Summary ExxonMobil Upstream Research Company (EMURC) recently completed a subsea technology development and qualification program that included performance testing of an inline electrocoalescer device supplied by FMC Technologies (FMC). This paper will summarize the results from these performance tests. Although heavy oil has been processed onshore 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 is 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 an inline electrocoalescer device. An inline electrocoalescer device enhances the coalescence of water droplets dispersed in emulsified oils. This technology has the potential to improve the performance of the downstream oil/water separator considerably. 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 that can be separated faster and more easily in the downstream separation equipment are formed. Such a device 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 such a device 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 an inline electrocoalescer device at FMC's testing facilities in the Netherlands, with EMURC's involvement. 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 inline electrocoalescer device was evaluated over a range of oil viscosities. Water-in-oil concentration, flow velocity, upstream shear, and electrical-field strength were also varied to investigate their effects on the performance of the inline electrocoalescer device. The results demonstrate that the unit is able to deliver high preconditioning performance to medium- and heavy-crude-oil emulsions, provided that the appropriate process conditions and electrical settings are used.

In an effort to understand separation phenomena, improve separation technologies, and mitigate the uncertainty and risk associated with separator design and operation at elevated pressures, high-pressure separation tests have been conducted at 1,500 psig and 2,600 psig over a wide range of gas flow rates and inlet liquid concentrations. The tests were performed at the Southwest Research Institute® Multiphase Flow Facility using hydrocarbons ? natural gas and a liquid hydrocarbon model fluid (ExxsolTM D110, with components C12-C17). The experimental test section used during this study was equipped with compact, high-capacity separation technologies that accomplish high liquid removal efficiencies while minimizing footprint. The unit consisted of a CDS Separation Systems inline cyclonic separator for bulk liquid-phase removal and a downstream vertical separator equipped with compact internals (i.e., a vane-type inlet device, drainable mesh pad coalescer, and demisting cyclones). The design of the test skid provided significant flexibility to evaluate the performance of the separation devices alone or in combination. In this paper, the high-pressure separation testing approach, performance trends, and impact of the results are presented and discussed. Introduction Efficient gas-liquid separation is essential to the reliability and successful operation of many processes within the oil, gas, and chemicals industries. Poorly designed or inefficient separators can lead to numerous process-related issues. In gas processing, separators are used upstream of rotating equipment (e.g., expanders, compressors, turbines), contactors (e.g., glycol and amine), mol-sieve dehydrators, fuel systems and the like, and are therefore critical to preventing mechanical damage, foaming, fouling, or hydrate formation in downstream equipment. In addition, separators are important to meeting product requirements (e.g., hydrocarbon dew point) or satisfying air emissions and other environmental regulations. The importance of a properly designed separator is quickly realized as costs associated with the repair or replacement of equipment and/or gas treating solvents often far exceed the initial cost of the separator. Gas-liquid separators are designed to handle a mixed-phase inlet stream and use the density difference between the phases to drive phase separation (e.g., remove entrained liquid droplets from a gas-continuous stream). Gravity-based separators often employ more conventional demisting devices (i.e., wire mesh pads or vane packs), and therefore rely on gravity and impingement as the primary separation mechanisms. Unfortunately, conventional gravity separators, and the aforementioned internals employed within, are not always feasible. This is most evident when de-bottlenecking existing facilities (to increase throughput and/or prolong the life of the field) and in the development of resources in challenging environments (e.g., deepwater, arctic regions, or other remote fields) where vessel diameter, wall thickness, weight, or available footprint may be restricted. In such cases, more compact separator internals that use centrifugal forces to drive phase separation can be employed, such as inlet cyclones (bulk phase separation) and demisting cyclones (fine droplet removal). More recently, the demand for compact, efficient gas-liquid separation in such services has launched the development of inline cyclonic devices that employ the same separation mechanism (i.e., centrifugal forces) to achieve bulk phase separation [Fantoft et al., 2010]. Inline cyclonic separators can potentially replace larger, more conventional separators or be paired upstream of a separator to de-bottleneck existing facilities or reduce the footprint in grass-root designs (by reducing the diameter and overall height of the downstream vessel).

This paper summarizes key results of the development and verification for a subsea compact separation control system based upon a literature review, control system design, dynamic simulations, and an integrated system test. The compact separation system being considered is designed for applications in water depths up to 3,000m. The control system is a key technology element of the compact separation system, and its satisfactory performance is critical to ensure stable operation of the overall system. A thorough literature review was conducted to evaluate the control system designs for comparable subsea separation systems in industry, to understand the technical challenges, and to incorporate the key learnings into the development of this control system design. From this work, best practices were identified and were used as guidelines. A preliminary control system was developed, and the robustness of its design was assessed through dynamic simulations. Later, an integrated system test was performed with real crude and methane at realistic operating conditions to evaluate the performance of the compact separation equipment and to validate the model of the control system. The dynamic simulations and integrated system test results demonstrated the control system response following transient events, such as slugging, and provided insight into the system dynamics that then led to further modifications of the control system design and enhanced the overall system performance. This paper also delineates challenges associated with the design of a control system for a subsea compact separation system consisting of multiple, closely integrated gas-liquid and oil-water separation units. For example, the relatively small control volumes in compact separation equipment and the interaction between the different components can both add complexity to the control system design. Lessons learned from the modeling and implementation of such a sophisticated control system are discussed with the intent to serve as a reference for future subsea separation projects in the oil and gas industry.

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.

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