Offshore Oil and Gas
The extraction of offshore oil and gas is critical to the world’s energy supply. It will necessitate increasingly sophisticated technology as well as increased environmental consciousness. Offshore production accounts for 30% of global oil output and 27% of global gas production. Despite considerable onshore development of unconventional resources such as oil sands and shale oil and gas, these percentages have been stable since the early 2000s. Offshore production now accounts for 20% of world oil reserves and 30% of global gas reserves
Cost and time constraints
Offshore production, like unconventional resources, is restricted by cost and the environment. Despite technological advances, each stage of oil and gas production, from discovery to drilling to extraction to platform and vessel construction, requires billions of dollars in investment. Each project’s cost-competitiveness must be assessed independently. In response to environmental events like as the Macondo blowout in April 2010, companies are updating existing facilities, adjusting seabed installation designs, and strengthening best practices. Constant vigilance is required, especially while operating in such hazardous environments as the Arctic.
Deep-water output is increasing
Offshore production in 200-meter-deep oceans began in the 1950s. On the seafloor, platforms with metal or concrete legs were constructed. Following the 1973 oil crisis, North Sea output increased dramatically. Half of today’s 17,000 platforms are permanently anchored to the bottom. Firms began pushing deeper in the 1990s, between 400 and 1500 meters (deep-water) (ultra-deep water). Companies are currently producing oil at depths of up to 3,000 meters and want to reach 4,000 meters. To reach such depths, hundreds of meters of silt must be excavated through.
Offshore deep-water production is on the rise. The Libra offshore oil field development, for example, is located more than 200 kilometers south of Rio de Janeiro and seeks deposits 3,500 meters beneath a salt layer, which is 2,000 meters below the seabed. Deep-water production has increased from 3% in 2008 to 6% now
Deep-water production has certain disadvantages
Instead of fixed platforms, deep-water production needs floating platforms connected to wellheads via flexible risers. Some risers transport water and gas to producing wells, while others transport oil to the surface. The risers are insulated to prevent the oil, which is extracted at temperatures exceeding 50°C, from cooling too quickly and clogging the pipes at deep-water conditions. Submarine stations are transforming into a sort of undersea factory, doing duties such as oil and gas separation.
Pipelines can be laid by sophisticated boats and underwater robots to bring the oil onshore. If the oil field is more than 1,000 meters deep and too distant from the shore, the oil is produced, stored, and dumped using a barge or tanker. These FPSOs have a capacity of up to 2.5 million barrels of oil. A field may have many FPSOs, each of which can last 20–25 years. FLNG (floating liquefied natural gas) facilities are also being studied, which would allow for fast liquefaction of gas after production. There is no need for costly onshore gas pipelines and liquefaction plants, which frequently spark debate due to their environmental effects.
First and first, offshore oil and gas must be located. Soundwaves are used by companies such as Geophysical Surveys to examine the seafloor. The energy source in water is a series of compressed air-filled air-chambers of various diameters. The source emits high-pressure energy bursts into the water. The returning sound waves are detected and recorded by hydrophones deployed along cables. Strict mitigation measures are used throughout the procedure to safeguard marine mammals and other marine animals. Geophysical surveys are commonly used for oil and gas exploration, but they are also used to find sand and gravel for coastal restoration.
Drilling in the Ocean
Once a promising resource has been located, firms will use MODUs to drill highly controlled exploration wells (MODUs). Some MODUs is converted into production rigs, which collect oil rather than drilling for it. The oil firm usually replaces the MODU with a permanent oil producing rig. MODUs is classified into four types
- A SUBMARINE OR BARGE MODU is a barge that sits on the seafloor at a depth of 30 to 35 feet (9.1 to 10.7 meters). On the deck of the barge, steel pillars rise above the waterline. A drilling platform is supported by the steel pillars.
- A jackup is a rig that floats on top of a barge. The ship tows the barge to the drill site. Once put up, the jackup’s legs may be extended to the seabed. The legs are weighted so that they do not contact the ground. The jackup will continue to ratchet the legs until the platform is elevated above the water. This shields the rig from the effects of tides and waves. Jackups can work at depths of up to 525 feet (160 meters)
- A drilling rig is located on the top deck of a drill ship. The drill goes all the way through the hull.
- Drill ships use anchors and propellers to control drift while drilling for oil.
- Semisubmersibles float on the ocean’s surface on massive, submerged pontoons. Others necessitate the use of a second vessel to transport them to the drilling location. To hold the structure upright, most use up to a dozen anchors. Some can convert from drilling rigs to production rigs, reducing the need for a second rig if oil is discovered.
