ALBERT

Description: Modeling of fluid flow in naturally fractured reservoirs is often done through modeling and upscaling of discrete fracture networks (DFNs). The two-dimensional fracture geometry required for DFNs is obtained from subsurface and outcropping analog data. However, these data provide little information on subsurface fracture aperture, which is essential for quantifying porosity and permeability. Apertures are difficult to obtain from either outcropping or subsurface data and are therefore often based on fracture size or scaling relationships, but these do not consider the orientation and spatial distribution of fractures with respect to the in situ stress field. Using finite-element simulations, mechanical aperture can be modeled explicitly, but because changes in fracture geometry require renewed meshing and simulating, this approach is not easily integrated into subsurface DFN modeling workflows. We present a geometrically based method for calculating the shear-induced hydraulic aperture, that is, an aperture of up to 0.5 mm (0.02 in.) that can result from shear displacement along irregular fracture walls. The geometrically based method does not require numerical simulations, but it can instead be directly applied to DFNs using the fracture orientation and spacing distributions in combination with an estimate of the regional stress tensor and orientation. The frequency distribution of hydraulic aperture from the geometrically based method is compared with finite-element models constructed from five real fracture networks, digitized from outcropping pavements. These networks cover a wide range of possible geometries and spatial distributions. The geometrically based method predicts the average hydraulic aperture and equivalent permeability of fractured porous media with error margins of less than 5%.

Description: Stratigraphy provides insights into the evolution and dynamics of the Earth System over its long history. With recent developments in Earth System science, changes in Earth System dynamics can now be observed directly and projected into the near future. An integration of the two approaches provides powerful insights into the nature and significance of contemporary changes to Earth. From both perspectives, the Earth has been pushed out of the Holocene Epoch by human activities, with the mid-20 th century a strong candidate for the start date of the Anthropocene, the proposed new epoch in Earth history. Here we explore two contrasting scenarios for the future of the Anthropocene, recognizing that the Earth System has already undergone a substantial transition away from the Holocene state. A rapid shift of societies towards the UN Sustainable Development Goals could stabilize the Earth System in a state with more intense interglacial conditions than in the late Quaternary climate regime and with little further biospheric change. In contrast, a continuation of the present Anthropocene trajectory of growing human pressures will likely lead to biotic impoverishment and a much warmer climate with a significant loss of polar ice.

Description: Numerical geochemical modeling was used to study the effects on pore-water composition and mineralogy from carbon dioxide (CO 2 ) injection into the Pennsylvanian Morrow B Sandstone in the Farnsworth Unit in northern Texas to evaluate its potential for long-term CO 2 sequestration. Speciation modeling showed the present Morrow B formation water to be supersaturated with respect to an assemblage of zeolite, clay, carbonate, mica, and aluminum hydroxide minerals and quartz. The principal accessory minerals in the Morrow B, feldspars and chlorite, were predicted to dissolve. A reaction-path model in which CO 2 was progressively added up to its solubility limit into the Morrow B formation water showed a decrease in pH from its initial value of 7 to approximately 4.1 to 4.2, accompanied by the precipitation of small amounts of quartz, diaspore, and witherite. As the resultant CO 2 -charged fluid reacted with more of the Morrow B mineral matrix, the model predicted a rise in pH, reaching a maximum of 5.1 to 5.2 at a water–rock ratio of 10:1. At a higher water–rock ratio of 100:1, the pH rose to only 4.6 to 4.7. Diaspore, quartz, and nontronite precipitated consistently regardless of the water–rock ratio, but the carbonate minerals siderite, witherite, dolomite, and calcite precipitated at higher pH values only. As a result, CO 2 sequestration by mineral trapping was predicted to be important only at low water–rock ratios, accounting for a maximum of 2% of the added CO 2 at the lowest water–rock ratio investigated of 10:1, which corresponds to a small porosity increase of approximately 0.14% to 0.15%.

Description: Substrate relief is a common characteristic of hard-bottom offshore banks and is associated with benthic biodiversity. Earlier studies revealed varying relief associated with offshore mesophotic communities. Correlations may exist between relief and benthic biodiversity, which in turn may be useful in determining drill sites. Such drill site determination requires obtaining an estimate of variability in relief on these banks and its associated geographic patterns. We performed fine-scale surveys of relief on 14 banks in the Gulf of Mexico to examine variation between them, geographic patterns, and possible processes influencing them: 28 Fathom, 29 Fathom, Alderdice, Bouma, Bright, Elvers, Geyer, Horseshoe, McGrail, Parker, Rankin, Rezak, Sidner, and Sonnier Banks. We used a multibeam sensor on a remotely operated vehicle, with resolution of approximately 0.5 m (2 ft). Average and standard deviation of relief were calculated at the transect, drop site, and bank levels of resolution. Sidner and McGrail Banks had the highest relief, and 29 Fathom and Sonnier had the lowest. Sidner Bank had relief averaging up to 11 m (36 ft) in height, whereas 29 Fathom Bank exhibited the lowest relief (range 1 to 2 m [3 to 7 ft]). Bright Bank and all others exhibited intermediate and variable relief at both the transect and drop site levels. Relief is not predictable on many banks because of high variability between drop sites. Some low-relief banks are predictable in their relief, lending themselves to predictions of benthic diversity and suitable drill sites. Relief decreased significantly as one moved northward in the study region. Relief exhibited a significant sinusoidal pattern from west to east. Banks with low relief occurred off Lake Calcasieu and Lafayette, Louisiana.

Description: We determine the contribution of glacial isostatic adjustment (GIA) to future relative sea level change for the North American coastline between Newfoundland and Texas. We infer GIA model parameters using recently compiled and quality assessed databases of past sea-level changes, including new databases for the United States Gulf coast and Atlantic Canada. At 13 cities along this coastline, we estimate the GIA contribution to range from a few centimeters (e.g. 3[−1 − 9]cm, Miami) to a few decimeters (e.g. 18[12 − 22]cm, Halifax) for the period 2085-2100 relative to 2006-2015 (1- σ ranges given). We provide estimates of uncertainty in the GIA component using two different methods; the more conservative approach produces total ranges (1- σ confidence) that vary from 3to16cm for the cities considered. Contributions from ocean steric and dynamic changes as well as those from changes in land ice are also estimated to provide context for the GIA projections. When summing the contributions from all three processes at the 13 cities considered along this coastline, using median or best-estimate values, the GIA signal comprises ≈ 5 − 38 % of the total depending on the adopted climate forcing and location. The contributions from ocean dynamic/steric changes and ice mass loss are similar in amplitude but with spatial variation that approximately cancels, resulting in GIA dominating the net spatial variability north of 35 ∘ N).

Description: The literature on the costs of climate change often draws a link between climatic ‘tipping points’ and large economic shocks, frequently called ‘catastrophes’. The phrase ‘tipping points’ in this context can be misleading. In popular and social scientific discourse, ‘tipping points’ involve abrupt state changes. For some climatic ‘tipping points,’ the commitment to a state change may occur abruptly, but the change itself may be rate-limited and take centuries or longer to realize. Additionally, the connection between climatic ‘tipping points’ and economic losses is tenuous, though emerging empirical and process-model-based tools provide pathways for investigating it. We propose terminology to clarify the distinction between ‘tipping points’ in the popular sense, the critical thresholds exhibited by climatic and social ‘tipping elements,’ and ‘economic shocks’. The last may be associated with tipping elements, gradual climate change, or non-climatic triggers. We illustrate our proposed distinctions by surveying the literature on climatic tipping elements, climatically sensitive social tipping elements, and climate-economic shocks, and we propose a research agenda to advance the integrated assessment of all three.

