川西坳陷须五段页岩气藏地震各向异性  

Seismic anisotropy of shale gas reservoirs in the 5^(th) member of the Xujiahe Formation in western depression of Sichuan Basin

作　　者：徐天吉[1,2] 闫丽丽[3] 程冰洁[4] 唐建明[2,5] 李曙光[1,2] 杨振武[1,2] 

机构地区：[1]中国石化西南油气分公司勘探开发研究院物探三所,四川成都610041 [2]中国石化多波地震技术重点实验室,四川成都610041 [3]成都理工大学地球科学学院,四川成都610059 [4]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [5]中国石化西南油气分公司,四川成都610041

出　　处：《石油与天然气地质》2015年第2期319-329,共11页Oil & Gas Geology

基　　金：国家自然科学基金青年科学基金项目(41204071);国家自然科学基金联合基金项目(U1262206);国家高技术研究发展计划("863"计划)项目(2013AA064201)

摘　　要：川西坳陷须(须家河组)五段天然气资源量巨大,具有良好的勘探开发远景;但地质认识程度低,尤其针对气藏各向异性的研究极少。为了提高储层预测精度和井位部署成功率,针对须五段开展各向异性研究,有利于进一步认识须五段储层特征并深入分析天然气聚集规律。通过早期研究发现,受四川盆地须五时期的沉积环境控制,川西坳陷须五段形成了以厚泥页岩和薄致密砂岩为主体的岩性组合,页岩层横向变化大,加之页岩矿物成分、碎屑颗粒定向排列、周期性薄层沉积及其他非均质特性,导致了地层展现出各向异性特征。目前,分析预测地层空间各向异性的有效方法并不多,且大多数方法仍然以地震数据为基础:通过分析地震反射及分方位地震属性对岩石类型、物理性质及构造形态等特征的直观响应,实现岩层各向异性指示信息的准确提取。相比较而言,如果不采用分方位地震数据,而仅基于全方位叠加地震数据的各向同性分析方法,则忽视了页岩的各向异性本质,不利于地质问题的准确认识。文中采用上述方法思路,基于分方位与全方位叠加地震数据,对比分析了这两类数据的地震反射响应特征、曲率体属性、相干体属性和储层阻抗等参数,并在地震各向异性信息的指示下捕捉岩层空间变化特征,成功地实现了川西须五段气藏沉积相、岩性、裂缝的精细解释和"甜点"储层的高精度预测。The huge gas potential in the 5 th member of the Xujiahe Formation has made it one of the hottest exploration targets in China .However ,the formation has not been well explored and many geological “mysteries” remained unsolved-anisotropy of the gas reservoirs there is one of them .A research was carried out on the anisotropy to better understand the reservoirs features and accumulation patterns , so as to improve the precision of reservoir prediction and success rate of well drilling .Previous study shows that the member had been controlled by sedimentary environment and formed lithologic assemblage dominated by thick mudstone and shale and thin tight sandstone .Looking horizontally ,the shale varies drama-tically and shows strong anisotropy due to complicated mineral combination ,directional alignment of detrital grains ,cyclic veneer and other heterogeneous features .There have had no effective method for analyzing and predicting the anisotropy so far.Available methods are mostly based on seismic data to obtain anisotropy information of rocks through analyses of seismic reflection and the direct responses of azimuth attributes upon rock types ,physical features and structure configura-tions.Comparatively speaking ,anisotropy feature of shale formations is likely to be ignored by isotropy analyses based solely on stacked wide-azimuth seismic data .By combining both the azimuth and wide-azimuth stacked seismic data ,we compared and analyzed the seismic reflection responses ,curvature attributes ,coherence attributes and impedances of the＆nbsp;two sets of data ,and then captured features of reservoir space under the guidance of the anisotropy information .A fine in-terpretation of sedimentary facies ,lithology and fracture of the reservoirs and an accurate prediction of sweet spots in the member were then achieved by applying the above-mentioned method and data yield from it .

关 键 词：各向同性 各向异性 全方位 分方位 页岩气 须家河组五段 川西坳陷 

分 类 号：P315.2[天文地球—地震学]