Field Results From Wells Treated With Hydroxy-Aluminum

Abstract

More than 200 wells have been treated with hydroxy-aluminum to stabilize reservoir fines. There have been many outstanding successes and few well defined failures. For wells whose production declines rapidly after acid stimulation, for wells that sand up, and for steam-stimulated wells in water-sensitive formations, hydroxy-aluminum could be the best solution. Introduction New, effective well treatments to prolong the economic production of wells in the U.S. are vital to the domestic gas and oil industry. Field results show that the hydroxy-aluminum process is such a treatment. Nearly all gas and oil formations contain clay minerals of different types and in various amounts. Serious permeability decreases occur when clay minerals obstruct flow by either dispersing and lodging in restrictions or expanding to fill pore spaces. In many sandstone formations, clay minerals are the principal cementing agents for sand and silt grains. A clay-mineral fabric can be weakened by changes in water saturation or composition, by treatment with acids, and by many other materials now used in well treatment and maintenance. The formation then becomes less competent and may start to erode or flow. Reed reported that hydroxy-aluminum (OH-Al) stabilizes formation clay minerals against dispersion and expansion. This prevents permeability caused by migrating and expanding clays. Reed and Coppel found that in certain formations if the clays are treated with OH-AL to make them more resistant to changes in water composition, the sand and silt fractions becomes less subject to erosion. Refs. 2 and 3 dealt primarily with laboratory work; they described the effectiveness of the process for clay stabilization, defined the critical process variables, and discussed sand stabilization. The purpose of this paper is to present the results of extensive field testing of the hydroxy-aluminum process in several types of applications. The Hydroxy-Aluminum Process Description of the Solution Hydroxy-aluminum is a low-cost, inorganic polymer that is available commercially. It can also be successfully prepared in the field in large quantity by reacting aluminum chloride and sodium hydroxide in a high-shear mixing device. It is a slightly acidic, nonhazardous chemical and no unusual handling procedures are required. Details of its chemistry and interactions with clay minerals are given in Ref. 2. Job Design In designing a job, two things must be considered, the process steps and the liquid volumes. process steps and the liquid volumes. The process, for most field applications, consists of the following three steps: injecting the hydroxy-aluminum, overflushing to displace the hydroxy-aluminum, and curing. The hydroxy-aluminum is injected for the purpose of bringing it into contact with the clay mineral surfaces. In the field tests to date, it appears that this can be accomplished in the formation without the need for special solvents or wetting agents. The purpose of the overflush is to assist in placing the hydroxy-aluminum and to remove excess placing the hydroxy-aluminum and to remove excess hydroxy-aluminum from the pores. JPT P. 1108