Stimulation of Low Pressure Carbonates Reservoirs with a Triphase Emulsified Acid System "3PEA" of Southern Iran -Case Studies

Matrix acidizing tries to enhance oil wells productivity as one of the main kind of well stimulation techniques in petroleum industry. This method of acidization is being implemented by stepwise injection of high rate stimulation fluids through the wellhead into the target zone of reservoir rock. Acid penetration depth and consequently the treated radius are the key factors to reach the maximum effectiveness of stimulation operations on production improvement and it can be optimized by an exact design of: fluid type, stimulation fluid volume, job stages and operating pressure. Based on recorded data and job reports, recent conventional matrix acidizing jobs had low effect on improving oil production rate in some old Iranian oil fields, especially depleted with low reservoir pressure ones. Firstly a possible reason of this problem was assessed as shallow acid penetration radius and insufficient treated area around the wellbore and well testing data confirmed this probability. Depth of damaged zone and acid penetration directly related on the porosity type, permeability, lithology, injection rate and production history of matrix acidizing candidate wells. In this study, successful application of a new kind emulsified acid system is evaluated in a low pressure, carbonates reservoirs in south of Iran. Application of nitrogen in stimulation treatments has gained wide acceptances in recent years. The applied triphase emulsified acid increases stimulated radius of near wellbore area by retardation the reactivity of acid system by adding a gaseous phase to emulsion of HCl and gasoil. Use of this acid system made it possible to achieve a 137% greater well productivity than traditional systems, in this study.