Dynamic Analysis Of Production Gas Wells In SDN Gas Reservoirs And Study Of Rational Working Systems

SDN gas reservoir belongs to the sandstone gas reservoir with characteristics of low porosity, low permeability, low abundance, wide gas-bearing area and large buried depth. Fractured vertical wells and fractured horizontal wells were widely applied into the exploitation of this gas reservoir. The whole gas reservoir is characterized by low single-well deliverability, short stable production time and rapid production decline. Therefore, researches of single well controlled reserves, productivity and rational production proration of fractured wells have important theoretical and practical significance to develop SDN gas reservoir in an efficient and economical way.Based on geological features and practical productivity data of SDN gas reservoir, this paper took fractured wells as research objects. Firstly, through parameters of open-flow capacity, gas-well production, the paper divided fractured vertical wells and fractured horizontal wells into three different types, respectively, stating and comparing dynamic productivity characteristics of different kinds of gas wells. Then, the single well controlled reserves of fractured wells were calculated by pressure drop method, flowing material balance method and rate transient method. Secondly, considering influence of slippage effect, non-darcy effect and stress sensitivity effect, a new productivity model of fractured vertical wells was derived by introducing Lame coefficient of the elliptical coordinates and pseudopressure function. On account of elliptical seepage theory, equivalent wellbore radius principle and superposition principle, the paper built new deliverability model of fractured horizontal wells under mutual interference among multi fractures. The result of modified isochronal well test verified the accuracy of deliverability model of fractured vertical wells and fractured horizontal wells, individually, meanwhile, analysing influence of the reservoir thickness, gas slippage effect, half-length of the fracture, stress sensitivity of fracture and fracture flow conductivity on the productivity of gas well and optimizing parameters of the fracture. At last, based on the new productivity model and open-flow capacity of gas well, this paper studied the reasonable productivity allocation of three different kinds of fractured vertical wells and fractured horizontal wells, combining empirical method, gas recovery curve method and critical liquid carrying flow rate method.The content studied in this paper consummated the theory of production performance analysis and production analysis of fractured vertical wells and fractured horizontal wells. Moreover, The paper offered theoretical foundations and rational methods for the proper production proration, having practical significance for guiding performance analysis, productivity prediction and proper production allocation of similar gas reservoirs.