For Gas fields, sooner or later the reservoir pressure becomes too low to maintain natural flow at a satisfactory production rate. Cost efficient solutions to boost the well-stream and regain satisfactory production rates will then be required.
As a result of emerging subsea processing technology, subsea gas compression has matured as a field development element. The benefit potential of this technology is that it eliminates the need for surface production facilitates and supports production from reservoirs otherwise not seen economically attractive.
Subsea gas compression solutions are associated with substantial technical challenges. Several key components are well known from surface production applications but need to be constructed differently to meet the special subsea requirements.
Special engineering attention is needed to ensure the performance of the compressor and motor unit, the control and power distribution system, as well as other key process components such as for separation, cooling and pumping. All these elements are needed to successfully exploit the full potential of subsea gas compression.
Also Surface compression systems are relatively complex. When bringing this technology subsea it is even more important to focus on overall simplicity to ensure low cost and reliable operation.
Several gas fields have been developed and designed as subsea to shore solutions, in spite of with long distance to the processing facility. Some of the most profiled field developments are the Ormen Lange and the Snøhvit fields. The two are both developed solely as subsea to shore solutions without surface processing facilities offshore.
Sooner or later such fields will need gas compression close to their wellheads. Subsea gas compression eliminates the need for a surface facility. Hence, the potential benefit for gas fields solely based on subsea technology is one of the main drivers for the development of subsea gas compression technologies.
The second main application type is when gas is to be produced with tie-in to an existing host processing facility or pipeline with a different pressure level. Subsea gas compression could in such cases be used without any further need for modifications or pressure reduction of the existing infrastructure.
Subsea gas compression is an emerging technology that can give great benefits as a field development tool. The economical potential and technical feasibilities are such that this technology should be attractive for any potential operator.