Oil and gas lie hundred to several thousand feet deep under subsurface. The rich pool of hydrocarbons that took millions of years to form is definitely scarce and may act as a pollutant, if not explored in a correct manner. Various technologies are required to reach this pool; the set of technologies are combined at a single place known as a platform. If this precious commodity is drilled onshore, then the setup is termed as a rig, and if done offshore, it is known as a platform. Offshore platforms are more complex in nature, as they need to accommodate not only the entire drilling team but also the produced hydrocarbon.
Based on the depth that needs to be achieved offshore, platforms are classified into different types. Fixed platform (up to 1,500 feet), Compliant Tower (1,500-3,000 feet), Floating Production System (up to 1,500-6,000 feet), Tension Leg Platform (1,500-7,000 feet), and Spar (2,000-10,000 feet) are the different types of platforms. This article examines different technologies or solutions adopted by the industry leaders to save time and money while making offshore platforms lighter and stronger than their existing counterparts.
An oil platform may have more than 50 different components based on the depth where it drills. The typical ones are mud tanks, power source, draw works, drilling assembly, drill floor, rotary table, blow out preventers, pipe handling systems, etc. The weight of the oil platforms may vary between 5,000 tons to 40,000 tons. Broadly, any platform can be divided into two components – the top side and the support hull structure, with more emphasis on the top side.
Topsides: The topside of an oil rig encompasses the surface deck of a platform, which includes all equipment for drilling, production, and processing. The topside operation can include oil and gas treatment, storage and offloading, process support systems, as well as the living quarters for those that work on the rig. All components in a topside construction must be suitable to perform in hostile environments.
A conventional topside design normally requires several modules to be fabricated onshore, transported to the site, and lifted onto the hull supported by a module support frame, and integrated and pre-commissioned offshore. A single lift topside design saves time, reduces safety exposure, and is less expensive to build than the conventional modular approach. The challenge is to find a way to incorporate all of the topside requirements without compromising safety and operability while maintaining the weight below the lifting capacity of available derrick barges in the area.
Making topsides lighter means less equipment, less pipe, less structural steel, reduction in the number of interconnecting for pipe and electrical cables, and reduction in junction boxes, as well as offshore hookup man-hours, compared to conventional design.
The reason for earlier topsides being heavier was due to increased oil prices that allowed any gold plating possible. The spares that were available were beyond optimal limit due to high earnings and high profitability, thus encouraging oil players to have huge inventories lying idle in warehouses. However, two things changed over a period of time, i.e., oil price and exploration site location. Once the industry began shifting to the deepwater arena and designing production facilities for weight-sensitive floaters (TLPs, spars, and semisubmersibles), the value of reducing topside weight took on a new meaning.
There is a misconception that designing topsides to weigh less is a bad idea. Lightweight topsides save time and money, lower hull and mooring costs, maintain precious payload for future expansion, and are safer to build and operate. Lightweight topsides require a smaller hull or, if designed with a margin for growth, the margin for growth is larger. Topsides weight savings increase return on investment by lowering capital costs and shortening the schedule, which accelerates cash flow. As per experience gained by players such as Alliance Engineering, topsides installed costs are within the range of $35,000-$50,000/ton. It is possible to achieve capital cost savings of $100-150 million by reducing a 20,000 ton topsides weight by 15%.
Designing lightweight topsides begins with defining principles that cannot be compromised. These principles are safety, operability (up-time), maintainability, schedule, and cost. The next important ingredient to achieving a lightweight design is a team. A team requires a lightweight mindset, lightweight design experience on several projects, and continual emphasis on saving weight in every discipline. The result is defined by the selection of the correct concept. This includes the design basis, a simplified/streamlined process design, equipment selection and layout, compact footprint, commonality of maintenance area, compact piping, and specifications developed for lightweight design. A few steps that are currently being followed in the industry are listed below:
Lightweight designing does not work if the hull is designed based on early topsides weight estimates, and the estimates later prove to be wrong. Acquiring accurate early weight estimates and maintaining that weight during design and fabrication is a must.
Key players involved in the offshore platform market are of two types: one who owns or leases the facility, and the other those who actually design these facilities.
Rig owners decide if the structure needs to be lightweight, and EPC companies help them in fulfilling this task. During Pre-FEED, EPCs create a model that takes into account several parameters, such as water depth, production rate, number of people on-board, electrical requirements, and discharge facilities that enable them to create a failure-proof model.
There are several areas that are being explored to reduce the weight of the platform. These are discussed below:
Share your focus area or question to engage with our Analysts through the Business Objectives service.
Submit My Business ObjectiveOur long-standing clients include some of the worlds leading brands and forward-thinking corporations.