Browsing by Subject "reaction kinetics"
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Item A Novel Model for Fracture Acidizing with Important Thermal Effects(2013-12-05) Lyons, JohnFracture acidizing is a well stimulation technique used to improve the productivity of low-permeability reservoirs, and to bypass deep formation damage. The reaction of injected acid with the rock matrix forms etched channels (that depend on injection rate, mass transport properties, formation mineralogy, reaction chemistry of the acid, and temperature) through which oil and gas can then flow upon production. The use of a model that can effectively describe fracture acidizing is an essential step in designing an efficient and economical treatment. Several studies have been conducted on modeling fracture acidizing, however, most of these studies have not accounted for the effect of variation in acid temperature (by heat exchange with the formation and the heat generated by acid reaction with the rock) on reaction rate and mass transfer of acid inside the fracture. In this study, a new fracture acidizing model is presented that uses the lattice Boltzmann method for fluid transport and takes into account these temperature effects. The lattice Boltzmann method incorporates both accurate hydrodynamics and reaction kinetics at the solid-liquid interface. This method is also well known for its capability to handle re- active transport in complex geometries. This enables the method to model realistic fracture shapes, on a pore-scale level, and predict the shape of the fracture after acidizing. Results of carbonate fracture dissolution with and without the thermal effects are presented. It is found that including thermal effects alters the predicted shape of the fracture after acidizing.Item The Influence of Equilibrium Reactions on the Kinetics of Calcite Dissolution in Lactic Acid Solutions(2014-08-07) Shedd, Daniel CMatrix acidizing has historically been a common means of removing formation damage and increasing the productivity of petroleum wells. Organic acids have been used in an effort to minimize the corrosion problem and the rapid reaction rate encountered when using strong acids, such as hydrochloric acid (HCl). The reaction of an organic acid with carbonates is reversible and thermodynamically limited by the presence of reaction products. This thermodynamic limitation must be considered when studying the reaction kinetics of organic acids with carbonates. A kinetic model was developed to account for both the equilibrium reactions on the rock surface and the mass transfer of the reactants and products. This study provides both mass transport and reaction kinetics parameters, which can be combined with the reservoir temperature to determine treatment duration or soaking time. While lactic acid has been used successfully in the field, having a more detailed knowledge of the reaction between lactic acid and calcite will allow for optimized treatment design. The kinetic model was also used to isolate the contributions of the transport of reactants, the surface reaction, and the transport of products to the overall resistance of the reaction. At all temperatures investigated, the transport of products away from the surface represented the largest contribution to overall resistance. A coreflood experiment was also performed to observe and confirm the wormholing tendencies of lactic acid in calcite. Lactic acid formed a single dominant, minimally-branched wormhole through the core.