OFFSHORE OIL & GAS PRODUCTION meeting challenges every day
More than two thirds of the earth’s surface is covered in water. It therefore stands to reason that oil and gas are produced not just on land, but at sea, too. However, so-called “offshore production” is much more technically demanding than production on land, because usually platforms are needed to reach the reservoirs under the seabed and carry out drilling and production activities. Drilling rigs and production platforms are some of the most extreme workplaces in the world. The staff that work there can only reach their workplace by helicopter or supply ship and stay on the platform for several weeks at a time.
24 hours a day the workers ensure production runs smoothly. But the people that work on the platforms, and the materials, must be able to bear the worst possible weather conditions and meter-high waves.
From drilling to production Installing the facilities
Before production can start, a well has to be drilled to reach the reservoir – just like on land. Special mobile drilling platforms are used to do this. After the drilling platform is removed a production platform is installed over the borehole. The oil and gas are transported from the borehole to the platform via pipelines. There, they are treated before being transported either directly to land via pipeline or loaded onto ships. Which type of platform is used depends on the depth of the water – platforms in shallow waters are very different to platforms used in deep waters. Our diagram explains the differences between the platforms and the situations in which they are used.
This is a mobile platform whose moveable legs can be raised or lowered like a mechanical jack. They are designed for short-term deployments and for transportation from one location to the next, and are therefore mainly used for exploratory drilling operations. Water depth: Usually 100 to 120 metres, but some also extend to 170 metres.
These are small, unmanned auxiliary platforms that are merely used to receive oil or gas from production wells. They are automatically controlled and are connected with larger platforms via flowlines that are used to transfer the oil or gas to them. Water depth: 100 to 3000 metres, depending on the type of platform.
This is a fixed structure used for production operations, which is anchored to the seabed on a solid base of concrete or steel. Because they are not transportable, they are intended for long-term deployment. Water depth: Up to 520 metres.
Compliant Tower (CT)
This platform consists of a slim, mobile tower, which is anchored to the seabed and on which a standard deck for drilling and production is secured. The CT was developed to withstand strong currents. Water depth: 400 to 900 metres.
Tension Leg Platform (TLP)
This floating platform, which is used for production operations, is anchored with steel cables to the seabed so that it is positioned over the wellhead. Standard TLPs rest on four columns and thus resemble semi-submersible platforms. Each of these columns is connected to the seabed. Water depth: From 300 metres to a maximum of 2000 metres.
A subsea completion consists of production wellheads on the seabed that are connected via flowlines with platforms or ships. This is a cost-effective alternative that is particularly sensible with smaller oil and gas fields. Water depth: Up to approx. 2000 metres.
This platform also floats on the water and, like TLPs, is moored with cables to the seabed. Spar platforms, however, have a large, cylinder-like base, which lies under water and is used as a storage or ballast tank. It stabilises the platform and keeps it upright. Water depth: Normally around 1800 metres, but some even extend to 2500 metres.
This is a floating, transportable platform that rests on pontoons and is held with anchor chains and/or cables to the seabed. They are used for both drilling and production operations. Water depth: Up to 3,000 metres.
FPSO (Floating Production, Storage & Offloading Vessel)
FPSOs are floating production systems, mostly in the form of ships. They receive the oil or gas from production wells on the seabed or platforms, and process and store it until it can be offloaded onto tankers. FPSOs are preferred in remote areas, as they are easy to install and do not require a local infrastructure such as pipelines to transfer the oil. Water depth: Up to 3,000 metres.
Europe’s most important supply region The North Sea
The North Sea is currently irreplaceable for Europe as a supplier of oil and gas – more than half the natural gas and a quarter of the oil consumed today in the European Union comes from the North Sea. The North Sea is also a traditional core region for Wintershall, a major European crude oil and natural gas producer: we have been active in the region since 1965 and operate more than 20 platforms. Most of Wintershall’s production platforms are at a depth of 25 to 40 meters under the sea. However, in Norway the company is conducting Wintershall-operated exploration wells that start at a depth of up to 400 meters.
Oil & gas from Norway
Besides Russia, Norway is Europe’s most important supplier of oil and gas. Wintershall has significantly expanded its activities in Norway in recent years and with about 50 licenses is one of the largest license-holders on the Norwegian Continental Shelf. It has shares in the fields Brage, Gjøa and Vega, among others, and is the operator of two producing fields, Brage and Vega.
The first platform in the Norwegian North Sea which Wintershall took over as operator is the Brage platform, located about 125 kilometers from the Norwegian coast. The water there is 140 meters deep, and oil was produced for the first time in 1993. 20 years later Wintershall took over the operatorship from the Norwegian company Equinor Energy AS.