Description: The Lower Cretaceous presalt section in the Kwanza Basin contains an excellent petroleum system that includes "synrift" strata (Barremian) overlain by a "sag" interval (Aptian) and capped by the Loeme Salt. The upper synrift is generally limestone with widespread mollusk packstones and grainstones (coquinas) deposited in a fresh-to–moderately saline (alkaline) lake. The sag interval is characterized by carbonate platforms and silica-rich isolated buildups formed in highly evaporated, highly alkaline lakes. Shrubby (dendritic), microbially influenced boundstones and intraclast–spherulite grainstones accumulated in shallow water on platform tops. Microbial cherts were deposited as organic buildups on large, isolated structural highs basinward (west) of platforms, and they apparently formed at low temperatures in very alkaline lake water. Shrubby boundstones and microbial cherts have vuggy pores that are primary and result in high permeability. Wackestones and packstones with calcitic grains (mainly spherulites) in dolomite or argillaceous dolomite were deposited in slightly deeper, low-energy sag environments. In addition, clays (especially stevensite) precipitated out of the silica-rich, highly alkaline lake waters. During sag deposition, calcite precipitated on the shallow lake floor with morphologies that ranged from spherulites to shrubs and included a continuum of intermediate forms. Spherulites probably precipitated just below the sediment–water interface. Spherulites and shrubby calcites are commonly recrystallized. Spherulites floating in stevensite probably formed in deeper lacustrine environments. Organic-rich mudstones were deposited in even deeper lacustrine environments in synrift and sag intervals, and they are likely the source of most hydrocarbons in this system. These interpretations are supported by seismic, core, petrographic, and stable isotope data.

Description: The United States Embassy in Beijing, China, released publicly a record of mass concentrations of particulate matter 2.5 µm and smaller in aerodynamic diameter (PM 2 .5 ) from April 2008 to the present measured with a Beta Attenuation Monitor (BAM). We compare these measurements with observations of particulate matter recorded at the Beijing Institute of Atmospheric Physics and observations of visibility recorded at the Beijing Capital International Airport (BCIA) to assess their value as a record of air quality in the greater Beijing metropolitan area. We find that the PM 2 .5 observations correlate well with the other observations of PM over the period January 1 st to February 1 st 2013 using a Tapered Element Oscillating Microbalance and an Aerosol Mass Spectrometer (AMS), and they exhibit a clear inverse correlation with visibility measured at BCIA. Using inverse visibility as a proxy of radiation extinction, we determine a dry mass extinction efficiency and a dependence of radiation extinction to relative humidity that is consistent with other studies of polluted urban environments. We deduce a strong degree of homogeneity of particulate pollution across the Beijing metropolitan region and conclude that the U.S. Embassy measurements are a reliable sample of this particulate pollution during periods of photochemical smog. The U.S. Embassy observations of PM 2 .5 appear to remain consistent throughout the available record and can serve as a useful dataset for studying future trends in particulate matter as China implements ambitious measures to improve air quality in the region.

Description: Climate change damages agriculture, causing deteriorating food security and increased malnutrition. Many studies have examined the role of distinct physical processes, but impacts have not been previously attributed to individual pollutants. Using a simple model incorporating process-level results from detailed models, here I show that although carbon dioxide (CO 2 ) is the largest driver of climate change, other drivers dominate agricultural yield changes. I calculate that anthropogenic emissions to date have decreased global agricultural yields by 9.5 ± 3.0%, with roughly 93% stemming from non-CO 2 emissions, including methane (-5.2 ± 1.7%) and halocarbons (-1.4 ± 0.4%). The differing impacts stem from atmospheric composition responses: CO 2 fertilizes crops, offsetting much of the loss induced by warming; halocarbons do not fertilize; methane leads to minimal fertilization but increases surface ozone which augments warming-induced losses. By the end of the century, strong CO 2 mitigation improves agricultural yields by ~3 ± 5%. In contrast, strong methane and hydrofluorocarbon mitigation improve yields by ~16 ± 5% and ~5 ± 4%, respectively. These are the first quantitative analyses to include climate, CO 2 and ozone simultaneously, and hence additional studies would be valuable. Nonetheless, as policy makers have leverage over pollutant emissions rather than isolated processes, the perspective presented here may be more useful for decision making than that in the prior work upon which this study builds. The results suggest that policies should target a broad portfolio of pollutant emissions in order to optimize mitigation of societal damages.

Description: The natural fracture system developed in the Cardium sandstone is examined in four outcropping structures that represent different stages of fold development. At the incipient stage of folding, the fracture system is dominated by large, widely spaced hybrid fractures that have very small displacements and are aligned in the regional shortening direction (type I orientation). These fractures are naturally propped open by asperities along the fracture surfaces. A lesser number of small thrust faults (type III orientation) are also developed. Extension fractures aligned parallel to the fold axis (type II orientation) begin to develop in the early stage of folding. Through the intermediate stage of folding, there is a progressive increase in the intensity of both type I and type II orientation fractures. Incremental increases in shear displacement on new or reactivated fractures create a gouge of comminuted sandstone grains along the fracture interface. As folding progresses to an advanced stage, there is major increase in the amount of shear displacement on both type I and type II orientation fractures. Many existing fractures coalesce into connected fracture zones and small faults that have shear offsets ranging from several centimeters to several meters. A breccia can result from intense fracturing in the rock within and marginal to these shear features. Slickensides on type I orientation features consistently indicate slip in a subhorizontal direction, even as bed dip increases. Multiple slickenside patterns record reactivation of these features. Type II orientation fractures and small faults consistently undergo bed-perpendicular slip. Type I and type II features both serve to stretch the Cardium sandstone beds but in different directions. Only type III features, which are a minor component of the fracture population, result in bed thickening.

Description: ABSTRACT Predictions of coastal evolution driven by episodic and persistent processes associated with storms and relative sea-level rise (SLR) are required to test our understanding, evaluate our predictive capability, and to provide guidance for coastal management decisions. Previous work demonstrated that the spatial variability of long-term shoreline change can be predicted using observed SLR rates, tide range, wave height, coastal slope, and a characterization of the geomorphic setting. The shoreline is not sufficient to indicate which processes are important to causing shoreline change, such as overwash that depends on coastal dune elevations. Predicting dune height is intrinsically important to assessing future storm vulnerability. Here, we enhance shoreline-change predictions by including dune height as a variable in a statistical modeling approach. Dune height can also be used as an input variable, but it does not improve the shoreline-change prediction skill. Dune-height input does help to reduce prediction uncertainty. That is, by including dune height, the prediction is more precise but not more accurate. Comparing hindcast evaluations, better predictive skill was found when predicting dune height (0.8) compared to shoreline change (0.6). The skill depends on the level of detail of the model and we identify an optimized model that has high skill and minimal overfitting. The predictive model can be implemented with a range of forecast scenarios, and we illustrate the impacts of a higher future sea-level. This scenario shows that the shoreline change becomes increasingly erosional and more uncertain. Predicted dune heights are lower and the dune height uncertainty decreases.

Description: The response of runoff and sediment loading in the Apalachicola River under projected climate change scenarios and land use land cover (LULC) change is evaluated. A hydrologic model using the Soil Water Assessment Tool (SWAT) was developed for the Apalachicola region to simulate daily runoff and sediment load under present (circa 2000) and future conditions (2100) to understand how parameters respond over a seasonal time frame to changes in climate, LULC, and coupled climate / LULC. The Long Ashton Research Station-Weather Generator (LARS-WG) was used to downscale temperature and precipitation from three general circulation models (GCM), each under Intergovernmental Panel on Climate Change (IPCC) carbon emission scenarios A2, A1B, and B1. Projected 2100 LULC data provided by the United States Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center was incorporated for each corresponding IPCC scenario. Results indicate climate change may induce seasonal shifts to both runoff and sediment loading. Changes in LULC showed more sediment load was associated with increased agriculture and urban areas and decreased forested regions. A nonlinear response for both runoff and sediment loading was observed by coupling climate and LULC change, suggesting both should be incorporated into hydrologic models when studying future conditions. The outcomes from this research can be used to better guide management practices and mitigation strategies.

