Reservoir Characteristics And Comprehensive Classification Evaluation Of He8 Gas Reservoir In Area X Of Sulige Gas Field,Ordos Basin

The 8th member of the Lower Paleozoic Permian Shihezi Formation is the main production zone in the X area of the Sulige gas field in the Ordos Basin.The current exploration and development results show that the lack of a clear understanding of the reservoir characteristics of the target interval and the evaluation criteria for reservoir classification has restricted the subsequent rolling expansion and reserves stimulation.Therefore,on the basis of previous research results,this study combined with specific data such as geology,logging,production,etc.,combined with analysis of scanning electron microscopy,cast flakes,high-pressure mercury intrusion,visual displacement,gas-water phase infiltration,etc.In the test experiment,the characteristics of the He 8 reservoir in the X area are systematically studied,and the He 8 gas reservoir is comprehensively classified using mathematical methods,and various types of reservoirs are analyzed and evaluated to further select favorable production areas.The results show that:?1?A low-structural zone is developed in the central and western He 8of the study area,and the two wings develop near-western rhinoplasty with strong inheritance.?2?The sedimentary environment of the study area is the braided river delta front subfacies under the control of the north and northwest provenances,including underwater distributary channel microfacies,underwater natural dike microfacies and underwater distributary bay microfacies.In the next period of Box 8,several rivers developed.The hydrodynamic force in the east was extremely strong and the channel was relatively wide.There were only a few diversion bays in the southeast.In the last period of Box 8,the current in the east weakened,the bay between the diversions increased,and the hydrodynamics changed from strong to strong from bottom to top.Sand body distribution is controlled by sedimentary facies,and well-developed sand bodies are developed in underwater distributary channels.?3?The reservoir rock types in area X are mainly medium-coarse grain detrital quartz sandstone and quartz sandstone,which have the petrological characteristics of high quartz,very few feldspar and medium debris.The content of interstitial material is 12.9%on average,mostly clay minerals Cement with carbonate.?4?The average face ratio of the reservoir in the study area is2.42%.The main pore spaces are intergranular pores,feldspar and debris dissolution pores,and a small amount of intercrystalline pores and microcracks.The reservoir pore structure can be divided into four categories.?5?During the diagenesis period,there are mainly compaction,cementation,dissolution and metasomatism.Among them,the compaction and cementation strongly destroy the primary pores of the reservoir,while the secondary pores produced by the dissolution greatly increase the reservoir Storage performance.Combined with the changes of reservoir pores during diagenesis,it is summarized into three diagenetic evolution stages and divided into five types of diagenetic facies.?6?Through experiments such as visual displacement and gas-water seepage,quantitative analysis of the seepage flow law in the reservoir,it was found that the bound water content in the reservoir in the study area is relatively high,due to the high content of hydrophilic quartz minerals and complex pore throats structure.?7?Combining well logging data and measured physical property data to establish a physical property interpretation template and analyze the physical property characteristics of the whole area.The results show that the porosity of the reservoir in the 8th member of X zone is between 5%and 13%,and the permeability is between 0.01×10^-3?m²?5×10^-3?m²,belongs to low porosity-ultra-low permeability reservoir.Based on the study of reservoir characteristics,the reservoir is divided into four categories by using the combination of the fuzzy mathematics method and the actual productive conditions.In the study area,type?reservoirs,which mostly distributed in underwater distributary channel microfacies are the most developed.Followed by type?reservoirs and type?reservoirs,which distributed on both sides of the channel,natural embankments and inter-distributary bays.Type ? reservoirs is the least found in the study area.It mostly distributed in spots in the center of the channel.According to the characteristics of lithologic trap formation and reservoir classification in the study area,8 favorable production areas and6 potential production areas are predicted,with a total area of 17.98km² and 8.5km².