Analytical Model for Estimation of Pore Volume to Breakthrough in Carbonate Acidizing with Organic and Mineral Acids

Abstract

Acidizing is one of the most useful methods in the oil well stimulations. This treatment technique creates capillary wormholes in the carbonate formations to enhanced fluids flow production of a reservoir. One of the main indexes for recognizing the wormhole characterization is the pore volume to breakthrough number. Therefore, calculating this number is one of the main goals in the carbonate acidizing. Obtaining this number is always required for experimental works, which needs time, energy and cost. In this article, an empirical model was used to evaluate carbonate acidizing procedure in the limestone and dolomite cores as the carbonate cores. This empirical model measures the number of wormholes formed in the carbonate cores after acid injection by using the conservation of mass law. In this method, the transport relative reaction rates of acid and core inside the structure of wormhole was maintained during the wormhole creation process. Growing the wormhole in the carbonate formation was developed step by step. Changes in acid concentration as an injected fluid flow were accounted for in this empirical model. Also, the changes in carbonate porosity, the effect of Damköhler number, and injection rate were included in the model. Two types of carbonate rocks and five types of acids with different molar masses were used in this model for the analysis and validation of the model. The results from experimental works was significance and justifies the use of use of the law for mass transport and chemical reactions. Evaluation of the developed model with other experimental and numerical results gave an excellent assessment of 95.45% for the average accuracy and 0.9933 for the average coefficient of determination. Therefore, an empirical technique to approximate the pore volumes to breakthrough number in the limestone and dolomite cores with high accuracy using physical core and acid properties is proposed.