Evaluation of thermodynamics effect on mineral scale formation in water injection wells supported by laboratory experiments

Abstract

Usually, some amount of unwanted water is being produced along with oil production in most of the oil fields. These waters are dangerous to environment and must be managed safely. In most cases, they are injected into water disposal wells. Scale formation and well plugging during water injection to disposal wells is a critical problem in waste water management. Main reasons for inorganic scale formation in these wells are incompatibilities of injection water and reservoir water, and thermodynamics condition variation of injection water. These mechanisms lead to the mineral scales precipitation and consequently, they are deposited in porous media which leads to injection rate reduction in water disposal wells. The critical place of scale formation is the well bottom. It is the entrance of injected fluids and commonly results in the increase of injection pressure and reduction of water injection. In the current study, the effect of pressure and temperature would be assessed on precipitation of inorganic scale by lab testing and software simulation at different mixing ratio of injection water to formation water. Also, some core flooding tests are run to evaluate the effect of deposited mineral scales on water injection process in the core samples. All input data of software modeling and core samples belong to a water injection well in a sand stone reservoir in south west of Iran.