Pre-salt Seafloor Construction/Remote Operations Challenges Part 1
As a world leader in construction and remote operations in deep waters, Petrobras has been developing new technologies and testing them with their partners in Brazil’s deepwater pre-salt fields for over a decade. Petrobras has historically opted for an incremental strategy to develop its technological capabilities to explore the Brazil’s offshore oil resources. As deepwater discoveries began to enter the production phase, Petrobras opted for using and FPSOs and wet x-mas trees. These discoveries of supergiant oil fields in the Brazilian pre-salt have offered Petrobras an opportunity for reviewing its technological path and it is becoming clear that the national operator has been increasingly inclined to move as much of the oil production systems to the seafloor as possible, therefore diminishing the amount of equipment on its FPSOs, while at the same time planning on increasing the storage capabilities of future pre-salt FPSOs. This move has given the company and its suppliers of equipment and services, a leading technological role in the oil industry.
Challenges in seafloor construction and remote operations of equipment placed on the seafloor abound. With many pre-salt plays being located at depths of over 2,000 meters of water and 300 km offshore, logistics challenges also come into play. Data obtained through exploratory wells integrated to large seismic survey efforts indicate that the pre-salt reservoir rocks can be found in an area extending approximately 800 km in length by 200 km in width offshore, following the coast from the north of the state of Santa Catarina to the State of Espírito Santo. Up to now only a small percentage of this area has been explored, yet this comparatively small area will need to have its seafloor precisely prepared and built up with a large array of subsea equipment needed for production and transportation.
Weather has some influence on seafloor construction, but wind and sea state only affect the initial launching process of equipment from surface vessels and the beginning of the descent. The trip down the water column may sometimes be a major inconvenience to operations due to strong currents pushing on the equipment. In certain locations, such as in some deepwater plays along the Brazilian equatorial margin and even occasionally at the Santos Basin, equipment may need to launched miles from the seafloor location where it needs to go, due to strong currents along the water column and/or deepwater currents. Surface and underwater currents are monitored by a variety of Metoc sensors in support of seafloor construction operations. GIS (Geographical Information System) technology is now regularly used for data management and data exchange of geo-science seabed survey information. The operational implementations of GIS in support of SURF (Subsea infrastructures,Umbilicals, Risers, and Flowlines) field development projects are key in allowing precise placement of subsea equipment and pipelines.