川东地区寒武系高台组白云岩-蒸发岩共生地层高频层序划分及地质意义  

High-frequency sequence division and geological significance of dolomiteevaporite paragenetic strata of Cambrian Gaotai Formation in eastern Sichuan Basin

作　　者：胡忠贵[1,2] 王纪煊 李世临 郭艳波 左云安 庞宇来 HU Zhonggui;WANG Jixuan;LI Shilin;GUO Yanbo;ZUO Yun’an;PANG Yulai(School of Geosciences,Yangtze University,Wuhan 430100,China;Sedimentary Basin Research Center,Yangtze University,Wuhan 430100,China;Chongqing Gas Mine,PetroChina Southwest Oil and Gas Field Company,Chongqing 402160,China)

机构地区：[1]长江大学地球科学学院,武汉430100 [2]长江大学沉积盆地研究中心,武汉430100 [3]中国石油西南油气田公司重庆气矿,重庆402160

出　　处：《岩性油气藏》2023年第2期113-124,共12页Lithologic Reservoirs

基　　金：“十三五”国家科技重大专项“重点海相层系沉积相研究”(编号:2016ZX05007002)资助。

摘　　要：白云岩-蒸发岩共生地层中油气资源丰富。基于层序地层学原理,结合钻井、薄片等资料,在三级层序划分的基础上,采用INPEFA和小波变换技术对川东地区寒武系高台组白云岩-蒸发岩共生地层的高频层序进行识别与划分,并探讨了其地质意义。研究结果表明:(1)川东地区寒武系高台组白云岩-蒸发岩共生地层可划分为3个三级层序,自下而上分别为Sq1,Sq2,Sq3,可进一步划分为6个四级层序(ssq1—ssq6)。高台组主要为碳酸盐岩台地沉积环境,自西向东依次发育混积台地、局限-蒸发台地、开阔台地相沉积。(2)研究区高台组的岩性组合序列包括白云岩上覆厚层蒸发岩(A)、厚层白云岩夹蒸发岩(B)、白云岩与蒸发岩互层(C)和蒸发岩上覆厚层白云岩(D)等4种类型。白云岩-蒸发岩共生地层发育在四级层序的接触界面,且多发育于层序内部的高位体系域,反映了海平面较强烈的扰动,尤其是海平面的相对下降有利于白云岩和蒸发岩沉积。(3)研究区高台组白云岩-蒸发岩共生地层的岩性组合序列在GR_(inpefa)曲线和小波变换曲线上均具有响应特征,对应的64尺度小波系数曲线波动平缓,能量团为弱黄蓝色,GR_(inpefa)曲线以“缺口”的形式表现出蒸发岩与白云岩的岩性差异。The dolomite-evaporite paragenetic strata are rich in oil and gas resources.Based on the principle of sequence stratigraphy,combined with drilling and thin section data,and on the basis of third-order sequence division,INPEFA and wavelet transform technologies were used to identify and divide the high-frequency sequences of dolomite-evaporite paragenetic strata of Cambrian Gaotai Formation in eastern Sichuan Basin.The results show that:(1)The dolomite-evaporite paragenetic strata of Cambrian Gaotai Formation in eastern Sichuan Basin can be divided into three third-order sequences which are respectively Sq1,Sq2 and Sq3 from bottom to top,and can be further divided into six fourth-order sequences(ssq1-ssq6).The Gaotai Formation is mainly in a carbonate platform sedimentary environment,with mixed tidal flats,confined-evaporative platforms and open platform facies deposits developed in turn from west to east.(2)There are four types of intergrowth rock assemblages of Cambrian Gaotai Formation in the study area,including:thick-layered evaporite overlying dolomite,thick-layered dolomite interbedded with evaporite,interbedded dolomite and evaporite,and thick-layered dolomite overlying evaporite.The dolomite-evaporite paragenetic strata are developed at the contact interface of the fourth-order sequence,and are mostly developed in the highstand systems tract inside the sequence,reflecting a strong disturbance of sea level,especially the relative decline of sea level,which is conducive to the deposition of dolomite and evaporite.(3)The rock assemblage sequence of the dolomite-evaporite paragenetic strata of Gaotai Formation can generate response characteristics on the GR_(inpefa)and wavelet transform curves.The corresponding 64-scale wavelet coefficient curve fluctuates smoothly,and the energy clusters are weak yellow-blue.The GR_(inpefa)curve shows lithological difference between evaporite and dolomite in the form of“notch”.

关 键 词：白云岩-蒸发岩共生 最大熵谱分析 小波变换 高频层序划分 高台组 寒武系 川东地区 

分 类 号：TE121.3[石油与天然气工程—油气勘探]