The naphthenate soap deposition and related formation damage in petroleum reservoirs are investigated by means of the laboratory-scale experimental and theoretical studies. Experiments were carried out in three directions to understand and quantify the naphthenate soap deposition problem. Static bottle tests were conducted to determine the precipitation rate for various pH and temperature conditions. Microscopy investigations were carried out to verify the growth of naphthenate soap particles under different pH conditions. Core flow tests were conducted to generate naphthenate soap particles and to determine the permeability impairment caused by subsequent deposition of these particles in porous media under flowing conditions and different pH values. A power-law expression was proposed and verified for the precipitation rate of the naphthenate soap particles. The parameters of the rate equation were correlated with respect to pH and temperature. This also allowed the determination of the critical pH value for the onset of naphthenate soap precipitation. The results of the particle size experiments were described by a particle growth equation and the parameters of the equation were correlated with respect to pH. The core flow experiments proved the occurrence of formation damage caused by naphthenate soap precipitation and subsequent deposition. The permeability impairment in core flow experiments was described by a new differential model. The applications presented in this study provide insights for understanding of the mechanism and magnitude of naphthenate soap-induced formation damage, and help in taking proper measures for avoiding the formation damage caused by naphthenate soap deposition.

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