ALBERT

Description: Reservoir production is highly dependent on reservoir models. A key problem faced in the development of a hydrocarbon reservoir is that of constructing a reservoir model that can generate reliable production forecasts under various development scenarios. Therefore, geological models have to be built in three dimensions (3D). Unfortunately, manual construction of 3D geological models (deterministically) is almost impossible, which explains why geologists often limit their interpretation to two dimensional (2D) correlation panels, fence-diagrams or maps. Consequently, geological conceptual models are rarely included or considerably simplified in reservoir models used for flow simulations and replaced by stochastic or geostatistic approaches. In spite of this admission of failure, sedimentological cross-sections and maps contain most of the knowledge and concepts of sedimentologists. They represent the outcome of sedimentological studies, including available well data, seismic interpretation and especially sedimentological and environmental concepts, incorporating all facies transitions and successions in a high-resolution stratigraphic framework. They allow fine temporal- and spatial-scale sedimentological heterogeneities to be identified. The integration of these fine-scale sedimentological heterogeneities is an essential step in improving the precision and accuracy of static reservoir models and volumetric calculations. This paper demonstrates the quantitative influence of introducing sedimentological information into the reservoir characterization workflow using a simple deterministic workflow. The described incorporation of sedimentological knowledge through facies 3D proportions cubes allows a direct assessment to facies distribution multi-realization scheme and associated uncertainties by applying stochastic simulations.

Description: A new inverse numerical modeling method is used to constrain the environmental parameters (e.g., relative-sea-level, sediment-supply, and wave climate histories) that control stratigraphic architecture in wave-dominated shallow-marine deposits. The method links a "process-response" forward stratigraphic model that simulates wave and storm processes (BARSIM) to a combination of inverse methods formulated in a Bayesian framework that allows full characterization of uncertainties. This method is applied for the first time to a real geologic dataset, collected at outcrop from two shoreface-shelf parasequences in the Aberdeen Member, Blackhawk Formation of the Book Cliffs, east-central Utah, USA. The environmental parameters that controlled the observed stratigraphic architecture are quantified, and key aspects of stratigraphic architecture are successfully predicted from limited data. Stratigraphic architecture at parasequence-stacking and intra-parasequence scales was driven principally by relative sea level (varying by up to about 55 m) and sediment supply (varying by up to 70 m2/yr), whose interplay determines the shoreline trajectory. Within zones of distinctive shoreline trajectory, variations in wave climate (of up to about 3 m in fairweather-wave height) controlled superimposed variations in sandstone and shale content (e.g., the development of upward-coarsening and upward-fining bedsets). The modeling results closely match the observed stratigraphic architecture, but their quality is limited by: (1) the formulation and assumptions of the forward-modeling algorithms, and (2) the observed data distribution and quality, which provide poor age constraint.

Description: This study addressed the architecture and dimension distributions of fluvial deposits of the Olson Member of the Escanilla Formation through analysis of outcrops in the southern Buil syncline, Ainsa Basin, south central Pyrenees, Spain. The Olson Member consists of wide multistory channels alternating with mud-rich intervals composed of flood-plain deposits and "isolated" individual channels. Field descriptions and a combination of terrestrial light detection and ranging data and digital orthophotographs were used to map and document the abundance, distribution, and dimensions of sandstone bodies. These data show that channels are distributed according to the local stratigraphic framework and differential subsiding areas. Morphology (width, depth, and sinuosity) of the channels throughout the sequence evolve according to their stratigraphic position. During low-accommodation periods, channels stacked laterally, forming wide multistory channel belts. Under these conditions, single channels have a mean width-to-thickness (W:T) ratio of 49. During high-accommodation periods, single channels have a mean W:T ratio of 29. Moreover, the tendency of narrower and thicker channels having developed during high-accommodation periods is also clearly observable vertically from the base to the top of high-accommodation intervals throughout the sequence. This pattern of deposition results in increasing vertical connectivity, even in mud-rich high-accommodation periods. A geocellular three-dimensional model has been performed using object-based simulations. A succession of stochastic simulations was performed from the simplest one (random simulations) to more elaborated simulations, integrating successively outcrop observations. These simulations serve to image sandstone bodies' connectivity evolution according to outcrop observations and sedimentologic knowledge. Subsurface application of such vertical channel morphology evolutions and distribution could lead to more predictive flow-unit definitions and extensions.

