Durability and Reliability for Sea-Floor Oil and Gas Processing Equipment

Developing more efficient water processing units for oil and gas production is becoming an industry focus. Water occurs naturally within oil and gas reserves and can also be introduced as part of enhanced oil and gas recovery process. The water involved in oil and gas production is called produced water and is an undesired by-product in that industry. Both onshore and offshore produced water requires large amounts of pumping energy and the costs for water management and disposal are rising.  The problem is greatest for old wells and for offshore production. Exciting new technologies are being developed to address these issues and engineering simulation can help.

The price and demand for oil now make it financially viable to produce more oil from old fields and deep-sea reservoirs. In both cases the produced water has to be pumped to the surface and either processed for re-injection into the reservoir or disposed.  Because the produced water is contaminated with high salinity, oil and heavy metals, discharge and reuse are regulated. To address regulatory and environmental concerns and to reuse the water for enhanced oil recovery the produced water is processed using equipment that might include hydrocyclones, clarifiers and other separators.

For offshore operations there is the added complexity of transporting the produced water through miles of pipes to processing stations — usually an offshore platform or a floating production, storage and offloading unit (FPSO). This is costly since there is no profit made from the produced water.  In addition, to pump and process an ever-increasing amount of produced water can push existing processing capacities on offshore platforms to their design limit, requiring either expansion (something that was not planned for in many vessels originally designed 10 to 15 years ago) or a search for alternatives. One alternative that is gaining some viability is moving the processing unit to the sea floor.

The idea to establish equipment on the sea floor to process produced water has been under investigation for many years. Ultra-deep water drilling makes pumping of produced water to the surface extremely costly. In the Arctic, subsea installations have the benefit of longer production seasons and reduce the risk of ice formation and ice impact that affect facilities on the water surface. Making sea-floor installation of water processing equipment viable requires both that the equipment operate reliably with minimal external intervention and at low maintenance, and that disposal of the process water occur without causing contamination. These installations can have enormous impact on increasing yield from depleting oil reservoirs, improving operational efficiency by reducing equipment and piping costs, and overcoming regular slowdowns and production stoppages due to processing equipment bottlenecks. Sea-floor processing facility concepts are moving to testing and implementation stages.  Already, Statoil, Petrobras and FMC among others are testing concepts for pumping, separation and water reinjection for facilities built on the sea floor.

Engineering simulation can help companies develop current and next-generation subsea equipment for oil and gas production. The requirements for oil, water, gas and sand separation combined with the level of reliability and durability needed for sea-floor operations make use of engineering simulation solutions essential. ANSYS solutions can be used to engineer the entire system to examine all possible configurations and physical conditions that the equipment will face in the real world. Engineering new sea-floor equipment requires consideration of complex multiphase flow, thermal factors, vibration, structural mechanics, nonlinear material behavior and electronics systems —both alone and in combination. In addition, since sea-floor processing systems need to work for a broad range of conditions without operator intervention, monitoring functionality and separation methods for these new systems must be developed and perfected. It is very important to reduce equipment complexity to increase reliability. Electronic and control systems must be designed to reliably service the subsea installations. Remotely operated vehicles (ROVs) will need to be developed and deployed to build and maintain the sea-floor equipment.

ANSYS solutions are developed with these types of industry requirements in mind. Rather than a single-point solution it is possible to engineer the entire system. Using ANSYS advanced technology solutions in electronic, electromagnetic, fluids and structural mechanics each component and the full system can be optimized. Through simulation-driven product development (SDPD) many aspects of engineering analysis and design related to oil and gas production and processing equipment can be evaluated in an integrated environment using virtual prototyping long before manufacture and deployment. And, through embedded optimization and parameterization technology it is possible to develop robust designs by evaluating many parameters.  These practices lead to simple and elegant designs that will meet the quality, durability and dependability requirements of subsea projects.