Evaluation of voltage-dependent calcium channel gamma gene families identified several novel potential susceptible genes to schizophrenia

Voltage-gated L-type calcium channels (VLCC) are distributed widely throughout the brain. Among the genes involved in schizophrenia (SCZ), genes encoding VLCC subunits have attracted widespread attention. Among the four subunits comprising the VLCC (α − 1, α −2/δ, β, and γ), the γ subunit that comprises an eight-member protein family is the least well understood. In our study, to further investigate the risk susceptibility by the γ subunit gene family to SCZ, we conducted a large-scale association study in Han Chinese individuals. The SNP rs17645023 located in the intergenic region of CACNG4 and CACNG5 was identified to be significantly associated with SCZ (OR = 0.856, P = 5.43 × 10(−5)). Similar results were obtained in the meta-analysis with the current SCZ PGC data (OR = 0.8853). We also identified a two-SNP haplotype (rs10420331-rs11084307, P = 1.4 × 10(−6)) covering the intronic region of CACNG8 to be significantly associated with SCZ. Epistasis analyses were conducted, and significant statistical interaction (OR = 0.622, P = 2.93 × 10(−6), P(perm) < 0.001) was observed between rs192808 (CACNG6) and rs2048137 (CACNG5). Our results indicate that CACNG4, CACNG5, CACNG6 and CACNG8 may contribute to the risk of SCZ. The statistical epistasis identified between CACNG5 and CACNG6 suggests that there may be an underlying biological interaction between the two genes

Evaluation of genetic susceptibility of common variants in CACNA1D with schizophrenia in Han Chinese

The heritability of schizophrenia (SCZ) has been estimated to be as high as 80%, suggesting that genetic factors may play an important role in the etiology of SCZ. Cav1.2 encoded by CACNA1C and Cav1.3 encoded by CACNA1D are dominant calcium channel-forming subunits of L-type Voltage-dependent Ca(2+) channels, expressed in many types of neurons. The CACNA1C has been consistently found to be a risk gene for SCZ, but it is unknown for CACNA1D. To investigate the association of CACNA1D with SCZ, we designed a two-stage case-control study, including a testing set with 1117 cases and 1815 controls and a validation set with 1430 cases and 4295 controls in Han Chinese. A total of selected 97 tag single nucleotide polymorphisms (SNPs) in CACNA1D were genotyped, and single-SNP association, imputation analysis and gender-specific association analyses were performed in the two independent datasets. None was found to associate with SCZ. Further genotype and haplotype association analyses indicated a similar pattern in the two-stage study. Our findings suggested CACNA1D might not be a risk gene for SCZ in Han Chinese population, which add to the current state of knowledge regarding the susceptibility of CACNA1D to SCZ

Natural gas migration and accumulation model and favorable exploration targets in Ordovician dolomite in Jingxi, Ordos Basin

The Ordovician dolomite reservoir in Ma5(5)-Ma5(10) sub-members in Jingxi in Ordos Basin is a newly discovered field with multiple natural gas pools. The gas accumulation patterns of the reservoir are unclear. Considering the geological background, the genesis, migration, and accumulation of natural gas in Jingxi were studied systematically, and favorable exploration targets were predicted. Natural gas in Ma5(5)-Ma5(10) sub-members is a mixture of Upper Paleozoic and Ordovician products. The Upper Paleozoic coaliferous gas was mainly expulsed downward through the hydrocarbon-providing window where the coal-bearing source rocks made contact with the dolomite reservoirs. The gas then migrated from west to east and accumulated under the condition of lithology variation. The Ordovician petroliferous gas mainly migrated from bottom to top through fractures and mixed with the coaliferous gas in Ma5(5)-Ma5(10) sub-members. The natural gas reservoir formation model was summarized as the migration of gas over a short distance and partial charging into the dolomite reservoirs from the Late Triassic to Middle Jurassic, and the migration of gas over a long distance and massive charging into the dolomite reservoirs during the Late Cretaceous. Ma5(5) and Ma5(6) sub-members are the focus of further exploration, and petroliferous gas in Ma5(7)-Ma5(10) sub-members deserves attention. The dolomite reservoirs of the hydrocarbon-providing windows and the east of these locations are the favorable exploration targets

Exploration practices and prospect of Upper Paleozoic giant gas fields in the Ordos Basin

Natural gas resources is abundant in the Ordos Basin, where six gas fields with more than 100 billion cubic meters of gas reserves have been successively developed and proved, including Jingbian, Yulin, Zizhou, Wushenqi, Sulige and Shenmu. This study aims to summarize the fruitful results and functional practices achieved in the huge gas province exploration, which will be regarded as guidance and reference for the further exploration and development in this basin. Based on the past five decades' successful exploration practices made by PetroChina Changqing Oilfield Company, we first comb the presentation of geological theories at different historical stages as well as the breakthrough in the course. Then, we analyze a complete set of adaptive techniques obtained from the long-time technological research and conclude historical experiences and effective measures in terms of broadening exploration ideas, such as the fluvial delta reservoir-forming theory, giant tight gas reservoir-forming theory, the idea of sediment source system in the southern basin, etc., and innovating technical and management mechanism, such as all-digit seismic prediction, fine logging evaluation for gas formations, stimulation of tight sand reservoirs, flat project and benchmarking management, and so on

