Typical offshore process platform have following process
Separation is main process in the central processing platforms, in which oil, gas and water is separated from the well fluid. Well fluid from various well platforms / subsea manifold reaches the process complex via subsea pipelines and risers and is further processed in more than one train. Each train will normally consist of a production manifold, well fluid heater, Inlet Separator, crude oil manifold, crude oil heater, Surge Tanks and MOL Pumps. Well fluid is received in the production manifold. Demulsified chemical is dozed in production manifold to promote breaking up of water–oil emulsion
Gas Compression and Gas Dehydration
Produced Water Conditioning
- Flash Vessel: – flash vessel receives water from both Inlet separators and surge tanks. It is maintained at 0.8 kg pressure. In flash vessel most of the dissolved gases in the produced water flashes out which is routed to LP flare header. associated oil from the produced water in the flash vessel is routed to closed drain header and is collected in the sump caisson.
- CPI separators:- Water from the flash vessel flows to many CPI separators in parallel. Oil from CPI separator is collected in a tank from which it is pumped to oil manifold. Gas goes to LP Flare header.
- IGF unit:- Water from CPI separator flows to IGF unit. IGF is a tank in which gas bubbles are aerated with motor driven agitators. These bubbles float the oil droplets to surface .This collected oil is pumped to CPI separators.
- Sump Caisson:-Water from IGF is routed to sump caisson which is a vessel with bottom end open through which water continuously drains into the sea. Oil floating in the surface of the sump caisson is collected in the blow caisson and lifted up and flown into the skimmer with gas injection.
Water injection system and Sea water processing
- Water Injection:- Water Injection is done to maintain reservoir pressure as well as water flooding. To prevent damage to the reservoir the quality of water injected is strictly complied with. Also, the health of the pipelines carrying the injection water to the wells and well platforms is taken care of by dozing chemicals to prevent corrosion and generation of h2s by srb colonies. The major components of water injection systems are sea water lift pumps, coarse filters, fine filters, deoxygenating towers, booster’s pumps, main injection pumps, chemical dosing system, chemical dozing system flocculent, scale inhibitor, corrosion inhibitor, chlorination etc.
- Sea Water Lifting and Filtering:- Water from sea is lifted with seawater lift pumps and fed to Coarse Filters and fine filters for filtering. Coarse filters the particles are filtered to 20 microns. Fine filters the particles are filtered up to 2 microns. Poly electrolyte and coagulants are added in sea water lift pump discharge to promote coagulation of suspended particles.
- De–Oxygynation and Pumping:- The filtered water flows to deoxygenating towers for removal of oxygen. De-oxygenation prevents formation of aerobic bacterial colonies (sulphur reducing bacteria) in the WI flow lines. Vacuum pumps and oxygen scavenger chemical dozed facilitates oxygen removal in the towers. Booster pumps take suction from de-oxygenation towers and feed Main Injection Pumps. Scale inhibitors, bactericide and corrosion inhibitor chemicals are dozed in the discharge of booster pumps. MIP’s discharge the treated water to Water Injection subsea pipelines to wells and well platforms for injecting in to water injection Wells
Sea water processing and injection system:
Water Maker/Utilities/Sewage Treatment
Emergency diesel generators
Fire water pumps
Fire detection & Suppression system
Nitrogen Air receiver
Installations of central processing platform
Fixed platforms are anchored to the seabed with piles or other devices. They are the most common type of offshore platform and can be used for both drilling and production.
- Steel jacket platforms are the most common type of fixed platform. They are made of steel and are anchored to the seabed with piles. Steel jacket platforms are relatively inexpensive and can be easily modified to accommodate different drilling and production requirements.
- Concrete caisson platforms are made of concrete and are also anchored to the seabed with piles. Concrete caisson platforms are more expensive than steel jacket platforms, but they are also more durable. They are
often used in areas where the seabed is soft or unstable.
Floating platforms are not anchored to the seabed and are used in deeper water. They are more expensive than fixed platforms, but they are also more flexible and can be moved to different locations.
- Semi-submersible platforms are the most common type of floating platform. They have a hull that floats on the surface of the water and legs that reach down to the seabed. Semi-submersible platforms are stable in
deep water and can be used in a variety of weather conditions.
- Tension-leg platforms are also a type of floating platform. They have a hull that floats on the surface of the water and legs that are tethered to the seabed with cables. This design provides very good stability and allows tension-leg platforms to be used in very deep water.
- Spar platforms are a type of floating platform that is shaped like a cylinder. They have a hull that floats on the surface of the water and a spar that extends down to the seabed. Spar platforms are used in water depths up to about 3,000 meters.
Drillships are mobile platforms that are used for drilling in deep water. They are typically anchored to the seabed, but they can also be moved to different locations. Drillships are the most expensive type of offshore platform, but they are also the most versatile.
Jackup rigs are mobile platforms that can be moved from one location to another. They are used for drilling in shallow water. Jackup rigs are less expensive than drillships, but they are not as versatile.
Floating production, storage, and offloading (FPSO) units are used to produce, store, and offload oil and gas. They are typically anchored to the seabed. FPSO units are a cost-effective way to produce oil and gas in deep water.
The type of offshore platform that is used depends on a number of factors, including the water depth, the type of drilling operation, and the cost.