鄂尔多斯盆地中东部奥陶系马家沟组五段盐下白云岩储集层特征及其形成演化  

Characteristics, formation and evolution of pre-salt dolomite reservoirs in the fifth member of the Ordovician Majiagou Formation, mid-east Ordos Basin, NW China

作　　者：付斯一 张成弓 陈洪德[1,2] 陈安清 赵俊兴[1,2] 苏中堂 杨帅[1,2] 王果 密文天[3] FU Siyi;ZHANG Chenggong;CHEN Hongde;CHEN Anqing;ZHAO Junxing;SU Zhongtang;YANG Shuai;WANG Guo;MI Wentian(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China;School of Mines,Inner Mongolia University of Technology,Hohhot 010051,China)

机构地区：[1]油气藏地质及开发工程国家重点实验室,成都610059 [2]成都理工大学沉积地质研究院,成都610059 [3]内蒙古工业大学矿业学院,呼和浩特010051

出　　处：《石油勘探与开发》2019年第6期1087-1098,共12页Petroleum Exploration and Development

基　　金：国家自然科学青年基金项目(41602107);“油气藏地质及开发工程”国家重点实验室开放基金项目(PLC20180307);内蒙古自然科学基金(2018LH04006)

摘　　要：基于岩心、薄片观察与地球化学分析结果,对鄂尔多斯盆地中东部奥陶系马家沟组五段盐下白云岩储集层特征及其形成演化进行研究,得到以下几点认识:①盐下白云岩主要由微晶白云岩、晶粒白云岩和砂屑白云岩组成,晶间孔和各类溶蚀孔是主要储集空间;②研究区内成岩作用复杂,主要为白云石化作用、溶蚀作用、充填作用和重结晶作用等;③多阶段的白云石化作用有利于次生孔隙发育和原生孔隙保存,包括准同生阶段的蒸发泵白云石化作用、准同生—浅埋藏阶段的渗透-回流白云石化作用以及后期的埋藏白云石化作用;④多期次溶蚀作用对次生孔隙发育具有重要影响,同生—准同生期多期次次一级的海进-海退旋回导致易溶组分暴露溶蚀,发育次生孔隙;⑤埋藏期的有机酸溶蚀、硫酸盐热化学反应及其产物H2S生成的氢硫酸对储集层溶蚀改造,使储集空间进一步得到改善;⑥盐下层系中高H2S含量的区域可以成为下一步勘探潜在目标。The characteristics and formation of the pre-salt dolomite reservoirs in the fifth member of Ordovician Majiagou Formation in the mid-east Ordos Basin are investigated through observation of cores and thin sections,and geochemical analysis.(1)The pre-salt dolomites can be divided into dolomicrite,grain dolomite and dolarenite,in which the main reservoir space consists of intercrystalline pores and various dissolved pores.(2)The diagenesis in the study area is complex and mainly includes dolomitization,dissolution,filling,and recrystallization.(3)Multi-stages of dolomitization,including penecontemporaneous capillary concentration dolomitization,seepagereflux dolomitization during penecontemporaneous and shallow burial stage,and burial dolomitization in later stage,are conducive to the preservation of primary pores and development of secondary pores.(4)Multi-stages of dissolution also have strong influence on the development of secondary pores;the secondary transgression and regression cycles during the contemporaneous-penecontemporaneous stage led to exposure and dissolution of soluble minerals and thus the generation of secondary pores.(5)In the burial stage,reservoir pores were further improved due to organic acid dissolution and the dissolution by hydrosulphuric acid from thermochemical sulfate reduction(TSR)and its product H2S.(6)High H2S concentration area in pre-salt reservoirs can thus be considered as targets for future exploration.

关 键 词：鄂尔多斯盆地 奥陶系马家沟组 白云岩 膏盐岩 白云石化作用 溶蚀作用 

分 类 号：TE122[石油与天然气工程—油气勘探]