四川盆地西部中三叠统雷口坡组烃源岩生烃潜力分析

Hydrocarbon potential of source rocks in the Middle Triassic Leikoupo Formation in the Western Sichuan Depression

杨克明

Yang Keming

中国石化 西南油气分公司, 成都 610016

SINOPEC Southwest Branch Company, Chengdu, Sichuan 610016, China

中三叠统雷口坡组是近年来四川盆地海相天然气勘探的重要层系之一。通过对川西地区雷口坡组钻井样品的有机地球化学分析,结合地震解释资料及沉积相资料,推测雷口坡组烃源岩主要分布在大邑-温江-彭州-广汉及孝泉地区,烃源岩厚度达250~350 m,有机碳含量为0.4%~0.6%。川西雷口坡组烃源岩形成于生物生产力较高、水动力较弱、海水循环受限、盐度较高、沉积物-水界面附近缺氧和沉积速率较低的沉积环境,有利于烃源岩有机质的保存。川西地区雷口坡组烃源岩有机、无机地球化学和有机岩石学综合分析表明,该烃源岩虽然有机质丰度较低,但类型较好;烃源岩有机质显微组分中常见固体沥青和超微组分,有机质类型指数TI为12.5%~98.03%,主要为Ⅱ1-Ⅱ2型烃源岩,有机质主要来源于水生浮游生物,具有较好的生烃潜力。

The Middle Triassic Leikoupo Formation in the Western Sichuan Depression is an important marine target for natural gas exploration in the Sichuan Basin in recent years. Geochemical analyses were made with rock samples from the Leikoupo Formation. Seismic interpretation and sedimentary data were studied. Source rocks in the Leikoupo Formation mainly distribute in Dayi, Wenjiang, Pengzhou, Guanghan and Xiaoquan. They are about 250-350 m thick, and have a TOC content of 0.4%-0.6%. The source rocks were deposited in a sedimentary environment with high biological productivity, quiescent depositional setting, restricted seawater circulation, high salinity, anoxic bottom water and low deposition rate, all favorable for the preservation of organic matter. The comprehensive analyses of organic geochemistry, inorganic geochemistry and organic petrology indicated that, the source rocks in the Leikoupo Formation displayed a low abundance of organic matter with good organic type. Solid bitumen and ultramicro macerals were observed on photomicrographs. Organic type index (TI) ranges from 12.5%-98.03%, indicating Type Ⅱ1-Ⅱ2 source rocks. Organic matter was mainly derived from hydroplankton, showing a good hydrocarbon potential.

中国地质调查局项目"四川盆地及周缘碳酸盐岩油气地质调查及战略选区(带)评价"(1212011220758)资助。

https://doi.org/10.11781/sysydz201603366