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Castrol Offshore upgrades subsurface safety valve testing facility in the UK

20 October 2009

Castrol has upgraded the Sub Surface Safety Valve (SSSV) test facilities at its International Testing Facility, Pangbourne, UK, allowing subsea control fluids to be subjected to the increasingly extreme conditions found in oil and gas exploration.

In downhole completions, Castrol subsea control fluids are used to operate the SSSV, which sits in the flowing well stream and is the hottest part of a subsea system. This safety critical device acts as the final line of defense and seals the well in the event of an emergency.

Castrol's Pangbourne facility comprises two purpose-built SSSV test rigs designed to evaluate SSSV and subsea production control fluid performance at the conditions seen in the well. This means pressures of up to 20,000psi and temperatures in excess of 200C. These fixtures are manufactured to the guidelines as defined in OTO 99 001 and incorporate the port, actuator, piston and seals (static and dynamic), and return spring as used in SSSVs. Each fixture is specific to a particular model of SSSV. Castrol Offshore works closely with the main SSSV vendors; Baker Oil Tools, Halliburton and Schlumberger (Camco), and has completed HP/HT qualification testing with all of their current SSSV designs.

The industry standard test (API 14) requires SSSVs to be qualified under a "hot cyclic" test regime, whereby the SSSV will be cycled from open to closed and back again for typically 600 cycles. However the API test takes only a few days to complete and does not incorporate extended hold-open periods that are normally experienced in the field. The standard API test does not therefore evaluate the closing characteristics after long hold-open periods or the behaviour of SSSV materials such as elastomers and plastics over extended periods at temperature and pressure; nor does it consider the behaviour of the subsea production control fluid under these conditions.

Chris Morrissey, Subsea Technology Team Leader for Castrol Offshore, explained why Castrol's tests exceed the industry standard: "Many upcoming deepwater projects fall into Extreme High Pressure and High Temperature conditions (EHP/HT). Ensuring that control fluids work reliably under these extreme conditions is critical for the safety and reliability of the production system; loss of function or excessive leakage can lead to lost production, with intervention work being both difficult and extremely expensive. Tests on Castrol Offshore's SSSV rigs include cyclic and static operation of the SSSV, with monitoring of the opening and closing profiles both during cyclic operation and after long static hold-open periods. The test runs for a total of three months and includes three static hold open periods of one month. Both rigs are fully automated and have triple redundancy on the measurement system. A wide range of additional checks can be made using the extensive analytical facilities available at Castrol's International Technology Centre in Pangbourne. These include detailed fluid elemental analysis, changes in physical characteristics and full statistical process measurement. All this means Castrol can drill down to a level of detail unavailable from other subsea fluid providers."