가스전의 컨덴세이트 축적 완화에 대한 시뮬레이션 연구

Abstract

A gas condensate is a single-phase fluid at original reservoir conditions in gas-condensate reservoir. As gas produces, reservoir pressure decreases continuously and the biggest pressure drops occur near the wellbore. Most gas condensate wells experience pressures below dew point pressure of the reservoir, which causes condensate to drop out and accumulate near the wellbore. As a result, the significant part of the pore space is occupied by the condensate and the relative permeability to gas reduces significantly. In this study, the condensate banking phenomena were analyzed for a real field. Chemical treatment and hydraulic fracturing was investigated for the reduction methods of the condensate banking using reservoir simulation. Three near-well models with different characteristics were constructed for the sensitivity analysis of the various reservoir properties. In the chemical treatment case, the chemical treatment effect was considered by changing the end points of the relative permeabilities and residual saturation of gas and oil. The simulation results showed that the optimal treatment radius from the wellbore was about 1.5 m. This result can be used to calculate the optimal chemical injection volume. In the case of hydraulic fracturing, the sensitivity study was carried out in terms of the number of the fractures and the fracture half-length. It was assumed that the fractures could be located at the toe, center, and heel of the horizontal section of the well and have the half-length of 20, 30, and 50 m. The results indicated that the cumulative production increased as the number of the fracture and fracture half-length increased. Therefore, hydraulic fracturing have a positive impact in increasing productivity because it makes the flow regime of the near wellbore changed from the radial to the linear flow.