Comparison of Well Productivity Between Vertical, Horizontal and Hydraulically Fractured Wells in Gas-Condensate Reservoirs

摘要

Gas condensate reservoirs usually exhibit complex flow behaviors due to the build-up of condensate banks around the wells when the bottomhole pressure drops below the dew point. The liquid phase accumulation in the near-wellbore region forms a ring that reduces the gas relative permeability. As a result, gas production decreases and the hquid phase which is a significant part of the value of the field remains in the reservoir. Various solutions have been implemented in order to remediate such a productivity loss. They include drilhng horizontal wells instead of vertical wells, hydrauhcally fracturing vertical wells before or after the development of the condensate bank, and acidizing after the condensate bank has formed. In this work, we used reservoir simulation to quantify the increase in well productivity from different remediation solutions and assess their effectiveness. The empirical correlations needed to model non-Darcy flow and capillary number effects, which are among the main parameters that control gas condensate well performance, were calibrated with actual well test data.As should be expected, we found that horizontal wells and hydrauhcally fractured vertical wells improve well productivity. The degree of productivity enhancement, however, depends on well and reservoir parameters such as horizontal well lengths, permeability anisotropy, fracture length and fracture conductivity. Different simulation models were run above and below the dew point pressure at the same reservoir and flow conditions. The results of our simulations show that horizontal wells enhance productivity significantly below the dew point. Performance improvement with hydrauhc fractures, on the other hand, depends on facture length and fracture conductivity.