Schlumberger

Antiballing Coating

Eliminate Bit Balling in Clay/Shale Formations

Lyng Drilling offers a unique coating process called antiballing coating to combat bit balling, in which cuttings stick to the bit surface in water-reactive clay/shale formations.

Two mechanisms contribute to bit balling: mechanical and electrochemical sticking. A rough bit surface will increase the surface area and increase the adhesive forces. When the mud flow stops, or if a bit with poor hydraulic design is used, an electrostatic force may cause clays to stick in the bit surface. Once initiated, it is easier for clays to build up and eventually ball up the bit.

The solution was found in a unique coating process, where a metallic layer with highly specialized properties can be applied on the bit surface to eliminate bit balling.

Antiballing coating boosts ROP 25 m/h

In an 8 1/2 × 9 1/4-in section normally to be drilled entirely in the reservoir, a PowerDrive Xceed rotary steerable system (RSS) for harsh, rugged environments and a 9 1/4-in underreamer were used. The section was started in the Springar formation, known to cause bit balling problems in water-base mud.

In the first run, an 8 1/2-in polycrystalline diamond compact (PDC) bit without the antiballing coating was used on the PowerDrive Xceed tool. The first 3 to 4 m were drilled normally, but the ROP dropped down to approximately 5 m/h shortly after starting drilling. Attempts to change the drilling parameters had no effect, and the achieved dogleg severity with 100% steer force was well below the required 6°/30 m. Due to the inability to keep the well path on the planned trajectory and the lower-than-expected ROP, it was decided to pull out of hole (POOH). The bit had balled up.

In the next run, the Lyng LM6340D1 with antiballing coating was run on the same assembly and drilled the section to TD, achieving the desired dogleg severity and a 30 m/h average ROP.

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Unique Coating Process Combats Bit Balling

Antiballing Coating
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