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We investigated diagenesis of the sandstones from the DN2 Gas Field of the Kuqa Foreland Basin (KFB), in order to infer the timing of fluid migration and discuss the linkage between fluids and tectonics. The textures and chemical composition of authigenic minerals, fluid evidence from fluid inclusions and formation water measurements were all used to fulfill this aim. Eodiagenesis occurred with the participation of meteoric water and connate water. Mesodiagenesis is related to high salinity fluids, which were attributed as originating from the overlying Neogene Jidike Formation evaporite (principal minerals including halite, anhydrite, glauberite, carnallite and thenardite). The onset of high salinity fluid migration is inferred to occur during the late Miocene (12.4–9.2 Ma) through the use of homogenization temperatures measured in the present study and K‐Ar dating of authigenetic illites from previous work. This period is consistent with the crucial phase (13–10 Ma) that witnessed the rapid uplift of the southern Tianshan Mts and the stage when calcite and anhydrite veins formed in the studied strata. We thus argue that diagenesis related to high salinity fluids occurred as a response to the Tianshan Mts' rapid uplift and related tectonic processes. The flow of high salinity fluids was probably driven by a density gradient and channeled and focused by fractures formed contemporaneously. [ABSTRACT FROM AUTHOR]

The article presents inflation–deflation algorithm for conventional reservoirs which is adopted to derive critical percolation thresholds to evaluate pore connectivity of shales based on digital cores. Topics discussed include series of digital models with the same pore structure as the original digital core; novelty and superiority of the new computational algorithm; and effective derivation of the critical percolation threshold porosities for pore connectivity analysis.

This article reviews the applications of light stable isotope, including carbon, oxygen and hydrogen, in the studies on origin and formation temperature of authigenic carbonate, quartz and clay minerals. Theoretical knowledge and analytical methods for major light stable isotopes are introduced in detail. Negative and positive δ13C values indicate significant differences on the origin of carbonate cements. The δ18O value is an effective palaeotemperature scale for authigenic minerals formation. Various fractionation equations between δ18O and temperature are proposed for carbonate cements, quartz cements and clay minerals, whose merit and demerit, applicable conditions are clarified clearly. Clumped isotope analysis can reconstruct the temperature of carbonate precipitation with no requirement on the δ18O of initial waters, which makes temperature calculation of carbonate cements formation more convenient and accurate. Hydrogen and oxygen isotopes mainly reflect the origin of diagenetic fluid for clay mineral formation, providing reliable evidence for diagenetic environment analysis. This work aims at helping researchers for better understanding the applications of light stable isotope in sandstone diagenesis. [ABSTRACT FROM AUTHOR]

The article present research on Fluid Inclusion re-equilibration in Carbonate Rock caused by freezing during Microthermometric analysis. Topic include samples of carbonate rock from the Middle Ordovician Yijianfang formation selected from Well SHB -5 and Well YJ-1X in the Tarim Basin, with burial depths ranging from 7229.30 m to 7427.30 m .

The pores in shales are mainly of nanometer-scale, and their pore size distribution is very important for the preservation and exploitation of shale gas. This study focused on the organic-rich Lower Silurian black shale from four wells in the Upper Yangtze Platform, and their TOC, mineralogical composition and pore characterization were investigated. Low pressure N2 and CO2 adsorption were conducted at 77.35 K and 273.15 K, respectively, and the pore structures were characterized by modified Brunauer-Emmett-Teller (BET), Dubinin-Radushkevich (DR), t-plot, Barrett-Joyner-Halenda (BJH) and density functional theory (DFT) methods and then the relationship between pore structure and shale gas sorption capacity was discussed. The results indicate that (1) The Lower Silurian shale has high TOC content of 0.92%-4.96%, high quartz content of 30.6%-69.5%, and high clays content of 24.1%-51.2%. The total specific surface area varies from 7.56 m2/g to 25.86 m2/g. Both the total specific surface area and quartz content are positively associated with the TOC content. (2) Shale samples with higher TOC content have more micropores, which results in more complex nanopore structure. Micropore volumes/surface areas and non-micropore surface areas all increase with the increasing TOC content. (3) A combination of N2 and CO2 adsorption provides the most suitable detection range (∼0.3-60 nm) and has high reliability and accuracy for nanopore structure characterization. (4) The TOC content is the key factor to control the gas sorption capacity of the Lower Silurian shale in the Upper Yangtze Platform. [ABSTRACT FROM AUTHOR]