Installing and testing a new deep wellbore barrier in older assets has proven to be challenging, especially when previously installed devices are difficult to remove from the well. When a new barrier is installed in close proximity to the old device it makes it extremely hard to assure integrity of the upper barrier due to the small volume that exists between the two. Only by measuring the pressure between the devices can the integrity of the newer barrier be correctly verified.
Isolating a reservoir by installing a deep barrier, complete with Barrier Verification System (BVS) logging the pressure across the barrier, will give much quicker assurance that the barrier has in fact isolated the reservoir. The BVS consists of a pressure sensor with a wireless transmitter attached below the barrier. The receiver is included in the setting tool above the barrier to be tested and wirelessly records the pressure from below the installed barrier. An additional pressure sensor in the receiver forms part of the tool to provide an accurate pressure over the established barrier. The receiver can transfer real time data on e-line to surface, or be deployed in memory mode for slickline or other intervention methods.
As part of the barrier verification the setting log from the Electronic Setting Tool (EST) is recorded. This data is part of the integrity verification package to the customer. Data can be verified against our extensive database of previous logs taken from products across our range. In wells where tubing 19been set within its setting range.
A major North Sea Operator made significant operational savings by being able to conduct their deep-set barrier verification using this technology across 11 wells with an average integrity test time of 50 minutes. Traditional chart recorder document methods require stable pressure at surface to confirm the barrier's integrity. The time required to achieve stable recordable condition on surface is normally significantly longer, due to free gas and introduction of colder test fluid in the well column.
The paper will look at the operational use and savings obtained with the technology, the savings and enhanced reliability with documented installation profiles in execution of a multi-well suspension operations in the North Sea, and the behavior and stability of the well before and after the intervention operations.
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