That performance was made possible by the substantial development infrastructure employed at the site, of which some components were well ahead of their time. For example, two dynamically positioned drillships, the Pride Africa and the Pride Angola, were built for the project. New horizontal well technology was adopted to enhance productivity at Girassol and reduce the number of wells to be drilled, and new tools were developed to construct the subsea pipelines. Risers with thermal insulation also made their first appearance at Girassol, carrying production output from the seafloor to the FPSO. It was for these and other major innovations at Girassol that Total won its first OTC award in 2003.
Girassol
Covering an area of 14 by 10 kilometers, Girassol was the first of the Block 17 fields to come on stream, on December 4, 2001. It was also the first deepwater project conducted in Angola.
Girassol’s Development Infrastructure
The development plan for Girassol included:
39 subsea wells, including 23 producing wells.
45 kilometers of flow lines.
29 kilometers of injection lines.
70 kilometers of umbilicals.
The flow lines – eight bundles ranging from 800 to 2,900 meters in length – were built and assembled at the Soyo site in northern Angola and then towed along the seabed to the Girassol field 200 kilometers away, where they were positioned and connected to the production equipment. These operations, conducted with surgical precision in water depths of 1,400 meters and pressure exceeding 150 bars, were a true demonstration of engineering prowess, made possible by the use of acoustic beacons and remote-controlled robots.
In addition, to keep the oil at a temperature of 40°C and prevent it from freezing in the pipelines on the seabed, where the temperature was just 4°C, the flow lines were wrapped in synthetic foam insulation. Indeed, ensuring a continuous flow of output was a major challenge. Engineers therefore adopted a system of production loops designed to prevent the formation of paraffin and hydrates, thanks to the thermal insulation on the flow lines coupled with the use of smart pigs.
Umbilical: An assembly of steel tubes and/or hydraulic lines, electrical cable and fiber-optic cable. Umbilicals are used to control subsea infrastructure
Girassol’s Risers
The genius of these structures is that they offer the desired heat insulation as well as buoyancy for the entire system. After being towed to the Girassol field from the construction site at Lobito, the risers were mounted in place in a matter of hours, thanks to their position sensors. Once they were vertical and connected to a suction anchor, the buoyancy provided by the ballast float and synthetic foam kept the risers in position.
The riser developed for use at Girassol was among the innovations that helped Total E&P Angola win an OTC award in 2003. Building on that knowledge, the affiliate continued to push technological boundaries with new, flexible production risers for Dalia. Extending 1,650 meters in length and weighing nearly 800 tons, the new risers boasted a record outer diameter of almost 60 centimeters and no fewer than eleven layers, designed to ensure fluid flow and provide insulation and mechanical strength. The most striking innovation was a gas lift system consisting of 24 lines feeding six injection points at the riser’s base, offering total daily injection capacity of 800,000 cubic meters of gas.
The Girassol FPSO
The Girassol field offered an initial test of the value of a large-scale FPSO, able to treat more than 200,000 barrels a day – the field’s entire production. In particular, the affiliate hoped to demonstrate the FPSO’s reliability and economic feasibility in water 1,400 meters deep, when connected to subsea wellheads and a gathering system designed to operate for at least 20 years. The FPSO was equipped to separate and treat the various effluents – gas, water, oil – to ensure they met commercial or environmental specifications in order to be marketed, reinjected into the reservoir or discharged.
“Girassol was the Group’s first FPSO and would combine a multitude of innovative technologies in a record time that has yet to be beat.” Pierre Bang, Girassol FPSO Project Manager, 1997-2001.
Girassol also instituted an HSE policy to address the vital concerns of health, safety and the environment. Audits were conducted at the construction sites in both Angola (Lobito and Soyo) and South Korea, where the Girassol FPSO was built. Safety managers were also appointed within each project team on a site-by-site basis to ensure that first-tier suppliers and their subcontractors complied with Total’s safety standards on accident readiness and prevention and training for the relevant personnel. In addition, the FPSO maintained a systematic process for reporting accidents and improving prevention measures throughout the production phase. Expert consultants conducted environmental impact studies at sea and on land at every stage of the project, while contingency plans were developed for responding to an offshore oil spill. Moreover, Total E&P Angola joined forces with ocean research institute IFREMER to conduct a three-year oceanographic campaign to catalog and analyze deepwater marine life, so as to assess the potential impact of oil exploration and production on benthic ecosystems.
In a bid to reduce the environmental impact of its exploration and production, Total introduced a series of measures for Block 17, both on land and at sea. They include reinjecting gas in order to eliminate flaring and make use of energy resources; using drilling mud made with low-toxicity mineral oil; treating the cuttings so as to eliminate residual drilling mud; and recovering heat energy from the turbines for reuse in various processes aboard the FPSOs.