Dynamic mechanisms of tight gas accumulation and numerical simulation methods: Narrowing the gap between theory and field application

Despite the significant progress made in tight gas exploration and development in recent years, the understanding of the dynamic mechanisms of tight gas accumulation is still limited, and numerical simulation methods are lacking. In fact, the gap between theory and field application has become an obstacle to the development of tight gas exploration and development. This work sheds light on the dynamic mechanisms of hydrocarbon accumulation in tight formations from the aspect of capillary self-sealing theory by embedding calculation of pressure- and temperature-dependent capillary force in a pore network model. The microscale dynamic mechanisms are scaled up to the reservoir level by geological simulation, and the quantitative evaluation of reserves based on real geological sections is realized. From the results, several considerations are made to assist with resource assessment and sweet spot prediction. Firstly, the self-sealing effect of capillary in the micro-nano pore-throat system is at the core of tight sandstone gas accumulation theory; the hydrocarbon-generated expansion force is the driving force, and capillary force comprises the resistance. Furthermore, microscopic capillary force studies can be embedded into a pore network model and scaled up to a geological model using relative permeability curve and capillary force curve. Field application can be achieved by geological numerical simulations at the reservoir scale. Finally, high temperature and high pressure can reduce capillary pressure, which increases gas saturation and reserves.Cited as: Zhao, W., Jia, C., Song, Y., Li, X., Hou, L., Jiang, L. Dynamic mechanisms of tight gas accumulation and numerical simulation methods: Narrowing the gap between theory and field application. Advances in Geo-Energy Research, 2023, 8(3): 146-158. https://doi.org/10.46690/ager.2023.06.0

Paleoenvironment and chemostratigraphy heterogenity of the Cretaceous organic-rich shales

The Cretaceous Qingshankou Formation in the Songliao Basin is rich in shale oil resources, which has become one of the most important exploration targets of lacustrine shale oil in China. Based on X-ray fluorescence element analysis, X-ray diffraction analysis, total organic carbon, rock pyrolysis, scanning electron microscope and nitrogen adsorption, the Paleoenvironment was reconstructed by comprehensive utilization of integrated prediction error filter analysis of chemical stratigraphy, and its relationship with organic geochemistry, mineralogy and pore structure was discussed. The results indicated that the Qingshankou Formation was deposited in the environment with fresh water-brackish water, semi-deep/deep water and strong reduction. The evolution of Paleoenvironment during the deposition of Qingshankou Formation changed from bottom to top, with increasing water depth, decreasing salinity and oxygen content. Paleosalinity was positively correlated with total organic carbon, residual hydrocarbon and carbonate mineral content. From bottom to top, the contents of carbonate and chlorite decreased, while the contents of plagioclase and clay minerals increased slightly. The pores were dominated by intra-illite pores, intra-I/S mixed-layer pores and intra-pyrite pores. Some intra-plagioclase pores and calcite dissolution pores were developed, and the organic matter pores are slightly few. Nitrogen adsorption data showed that the dominate pore size was 40-53 nm. This study clarifies the Paleoenvironmental evolution of the Qingshankou Formation, and may shed lights on lacustrine shale oil accumulation and sweet-spotting.Cited as: Guan, M., Wu, S., Hou, L., Jiang, X., Ba, D., Hua, G. Paleoenvironment and chemostratigraphy heterogenity of the Cretaceous organic-rich shales. Advances in Geo-Energy Research, 2021, 5(4): 444-455, doi: 10.46690/ager.2021.04.0

Assessing Reproducibility of Inherited Variants Detected With Short-Read Whole Genome Sequencing

Background: Reproducible detection of inherited variants with whole genome sequencing (WGS) is vital for the implementation of precision medicine and is a complicated process in which each step affects variant call quality. Systematically assessing reproducibility of inherited variants with WGS and impact of each step in the process is needed for understanding and improving quality of inherited variants from WGS. Results: To dissect the impact of factors involved in detection of inherited variants with WGS, we sequence triplicates of eight DNA samples representing two populations on three short-read sequencing platforms using three library kits in six labs and call variants with 56 combinations of aligners and callers. We find that bioinformatics pipelines (callers and aligners) have a larger impact on variant reproducibility than WGS platform or library preparation. Single-nucleotide variants (SNVs), particularly outside difficult-to-map regions, are more reproducible than small insertions and deletions (indels), which are least reproducible when \u3e 5 bp. Increasing sequencing coverage improves indel reproducibility but has limited impact on SNVs above 30×. Conclusions: Our findings highlight sources of variability in variant detection and the need for improvement of bioinformatics pipelines in the era of precision medicine with WGS

Assessing reproducibility of inherited variants detected with short-read whole genome sequencing

