Published: 01/18/2013
Published: 01/18/2013
The lithology associated with applications in northern Utah's Wasatch formation consists of difficult interbedded sand and shale with a UCS that ranges from 2,000 to 30,000 psi. From 5,900- to 10,500-ft TVD, the formation is characterized by sandstone with a UCS of 10,000 to 15,000 psi. It is interbedded with soft shale that has a UCS of 2,000 to 5,000 psi and hard sandstone stringers with a UCS of 25,000 to 30,000 psi.
To increase drilling performance of the 7 7/8-in Mi616 PDC bits drilling in this area on a directional BHA using a PDM with a 1.5° bend angle, MiZ616 PDC bits with a Stinger element were tried with the following goals: increase ROP, improve cutting structure durability in high weight-on-bit applications (30,000 to 50,000 lbf), and reach section TD in one run.
The Stinger element has twice the diamond thickness of conventional PDC cutters and is manufactured from synthetic diamond material engineered to provide superior resistance to abrasive wear and impact loading. Combining this capability with the Stinger element's unique conical geometry resulted in a cutting element that can significantly enhance a PDC bit's durability.
To ensure that placement of the Stinger element at the PDC bit's center would maximize drilling efficiency, engineers used IDEAS integrated drillbit design platform to further optimize the cutting structure. This effort included selectively abbreviating the blades that held the PDC bit's low-velocity center cutters and placing the Stinger element at the center of the PDC bit's cutting structure.
By opening up the center of the cutting structure, a stress-relieved rock column is allowed to develop at the bit's center during drilling. As the Stinger element engages it, the rock column is continuously crushed and fractured, thereby improving drilling efficiency. Efficiency is increased still further because bits with a Stinger element have fewer cutters, so there is less division of the weight on bit. This configuration has proven to maximize drilling efficiency, increase stability, and reduce vibration.
A MiZ616 PDC bit with a Stinger element run on a directional BHA drilled a 6,050 ft, 7 ⅞-in section to TD in one trip. After drilling 43 hours, the bit was pulled out of the hole in excellent dull condition: 1-2-BT-C-X-IN-WT-TD. Beyond demonstrating much greater durability, when compared with the average from the four best offset drilling performances, the PDC bit with a Stinger element had a 14% greater ROP.
Challenge: Drill 7 ⅞-in vertical section of at least 6,000 ft through formations with the wide-ranging unconfined compressive strength (UCS) that compose Utah’s Wasatch formation at a greater ROP and with fewer bits.
Solution: Run a 7 ⅞-in MiZ616 PDC bit with a Stinger conical diamond element on a positive displacement motor (PDM) with a 1.5° bend angle.
Results: Drilled a 6,050-ft, 7 ⅞-in section to TD in one trip, and when compared with bits that had the best average ROP in four offset wells, the bit with a Stinger element increased ROP 14%.