Accumulation conditions and exploration and development of tight gas in the Upper Paleozoic of the Ordos Basin

Through lithological analysis of reservoirs, fluid inclusion test and simulation experiment, combined with geochemical, seismic, well logging and formation testing data, this paper studies the favorable geological conditions for tight gas accumulation in the Upper Paleozoic of the Ordos Basin, specifies the characteristics of tight gas reservoirs, and summarizes the key techniques for tight gas exploration and development. The gas source conditions of large area hydrocarbon generation and continuous hydrocarbon injection, widespread delta facies sandstone reservoirs, and the accumulation mode of short-distance migration facilitate the formation of the large-scale tight gas reservoirs in the Upper Paleozoic of the Ordos Basin. The Upper Paleozoic tight gas reservoirs in the Ordos Basin cover a large area and have many gas-bearing formations and multiple pressure systems. The tight reservoirs, which were formed before gas accumulation, are of high heterogeneity. Full digital seismic prediction technique for thin reservoirs, fine logging evaluation technique for tight gas reservoirs, and integrated supporting techniques for gas development provide technical support for further exploration and development. Key words: Ordos Basin, tight gas, accumulation condition, key techniqu

Discovery and reservoir-forming geological characteristics of the Shenmu Gas Field in the Ordos Basin

By the end of 2014, the giant Shenmu Gas Field had been found in the Ordos Basin with an explored gas-bearing area of 4069 km2 and the proved geological gas reserves of 333.4 billion m3. This paper aims to review the exploration history of this field and discusses its reservoir-forming mechanism and geological characteristics, which may guide the further discovery and exploration of such similar gas fields in this basin and other basins. The following research findings were concluded. (1) There are typical tight sand gas reservoirs in this field primarily with the pay zones of the Upper Paleozoic Taiyuan Fm, and secondly with those of the Shanxi and Shihezi Fms. (2) Gas types are dominated by coal gas with an average methane content of 88% and no H2S content. (3) The gas reservoirs were buried 1700–2800 m deep underneath with multiple pressure systems and an average pressure coefficient of 0.87. (4) The reservoir strata are composed of fluvial delta facies sandstones with an average porosity of 7.8% and permeability of 0.63 mD, having high pressure sensibility and a strong water-locking effect because the pore throat radius are mostly less than 1 μm. (5) There are different dynamics at various stages in the gas reservoir-forming process. The abnormal well-developed strata pressure was the main reservoir-forming force at the Early Cretaceous setting stage while the fluid expansibility became the main gas-migrating force at the uplift and denudation stage after the Early Cretaceous period. (6) Gas reservoirs with ultra-low water saturation are mainly controlled by many factors such as changes of high temperature and high pressure fields in the Late Jurassic and Early Cretaceous periods, the charging of dry gas at the highly-mature stage, and the gas escape and dissipation at the post-reservoir-forming periods. (7) Natural gas migrated and accumulated vertically in a shortcutting path to form gas reservoirs. At such areas near the source rocks, large-scale gas reservoirs were easily found with plenty of gas sources and high gas saturation; but at those far from the source rocks, relatively small-scale and mostly secondary gas reservoirs were discovered

Natural gas exploration and development in Changqing Oilfield and its prospect in the 13th Five-Year Plan

PetroChina Changqing Oilfield Company (hereinafter referred to as Changqing Oilfield) built the largest oil and gas production base of China in the Ordos Basin in 2013, achieving the yearly natural gas production of 375 × 108 m3 in 2015. For the further sustainable and stable production and quality and benefit improvement, such great achievements made in the 12th Five-Year Plan were first summarized, and the relevant favorable conditions for natural gas development were also analyzed as follows: abundant natural gas resources; increasingly mature E&P technologies; continuously improved delicacy management; and a surging demand for natural gas. Then, challenges to natural gas development were also discussed, including obvious deterioration of natural gas resources; diminished capacity of stable production of produced gasfields; increasing number of low-yield wells; and prominent supply–demand contradiction in present natural gas market. Finally, its prospect in the 13th Five-Year Plan was studied: to carry out natural gas exploration with focus on Upper Paleozoic tight gas, Lower Paleozoic carbonate rocks, and new areas and new domains, so as to achieve rapid growth of natural gas reserves and orderly replacement in exploration domains; to make rational development planning with focus on the stable production of mature gasfields; and to enhance tight gas recovery and strengthen capacity building in new areas, so as to achieve a steady rise of annual gas production in the giant gas province. It is expected that by the end of 13th Five-Year Plan period, Changqing Oilfield will achieve its annual gas production of up to 400 × 108 m3