The geochemical feature and evolutionary history of hydrocarbons from the deep Cretaceous Bashijiqike (K1bs) Formation tight sandstone reservoir in the Dabei Gas Field, Kuqa Depression were investigated using gas chromatography, gas chromatography–mass spectrometry, inclusions petrography and micro-thermometry, laser Raman spectroscopy, and quantitative grain fluorescence. The result indicates that natural gases from the deep sandstone reservoir are mainly composed of alkanes and belong to dry gases, of which methane accounts for 94.30–97.20% (avg. 95.64%), and ethane is 1.23–2.45% (avg. 1.95%). The stable carbon isotopic value of methane and ethane is −31.9‰ to −29.3‰ (avg. −30.3‰) and −24.2‰ to −19.4‰ (avg. −21.7‰), respectively, and this reflects the features of high-mature coal-derived gases. In addition, natural gases in the Dabei Gas Field have characteristics of coal-derived gases which were sourced from Jurassic coal measures. Oils in the Dabei Gas Field predominately originated from Triassic Huangshanjie (T3h) Formation mudstones with some contributions from Jurassic coaly rocks. Petrological and micro-thermometry results of fluid inclusions suggest that the K1bs Formation tight sandstone reservoirs have experienced two phases of hydrocarbons charge histories, namely “early oil and later gas.” The quantitative grain fluorescence analysis indicated that sandstone samples with quantitative grain fluorescence index value >5 and quantitative grain fluorescence-extraction intensity >40 pc in Wells DB101 and DB2 can be used as indicators for the paleo oil layers or the migration channels of later charged natural gas. The aforementioned analyses and burial and thermal histories of K1bs sandstone reservoir demonstrated that oil charged at 10 Ma and natural gas charged at approximately 3 Ma in the study area. Furthermore, paleo-tectonic evolution enabled source rocks to mature and expel hydrocarbons, and the structurally related faults and traps provided pathways and places for hydrocarbon migration and accumulation.

中文翻译：

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塔里木盆地库车坳陷大北气田深层致密砂岩储层烃地球化学及充注史

采用气相色谱、气相色谱-质谱、包裹体岩相学和显微测温、激光拉曼光谱等方法研究了库车坳陷大北气田深部白垩系巴什基奇克(K1bs)组致密砂岩储层烃的地球化学特征和演化历史，和定量颗粒荧光。结果表明，深部砂岩储层天然气以烷烃为主，属于干气，其中甲烷占94.30%～97.20%（平均95.64%），乙烷占1.23%～2.45%（平均1.95%） ）。甲烷和乙烷的稳定碳同位素值分别为-31.9‰～-29.3‰（平均-30.3‰）和-24.2‰～-19.4‰（平均-21.7‰），这反映了高-成熟的煤成气。此外，大北气田天然气具有煤成气特征，来源于侏罗系煤系。大北气田石油主要来源于三叠系黄山街（T3h）组泥岩，部分来自侏罗系煤岩。流体包裹体的岩石学和显微测温结果表明，K1bs组致密砂岩储层经历了“早油晚气”两个阶段的油气充注史。颗粒荧光定量分析表明，DB101、DB2井颗粒荧光定量指数值>5、颗粒荧光提取强度>40pc的砂岩样品可作为古油层或后期带电天然运移通道的指示剂。气体。上述分析和 K1bs 砂岩储层的埋藏和热史表明，研究区的石油充注量约为 10 Ma，天然气充注量约为 3 Ma。此外，古构造演化使烃源岩成熟排烃，与构造相关的断层和圈闭为油气运聚提供了通道和场所。