四川盆地普光和通南巴地区须家河组气藏气源探讨

Origin of natural gas in the Xujiahe Formation in Puguang and Tongnanba area, Sichuan Basin, China

张鹏伟,张洪安,王学军,彭君,周勇水,徐田武,张云献,张斌,康华

中国石化中原油田分公司勘探开发研究院，河南 濮阳 457001 中原油田博士后科研工作站，河南 郑州 450000 中国石化中原油田分公司，河南 濮阳 457001

Exploration and Development Research Institute, Zhongyuan Oilfield Company, SINOPEC, Puyang 457001, China Post?鄄Doctoral Scientific Research Station, Zhongyuan Oilfield Company, Zhengzhou 450000, China Zhongyuan Oilfield Company, SINOPEC, Puyang 457001, China

以天然气和烃源岩的地球化学特征为主要依据，通过气藏气、烃源岩脱附气、烃源岩综合对比，深入探讨了普光和通南巴地区须家河组气藏的气源。2个地区的须家河组天然气以甲烷为主，干燥系数普遍高于0.97，为典型干气。普光地区天然气甲烷和乙烷的δ13C值分别为-36.1‰~-30.8‰，-28.9‰~-26.0‰，具有正碳同位素序列特征，表现为高—过成熟油型气和煤型气的混合气。通南巴地区天然气甲烷的δ13C值高达-25.2‰，具有煤型气的特点，乙烷的δ13C值介于-35.5‰~-28.9‰，为油型气成因，甲烷和乙烷的碳同位素发生倒转，且甲烷的δD值介于-173‰~-122‰，具有海、陆相混源的特征。气源对比研究表明：普光地区须家河组天然气主要来源于自身腐殖型和混合型干酪根，为自生自储型气藏；通南巴地区须家河组气藏具有“海、陆相双源供烃”的特点，通南巴背斜带须家河组天然气主要来源于中—下三叠统碳酸盐岩气藏以及龙潭组和龙马溪组烃源岩，通江凹陷带须四段气藏中海相油型气的比例明显降低，气源主要为须家河组烃源岩。

Origin of natural gas from the Xujiahe Formation reservoirs in Puguang and Tongnanba area in the Sichuan Basin has been studied based on geochemical characteristics of natural gas, source rock, and adsorbed gas in the source rock. Natural gas in the Xujiahe Formation in both areas is predominated by methane, with gas dryness values greater than 0.97. Gas in the Puguang area has methane δ13C values ranging from -36.1‰ to -30.8‰ and ethane δ13C values from -28.9‰ to -26.0‰, which shows a normal sequence of carbon isotopic compositions and consists of oil-and coal-type gases with an advanced degree of maturation. Gas in the Tongnanba area is also composed of coal-type gas with methane δ13C values up to -25.2‰ and oil-type gas with ethane δ13C values varying from -35.5‰ to -28.9‰. However, the carbon isotopic reversal was observed in most gas samples, and the methane is probably of mixed marine and terrestrial origin with δD values ranging from -173‰ to -122‰. We conclude that natural gas in the Xujiahe Formation in the Puguang area originates primarily from the humic-and mixed-type kerogens of itself, but the gas in the Tongnanba area has a mixed marine and terrestrial origin. The gas from the Xujiahe Formation reservoirs in the Tongnanba anticline was mainly derived from the Middle-Lower Triassic carbonate reservoirs and the Longtan and Longmaxi formations source rocks, whereas the gas in the fourth member of the Xujiahe Formation in the Tongjiang depression was mostly generated by the Xujiahe Formation source rock.  

10.6056/dkyqt202202001