AST

Surface test

AST Tool (RIG) Checks

A surface check should be performed if re-running the AST is considered. The AST should be replaced in any case if the next run will take the tool past rotary 200 hours. The AST should also be replaced for reasons mentioned under Lay-out Procedure (below) or if other dynamic BHA components are replaced for the same reasons. An example of a dynamic component is the RSS (Rotary Steerable System).

Surface Acceptance Check Procedure

  1. Seals and surfaces:
    1. Wipe the polished section of the mandrel dry and watch for oil / mud leakage.
    2. Check that there is no mechanical damage on the polished section that will damage the seals. Junk damage, transport damage, etc.
    3. If there is oil or mud leakage or damage, the tool must be laid out.

Downhole Wear

It is possible to check the mechanical integrity of the AST (and other tools in the upper BHA) in abnormal situations, such as when working a stuck BHA or having no drilling progress. This is done by comparing downhole RPM from the MWD / RSS tool with surface RPM. If the average downhole RPM is the same as the surface reading, the AST and all other components between the two measuring points have their mechanical integrity intact.

Lay-out Procedure

The maximum rotating hours (as per IADC report) on an AST tool are 200. In practical terms, the tool should be laid out prior to a run that will result in accumulated rotating hours beyond 200. In cases where a tool has been subjected to abnormal conditions, e.g. excessive jarring, drilling for a considerable time with a ringed-out or undergauged bit or damaged under-reamer, or high sand or solids content in the mud, then the AST may have suffered accelerated wear and should be laid out sooner.