石柱地区建深1井志留系超压顶封层的封闭机制  

Sealing Mechanism of Overpressured Top Seal in Well Jianshen 1 Silurian Formation of Shizhu Synclinorium

作　　者：杨兴业[1] 何生[1] 何治亮[2] 李天义 王芙蓉[1] 

机构地区：[1]中国地质大学构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国石油化工股份有限公司石油勘探开发研究院,北京100083

出　　处：《地球科学（中国地质大学学报）》2014年第1期64-72,共9页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学重点基金项目(No.40739904);国家科技重大专项(No.2011ZX05005-002);国家自然科学基金面上项目(No41072093)

摘　　要：石柱复向斜地区建深1井志留系地层钻遇超压,压力系数为1.75-2.00,且全层段含气.地层中超压形成和保存与盖层封闭的有效性密切相关.在对超压层段泥岩压实特征以及埋藏史、热史、生烃史研究的基础上分析欠压实、生烃、构造挤压及其他增压机制在志留系超压形成所起的作用,其中早三叠世至侏罗纪末期干酪根和液态烃裂解生气作用引起的流体体积膨胀是本区超压形成的主控因素,生气作用终止后无重要的增压事件发生.早白垩世以来的构造抬升作用导致大量溶解态天然气从地层水中出溶,并聚集于孔喉半径较大的粉砂岩层中.志留系顶部超压顶封层中泥岩和粉砂岩频繁出现互层,因而形成多个含气粉砂岩薄层.垂向上各个气水界面的毛细管作用力具有可叠加性,增强了顶封层对超压的封闭能力,使本区志留系地层中的超压保存至今.The drilling of Well Jianshen 1located in Shizhu synclinorium meets overpressure and gas zone in Silurian strata,with pressure coefficients ranging from 1.75to 2.00.Overpressure generation and preservation are closely related to the sealing efficiency of cap rock.Disequilibrium compaction,hydrocarbon generation,horizontal tectonic compaction and other overpres-sure generation mechanisms for Silurian abnormal high pressure are analyzed based on mudstone compaction characteristics,tectonic subsidence history,sediment burial history,hydrocarbon generation history,and it is found out that gas generation by kerogen and petroleum cracking during Early Triassic to Late Jurassic is the controlling mechanism for overpressure.Tectonic uplift since Early Cretaceous led to the separation of plenty of gas from gas-saturated formation water and the gathering into the relatively coarse-grained siltstone.Interbedded mudstone and siltstone appear frequently in pressure transition zone at the top of Silurian formation,resulting in several thin layers of gas.Vertical capillary force in each gas-water interface is superimposed and increases cap rock sealing ability,where the abnormally high pressure has been effectively preserved to date.

关 键 词：石柱复向斜 超压成因 超压封闭 构造 油气 

分 类 号：P618[天文地球—矿床学]