川西北栖霞组超深层白云岩储层特征及主控因素  

Development characteristics and main controlling factors of ultra-deep dolomite reservoirs of the Qixia formation in the northwestern Sichuan Basin

作　　者：刘文栋 钟大康[1,2] 尹宏 孙海涛[1,2] 梁雪祺 李荣容 卓骏驰 曾鑫耀 彭思桥 LIU Wendong;ZHONG Dakang;YIN Hong;SUN Haitao;LIANG Xueqi;LI Rongrong;ZHUO Junchi;ZENG Xinyao;PENG Siqiao(College of Geoscience,China University of Petroleum(Beijing),Beijing 102249,China;State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;Chuanxibei Division of PetroChina Southwest Oil and Gas Field Company,Jiangyou,Sichuan 621741,China;Exploration and Development Research Institute,SINOPEC Southwest Oil and Gas Branch,Chengdu,Sichuetn 610041,China)

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]中国石油大学(北京)油气资源与探测国家重点实验室,北京102248 [3]中国石油西南油气田分公司川西北气矿,四川江油621741 [4]中国石化西南油气分公司勘探开发研究院,四川成都610041

出　　处：《中国矿业大学学报》2021年第2期342-362,共21页Journal of China University of Mining & Technology

基　　金：国家自然科学基金项目(41972097)。

摘　　要：四川盆地西北部双鱼石地区栖霞组发育深度超过7000 m的孔隙度平均为2.94%的超深层优质白云岩储层,成为近年来油气勘探的重点.通过野外露头考察、岩心观察、薄片鉴定、阴极发光和稳定碳、氧同位素分析测试,认为双鱼石地区栖霞组厚层优质白云储层具有明显的"相控"和"层控"特点,而热流体活动对白云岩储层既有溶蚀有又充填.研究结果表明:栖霞组白云岩储集空间主要为晶间孔、晶间溶孔、溶蚀孔洞和裂缝,并以晶间孔和溶蚀孔洞为主要储集空间类型.栖霞组白云岩储层具有滩相沉积背景,并且受多种因素综合控制,其中有利相带是基础,原生孔隙发育的滩主体微相为后期白云石化流体活动提供了载体,其决定了白云岩储层在平面上的分布范围.海平面变化决定着栖霞组白云岩储层在纵向上的分布位置,栖霞组中下部沉积期,海平面较低,并存在多期高频海平面升降旋回,为厚层白云岩储层发育创造了条件.栖霞组大规模基质白云岩交代流体主要来自于沉积期海水,其δ^(13)C为1.5%~4.3%、δ^(18)O为-10.2%~-3.5%,基本处于同期海水同位素数值范围内;海平面较低时,在地貌相对较高的滩主体部位形成微蒸发浓缩海水,随埋深增加,沉积期"封存"的原生微浓缩海水在温压逐渐升高的背景下,开始突破白云石化作用发生的热力学障碍,不断交代周围高能颗粒滩相沉积物,形成厚层白云岩.埋藏期白云石化作用为栖霞组白云岩储层形成的关键,并且具有多阶段性,从细晶白云岩(δ^(18)O为-7.6‰~-6.3‰)至中晶白云岩(δ^(18)O为-8.8‰~-8.7‰)再到中粗晶白云岩(δ^(18)O为-9.7‰~-8.9‰),发生白云石化时所处的地层埋深逐渐增加,交代流体温度逐渐升高,导致白云岩氧同位素值逐渐较低,并且三者依次遵循了等体积交代、等摩尔交代以及发生过度白云石化,白云石晶间孔隙发育程度具有从低到高再降The Qixia formation in the Shuangyushi area of the northwestern Sichuan Basin has developed ultra-deep high-quality dolomite reservoirs with a depth of more than 7000 m and an average porosity of 2.94%,which has become the focus of oil and gas exploration in recent years.Through field outcrop survey,core observation,section identification,cathodoluminescence and stable carbon and oxygen isotope analysis tests,it is believed that the thick high-quality dolomite reservoirs of the Qixia formation in the Shuangyushi area have obvious characteristics of"facies control"and"stratification control",and thermal fluid activities both dissolve and fill the dolomite reservoirs,The results indicated:The dolomite reservoir space of Qixia formation is mainly inter-crystalline pores,inter-crystalline dissolved pores,dissolved pores and fractures,with inter-crystalline pores and dissolved pores as the main ones.The dolomite reservoir of the Qixia formation has a shoal facies sedimentary background and is comprehensively controlled by various factors.Among them,favorable sedimentary facies are the foundation among those factors.The microfacies of the main shoal with primary pores provide a carrier for the later dolomitization fluid activity,which determines the distribution of the dolomite reservoir on the plane.Sea level changes determine the vertical distribution of the dolomite reservoirs of the Qixia formation.During the deposition of the middle and lower parts of the Qixia formation,the sea level is low,and there are multiple periods of high-frequency sea level ups and downs,creating conditions for the development of thick dolomite reservoirs.The large-scale matrix dolomite replaced fluids of the Qixia formation mainly come from the seawater during the sedimentary period,with δ^(13)C ranging from 1.5% to 4.3% and δ^(18)O ranging from -10.2% to -3.5%,which are basically within the range of seawater isotopic values during the same period.When the sea level is low,micro-evaporation concentrated seawater is formed on the main p

关 键 词：白云岩储层 超深层 白云石化 热流体活动 栖霞组 四川盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]