Influência dos parâmetros termodinâmicos nos mapas de solubilidade dos sulfatos de bário e estrôncio

Abstract

Keeping the oil reservoir under high pressure to maximize production and prevent scale formation is a challenge for the oil industries. Generally, the water injected into the reservoirs is sea water, rich in sulphate. In the reservoir, retained in the interstices of sedimentary rocks, there is the formation water that presents considerable concentrations of alkaline earth metals, such as barium and strontium. When these two types of water mix, inorganic compounds can be formed and precipitated due to chemical incompatibility. Furthermore, variations in temperature and pressure can also lead to the formation of precipitates. After precipitation, the particles have the potential to grow in size and adhere to some surface in a process called scale formation. Oil production line stoppages caused by scale formation can result in losses in the order of millions of dollars. In the present work, a methodology that has already been used successfully to generate solubility maps for calcium carbonate is applied to barium and strontium sulphates. The proposed model presents the solubility maps of such compounds using thermodynamic equations that relate pressure, temperature and concentration. These maps were compared with a widely used industrial software called Multiscale. The present work and the computational resource use the same equations that relate the influence of temperature and pressure on solubility. The temperature and pressure range used both in the methodology and in the computacional program was from 0 to 100°C and from 1 to 100 bar. For barium sulphate, the difference between results varies from 0.01% to 11.17%. For strontium sulphate, the discrepancy of values is between 0.03% and 10.67%.