ResumoEstudou-se a utilização da escória de cobre de uma fundição do Chile na fabricação de argamassas de cimento. A escória foi caracterizada através de análise quí-mica, mineralógica e granulométrica. Também foram usados diferentes padrões para se conhecerem alguns parâmetros importantes da escória e se fazerem os ensaios de compressão e de flexão das argamassas. Os resultados mostraram que as argamassas feitas com escória de cobre apresentaram maior resistência à compressão e à flexão que as preparadas com areia. O estudo conclui que esse resíduo metalúrgico poderia ser utilizado na construção civil. Palavras

Low crude oil sweep efficiency may be the result of channeling of injected water through high permeability sands in heterogeneous reservoirs. In these cases the efforts have been focused in improving the distribution of injected water in the wellbore through treatments using cements, gelling agents, and other short radius plugging materials. It has been proven that such treatments contribute to a better water distribution in the formation around the wellbore However, they are unlikely to be completely successful because, deeper in the formation, the fluid may divert. Laboratory and field studies have suggested that oil-in-water emulsions can be used to obtain a deeper formation plugging and this results in better sweep efficiency and a greater oil recovery. However, the suitability of this method for fractured formations remains relatively unknown. This paper presents the second phase of a three-phase study. The first phase consisted at the formulation of a heavy oil-in-water emulsion. Alkaline solutions were used as emulsifier agents. Parameters such as alkaline solution type and concentration, oil/water ratio, and shear rate were optimized in order to obtain a stable emulsion with an average drop diameter of 3 m. The second phase comprises the laboratory evaluation of the plugging effectiveness of the emulsion. The third phase will address the development of a field-pilot test. In order to accomplish the second phase objective, coreflood experiments were conducted at 80 C, with a confining pressure of 3000 psi and an injection pressure of 1000 psi. Various types of cores were used, including some with a longitudinal fracture. It was observed that an undesired breakdown of the emulsion generates plugging at the core injection inlet. A flush with an alkaline conditioner is required to minimize the breaking of the emulsion before it enters the cores. This preflush has no effect on the core permeability. Externally produced emulsions injected into the cores after the pre-flush with the alkaline conditioner reduced the permeability up to 80%. No time degradation on the emulsion plug was observed even after 27 PV of water injected. Introduction A number of studies has proved that oil-in-water (o/w) emulsion can cause permeability reduction. McAuliffe postulated and tested in parallel cores experiments that o/w emulsions would enter the most permeable layers of the reservoirs, where it is trapped. The trapped emulsion creates enough blockage for the water injected afterwards, resulting in a diversion process the improves the overall oil recovery. Considering an initial situation where three oil bearing layers (A, B and C) are waterflooded If one of these three layers (A) has higher permeability than the other two, most of the injected water should flow through it sweeping the oil, but leaving the other two layers (B and C) unswept. After the blockage of layer A with an emulsion, layers B and C can be swept, increasing the recovery of oil. The only field pilot test of this process was conducted in the Midway Sunset field, California. P. 611

Ethylene-propylene-diene monomer (EPDM) rubbers used in electric submersible pump (ESP) cables were analyzed after being aged in actual operation conditions in oil wellbores. These rubbers constitute the insulation and jacket layers of the ESP cables. EPDM rubbers from four different cables operating during different time intervals (2 and 4.8 years) at different depths (from 760 to 2170 m) below sea level were studied. To verify the effects of the long exposure on the rubber performance, thermal analysis was performed to determine the thermal stability and activation energy of degradation. In addition, structural analysis, through vibrational spectroscopy and crosslinking fraction assessment, was carried out. The mechanical properties of the aged rubbers were inferred through the measurement of hardness, while the absorption of a service fluid was studied by gravimetry. The results showed only minor changes in the thermal, structural, mechanical and barrier properties of the EPDM-based ESP cable layers. It is suggested that the thermo-oxidation mechanism followed by chain scission does not have a role in the degradation of EPDM within the aged ESP cables, and no sign of variation of crosslink fractions has been encountered. Therefore, it was concluded that EPDM-based layers seem not to be weak links in the configuration of modern ESP systems.

The precipitation of inorganic compounds by cation hydrolysis could be an alternative method to modify injection and production profiles. The precipitation in porous media can be caused by a pH increase as result of fluid-rock interactions, direct neutralization with base or thermal decomposition of a basic precursor, placed as additive. This paper ascertains the effects of precipitant solutions of zinc or aluminum salts, plus urea as basic precursor, on permeability, at reservoir conditions. Flow tests were conducted in 30 cm Berea cores, at 140°C, 800 psi. Different injection schemes were tested, varying the number of precipitant solution batches, i.e. 1 and 2, and the shut-in time, i.e. 24 and 48 h. After that, fresh water was injected to determine permeability reduction, as well as the effect stability, along the core and in 3 sections of 10 cm each. The results show 98% as maximum permeability reduction located mostly in the inlet section, while in the outlet section the maximal reduction achieved was 80%. In all cases, the effect was stable for at least 10 PV of water injected. Furthermore, permeability was not restored by 0.1 N HCl solutions. Precipitation occurs at T>70°C; it takes 2–4 hours at 80°C, and 40 min. at 140°C; enough time for the placement of the solution into porous media. Scanning electron microscopy images of the treated Berea cores demonstrated different shapes of particles precipitated, depending on the cation; all of them reduce permeability by filling the porous space. The aforementioned results show that in-situ cations hydrolysis induced by basic precursor have the potential to modify injection and production profiles in the field, with some possible placement advantages. Introduction Water injection profiles and production water are important factors that require optimization during the life of the enhanced oil recovery projects. They have incidence in oil producing rate and costs for treatment-disposal of produced water. Once water breakthrough, preferential flow channels form leaving oil-saturated areas not contacted by the displacing fluid. In such cases, high permeability areas must be isolated or sealed in order to divert injection fluids towards oil bearing zones. Commonly sealing chemical technologies include gels1,2,3 and cements4,5. Nowadays, research on alternative technologies is looking for lower formulation and operational costs and placement advantages. Among these technologies is cation in-situ precipitation, subject of this paper. The precipitation of NaCl and KCl by salting-out effect has already been evaluated in porous media at reservoir conditions. Although significant permeability reduction can be achieved, the final effect is not stable to water flow; in addition, the brines used can induce corrosion6. Other approach considers precipitation of hydroxides and oxyhydroxides by cation hydrolysis, either by addition of an alkali to metal salt solutions or by reaction of these solutions with carbonate minerals7,8. Lakatos et al.9 tested an iron hydroxide-based application in injector and producer wells in Algyö field, Hungary. Treatment scheme consisted in the neutralization, inside porous media, of acid solutions of FeCl3 by sequential injection of K2CO3. Preliminary evaluation of the results pointed 60% technical success and 40% of the treatment profitable, making the technology very attractive. However, the above procedure may drive to precipitation in a relative small mixing section, yielding low efficiency treatment. On the other hand, the method based on the reservoir rock carbonate content is of limited application, and it could have competition between channel formation due to dissolution and pore plugging due to precipitation. In order to achieve full precipitation and plugging of the whole flooded section, basic precursors may be appropriate to use. These compounds hydrolyze under certain conditions of temperature, changing pH of medium and inducing precipitation by cation hydrolysis.

No abstract