Schlumberger

Case Study: SHARC PDCs Outdrill Other Bits in West Africa with 194% Greater ROP

Top performing bits drill ultra-abrasive formation, averaging 3.5 ft/h ROP

Challenge: Using as few bits as possible, directionally drill a 12 1/4-in vertical section through a hard and extremely abrasive formation known to cause high bit wear.

Solution: Run a 12 1/4-in SHARC high-abrasion-resistance PDC drill bit fitted with ONYX PDC cutters and run it on a directional drilling assembly.

Result: Used four bits to drill the 12 1/4-in vertical section, and of those, the two SHARC PDC bits outdrilled the other two bits, surpassing their ROP by 194%.

Increased bit durability required for an ultra-abrasive application

An operator working off the coast of Ghana, trying to drill 12 1/4-in vertical sections through hard abrasive sandstone interbedded with shale and siltstone, was experiencing adverse bit wear. The unconfined compressive strength (UCS) of these formations ranges from 9,000 to 15,000 psi and up to 21,000 psi in short, very hard strips. Trying to drill 450-ft intervals under such conditions was taxing bit durability and reducing drilling performance. The operator wanted a bit that could drill longer, thereby reducing the number of trips being made to replace bits.

Application-specific cutting structure to combat wear

For this application, Smith Bits recommended using a 12 1/4-in MDSI816LBPX PDC bit with SHARC off-profile backup cutters and ONYX abrasion-resistant cutters. The operator drilled the same interval using four bits, all of which were run on a directional drilling assembly; two were SHARC bits.

Increased durability significantly increases drilling performance

Two of the bits used combined to drill 74 ft of the section at the identical ROP of 1.8 ft/h. Upon being pulled, these bits were found to be completely cored or rung out. The SHARC bits drilled 381 ft of the section while sustaining a minimum amount of cutting structure wear and delivering much better performance: The first drilled 234 ft at an ROP of 4.5 ft/h and the second SHARC bit drilled 147 ft at an ROP of 2.5 ft/h. This represents a 3.5 ft/h average, surpassing the other bits’ ROP by 194%.


Download: SHARC PDCs Outdrill Other Bits in West Africa with 194% Greater ROP (0.51 MB PDF)

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SHARC Bits with Abrasion-Resistant ONYX Cutters Combat Bit Wear

The 12 1/4-in MDSI816LBPX SHARC PDC bits drilled longer, with 194% greater ROP
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