ALBERT

Description: Minerals, Vol. 7, Pages 151: Vertical Heterogeneity of the Shale Reservoir in the Lower Silurian Longmaxi Formation: Analogy between the Southeastern and Northeastern Sichuan Basin, SW China Minerals doi: 10.3390/min7080151 Authors: Jun Liu Yanbin Yao Derek Elsworth Dameng Liu Yidong Cai Li Dong Lower Silurian Longmaxi formation (LSL) shale is widely and continuously distributed in the northeastern Sichuan Basin and, based on structural analogies with the gas producing LSL formation in the southeastern Sichuan Basin, has significant potential for shale gas exploration. However, limited research has been performed to evaluate the shale gas potential in this region. Samples from a recently completed exploratory well (Well-WQ2) in the northeastern Sichuan Basin indicate that the LSL shale has a vertical property sequence that closely resembles the vertical property sequences in wells in the gas-producing sections of the southeastern Sichuan Basin. The continuous sampling and analyses of Well-WQ2 have allowed a detailed investigation of the vertical variations in lithofacies, mineral characteristics, pore structures, and organic geochemical characteristics. The Longmaxi formation was divided into two third-order sequences (SQ1 and SQ2) based on systematic core observations and well logging analyses. Both SQ1 and SQ2 include a transgressive system tract (TST) and a high-stand system tract (HST). The lithofacies exhibit an upward decrease in the organic content. From SQ1 to SQ2, the quartz content, in situ graptolite content, total organic carbon (TOC) content, and brittleness index decrease, but the clay mineral content increases. The LSL shale sections from depths of 1204 to 1214 m and from 1271 to 1282 m possess well-developed fractures and high permeability. Additionally, the average porosity and permeability in SQ1 are higher than those in SQ2. In addition, the positive correlation between the TOC and quartz contents of the assayed samples suggests that much of the quartz is of biogenic origin. Changes in the sedimentary and diagenetic environments during deposition are two key factors that contribute to the observed vertical heterogeneity of the Longmaxi formation. In conclusion, the shale sections of the lower part of the SQ1, like their analogs in the southeastern Sichuan Basin, are the most favorable targets for shale gas production in the northeastern Sichuan Basin.

Description: Minerals, Vol. 7, Pages 179: Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the Sichuan Basin, SW China Minerals doi: 10.3390/min7100179 Authors: Jun Liu Yanbin Yao Dameng Liu Zhejun Pan Yidong Cai This study performs a comprehensive comparison of three key marine shale reservoirs in the southeastern margin of the Sichuan Basin, and explains why commercial gas production was only achieved in the Lower Silurian Longmaxi (LSL) and Upper Ordovician Wufeng (UOW) formations, but not in the Lower Cambrian Niutitang (LCN) formation. The experimental methods included in situ gas content and gas composition tests, methane adsorption analysis, low-pressure N2 adsorption, field emission scanning electron microscopy (FE-SEM), and total organic carbon (TOC) and vitrinite reflectance (Ro) analyses to evaluate the lithology, mineralogy, physical properties of the reservoir, organic geochemistry, in situ gas content and methane adsorption capacity characteristics of the three shales. The LCN shale has lower quartz and clay mineral contents and a low brittleness index, but higher contents of feldspar, pyrite and carbonate minerals than the LSL and UOW shales. The porosity and permeability of the LSL and UOW shales are higher than those of the LCN shale. The primary contributions to the high permeability in the LSL shale are its well-developed fractures and organic matter pores. In contrast, the over-mature LCN shale is unfavorable for the development of organic pores and fractures. Although the LCN shale has a higher methane sorption capacity than the LSL and UOW shales, the gas content and methane saturation of the LCN shale are distinctly lower than those of the LSL and UOW shales. This is primarily due to gas migration from the LCN shale, resulting from the activities of tectonic uplift and the unconformable contact between the LCN shale and the Dengying formation. When compared with gas shale in North America, the LSL shale is the most favorable shale reservoir out of the three Sichuan shales, while the combination of the LSL and UOW shales is also potentially productive. However, the individual single layer production of the UOW or LCN shales is still limited due to poor resource potential and/or reservoir physical characteristics in the study area.

Description: Minerals, Vol. 8, Pages 117: Experimental Study of CO2-Water-Mineral Interactions and Their Influence on the Permeability of Coking Coal and Implications for CO2-ECBM Minerals doi: 10.3390/min8030117 Authors: Hui Guo Xiaoming Ni Yanbin Wang Xiaomin Du Tengteng Yu Ruimin Feng Coal permeability is one of the most critical parameters affecting gas flow behavior during coalbed methane (CBM) production. However, little research has been conducted on how permeability evolves after CO2 injection in coking coal. Hence, examining possible chemical interactions between coal minerals, water, and injected CO2 can be very helpful to better characterize coking coal. In this study, coking coal specimens obtained from the Malan and Tunlan mines located in the Gujiao block of the Qinshui basin were treated with water and CO2 to achieve a better understanding of their dissolution kinetics, pore structure, and permeability. It was found that the relative carbonate mineral content decreases with time, while the relative clay mineral content increases after the reaction with CO2 and water. Scanning electron microscopy (SEM) confirmed these mineral alteration phenomena. Carbonate minerals (calcite, dolomite) dissolve faster than clay minerals (montmorillonite, illite and kaolinite). In particular, the dissolution rates of Ca2+ in carbonate minerals increases with decreasing temperature (25–45 °C) and pH (4.3–6.3), and the dissolution rate of Ca2+ ions in the calcite reaction solution is higher than that in the dolomite solution. In addition, the results of low-pressure nitrogen adsorption analysis showed that CO2 injection can enlarge smaller size pores into larger size pores and change the overall pore size distribution. Therefore, CO2 injection can increase the porosity of coal beds and ultimately their permeability, which in turn facilitates CBM production.

Description: A Paris-Edinburgh press combined with a multi-channel collimator assembly has been commissioned at the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS) beamline for monochromatic X-ray scattering, with an emphasis on studying low-Z liquids, especially silicate liquids at high pressure. The Paris-Edinburgh press is mounted on a general-purpose diffractometer, with a pixel array detector mounted on the detector arm. The incident monochromatic undulator beam with energies up to 60 keV is focused both horizontally and vertically to a beam size about 30 × 30 µm. With this setup, background scattering from the surrounding pressure media is completely removed at 2θ angles above 10° for samples larger than 1.05 mm in diameter. Thirty minutes is typically sufficient to collect robust X-ray scattering signals from a 1.6 mm diameter amorphous silicate sample. Cell assemblies for the standard Paris-Edinburgh anvils have been developed and pressures and temperatures up to 7 GPa and 2300 K, respectively, have been maintained steadily over hours. We have also developed a cupped-toroidal Drickamer anvil to further increase pressure and temperature capabilities. The cupped-toroidal Drickamer anvil combines features of a modified Drickamer anvil and the traditional Paris-Edinburgh anvil. Pressures up to 12 GPa have been generated at temperatures up to 2100 K.