The Optimum Injection Rate for Matrix Acidizing of Carbonate Formations

TLDR

Acid injection rates that are too low waste acid at the core surface, while excessively high rates create multiple ramified wormholes, affecting carbonate coreflood performance. The study seeks to identify the optimum acid injection rate that achieves breakthrough in carbonate corefloods with minimal total acid volume. The authors develop a theory incorporating rock composition, reaction temperature, and pore size distribution to predict the optimal rate. The theory predicts an intermediate optimum rate that yields a single, small wormhole and depends on rock composition, temperature, and pore size, enabling quantitative optimization of acid injection.

Abstract

Abstract Our main result is the discovery of an optimum acid injection rate to obtain acid breakthrough in linear corefloods of carbonates using a minimum total acid volume. Low rates result in acid spending at the core surface while high rates result in the formation of multiple, highly ramified wormholes. At the optimum intermediate rate, a single, small wormhole penetrates the core. The optimum acid rate is found to be a function of the rock composition and reaction temperature as well as the pore size distribution of the virgin formation rock. All of these factors are included in the theory developed here. This theory provides a quantitative prediction of the optimum rate. The practical ramifications of the results are also considered.