At the end of last year, Petrobras deployed its first wet Christmas tree using cables in the pre-salt area. The main change involved was the use of a subsea equipment support vessel (SESV) to install the equipment rather than a traditional drillship. This resulted in a time saving of approximately 10 days, generating a gain of more than $5 million. The Christmas tree was installed using this technique on Well 7-SPH-2D-SP, which is located on the Sapinhoá field in the pre-salt layer of Santos Basin, at a depth of 2,130 m.
The operation, which involved lowering the Christmas tree into position and installing it on the wellhead using a suspended cable, was carried out from an SESV using a subsea equipment guidance system. This installation technique replaces the use of drillships. Petrobras estimates that it takes approximately 10 hours to lower a riser 1,000 m in the open sea using a drillship. Consequently, the time taken to lower a Christmas tree for installation on a well at a water depth of 2,300 m is 40 hours on average. SESVs, on the other hand, can perform the same maneuver in less than four hours, due to the cable launch and return speed, according to the operator.
Petrobras had already used this technology at depths of up to 2,000 m. Following engineering studies, some adaptations were made to the SESV Skandi Santos, enabling the vessel to install equipment at depths of up to 2,300 m. Petrobras has now chartered a second SESV, which is being adapted for depths of up to 2,500 m and should start operating in the second half of 2016.
The Sapinhoá field is operated by Petrobras (45%) in partnership with BG E&P Brasil (30%) and Repsol Sinopec Brasil (25%).