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, andcuring. 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
Severe emulsion upsets in surface treating facilities following acid stimulation frequently occur after production from the stimulated well is commingled with other production. Preventing such upsets requires using optimum demulsifiers at high concentrations and eliminating, or at least minimizing, the formation of precipitates. Introduction Frequently, severe emulsion upsets occur in surface treating facilities following acid stimulation. Such upsets usually occur after production from the stimulated well is commingled with other production from nonstimulated wells. These emulsions have been extremely difficult to treat and have resulted in loss of considerable oil produced as an untreatable emulsion and a reluctance, in some areas, to use acid stimulation. Results presented in this paper show that acids partially spent on formation solids contain, in solution, potentially precipitable materials. As the pH of the produced acid precipitable materials. As the pH of the produced acid increases upon commingling with other production, fine solids are precipitated; these solids are capable of stabilizing extremely tight emulsions. The stability of such emulsions is far greater than that of emulsions stabilized by fine particles loosened from the formation or by oil-wet formation particles loosened from the formation or by oil-wet formation particles. Preventing upsets in the field requires using particles. Preventing upsets in the field requires using optimum demulsifiers and eliminating, or at least minimizing, the formation of precipitates from partially spent acids. Examples are given for handling such problems in the field. A novel technique for the reproducible formation and the study of emulsions in the laboratory is presented. The use of the technique in selecting optimum demulsifiers for the field is described. Background Historically, emulsion treatment has played a significant role in petroleum production. Much of the world's oil is produced with water and, in many cases, stable water in produced with water and, in many cases, stable water in oil emulsions occurs. An entire technology has been developed for treating such emulsions. Types of treatment include thermal, electrical, and chemical treatments. Most oilfield emulsions are stabilized by small amounts of naturally occurring, surface-active materials present in either the oil or the water, and usually can be treated with nominal amounts of chemicals or by other means. Such emulsions generally are observed at the wellhead and are believed to form either in the wellbore or in the formation. Emulsions observed following acid stimulation are significantly different. First, they do not always show up at the wellhead, but generally form only after production from the acid-treated well is commingled with production from untreated wells. Second, they are extremely difficult to treat requiring either large amounts of chemical demulsifiers or unusually long separation times. Such emulsions are a particularly serious problem in offshore operations, where it is usually impractical to separate production from individual wells and where an entire production from individual wells and where an entire field's production may be commingled before treatment. Emulsion upsets under such circumstances can result in thousands of barrels of nonpipeline-quality oil. The problem has been particularly acute in Gulf Coast fields, problem has been particularly acute in Gulf Coast fields, but also has been noticed recently to a lesser degree in production from offshore California. As more production production from offshore California. As more production comes from offshore and more acid stimulation is used in such areas, occurrence of severe emulsion problems can be expected to increase. The work reported here was related to sandstone acidizing with HC1-HF acid. JPT P. 1060
The a-c and d-c resistances for tetragonal zirconia were measured over the temperature range of 1100~176 and pressure range of 1 to 10 -14 atm oxygen. Polarization studies indicated that in oxygen atmospheres an oxygen electrode reaction occurs at the platinum-zirconia interface so that it is not possible accurately to separate ionic and electronic conduction components from the resistance data. However, the data do indicate a significant ionic conduction component within the pressure and temperature range studied. Assuming that oxygen transport accounts for the ionic conduction some order of magnitude values for oxygen diffusion in zirconia at 1400~ were calculated.Most chemical processes of interest in the fabrication and use of materials at high temperatures involve heterogeneous systems, and the kinetics of these processes are more often than not transport-controlled. However, experimental data on high-temperature diffusion processes is very limited, and we are not yet able to predict transport behavior.In conjunction with recent studies in our laboratories, on the kinetics of oxidation of zirconium carbide and boride in the 1000~176 range, we desired data on the mass transport properties of the ZrO2 that can form as a surface coating during the oxidation process. In particular, information was sought on the diffusion of oxygen, the defect structure of the oxide, and the effect of temperature, atmosphere, and impurity content on the defect structure. As a result of this interest, we initiated a study of the a-c and d-c electrical conductivity of tetragonal zirconia in an attempt to provide some of the desired information.From a-c and d-c resistance measurements we expected to be able to calculate transport numbers and separate ionic and electronic conduction components. From accurate knowledge of these components a defect structure model can be developed. In addition, knowledge of ionic conduction will permit the calculation of diffusion data for oxygen, providing that oxygen is the only ionic species contributing significantly to the ionic conduction.Previous work on tetragonal zirconia has been extremely limited. Kofstad and Ruzicka (1) found that the direct current conductivity of tetragonal zirconia had a complex oxygen dependence. They proposed as a possible explanation for this behavior that zirconia is an ionic conductor with a coupled transport of oxygen vacancies and interstitials and pointed out that to confirm this explanation it would be desirable to study the relative importance of ionic and electronic conduction as a function of the partial pressure of oxygen. Vest and Tallan (2) have been studying tetragonal as well as monoclinic zirconia concurrently with this study utilizing a polarization technique. Their results have not yet been reported in detail.
In many oil producing reservoirs, sand and other fine-grained rock materials migrate into wells. This influx may decrease oil production by plugging gravel packs, eroding well equipment or completely sanding up wells.In many such problem formations, the principal natural cementing agents are clay minerals, which are relatively weak and may be further weakened by changes in formation fluid chemistry.When these clay minerals expand and disperse, the coarser silt and sand in the formation rock may also move in with flowing fluids and damage the well. This paper describes a procedure for treating such formations with hydroxyaluminum to stabilize clay minerals and thereby prevent sand and silt production. AIQKM. G-RFFD and CLAUDE P. COPPEL 5
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