Comprehensive Evaluation Method For Recovery Of Tight Gas Reservoirs

Tight gas reservoirs have the characteristics of poor reservoir properties,high water saturation,strong heterogeneity,and complex seepage laws,resulting in low recovery,which is only about 30%.And the recovery of tight gas reservoirs is difficult to be accurately calibrated.At present,there is no specific unified method for the identification of factors affecting the recovery of tight gas reservoirs,which are often treated with conventional low-infiltration geological understanding and corresponding evaluation methods.Based on this problem,this paper takes the tight gas reservoir in the eastern area of Sulige gas field as the research object.Firstly,from the experimental study of reservoir microstructure,the evaluation reveals the microscopic seepage characteristics of tight gas reservoirs,among which the microscopic factors mainly include slippage effect,starting pressure gradient and stress sensitivity;Then,the main control factors affecting the recovery are comprehensively identified and optimized,and the influence weights of the main controlling factors are determined by using grey correlation analysis method,thus forming a multi-factor comprehensive evaluation method for tight gas reservoir recovery;Next,combined with the experimental results and theoretical analysis,a matrix-fracture tight gas reservoir seepage model considering slippage effect,start-up pressure gradient and stress sensitivity effect is established;Based on the seepage model,combined with the multi-factor comprehensive evaluation method of tight gas recovery,a dynamic F-recovery model is established,and then a comprehensive evaluation method for tight gas reservoir recovery is formed;Finally,the comprehensive evaluation method of tight gas reservoir recovery is applied to evaluate the recovery rate of the tight gas reservoir in the eastern area of Sulige gas field.According to the evaluation results,the optimum development method for enhanced oil recovery in this gas reservoir is determined.The establishment of comprehensive evaluation method for tight gas recovery has fully considered the macroscopic geological characteristics and microscopic seepage characteristics of tight gas reservoirs,and is more in line with the actual characteristics of gas reservoirs,which has certain guiding significance for the evaluation and efficient development of tight gas reservoirs.