Subsea Well Fluid Intervention Using MARS (Multiple Application Reinjection System)

Abstract

Subsea Well Interventions offer many challenges. The population of subsea wells is now in the region of 4000 and is anticipated to continue to grow, with expansion into deeper waters and more hostile environments. Historically, the cost of intervention on subsea wells has negatively influenced its uptake; however, this is changing with advancing technologies, as operators seek to improve recovery from their subsea assets. Fluid intervention does not require vertical well access for wireline or coiled tubing services: it involves pumping chemicals into the well in a controlled, safe manner. There are a number of fluid intervention applications, examples of which are: to protect the well against scale and hydrates; pumping of kill weight brine for the purposes of well control; cleaning the lower completion or stimulating the reservoir to tackle formation / production issues that can evolve throughout the life of the well. In 2008, an operator in the North Sea utilised the first MARS based subsea well intervention system, to carry out scale squeeze operations in the on a North Sea field from a DSV. Further successful campaigns have been completed in 2009 and 2010 in addition to a 10,000 psi system being ordered for other fields. By adopting a standardised method for scale squeeze operations, Shell has been able to reduce the cost and maximise the efficiency of their operations. Subsequently an operator in Angola has adopted the same philosophy for their subsea field while considering additional MARS options for well sampling and metering; successful operations where performed in 2009 and 2010 and 2011, allowing continuous production while reducing the cost of intervention. A major project in the Gulf of Mexico has been sanctioned where the technology will be used also. This paper will describe the operational and cost benefits of utilising MARS for subsea well intervention and update on the operational performance of this methodology as it matures. . Multiple ApplicationsMARS is a production optimization technology that establishes the wellhead as the unit of production, enabling processing equipment to be mounted directly onto production trees. The principle is simple: by introducing a coaxial flow path insert into the tree, well fluids are directed externally to a flow loop that houses a processing technology. The flow is returned to the wellhead and back into the existing flowline infrastructure. Processing hardware is installed between the existing isolation barriers and eliminates the need for expensive, high risk well intervention, field shut down, or flowline decommissioning, while minimizing production losses. The technologies and the range of possible solutions enabled by MARS are evolving. The existing or emerging processing technologies that can be fitted on to any wellhead with minimal risk include:• multiphase pumping • multiphase metering • fluid sampling • chemical injection and well stimulation • sand management • separation • bulk water management and re-injection • raw seawater injection • pressure...