琼东南盆地深水区第四系超浅层大型气藏盖层类型及封盖机理  

Caprock Type and Sealing Mechanism of Quaternary Ultra Shallow Large Gas Reservoir in Deep Water Area of Qiongdongnan Basin, China

作　　者：裴健翔 王宇 Pei Jianxiang;Wang Yu(Institute of Advanced Studies,China University of Geosciences,Wuhan 430074,China;CNOOC Hainan Branch Company,Haikou 570312,China)

机构地区：[1]中国地质大学高等研究院,湖北武汉430074 [2]中海石油(中国)有限公司海南分公司,海南海口570312

出　　处：《地球科学》2025年第1期144-157,共14页Earth Science

基　　金：中国海油南海油气能源院士工作站基金项目;海南省重点研发项目(No.ZDYF2024GXJS031)。

摘　　要：盖层是决定油气能否成藏的重要因素,目前盖层研究多关注中深层固结岩石的封盖能力,而围绕浅层疏松未固结盖层的研究较少,对于深水浅埋地层中的盖层评价则更为少见.基于琼东南盆地深水区三维地震解释、三轴应力实验、测井评价、圆锥触探试验等研究成果,明确了L36区第四系乐东组浅埋气藏盖层的发育类型及封堵能力,总结了研究区盖层封盖机理.结果表明:(1)深水区乐东组发育深海泥、块体流、含水合物地层3类盖层,三者均可起到有效封盖作用;(2)综合地震-地质解释及实验成果,明确了3类盖层封盖能力从小到大依次为深海泥、块体流、含水合物地层,其中深海泥在海底埋深200 m处可封盖59 m天然气,为研究区主要目的层盖层封堵下限.(3)深水浅埋盖层封堵机理占主导作用的是毛细管封闭、水力封闭,低温高压环境下饱和盐水封堵机制发挥了特色性增封作用.以上认识得到近两年钻探的验证,这不仅为琼东南盆地乐东组的后续勘探开发提供了理论依据,也可为其他深水浅埋地区的天然气勘探提供有益借鉴.Caprock plays an important role in determining whether hydrocarbon accumulation is available.Previous studies of caprock mainly focus on the sealing ability of medium-deep consolidated rock,while less attention is paid to the shallow unconsolidated caprock,and the evaluation of caprock of shallow buried formations in deep water area is rare.Based on the research results of seismic interpretation,uniaxial stress test,logging evaluation,and cone penetration test in the deep water area of Qiongdongnan Basin,the development type and sealing ability of the caprock for the gas reservoir of the Ledong Formation in the L36 area are studied in this paper.The results show that:(1)There are three types of caprock(deep-sea mud,mass transport deposits,and hydrate-bearing strata)in the deep water area of the Ledong Formation,which could all have the effective sealing effect.(2)Based on the seismic and geological interpretation and experimental results,it is clear that the sealing capacity increases in the order of deep-sea mud,mass transport deposits,and hydrate-bearing strata;and the deep-sea mud can seal 59 m hydrocarbon at 200 m below seafloor,which is the threshold of sealing ability for the main target layer in the study area.(3)The capillary sealing and hydraulic sealing plays a dominant role in the sealing mechanism of shallow buried caprock in the deep water area,under low temperature and high pressure environment,the saturated salt water sealing mechanism plays a characteristic role in increasing sealing capacity.The above results have been verified by drilling in the past two years,which not only provides a theoretical basis for the follow-up exploration and development of the Ledong Formation in Qiongdongnan Basin,but also can provide a useful reference for the natural gas exploration in other shallow buried areas in the deep water area.

关 键 词：琼东南盆地 深水区 第四系 超浅层气藏 盖层类型 封盖机理 石油地质学 

分 类 号：P618.13[天文地球—矿床学]