Removal of condensate banking from different formations using thermochemical treatment

Condensate phenomenon occurs during gas production due to the reduction in reservoir pressure. In tight reservoirs, liquid banking causes an extreme damage and hydrocarbon production might be impaired due to liquid blockage. Therefore, stimulation treatments are applied to mitigate condensate damage and restore gas production. Several approaches are used to overcome liquid banking in gas condensate reservoirs. Gas recycling is one of the most effective techniques for mitigating condensate banking. However, at certain conditions, it might not be economical to use gas-cycling treatment, with the increasing demand on gas. This work investigates thermochemical treatment to remove condensate blockage from different types of formation. In this work, rock samples from sandstone, shale and limestone formations were used. Thermochemical fluids that able to generate in-situ pressure and heat were used. Coreflooding tests were carried out by flooding rock samples with thermochemical fluids. Huff and Puff injection mode was applied to remove trapped condensate. Minimum of four cycles of injection and production phases were implemented. Sufficient soaking time was applied for all samples to ensure that the reaction between the injected fluids and the rock matrix reached to the equilibrium status. Pressure profiles were utilized to indicate the equilibrium status. The impact of formation type and number of injection cycles on the treatment performance were studied. The treatment efficiency was determined based on the volume of the removed condensate and the improvements of flow condition after the treatment. The cumulative condensate recoveries were 72.97%, 68.09% and 43.38% for sandstone, limestone and shale samples, respectively. For all samples, the distribution of liquid recoveries with number of cycles are non-uniform. The incremental condensate recovery was reduced with production cycles, and more liquid removal was achieved during the first cycles of the chemical treatment. In addition, no formation damage was induced by the injected chemicals, which indicates that thermochemical fluids are compatible with the treated rocks. Reaction products of thermochemical treatment are able to stabilize the clay minerals and avoid clay swelling, particle migration and throat plugging. Overall, thermochemical treatment showed an effective performance in removing the condensate damage from limestone rocks. More than 60% of condensate banking can be removed using three cycles of thermochemical injection. In addition, the injected chemical showed minor effect on the rock integrity.