Improvement of acid solutions for stimulation of compacted high-temperature carbonate collectors

Abstract

The object of research in this work is the intensification of hydrocarbon production. The most problematic task of the study is the efficiency of intensification of compacted high-temperature carbonate reservoirs. Despite the gradual transition to renewable energy sources, natural gas and oil will play a dominant role in the world's energy balance in the next 20–30 years. Carbonate rocks have significant mining potential, but low filtration properties require intensification to improve reservoir permeability. High temperatures and pressures at great depths require the improvement of existing hydrocarbon production technologies. The most popular method for treating reservoirs containing carbonates is acid treatments in different variations, but for effective treatment it is necessary to achieve deep penetration of the solution into the formation. The study solves the problem of selection of effective carrier liquids for the preparation of acid solutions for the treatment of compacted high-temperature reservoirs with high carbonate content. To ensure quality treatment, acid solutions must have low viscosity and surface tension coefficient, low reaction rate, their chemical properties must ensure the absence of insoluble precipitates in the process of reactions with fluids and rocks, as well as be environmentally friendly. To select the most optimal carrier liquid, experiments were conducted to determine which candidate liquids provide the minimum reaction rate of acidic solutions with carbonates. Based on the analysis of industrial application data and literature sources, water, nephras, methanol, ethyl acetate, and methyl acetate were selected for further research. Widely studied acetic acid was chosen as the basic acid. Studies have shown that methyl acetate has a number of advantages, namely low reaction rate, low viscosity and surface tension coefficient. As well as the possibility of hydrolysis in the formation with the release of acetic acid, which significantly prolongs the reaction time of the solution with the rock and the depth of penetration of the active solution into the formation.

Chemical stimulation of geothermal reservoirs using retarded acid systems: current developments and potential directions

“…OCA was applied in France (Nami et al 2008) and Mexico (Flores-Armenta 2010). This type of ester-based retarded acid system that releases the acid in the reservoir by hydrolysis is also applied with other acids like methyl acetate in the hydrocarbon industry (Zimin 2021), but no other instances are known for geothermal applications. However, esters have a lot of potential as the hydrolysis reaction can be influenced by molecular design for an appropriate reaction speed to regulate the penetration depth (Nottebohm et al 2012) and should be considered for future developments of retarded acid systems.…”