Influence of acid-rock reaction heat and heat transmission on wormholing in carbonate rock

Abstract

Matrix acidizing is one of the most important technologies to recover or enhance oil/gas recovery by injecting acid fluids to dissolve rocks and increase the permeability near the wellbore. The wormholes with different patterns are generated in the dissolution process. In addition to the injection parameters, acid types and physical properties of rock, the temperature is one of the potential factors to affect wormholing performance, especially for some temperature dependent diverting acids. However, few works concentrated on the influence of reaction heat on wromholing. In this work, the acid-rock molar reaction heat considering comprehensive impact of temperature, pressure and volumetric work of CO2 was introduced into the heat transfer model, and combined with two-scale model. The models were numerically simulated to highlight the influence of different factors on reaction temperature profiles, wormhole patterns and breakthrough curves under isothermal and non-isothermal conditions with radial coreflood simulations, and the modeling results are in good agreement with the experiments. The simulation results illustrate that molar reaction heat influences the reaction temperature profile to some extent, and can affect wormholing on macro-scale under certain conditions. During the reaction, the highest reaction temperatures are observed at the wormhole tips, which are over 11 K in our simulations. Under isothermal conditions, the temperature and acid concentration strongly affect the wormhole propagation progress, but pressure does not. The field application condition of matrix acidizing considering non-isothermal Influence is also systematically studied. It was found that a colder acid injection or a lower rock temperature will promote the acidizing efficiency when the injection rate is within the appropriate range.