ExxonMobil Upstream Research Company recently completed a technology development and qualification program, which included performance tests on an integrated subsea compact separation system for ultradeepwater applications.

ExxonMobil Upstream Research Company (EMURC) recently completed a subsea technology development and qualification program which included performance testing of an integrated, subsea compact separation system with electrocoalescence for ultra-deepwater applications. To the authors' knowledge, this was the first time that an electrocoalescer had been tested with a gravity-based, compact separator (e.g., a Pipe Separator).One challenge often seen with conventional gravity separators is the formation and build-up of stable emulsion layers, mainly associated with the processing of medium and heavy oils. In an earlier test program, the Pipe Separator, the primary oil-water separator in the subsea compact separation system, performed well; however, emulsions that were not separated in the main pipes of the Pipe Separator tended to accumulate in the outlet section. There, the emulsion layer then had to either flow out of the oil outlet (penalty on the oil quality) or the water outlet (penalty on the water quality).The medium and heavy oil trials were particularly challenging, especially at lower water cuts. In order to achieve the desired oil and water qualities, the total liquid flow rate through the system had to be reduced. To overcome this limitation, additional trials were performed later with a compact electrocoalescer, the Compact Electrostatic Coalescer (CEC™) supplied by Fjords Processing (formerly Aker Process Systems), which effectively coalesced dispersed water droplets in the oil-continuous feed into larger droplets such that they could be separated easier in the downstream Pipe Separator. The results from the additional trials demonstrated that electrocoalescence enhanced the oil-water separation performance of the integrated system at flowing and operating conditions that would have otherwise been very challenging. This paper presents a summary of the results from these additional trials.The cost of developing and deploying a subsea separation system is significant; and therefore, it may not be economical if the system is unable to achieve a sufficient capacity. The design of subsea processing systems is often a balance between what is practically achievable under the module size/weight constraints, and what production rate is required for project economics. By understanding, with confidence, the maximum liquid handling capacity of the integrated system with electrocoalescence, technical risks could be minimized, and a future subsea separation project could become more attractive. As such, the results from this test program may be of interest to operating companies considering similar technologies or future subsea separation projects.Industry activity in the area of subsea processing, and subsea separation in particular, has increased over the past two or three decades, leading to a handful of applications ranging from single-phase or multiphase boosting, separation and boosting, and compression projects. While the benefits of subsea separation and boosting are generally recognized by industry, the design ...

ExxonMobil Development Company (EMDC) recently completed a qualification program which included a multiphase, subsea separation system for shallow-water applications. This paper summarizes the results from this qualification program. Developments and advances in subsea processing technologies and the application of such technologies have been fueled by recent economic considerations in the oil and gas industry, as fields are maturing and operating companies strive to maintain oil and gas production. To-date, companies have executed project-specific qualification programs which take years of upfront engineering. The intent of this qualification program was to develop subsea separation technologies for the "global" subsea portfolio, rather than a specific project. To cover the "global" subsea portfolio, a separator design was chosen that would meet separation performance targets over a wide range of operating conditions. For subsea applications, availability and reliability is critical, as unplanned intervention costs are extremely high; therefore, only certain internals were recommended to avoid plugging and fouling issues. Also, the separator was equipped with sand handling internals, including sand jetting headers and sand removal cyclones, to allow online fluidization and removal of accumulated sand. Qualification activities included the development of a subsea processing template, design validation of a multiphase separator design using Computational Fluid Dynamics (CFD) and performance tests with model fluids and "live" fluids, and performance tests on the sand handling equipment. High-level results from these tests are shared. Prior to the qualification programs, experience with subsea separation technologies, and subsea processing as a whole, within ExxonMobil was limited to being an active partner with subsea processing projects such as Tordis and Pazflor. Following the execution of the aforementioned qualification programs, technical risks have been mitigated, such that it is now possible to be confident in applying these technologies in the "global" subsea portfolio. This will enable ExxonMobil to reduce the cost and schedule impact of upfront engineering on future subsea processing projects. In the ever-changing business environment of the oil and gas industry, this may become a preferred approach to bring unproven technologies to maturity when the business need is well-established.

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