Semianalytical Modeling for Multiphase Flow in a Fractured Low-Permeability Gas Condensate Reservoir.

Abstract

During the production of fractured low-permeability gas condensate reservoir (FLPGCR), a phase transition takes place in both the formation and wellbore, resulting in multiphase flow when the pressure drops below the dew point pressure. Additionally, the presence of fractures causes the formation of stress-sensitive characteristics. Nevertheless, traditional analytical models, such as the two-region model or three-region model, overlook the coupling impact of the above factors, which could lead to incorrect pressure transient response and erroneous estimation of well and formation parameters. Therefore, this work presents a semianalytical model for an FLPGCR considering the effects of multiphase flow, stress-sensitive, and wellbore phase redistribution. The gas condensate reservoir is divided into N banks, and the radial fluid saturation variation is modeled by multiple annular reservoirs with a constant saturation in each annular reservoir. The behavior of a fractured reservoir is modeled by using the dual-porosity model. The Pedrosa transform was utilized to address the nonlinear differential equation arising from stress-sensitive behavior. To verify the semianalytical solution, it was compared with numerical simulation results from CMG. The results showed that there are 10 flow regimes for the proposed model. The shape of the type curve has the potential to identify the degree of blockage within the FLPGCR. The wellbore phase redistribution only affects the first transitional-flow regime, which slows the rate of pressure drop. The stress sensitivity will lead to the upward characteristic of the curve in a later stage. More attention should be paid to the upward pressure derivative curve at late times, which is conventionally regarded as the effect of a closed boundary when it may not be the case. In addition, the shape factor and composite radius may obscure the radial flow regime. Finally, the proposed model was applied to interpret the pressure measurements recorded from the Bohai field in China, which exhibits a better fitting quality than the traditional models.