David B. Allison

An Overview of HF Acid as Applied to the Wilcox Sand in Reddell Field, Southwest Louisiana

The Wilcox reservoir in South Central Louisianas Reddell Field has responded quite favorably to slow-reacting HF acid treatments. A historical perspective. dating back to 1981. is the basis for the comparison of traditional HF acid (12% HCI - 3% HF) systems to that of the slow-reacting HF acid system. These documented benefits are listed below: . Two- to four-fold production increase . Accelerated recovery of well production . Reduced workover fluid recovery time from 24 months to 2 months . Increased success rate associated with stimulation from 40% to 90% The improved performance was achieved because of careful attention to reducing chemical incompatibilities. Separation of the HF fluids from the potassium chloride workover fluids and the proper choice of HCI-HF concentrations for the Wilcox formation mineralogy dramatically reduced secondary plugging from the HF treatment. This paper discusses Wilcox formation mineralogy and its susceptibility to formation damage. In addition the paper compares conventional acid treatments to slow-reacting HF acid treatments. Finally, criteria are suggested regarding applications of HF acid for similar formations.