Determining Acid Distribution Using Distributed Temperature Measurements
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AbstractPlacement of a sufficient volume of acid in all desired zones is critical for a successful acid stimulation treatment. Particularly in thick, highly heterogeneous carbonate formations, the acid distribution is crucial for optimal stimulation results. A variety of diversion methods are applied in acidizing treatments to evenly place acid along the well, but the effectiveness of these diversion methods is generally only inferred from the rate and pressure behavior during the treatment, and is not known with any certainty. It would be extremely helpful if the acid distribution could be measured.We developed a model to simulate the temperature behavior along the wellbore during acid injection and during the flow back period following an acid stimulation. An important phenomenon in this process is the heat generated by reaction, the key factor enabling the interpretation of the acid distribution from the temperature profile. We have developed a mathematical model that describes the coupled flow and heat transfer process. The flow system consists of a near wellbore formation with a wormhole region and a spent acid region. Wormhole propagation and the spent acid front are simulated as a function of acid injection volume (time). The thermal model includes conduction, convection, and reaction heating to seek the connection between acid volume distribution and temperature profile. The result of the thermal model showed significant temperature effects caused by reaction. During flow back, the zone that took more acid volume would have created more heating because of reaction, providing a mechanism to quantitatively determine the acid flow profile.
