Analyzing the factors contributing to water coning in a naturally fractured oil reservoir of Kurdistan Region of Iraq

Abstract

Production optimization in water producing oil reservoirs have always been one of the most critical challenges in the Middle East oil fields. Good evaluation of water production mechanism results in application of proper control of water production. In general, water coning is the most production problem mechanisms in the Middle East oil fields, especially in Kurdistan Region of Iraq.When excess of water production exists, the costs associated to surface facilities, artificial lift systems, corrosion and scale problems increases. Besides, the recovery factor decreases as oil is left behind the displacement front. These factors reduce the economic indicators. The drastic influence of water coning must be soon detected, and the source of such problem must be identified to apply effective and suitable techniques to control this production.Different methods have been developed to solve the problem of water coning and the success of any method depends largely on the ability to recognize the mechanism causing the water coning. This is mainly due to wellbore and reservoir parameters which can affect water coning fractured reservoirs. Without clear understanding of the contribution of each parameter on water coning, it is not possible to increase recovery factor nor optimize production.The purpose of this work was to identify by simulation the factors contributing to water coning in fractured reservoirs (1). A model was developed to represent water coning via a numerical simulation approach on a single- vertical well in an oil -water phase system using a radial cross-section model in a commercial reservoir simulator.The parametric study was performed by changing a variety of properties individually over a representative range for the fractured reservoir. The results were characterized by time to water breakthrough, oil production rate and water oil ratio. Lastly, an oil producing well with water coning issue in Kurdistan Region of Iraq was simulated and compared to the simulation work done for fractured reservoir in this research. The correlations achieved from simulation work concludes few points. First, perforation depth, perforation interval thickness and production rate are the most effective parameters on water conning phenomena. Second, water breakthrough time is not a sufficient indicator on the economic performance of the well, since the percentage of the water cut is also important. Third, natural fractures have significant contribution to water coning, which leads to less oil production at the end of production time.