A new approach for the demonstration of acidizing parameters of carbonates: Experimental and field studies

Abstract

Acid stimulation of carbonates is the most common method of production intensification in practice of hydrocarbon field development. Injection of acid compositions improves hydrodynamic connection of the wellbore with the reservoir by creating extended filtration channels – wormholes. Wormholes increase the effective drainage radius of production wells, which provides incremental oil. Scientists around the world have conducted a considerable amount of experimental and numerical research at the fundamental level aimed at studying the complex process of interaction of acid compositions with carbonate rock. The results of the studies repeatedly noted the critical role of technological parameters of acid treatment, the competent choice of which often provides a positive result of stimulation. However, a significant number of studies have been performed and tested only at the theoretical level or under ideal laboratory conditions, and their transfer to real heterogeneous productive reservoirs turns out to be a failure. Our study demonstrated a fundamentally new approach to justify the technological parameters of acid stimulation of carbonates (volume of acid and reaction time) based on laboratory experiments and field studies. We developed a rating matrix that characterized the effectiveness of acid treatments in terms of changes in well performance and reservoir properties, as well as the multiplicity of exposure, for a wide range of technological parameter changes. The application of this approach allows not only to evaluate the effectiveness of actually performed acid treatments, but also to quickly determine the perspective of different design options for future interventions. The operability of matrix was confirmed by positive pilot tests at wells in Perm Krai (Russia), and the test results were 8–31% higher than the planned results. The algorithm we described was useful in designing acid treatments. This method effectively improved the oil and gas recovery under the condition that the reserve structure deteriorated annually and the number of candidate wells decreased.