BHA Inspection Criteria

I am looking for some advice on tubular inspection criteria as
defined by T H Hill.

Our rig contract states that the drill collars shall be fully
inspected to meet the requirements of T H Hill DS-1 Category 4 (or
equivalent).

Within TH Hill Drill Stem Inspection manual, it refers to the
definition of Category 4 as ”œdrilling conditions more difficult than
Category 3. Significant fishing costs or losing part of the hole are
likely in the event of drill string failure”.

Further within the document it discusses setting acceptance criteria
for drill collars by specifying the acceptable bending strength
ratio range which establishes the dimensional requirements for drill
collar OD and ID and states a range for the size of drill collar.
There is also a reference to recommended inspection programs in
Table 2.3 (Component 3-5) for DC & HWDP.

The rig we are about to contract has 6.1/2” drill collars, which
have 4.1/2” IF connections. These used to be 4” IF but were recut to
4.1/2” IF.

The attached Tuboscope inspection sheet for the 6.1/2" drill collars
on the rig show the ODs and IDs, and the equivalent Bending Strength
Ratio. This shows that the BSR would be lower than the 2.25 - 2.75
(guideline within T H Hill) if the drill collars had 4.1/2” IF
connections.

This rig was working prior to our contract with 4.1/2” IF
connections.

We are being told that the threads on these drill collars would have
to be recut to 4” IF to meet the BSR as defined by the T H Hill
inspection criteria range.

We would like to keep the threads as 4.1/2” IF.

Has anyone had experience of this?
What is the potential impact or risk exposure by keeping 4.1/2" IF
connections with BSR as low as 1.80.

Regards,
Tony Williams

5 Answer(s)

---