The Research On Reservoir Geological Characteristics Of The Major Gas Reservoirs Of Majiagou Formation In Tao2 Block,Sulige

T2 block is located in the southeast of Sulige gas field,close to Changqing Jingbian gas field,the work area is about 651km².In recent years,the Sulige gas field has increased the natural gas exploration and development of the T2 block,found the gas reservoir in the Ma5 of the Ordovician Majiagou Formation in the Lower Paleozoic,and showed good development potential,but the current geologic study of paleoclimatic reservoirs in this area is weak and can not meet the urgent need of gas reservoir development in this area.Based on the core observation,logging,geological logging,productivity test and dynamic production data as a foundation,with the polarizing microscope,mercury penetration analysis,image analysis and other testing techniques,detailed research and analysis of the reservoir geological characteristics of the major gas reservoirs in Majiagou Formation in the study area,so as to provide a reliable geological basis for the efficient development of the Lower Paleozoic gas reservoirs.Based on the analysis of core,thin sections,logging,geological logging,lithologic microfacies and sedimentary structure characteristics as a symbol,the Ma5_1-4 submember of sedimentary environment is the tidal flat facies of continental sea.Including 2 subfacies and 16 microfacies,the facies of supratidal dolomite flat,supratidal argillaceous dolomite flat and supratidal lime dolomite flat are beneficial to the development of reservoir.The reservoir is modified by many diagenesis,dolomitization and karstification play a constructive role in the development of reservoir space.The basic characteristics of the reservoir in the study area are studied by using core,well logging and geological logging data,the main rock types in the study area are grain dolomite,granular dolomite,argillaceous dolomite,lime dolomite,dolomitic limestone and gypsum dolomite.Ma51 submember physical properties slightly better than Ma5₄,Ma5₁³ small layer of physical properties better than Ma5₄¹ small layer.There are 13 types of reservoir space types,composed of three types of pore cave fracture,fracture-cave and fracture dissolution pore.According to the development degree of porosity,the form of pore cave fracture and the capillary pressure curve,four types of reservoirs are divided into four types of typical capillary pressure curves.The opening of the micro cracks and the filling residual hole of dissolution pore or the hole and intercrystalline pore has a great contribution to the effectiveness of the reservoir.The significance of fracture in the reservoir of the study area lies in the fact that there is no crack and no reservoir.Comprehensive core,well logging,mud logging,gas testing and other data,draw the lithology,electrical properties,physical properties and gas bearing parameters histogram,cross plot to carry out the reservoir four characteristics correlations.It is found in the study that the conclusion of the relationship between lithology and electricity is consistent with the previous results.The correlation between physical properties and electrical properties is mainly reflected in the correlation between porosity and acoustic parameters.The coincidence rate of single well in the study area was evaluated as “moderate” and “good”.Supratidal dolomite flat and supratidal argillaceous dolomite flat are the dominant microfacies of the reservoirs in the Ma5_1-4 submember of the study area,which control the development and distribution of the reservoirs.Intercrystalline intergranular pore and intergranular dissolved pores as a symbol of the dolomitization of the formation of dolomite reservoir plays a controlling role.Syngenesis solution gave birth to the embryonic form of the reservoirs of Ma5_1-4 in the study area,epidiagenesis solution forms the basic outline of the paleokarst reservoir,burial solution further transforms the karst reservoir into the present situation.Comprehensive rock types,sedimentary microfacies,physical properties,pore structure,reservoir space types,four characteristics correlations with rate evaluation,gas saturation,effective thickness and flow parameters of well logging,developed reservoir evaluation and classification criteria,Ma5_1-4 submember reservoir of the study area is divided into four categories.The study area is mainly distributed with ?+? class reservoir.The combination of intergranular pores,intergranular dissolved pores,caves and fractures is a good reservoir in the study area.