Improved Technique Developed for Acidizing Gas Producing and Injection Wells

Published in Petroleum Transactions, AIME, Volume 195, 1952, pages 285–288. This paper describes an improved acidizing technique which has been applied in acidizing gas wells in the La Gloria field. Wells acidized in this manner exhibited a much greater increase in deliverability than wells acidized in the conventional manner. The acid is injected into the well in small slugs separated by a small volume of high pressure gas. The acid and gas are displaced from the tubing by high pressure gas to reduce the hydrostatic head on the well when the acid is recovered from the well. The well is opened for production as soon as the acid and gas are displaced. This procedure permits a very rapid recovery of the acid which results in large increases in the deliverability of the gas wells. It has been found advantageous in the acidization of gas injection wells to inject the high pressure gas directly after the acid without backflowing the acid out of the well. This practice has made it possible to inject the gas in the injection wells of this field with a much lower pressure differential. This reduces the horse-power required to inject the gas and also decreases the number of injection wells required per reservoir. Introduction Results obtained by acidizing gas wells in the La Gloria field have varied considerably in the past. For this reason, a planned study of the acidizing procedure was undertaken in order to obtain more consistent results. The Frio Sands of the La Gloria field are rather permeable and it was not necessary to acidize many of the wells when they were originally completed. At the completion of an eight year cycling program in several of the gas reservoirs, it became necessary to recomplete many wells in other reservoirs. It was found that the open flow potential of the wells recompleted in different sands was not as large as wells that were originally completed in that reservoir. A study of the drilling records of several of these wells indicated that the sands had originally been subjected to considerable hydrostatic drilling fluid overload while the well was being drilled to the deeper sands of the field. It is indicated that during this eight year period, the drilling mud and water that were lost into the formation when the well was being drilled had formed a relatively impermeable zone around the well bore. This impermeable zone around the well bore made it very difficult to obtain high deliverability wells when the original wells are recompleted in other zones.