Running washpipe is impractical in extended-reach, highly deviatedwells

An operator needed to drill several wells in an oil field offshore Norway. This field is characterized by variations in permeability, with several shale zones interbedded between formation sand.

The operator planned to drill a long, horizontal well with a measured depth of 14,682 ft [4,475 m] and a total vertical depth of 6,476 ft [1,974 m]. The well would have a 90° deviation and an openhole span of 4,921 ft [1,500 m]. Because of the field’s geology, wells in this field had previously been completed with stand-alone screens and ResFlow inflow control devices (ICDs) that use nozzles to regulate flow along the length of the reservoir. These ICDs are typically run with washpipe (the inner string) to permit washdown operations while the screens are being run inhole. Washpipe also permits the placement of filtercake breaker along the entire openhole section after the screen reaches total depth (TD).

However, washpipe rental and rig time to run it in and pull it out increase costs, and the process complicates logistics and creates safety risks. Moreover, in wells as long as the one planned, the heavy washpipe tests the tensile limits of the service tool and makes it difficult to run the screens to TD.

ResFlow CV ICD assembly eliminates need for washpipe

To reduce the costs and risks, Schlumberger recommended the use of the new ResFlow CV check-valve ICD, which does not require washpipe. The check-valve assembly includes an aluminum or ceramic ball, a ceramic nozzle, and an aluminum plate. It replaces the standard ResFlow ICD nozzle assembly in the ICD housing.

When this ICD is run inhole, the pressure of the fluid being pumped down the completion string causes the ball to seal the check-valve assembly. Fluid is thus prevented from leaking into the annulus through the nozzle and must travel the length of the completion string to the toe before returning up the annulus.

In this particular case, the aluminum ball and plate were dissolved before production with the standard acid-base breaker system used for well cleanup. At that point, the ResFlow CV check-valve ICD worked like the standard ResFlow ICD nozzle, helping balance inflow across the completion.

Operator trims 24 hours and saves USD 800,000

The well was successfully completed with zero NPT related to Schlumberger services or products. Because of the lighter weight of the assembly string, the completion was run without difficulty to TD. Eliminating the washpipe rental expenses and rig- and service-related costs saved the operator 24 hours and approximately USD 800,000.