Schlumberger

Performance Report: BREAKDOWN Raises the Bar in UK Water Injection Project

Challenge: The reservoir was drilled with a low-solids FLOPRO NT water-based fluid. The operator required a breaker formulation that would not only allow the upper completion to be run before losing filtration control, but also deliver superb injectivity on completion. A key requirement of the breaker selected was that it had to be effective in the controlled destruction of the filter cake to allow sufficient time to trip out and install the FIV packer.

Solution: After testing a range of different breakers in its labs, the operator selected the M-I SWACO BREAKDOWN as the preferred system for this completion. BREAKDOWN comprises enzyme and chelant components, both of which must react with the filter-cake at approximately the same rate. The breaker design was validated prior to the job, using a filter-cake laid down on an aloxite disk under projected conditions of pressure and temperature. Afterwards, a volume of breaker solution was applied to the cake and allowed to soak under differential pressure, after which the break-through time was measured. The volume applied was calculated from a “scale-down” spreadsheet to ensure the ratio of breaker volume to the surface area of the filter-cake replicates the field geometry. An injection test was carried out after the soak period and residual filter-cake is tested for starch to ensure the entire available polymer has been removed.

Result: The breaker acted on the filter-cake in the required and planned time, thus allowing the completion and the FIV packer to be run without losses to the formation with the filter-cake remaining functional throughout. This operation took several days to complete after the breaker had been spotted across the sand screens. Upon completion, injectivity tests with seawater were successful with approximately 15,000 bbl/d achieved, despite poorer than expected reservoir quality.
Furthermore, since the breaker was mixed onshore and shipped to location, on-site waste volume was minimized and there were no HSE incidents related to handling and mixing on the rig.

Well Information
Location UK Foinaven West of Shetland
Well Type Water Injector
Date April 2009
Maximum Deviation 47˚
BHST 63˚C (145˚F)
Well Depth 3,115m MD (10,220 ft)
Well Geometry 7 in tubing / 5 ½ in screens to TD

The breaker acted on the filter-cake in the required and planned time, thus allowing the completion and the FIV packer to be run without losses to the formation with the filter-cake remaining functional throughout. This operation took several days to complete after the breaker had been spotted across the sand screens. Upon completion, injectivity tests with seawater were successful with approximately 15,000 bbl/d achieved, despite poorer than expected reservoir quality.

Furthermore, since the breaker was mixed onshore and shipped to location, on-site waste volume was minimized and there were no HSE incidents related to handling and mixing on the rig.


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