Industry collaboration works to advance subsea processing technology

Roy Long
US Department of Energy

Improving safety, reliability, and performance indeepwater development are the principle goals of the US Department of Energy Office of Fossil Energy's (DOE) implementation of the Energy Policy Act of 2005. The program, created by an act of Congress and administered by the Research Partnership to Secure Energy for America (RPSEA) under the direction of DOE's National Energy Technology Laboratory (NETL), funds research, with additional funding and research by industry and academic partners, in technologies key to ensuring a secure energy supply for the United States.

Research in subsea production and processing has been an important component of the program. Within the deepwater program, a series of projects undertaken jointly by RPSEA and GE have worked to develop subsea processing technology to lessen the need for deepwater surface production facilities and extended tiebacks.

The program began with development of a process simulation tool designed to modelsubsea processing systems (SPS) for oil and gas. The intent was to provide an industry standard to evaluate SPSs performance, and to help bridge technology readiness level (TRL) gaps between operation engineers and facility suppliers. The program deliverables included simulation architecture, a functional simulator, procedures and documentation, experimental validation, and experimental facility availability.

The program's key objectives included:

Objective 1. Develop a library of robust analytical unit models, with standardized interfaces, for compact separation devices operating in a subsea multi-phase flow environment. Standardized unit models allow the buildup of complex systems.

Objective 2. Develop a robust process simulator combining the analytical unit models from Objective 1 to provide for the following major features:

• Prediction of both steady-state and transient performance
• Expandability at the component level to accept more accurate analytical component descriptions as they become available from ongoing research and experience
• User configurability
• Interface with existing upstream industry-standard production simulators.

Objective 3. Develop a lab-scale test facility and testing protocols for the validation of both the analytical models and the simulator performance. This objective has importance for both developing unit models and validating the resulting system models, as well as the processes and methods used therein. This objective was accomplished through the creation and use of a test loop facility. The chosen test case is a horizontal three-phase (saltwater/oil/gas) gravity separator.

Objective 4. Develop a methodology and associated procedures for using the simulator to determine the operational envelope for various process designs. This was achieved through the development of a statistical methodology and toolkit in MATLAB, the technical computing language and interactive environment for algorithm development and data analysis.

Objective 5. Using the lab-scale test facility and protocol, simulator performance was validated by executing a test plan for evaluation over a wide range of conditions:

• Operating envelopes
• Transient stability
• Process control logic.

Using the simulator to model various components of SPSs resulted in several research and development projects, among them the design of subsea electrical provision and distribution systems to power subsea processing components.