Description: This work outlines a dynamic modeling framework to examine the effects of global climate change, and sea level rise (SLR) in particular, on tropical cyclone-driven storm surge inundation. The methodology, applied across the northern Gulf of Mexico, adapts a present day large-domain, high resolution, tide, wind-wave, and hurricane storm surge model to characterize the potential outlook of the coastal landscape under four SLR scenarios for the year 2100. The modifications include shoreline and barrier island morphology, marsh migration, and land use land cover change. Hydrodynamics of ten historic hurricanes were simulated through each of the five model configurations (present day and four SLR scenarios). Under SLR, the total inundated land area increased by 87% and developed and agricultural lands by 138% and 189%, respectively. Peak surge increased by as much as 1 m above the applied SLR in some areas, and other regions were subject to a reduction in peak surge, with respect to the applied SLR, indicating a nonlinear response. Analysis of time-series water surface elevation suggests the interaction between SLR and storm surge is nonlinear in time; SLR increased the time of inundation and caused an earlier arrival of the peak surge, which cannot be addressed using a static (“bathtub”) modeling framework. This work supports the paradigm shift to using a dynamic modeling framework to examine the effects of global climate change on coastal inundation. The outcomes have broad implications and ultimately support a better holistic understanding of the coastal system and aid restoration and long-term coastal sustainability.

Description: This study examines the integrated influence of sea level rise (SLR) and future morphology on tidal hydrodynamics along the Northern Gulf of Mexico (NGOM) coast including seven embayments and three ecologically and economically significant estuaries. A large-domain hydrodynamic model was used to simulate astronomic tides for present and future conditions (circa 2050 and 2100). Future conditions were simulated by imposing four SLR scenarios to alter hydrodynamic boundary conditions and updating shoreline position and dune heights using a probabilistic model that is coupled to SLR. Under the highest SLR scenario, tidal amplitudes within the bays increased as much as 67% (10.0 cm) due to increases in the inlet-cross-sectional area. Changes in harmonic constituent phases indicated tidal propagation was faster in the future scenarios within most of the bays. Maximum tidal velocities increased in all of the bays, especially in Grand Bay where velocities doubled under the highest SLR scenario. In addition, the ratio of the maximum flood to maximum ebb velocity decreased in the future scenarios (i.e., currents became more ebb dominant) by as much as 26% and 39% in Weeks Bay and Apalachicola, respectively. In Grand Bay, the flood-ebb ratio increased (i.e., currents became more flood dominant) by 25% under the lower SLR scenarios, but decreased by 16% under the higher SLR as a result of the offshore barrier islands being overtopped, which altered the tidal prism. Results from this study can inform future storm surge and ecological assessments of SLR, and improve monitoring and management decisions within the NGOM.

Description: This paper analyzes multi-year records of solar flux and climate data from two solar power sites in Vermont. We show the interannual differences of temperature, wind, panel solar flux, electrical power production and cloud cover. Power production has a linear relation to a dimensionless measure of the transmission of sunlight through the cloud field. The difference between panel and air temperatures reaches 24°C with high solar flux and low windspeed. High panel temperatures that occur in summer with low windspeeds and clear skies can reduce power production by as much as 13%. The intercomparison of two sites 63 km apart shows that while temperature is highly correlated on daily (R 2 =0.98) and hourly (R 2 =0.94) timescales, the correlation of panel solar flux drops markedly from daily (R 2 =0.86) to hourly (R 2 =0.63) timescales. Minimum temperatures change little with cloud cover, but the diurnal temperature range shows a nearly linear increase with falling cloud cover to 16°C under nearly clear skies, similar to results from the Canadian Prairies. The availability of these new solar and climate datasets allows local student groups, here a Rutland High School team, to explore the coupled relationships between climate, clouds and renewable power production. As our society makes major changes in our energy infrastructure in response to climate change, it is important that we accelerate the technical education of high school students using real-world data. Citation: Betts, A.K., J. Hamilton, S. Ligon and A.M. Mahar (2015), Integrating solar energy and climate research into science education. Submitted to Earth's Future, 2015EF000315.

Description: CONFLICT OF INTEREST AND OTHER RELEVANT INFORMATION: Conflict of interest information is provided below for the authors of this paper. Chesapeake Energy Corporation (Chesapeake) funded the authors of this paper through their organizations of employment and, in the case of the senior author, privately, to do basic research to evaluate this very large data set and prepare the paper. Data were collected on behalf of Chesapeake by paid third-party consultants to comply with regulatory programs. The analyses and interpretations, and report writing, were done by the authors of the paper. The decision to submit the paper was that of the authors. The opinions and conclusions expressed in this paper are those of the authors and do not necessarily reflect those of Chesapeake. During the preparation of this paper, all authors worked for the organizations noted in authorship. Mark Hollingsworth is a current employee of Chesapeake, having worked there from February 2011 to the present. Prior to Mr. Hollingsworth’s employment by Chesapeake, he worked for TestAmerica Laboratories, Inc., which provided laboratory analytical consulting services to Chesapeake. Bert Smith is a former employee of Chesapeake, having worked there from May 2012 to September 2013, and has been employed by Enviro Clean Cardinal from November 2013 to the present. Enviro Clean Cardinal also does consulting work for Chesapeake. Prior to May 2013, Mr. Smith worked for Science Applications International Corporation, which did consulting work for Chesapeake. Elizabeth Perry works for AECOM, who provides energy consulting services to government and private industry, including Chesapeake. Rikka Bothun also worked for AECOM during most of the time this paper was under preparation but left AECOM in December 2014 and now works for a private consulting company that does not do consulting work for Chesapeake. None of the following authors (Don Siegel, Bert Smith, Elizabeth Perry, or Rikka Bothun) have competing corporate financial interests exceeding guidelines presented by AAPG Environmental Geosciences Journal. Mark Hollingsworth is a current employee of Chesapeake and owns stock in the company in an amount in excess of $5000. Donald Siegel is the lead author and contributor to the manuscript’s preparation, technical interpretations, and review of these data and the manuscript. Bert Smith contributed to the manuscript preparation, technical interpretations, and review of these data and the manuscript. Elizabeth Perry and Rikka Bothun contributed to the manuscript preparation, technical interpretations, and review. Mark Hollingsworth maintains the Chesapeake baseline data set and contributed to the manuscript preparation and review of these data and the manuscript. Due to confidentiality agreements with landowners whose wells were sampled, latitude and longitude cannot be shown on maps.

Description: CONFLICT OF INTEREST AND OTHER RELEVANT INFORMATION: Chesapeake Energy Corporation funded consultants and the authors of this paper through their organizations of employment and, in the case of Donald Siegel, privately to do basic research on this temporal data set and prepare the paper. The authors of this report did all analysis and writing. The opinions and conclusions expressed in this paper are those of the authors and do not necessarily reflect those of Chesapeake Energy Corporation. During the preparation of this paper, all authors worked for the organizations noted in authorship. Bert Smith is a former employee of Chesapeake Energy Corporation, having worked there from May 2012 to September 2013, and has been employed by Enviro Clean Cardinal since November 2013. While employed at Chesapeake Energy Corporation, he managed this temporal study, which was completed shortly after he left Chesapeake Energy Corporation. Enviro Clean Cardinal also does consulting work for Chesapeake Energy Corporation. Prior to May 2012, Bert Smith worked for Science Applications International Corporation, which consulted for Chesapeake Energy Corporation. Mark Becker has worked for Chesapeake Energy Corporation since March 2012; prior to that, he worked for the US Geological Survey for 24 yr. Donald Siegel works for Syracuse University, but he was funded privately for this work. Neither Bert Smith nor Donald Siegel have competing corporate financial interests exceeding guidelines presented by AAPG Environmental Geosciences . Mark Becker is a current employee of Chesapeake Energy Corporation and owns stock in the company in an amount in excess of $5000. Bert Smith is the lead author and contributed to the paper preparation, technical interpretations, and review of these data and paper. Mark Becker contributed to the paper preparation, technical interpretations, and review of these data and paper. Donald Siegel contributed to the paper preparation, technical interpretations, and review of these data and paper.

