Melhoria do cálculo da temperatura inicial de aparecimento de cristais (TIAC) para petróleo com abordagens de modelagem termodinâmica simples

Abstract

Oil reservoirs containing heavy paraffinic compounds can precipitate with decreasing temperature, forming a solid phase called wax. This wax precipitation is a problem for the oil industry, affecting all oil production steps. The wax may be deposited as a solid layer on pipes, and this layer may completely block the pipeline when not mechanically removed. Part of this solid precipitated, when not deposited, becomes solid particles through the liquid phase such as a slurry. These suspended particles increase the apparent viscosity of oil, affecting the flow. A challenge to the petroleum industry is to prevent the formation of this undesired solid and at the same time to reduce the costs with methods such as heat treatment and use of chemical inhibitors, for example, which are used to prevent the precipitation of wax. Therefore, it is necessary to specify the conditions under which precipitation can occur as a function of pressure, temperature and oil composition. Despite all the research efforts already made, there is not an ideal model or method for predicting oil wax precipitation. Many of the proposed models were used to estimate the precipitation of synthetic oils, which does not solve the real industry problem for predicting oil wax precipitation. The main objective of this work is to propose a simple and easily applied model to the prediction of wax precipitation in oil through the calculation of Wax Appearance Temperature (WAT). In this context this work proposes new simple methods for obtaining WAT, requiring few input data and without the need for complex calculations. Through the proposed methods the WAT can be estimated from data of molar fractions and molecular weights of the lighter fractions. These methods have been tested with several experimental data, obtaining good results despite its simplicity.