吐哈盆地台北凹陷水西沟群煤系烃源岩沉积有机相研究

Study on sedimentary organic facies of coal-measure source rocks in Shuixigou Group, Taibei Sag, Tuha Basin

梁浩 范谭广 王志勇 陶树 文艺洁 郑海天 张子建

LIANG Hao FAN Tanguang WANG Zhiyong TAO Shu WEN Yijie ZHENG Haitian ZHANG Zijian

1. 中国石油 吐哈油田分公司, 新疆 哈密 839009; 2. 中国地质大学(北京) 能源学院, 北京 100083

1. PetroChina Tuha Oilfield Company, Hami, Xinjiang 839009, China; 2. School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China

吐哈盆地台北凹陷蕴含丰富的油气资源，侏罗系水西沟群煤系烃源岩作为区内主力烃源岩发育层位，生烃潜力巨大。然而对于水西沟群煤系烃源岩有机相类型及其与沉积环境的对应关系尚无明确定论，制约了整个凹陷乃至盆地范围油气资源勘探部署。为实现吐哈盆地水西沟群煤系烃源岩的精细划分与评价，基于显微组分、总有机碳(TOC)含量、生烃潜量(S1+S2)等地球化学测试结果，建立了研究区煤系烃源岩沉积有机相划分标准，明确了有机相类型、生烃潜力及其与沉积相的对应关系。研究表明，台北凹陷水西沟群煤系烃源岩沉积有机相类型分为五类，即湖相强覆水高镜质组有机相、湖相覆水中高镜质组有机相、三角洲平原覆水中高镜质组有机相、三角洲平原弱覆水中镜质组有机相和三角洲前缘弱覆水低镜质组有机相。湖相强覆水高镜质组有机质丰度高且生烃潜力最强，TOC含量为5.05%～18.31%，S1+S2为6.35～20.93 mg/g，镜质组含量大于80%；其次为湖相覆水中高镜质组有机相和三角洲平原覆水中高镜质组有机相，二者TOC含量分别为3.83%～17.68%和2.30%～7.41%，S1+S2平均分别为6.35 mg/g和4.48 mg/g，镜质组含量均介于50%～80%；三角洲前缘弱覆水低镜质组有机相的生烃潜力最差，TOC含量平均仅为1.3%，S1+S2平均为4.1 mg/g。研究成果为预测台北凹陷水西沟群煤系优质烃源岩分布并准确评价其油气资源潜力提供了重要依据。

The Taibei Sag in the Tuha Basin contains abundant oil and gas resources. The coal-measure source rocks in the Jurassic Shuixigou Group are the main hydrocarbon source layers in the area, with significant hydrocarbon generation potential. However, organic facies types of the coal-measure source rocks in the Shuixigou Group and their relationships with sedimentary environments remain unclear, hindering oil and gas exploration across the sag and the entire basin. To enable a detailed classification and evaluation of coal-measure source rocks in the Shuixigou Group of the Tuha Basin, geochemical analyses were conducted, including maceral composition, total organic carbon (TOC) content, and hydrocarbon generation potential (S1+S2). Based on the result, the study established classification criteria for sedimentary organic facies of coal-measure source rocks in the study area, identified organic facies types, and clarified hydrocarbon generation potential and their relationships with sedimentary facies. The results indicate that the sedimentary organic facies of the coal-measure source rocks in the Shuixigou Group of the Taibei Sag can be categorized into five types: organic facies of lacustrine with strong water coverage and high vitrinites, organic facies of lacustrine with water coverage and medium to high vitrinites, organic facies of delta plain with water coverage and medium to high vitrinites, organic facies of delta plain with weak water coverage and medium vitrinites, and organic facies of front delta with weak water coverage and low vitrinites. The organic facies of lacustrine with strong water coverage and high vitrinites have a large organic abundance and exhibit the highest hydrocarbon potential, with TOC contents ranging from 5.05 % to 18.31 % and S1+S2 values from 6.35 to 20.93 mg/g, and vitrinites exceeding 80%. Following this, the organic facies of lacustrine with water coverage and medium to high vitrinites and the organic facies of delta plain with water coverage and medium to high vitrinites exhibit TOC contents of 3.83%-17.68% and 2.30%-7.41%, with average S1+S2 values of 6.35 mg/g and 4.48 mg/g, and vitrinites ranging between 50%-80%, respectively. The organic facies of front delta with weak water coverage and low vitrinites show the poorest hydrocarbon generation potential, with an average TOC content of only 1.3% and an average S1+S2 of 4.1 mg/g. The findings provide a critical basis for predicting the distribution of coal-measure high-quality source rocks in the Shuixigou Group in the Taibei Sag and for accurately assessing their oil and gas resource potential.

中国石油前瞻性基础性战略性技术攻关项目(2022DJ2107)资助。

https://doi.org/10.11781/sysydz2025010184