Description: As the largest active strike-slip fault zone of east Asia, the Tan-Lu fault zone is the most significant tectonic feature controlling the hydrocarbon accumulation in Bohai Bay. The Penglai 19-3 and Penglai 25-6 fields are the most typical examples among the fields found in the Tan-Lu fault zone. The structures related to the two fields are fault restraining bends produced by dextral strike-slip movement on faults within the Tan-Lu fault zone. The structures initiated at the late depositional stage of the third member of the Eocene Shahejie Formation (ca. 40 Ma) after the deposition of the main source rocks of the basin. They then experienced a main development stage during deposition of the second and first members of the Eocene Shahejie Formation and the Oligocene Dongying Formation (40–25 Ma). During the Neogene, the structures continued to be enhanced slightly because of continued strike-slip until the early to middle Pleistocene. These structures were characterized by the absence of the preponderance of the reverse separations on faults and might represent the restraining bends in a divergent wrench deformation zone. This study shows that restraining bend structures along intrabasinal strike-slip systems formed after the deposition of the source rocks are very favorable for hydrocarbon accumulation.

Description: The distribution of porosity was examined on seven drill cores from west–central Alberta encompassing the Belle Fourche and Second White Specks Formations. These Cenomanian–Turonian mudrocks from the Western Canada Sedimentary Basin exhibit good organic richness (〉2 wt. % total organic carbon) and marine kerogen type II with limited kerogen type III. With the increasing thermal maturity from approximately 0.43% vitrinite reflectance ( R o ) to approximately 0.90% R o , the total porosity decreases from approximately 9 to approximately 1 vol. %. This change translates to a reduction in total pore volume from approximately 0.05 to approximately 0.005 cm 3 /g and is accompanied by changes in relative proportions of micropore, mesopore, and macropore volumes. Variations in total porosity for the seven cores with different thermal maturities across Alberta are mainly related to mesoporosity and macroporosity, although the in-core variations in total porosity are mainly related to microporosity. In general, organic matter micropores contribute to the overall microporosity in the seven cores across the study area. The increase in the total pore volumes is in accordance with an increasing concentration of quartz, although increasing concentrations of chlorite and kaolinite may contribute to greater abundance of micropores in the seven cores. The in-core variations suggest that greater contents of kaolinite and illite may contribute to increasing mesopore volumes. Variations in pore volumes and pore size distribution with depth within individual cores (representing specific thermal maturity level) differ from what is observed laterally, when cores of various thermal maturity levels across Alberta are compared, indicating complex controls on porosity systems.

Description: The stratigraphic organization of early synrift clastic successions is controlled by the rates of tectonic subsidence and the growth of the master faults, which, coupled with eustatic base level change, control the generation of accommodation. The 100- to 300-m (328- to 984.2-ft)-thick, highly heterolithic Lower Jurassic upper Åre and Tilje succession (Halten terrace, offshore Norway) represents an example of ancient synrift deposits that accumulated within a north–northeast-south–southwest-oriented structurally controlled embayment where sedimentation was strongly influenced by tidal currents but with significant river influence and minor wave action, except in exposed distal locations. The shallowing-upward, deltaic Tilje succession was deposited near the lowstand shoreline. The Tilje Formation consists of two tabular second-order sequences, each of which overlies structurally influenced sequence boundaries (SB2 and SB3 in local terminology) associated with rift-related tectonic pulses. The first pulse led to formation of SB2 (shallow incision into the Åre Formation) and caused a regional geomorphological change of the basin from an open, wave-dominated setting (upper Åre Formation) to a funnel-shaped, tide-dominated setting (Tilje Formation), in which the lower sequence 2 accumulated. Sequence 3 rests erosively on sequence 2 and is characterized by proximal tidal deposits showing at least two main oblique to axial fluvial input points (north–northwest and northeast), with an increase in wave influence and deepening toward the south. Local rapid subsidence of elongated, narrow hanging wall basins exerted a subtle control on the succession thickness and distribution of tidal–fluvial distributary channels. The overall tabular geometry and internal architecture of the Tilje Formation is less complex than that of other tidal successions worldwide, showing lateral and vertical compartmentalization of the best tidal–fluvial sandstone reservoirs.

Description: Carbonate reservoir rocks exhibit a great variability in texture that directly impacts petrophysical parameters. Many exhibit bi- and multimodal pore networks, with pores ranging from less than 1 μm to several millimeters in diameter. Furthermore, many pore systems are too large to be captured by routine core analysis, and well logs average total porosity over different volumes. Consequently, prediction of carbonate properties from seismic data and log interpretation is still a challenge. In particular, amplitude versus offset classification systems developed for clastic rocks, which are dominated by connected, intergranular, unimodal pore networks, are not applicable to carbonate rocks. Pore geometrical parameters derived from digital image analysis (DIA) of thin sections were recently used to improve the coefficient of determination of velocity and permeability versus porosity. Although this substantially improved the coefficient of determination, no spatial information of the pore space was considered, because DIA parameters were obtained from two-dimensional analyses. Here, we propose a methodology to link local and global pore-space parameters, obtained from three-dimensional (3-D) images, to experimental physical properties of carbonate rocks to improve P-wave velocity and permeability predictions. Results show that applying a combination of porosity, microporosity, and 3-D geometrical parameters to P-wave velocity significantly improves the adjusted coefficient of determination from 0.490 to 0.962. A substantial improvement is also observed in permeability prediction (from 0.668 to 0.948). Both results can be interpreted to reflect a pore geometrical control and pore size control on P-wave velocity and permeability.

Description: With the booming exploration and development of unconventional hydrocarbon resources in source rocks, the estimation of total organic carbon (TOC) content from well logs has become increasingly important because of the significance of TOC in the formation evaluation of those resources. In this paper, a new log overlay method is developed to estimate the TOC content of source rocks with excess radioactivity, but containing little or no potassium feldspar. Specifically, on the basis of previous results of log responses of source rocks, it is believed that the natural gamma ray (GR) log responses of source rocks in the applicable conditions are predominantly contributed by clay minerals and organic matter. A practical clay indicator is established to reflect the clay content using density and neutron logs. The indicator is effective not only in nonsource rocks that contain oil or water but also in source rocks. Furthermore, a new method was developed by overlaying the properly scaled clay indicator curve on the GR curve. In nonsource rocks, including clay-rich rocks and reservoirs saturated with oil or water, the two curves overlie each other, whereas a separation between the curves occurs in organic-rich source rocks. The separation between the curves was defined and expressed and can be used to calculate the TOC consecutively after careful calibration with core data. This method has been successfully applied to two shale gas plays with high-maturity kerogen in the Sichuan Basin, China. In addition, a source rock with low-maturity kerogen was used to verify the new method for its effectiveness, reliability, and widespread adaptability.

Description: Geochemical fingerprinting of produced water from hydraulic fracturing projects is an essential tool to trace their provenance during the postfracturing period, to quantify recovery rates and volumes of fracturing fluids, and to visualize the geodynamic structure of natural or induced fracture networks. A total of 41 produced water samples from an exploration well in the Northern Arabia Exploration Area in Saudi Arabia were collected daily from the fracture-stimulated Qusaiba hot shale and analyzed for major ions and trace elements and partially for environmental isotopes. The postfracturing period shows an initial return of supply water and potassium chloride brine, subsequently replaced by the inflow of sodium chloride–type formation water with a stable plateau salinity of 50,000 mg/L. Less than 10% of the total injected fracturing fluids were recovered during postfracturing, whereas 78.8 vol. % of the total recovered fluid is composed of formation water (20,843 out of 26,446 bbls) during the study period. Coinciding values between logged reservoir temperature and calculated geothermometers confirm the provenance of pore water from the Qusaiba hot shale or from nearby units. The recharge of the Silurian sequence with meteoric surface water occurred during the early Holocene (6–6.7 ka), as evidenced by geochronological dating with the 14 C method and 18 O/ 2 H values close to the global meteoric water line. The inflow of formation water into the stimulated shale layer in the postfracturing stage could be originated by the natural occurrence of pore water within a naturally fractured, black shale layer or, more likely, by the rise of groundwater from the underlying Sarah sandstones via migration pathways of natural or newly formed, vertically induced hydraulic fractures. For this particular well site and the specific hydraulic fracturing project, chemical and isotopic fingerprinting confirms the absence of ascending migration pathways from the Silurian Qusaiba hot shale toward a shallower groundwater system, which are isolated through a lithological set of more than 900 m (3000 ft) of impermeable mudstone from the Qusaiba Member.