Background: Reproducible detection of inherited variants with whole genome sequencing (WGS) is vital for the implementation of precision medicine and is a complicated process in which each step affects variant call quality. Systematically assessing reproducibility of inherited variants with WGS and impact of each step in the process is needed for understanding and improving quality of inherited variants from WGS. Results: To dissect the impact of factors involved in detection of inherited variants with WGS, we sequence triplicates of eight DNA samples representing two populations on three short-read sequencing platforms using three library kits in six labs and call variants with 56 combinations of aligners and callers. We find that bioinformatics pipelines (callers and aligners) have a larger impact on variant reproducibility than WGS platform or library preparation. Single-nucleotide variants (SNVs), particularly outside difficult-to-map regions, are more reproducible than small insertions and deletions (indels), which are least reproducible when > 5 bp. Increasing sequencing coverage improves indel reproducibility but has limited impact on SNVs above 30x. Conclusions: Our findings highlight sources of variability in variant detection and the need for improvement of bioinformatics pipelines in the era of precision medicine with WGS.Peer reviewe

Shale Mineralogy Analysis Method: Quantitative Correction of Minerals Using QEMSCAN Based on MAPS Technology

Shale is of strong heterogeneity. The mineral composition has a significant influence on the diagenetic evolution, pore network formation, hydrocarbon content, oil mobility, and reservoir stimulation of shale. Accurate mineral analysis of shale is an essential precondition for scientific research and industrial production. In this study, we present a new quantitative method for shale mineral analysis based on high-resolution images, using a combination of QEMSCAN and MAPS technology. We overcome the problem of errors between the morphology and content of certain minerals identified by QEMSCAN technology and the actual results and take full advantage of high-resolution large-scale backscatter scanning electron microscopy (MAPS technology) to process clay-grade mineral image data with complex contact relationships. Specifically, we realize the correction of QEMSCAN mineral quantitative analysis results through image smoothing, image alignment, image segmentation, morphological analysis, and other image processing technologies. The method enables the precise and fast measurement of mineral types, contents, and two-dimensional (2D) distributions. It provides a more credible result consistent with geological reality than QEMSCAN. A straightforward application of the new method is refined mineralogical analysis, including the characterization of pores, fractures, organic matter, and/or mineral grains in geological materials

Controlling factors of volcanic hydrocarbon reservoirs in Bohai Bay Basin, China

Volcanic hydrocarbon reservoirs are developed in the Mesozoic and Cenozoic strata in Bohai Bay Basin in China. There is more than one hundred million tons of proven oil reserves in the said reservoir. They performed different actors for oil and gas accumulation in the basin. Faults controlled the distribution and accumulation of oil and gas related to volcanic rocks in Bohai Bay Basin. Not to mention, the zone near the faults is favorable for the development of good reservoirs. Volcanic rocks and volcanism can serve several roles during the course of hydrocarbon generation and accumulation. Volcanism can promote hydrocarbon generation from source rocks. Simultaneously, volcanic activity can damage petroleum reservoirs. Volcanic rocks can be both the reservoirs and the cap-rocks or obscured layer in the basin. The occurrence of volcanic rocks in source rocks can form fractures more easily compared to that in sandstones. Finally, volcanic rocks also control the distribution of mantle-derived CO2 gas reservoirs in the basin

Failure Of Hearing Acquisition in Mice With Reduced Expression of Connexin 26 Correlates With the Abnormal Phasing of Apoptosis Relative to Autophagy and Defective ATP-Dependent Ca2+ Signaling in Kölliker’s Organ

Mutations in the GJB2 gene that encodes connexin 26 (Cx26) are the predominant cause of prelingual hereditary deafness, and the most frequently encountered variants cause complete loss of protein function. To investigate how Cx26 deficiency induces deafness, we examined the levels of apoptosis and autophagy in Gjb2loxP/loxP; ROSA26CreER mice injected with tamoxifen on the day of birth. After weaning, these mice exhibited severe hearing impairment and reduced Cx26 expression in the cochlear duct. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cells were observed in apical, middle, and basal turns of Kölliker’s organ at postnatal (P) day 1 (P1), associated with increased expression levels of cleaved caspase 3, but decreased levels of autophagy-related proteins LC3-II, P62, and Beclin1. In Kölliker’s organ cells with decreased Cx26 expression, we also found significantly reduced levels of intracellular ATP and hampered Ca2+ responses evoked by extracellular ATP application. These results offer novel insight into the mechanisms that prevent hearing acquisition in mouse models of non-syndromic hearing impairment due to Cx26 loss of function

Valproate Sodium Protects Blood Brain Barrier Integrity in Intracerebral Hemorrhage Mice

