Study On Seepage Law Of Tight Sandstone And Coal-rock Interbedded Gas Reservoirs

Explorations of Shenfu-Linxing section in eastern Ordos Basin have shown a coexistence of coalbed methane and tight gas in this area.However,due to the coal bed and compact sandstone layer are featured with thin reservoir stratum,complicated contact relations and low mono-stratum productivity,it is required to apply the "Coal-Compact"combined exploitation to form a pressure disturbance so that the gas well productivity can be increased.Owing to that the coal bed and compact sandstone layer differ with each other in terms of reservoir status,rock property,filtration capacity and way of development,it is required to study these two systems under different contact relations from many perspectives,such as gas-water flow rules,pressure distribution rules,productivity disturbance rules,interlayer replacement rules and shaft coupling rules.Based on the analyses on the contact relations of the coal bed and compact sandstone layer in Shenfu-Linxing district,three simplified contact geologic models and numerical models were set up,including direct contact of;"Coal-Compact",indirect contact of "Coal-Compact" and non-contact of "Coal-Compact".Meanwhile,by adopting methods of mechanism analysis and numerical simulation,the rules of interlayer disturbance for individual exploitation of the coal bed or compact sandstone layer and the "Coal-Compact"combined exploitation were studied:By comparing the gas-water flow status,interlayer pressure distribution and reservoir productivity for "Coal-Compact" interbeded gas reservoir under different contact relations,the theory,time and intensity of the interlayer disturbance for "Coal-Compact" interbeded gas reservoir were determined.Moreover,different development proposals of interlayer replacement were designed according to varying contact modes for the;"Coal-Compact" interbeded gas reservoir.Then,the optimal development mode under different interlayer disturbances was selected with the help of numerical simulation method.In line with the relationship between the water drainage amount of shaft and water yield amount of reservoir in the event of "Coal-Compact" combined exploitation,a coupling study was carried out and a coupling relationship model involving the water drainage amount and water yield amount of reservoir was put forward.Consequently,mine field data and numerical simulation method were adopted to compare the practical cases and verify the analyses.Based on the analyses on the contact relations of the coal bed and compact sandstone layer in Shenfu-Linxing district,three simplified contact geologic models and numerical models were set up,including direct contact of "Coal-Compact",indirect contact of "Coal-Compact" and non-contact of "Coal-Compact".Meanwhile,by adopting methods of mechanism analysis and numerical simulation,the rules of interlayer disturbance for individual exploitation of the coal bed or compact sandstone layer and the "Coal-Compact"combined exploitation were studied:By comparing the gas-water flow status,interlayer pressure distribution and reservoir productivity for "Coal-Compact" interbeded gas reservoir under different contact relations,the theory,time and intensity of the interlayer disturbance for "Coal-Compact" interbeded gas reservoir were determined.Moreover,different development proposals of interlayer replacement were designed according to varying contact modes for the "Coal-Compact" interbeded gas reservoir.Then,the optimal development mode under different interlayer disturbances was selected with the help of numerical simulation method.In line with the relationship between the water drainage amount of shaft and water yield amount of reservoir in the event of "Coal-Compact" combined exploitation,a coupling study was carried out and a coupling relationship model involving the water drainage amount and water yield amount of reservoir was put forward.Consequently,mine field data and numerical simulation method were adopted to compare the practical cases and verify the analyses.