INVESTIGATION OF THE IMPACT OF CONDENSATE BLOCKAGE ON WELL PRODUCTIVITY IN A TIGHT GAS CONDENSATE RESERVOIR - CASE STUDY OF TAWES FIELD

摘要

The Tawes Gas field in Block B, South Natuna Sea was discovered in 1988 by the Tawes-1 exploration well and appraised by the Tawes-2 well in 1999. The primary reservoir is the Gabus-3B sandstone. Economic development of the field is challenging due to its poor quality reservoir and fluid properties. In low permeability reservoirs, rich gas produced below the dew point has a negative effect on permeability in the near wellbore area. For tight gas reservoirs such as the Gabus 3B, high drawdown pressure is needed to flow gas, consequently condensate saturation banking will occur near the wellbore as the pressure drops below dew point pressure. The buildup of condensate saturation is called condensate blockage. This effect causes a significant drop in gas relative permeability, which reduces the productivity of the well. To investigate and to model the condensate blockage phenomena in a numerical reservoir simulation, a radial single well model was first used. For a sector or full-field model with a coarser Cartesian grid, Generalized Pseudo-Pressure (GPP) was found to be the best method to capture the phenomena without the need to use fine grid simulation. Hydraulic fracturing was evaluated as a method to enhance productivity. In an earlier initial assessment, a study using a mechanistic model was performed and concluded that hydraulic fracturing could increase the well deliverability and the total recovery of the field. However, the potential effect of condensate blockage was not taken into account in that study. This paper focuses on the use of numerical simulation to investigate the condensate blockage phenomena in the reservoir and also to examine if hydraulic fracturing could still be beneficial to increase the productivity of a gas reservoir with condensate blockage.