Modeling acidizing of carbonate formations with different reservoir properties

Abstract

Introduction. The efficiency of matrix acidizing of the bottom-hole formation zone depends on many factors, the chief being the reservoir properties. The research aim is to assess the effect produced by the formation reservoir properties on the result of hydrochloric acid treatment. Experiments simulating carbonate formation acid treatment were carried out. Methods. The experiments were carried out using the UIK-1 core analysis apparatus. Carbonate cores with different porosity and permeability were selected. Some of the experiments modeled permeability reduction as a result of bottom-hole formation zone contamination with drilling mud. Results. The research has shown that during low permeability reservoirs acidizing, permeability increases to a greater extent than during high permeability cores acidizing. In low permeability cores, the acid solution mainly forms new channels, while in high permeability cores the expansion of existing ones mainly occurs. In the present paper, the equivalent surface area of the acid-formed channels was estimated. When acidizing low permeability cores, the equivalent area of the channels is larger than when acidizing high permeability cores. The outcome of acidizing of the core samples with impaired porosity and permeability and contaminated with model drilling mud is comparable to acidizing of low permeability samples not contaminated with drilling mud. Conclusions. Acidizing of low permeability reservoirs leads to a greater increase in permeability. The equivalent area of acid-formed channels is larger than that of high permeability cores treatment. This reveals that the impact of acid on low permeability reservoirs is more effective.