Description: Oxygen isotope ( 18 O) zonation in carbonate mineral cements is often employed as a proxy record (typically with millimeter-scale resolution) of changing temperature regimes during different stages of sediment diagenesis. Recent advances in secondary ion mass spectrometry allow for highly precise and accurate determinations of cement 18 O values to be made in situ on a micrometer scale, thus significantly increasing the spatial resolution available to studies of diagenesis in sandstone–shale and carbonate systems. Chemo-isotopically zoned dolomite–ankerite cements within shaly sandstone beds of the predominantly silty–shaly Eau Claire Formation (Cambrian, Illinois Basin) were investigated, revealing the following: with increasing depth of burial (from 〈0.5 to ~2 km [〈1500 to 6500 ft]), cement 18 O values decrease from a high of approximately 24 down to approximately 14 (on the Vienna standard mean ocean water [VSMOW] scale, equivalent to –6.5 to –16.5 on the Vienna Peedee belemnite [VPDB] scale). The observed cross-basin trend is largely consistent with cements having formed in response to progressive sediment burial and heating. Within the context of independent burial and thermal history models for the Illinois Basin, cementation began soon after deposition and continued intermittently into the mid-Permian. However, temperatures in excess of burial model predictions are inferred at the time of latest ankerite cement precipitation, which we propose overlapped in time with conductive heating of the Eau Claire Formation (a closed system) from under- and overlying sandstone aquifers that channeled the flow of hot, Mississippi Valley–type mineralizing brines during the mid-Permian (ca. 270 Ma).

Description: The Bohai Sea area, offshore of the Bohai Bay Basin, is one of the most petroliferous regions in China, with proven original oil in place of approximately 2.4 x 10 9 m 3 (150.94 x 10 8 bbl) and proven original gas in place of over 5 x 10 12 m 3 (1.76 x 10 13 ft 3 ). Cumulative oil production is over 50 million tons (3.5 x 10 8 bbl). In this study, using the limited data on source rock thickness, core samples, and Rock-Eval pyrolysis along with sedimentary facies analysis, source rock characteristics of different depositional settings were identified, and the thickness, richness, organic matter type, and thermal evolution of four sets of source rocks in the Bohai Sea area— the second member of Dongying Formation (E 3 d 2 ), the third member of Dongying Formation (E 3 d 3 ), the first and second members of Shahejie Formation (E 2 s 1-2 ), and the third member of Shahejie Formation (E 2 s 3 )—were predicted and evaluated. Subsequently, the intensity and history of hydrocarbon expulsion for different sags was systematically compared and analyzed. The greatest thickness of the four sets of source rocks in the Bohai Sea area is 400–800 m (1300–2600 ft). The average richness of the organic matter of these source rocks is 1.74%–2.87%. The E 2 s 3 set has the highest organic matter abundance; E 2 s 1-2 has the lowest. The organic matter of these source rocks is mainly type I and type II, but their evolutions differ. The vitrinite reflectance of E 3 d 2 is 0.5%–1.0%, that of E 3 d 3 is 0.7%–1.25%, that of E 2 s 1-2 is 0.75%–1.75%, and that of E 2 s 3 is 0.75%–2.0%. The cumulative hydrocarbon expulsion of the four sets of rocks is 4.14 x 10 10 t (2.90 x 10 11 bbl). The E 2 s 1-2 set has the greatest expulsion amount: 1.75 x 10 10 t (1.22 x 10 11 bbl). The peak stages of hydrocarbon expulsion of the four sets of source rocks were during Neogene Minghuazhen Formation (12.2–2.0 Ma) and Neogene Guantao Formation (16.6–12.0 Ma). The Bozhong sag expelled the most hydrocarbons, followed by the Liaozhong, Qikou, and Huanghekou sags.

Description: Schlumberger’s modular dynamics tester (MDT) tool was used to test 10 Miocene sands in the Tubular Bells deep water oil field, offshore Gulf of Mexico, United States. Nine sands from true vertical depths of 19,999–26,464 ft (6096–8066 m) were sampled from a single well and another deeper sand (29,075 ft [8,862 m]) from a second well. Using ion and strontium, oxygen, and hydrogen isotopic analysis, the nine MDT water samples were demonstrated to be mostly formation water. The sample in the second well from 29,075 ft (8862 m) is filtrate, based on its oxygen and hydrogen isotopic composition (–4.10 and –26.3, standard mean ocean water [SMOW]). Insufficient water was recovered for ionic analysis, which made the isotopic analysis even more important to help document the origin of the water in what appears to be a hydrocarbon-charged interval. Using a combination of chemical and isotopic analyses, it is concluded that only two of the sands are possibly in fluid communication or separated by baffles. The other sands are each in separate fluid compartments. The salinity (total dissolved solids) of the formation waters decreases with depth and distance from the salt and ranges from approximately 39,000 to more than 288,000 mg/L. The formation waters have oxygen and hydrogen isotopic compositions ranging from +3.19 to +4.52 and –16.1 to –19.4, respectively (SMOW). Bromide–chloride systematics indicate that the formation waters are mixtures of normal seawater and seawater that was evaporated to and probably beyond halite saturation. The evaporite water is sourced from the deeper Jurassic section (Louann Salt) and likely came up along the salt–sediment interface along faults and fractures associated with emplacement of the salt stock and canopy. The formation waters were subsequently enriched in chloride and sodium to varying degrees by dissolution of the diapiric salt. Strontium isotopes are compatible with mixing of highly concentrated (evaporative) Jurassic seawater with relatively low 87 Sr/ 86 Sr ratios and much less concentrated (almost seawater salinity) pore water with more radiogenic strontium, the latter derived from silicate reactions during burial diagenesis. Short-chain organic acids are present in high concentrations (〉1000 mg/L) along with the organophilic ions boron and iodide. The concentrations of boron, iodide, and organic acids do not correlate with salinity. Boron and iodide show a strong positive relationship with each other and a less strong, but positive, relationship with organic acid concentrations. Boron and iodide are nearly twice as concentrated in waters of oil-bearing sands than in water-bearing sands and appear to be indicators of hydrocarbon proximity. One water-bearing sand has concentrations of boron and iodide as high as those seen in oil-bearing sands, possibly suggesting an updip oil accumulation.

Description: Huge, high gas–oil ratio, hydrogen sulfide (H 2 S)-bearing gas condensate accumulations were recently discovered in the Ordovician carbonate reservoirs of the Tazhong uplift in the Tarim Basin, northwest China. Distinct differences exist between the eastern and western condensates in terms of chemical and isotopic compositions. Condensates from the western part of the uplift were characterized by high dibenzothiophenes (generally 〉500 μg/g), a high H 2 S concentration (~7%, vol./vol.), and relatively depleted 13 C methane ( 13 C 1 = –55.5 to –36). The H 2 S concentration in the Tazhong gas condensates shows a positive correlation to Mg 2+ concentration in the formation water. Formation water in Lower Ordovician–Cambrian strata in the Tazhong uplift is rich in Mg 2+ , which facilitates the thermochemical sulfate reduction (TSR) of sulfate contact ion pairs (CIPs) to produce H 2 S and dibenzothiophenes. A detailed comparison of the chemical compositions of the formation waters in different strata indicates that a high H 2 S concentration in the Tazhong gas condensates originates from the TSR of sulfate CIPs in the Lower Ordovician–Cambrian strata, where a primary oil accumulation may have existed. The concentrations of 3- and 4-methyldiamantanes in the western condensates (80 to 150 μg/g) are relatively lower than those from the eastern part of the uplift. Also, the 13 C 1 in the western H 2 S-bearing gas condensates was more negative, and the 13 C 2 – 13 C 1 value was larger than that from typical TSR-altered gases. These features indicate that the western Tazhong samples had just entered the initial stage of TSR. According to the pressure, volume, temperature (PVT) phase diagram, the lower Paleozoic section was quickly buried after the Tortonian. High-H 2 S hydrocarbon inclusions formed during the last 10 m.y. when paleotemperatures reached 140°C (284°F). Because the reaction rate of the sulfate CIPs oxidation was relatively slower than that of H 2 S autocatalysis during the entire TSR process, advanced TSR has not been accomplished yet. It is also inferred that the Tortonian was the key period for accumulation of secondary H 2 S-bearing gas condensates, resulting from abundant gas washing along deep fractures and charging in the early reservoirs. An increased aromaticity parameter (toluene/n-heptane) and an increased fractionation index from east to west indicate an intensified degree of gas washing. Different gas-washing intensities in the eastern and western gas condensates led to diverse PVT states as well. Deep strata in the Tazhong uplift were characterized by multiple charges and mixing, coupled with periodic TSR, leading to the occurrence of variable H 2 S-bearing gas condensates.

