摘要
米苍山-大巴山冲断构造带南缘海相下组合具有良好的油气勘探前景,但作为新领域、新地区其勘探程度很低。根据对城口、南江地区可能烃源岩层位的系统观测、采样和有机地球化学综合剖面研究指出,下寒武统筇竹寺组中下部、上奥陶统五峰组-下志留统龙马溪组底部各发育一套黑色页岩,厚度数十米至百余米,分布稳定,有机质丰度高(TOC普遍大于1%),有机质类型属藻腐泥型,生烃潜力高(其中五峰组-龙马溪组烃源岩S1+S2高达2.86-3.65 mg/g,S2为2.66-3.36 mg/g),均是优质烃源岩;下寒武统烃源岩在本区燕山中晚期褶皱隆升、剥蚀前最大埋藏时达到了过成熟早期生干气阶段,上奥陶统-下志留统烃源岩进入了生凝析油-湿气为主的高成熟阶段,处于生气高峰期,而因埋深增加和持续埋深等原因,处在推覆体之下或毗邻凹陷腹部的现今热演化程度也许会有所升高,成为以生干气为主的气源岩。认为该2套优质海相烃源岩的存在,可为川东地区尤其是南江、镇巴-万源地区下组合的油气生成、成藏提供雄厚的物质基础。
There is good prospect for nature gas in the north of the upper-Yangtze area, but there exists complex geological conditions and low degree of exploration. Potential source rocks in the Chengkou and Nanjiang sections are investigated on their organic geochemistry, petrology, carbon isotope composition and thermal evolution etc, and are showed in compositive vertical sections. Two series of high-quality source rocks are discovered including lower Cambrian and upper Ordovician-lower Silurian black shale. They all have characteristics as follows： ①good organic types（sapropel type）, high abundance of organic materials （TOC≥1.0%） and hydrocarbon potentials （S1＋S2 are 2. 86～3. 65 mg/g, S2 is 2. 66～3. 36 mg/g）; ②large thicknees and extensive distribution; ③a mass of oil（bitumen） and gas show. The thermal evolution degree of source rock in lower Cambrian has came to over-mature stage at late Jurassic-cretaceous, and the upper Ordovician-lower Silurian has came to the late stage of high-mature that is the period of peak gas generation. That these high quality source rocks contribute main organic material basis for the early deposits, and the formation of gas traps in the late stage.
出处
《天然气地球科学》
EI
CAS
CSCD
2007年第2期254-259,共6页
Natural Gas Geoscience
基金
国家重点基础研究发展规划"973"项目(编号:2005CB422102)
中国石化股份公司科技项目(编号:P04040)联合资助
关键词
优质烃源岩
生烃潜力
热演化史
上扬子北缘下组合
High-quality source rock
Hydrocarbon potential
Thermal evolution history
Lower combination in the North upper-Yangtze area.
