Optimizing the Productivity of Gas/Condensate Wells

Abstract

Abstract Gas-condensate reservoirs exhibit complex phase and flow behaviors due to the appearance of condensate banking in the near-well region. A good understanding of how the condensate accumulation influences the productivity and the composition configuration in the liquid phase is very important to optimize the producing strategy, to reduce the impact of condensate banking, and to improve the ultimate gas recovery. This study addressed several issues related to the behavior of the composition variation, condensate saturation build-up and condensate recovery during the gas-condensate producing process. A key factor that controls the gas-condensate well deliverability is the relative permeability, which is influenced directly by the condensate accumulation. The accumulated condensate bank not only reduces both the gas and liquid relative permeability, but also changes the phase composition of the reservoir fluid, hence reshapes the phase diagram of reservoir fluid and varies the fluid properties. Different producing strategies may impact the composition configuration for both flowing and static phases and the amount of the liquid trapped in the reservoir, which in turn may influence the well productivity and hence the ultimate gas and liquid recovery from the reservoir. Changing the manner in which the well is brought into flowing condition can affect the liquid dropout composition and can therefore change the degree of productivity loss. In this study, compositional simulations of multicomponent gas-condensate fluids were conducted at field scale to investigate the composition and condensate saturation variations. Different producing strategies have been compared, and the optimum producing sequences are suggested for maximum gas recovery. A core flooding experiment with two- component synthetic gas-condensate was designed and constructed to model gas-condensate production behavior from pressure above the dew-point to below. Experimental observations of gas-condensate production confirm the dramatic changes in the liquid composition seen in the simulations.