Abstract

Horizontal wells with multistage hydraulic fracturing stimulation become the common practice in developing tight and shale gas reservoirs. For gas condensate reservoirs, heavier components in the gas phase start dropping and decrease the gas mobility due to a relative-permeability relationship as reservoir pressure drops below the saturation pressure. Therefore, modeling the condensate banking along hydraulic fractures becomes critical in understanding the productivity loss, the hydraulic fracturing job design as well as the field production optimization. In addition, along with pressure depletion, the stress dependent permeability must be taken into account either by an approximation derived from lab experiments inside a finite difference flow simulator or modeling separately by a finite element geomechanics code.

A condensate fluid pseudoization that reduces nine hydrocarbon components to a pseudo three components mixture is presented in this paper. The control volume based multiphase multi-components thermal simulator FATS is utilized in modeling the condensate banking inside the hydraulic fractures and surrounding matrix blocks. A K-value interpolation algorithm is developed and validated by a two-phase envelope generated by an Equation of State (EOS). FATS results are validated by the EOS based reservoir simulator GEM.

A compositional simulation model is coupled with reservoir geomechanics in this study to investigate the interaction of stress changes and its effects on multiphase flow along fractures. A modular coupled approach is implemented for solving the stress and flow equations at each time step by the iteration between the reservoir simulator and geomechanical module. Pressure and temperature changes occurring in the reservoir simulator are passed to the geomechanical simulator to compute the changing of stress and strain and updating porosity and permeability simultaneously. Simulation results show that fracture conductivity reduction is due to the combination of condensate banking and changing of the effective stress along hydraulic fractures.

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