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Evaluation of Acid Jetting in Matrix Acidizing Treatments in Carbonate Reservoirs
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Various open-hole completion and stimulation designs used in horizontal wells in carbonate reservoirs cause hydrochloric acid (HCl) to be jetted onto the wellbore surface at high velocity. To properly design a limited entry liner completion and acid stimulation job, wormhole growth due to the acid jet at an orifice and skin reduction due to jetting wormhole growth must be modeled. The literature supplies adequate models of matrix acidizing wormhole growth but not wormhole growth due to an acid jet. To assist the modeling effort, previous experimental studies were conducted where HCl was jetted through limestone cores using a novel apparatus and procedure. These studies have shown that bulb-shaped cavities form at the base of cores and that dominant wormholes propagate from the base of the cavity structures. One limitation of the previous experimental studies was that interstitial velocity was allowed to increase throughout experiments and not maintained constant. For this study, the apparatus and procedure used in the previous studies were modified to conduct approximately constant interstitial velocity experiments. 15% HCl was jetted 80 ft/s with constant interstitial velocity through 4-inch diameter by 8-inch length Indiana limestone cores at room temperature. Additionally, a fitting was designed to disperse acid evenly across the core’s face in an effort to simulate a matrix acidizing with the jetting apparatus. These “non-jetting” experiments were conducted using the same conditions as the jetting experiments in an effort to have a calibrated comparison between acid jetting and matrix acidizing. These two sets of experiments were fit to a semi-empirical matrix acidizing wormhole model to gain insights into the wormhole growth behavior of the acid jetting process and its comparison to matrix acidizing. CT images of dissolution structures within cores are shown with reference to interstitial velocity to demonstrate the apparent dissolution regimes of acid jetting at various interstitial velocities and compared to matrix acidizing. Based on the laboratory, core-scale experimental acid jetting result, a theoretical, wellbore-scale wormhole/dissolution geometry is proposed and the geometry’s overall impact on apparent well skin and productivity is postulated.
Frick, Taylor Ross (2018). Evaluation of Acid Jetting in Matrix Acidizing Treatments in Carbonate Reservoirs. Master's thesis, Texas A & M University. Available electronically from