鄂尔多斯盆地靖边气田区中奥陶统马家沟组五1-五4亚段古岩溶型储层分布特征及综合评价

鄂尔多斯盆地中部中奥陶统马家沟组最上部的马五1-马五4亚段是靖边气田区主要的产气层之一.按岩性及天然气勘探潜力每个亚段又可划分出2-4个小层,共12个小层.其中最佳产层为马五.12和马五13层,其次有马五11、马五14、马五22和马五41层.储层最主要的岩石类型是含硬石膏结核或含硬石膏柱状晶和结核的粉晶白云岩,其次为含...

Distribution Characters and Comprehensive Evaluation of Middle Ordovician Majiagou 51-54 Submembers Reservoirs in Jingbian Gas field Area, Ordos Basin

Ma51 to Ma54 Submembers that are at the uppermost part of Middle Ordovician Majiagou Formation are ones of the main nature gas pay horizons in Ordos Basin,According to the lithology and gas exploratory potential,each submember can be further divided into 2~4 layers which are 12 layers in total with total thickness of 70～80m.The best pay horizons are Ma512 and Ma513 layers,and the next ones are Ma511,Ma514,Ma522,Ma541 layers.In lithological types of reservoirs,the predominant one is silt-sized crystalline dolostone with anhydrite nodules or with anhydrite columnar crystalline and nodules,and the next is coarser silt-sized crystalline dolostone that contain intercrystal pores.Since experience for over 140 m.y.of sedimentary discontinuity form late Ordovician to Middle Carboniferous,the Ma51-Ma54 strata that situated at the topmost intensively suffered karstification of weathering palaeocrust during epidiagenetic exposure phase and formed a great amounts of solution pores,fissures,caves and channels.The secondary solution pores that formed during burial digenesis phase mostly stacked at the early paleaokastic pores and porous filling,or stacked at the coarser silt-sized crystalline dolostone with intercrystal pores so as to the stacked pore system developed.The good pore network that formed during Indo-Sinian and Yanshan movements formed in natural gas reservoir beds.By synthesizing the data of porosity,permeability,strata thickness,effective logging thickness,gas saturation and well flow from 399 wells,a criterion of reservoir evaluation is established.According to the criterion,the detailed reservoir evaluation does for each layer of Ma 51 to Ma 54 submembers and different reservoir grades of gas areas are cycled and mapped.