鄂尔多斯盆地上古生界本溪组8^(#)煤岩煤岩气与致密砂岩气主要气藏特征对比  

Comparison of main reservoir characteristics between deep coal-rock gas of the No.8 coal seam of the Upper Paleozoic Benxi Formation and tight sand gas reservoirs,Ordos Basin

作　　者：李明瑞 史云鹤[1,3] 范立勇 戴贤铎[1,3] 荆雪媛 张沂[4] LI Mingrui;SHI Yunhe;FAN Liyong;DAI Xianduo;JING Xueyuan;ZHANG Yi(National Engineering Laboratory for Exploration and Development of Low-Permeability Oil&Gas Fields,Xi’an,Shaanxi 710018,China;Petroleum Exploration Division,Changqing Oilfield Company,PetroChina,Xi’an,Shaanxi 710018,China;Research Institute of Exploration and Development,Changqing Oilfield Company,PetroChina,Xi’an,Shaanxi 710018,China;No.1 Gas Production Plant,Changqing Oilfield Company,PetroChina,Xi’an,Shaanxi 710018,China)

机构地区：[1]低渗透油气田勘探开发国家工程实验室,陕西西安710018 [2]中国石油长庆油田公司勘探事业部,陕西西安710018 [3]中国石油长庆油田公司勘探开发研究院,陕西西安710018 [4]中国石油长庆油田公司采气一厂,陕西西安710018

出　　处：《石油与天然气地质》2024年第6期1590-1604,共15页Oil & Gas Geology

基　　金：中国石油天然气股份有限公司科技专项(2023ZZ18);中国石油长庆油田公司“揭榜挂帅”项目(2022D-JB01)。

摘　　要：鄂尔多斯盆地长庆油田在盆内煤岩气领域取得了良好的勘探进展,发现CH_4多以吸附态和游离态赋存于煤岩中,形成自生自储型煤岩气藏。针对上古生界本溪组8^(#)煤岩为代表的煤岩气藏特征进行了深入研究。结果表明:鄂尔多斯盆地自上而下发育10套煤岩,其中5^(#)和8^(#)煤岩为主力煤岩,分布稳定,厚度大。本溪组煤岩气相较于浅层煤层气表现出“高压力、高温度、高含气、高饱和、高游离”等5高特征。气藏平均地层压力22~35 MPa,压力高但压力系数为1.0~1.1,为正常压力系统。气藏平均地层温度为67~92℃,地温梯度为29.4℃/km,属于正常地温梯度。气体组分中CH_(4)含量平均值为96.92%,C_(2)H_(6)含量平均值为0.61%,CO_(2)含量平均值为0.85%,N_(2)含量平均值为1.47%,为干气气藏。气藏地层水矿化度为41644~89776 mg/L,平均值为62228 mg/L,为CaCl_(2)型原生地层水,未受浅层水的影响。煤岩气试气产量高,生产阶段控压生产情况下产量稳定、压降速率低、稳产效果好。通过对煤岩气与苏里格气区石盒子组8段与山西组1段内致密砂岩气的系统性对比分析,发现两者在气藏类型、气藏压力和温度、气体成分、地层水性质及产能特征等主要气藏特征方面具有相似性,这个规律对后期煤岩气的大规模开发和建产具有指导意义。The Changqing Oilfield Company of PetroChina has achieved significant advances in exploring deep coal-rock gas within the Ordos Basin,discovering that methane(CH_(4))largely occurs in coals as both adsorbed and free gas,which contributes to the formation of self-sourced coal-rock gas reservoirs.In this study,we comprehensively investigate the characteristics of coal-rock gas reservoirs represented by the No.8 coal seam of the Benxi Formation.The results indicate that the Ordos Basin contains 10 coal seams from top to bottom.The Nos.5 and 8 coal seams,among others,predominate,exhibiting stable distribution and great thickness.Compared to shallow coalbed methane(CBM),the deep coal-rock gas occurring in the No.8 coal seam of the Paleozoic Benxi Formation is characterized by high formation pressure,high formation temperature,high gas content,high gas saturation,and high free gas content.Specifically,these coal-rock gas reservoirs exhibit average formation pressure ranging from 22 to 35 MPa,suggesting high formation pressure.However,their formation pressure coefficients vary between 1.0 and 1.1,indicating a normal pressure system.The coal-rock gas reservoirs present average formation temperatures ranging from 67 to 92℃and an average geothermal gradient of 2.94℃/km,suggesting normal geothermal gradients.The composition of coal-rock gas in these reservoirs manifests an average CH_(4) content of 96.92%,average C_(2)H_(6) content of 0.61%,average CO_(2) content of 0.85%,and average N_(2) content of 1.47%,establishing these reservoirs of dry gas type.The formation water in these reservoirs has total dissolved solids(TDS)concentrations ranging from 41644 to 89776 mg/L(average:62228 mg/L),indicating primary CaCl_(2)-rich formation water.Unaffected by shallow groundwater,the coal-rock gas reservoirs exhibited high gas production rates in tests and stable production at a low pressure drop rate.A systematic comparison between deep coal-rock gas reservoirs in the No.8 coal seam of the Benxi Formation and tight-sand gas reser

关 键 词：气藏特征 致密砂岩气 煤岩气 煤岩 本溪组 鄂尔多斯盆地 

分 类 号：TE122.3[石油与天然气工程—油气勘探]