摘要
四川盆地东部(以下简称川东地区)中二叠统茅口组后期沉积相变过程复杂,加之茅口组顶界尚缺乏统一的划分标准,由此导致所恢复的茅口组岩溶古地貌格局与实际情况之间存在着较大的差异。为了给该区茅口组岩溶储层的天然气勘探提供帮助,利用露头地质调查、钻井岩心、测井及地震人工虚拟井等资料,在通过标志层对茅口组进行精细划分和对比的基础上,综合地层残余厚度、地层岩性、地层剥蚀层段分析,建立了茅口组古岩溶地貌单元划分标准,刻画出岩溶高地、岩溶斜坡和岩溶盆地的分布格局。研究结果表明:①该区茅口组残余地层厚度具有“北薄南厚”的分布特征,其中茅一段厚度分布稳定,茅二段残余地层厚度变化较大;②海槽相孤峰段开始沉积于茅二^(b)期,结束于茅二^(a)晚期,地层厚度一般小于25 m,分布局限于川东北地区;③茅三段和茅四段在川东地区的中部和北部均遭到不同程度的剥蚀;④茅口组末期古地貌可划分出2个岩溶高地、3个岩溶盆地及2个岩溶斜坡。结论认为,川东地区茅口组古地貌总体上呈岩溶斜坡为主、岩溶高地次之,岩溶盆地分布范围相对较小,其中北部和中部地区岩溶高地、岩溶斜坡带茅口组上部地层剥蚀较多,岩溶储层主要发育于茅二^(b)亚段、茅二^(c)亚段及茅一段中上部,南部地区岩溶储层主要发育于茅三段、茅二^(a)亚段及茅二^(b)亚段。
The Middle Permian Maokou Formation in the eastern Sichuan Basin experienced complex sedimentary facies change in the late stage,and there is no unified division standard of the top and bottom boundaries of Maokou Formation,so the restored karst palaeogeomorphological pattern of Maokou Formation is much different from the actual situation.In order to provide support for the natural gas exploration in the Maokou Formation karst reservoirs of this area,this paper,through precise division and correlation of the Maokou Formation referring to the marker bed,using the data of outcrop geological survey,drilling core,logging and seismic artificial virtual wells,based on the analysis of residual formation thickness,formation lithology and denuded formation interval,aims to establish a division standard of the Maokou Formation karst palaeogeomorphological unit,and describe the distribution pattern of karst highlands,karst slopes and karst basins.And the following research results are obtained.First,the residual formation thickness of Maokou Formation presents the distribution characteristics of"thin in the north and thick in the south".The thickness of the first Member of Maokou Formation(P_(2)m^(1))is stable while the residual formation thickness of the second Member of Maokou Formation(P_(2)m^(2))varies greatly.Second,the sedimentation of the Gufeng Member of trough facies begins in the P_(2)m^(2)b stage and ends in the late P_(2)m^(2)a stage.Its formation thickness is generally less than 25 m and its distribution is limited in the northeastern Sichuan Basin.Third,the 3^(rd)and 4^(th)Members of Maokou Formation(P_(2)m^(3)and P2m4)are denuded to different degrees in the central and northern part of eastern Sichuan Basin.Fourth,the palaeogeomorphology at the end of Maokou Formation can be divided into two karst highlands,three karst basins and two karst slopes.In conclusion,the Maokou Formation in the eastern Sichuan Basin is palaeogeomorphologically characterized by primary karst slopes,secondary karst highlands and smaller karst basins.In the northern and central part,the upper zone of Maokou Formation in the karst highlands and karst slopes is more denuded,and karst reservoirs are mainly developed in the P_(2)m^(2)b,the P_(2)m^(2)c and the middle and upper zones of P_(2)m^(1);while in the southern part,karst reservoirs are mainly developed in the P_(2)m^(3),P_(2)m^(2)a and P_(2)m^(2)b.
作者
陈卫东
陈义才
徐发波
李世临
李延钧
曾丽媛
谭谦
康宇
CHEN Weidong;CHEN Yicai;XU Fabo;LI Shilin;LI Yanjun;ZENG Liyuan;TAN Qian;KANG Yu(Chongqing Division,PetroChina Southwest Oil&Gasfield Company,Chongqing 400021,China;Chengdu University of Technology,Chengdu,Sichuan 610059,China;Chengdu ChuangYuan Oil and Gas Technology Development Co.,Ltd.,Chengdu,Sichuan 610500,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2021年第6期27-36,共10页
Natural Gas Industry
基金
中国石油西南油气田公司重大专项“川东地区中—浅层油气综合地质及有利目标评价研究”(编号:XNS02JS2018-0157)。
关键词
四川盆地东部
中二叠统茅口组
孤峰段
地层划分与对比
岩溶古地貌
Eastern Sichuan Basin
Middle Permian Maokou Formation
Gufeng Member
Stratigraphic division and correlation
Karst palaeogeomorphology