Description: Anomalous carbonate horizons with intercrystalline hydrocarbon residue, cone-in-cone structures, and calcite "beef" veins in adjacent sandstone beds record potential evidence for hydrocarbon generation and seepage in the middle to upper Turonian Frontier Formation from the Uinta Basin, Utah and Colorado. Eight carbonate occurrences, all encountered within distal delta-front facies (thin-bedded sandstones and siltstones), were sampled at outcrop locations from the southern and eastern margins of Dinosaur National Monument. Seven petrographic facies (PF1–PF7) were identified using standard petrographic and cathodoluminescence microscopy: PF1, large and small botryoids and fans; PF2, yellow-brown spherules; PF3, microcrystalline spar cement; PF4, blocky spar; PF5, prismatic spar; PF6, drusy mosaic spar; and PF7, dolomite. Facies PF1–PF3 are synsedimentary phases comprising a large percentage of carbonate horizon volume, whereas PF4–PF7 are late-stage fabrics. The 13 C values of PF1–PF3 (–9.9 to –20.0) are consistent with contributions from biogenic methane seepage during deposition and early diagenesis. Brecciated PF1 fabrics and blowout depressions within sandstone horizons further indicate significant methane generation during deposition and early burial. Late-stage fabrics contain 13 C (–8.0 to –17.3) and 18 O (–6.5 to –13.5) values consistent with progressive burial, during which intercrystalline hydrocarbon residue, cone-in-cone structures, and calcite beef veins were formed by the thermal maturation of organic matter from enclosing distal delta-front facies. Together, these features reveal the potential for the thin-bedded facies of the Frontier Formation distal delta front to serve as a potentially viable petroleum subsystem previously unrecognized in the Uinta–Piceance petroleum province.

Description: Historical extreme storm events are widely used to make Probable Maximum Precipitation (PMP) estimates, which form the cornerstone of large water management infrastructure safety. Past studies suggest that extreme precipitation processes can be sensitive to land surface feedback and the planetary warming trend, that make the future safety of large infrastructures questionable given projected changes in land cover and temperature in the coming decades. In this study, a numerical modeling framework was employed to reconstruct 10 extreme storms over CONUS that occurred during the past 100 years, which are used by the engineering profession for PMP estimation for large infrastructures such as dams. Results show that the correlation in daily rainfall for such reconstruction can range between 0.4 ~ 0.7, while the correlation for -3day accumulation (a standard period used in infrastructure design) is always above 0.5 for post-1948 storms. This suggests that current numerical modeling and reanalysis data allow us to reconstruct big storms after 1948s with acceptable accuracy. For storms prior to 1948, however, reconstruction of storms shows inconsistency with observations. Our study indicates that numerical modeling and data may not have advanced to a sufficient level to understand how such old storms (pre-1948) may behave in future warming and land cover conditions. However, the infrastructure community can certainly rely on the use of model reconstructed extreme storms of the 1948-present period to reassess safety of our large water infrastructures under assumed changes in temperature and land cover.

Description: The project presented here sought to determine whether changes in anthropogenic thermal emission can have a measurable effect on temperature at the national level, taking Japan & Great Britain as type examples. Using energy consumption as a proxy for thermal emission, strong correlations (mean r 2  = 0.90 & 0.89 respectively) are found between national equivalent heat output HO and temperature above background levels ∆ t averaged over 5 to 8 year periods between 1965 and 2013, as opposed to weaker correlations for CMIP5 model temperatures above background levels ∆ mt (mean r 2  = 0.52 & 0.10). It is clear that the fluctuations in ∆ t are better explained by energy consumption than by present climate models, and that energy consumption can contribute to climate change at the national level on these timescales.

Description: Cities generate 70% of anthropogenic greenhouse gas emissions, a fraction that is growing with global urbanization. While cities play an important role in climate change mitigation, there has been little focus on reducing urban methane emissions. Here we develop a conceptual framework for methane mitigation in cities by describing emission processes, the role of measurements, and a need for new institutional partnerships. Urban methane emissions are likely to grow with expanding use of natural gas and organic waste disposal systems in growing population centers; however, we currently lack the ability quantify this increase. We also lack systematic knowledge of the relative contribution of these distinct source sectors on emissions. We present new observations from 4 North American cities to demonstrate that methane emissions vary in magnitude and sector from city to city, and hence require different mitigation strategies. Detections of fugitive emissions from these systems suggest that current mitigation approaches are absent or ineffective. These findings illustrate that tackling urban methane emissions will require research efforts to identify mitigation targets, develop and implement new mitigation strategies, and monitor atmospheric methane levels to ensure the success of mitigation efforts. This research will require a variety of techniques to achieve these objectives, and should be deployed in cities globally. We suggest that metropolitan-scale partnerships may effectively coordinate systematic measurements and actions focused on emission reduction goals.

Description: Reliable modeling of meandering fluvial reservoirs is challenging because of the heterogeneity in magnitude and pattern of porosity and permeability related to depositional and diagenetic features. Early mechanical and chemical alterations proceed along different pathways directly related to depositionally governed differences in textural and compositional parameters. In a well-constrained sedimentological framework and with relatively homogeneous conditions of detrital composition, this study aims to determine the effect of depositional fabric on early diagenetic processes and their collective effect on petrophysical properties (pore size distribution, open porosity, and permeability). A high-resolution qualitative and quantitative petrographic analysis is conducted on 22 fine- to very fine–grained sandstones from the main meandering fluvial facies of the channel (center and margin), point bar (lower, middle, and upper), scroll bar, and chute channel of a Triassic outcrop analog. The occurrence of small-scale internal heterogeneity associated with detrital matrix and suspension-settling laminae favors the compaction process and hinders early pore-filling cement precipitation that helps the preservation of primary porosity. Multivariate statistical treatment of data demonstrates that large (〉1 µm) and well-connected primary intergranular pores are the main contributors to permeability in the more heterogeneous samples. The distribution of the finer-grained sediment fraction is strongly facies related as a result of hydraulic sorting. Better understanding of linkages between depositionally predictable features and diagenetically induced heterogeneity may lead to realistic reservoir models and enhanced effectiveness of exploitation and bypassed-oil recovery strategies.

Description: Fractures are the main fluid-flow pathways in tight-oil sandstones, and they have a significant influence on tight-oil distribution, exploration, and development. Cores and image logs are commonly unavailable because of their high costs, so employing conventional logs for fracture detection is imperative for tight-oil sandstones. We compared the fracture-response characteristics of conventional logs based on two data sets, one from 8 cored wells with fracture intensities greater than 1 m –1 (3.3 ft –1 ) and the other from 11 cored wells with fracture intensities less than 0.5 m –1 (1.6 ft –1 ), with a case study of the Upper Triassic Yanchang Formation in southwest Ordos Basin, China. The results indicate that when tight-oil sandstones are more intensely fractured, the caliper log, acoustic log, compensated neutron log, density log, dual induction logs, and laterolog 8 present fracture responses to some extent. However, it is difficult to make a distinction between fractured and nonfractured zones using conventional logs in sandstones with smaller fracture intensities. The fracture-response intensities of conventional logs are weak, and they are influenced by fracture abundance, fracture occurrence, fracture scale, and mineral-filling degree. Moreover, lithology, fluids, and rock physical properties can cause fracturelike responses. Hence, some ambiguity exists when using conventional logs to directly identify fractures. Accompanying fracture-sensitive conventional logs with some methods to enhance fracture-response intensity and eliminate nonfracture influence could enable fracture identification in tight-oil sandstones.

