Wet-Buckle” Contingency and Precommissioning Services for 32 Inch 322 Mile (518Km) Pipeline in 3,600 Feet (1,100M) Water

Case Study: Greenstream pipeline project, “wet-buckle” contingency and precommissioning services for 32 inch 322 mile (518km) pipeline in 3,600 feet (1,100m) water

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Introduction, Project Details and Challenges/Solutions:

Introduction: Project Details:

During recent years, technology has The Trans-Mediterranean pipeline, known allowed the exploitation of oil and gas as the Libya Gas Transmission System reserves in increasingly deeper waters. In (LGTS), or Greenstream, is 322 miles addition to floating production facilities and (518km) long, 32 inch diameter. The tanker transportation, pipeline construction pipeline runs from Melitah, Libya, North companies have also developed their Africa to Gela, Sicily, Italy (Fig. 1) and is services to facilitate pipeline transportation located in water depths exceeding 3,600 of oil and gas reserves from deepwater feet (1,100m). The new onshore site was installations. As a result, some construction at the landfall in Gela. companies have been required to obtain a real time solution for a “wet-buckle” Challenges/Solutions: scenario. In an ideal world, construction of offshore pipelines should be completed Weatherford very efficiently mobilised its without any incidents. However, in the real temporary air compressor station world, and for a variety of reasons, (TACSSM) from the Bluestream project sections of a pipeline can sometimes located in Russia to Italy. This project become damaged or even flooded during alone was a major undertaking as the full the laying process. Such an occurrence of station travels as 150 standard sea unplanned flooding of the pipeline is known containers. Several of the pieces of as “wet-buckling”. Since a pipeline is most equipment required special permits to likely to buckle during deepwater travel by road once inside Sicily. To installation, it is important to have detection facilitate the expedient arrival and and correction methods in place at this assembly of all the equipment a holding stage. While few deepwater projects yard and maintenance yard were ultimately require a “wet-buckle” established in advance of the main site contingency during pipe lay, construction being made available. This maintenance companies agree on the benefits of “Buffer Zone” allowed the equipment to be providing it as an insurance. If any buckling stored, sorted and maintained prior to escapes detection during the installation, making the final short journey to the main and is only discovered post installation, site where the sequence, laydown and then the costs to correct the situation can position of each piece of equipment was be huge. as precisely engineered as any other part of the project.

Figure 1: Greenstream route Figure 2: Main compressor unit

Challenges/Solutions:

Weatherford engineers identified a potential The TACS comprises 78 major components, problem in anticipation of high ambient plus 18 coalescing and carbon bed oil summer temperatures in the central removal filters, flow meters, a centralised Mediterranean Sea area. These high ambient remote monitoring system, fuel pumping and temperatures coupled with the prevailing distribution systems, and all support facilities winds potentially could cause a build up of (such as electrical generation, lighting, etc.). heat within the confines of the banks of TACS was estimated to require compression. The solution was to re-engineer approximately 40% less space than the layout of the site and configuration of the conventional compressor units, and consisted manifolds. As a result of this foresight the of 58 main combination compressors (Fig. 2), TACSSM was available 24/7 and during peak four feed compressors, eight high volume air operational loads no unwanted heat build up dryers (Fig. 3) capable of dew points in occurred. Such was the success of the excess of -76°F (-60°C), and eight boosters preparation and mobilisation of the TACS that (Fig. 4). Each Weatherford engineered from availability of the main site to mechanical combination compressor unit consists of a completion took only 16 days. TACS was rotary-screw compressor and horizontal ready to provide emergency “wet-buckle” reciprocating compressor, each one of which contingency services from August 2003 is capable of delivering 1,150scfm/min throughout the pipelay operations, (33m3/min) at 2,000psig (138barg); the entire precommissioning took place early in 2004 station generated a total of 52,500bhp whereby the entire station was required to (39,400kW). The high pressure boosters were dewater and dry the pipeline. Dewatering designed around a two stage horizontal operations were very efficient and very little reciprocating compressor and provided an residual water was left in the pipeline. The additional stage of compression to meet the dewatering efficiency coupled with the high 3,625psig (250barg) final discharge pressure. pressure nature of the air used in dewatering This overall design proved to be the answer resulted in the drying operations being for Saipem’s requirement of maximised fuel concluded ahead of schedule. efficiency and minimised footprint.

Figure 3: Dryers Figure 4: High pressure booster

Results/Benefits and Summary:

Results/Benefits: Summary:

Weatherford was able to provide Saipem The TACS is a unique, mobile facility with a dependable and durable providing high specification air services for compression station for contingency and pipe lay construction companies operating precommissioning for this pipeline project. in deep water, where the cost of not Problems were faced and challenges retaining an immediate remedial solution overcome, and the successful completion for “wet-buckles” during pipe lay could be of the work scope was proof to both huge. It is a proven synergised package Saipem and Weatherford that the TACSSM that can provide dewatering capability of and its completely self supporting inventory up to 64,000scf/min (1,800m3/min) and was an effective solution for this type of 3,625psig (250barg) without the deepwater pipeline project. The installation uncertainty of having to mobilise a large of the TACS from availability of the site to fleet of equipment at the last minute. As mechanical readiness took only 16 days. offshore pipeline developments venture Although few deepwater projects ultimately into deeper and deeper waters, the TACS require a “wet-buckle” contingency during and its capabilities and applications will pipe lay, the benefits of having one in place continue to evolve, meeting new technical become obvious compared to the costs challenges and requirements. incurred to correct the situation post installation.

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