中国中上元古界页岩气地质特征及有利区预测

Geological Characteristics and Prospective Zone Prediction of Meso- Epiproterozoic Shale Gas in China

作为中国沉积最早的地层,中、上元古界页岩气发育的地质条件和资源分布值得重视。通过文献调研、野外地质研究和实验分析相结合的手段,对页岩的分布、厚度和地球化学等特征及页岩气有利区进行了系统的分析。中、上元古界页岩主要分布在中上扬子地区的陡山沱组和燕山地区的洪水庄、下马岭组等地层中;沉积环境为大陆架和局限海相盆地内,分布相对稳定,沉积连续,厚度从20 m到150 m不等。页岩的地球化学指标较好,有机质类型以腐泥型为主,有机质丰度受控于沉积环境,TOC>2%的地层普遍发育。扬子地区中、上元古界页岩达到高—过成熟阶段,华北北部地区和建昌盆地略低,目前仍处于生烃高峰期。从页岩气聚集的地质条件上看,中国中、上元古界页岩气具有一定的资源潜力,湘鄂西和渝东南地区的陡山沱组、华北北部地区和建昌盆地的洪水庄组是页岩气发育较好的地区和层段,其勘探前景值得关注。

The geologic condition and resource distribution of shale gas developed in Meso- Epiproterozoic,the earliest deposited strata in China,are worthy of paying more attention. In this paper,by means of literature investigation,field geologic study and experimental analysis,systematic analysis was conducted on the distribution,thickness and geochemical characteristic of shale and the favorable shale gas provinces. Meso- Epiproterozoic shale is mainly distributed in the strata like Doushantuo Formation in Middle-Upper Yangtze region and Hongshuizhuang Formation and Xiamaling Formation in Yanshan region; the depositional settingsinclude continental shelf and restricted sea basin,with relatively stable distribution,continuous deposition and thickness ranging from 20 m to 150 m. The geochemical indicators of shale are good,the type of organic matter isdominated by sapropelic,the organic matter abundance iscontrolled by depositional setting,and the strata with TOC > 2% were universally developed. The Meso- Epiproterozoic shale has come to high- over mature stage in the Yangtze region,but is slightly lower in Northern Huabei and in the Jianchang Basin,and is still at hydrocarbon generation peak for the moment. Observed from the geologic conditions of shale gas accumulation,the Meso- Epiproterozoic shale gas has some resource potentials in China. The Doushantuo Formation in western Hunan and Hubei provinces and southeastern Chongqing city as well as the Hongshuizhuang Formation in Northern Huabei and the Jianchang Basin are the regions and intervals with better development of shale gas,whose exploration prospectsare worthy of attention.