Technique promises greater accuracy in drillstring pressure tests

Offshore staff

ABERDEEN, UK – Churchill Drilling Tools has deployed successfully its mechanical extrusion (MX) and smart dart (SD) systems in drillstring pressure testing.

The MX enables application of rigid SDs for multi-cycle control. Churchill claims the combination provides robustness and resilience to high-pressure/high-temperature environments, and improved reliability and performance compared with conventional ball activation.

The company’s PTS MX system can be used to test a drillstring up to a specific pre-set pressure with the capability to regain circulation between each test. This allows multiple tests to be performed at various pressures in a single run.

PTS MX can be run in any length of pipe, Churchill adds, at any angle or temperature, and with any type of circulation fluid.

The subs’ fully tapered internals provide unrestricted circulation and feature a full thru-bore prior to the first cycle. The SD is dropped and pumped into place with the load transmitted through pins in the dart into the PTS MX sub; the pins determine shear out pressure.

Pressure can be maintained at the required test level as long as necessary. When testing is complete, a small increase in pressure is applied to shear out the dart into the catcher below.

Multiple test cycles can be performed, with full circulation restored between each test, and the shear out point can be accurately modified by altering the dart’s pins before it is dropped.

The system was first used by a pipe manufacturer offshore Norway last year with shearing accuracy results of 99.6%. This has led to a series of new drillstring development applications. The technology also is being used offshore the UK for leak detection in operational drillstrings, in pre-emptive integrity tests prior to ultra-critical high-pressure phases.


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