Introducing a New and Practical Method for Determination of the Critical Flow Rate in Carbonate Reservoirs

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; this is especially true in high clay content، low permeability، and poorly consolidated reservoirs. The formation damage could be both temporarily، by exceeding the turbulent limit of fluids in porous media، and permanently، by fine and sand production or fissure and fracture activation; because of this overall pressure drop will be noticeable in near wellbore. Since the carbonate formations are stronger than sandstone formations، the results of velocity formation damage are different and comparable with results of sandstone formations. In this study، a series of core flooding experiments have been carried out to determine the critical injecting flow velocity in porous media of the carbonate formation by the use of a new and practical method. The formation damage limits in linear system were determined by both qualitative and quantitative methods for different plugs. The proposed method incorporates two different methods، one of which uses base line permeability and returning the injection rate to base rate after each incremental stage and the other determines formation damage degree. The results show that the induced damage mechanism is in the form of fine migration or activation of natural fractures and، to prevent formation damage، the injecting flow velocity must be kept less than its critical value. Otherwise، the induced damage will be permanent and irreversible.