鄂尔多斯盆地东缘临兴区块煤系叠置含气系统及其兼容性

Superimposing gas-bearing system in coal measures and its compatibility in Linxing block,east Ordos Basin

叠置含气系统及其兼容性是煤系多类型非常规天然气合采可行性判识基础。基于临兴区块地层压力、天然气地球化学及生产数据解译,划分了叠置独立含气系统,探讨了含气系统间兼容性。基于地层压力梯度差异认为目标层段至少存在7套独立含气系统;基于产层的天然气甲烷同位素差异,认为太2段、山2~山1段、盒8~盒6段、盒3段等4套层系互不连通;基于天然气生产曲线差异,识别出山西组与石盒子组为2套独立含气系统。综合将研究区自上而下划分为千1~千4段、千5段、盒1~4段、盒5~8段、山1~太1段、太1~太2、本1段及本2段等独立含气系统。提取了地层压力梯度、气层厚度、渗透率及可动水量等影响合采兼容性关键因素,采用最优分割分类方法,指出研究区含气系统兼容性最佳分类数为5~6类,千5段、盒1~4段、盒5~8段等3套叠置含气系统合采兼容性较好。

Superimposing gas-bearing systems and their compatibility are the key to commingling production of multitype unconventional natural gas from coal measures.Based on the pressure,geochemistry of natural gas and production data of the Linxing block,the independent gas-bearing system was divided,and their compatibility for comingling production was investigated.Based on the differences of reservoir pressure gradient,there are at least seven sets of independent pressure systems in the target coal measure.Based on the properties of methane isotopes of natural gas from the actual production seams,three sets of combined production layers,including Tai2 to Shan2 members,He8 to He6 members,He3 member,are not connected. Based on the differences of natural gas production curve,the Shanxi and Shihezi Groups are apparently two independent gas-bearing systems. In summary,there are at least eight independent gas systems,including Qian1-Qian4 member,Qian5 member,He1-He4 member,He5 to H8 member,Shan1 to Tai1 member,Tai1-Tai2 member,Ben1 member and Ben2 member.The key factors that affect the compatibility of comming-ling production from independent gas-bearing systems,such as formation pressure gradient,the thickness of the gasbearing layer,permeability,and movable water content,were extracted. Optimal partitioning method was adopted to classify the compatibility of comingling production from the different gas-bearing system in the target block. The best classification of gas-bearing system compatibility in the study area is 5-6,and the gas-bearing system compatibility of Qian5,He1-4,and He5-8 are better than those of other systems.