川东地区下侏罗统凉高山组烃源岩资源潜力评价

Resource potential evaluation of source rocks in Lower Jurassic Lianggaoshan Formation,eastern Sichuan Basin

历年来,四川盆地川东地区在侏罗系凉高山组钻井中有大量油气显示并获得低产油气流,显示了凉高山组具有良好的勘探潜力。目前川东地区凉高山组油气勘探仍处于初步阶段,对其烃源岩资源潜力尚无系统的研究。通过充分利用研究区内完钻井岩心、岩屑和野外资料,开展岩石学特征、有机质丰度、有机质类型和有机质成熟度分析,对烃源岩进行资源潜力评价。研究结果表明:①凉高山组烃源岩主要发育灰色和灰黑色泥页岩,具有分布连续性稍差、层数多、单层厚度小的特点,发育层数5~27层,最大单层厚度6~33 m,总厚度在15~112 m之间;②从有机质丰度和生烃潜量来看,TOC介于0.5%~3.21%,平均1.23%;S1+S2值介于0.06~8.68 mg/g,平均2.49 mg/g,为较好—好烃源岩,在垫江—梁平—忠县—石柱一带最好,平均TOC在1.5%以上;③从干酪根镜检和岩石热解数判断有机质类型以Ⅱ2型为主,Ⅱ1型和Ⅲ型为辅;④烃源岩干酪根的镜质体反射率Ro介于0.57%~1.53%,平均1.14%,处于成熟—高成熟演化阶段。⑤总生烃强度一般在1.59×10^(8)~8.97×10^(8)m^(3)/km^(2)之间,垫江、忠县、梁平区域内构造相对较高,平均生烃强度大于4×10^(8)m^(3)/km^(2)。

Over the years,a large amount of hydrocarbon shows have been revealed by drilling targeting the Lower Jurassic Lianggaoshan Formation in eastern Sichuan Basin,and low-yield oil-gas flow was obtained,suggesting a good exploration potential.Presently,the exploration is still in the initial stage,and the resource potential of the Formation has not been systematically investigated.In order to evaluate the resource potential of source rocks,the petrologic characteristics,abundance,types and maturity of organic matter were analyzed through the core,cuttings and field data.Results show that,(1)the source rocks are mainly gray and grayish black mud shales,which are characterized by poor distribution continuity,multiple layers and small single-layer thickness;there develops 5–27 layers,with the maximum single-layer thickness of 6–33 m,and the total thickness of 15–112 m;(2)in terms of organic matter abundance and hydrocarbon generation potential,TOC is 0.5%–3.21%(avg.1.23%),and S_(1)+S_(2) is 0.06–8.68 mg/g(avg.2.49 mg/g),indicating moderate to good source rocks,and the best ones are found in the Dianjiang-Liangping-Zhongxian-Shizhu area,with TOC˃1.5%;(3)according to the microscopic examination of kerogen and the Rock-Eval pyrolysis,the type of organic matters are mainlyⅡ_(2),followed byⅡ_(1) andⅢ;(4)the vitrinite reflectance(R_(o))of kerogen ranges from 0.57%to 1.53%,with an average of 1.14%,suggesting that the source rocks are in the stage of mature to high mature evolution;and(5)the total hydrocarbon generation intensity is generally between 1.59×10^(8)m^(3)/km^(2)and 8.97×10^(8)m^(3)/km^(2),and the one in the Dianjiang,Zhongxian and Liangping areas is relatively high,with an average over 4×10^(8)m^(3)/km^(2).