Wellhead control panel (WHCP) is system package controller in oil & gas exploration onshore/offshore. Each well always equipped with SSV (surface safety valve), common each a well consist three safety valves (SV): down hole safety valve (DHSV), master safety valve (MSV), and wing safety valve (WSV) where both MSV & WSV usually called surface safety valve (SSV). SSV can be driven by hydraulic actuator or pneumatic actuator depends on the pressure rating, then DHSV can be driven by only hydraulic actuator because needed high pressure to open it ( > 400 bar). Below showing picture design WHCP in another offshore platform
WHCP systems usually consist of hydraulic reservoir, strainer, hydraulic pumps, accumulator, wellhead control module, and hydraulic line which are supply and return to wellhead control module. Any other parts except wellhead control module are classified into basic cabinet. Each control module is built up dedicated for one well only, therefore if there are 6 well in a wellhead platform, then there will be 1 basic cabinet and 6 wellhead control module needed.
Hydraulic reservoir contains hydraulic fluid in sufficient quantity to operate each wellhead and few equipment instruments in field flow-line. The size of reservoir is determine through an estimation of hydraulic fluid needed to operate each actuator, possible leakage, distance from the well, and an additional safety factor. Usually the hydraulic reservoir is an atmospheric tank with a flame arrestor venting and filler access.
Hydraulic pump provided to build up a hydraulic header (medium and high pressure) the WHCP utilize. Common the each service pressure dedicated one or two item pump hydraulic as main & backup pump for high performance system. Accumulator provided to stored energy hydraulic if function pump has stop. Hydraulic fluid accumulated at the hydraulic header (high pressure and medium pressure) then it’s ready to supply each wellhead control module. Usually the line from hydraulic header to wellhead control module is called a hydraulic supply lines. Wellhead control module, the sequence and logic to operate the DHSV and SSV is built-up. ESD main signal also goes to this module, it needs to open the DHSV and SSV, it supplies the high pressure or medium pressure hydraulic fluid to the SCSSV and SSV. In case there is a need to close it down, the hydraulic fluid supply will close and the hydraulic fluid will goes to a hydraulic return line through a three way valves selector. This hydraulic return line will goes to the hydraulic reservoir again.
The last explanation we can conclude that the wellhead control panel (WHCP) is a hydraulic system that utilizes a hydraulic power pack and a wellhead control module to perform its task. Below showing example description overall design schematic.