A Study On Palaeokarst Reservoir Of Ma5₁₊₂ Period In Y Area Of Jingbian Gas Field

In order to clarify the characteristics of the palaeokarst reservoir in the Ma51+2 period.Under the guidance of sedimentology and carbonate reservoir geology,more than 130 Wells in the study area were divided and compared.The corresponding stratigraphic framework was established and the related top surface structure maps were drawn.The structure of the study area is simple and faults and folds are not developed,which is a gentle monocline with a westward dip and a small dip angle.The reservoir of Ma51+2 period in the study area is restricted platform subfacies of carbonate platform facies.According to the composition of sediment,it can be divided into dolomitic flat,argillaceous dolomitic flat and calcareous dolomitic flat microfacies.The dolomitic flat microfacies is a favorable sedimentary facies belt for natural gas accumulation in the reservoir of Ma51+2 period.The palaeokarst landform in the study area was analyzed and restored by means of impression method and residual thickness method.The study area is located in the karst slope and the reservoir space types are mainly dissolution pore,intercrystalline pore,intergranular solution pores,gypsum mould pore and fracture.The physical property is extra low porosity and extra low permeability.According to the four relations of reservoir,lithology identification is carried out,the interpretation models of porosity,permeability and gas saturation are established.Based on the sedimentary facies,karst paleogeomorphology and diagenesis,the prediction map of favorable reservoir distribution is drawn,which provides theoretical reference for further exploration and development.