徐家围子断陷沙河子组煤岩气成藏条件及突破方向  

Gas accumulation conditions and exploration orientation of coal measure gas in Shahezi Formation in Xujiaweizi Fault Depression

作　　者：孙立东[1] 杨亮[1] 许金双 刘家军[1] 李笑梅[1] 李国政[1] Sun Lidong;Yang Liang;Xu Jinshuang;Liu Jiajun;Li Xiaomei;Li Guozheng(Research Institute of Exploration&Development,PetroChina Daqing Oilfield Company)

机构地区：[1]中国石油大庆油田勘探开发研究院

出　　处：《中国石油勘探》2024年第4期71-81,共11页China Petroleum Exploration

基　　金：中国石油天然气股份有限公司科学研究与技术开发项目“松辽盆地深部含油气系统研究”(2021DJ0205);中国石油天然气股份有限公司重大科技项目“松辽盆地及外围风险勘探领域和目标研究、工程技术攻关现场试验”(2023YQX10102)。

摘　　要：为明确徐家围子断陷煤岩气勘探有利区,综合地震、岩心和地球化学等多种资料,系统分析了煤岩气成因、烃源岩类型、储层特征和储盖组合等有利成藏条件。结果表明:(1)沙河子组1号、2号煤层是形成于三角洲前缘和滨浅湖沼泽环境的稳定煤岩,煤岩厚度为3~10m,TOC平均约为29.65%,正处于高—过成熟阶段;(2)沙河子组煤层气以甲烷为主,为自生自储的高—过成熟煤型气;(3)煤岩储集空间类型多样,以张性微裂隙、原生植物组织孔、气孔和矿物质孔为主,孔隙度和渗透率分别平均为4.74%和4.42mD,是深层有利储层;(4)沙河子组顶部发育泥岩、泥质粉砂岩2种盖层和3种储盖组合,顶底泥岩型和顶泥底砂型储盖组合封闭性高,与煤层内广泛分布的超压封存箱一起,为煤岩气的保存创造了有利条件;(5)在煤层气藏地质特征研究基础上,通过生烃模拟估算研究区各生烃洼槽的资源量,并结合煤岩厚度、埋藏深度、成熟度等多种参数,优选宋站洼槽1号煤层和徐西洼槽2号煤层2个有利区,泥质盖层厚度大于5m的区域为近期煤层气勘探突破方向。In order to identify the favorable exploration area for coal measure gas in Xujiaweizi Fault Depression,seismic data,coal samples and geochemical data are used to systematically study the favorable gas accumulation conditions,including genesis of coal measure gas,source rock type,reservoir characteristics and reservoir-cap rock combination.The study results show that:(1)No.1 and No.2 coal seams in Shahezi Formation are two sets of consistent coal rocks deposited in delta-front and shallow lake swamp environments,with a thickness of 3-10 m,average TOC of 29.65%,and high to over-high maturity;(2)The coal measure gas is dominated by methane,showing a self-generation and self-storage type highly-over matured coal-generated gas;(3)There are diverse reservoir space types,which are dominated by tensile micro-fissures,primary plant tissue pores,vesicles and mineral pores,with the porosity and permeability of 4.74%and 4.42 mD,showing a favorable reservoir for coal measure gas in deep formations;(4)There are two types of cap rocks at the top Shahezi Formation,i.e.,mudstone and argillaceous siltstone,and three types of reservoir-cap rock combinations,among which the mudstone roof and floor type and mudstone roof and sandstone floor type have good sealing capacity,providing favorable preservation conditions for coal measure gas together with the widespread overpressure sealing box in the coal seam;(5)Based on the study of geological characteristics of coal measure gas reservoir,gas resources in all hydrocarbon generation sub-sags are estimated by using hydrocarbon generation simulation method,and two favorable exploration areas are optimally selected,i.e.,No.1 coal seam in Songzhan sub-sag,and No.2 coal seam in Xuxi sub-sag by integrating multiple parameters such as coal thickness,burial depth,and maturity.The area with mudstone cap rock thickness of greater than 5 m is exploration orientation in the near future for achieving breakthroughs of coal measure gas.

关 键 词：徐家围子断陷 沙河子组 煤岩气 成藏条件 突破方向 

分 类 号：TE122.2[石油与天然气工程—油气勘探]