Study On Decreasing Yield Of Horizontal Wells In Multi - Stage Fracturing Of Shale Gas Reservoirs

Currently the exploration and development technology of shale gas is prior to its theoretical research, and production decline analysis is the basis for predicting shale gas reservoir performance, so it is necessary to study the percolation theory and production decline law of multiply fractured horizontal well in shale gas reservoirs. Based on the analysis of the storage, migration and production mechanisms of shale, mathematical models of a shale gas multi-stage horizontal well (MFHW) were established by considering desorption, Knudsen diffusion and slippage effect in matrix pores. Finally, the production decline law of a shale gas MFHW was thoroughly analyzed. The main works are as follows:(1) The linear dual porosity SRV model and its analytical solution were derived, the corresponding curves of production decline were got and flow processes were divided, and the parameters like interporosity flow coefficient, storativity ratio, desorption factor, apparent permeability factor and reservoir size etc. were analyzed.(2) The conventional tri-linear flow models of homogenous and dual porosity formation and their solutions were derived, the corresponding curves of production decline were got and flow processes were divided, and the parameters like conductivity of hydraulic fracture and reservoir, capacity of hydraulic fracture, density and permeability of hydraulic fracture and natural fracture, Knudsen diffusion factor and slippage factor etc. were analyzed.(3) The variable tri-linear flow models of homogenous and dual porosity formation and their solutions were derived, the corresponding curves of production decline were got and flow processes were divided, and the parameters like conductivity and capacity of hydraulic fracture, nature fracture permeability ratio of inner and outer region, density and permeability of hydraulic fracture and natural fracture, Knudsen diffusion factor and slippage factor etc. were analyzed.(4) Two analysis methods of production decline were presented, including mixed method which combining Arp’s hyperbolic decline and transient linear flow solution, and tri-linear flow solutions matching method.(5) For the dynamic production data of#314well in Barnett shale, the analysis methods presented in this paper were used to predict the future production of this well and estimate corresponding parameters. These two methods can estimate formation and hydraulic fracture parameters, and predict production well. However, the b of mixed method is not a constant, but gradually decreases to zero, so that the production predicted by mixed method will be overestimated.