Estimation of pore volumes to breakthrough number in limestone cores by derivation of an empirical model

Abstract

Acidizing in carbonate formations is an inevitable stimulation treatment method for oil and gas wells. In the limestone, acidizing stimulation makes capillary wormholes to increase fluids flow reservoir production. The pore volume to breakthrough number is one of the main indexes for recognizing the wormhole structure. Therefore, finding the pore volume to breakthrough number is one of the main goals in the limestone acidizing. Obtaining this number is always required for experimental works, which needs time, energy and cost. The purpose of this research is to develop an empirical method to estimate an acceptable result for this number merely by implementing limestone core and acid properties without any experimental work. In order to create a wormhole, an empirical method is developed using the law of conservation of mass considering that the core of limestone as an isolated package and the overall mass is constant in this package in the acidizing period. Also, to develop the mathematical section, the Damköhler number is used. Since this number must be calculated experimentally, a constant number is created in the model to eliminate the Damköhler number. An average accuracy of 92.31% is obtained for the developed empirical model by comparing the results obtained from the other three experimental and numerical works. This study conclusively provides a thoroughly empirical method for estimating a high accuracy of the pore volume to breakthrough number by only using known physical properties limestone core and acid.