Socotherm’s technology has reached a record depth beneath the waters of the Gulf of Mexico.
The Perdido platform showcases a major milestone in oil and gas offshore exploration, and Socotherm’s technological solutions helped to make it possible. The Perdido operation will allow oil production from the deepest (2851 m/9356 ft) and one of the most remote areas of the Gulf of Mexico thus far.
No doubt, the Perdido Development represents a challenging frontier area whose conquest demonstrates the critical value of our energy resources. From a technological point of view, its success required major advances in addressing obstacles such as extreme water pressures, cold temperatures and other fluctuating marine
conditions, such as high winds and waves, currents, tropical storms and hurricanes.
Designed to address all of these conditions, the Perdido facility is a single vertical cylinder of 50 000 t, which is almost as tall as the Eiffel Tower with its topsides and drilling rig - about 168 m, and 36 m in diameter. It supports a huge operations deck that includes a common processing hub incorporating drilling capability and functionality, which allows for the gathering, processing and exporting of production.
Accordingly, the platform was designed to concentrate all possible operations in order to reduce costs and lower the environmental impact. Traditionally, multiple offshore platforms would have been installed to produce fields of this size. Once fully operational, this single platform will be capable of producing up to 130 000 bpd of oil and 200 million ft3/d.
The Perdido platform is located in Alaminos Canyon Block 857, about 200 miles south of Houston, Texas. The ‘truss spar’ platform operated by Shell on behalf of its joint venture partners BP and Chevron will develop the Great White, Tobago and Silvertip fields that will have 35 wells (22 direct vertical access wells from the spar, with an additional 13 tiebacks from subsea completions) within a 30 mile (55 km) radius of the facility. Its structure has been built to support five production pipelines of 14.126 in. diameter and 0.75 in. thickness, known as top tension risers (TTRs). These TTRs reach a 2377 m depth and have thermal insulation systems with a high degree of hydrostatic pressure resistance, superior to 250 bars.
This technology was tailored by Socotherm through virtual and field simulations done in its Research & Development Centre in Argentina in order to support strong dynamic efforts.
Proven in performance
Socotherm conceived the TTRs’ coating system based on two main goals specified by Shell. First, in terms of thermal insulation, the target was to reach a 0.452 Btu/hr.ft2 °F (2.57 W/m2.K) U-Value - based in its internal diameter – that would ensure the flow from the sea bed to the platform in spite of the low temperatures, which reach 4 ºC. The second issue to be considered was reaching a 260 kips pipe’s vertical buoyancy that would contribute to the stability of the platform, whose structure should be able to survive hurricanes. In order
to fulfill these requirements, the chosen solution was the application of a WETISOKOTE® thermal insulation system (five layers syntactic polypropylene) of 102 mm, thickness over the 24 m steel pipes that will form the TTRs. WETISOKOTE® was developed by Socotherm for shallow, deep and ultra-deepwater environments. Its Multy-Pass® application process technology of lateral extrusion provides the chance to combine different kinds of polypropylene compounds in order to comply with the most stringent project requirements regardless of the pipe diameter or its laying systems (jlay, reeling, etc.). Hence, and without this implying a limit, this combination of materials allows reaching maximum operation temperatures between 110 and 140 ºC, beyond 3000 m depth, adding a high degree of hydrostatic pressure resistance and great abrasion resistance.
By using the Multy-Pass® System, it is possible to obtain an homogeneous coating, of high thickness and concentricity whose five layers are applied and work in the following way:
Layer 1: fusion bonded epoxy primer.
The first layer is a fusion bonded epoxy powder that provides the pipe’s steel surface with a film that is highly resistant to chemical attack, ensuring good resistance to cathodic disbondment.
Layer 2: polypropylene copolymer adhesive
The second layer consists of an adhesive copolymer that works as a bonding layer between the polypropylene and the first layer of fusion bonded epoxy powder.
Layer 3: solid polypropylene
The third layer consists of an extruded sheet of polypropylene. Once this layer has been applied, the integrity of the anticorrosion coating is guaranteed.
Layer 4: insulation syntactic PP-based material
The exceptional resistance of polypropylene to high-pressure is obtained using a matrix of solid polypropylene based on a proprietary technology in which Hollow Glass Microspheres are incorporated during extrusion operation. The thickness of this layer basically depends on the level of insulation that has to be reached (always respecting the maximum coating diameter) in order to comply with the flow assurance calculations.
Layer 5: solid polypropylene outer layer (top coat)
The outer layer is a compact modified polypropylene copolymer with suitable thermal aging stabilisation packaging and strong abrasion resistance.
With the aim of optimising costs and logistic efficiency, WETISOKOTE® application was made by Socotherm-
LaBarge, Socotherm’s subsidiary, in its Channelview facility, located near of Houston, Texas. Besides its proximity to the Gulf of Mexico, this facility has direct access to the Houston Ship Channel and the Intercoastal Waterway, with a dock for barge load in/out on the premises of 490 ft long, 12 ft draft).
Innovation in the protection of joints – continuous protection
In addition to the protection and buoyancy requirements of the pipes, it was also necessary to guarantee that the couplings connecting them could keep the same insulation and resistance as the 102 mm thickness of Wetisokote®. The pipe connections required pin and box steel unions that modified the outer diameter of the pipeline. The solution given by Socotherm was the design of syntactic polypropylene half covers, molded as per the pin and box unions’ shape and then secured around them with the help of titanium bands. The design of these half covers included provisions about installation. To that effect, parallel holes were made in the upper section of the half covers, where special accessories were placed in order to hold and apply
them over the unions before the immersion of the pipes.
While the steel pipes were coated in Channelview, the production of the half covers was made at Socotherm’s
facility located in Escobar (Buenos Aires, Argentina) because it required the constant supervision of its R&D
crew. To accomplish this stage of the production, an existent facility was redesigned, and specific measures and tolerance tests were carried out under a tight schedule, including the delivery as per Shell’s installation programme of each riser.
In 1996, when the Perdido Project was announced, none of the described technologies existed and subsea exploration at depths of 3000 m was closer to science fiction. Now, because of all the engineering innovations and technological solutions designed to achieve and complete this massive project, exploration at this depth is now reality. With Socotherm’s designs and provision of steel-pipe protection systems, once seemingly impossible feats can now become commonplace in the worldwide energy industry.
Source: World Pipelines – January 2011