鄂尔多斯盆地中东部奥陶系盐下深层储层特征及主控因素  

Characteristics and main controlling factors of Ordovician deep subsalt reservoir in central and eastern Ordos Basin

作　　者：付玲 李建忠[1] 徐旺林[1] 郭玮[2] 李宁熙 张月巧[1] 宋微[1] 孙远实 FU Ling;LI Jian-zhong;XU Wang-lin;GUO Wei;LI Ning-xi;ZHANG Yue-qiao;SONG Wei;SUN Yuan-shi(Petro China Research Inustituter of Petroleun Explration and Development,Beijing 100083,China;Petro China Changqing Oil Field Branch Company,Xi'an 710018.China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]中国石油长庆油田分公司,陕西西安710018

出　　处：《天然气地球科学》2020年第11期1548-1561,共14页Natural Gas Geoscience

基　　金：国家重点研发计划“深地资源勘查开采”重点专项(编号:2018YFC0603706);国家科技重大专项“下古生界—前寒武系碳酸盐岩油气成藏规律、关键技术及目标评价”(编号:2016ZX05004);中国石油勘探与生产分公司科技项目“鄂尔多斯盆地新层系新领域研究与有利区带评价”(编号:kt20180401)联合资助。

摘　　要：鄂尔多斯盆地奥陶系盐下深层白云岩储层近年来取得较好的勘探效果,具有一定勘探前景。综合运用岩心观察、铸体薄片、扫描电镜、物性分析、压汞等资料,对盆地中东部奥陶系盐下深层马家沟组马三段、马四段储层特征及其发育的主控因素展开研究。结果表明:马三段储层以海退蒸发环境的含膏云岩为主,马四段储层以海侵环境的灰质云岩、粉—细晶云岩为主;马四段、马三段主要储集空间类型分别为溶孔(溶洞)、晶间孔、晶间溶孔、微裂隙;微裂隙、膏模孔、溶孔和粒间孔;孔隙结构复杂,毛管压力曲线形态可划分为溶孔型、晶间(溶)孔型、微裂隙型和微孔型4种类型;现有资料显示马三段—马四段平均孔隙度分别为2.1%和2.3%,平均渗透率分别为0.19×10-3μm2和0.22×10-3μm2。中央古隆起、乌审旗—靖边次级古隆起以及神木—子洲低隆带控制了马三段—马四段沉积相带及有利岩相分布;沉积微相控制岩石原始沉积组构,一定程度影响储层物性,砂屑云岩、晶粒云岩及膏质云岩的储层物性通常相对较好;此外,成岩作用也是控制盐下储层发育的关键因素,多种成因机制下的白云化作用是晶间孔形成的主要方式,表生成岩环境及埋藏成岩环境下的溶蚀作用控制了次生孔隙的发育;燕山期构造活动对储层微裂隙的发育起关键作用,显著改善了储层渗透性。总之,构造背景、岩石组构、成岩作用以及裂缝作用决定了盐下深层储层的储集性能,是优质储层形成的主控因素。In recent years,the sub-salt dolomite reservoirs in the Ordovician strata of the Ordos Basin have indicated good exploration results and are expected to have a high hydrocarbon potential.This study targets the Ma3-Ma 4 reservoirs below the salt rock of the Ordovician in the central and eastern Ordos Basin and investigate the reservoir characteristics and main controlling factors of high-potential reservoirs by combining core observations,cast slabs,scanning electron microscopy,physical property analysis and mercury injection data.The results show that the Ma 3 reservoirs are dominated by gypsum-bearing dolomite deposited in evaporation environments,whereas the Ma 4 reservoirs are dominated by calcite dolomite under transgressive environment.The types of Ma 4 reservoir space mainly include dissolved pores(dissolved holes),intra-crystalline pores,intracrystalline dissolved pores and microcracks.The types of Ma 3 reservoirs space mainly include microcracks,gypsum mould pore dissolved pores(dissolved holes),and intergranular pores.The pore structures of reservoirs are complex.The capillary pressure curves can be divided into four types,including dissolved pore type,intra-crystalline(dissolved)pore type,microcrack type,and micro-porous type.Based on available information,the average porosity of the Ma 3-Ma 4 reservoirs are 2.1%and 2.3%,respectively,and the average permeability values are 0.19×10-3μm2 and 0.22×10-3μm2,respectively.The central paleo-uplift,Wushenqi secondary paleo-uplift and Shenmu low uplift controlled the sedimentary facies and favorable lithofacies distributions.Sedimentary microfacies control rock fabric,and the rock fabric affect physical properties of the reservoirs.The limestone and dolomite reservoirs with gypsum and sand cutting texture have relatively good physical properties.Diagenesis is also a key factor in the development of sub-salt reservoirs.Intra-crystalline pores are mainly formed under various dolomization mechanisms.The surficial and buried diagenetic environments facilitate the

关 键 词：鄂尔多斯盆地 盐下深层储层 储集空间 成岩作用 古隆起 微裂隙 

分 类 号：TE122.1[石油与天然气工程—油气勘探]