Formation Damage Modeling for Unfiltered Produced Water Reinjection in North-Rumaila Oilfield

Produced water re-injection (PWRI) is one of the most important management methods to dispose fluid associated with oil and natural gas production because it is economic and environmentally friendly method. However, several formation damage mechanisms are associated with the re-injection, and the most important damage is clogging of pore throats phenomenon due to the suspended particles, which will reduce the permeability of formation. Therefore, it is necessary to build mathematical model to predict the growth and extend of the formation damage in reservoir to help surveillance PWRI operations. Empirical correlation is one of the Algebraic formation damage models. Empirical model becomes important when there is a loss in detailed information about process of damage creation. In this paper, an empirical model was built to describe growth and extent of the damage in Zubair formation caused by the operation of unfiltered produced water re-injection (UPWRI) in North-Rumaila oilfield under matrix condition by using nonlinear regression tools. From growth and extent of the damage, we conclude that reinjected unfiltered produce water under matrix pressure led to large damage in Main Pay formation near and round wellbore injector because of increased volume of produced water injection. In matrix injection, the quality of the injected water must meet stringent requirements. The damage is start from maximum value (75%) at near wellbore and gradually decreases away from it. The damage zone expands symmetrical around axial wellbore injector formed circular dish that increase-by-increase flow rate and duration injection.