Description: Hydrocarbon fields consisting of turbidite deposits are commonly more complex than anticipated because of fine-scale sedimentary heterogeneities, which complicate the reservoir characteristics. This is particularly evident in turbiditic channel complexes with lateral channel migration. The creation of fine-scale models is founded on high-resolution seismic data, incorporating all available data together with concepts of the internal reservoir architecture. The model is essential for understanding the impact of these phenomena on reservoir characteristic distributions. The lateral extents and a real distribution of heterogeneity are still unknown; thus, our modeling workflow is incorporated into an uncertainty chain to identify and measure all uncertainties with a possible effect on static connectivity. Internal channel complex fill is composed of multiple individual (elementary) channel stacks formed during repeated erosion-deposition cycles. These elementary structures allow sand transport through deep-sea areas and the preservation of slumps and slides on channel borders, resulting in the formation of internal heterogeneities. The sideways and downdip movement of elementary channels in turbidite complexes show two typical channel patterns: lateral migration and vertical stacking. The spatial distribution of slide heterogeneities is therefore constrained by the different channel patterns. Distinguishing between these two patterns provides an understanding of heterogeneity distributions and the resulting differences in static connectivity. These contrasts can be explained as distinct preservation rates of mass-transport slide sediments within elementary channels and can thus be included in reservoir models to define preferential zones of heterogeneity preservation along turbidite complexes. Richard Labourdette has 15 years of experience in the petroleum industry and has been involved in the three-dimensional sedimentary modeling project of Total since 1993. He received his M.Sc. degree in reservoir geology and is currently finishing his Ph.D. (Montpellier University). His main focus is the sedimentary modeling of reservoirs and analog outcrops. He is part of the European Association of Geoscientists and Engineers Distinguished Lecturer Program (2005, 2006, and 2007).

Description: This study addressed the architecture and dimension distributions of fluvial deposits of the Olson Member of the Escanilla Formation through analysis of outcrops in the southern Buil syncline, Ainsa Basin, south central Pyrenees, Spain. The Olson Member consists of wide multistory channels alternating with mud-rich intervals composed of flood-plain deposits and “isolated” individual channels. Field descriptions and a combination of terrestrial light detection and ranging data and digital orthophotographs were used to map and document the abundance, distribution, and dimensions of sandstone bodies. These data show that channels are distributed according to the local stratigraphic framework and differential subsiding areas. Morphology (width, depth, and sinuosity) of the channels throughout the sequence evolve according to their stratigraphic position. During low-accommodation periods, channels stacked laterally, forming wide multistory channel belts. Under these conditions, single channels have a mean width-to-thickness (W:T) ratio of 49. During high-accommodation periods, single channels have a mean W:T ratio of 29. Moreover, the tendency of narrower and thicker channels having developed during high-accommodation periods is also clearly observable vertically from the base to the top of high-accommodation intervals throughout the sequence. This pattern of deposition results in increasing vertical connectivity, even in mud-rich high-accommodation periods. A geocellular three-dimensional model has been performed using object-based simulations. A succession of stochastic simulations was performed from the simplest one (random simulations) to more elaborated simulations, integrating successively outcrop observations. These simulations serve to image sandstone bodies' connectivity evolution according to outcrop observations and sedimentologic knowledge. Subsurface application of such vertical channel morphology evolutions and distribution could lead to more predictive flow-unit definitions and extensions. Richard Labourdette has 17 yr of experience in the petroleum industry and has been involved in the three-dimensional sedimentary modeling project of Total since 1993. He received his Ph.D. from Montpellier University. His main focus is the sedimentary modeling of reservoirs and analog outcrops. He is part of the European Association of Geoscientists and Engineers Distinguished Lecturer Program (2005–2008).

Description: In turbidite settings, channel sand bodies stack laterally and vertically as a function of turbidite story confinement degree. Therefore, we can establish a simple mathematical relationship between these parameters to represent and model complex reservoir features. The morphology of eight well-imaged turbidite complexes from west Africa (from upper Oligocene to Pleistocene deposits) was studied to improve the understanding of their evolution and to assess depositional processes. Measurements of individual channels are treated statistically and compared with channel story characteristics. Based on this geometric analysis, we establish a relationship between the degree of channel story confinement and the stacking architecture of channelized sand bodies. This relationship allows an assessment of reservoir architecture and connectivity for different depositional settings characterized by channel story confinement. Less-confined channel stories characterized by lateral migration patterns with low vertical amalgamation have a tabular amalgamated architecture where connectivity is related to channel margin heterogeneities. As confinement increases, downdip and vertical movement components increase, leading to ribbon platform and vertical amalgamation of sand bodies. Resulting reservoir characteristics are highly variable along channel stories, depending on downdip and vertical component ratios. According to our observations, the degree of confinement exerts an important control on turbidite flows and the ultimate distribution and architecture of sedimentary bodies. Richard Labourdette has 17 years of experience in the petroleum industry and has been involved in the three-dimensional sedimentary modeling project of Total since 1993. He received his Ph.D. from Montpellier University. His main focus is the sedimentary modeling of reservoirs and analog outcrops. He is part of the European Association of Geoscientists and Engineers distinguished lecturer program (2005 to 2008). Martine Bez is a senior sedimentologist at Total's Geoscience Technology and Research Center. She received a Ph.D. from the University of Lyon. She has been involved in several projects in Tertiary turbidite fields from the Congo-Angolan margin and the Niger Delta. She is a research and development team leader on ancient and modern turbidite system analogs.