川东地区下侏罗统自流井组东岳庙段烃源岩评价

Evaluation on source rocks of Dongyuemiao Member in the Lower Jurassic Ziliujing Formation,eastern Sichuan Basin

2020年,江汉油田在川东地区部署的下侏罗统自流井组东岳庙段水平页岩气井测试取得工业油气流,展示了东岳庙段页岩气具有巨大的勘探潜力。但对东岳庙段页岩油气勘探仍处于初步阶段,对其烃源岩尚无系统的研究。为此充分利用区内完钻井岩心、岩屑资料,开展岩石学特征和地化分析,对烃源岩进行定性评价。研究结果表明:(1)川东地区东岳庙段主要发育碳质页岩、介壳页岩和泥岩,厚度25~40 m;(2)从有机质丰度和生烃潜量来看,东岳庙段发育较好-好的烃源岩,主要分布在福禄场-大猫坪-高峰场-五百梯一带;(3)从干酪根镜检和岩石热解数判断有机质类型以Ⅱ_(1)型为主、Ⅱ_(2)型为辅;(4)油藏与凝析气藏成熟度(换算为镜质体反射率)划分界限在1.1%,凝析气藏与湿气藏界限在1.4%左右。东岳庙段烃源岩处于成熟晚期到高熟早期阶段(研究区统计样品数据中77.4%以上的镜质体反射率值大于1.1%,19.3%以上的镜质体反射率值大于1.4%),以生成凝析油气-湿气为主,因此川东地区东岳庙段应以页岩气藏为主要勘探目标。

In 2020,industrial oil and gas flow was obtained from Dongyuemiao Member in the Lower Jurassic Ziliujing Formation in one horizontal shale-gas well deployed in eastern Sichuan Basin by Sinopec Jianghan Oilfield Company,proving a great potential in shale-gas exploration.However,for the Dongyuemmiao Member,its exploration is still at the primary stage,and there is no systematic investigation on source rocks.So,the source rocks were qualitatively evaluated by means of core and cuttings data and their petrological and geochemical analysis.Results show that(1)carbonaceous shale,shell shale,and mudstone are mainly developed in the Jurassic Dongyuemiao Member,which are 25 to 40 m thick;(2)judged by organic-matter abundance and hydrocarbon-generating potential,good to better source rocks are developed in this member mainly around Fuluchang-Damaoping-Gaofengchang-Wubaiti area;(3)from microscopic examination of kerogen and rock pyrolysis,the organic-matter type is chieflyⅡ_(1) withⅡ_(2) as the supplement;and(4)the source rocks are in late maturity to early over maturity,so condensate gas and wet gas are dominately generated from them,the Ro threshold of oil and condensate gas reservoirs is 1.1%,and 1.4%for condensate gas and wet gas reservoirs,indicating shale-gas reservoirs of Dongxuemiao Member are the primary exploration targets in eastern Sichuan Basin.