Abstract
Water breaks through along fractures is a major concern in tight sandstone reservoirs with a bottom aquifer. Analytical models fail to handle the three-dimensional two-phase flow problem for partially penetrating inclined fractures, so time-consuming numerical simulation are often used for this problem. This paper presents an efficient semianalytical model for this problem considering three-dimensional fractures and two-phase flow. In the model, the hydraulic fracture is handled discretely with a numerical discrete method. The three-dimensional volumetric source function in real space and superposition principle are employed to solve the model analytically for fluid flow in the reservoir. The transient flow equations for flow in three-dimensional inclined fractures are solved by the finite difference method numerically, in which two-phase flow and stress-dependent properties are considered. The eventual solution of the model and transient responses are obtained by coupling the model for flow in the reservoir and discrete fracture dynamically. The validation of the semianalytical model is demonstrated in comparison to the solution of the commercial reservoir simulator Eclipse. Based on the proposed model, the effects of some critical parameters on the characteristics of water and oil flow performances are analyzed. The results show that the fracture conductivity, fracture permeability modulus, inclination angle of fractures, aquifer size, perforation location, and wellbore pressure drop significantly affect production rate and water breakthrough time. Lower fracture conductivity and larger inclination angle can delay the water breakthrough time and enhance the production rate, but the increment tends to decline gradually. Furthermore, water breakthrough will occur earlier if the wellbore pressure drop and aquifer size are larger. Besides, the stress sensitivity and perforation location can delay the water breakthrough time.
Highlights
In recent years, tight sandstone reservoirs have been discovered as unconventional oil and gas resources with great potential, and hydraulic fracturing technology has been very critical for improving the well productivity of this kind of reservoir [1,2,3,4]
This paper proposed a semianalytical model to analyze production data and predict water breakthrough time in tight sandstone reservoirs with a bottom aquifer
The results suggest that the proposed model can model fluid flow in threedimensional large-scale fractures and predict the production profiles and water breakthrough time of fractured wells in tight sandstone reservoirs with a bottom aquifer
Summary
Tight sandstone reservoirs have been discovered as unconventional oil and gas resources with great potential, and hydraulic fracturing technology has been very critical for improving the well productivity of this kind of reservoir [1,2,3,4]. Semianalytical models capture the two-phase flow behavior in the fracture and have much higher computational efficiency than numerical simulation methods, which have recently attracted increasingly attention [25,26,27,28,29]. Much work has been devoted to the two-phase flow models, there are many challenges in developing semianalytical solutions for fractured wells in tight sandstone reservoirs with a bottom aquifer. The novelty of the new model is in the ability to semianalytically obtain the performance of production wells in tight sandstone reservoirs with a bottom aquifer It provides an efficient method for modeling bottom water coning, combining threedimensional fracture characteristics and two-phase flow
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