Description: Accurate definition of structural style in subsurface interpretation is critically important for understanding the deformation history of fold-and-thrust belts, as well as assessing the petroleum prospectivity of structural traps. Using two- and three-dimensional seismic reflection surveys, well data, field mapping, forward models, and balanced cross sections, we describe the structural styles across the actively deforming southern Junggar fold-and-thrust belt in northwestern China, a basin undergoing petroleum exploration and development operations. Subsurface interpretations indicate several folds in the basin overlie Jurassic normal faults that were tectonically inverted in the Late Jurassic to Early Cretaceous. Following inversion, multiple detachment levels propagated northward from the Tian Shan and formed a series of imbricated fault-related folds. The most prominent fold trend in southern Junggar consists of the Tugulu, Manas, and Huoerguosi anticlines, which trap hydrocarbons in clastic Eocene reservoirs. These structures exhibit complex internal geometries, with coeval forethrusts and backthrusts forming imbricated structural wedges. In the latest stages of deformation, and continuing at present, the uppermost thrust sheet, the Southern Junggar Thrust (SJT), truncated the backlimbs of these structural traps, implying the SJT is a tectonically active, out-of-sequence thrust. From these interpretations, we present a model for how the southern Junggar fold-and-thrust belt developed from Jurassic to present. Moreover, we detail how fold growth, fault activity, and structural style affected charge histories, trap formation, and reservoir compartmentalization. Our results have direct implications for assessment of the southern Junggar petroleum system as well as other complex fold-and-thrust belts.

Description: Distinguishing axial and lateral sedimentary systems in rift basins is crucial for predicting reservoir distribution and quality, particularly where synrift strata are interrupted by mass transport complexes (MTCs). Upper Jurassic deep-marine synrift successions in the central North Sea have been studied to assess the temporal and spatial relationships of sediments and controls on reservoir quality. In the Late Jurassic, the central graben experienced erosion at rift margins, whereas adjacent grabens were starved and underfilled with marine sediments, supplied by axial and transverse systems. This study focused on sediments adjacent to a major intrabasinal high, the Josephine ridge. Data included seismic, wireline logs from 16 wells, and biostratigraphic and sedimentological analysis of 144 m (472 ft) of core. Synrift strata are dominated by mudstones but include MTCs interbedded with coarse sandstones at the rift margin and fine-grained turbidite sandstones in basinal depocenters. Petrographic and heavy mineral data indicate different provenance between MTCs and basinal turbidites. Turbidites correlate with periods of lowered relative sea level, during the initial rift phase, and record axial sediment supply. The composition of the MTCs corresponds to in situ strata on the adjacent Jade and Judy horsts. The distribution of MTCs implies formation by crestal collapse horsts during the rift climax and represents a transverse system, with no genetic relationship to axial turbidites. In starved deep-marine basins, fine-grained, well-sorted axial systems may provide the most extensive reservoirs. Transverse systems derived from isolated horsts are typically coarse-grained, poorly sorted, and spatially restricted, being unlikely to provide significant reservoir material.

Description: Recent trends and climate models suggest that the Arctic summer sea ice cover is likely to be lost before climate interventions can stabilize it. There are environmental, socioeconomic and sociocultural arguments for, but also against restoring and sustaining current conditions. Even if global warming can be reversed, some people will experience ice free summers before perennial sea ice begins to return. We ask: How will future generations feel about bringing sea ice back where they have not experienced it before? How will conflicted interests in ice-covered vs ice free conditions be resolved? What role will science play in these debates?

Description: Biospheric relationships between production and consumption of biomass have been resilient to changes in the Earth system over billions of years. This relationship has increased in its complexity, from localised ecosystems predicated on anaerobic microbial production and consumption, to a global biosphere founded on primary production from oxygenic photoautotrophs, through the evolution of Eukarya, metazoans, and the complexly networked ecosystems of microbes, animals, fungi and plants that characterise the Phanerozoic Eon (the last ~541 million years of Earth history). At present, one species, Homo sapiens , is refashioning this relationship between consumption and production in the biosphere with unknown consequences. This has left a distinctive stratigraphy of the production and consumption of biomass, of natural resources, and of produced goods. This can be traced through stone tool technologies and geochemical signals, later unfolding into a diachronous signal of technofossils and human bioturbation across the planet, leading to stratigraphically almost isochronous signals developing by the mid-20 th century. These latter signals may provide an invaluable resource for informing and constraining a formal Anthropocene chronostratigraphy, but are perhaps yet more important as tracers of a biosphere state that is characterised by a geologically unprecedented pattern of global energy flow that is now pervasively influenced and mediated by humans, and which is necessary for maintaining the complexity of modern human societies.

Description: Petroleum (oil and gas) forms from the bacterial or thermal breakdown of kerogen during progressive burial in sedimentary basins. During times of petroleum generation, kerogens in organic-rich source rocks expel petroleum to form a fluid phase in the pore system, capable of migrating under hydrodynamic and buoyancy forces to ultimately escape to the surface or accumulate within petroleum traps in the subsurface. The relative timing of petroleum charge and trap formation is a vital component in the accumulation of petroleum deposits. Exhumed basins have been historically viewed as higher-risk targets for conventional petroleum exploration because of, inter alia, the switch-off of petroleum generation in the source rock at the commencement of cooling during exhumation. However, even at the switch-off point, the source rock may retain a significant volume of petroleum sorbed in kerogen and within its pore system. Herein we demonstrate that if the source rock is exhumed to shallower depths after peak burial, pore pressure reduction and the associated volumetric expansion of the petroleum—particularly of the gaseous—phase in the pore system will result in the discharge of additional petroleum into the adjacent carrier bed or reservoir formations. Because most onshore sedimentary basins are characterized by major exhumation events at some point in their history, this represents an additional and underappreciated mechanism for a late-stage petroleum charge in exhumed sedimentary basins. The modeling also indicates that both the initial, pre-exhumation, total gas storage capacity and the exhumation gas charge are likely to be volumetrically more significant for gas-bearing source rocks that have been exposed to higher initial pressures and lower thermal gradients. The concepts presented here also have implications for petroleum resources retained within unconventional shale reservoirs because high-graded shale plays may be associated with systems where the magnitude or rate of relative overpressure dissipation has limited exhumation charge from the unconventional to conventional reservoirs within the basin.

Description: An estimate or measurement of organic matter density is required for converting between the weight percent of total organic carbon (TOC) and the volume percent of organic matter for wireline log calibration; it is therefore important to recognize when significant changes in organic matter density occur. A method is presented for calculating organic matter density from measurements of crushed-rock dry grain density and Soxhlet-extracted TOC. I have investigated the thermal evolution of organic matter by tracking changes in the intrinsic density of organic matter as a function of thermal maturity. Organic matter density shows two step increases that correspond to the generation of liquid hydrocarbons in the oil window (up to ~1.2% vitrinite reflectance [ R o ]) and the conversion of organic matter to graphitelike carbon (more correctly, "turbostratic carbon") at high thermal maturity (〉4% R o ). Profound structural changes of organic matter may, in part, determine the maturity limits of source-rock tight liquids and shale-gas plays, particularly at high thermal maturity, where gas is hosted within the organic matter–hosted pore system.

