Performance Testing of an In-Line Electrocoalescer Device with Medium and Heavy Crudes

Abstract

ExxonMobil Upstream Research Company (EMURC) recently completed a subsea technology development and qualification program which included performance testing of an in-line electrocoalescer device supplied by FMC Technologies (FMC). This paper will summarize the results from these performance tests.Although heavy oil has been processed on-shore successfully for many decades, processing heavy oil in deepwater, subsea, or Arctic fields is extremely challenging. One key challenge is oil-water separation, in which physical separation is constrained by the high viscosity of the crude and the narrow density difference between oil and water. Installing conventional electrostatic coalescers or dehydrators is often not economical or impractical at remote locations. As part of ExxonMobil's subsea program, several different separation technologies have been investigated and tested that could enable development of these fields. One example of such a technology is FMC's InLine ElectroCoalescer (IEC).FMC has developed an innovative, compact electrostatic technology that enhances the coalescence of water droplets dispersed in emulsified oils. This technology has the potential to considerably improve the performance of the downstream oil-water separator. By applying an electrical field to an oil-water mixture, the dispersed water droplets become polarized and reorient themselves in the electrical field. As these water droplets approach one another, attractive forces between the individual water droplets lead to coalescence. Larger water droplets are formed, that can be separated faster and more easily in the downstream separation equipment. The IEC can be used to increase the throughput, performance, and reliability of existing oil processing systems while reducing the energy consumption and/or use of chemical demulsifiers. In new processing systems, either subsea or topside, deployment of the IEC has the potential to significantly reduce the size and weight of the downstream separation equipment, thereby lowering the overall capital expenditure.The results presented in this paper are from performance tests that have been carried out on the IEC at FMC's testing facilities in the Netherlands, under EMURC's supervision. Extensive testing was executed with both medium and heavy crude oils. The operating temperatures were varied in a range representative for subsea processing applications, where heating of the process fluids is difficult. Thus, the performance of the IEC was evaluated over a range of oil viscosities. Water-in-oil concentration, flow velocity, upstream shear, and electric field strength were also varied to investigate their effects on the IEC performance. The results demonstrate that the IEC is able to deliver high pre-conditioning performance to medium and heavy crude oil emulsions, given the appropriate process conditions and electrical settings are used.