The Petroleum Safety Authority (PSA) has carried out an audit of how Statoil is meeting regulatory requirements relating to the use of a new method for drilling and well intervention at Gullfaks C, in the North Sea.
The PSA in December 2015 carried out an audit of Statoil’s planning and execution of the TTRD (Through Tubing Rotary Drilling) method for intervention, drilling and completion of wells at Gullfaks C. The audit was conducted at Statoil’s premises at Sandsli.
TTRD involves drilling a sidetrack well from an existing, conventional well. According to Statoil, the greatest benefit of this method is that new reservoirs can be reached without the need to remove existing Christmas trees, production tubing or casings.
Statoil also claimed that TTRD wells are particularly useful for reaching isolated pockets of oil and gas on mature fields in a cost-efficient manner.
In its report, the PSA said that these types of well operations differ in many respects from conventional methods and may therefore entail a different risk scenario.
The objective of the audit was to monitor how Statoil, along with its drilling contractor KCA Deutag and other stakeholders, is safeguarding the planning, experience transfer and execution of TTRD operations with regard to the regulations and its own requirements, the PSA said.
While no non-conformities were detected during this audit, one improvement point was identified relating to plans for follow-up and improvement following an earlier incident.
Statoil has been asked to report on their assessment of the improvement points by May 2, 2016.
Back in April 2012, Statoil awarded a contract to Aker Solutions for hiring of an entirely new type of rig in an effort to increase recovery from existing fields. The new rig type, Category B rig, was supposed to fill the gap between light intervention vessels (category A) and conventional rigs (category C), and carry out sidetrack drilling from production tubing (through tubing drilling – TTD) in a manner that allows simultaneous production from both the new sidetrack and existing production tubing.
The rig was supposed to be in service some time during 2015. However, in June 2013, Statoil and Aker Solutions agreed to cancel the contract for the Category B rig hire due to remaining further technology qualification. Afterwards, Statoil decided to consider alternative solution.