There are a large number of shale gas condensate reservoirs around the globe. Shale gas condensates are clean energy sources with low carbon intensity. Under reservoir (temperature and pressure) conditions, the shale condensate may remain as a gas phase. During production, retrograde condensation can occur, leading to the dropout of heavier hydrocarbons. Consequently, a condensate bank in the near wellbore region will be formed. The condensate bank may partially block the gas flow path, and hence significantly reduce the gas productivity. How to effectively remove the condensate bank close to the wellbore is becoming an important question.
A number of methods might be used to remove the shale gas condensate around the wellbore. These methods include: injection of methanol, injection of dry gas, altering rock wettability by injecting surfactant. The remedial methods involving fluid injection would be less effective for shale condensate reservoirs due to the ultra-low permeability of shale formations. In this proposal, we propose to use a drastically different approach to solve such condensate blockage issue. We will conduct reservoir-scale numerical simulations to test the feasibility of using the electrical heating method to remove the shale condensate bank in the near wellbore region. The near-wellbore region can get heated by the electrical heater that is running downhole. The heating would increase both pressure and temperature of the fluids in the near-wellbore region, which can shift the temperature/pressure conditions outside of the two-phase envelope.
The proposed research will examine the technical feasibility of wellbore heating to remove the condensate bank in shale condensate reservoirs. We will mainly rely on numerical simulations to carry out the proposed research work. The following are the detailed research tasks to be carried out:
- Select a representative shale condensate reservoir for study;
- Build an equation of state model for describing the phase behavior of shale condensate mixtures, in particular under high-temperature conditions;
- Couple the equation of state model to a compositional simulator to simulate the downhole heating process for removing condensate bank in the near-wellbore region;
- Conduct sensitivity analysis to study the influence of heating power, heating duration, and heating frequency on the condensate removal near the wellbore as well as the productivity of shale condensate wells. The sensitivity analysis will help optimize the key parameters that are affecting the process efficiency of the downhole heating for condensate bank removal.