Today more than 100 staff work on the platform in shifts, each lasting 14 days. The following film provides insight into life in this harsh environment.
Remote-controlled production in the Netherlands
Wintershall is one of the major natural gas producers in the Netherlands and operates 20 offshore platforms here, most of which are controlled from the mainland via a cutting-edge radio-control system: the Center for Remote Controlled Operations (RCO) in Den Helder controls platforms in the British and German sectors of the North Sea as well as the Dutch platforms. This way Wintershall reduces the number of transport and supply flights to the platforms by up to a third. These small remote-controlled platforms are one of the key requirements for commercial production from smaller reservoirs in the southern North Sea. One of Wintershall‘s remote-controlled platforms is the innovative L6-B platform – it sets new standards in unmanned mini-platforms.
6 million cubic meters daily
Wintershall’s largest production platform in the Dutch North Sea is the platform F16-A. It has seven floors and weighs 3,600 tons.
There is an eight-person crew on board which is largely self-sufficient: the crew members generate drinking water via a seawater desalination plant; and a mini power plant generates electricity from some of the natural gas produced. The reservoir the platform produces from lies at a depth of about 3,500 meters. Overall, F16-A can process up to six million cubic meters of natural gas daily.
As an offshore installation manager, I am in charge of everything that happens on the platform and responsible for everybody on it. My team guarantees that the production is running smoothly around the clock, two weeks at a time.Sandor Bont
Highest safety standards Individual concept for each platform
Oil and gas exploration and production on the high seas require particularly extensive safety measures, as the facilities are often located hundreds of kilometers from the mainland and subject to the most extreme weather conditions. To ensure the protection of the environment as well as the safety of its staff, Wintershall’s own company standards go far beyond what is legally required. A tailor-made HSE concept, in which all the possible risks and dangers are reviewed by auditors, is drawn up for every offshore plant. The employees on offshore plants practice what to do if there is an incident, how to handle hazardous substances, and how to survive in ice-cold water.
The safety of the production platforms is guaranteed by an eight-level barrier system, the integrity of which is protected even if some barriers fail.
Geir Ove Kollsgård
Emergency Preparedness & Security Advisor
Eight barriers for more safety
The plants and equipment used by Wintershall for the exploration and production of oil and gas conform to the highest safety standards. Cutting-edge technology is one of the foundations of safety.
For this reason we are continuously investing in new plants and developing our existing ones on an ongoing basis.We consider aspects such as health, safety and environmental protection in the early planning stages of our facilities. For its offshore production, Wintershall uses a system with eight safety barriers. Each barrier is also made of an assembly of safety devices. That means even in the unlikely event that several barriers in the safety system failed at the same time, the integrity of the plant would be guaranteed at all times.
Our diagram explains the barriers that ensure the safety of the platforms.
The design of the facility ensures structural safety both under water and above the surface. The subsea facilities are inspected by divers or remote controlled vehicles.
The subsurface safety valve is installed around 100 meters beneath the seabed, and prevents oil or gas from being released accidentally. Further valves provide additional protection.
Sources of ignition: If oil or gas should leak out, fire or explosions cannot occur. All electrical equipment and devices are earthed and designed in such a way that they do not produce sparks.
Warning and fire alarm systems: Sensors which react to gas and naked flames and trigger alarms are installed on every deck. Crew members can also trigger the alarms manually.
Fire protection systems such as sprinkler systems and fire extinguishers, can be found on the decks. In an emergency, water pumps on the bottom deck can provide seawater for fighting fires.
Shut-off devices ensure the facility is depressurized and seal off areas where hazardous substances have leaked out. A shut-off valve can seal off the platform from the export pipeline.
A range of facilities are pro-vided for emergencies. These include safe evacuation rooms, helicopter landing pads, emergency power units, and failsafe communication systems.
Rescue equipment: If there is ever a need for the crew to leave the platform in order to reach safety, motor rescue boats and enclosed rescue capsules are available. Emergency evacuations are practiced on a regular basis.
Turning old into new
In rough seas it is not just the people that have to give maximum performance; the materials have to do the same. The life of a platform in these conditions is about 25 years. After that the plants are normally dismantled and scrapped.
But Wintershall has managed to reconcile economic and ecological interests in a very practical way: it converted two of its platforms in the Dutch North Sea and completely modernized them. This saved costs, time and materials compared to building a new platform from scratch because many of the facilities were recycled.