TECH TIDBITS, vol. 7

Land Rig Surveys Result in High Numbers of Findings with Potentially Serious Consequences

A number of operators have used WEST to gauge the readiness of land rigs for their drilling programs. While it is relatively unusual to identify items that WEST classifies as "Category I" in priority, these surveys have resulted in a significant number.

WEST definitions of recommendation classifications are partially listed as follows. Category I (most serious) and Category II are listed for comparison:

• Category I - Failure to implement this recommendation may lead to loss of wellbore integrity, compromise installation/vessel integrity, or contribute to injury or loss of life.

• Category II - Failure to implement this recommendation will leave the rig/vessel out of compliance with regulatory requirements and possibly out of manufacturer's requirements. This category includes discrepancies that could cause high risk of downtime due to unreliable equipment condition that may compromise the drilling operation.

 

This incident frequency reminds us that safety issues must be a critical component of your rig survey program wherever drilling is conducted. In addition, these short surveys save customers many thousands of dollars. Land rig assessments generally require only four days.

Some of the most significant Category I recommendations that have been found on recent land rig inspections are listed below.

• Hammer unions are mismatched. The mismatched union may not be able to contain the working pressure of even the lowest pressure-rated component. An explosion of the union may result.

• Chicksan swivel joint bearings are seized.

• There are no gauges at the driller's console to monitor HP pump pressure readings; gauges are present only on the pump discharge lines at the pumps.

• Air volume tanks are homemade and not tested in compliance with API 510.

• The few pressure relief valves that are installed are not suitable for a high volume air application.

• Splines on the off-driller's side of drawworks to the Elmagco brake are excessively worn.

• Elevators are cracked and damaged in several areas. Cracks can be seen in the elevators. They are very difficult to close and occasionally come open on their own when the slips are set. There is no record of maintenance or NDT examinations having been conducted. Thus, determination of the elevators' fit for purpose is difficult.

Red arrows indicate cracks in elevator.

Many other discrepancies of a less critical nature have been identified on these land rig surveys. Even with the reduced criticality, these issues could still cause significant downtime for the rig.

The choke and kill manifold was not back flushed to clear all
the mud from the lines and valves. This could easily result in
severe pitting of the valves, which would require their replacement.

The Cameron Type U pipe ram block showed excessive signs
of corrosion and required cleaning before tolerances could be checked.

Other parameters should be considered when picking up a previously stacked rig. Many times land rigs are stacked in open fields, trucking yards, or other unprotected, outdoor areas. How long has the rig been stacked? Was it stored to prevent damage and deterioration from weather? What equipment has been "borrowed" by other rigs? If lacking equipment, where did the required machinery come from and how was it stored and maintained?

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