Precipitation of Wax From Crude Oil Under the Influence of a Magnetic Field

Abstract

Abstract The use of magnetic fluid conditioning (MFC) technology to treat downhole wax deposition in the production of waxy crude oil has sparked considerable controversy. A variety of claims have been made about the success rate of the technology in field applications. The interpretation of results from MFC field treatments is extremely difficult, since field conditions involve a number of uncontrolled parameters, including oil composition and gas content, downhole temperature and pressure, and flow rate. In an effort to examine the influence of a magnetic field on wax precipitation from crude oil, a set of laboratory experiments was performed under controlled conditions. The experiments demonstrated that the application of a magnetic field can have a measurable effect on waxy crude oil. Properties of waxy crude oil samples, such as viscosity and wax out temperature, were measured before and after magnetic treatment. No changes in the wax out temperature were detected. Increases in the viscosity of oil samples following treatment were observed, but only when the temperature at which an experiment was performed was close to the wax out temperature of the sample. However, not all of the experiments performed near the wax out temperature of the oil resulted in measurable magnetic effects. The variability in the experimental results suggests that all of the key factors affecting the magnetic treatment process were not identified or adequately addressed. The results indicate, though, that one key factor is the state of wax saturation in the oil as it is undergoing magnetic treatment. A mechanism that may account for the magnetic effects observed in the experiments is proposed. Some implications of this mechanism on field applications of magnetic technology are presented. Introduction One of the major problems faced in the production of waxy crude oil is wax deposition in producing wells and associated piping and production facilities. A technology that has been proposed for handling wax deposition is magnetic fluid conditioning (MFC). To date, this technology has achieved varying degrees of success in field applications. Attempts to improve the effectiveness of MFC technology have been hindered by a lack of understanding of the mechanisms that may be responsible for the influence of a magnetic field on wax deposition. The scientific literature on magnetic fluid conditioning is contained almost exclusively in Russian and Chinese journals. For the most part, these papers mention some experimental evidence of magnetic treatment effects on waxy crude oils, but provide little supporting details about the experiments. Moreover, the observations are not consistent from paper to paper, and no credible explanation of the mechanisms involved in magnetic treatment is advanced in any of the papers. The patent literature associated with magnetic fluid conditioning technologies is largely US based. Although a handful of patents have been granted in which the treatment of waxy crude oils is identified as an application, a large number (more than 100) of others have listed water treatment (prevention of scaling) as the intended application. The devices for the latter application are generally similar in design to those for the former.