Study On The Effective Utilization Of Reserves In Ultra-low Permeability Reservoirs

The characteristics of ultra-low permeability reservoirs are different from those of medium and high permeability reservoirs,which are related to the stress sensitivity of low permeability reservoirs.This paper introduces the seepage characteristics of stress sensitive reservoir and builds up the mathematical model which is then solved by numerical method at constant-rate condition.In the solution,the non-isometric difference is used and constant-rate condition is transformed into the inner boundary condition of the first space unit,the effect of stress sensitivity on permeability is also handled through explicit method.On this basis,production decline plate considering stress sensitivity was obtained according to Blasingame non dimensional definitions and beta derivative definition.The calculation results show production decline curves of stress sensitive reservoir are parallel with each other in each group during the period of boundary control flow.Besides,the corresponding curve moves down with the increase of dimensionless distance.The value of beta derivative curve is close to 1 during the period of the boundary-dominated flow.Based on the results of the stress sensitive production decline chart,the dynamic prediction of oil and gas well production.At the same time,the PVT property of reservoir fluid should be taken into account in the process of failure development.The results show: at the early stage of production,the smaller of the stress sensitive factor is,the larger the gas production rate is,and the faster the increase of cumulative gas production is;for the boundary-dominated flow regime at the late stage of production,the smaller of the stress sensitive factor is,the smaller the gas production rate is,and the slower the increase of cumulative gas production is,however the smaller stress sensitive factor corresponds to a bigger cumulative gas production.The key to the effective development of ultra-low permeability reservoirs is to determine the effective development well spacing.It is necessary to consider the effect of stress sensitivity on the ultimate radius of extra low permeability reservoir.In this paper,the development of effective use in determining failure radius of the basis,through the method of numerical simulation under different well spacing under the condition of low permeability reservoir water flooding when the saturation distribution and recovery degree of variation,and verify the failure to develop effective drainage radius from the rationality of water flooding development perspective.