Avaliação de mecanismos de interação do ácido aminofosfônico com mineral constituinte da rocha arenítica berea: Feldspato

Abstract

Incrustations cause many operational problems in petroleum industry that occur in some moment of wells productive life, most frequently because of seawater injection for pressure maintenance and oil recovery. The formation and deposition of insoluble inorganic solids occur because of the difference of salinity between formation water and injection water (seawater) or because of changes in flow system conditions of reservoir and production. The squeeze technic is used to prevent scale formation, which consists in inhibitor retention by the formation rock through adsorption and precipitation, which avoid precipitate formation. Studying the interaction between the incrustation inhibitor and the rock formation, it has been performed batch tests with Feldspar and Quartz, that occur on sandstone Berea, and nitrilotrismethylenephosphonic acid (NTMP) as inhibitor. The batch tests have been performed in NTPM solutions with NaCl 1M and in artificial brine on temperatures of 25 and 70°C, pH 4 e 7, with contact time of 48 hours. In these tests, the influence of temperature, pH and inhibitor concentration were verified. Testing the mixture between two minerals, it was concluded that was possible to obtain the retention curve of mixture from the minerals individual curves. The samples were centrifuged and the NTPM final concentration was analyzed by the technique of optical emission spectroscopy inductively coupled plasma (ICP-OES). The results have shown that the biggest NTPM inhibitor occurs in saline solution of artificial brine at pH 4 and 70°C, controlled by precipitation method. It was observed the precipitate formation on pH 7 before the contact time with the rock, because of the formation of the complex cation-NTPM. In saline solution of NaCl 1M, the precipitation is the dominant method in pH 4, the adsorption of inhibitor decreases as pH increases due to increased level of electrostatic repulsion. In all the cases, the temperature increment of 25°C for 70°C promoted bigger inhibitor retention. It was verified that the method of prediction of the retention curve for a mixture of adsorbents from the individual curves was not valid for the mixture of minerals Feldspar and Quartz.