Quantifying alkaline sensitivity of Fahlyian Formation by alkaline flooding and formation damage evaluation

Secondary and Tertiary recovery processes can lead to severe and permanent reductions in permeability due to the interactions between injected fluids and the reservoir rock that is especially true in high clay content, low permeability, poorly consolidated reservoirs. After the fluid with a high pH value enters the reservoir, the texture of clay minerals and siliceous cement in the reservoir is destroyed due to the dissolution of clay minerals and cement and the release of fine particles produced, thus causing reservoir plugging. Formation damage could be both temporarily due to the precipitation of reaction products caused by interaction between high pH fluids and reservoir rock which will result in pore plugging.In this study, a series of core flooding experiments have been carried out to determine the critical pH of Alkaline fluids for plug samples of Fahlyian carbonate formation. Alkaline fluids with different pH (7, 8.5, 10 and 12) were injected into plug samples and the alkaline sensitivity of the carbonate formation has been measured in both qualitative and quantitative forms by a new applicable method. Using this approach will result in the accurate estimation of the degree of formation damage. Results indicate that used plugs show different behavior when exposed to fluids with different alkalinity and the degree of resulted formation damage varies from zero to serious and in certain cases are noticeable and Irreversible. Therefore, pH of injecting fluids must be kept less than its threshold value to prevent formation damage.