Study On Seepage Characteristics And Gas Supply Mechanism Of Tight Sandstone Gas Reservoir In Y Gas Field

The Y gas field is located in the southeastern part of the Ordos Basin.The reservoirs He 8,Shan 1,and Shan 2 of this studied area are characterized by low porosity,low permeability and strong heterogeneity.At present,the gas reservoir is in the early stage of development,lacking reasonable development technology policy support.Therefore,it is urgent to study the microscopic pore structure characteristics,seepage characteristics,and planar heterogeneous gas supply mechanism.systematically To exploit the development potential of potential reservoirs.The main results of this paper are as follows:(1)the storage space of 6 samples is mainly micro,fine pores and throat,and the sorting is poor.The reservoir capacity is better,but the seepage capacity is poor.In addition,the core pore radius does not change much.However,with the change of rock physical properties,especially the permeability,the distribution of throat radius varies greatly,and the throat is multi-modal.Wide range distribution;the pore throat radius ratio is an important controlling factor for the seepage capacity of tight sandstone reservoirs.(2)The results show that the movable water in the core is mainly distributed in the macropores,and when the pressure difference is lower,it was firstly driven out.As the displacement pressure difference increases,the brine present in the small pores is gradually driven out,and the water saturation of the low permeability gas reservoir is not a constant value during development.(3)The indoor experimental analysis is used as a means to study the gas-water seepage characteristics of the tight cores.Under high temperature and high pressure,the bedrock core permeability curve has a wider two-phase co-infiltration zone.However,the two-phase co-infiltration zone is narrowed and water channeling is highly prone to occur in the fractured core during water flooding process.In addition,the water-flooding efficiency drops sharply.(4)The physical model of planar heterogeneous gas supply in the long core series with joined high and low permeability core is established.The experimental results show that the recovery of gas reservoirs can be affected by the heterogeneous extreme of the gas reservoir and production(exploitation rate),and fracturing can significantly improve the recovery of strong heterogeneous gas reservoirs.(5)The numerical simulation model was established firstly to fit the results of planar heterogeneous gas supply experiment and then was extended to the actual single well plane heterogeneous seepage model.The effect mechanism of permeability grades,physical properties,different exploitation rate,fracturing and different ratios of high and low permeability zones on recovery were studied.The results show that when the permeability of the low-permeability zone is lower than 0.1mD,the residual pressure in the zone is obviously increased at the end of production,that is,the degree of utilization of the low permeability zone is significantly reduced.