Bit designers use the well-established practice of placing depth-of-cut (DOC) control features at strategic heights from the cutter profile to selectively manage drill bit aggressiveness and to maximize drilling performance. But, until now, the elements used for depth-of-cut-control were a fixed part of the bit. An innovative new feature enables compact element replacement and/or adjustments at the rig site using a mechanical locking design. The driller can quickly adjust the bit responsiveness before each run, if wanted, to optimize performance factors such as rate of penetration and tool face control. This paper describes the benefits, ease of use, positive results and reliability of this new technology with examples from multiple applications for a variety of bit designs.
The final design was selected and validated based on a number of evaluation methods including concept screening tests, simulated laboratory drilling tests and field tests. The initial screening tests evaluated the ease of compact installation and removal for various concepts using a test block. Full bit testing using a full-scale, high-pressure, downhole drilling laboratory evaluated installation, integrity and aggressiveness response changes using compact height adjustments. Finally, multiple field tests on wells in North American applications of the Eagle Ford, Marcellus, and DJ basin formations provided data to refine the mechanical design and improve manufacturing processes to achieve a robust technology.
Field tests proved the new design to be highly reliable, with drilling performance that matched or exceeded the performance of bits with standard brazed compacts in the same fields. This new design provided the unique ability to rapidly optimize bit responses. This paper describes the technical lessons learned, guidelines for use and tools developed to maximize the benefit from this innovative new feature.
This new method enables compact element installation and removal within fifteen minutes on the rig site for the purpose of repair or aggressiveness modification. In contrast, traditional methods of DOC control include long lead times to alter bit design, manufacturing and delivery. Drillers can reap the immediate benefits of improved bit performance by changing bit design on the rig site using direct feedback of bit aggressiveness and steerability between runs without needing multiple bits on site. Ultimately, this new bit technology provides improved drilling performance and greater efficiency for the operator.
Historically polycrystalline diamond compact cutters have consisted of a planar cutting face on a cylindrical diamond table. For decades industry has been aware of the potential drilling performance gains from forming these cylindrical cutters into other geometrical shapes. These early generation shaped cutters did not gain traction due to limitations in diamond technology, and high manufacturing costs associated with shaping the cutters. Recently PDC drill bits with shaped cutter designs are becoming more prolific in worldwide drilling applications. Often, the novelty in the design of the cutter shapes is enticing enough to merit opportunities for field runs. However, without an informed understanding of shaped cutter behaviors, there is risk of diminished drilling performance if the cutter shapes are not applied properly to the bit and application. The objective of this paper is to develop methods to evaluate two critical behaviors for shaped PDC cutter designs, overload integrity and aggressivity, and apply these methods to a full bit drilling model.
The cutter overload integrity characterization methods are developed using finite element analysis and the aggressivity characterization is based on high pressure visual single point cutter laboratory test data. The information is fed into a full bit drilling numerical model to predict bit performance and ability to avoid cutter breakage in a simulated drilling environment, accounting for factors such as lithology, interbedded transitions, bottom hole assembly type, and operating parameters. The models enable optimization of shaped cutter design and fit for purpose cutter selection.
The full bit model is tested and validated against field runs. Case studies include interbedded drilling in the Haynesville and Permian Basins. In both applications, bits were run with different shaped cutter designs, using drilling performance and dull photos to compare to the model outputs. ROP gains of 35% were seen in the Haynesville application, while the cutter survival rate more than doubled in the Permian application by using optimally selected shaped cutters.
The methods presented in this paper provide new pathways for shaped cutter design and selection. Digital tools are demonstrated to perform the multi-faceted analysis efficiently for pre-well planning and post-run analysis.
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