This originally appeared in Oilfield Technology’s Drill Bit Design Q&A, used with permission.
Oilfield Technology invited multiple companies to share their knowledge on a variety of drill bit design topics. Ulterra’s Chris Casad, innovation manager, and Chris Gooch, product development manager, discussed the following topics:
- Cutter Configuration and Design
- Stability & Vibration Resistance
- Boosting ROP
Cutter Configuration and Design
Ulterra – Chris Casad:
Since the creation of the first synthesized diamond in 1954 by GE, cutter vendors and drill bit providers have been working to improve their cutters from the original formula to achieve more longevity and better cutting speeds. These improvements have come in all manner of shapes and techniques. The origins of some of the recent shaped cutters can be drawn all the way back to an expired patent in 1995, demonstrating that what is old can easily become new again. The most recent advancement in drilling efficiency for cutter layouts has come through SplitBlade™ bit designs, a technology that allows the placement of cutters to break the traditional limits of physics. By focusing on better cutter composition and implementing these enhanced cutters with new-style layout technologies, significant improvements have been made to the two fundamental diamond considerations in a drill bit: diamond volume and wear efficiency. Top of the line deep leached cutters are engineered to use the full potential of these cutters, using a technique called cutter overlap. One thing that has been proven by the recent trend of extended reach intervals is how far the diamond itself in modern PDC cutters has improved at combating abrasive wear. With such material improvement, service companies should not be looking to reduce the volume of the diamond per cutter – as cutter placement real estate is at a premium – but instead to use fully resolute whole cutters more efficiently with layouts that maximize the diamond to placement cost of each position. The future of every industry is dependent on sustainability, and it is the sustainable technologies that maximize the costs and benefits of their solutions that will continue to bear the most fruit and deliver the best value to operators.
Stability & Vibration Resistance
Ulterra – Chris Gooch:
When drilling a well, operators face the risk of bit and bottomhole assembly (BHA) damage or failure caused by vibration of the drill string. The same vibration is also a source of wasted energy which could otherwise be put towards drilling faster. In every drill bit design, the PDC bit designer aims to increase the bit’s stability and protect it from vibration damage. Although the bit is unlikely to be the root cause of vibration issues, there are things that can be done with its design that will help to reduce or even mitigate vibration. In the past, the drill bit industry concentrated on the passive reduction of vibration damage to the bit by adding features to protect the cutting structure. Ulterra has shifted focus and designed a cutting structure that actively dampens drilling forces by managing and re-directing them into a stable pattern. This has the useful side effect of creating a very stable bit, and the more stable it is under drilling conditions, the more efficient it will be. ‘Interfacial severity’ is a buzzword in the industry right now, because transitional drilling applications are notorious for low efficiency and damaging bits. Often the damage operators see is caused by vibration combined with uneven cutting forces as the bit pushes through different layers of rock hardness. The company designed a new technology, RipSaw™, that controls these cutting forces and helps reduce the vibration and damage by actively dampening the bit while still allowing movement and high engagement. In a recent macro-level field study in West Texas, US, which encompassed over 3200 bit runs on nearly 2150 wells in 2019, it was found that active damping technology increased durability by 25%, which led to a near 30% increase in run success. This new type of cutting structure design provides a valuable solution to vibration and control issues, allowing operators to reduce drilling damage and redirect valuable input energy.
Ulterra – Chris Gooch:
Improving performance is at the heart of any new drilling technology. For ROP in particular, it is important to consider the entire drill string – including the drill pipe selection and BHA components – in order to determine the best approach to boosting ROP. With this perspective, one can get an objective view of the different approaches that are available and their results. One approach that has been gaining momentum is to use 5.5 in. drill pipe in order to increase torque through the drill string. Designing a bit that can properly use this torque and translate it into additional ROP without running into stick-slip and reverse whirl complications is more complex than it seems. When time is money, as the adage goes, it is important to have technology in a bit that delivers performance on multiple fronts. Recently, in West Texas, Ulterra has seen an improvement in performance on intermediate runs in the Southern Delaware Basin. A new generation of SplitBlade drill bits have been breaking into new footage records and doing so with consistency in less time than offset runs of even a few months before. An example of this has been demonstrated by an Ulterra 12.25 in. SPL616 that went from drill-out past 8000 ft. Notably, this run also drilled over 6000 ft, a common performance barrier in this area, with an ROP of 110 ft/hr, putting this run 10% faster than even the average of the last 10 highest performing runs. Over the past year, drill bits equipped with SplitBlade technology to improve torque transfer, hydraulic management and cuttings evacuation have proven to be adept at boosting ROP in any number of drilling applications. By designing a drill bit that maximizes these parameters, operators have found new depths of performance with wider windows of operations than before. This lowers the difficulty of achieving the highest levels of performance and boosts ROP across multiple basins.