淮南潘谢矿区深部煤系烃源岩地球化学特征与成烃潜力

Geochemical characteristics and hydrocarbon-generation potential of coal-bearing source rocks in the deep part of Panxie mining area,Huainan

为了查明淮南煤田潘谢矿区深部煤系的烃源岩生烃潜力,在对煤系烃源岩系统采样的基础上,应用总有机碳含量、氯仿沥青"A"、岩石热解、干酪根碳同位素、镜质组反射率等有机地球化学测试方法,结合深部煤炭勘查成果,深入探讨了淮南潘谢矿区深部煤系烃源岩地球化学特征、热演化及生烃组合特征。地球化学测试结果表明:潘谢矿区深部煤系有机质干酪根主要来源于陆生高等植物,类型属于Ⅱ2-Ⅲ型,局部存在少量的Ⅱ1型,具有良好的天然气生成潜力;上石盒子组、下石盒子组和山西组泥页岩TOC含量均达到了中等烃源岩标准,氯仿沥青"A"也均达到了好的烃源岩标准,上石盒子组和山西组泥页岩S1+S2达到了中等烃源岩标准,下石盒子组泥页岩S1+S2达到了好的烃源岩标准,因此泥页岩有机质丰度各项指标均达到了中等或者好的烃源岩标准,加上煤层总有机碳含量均在60%以上,表明潘谢矿区深部煤系有机质具有较高的原始生烃能力。在潘气1井煤系烃源岩有机地化和气测录井特征分析的基础上,结合深部煤炭勘查成果,以全区稳定发育的厚层煤层和泥页岩为目标层位,在潘谢矿区深部划分了3套稳定发育的生烃组合。组合1位于上石盒子组上段中-下部,厚40~60 m,是良好的页岩气-煤层气共生气藏;组合2位于下石盒子组上段,厚60~150 m,以煤层气为主,页岩气为辅;组合3位于山西组底部,厚20~35 m,以煤层气为主,页岩气为辅。

In order to ascertain the hydrocarbon generation potential of the deep part of Panxie mining area in Huainan coalfield,on the basis of sampling the source rocks of coal measures,some organic geochemical methods such as total organic carbon content(TOC),chloroform bitumen "A",rock pyrolysis,kerogen carbon isotope and vitrinite reflectance were used,combined with the achievements of deep coal exploration,to investigate the geochemical characteristics,thermal evolution and hydrocarbon generation combination characteristics of coal-bearing source rocks in the deep part of Huainan mining area.The geochemical test results show that the organic kerogen in coal measures belongs to type Ⅱ2-Ⅲ,with a small amount of type Ⅱ1,and has a good potential for gas generation.The TOCs of shale in Upper Shihezi Formation,Lower Shihezi Formation and Shanxi Formation all meet the standard of medium hydrocarbon source rocks,the chloroform asphalt "A" also meets the standard of good hy-drocarbon source rocks,the S1+S2 of shale in Upper Shihezi Formation and Shanxi Formation meets the standard of medium hydrocarbon source rocks,and the S1+S2 of shale in Lower Shihezi Formation meets the standard of good hydrocarbon source rocks.Therefore,all indexes of organic matter abundance in shale have reached the standard of medium or good hydrocarbon source rocks,and the total organic carbon content in coal seam is above 60%,which indicates that the organic matter in deep coal measures in Panxie mining area has high primary hydrocarbon generation ability.Based on the analysis of organic geochemistry and gas logging characteristics of coal-bearing source rocks in PQ-1 well,combining with the borehole columnar of deep coal exploration,and taking the thick coal seam and shale as the target horizon,three sets of stable hydrocarbon-generating combinations were divided in the deep part of Panxie mining area.Combination 1 is located in the middle-lower part of the upper segment of Upper Shihezi Formation,with a thickness of about 40-60 m,and is a good shale gas-coalbed methane co-generation reservoir.Combination 2 is located in the upper part of Lower Shihezi Formation,with a thickness of about 60-150 m,and dominated by coalbed methane and supplemented by shale gas.Combination 3 is located at the bottom of Shanxi Formation,with a thickness of about 20-35 m,and dominated by coalbed methane and supplemented by shale gas.