Case study

Ace Drilling Centralizer rotates on liner providing stability to liner drilling directional BHA

National Oil Company selects Ace Drilling Centralizer (ADC)* to stabilize 7” liner drilling string in directional interval


  • Installed at the rig site within 2 hours by 1 trained installer

  • The liner was rotated approximately 54,000 times at speeds ranging from 30 to 80 RPM over a 13.5 hour period

This was the first run of the ADC for this operator, who is now pursuing further applications for this and other Ace products.

The challenge

Casing and liner drilling are recognised as two of the best methods to minimise drilling problems and secure total depth of troublesome intervals. Both methods involve drilling with the casing or liner string and either a drill bit attached to the string, or a retrievable BHA, which can be safely withdrawn through the string, upon reaching total depth, to isolate the BHA from hazards.

In applications, such as casing and liner drilling & reaming, and for rotating the string while cementing, many revolutions of the casing or liner string is expected. However, this typically causes drilling torque and wear to both the parent casing and the rotating casing or liner.

The solution

To minimize drilling torque and wear on the liner and parent casing, Ace Oil Tools developed the Ace Drilling Centralizer (ADC), a centralizer that rotates independently of the casing or liner string.  This tool was selected by the operator to run during its drilling test to evaluate performance.

The 7” ADC solid-body centralizer consists of a centralizer coupled with (2) Ace Ratchet Collars with extensions that fit under the centralizer. The centralizer rides on these extensions to prevent wear on the casing or liner. The robust design is rated to 90,000lbs axial force and contains no small parts that can fail, leading to major issues.

The ADCs can be ordered with an outer diameter to match the hole size drilled. In this case 8-1/4” was selected to run inside an 8-1/2” open hole.

The design of the curvature of the blades and the bypass slots can also be varied to meet specific requirements.

The result

To drill this interval, the ADCs were installed at the rig site within 2 hours by 1 trained installer. The pipe was later run into the hole where the liner was then used to drill just under 900’ directional interval. During this test, the liner was rotated approximately 54,000 times at speeds ranging from 30 to 80 RPM over a 13.5 hour period. The liner was pulled as scheduled .

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