Wellbore Liquid Blockage in Gas-Condensate Reservoirs

Abstract

Abstract Gas condensate reservoirs have long presented production problems when the pressure around the well bore drops below the dewpoint pressure. The formation of the condensate around the well bore can be thought of as an additional "skin" that causes a reduction in the gas flow rates. Many processes have been used successfully to prevent or reduce the formation of liquids within the entire reservoir, such as pressure maintenance schemes and gas cycling processes. The pressure maintenance scheme is designed to keep the reservoir pressure at or above the dewpoint pressure while the gas cycling process is intended to reduce the liquid dropout by vaporization. Often times the pressure in the near-wellbore region of the reservoir falls below the dewpoint pressure, while the pressure in the reservoir remains higher than the dewpoint pressure. As the near-wellbore pressure drops below the dewpoint pressure, retrograde condensation occurs leading to the formation and then the mobilization of the condensate phase towards the producing wells. The liquid phase accumulates in the near wellbore region, forming a ring, which progressively reduces the gas deliverability. This study is designed to provide an insight into the mechanism of gas injection process in reducing gas-well productivity losses due to condensate blocking in the near wellbore region. The effectiveness of lean gas, N2, and CO2 Huff n' Puff injection technique in removing the liquid dropout accumulation in and around the well bore is evaluated. Results of the study show the importance of selecting the optimum injection volume and pressure for the successful use of the Huff n' Puff process in gas condensate reservoirs. P. 119