Subsea wellhead

The most basic subsea satellite is a single Subsea Wellhead with Subsea Tree, connected to a production facility by a series of pipelines and umbilicals. A control module, usually situated on the subsea tree, allows the production platform to remotely operate the subsea facility (i.e. valves, chokes). 

Whether on land or offshore, the principle of satellite development is the same. A new field is accessed with wells, and an export link is installed to the existing (host) facility. Development is not always easier on land, as environmental restrictions mean that some onshore fields have to be developed using directional drilling techniques (originally associated with offshore developments). A vertical well can be drilled offshore away from the host facility, and the well completed using a subsea wellhead. 

South China Sea, Champion 41, Blowout, Fire Failure of subsea wellhead, jacket severely damaged... 

Addition of up to 200 ppm concentration of wax modifier did not affect the dehydration performance of the treated emulsion even when the two treating chemicals were premixed and pumped through a pipe loop to simulate transport in a single subsea Injection line to the subsea wellhead. 

On the day of the accident, April 20, 2010, the intention was to seal temporarily the Macondo well so that Deepwater Horizon could move away - temporary abandonment . The plan was that, at some later point, another completion rig would be put into place to install hydrocarbon production equipment. This rig would in turn be replaced by a production facility that would connect to the subsea wellhead, left by the completion rig, so that production could be started. 

The most fundamental difference found between onshore and offshore drilling occurs when the wellhead is located at the seafloor. This configuration makes communication with the well more complex. A marine riser provides communication and circulation capability between the surface and the seafloor, and is used at some point during most offshore drilling. The riser consists of large-diameter (17-20) in.) steel pipe joints of approximately 50-ft lengths, with quick-connect couplings. The riser can be connected at the seafloor to a wellhead or to a subsea blowout preventer stack. A diverter system is usually attached at the... 

The crude separation facilities for a possible Troll oil development are shown In Fiq. 6. The crude stream from subsea wells with an expected platform arrival temperature of circa 5°C will be warmed by heat exchange with the export crude free water is knocked out In a 1st stage separator and the crude 1s then heated to the desired process temperature (> 40°C), prior to entering the second stage separator. Provision for the injection of demulsifier is required at the wellhead and upstream of the crude heater. 

Flow In an uninsulated subsea flowline Is cooled from 55°C to a seabed temperature of 5°C (Fig. 4), some 1200 m from the wellhead. Beyond this point wax deposit will be minimal since there is no temperature differential. Within 60 meters of the wellhead, the stream temperature is 1n excess of 35°C and no accumulation of wax will occur any wax deposited during a shutdown would be redissolved when flowing. 

It is clear that during start-up, conditions conducive to hydrate formation can exist at the wellhead, flowline and in the riser. Once flow has stabilised, conditions suitable for hydrate formation can exist in the subsea flowline, particularly at higher GOR s. 

Scenario Overpressure wellhead piping, subsea production flow hue and topsides. 

U.S. Navy Diving Manual[200S], Revision 6 IMCA 0 014, IMCA International Code of Practice for Offshore Diving IMCAD 019, Diving Operations in Support of Intervention on Wellheads and Subsea Facilities... 

The subsea part of the system will be connected with the damaged well and wiU have the capabiUty of totally capturing the leak, even if the wellhead is damaged. An initial subsea response system was put into service in February 2011. 

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