鄂尔多斯盆地杭锦旗地区上古生界原油成因及勘探前景

Origin and exploration prospect of Upper Paleozoic crude oil from Hangjinqi area, Ordos Basin

赵永强 许锦 倪春华 张毅 马中良 王付斌 贾会冲 张威 齐荣 安川

ZHAO Yongqiang XU Jin NI Chunhua ZHANG Yi MA Zhongliang WANG Fubin JIA Huichong ZHANG Wei QI Rong AN Chuan

中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126 中国石化油气成藏重点实验室, 江苏 无锡 214126 页岩油气富集机理与有效开发国家重点实验室, 江苏 无锡 214126 中国石化 华北油气分公司 油气勘探管理部, 郑州 450006 中国石化 华北油气分公司 勘探开发研究院, 郑州 450006

Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China SINOPEC Key Laboratory of Petroleum Accumulation Mechanisms, Wuxi, Jiangsu 214126, China State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Wuxi, Jiangsu 214126, China Department of Oil and Gas Exploration Management, SINOPEC North China Branch, Zhengzhou, Henan 450006, China Research Institute of Exploration and Development, SINOPEC North China Branch, Zhengzhou, Henan 450006, China

鄂尔多斯盆地杭锦旗地区上古生界海陆过渡相有一套良好的生储盖组合，目前已发现了东胜大气田。该区二叠系下石盒子组产出少量中质原油，但原油的成因及其勘探前景尚不明确。基于对该区原油的物性、饱和烃色谱、生物标志物及碳同位素等地化特征的研究，试图揭示原油的成因和勘探前景。杭锦旗地区上古生界原油具有低硫、高蜡、中等成熟度特征，其甾烷分布显示以陆生植物为主，少量水生生物；Pr/Ph值为2.16~2.26，重排甾烷和重排藿烷含量高，伽马蜡烷含量低，原油碳同位素值为-27.7‰~-26.8‰，正构烷烃单体烃碳同位素前重后轻，这些特征均指示该原油是由沉积环境为弱氧化的陆相煤系地层中的暗色泥岩生成。二叠系山西组烃源岩有机岩石学、生烃热模拟实验及岩石热解等综合分析表明，该区山西组暗色泥岩具有一定生油潜力。结合原油产出井的位置和烃源岩的空间展布，山西组暗色泥岩可能是潜在的烃源岩。杭锦旗地区上古生界良好的生储盖组合条件暗示着该区的原油勘探值得重视，泊尔江海子断裂两侧邻区是原油聚集的潜在有利区。

A set of favorable source-reservoir-caprock assemblage was found in the Upper Paleozoic transitional facies in the Hangjinqi area of the Ordos Basin, and the large-scale Dongsheng gas field has been discovered. A small amount of crude oil has been produced from the Lower Shihezi Formation reservoir in the area; however, the origin and exploration prospect of the oil are unclear. Based on the studies including physical property, n-alkanes distributions, biomarker compositions, and carbon isotopic ratios, the origin and exploration prospect of the crude oil has been discussed. Results indicate that the Upper Paleozoic crude oil from the Hangjinqi area is mature oil with a low sulfur content and a high wax content, and the steranes are dominated by terrestrial plants and assisted by a small amount of aquatic organism. The Pr/Ph ratio is 2.16-2.26, and the diasteranes and rearranged hopanes are in high contents with a relative low content of gammacerane. The carbon isotopic ratios of the oil range from -27.7‰ to -26.8‰, [JP+1]and the carbon isotopic[JP]compositions of individual n-alkanes are heavy at first and then become light with the increasing of carbon numbers. These characteristics suggest that the oil was generated by the dark mudstone in terrigenous coal measures under weak oxidation environment. The comprehensive analysis combining organic petrography, hydrocarbon generation simulation, and pyrolysis of source rocks in the Shanxi Formation indicates that, the dark mudstone in the Permian Shanxi Formation in the Hangjinqi area displays a certain amount of oil generation potential. In combination with the location of oil producing wells and the spatial distribution of source rocks, the dark mudstone in the Shanxi Formation might be the potential source rocks for the produced oil. The oil exploration of the Upper Paleozoic strata in the Hangjinqi area deserves attention as suggested by the favorable conditions of source-reservoir-caprock assemblage, and the adjacent areas of the Borjianghaizi fault are potential favorable areas for oil accumulation.

国家科技重大专项 2016ZX05002-006

https://doi.org/10.11781/sysydz202203487