Valproate sodium (VPA) is a traditional antiepileptic drug with a neuroprotective role in cerebrovascular disease. After intracerebral hemorrhage (ICH), mechanical compression by hematoma, neuroinflammation, oxidative stress, and cytotoxicity of hematoma lysates caused the destruction of the blood brain barrier (BBB). Targeting BBB is a major therapeutic method for patients with ICH. The purpose of the present study was to explore the role of VPA in preserving BBB integrity in the ICH model and investigate the underlying molecular mechanisms. One hundred and thirty-six adult male CD1 mice were randomly divided into five groups in the study. Mice subjected to ICH were administered intraperitoneally with VPA at 3, 24, and 48 h post-ICH, respectively. Neurobehavioral assessments, BBB permeability, Evans blue fluorescence, hematoma volume, and protein expression were evaluated. The administration of VPA reduced BBB permeability and improved the neurobehavior significantly post-ICH. VPA administration significantly decreased the expression of phosphorylated nuclear factor-kappa B (p-NFκB), matrix metalloproteinases 9 (MMP9), tumor necrosis factorα (TNFα), and interleukin-6 (IL-6), while it enhanced the expression of claudin 5 and occludin in the brain. In conclusion, VPA administration maintained the integrity of BBB after experimental ICH, thus reducing brain edema and improving the neurological outcomes. Therefore, VPA administration might be a new therapeutic method to protect BBB integrity for patients with ICH

Serum and Lung Tissue Selenium Measurements in Subjects with Lung Cancer from Xuanwei, China

Background and objective Xuanwei is an area of the highest incidence and mortality with lung cancer in China. The aim of this study is to determine serum selenium concentrations in lung cancer patients from Xuanwei as well as selenium levels of cancerous tissues, cancer-adjacent pulmonary tissues, and normal pulmonary lung tissues from lung cancer patients, and the relationship between selenium and the high incidence of lung cancer in Xuanwei. Methods One hundred and twenty female adults from Xuanwei were enrolled in the study (60 lung cancer patients and 60 with non-tumor and non-respiratory diseases, respectively) and blood samples were collected. Sixty fresh cancerous tissues and their adjacent as well as normal tissues were collected (31 samples from lung cancer patients living in Xuanwei for more than 2 years and 29 from patients in other regions of Yunnan Province outside of Xuanwei, respectively). Serum and tissue selenium concentrations were assayed using a fluorometric method. Results Women with lung cancer had a mean serum selenium value (55.22 μg/L±13.34 μg/L) of averagely 8.47%, significantly lower than that in subjects with non-tumor and non-respiratory disease controls (60.33 μg/L±13.82 μg/L)(P < 0.05). Selenium concentrations in the tumor tissues (0.105 μg/g±0.034 μg/g) were statistically lower than that of normal ones (0.140 μg/g±0.048 μg/g)(P < 0.05) from lung cancer patients in Xuanwei. Statistical differences had not been found between the cases from Xuanwei and non-Xuanwei district, adenocarcinoma and squamous cell carcinoma, among Stage I, Stage II, stage III groups. Conclusion Lower serum selenium state was negatively related to the incidence of lung cancer in Xuanwei. It was likely that lower selenium level of lung tissues was potential risk factor to lead to lung cancer

Weathered volcanic crust and its petroleum geological significance: A case study of the Carboniferous volcanic crust in northern Xinjiang, NW China

The weathered Carboniferous volcanic crust in the northern Xinjiang was analyzed in this paper, using outcrop and core chemical analysis, oil testing and logging data, in order to clarify the characteristics, distribution and petroleum geological significance of weathered volcanic crusts. A complete weathered volcanic crust consists of a 6 layered structure, comprising of a soil layer, hydrolysis zone, leached zone, disintegration zone I, disintegration zone II and parent rock, all of which have different characteristics and markers. The effective reservoir is developed mainly within the leached zone and disintegration zone I. The duration of weathering controls the thickness of the weathered crust. The crust thickness can reach 550 m deep and dates back to approximately 46.3Ma. The lithology, lithofacies and weathering degree control the properties of the weathered crust reservoir. Faults control the seepage of the weathered crust reservoir: the closer a reservoir is to a fault, the larger is its flow radius and seepage. Weathered volcanic crusts were mostly found at palaeogeomorphic high points, slope zones and fault-developed low-lying points, and oil layers near faults have a larger vertical span. We have established a model to evaluate the degree of weathering and effective reservoir generation of volcanic rock, while the well logging analysis could be used to evaluate weathered crust reservoir effectiveness for wells without core data. Key words: weathered volcanic crust, weathered-crust structure, differential weathering, fault, effective reservoir, evaluation metho