靖边气田马五_(1-4)亚段沉积微相和成岩作用研究

Research on the Sedimentary Microfacies and Diageneses of Ma5_(1-4) Submember in Jingbian Gas Field

鄂尔多斯盆地靖边气田马五1～4亚段属于陆表海蒸发碳酸盐潮坪相。潮上带(含)石膏结核白云岩和潮间带上部的含石膏晶模白云岩最有利于形成储层。马五1-4亚段碳酸盐岩经历了复杂的成岩作用,准同生期白云石化和膏化作用奠定了储层的物质基础;表生岩溶期选择性溶解作用构筑了储层的轮廓;埋藏期溶解作用和各种矿物充填作用,决定早期溶孔能否保存和储层最终状况。引入"负胶结物孔隙度"概念,更直观地反映了沉积作用对马五1-4亚段储层发育的控制作用。将沉积微相和成岩相研究有机地结合在一起,以简约的方式,用一套数字组合符号半定量地表达沉积微相和成岩相,在开发区块储层评价和预测上获得了良好效果。

Majiagou Formation of the middle part of Ordos Basin belong to epeiric sea carbonatites and evaporates.Majiagou Formation have Ma1 Ma6 Member（from bottom to top）,Ma1,Ma3,Ma5 Members are micrite-fine powder dolomite,gyprock and saline.Ma2,Ma4,Ma6 Members are mainly micrite limestone or wackestone.Caledonian event uplift North China Platform since last stage of Middle Ordovician.The top of Majiagou Formation in Ordos Basin udergo weather worn in 1300 million endurance.Weathered crust dolomite reservoir of the top of Ma5 Member are produced by dissolution of ancient karst.Ma5 member divided into Ma510,Ma59…Ma51from bottom to top.The producing pay allocation in Ma51-4〗submember which are top of weather crust.Ma51-4submember have thick 80 ～ 110 m,are dolomite,argillaceous dolomite,minor gypseous dolomite andtuffaceous mudstone.The reservoir rock of Ma51-4 submember are mainly corrosion pore and hole dolomite,valid reservoir are grand total 2 ～ 10 m,which initial rock are gypseous micrite-fine powder dolomite.Ma 51-4submember of Jinbian Gas Field in Ordos Basin belong to evaporated carbonate tidal flat facies,which divided into three subfacies：supratital zone,intertital zone,infratital zone,and 18 microfacies.The microfacies that are favour of developing reservoirs are supratidal zone dolomite which have anhydrite noddle and upper part intertidal zone dolomite which have anhydrite crystal.Ma51-4 Submember had undergone various diageneses.Penecontemporaneous dolomitization and gypsification that settled material base of reservoirs.Epidiagenesis selective dissolution of gypseous dolomite constructs the ambit of reservoirs.anhydrite noddle and crystal in dolomite selectively dissolved by meteoric fresh water and create pore and hole.Dissolved pore and hole what partly fill by one or some mineral form reservoirs.Early stage dissolution pore and hole are reconstructed by burial period dissolution,fill mineral sort and amount that determine the preservation condition of dissolution pore and the feature of reservoirs.Call in＂minus cement porosity＂,it directly reflects sedimentary that control reservoir Ma51-4 Submember.Combining of research microfacies and diagenesis facies,use concise numerical symbol that express semiquantitatively sedimentary microfacies and diagenesis facies.Used that in compilation microfacies chart and diagenesis partition chart,beneficial area for reservoir is so clearly.That method acquire approved effect on the evaluation and forecasing reservoir of Jingbian Gas Field.