Development and Qualification of a Subsea Compressor

摘要

Oil and gas production in the Norwegian Sea has been ongoing for decades. The Åsgard B platformrnproduces gas and condensate from the Mikkel and Midgard reservoirs from subsea wellheads with 50 torn80 km long pipeline tie-backs. Because the production started to decline, several innovative technologiesrnwere investigated to extend the production and increase the total recovery from the field. Artificial lift, byrnapplying compressors installed on the seabed close to the wellheads, was the most favorable solution. Anrnall-electric hermetically sealed integrated motor-compressor was selected to fulfil this duty and anrnextensive technology qualification program over 10 years was initiated.rnMachine qualification activities included both component and full scale testing levels with the aim tornarrive at a low risk subsea compressor solution with utmost robustness and reliability. The componentrntesting level placed major focus on screening available materials to withstand exposure to the rawrnwellstream fluid from the Åsgard field. Full scale motor compressor testing was performed in a dedicatedrntest facility with hydrocarbon fluids to investigate overall machine performance and enhancement via thernintroduction of new machine components from the material screening testing.rnValuable operational experience from the qualification efforts were collected and used to establish therndesign and material selection boundary conditions for the final dedicated subsea compression solution. Arnparticular negative operational experience was fouling induced machine thermodynamic and rotordynamicrnperformance degradation and the need to introduce integrated online washing and machine wet gasrncompression compatibility to reduce operational risks. To preserve machine robustness and mitigaternpotential corrosion and erosion problems, a machine concept with unconventional low operating speedrnand enhanced materials was selected. The world’s first subsea compressor with the above conceptrnattributes was successfully manufactured, tested, installed, and operated subsea at a depth of 260 meters.rnThe qualified machine has been designed and tested for presence of free liquids such as water,rnhydrocarbon condensate, and glycol in the gas stream and demonstrated full capability to operate withinrnthe complete compressor performance map with liquid content exceeding levels found in normalrngas-condensate fields. An available high performance wellstream compressor can reduce the complexityrnand cost of future subsea compression systems.