MODUs drill into the ocean floor to locate oil and gas resources. The riser is the part of the drill that travels beneath the deck and into the water. The riser is the piece that links the floor to the rig. Engineers insert a drill string, which is a group of pipes, through the riser. The blowout preventer is currently at sea (BOP). By hydraulically sealing the pipe leading up to the rig, an emergency blowout can be avoided. The BOP is one of several interconnected levels of offshore energy safety precautions.
Engineers use metal casings, similar to those used on land-based oil rigs, to support the well. Casings keep the well from collapsing. The walls of each casing are made of cement. Thinner casings are used in deeper wells. Drill bits become smaller as the depth of a hole increases. A liner hanger O-ring is used by engineers to seal each annulus where a thinner casing joins a larger one When the MODU encounters oil, engineers must plug the well. Two plugs will be used to plug the well bore by the engineers. Near the oil deposit. Drilling mud or seawater holds the plug-in place while engineers insert a top plug to cap the hole. A production rig may then take over.
Once a commercially viable well is found, and the limits are met, the focus shifts from exploration to production. Drilling in ultra-deep water at high temperatures and pressures is an offshore oil and gas industry marvel. Every offshore environment appears to have its own manufacturing platform. The permanent platform may be constructed at depths of up to 1500 feet in the sea.
- For drilling and production activities, the Compliant Tower (CT) is a thin, flexible tower supported by a piled foundation. Unlike the fixed platform, the compliant tower can withstand significant lateral loads and is used at sea depths ranging from 1,000 to 2,000 feet.
- The Tension Leg Platform (TLP) is a floating structure that is fastened to the bottom by piles. Ankle tendons provide a broad variety of water depths while allowing for little vertical mobility. Larger TLPs have been successfully deployed at sea depths of 4,000 feet.
- A floating mini-tension leg platform (Mini-TLP) was created to generate smaller deep-water reserves that would be uneconomical to extract using more traditional deep-water production technology. For larger deep-water discoveries, a utility, satellite, or early-production platform. In 1998, the world’s first Mini-TLP was installed.
- The SPAR Platform (SPAR) is a large diameter vertical cylinder with an attached deck.
- The hull is moored by a taut catenary system of six to twenty lines anchored into the bottom. SPARs are now used at water depths of up to 3,000 feet, but current technology allows them to be used in depths of up to 7,500 feet.
- A Floating Production System is a semi-submersible unit containing drilling and production equipment (FPS). It’s held together with wire rope and chain and pushed about by spinning thrusters. Subsea well output is transferred to the surface deck through production risers designed to handle platform motion. The FPS might be rather high.
It might be a single subsea well supplying a neighboring platform, FPS, or TLP, or it could be a network of wells supplying a distant production facility via a manifold and pipeline system. Now used in marine depths of up to 5,000 feet
The FPSO is a large tanker that is permanently attached to the bottom. On an FPSO, oil generated from a neighboring subsea well is offloaded on a regular basis onto a smaller shuttle ship. The oil is subsequently transferred to an onshore processing plant by the shuttle tanker. An FPSO may be appropriate for marginal resources in remote deep-water sites without pipeline infrastructure.
These are the platforms that are visible. Subsea production systems range from a single subsea well on the ocean floor to a network of wells supplying to distant facilities via a manifold and pipeline system. The oil is extracted from the seafloor and connected to an existing platform. A single production platform reliably serves several wells across a vast territory Offshore production platforms are technological wonders, yet oil and gas cannot be produced without human intervention. Larger oil rigs sometimes require more than a hundred employees to keep them running. Because many of these rigs are located far from towns and coastlines, the personnel (engineers, geologists, divers, and physicians) labor on these gigantic installations for weeks at a time
Offshore pipelines are critical in the extraction of oil and gas. Pipelines on the seafloor transport oil and gas from subsea wells to platforms, which are subsequently transported to the shore for processing and distribution.
- There are three types of pipelines: Infield pipes are used to carry fluids.
They are sometimes referred to as feeder lines. These pipelines transport oil, gas, and water from subsea wells to manifolds or directly to processing platforms. A few infield lines connect the platform’s treated water to injection wells. Export pipelines bring refined oil or gas to the shore. A multi-phase pipeline delivers both oil and gas. A pipeline is considered single-phase if it only transmits oil or gas. Transmission pipelines, like ships, transfer oil or gas from one coast to the other
The Outer Ecosystem
Geophysical businesses, drillers, and producers are all part of the offshore oil and gas production ecosystem. Thousands of additional industries, including heavy lift vessel operators, steel fabricators, marine and helicopter transportation companies, ROV makers, shipbuilders, and computer-aided design firms, as well as legal and financial services, rely on America’s offshore energy