Description: Apatite fission track (AFT) and vitrinite reflectance data from five exploration wells and three seafloor cores illuminate the thermal history of the underexplored United States Chukchi shelf. On the northeastern shelf, Triassic strata in the Chevron 1 Diamond well record apatite annealing followed by cooling, possibly during the Triassic to Middle Jurassic, which is a thermal history likely related to Canada Basin rifting. Jurassic strata exhumed in the hanging wall of the frontal Herald Arch thrust fault record a history of probable Late Jurassic to Early Cretaceous structural burial in the Chukotka fold and thrust belt, followed by rapid exhumation to near-surface temperatures at 104 ± 30 Ma. This history of contractional tectonism is in good agreement with inherited fission track ages in low-thermal-maturity, Cretaceous–Cenozoic strata in the Chukchi foreland, providing complementary evidence for the timing of exhumation and suggesting a source-to-sink relationship. In the central Chukchi foreland, inverse modeling of reset AFT samples from the Shell 1 Klondike and Shell 1 Crackerjack wells reveals several tens of degrees of cooling from maximum paleo-temperatures, with maximum heating permissible at any time from about 100 to 50 Ma, and cooling persisting to as recent as 30 Ma. Similar histories are compatible with partially reset AFT samples from other Chukchi wells (Shell 1 Popcorn, Shell 1 Burger, and Chevron 1 Diamond) and are probable in light of regional geologic evidence. Given geologic context provided by regional seismic reflection data, we interpret these inverse models to reveal a Late Cretaceous episode of cyclical burial and erosion across the central Chukchi shelf, possibly partially overprinted by Cenozoic cooling related to decreasing surface temperatures. Regionally, we interpret this kinematic history to be reflective of moderate, transpressional deformation of the Chukchi shelf during the final phases of contractional tectonism in the Chukotkan orogen (lasting until ~70 Ma), followed by renewed subsidence of the Chukchi shelf in the latest Cretaceous and Cenozoic. This history maintained modest thermal maturities at the base of the Brookian sequence across the Chukchi shelf, because large sediment volumes bypassed to adjacent depocenters. Therefore, the Chukchi shelf appears to be an area with the potential for widespread preservation of petroleum systems in the oil window.

Description: Advances in virtual outcrop technologies and their introduction to fracture characterization allow extraction of fracture data from very large and inaccessible areas. The recent development of automated or semiautomated methods for fracture extraction aims to reduce or avoid tedious, time-consuming, and biased manual interpretation of fractures from virtual outcrops. We present a benchmarking exercise between a previously proposed automated fracture picking method, manual picking, and fieldwork methods. Comparison between the three methods highlighted their relative advantages and limitations. The automated fracture picking method provided excellent results in terms of fracture orientation, size, spatial distribution, and density. Fieldwork is complementary to fracture extraction from virtual outcrops, and it should focus on quality control of remote sensing data, poorly exposed areas, small-scale observations, diagenesis, timing of fracture development, building conceptual models, and linking fracture stratigraphy to rock properties. We propose a best practice for the use and integration of manual and/or automated fracture extraction from virtual outcrop and fieldwork data for fracture characterization and modeling from outcrop analogs. We consider integration of different methods as the best way to improve the modeling exercise while reducing operational costs and risks.

Description: Because of its significant impact on relative permeability, capillary pressure, stimulation methods, and ultimate recovery, the wettability of reservoir rocks is a critical factor of the petroleum recovery process. However, characterizing the wettability of shale with extremely low matrix permeabilities is a challenging task because of the dominant presence of nanopores in shale and high heterogeneity of shale compositions at multiple scales. From spontaneous imbibition behavior that uses two types of imbibing fluid (water and n-decane), the present study examines the wettability characteristics of gas-window Barnett Shale samples taken from four different depths of Texas United 1 Blakely core in Wise County in Texas. Imbibition experiments were conducted in two directions: parallel and transverse to the lamination of the samples. A scaling method was used to analyze imbibition data, and observed imbibition behaviors were interpreted to infer the different wettability conditions of four samples with different mineralogy, total organic carbon content, and pore-throat size distribution. Our results show that wettability significantly affects fluid imbibition behavior and that four tested samples can be divided into three wettability categories: more water wet, mixed wet, and more oil wet. Overall, the variable wettability of Barnett samples will affect hydrocarbon storage, distribution, and production.

Description: The prolific Los Angeles basin in California may be the most petroliferous province on Earth per volume of sedimentary fill. However, because most exploration in the basin occurred prior to the advent of modern geochemical methods, genetic relationships among the various petroleum accumulations and their source rocks have remained speculative. A training set of 24 source-related biomarker and stable carbon isotope ratios for 111 non- or mildly biodegraded oil samples from the basin was used to construct a chemometric (multivariate statistics) decision tree. The decision tree allows genetic classification of additional oil or source-rock extract samples that might be collected. The decision tree identifies 6 tribes and a total of 12 genetically distinct oil families. The families have different bulk properties, such as API gravity and sulfur content, which were previously explained as resulting from secondary processes, including thermal maturity or biodegradation. However, the chemometric assignments are based on genetic properties that reflect distinct organofacies. The oil families occur in different locations and reservoir intervals in the basin, consistent with their origins from different organofacies of active source rock. The source-rock depositional environment for each oil family can be inferred using biomarker and isotope ratios. The samples show stable carbon isotope ratios for saturate and aromatic hydrocarbons that indicate different organofacies of Miocene marine source rocks. Tribes 1 and 2 straddle the central trough, mainly occur east of the Newport-Inglewood fault zone (NIFZ), and show evidence of proximal, clay-rich source rock deposited under suboxic conditions with elevated angiosperm input. Tribes 3–6 occur west of the NIFZ and show evidence of more distal, clay-poor source rock deposited under anoxic conditions. Geochemistry and stratigraphy of the oil tribes (1–6 below) suggest the following source-rock organofacies:

Description: The origin of the overpressure in the northern Qaidam Basin has not been clearly understood, which has caused some difficulties in hydrocarbon exploration. Using a compaction study, we applied a modified acoustic-velocity and effective-stress diagram to identify the overpressure transfer in the study area. This phenomenon has not been discussed in previous studies. For the present study, we approximately calculated the magnitude of the transfer overpressure and analyzed the cause of the overpressured aquifer at the crest of the anticline in the study area. Our study indicates that the effect of overpressure transfer is very distinct, and the largest contribution to the total overpressure is 57%. The main media of overpressure transfer include vertical faults and lateral conducting layers. The vertical faults can connect deep overpressured strata, and the lateral conducting layers can connect overpressured strata at the top and wing of the anticline. During anticline formation, the crest fractures, and then the overpressured water in the anticline wing flows into the fractured crest and forms the overpressure compartment that prevents the charging of deeper natural gas.

Description: Tidal heterolithic sandstones are commonly characterized by millimeter- to centimeter-scale intercalations of mudstone and sandstone. Consequently, their effective flow properties are poorly predicted by (1) data that do not sample a representative volume or (2) models that fail to capture the complex three-dimensional architecture of sandstone and mudstone layers. We present a modeling approach in which surfaces are used to represent all geologic heterogeneities that control the spatial distribution of reservoir rock properties (surface-based modeling). The workflow uses template surfaces to represent heterogeneities classified by geometry instead of length scale. The topology of the template surfaces is described mathematically by a small number of geometric input parameters, and models are constructed stochastically. The methodology has been applied to generate generic, three-dimensional minimodels (9 m 3 [~318 ft 3 ] volume) of cross-bedded heterolithic sandstones representing trough and tabular cross bedding with differing proportions of sandstone and mudstone, using conditioning data from two outcrop analogs from a tide-dominated deltaic deposit. The minimodels capture the cross-stratified architectures observed in outcrop and are suitable for flow simulation, allowing computation of effective permeability values for use in larger-scale models. We show that mudstone drapes in cross-bedded heterolithic sandstones significantly reduce effective permeability and also impart permeability anisotropy in the horizontal as well as vertical flow directions. The workflow can be used with subsurface data, supplemented by outcrop analog observations, to generate effective permeability values to be derived for use in larger-scale reservoir models. The methodology could be applied to the characterization and modeling of heterogeneities in other types of sandstone reservoirs.