Acidizing Performance in Hassi R'Mel Field, Algeria

Recently, matrix stimulation treatment was used for the first time in the Hassi R'Mel field in Algeria, one of the major gas condensate fields in the world, to increase the production of wells supposed to be producing below their potential, because of damaging events occurring during drilling, completion, and workovers. Acidizing jobs were conducted by three different companies. Three different kinds of mud acid system were used to stimulate a total of thirty-four wells during 1998 to 2000. In this study, the primary goal is to determine to what extent our predetermined objectives have been reached, and identify the conditions that lead to a greatest response to acidizing. For this purpose, laboratory evaluation was performed to identify formation properties and its response to different acid formulas, used or proposed by service companies. Pre- and post-stimulation engineering data were collected and analyzed. Finally, economic evaluation of each well and for the whole field is performed. The results of this study show that the reservoir was highly damaged by drilling and workover fluids. All acid formula were found to be effective in removing the damage, however insoluble precipitates capable of blocking pore throats were generated, especially in layer A. This layer of Hassi R'Mel field is described as dirty sand. Field results showed that: (a) layer A did indeed suffer production loss, (b) corrosion problems are severe, (c) chemical diversion proved to be ineffective in acidizing multi-layer wells, (d) damage is not completely removed, and (e) cleanup of wells takes long periods of time. These drawbacks can be reduced if: (a) corrosion inhibitor is used before well flowback, (b) more acid volume is injected, (c) overflush solution volume is three times the volume of main treating fluids, (d) Acid concentration is decreased, and (e) Chemical diversion is used together with mechanical diversion to treat multi-layer wells.