Mitigation of Condensate Banking Using Thermochemical Treatment: Experimental and Analytical Study

Abstract

Condensate banking is a common problem in tight gas reservoirs because it diminishes the gas relative permeability and reduces the gas production rate significantly. CO2 injection is a common and very effective solution to mitigate the condensate damage around the borehole in tight gas reservoirs. The problem with CO2 injection is that it is a temporary solution and has to be repeated frequently in the field in addition to the supply limitations of CO2 in some areas. In addition, the infrastructure required at the surface to handle CO2 injection makes it expensive to apply CO2 injection for condensate removal. In this paper, a new permanent technique is introduced to remove the condensate by using a thermochemical technique. Two chemicals will be used to generate in situ CO2, nitrogen, steam, heat, and pressure. The reaction of the two chemicals downhole can be triggered either by the reservoir temperature or a chemical activator. Two chemicals will start reacting and produce all the mentioned reaction products after 24 h of mixing and injection. In addition, the reaction can be triggered by a chemical activator and this will shorten the time of reaction. Coreflooding experiments were carried out using actual condensate samples from one of the gas fields. Tight sandstone cores of 0.9 mD permeability were used. The results of this study showed that the thermochemical reaction products removed the condensate and reduced its viscosity due to the high temperature and the generated gases. The novelty in this paper is the creation of micro-fractures in the tight rock sample due to the in-situ generation of heat and pressure. These micro-fractures reduced the capillary forces that hold the condensate and enhanced the rock relative permeability. The creation of micro-fractures and in turn the reduction of the capillary forces can be considered as permanent condensate removal.

Gas Production from Gas Condensate Reservoirs Using Sustainable Environmentally Friendly Chemicals

“…The generated heat and pressure due to the thermochemical reaction will change the condensate behavior. Further, the generated pressure can induce multifractures and reduce the capillary forces [26,30].…”

“…The novelty of using thermochemical fluids for improving the gas production from gas condensate reservoirs is that the thermochemical treatment can induce a permanent improvement in the reservoir deliverability [26,30]. Thermochemical fluids are cheap, nontoxic, and environmentally friendly.…”

“…Thermochemical fluids are cheap, nontoxic, and environmentally friendly. Compared to the available techniques for enhancing the gas recovery, thermochemical treatment can reduce the operational cost up to 40% [30]. Further, the thermochemical reaction can be triggered only at the reservoir conditions, which maximizes treatment efficiency and minimizes energy loss into the surrounding formations [26].…”

“…Theoretically, thermochemical reaction can generate pressures up to 5000 psi (34.5 MPa) and temperatures up to 700 • F (644.3 K) [18]. Additionally, injection of thermochemical fluids into tight formations does not induce any damage into the reservoir rocks, and no reduction in the reservoir permeability or porosity was observed [30]. However, the main disadvantage of this treatment is that the generated pressure and heat can exceed the safe limit and may lead to undesired impacts.…”

“…Therefore, this treatment should be well-designed by calculating the generated pressure and temperature due to the chemical reaction. Then, the treatment volume and the chemical concentration can be adjusted to achieve the required and safe amount of heat and pressure [26,30].…”