Subsea vessel helps Petrobras reduce costsProjects and Operations // January 26, 2015
Petrobras, Brazil's state oil company, says technology adapted for pre-salt depths replacing the use of drilling rigs, is saving US$5 million per well.
At the end of last year, Petrobras deployed its first wet Christmas tree 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 drilling unit.
This resulted in a time saving of approximately 10 days, generating a gain of more than US$5 million.
The well on which the Christmas tree was installed using this technique, 7-SPH-2D-SP, is in Sapinhoá field, in the pre-salt layer of Santos Basin, at a depth of 2,130m.
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 drilling ships, which are much more expensive to charter.
"SESVs have some other major advantages in relation to traditional drilling ships," said Petrobras. "For example, using a drilling ship it takes around 10 hours to lower a riser 1,000m in the open sea. Consequently, the time taken to lower a Christmas tree for installation on a well at a water depth of 2,300m is 40 hours on average. SESVs, on the other hand, can perform the same operation in less than four hours, due to the cable launch and return speed."