| Autor: |
Jain, Jayesh R., Ricks, Gregory, Baxter, Benjamin, Vempati, Chaitanya, Peters, Volker, Bilen, Juan Miguel, Spencer, Reed, Stibbe, Holger Stibbe |
| Předmět: |
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| Zdroj: |
SPE Drilling & Completion; Dec2016, Vol. 31 Issue 4, p286-294, 9p |
| Abstrakt: |
Since they were first introduced to the market decades ago, polycrystalline-diamond-compact (PDC) bits have undergone numerous technological improvements. One such example is depth-ofcut (DOC)-control technology. Introduced in the early 2000s, this technology emerged as an effective means to mitigate torsional vibrations by managing bit aggressiveness. Today, however, the drilling industry faces the task of drilling diverse sections of the well with a single bit. This is a significant challenge for fixed PDC bits, requiring a compromise that limits vibration mitigation in some sections of the well and/or top-end rate-of-penetration (ROP) performance in other sections. This paper presents an innovative PDC bit that can self-adjust its DOC-control characteristics to the constantly changing drilling environment and mitigate vibrations while delivering improved ROP. The self-adaptation is accomplished through a passive hydromechanical feedback mechanism encapsulated in self-contained cartridges that are installed inside the bit blades. The DOC control elements mounted on the cartridges respond to the external loads through strategically designed rate-sensitive retraction and extension strokes. During unfavorable dynamic events, the elements engage with the formation and mitigate dysfunctions. During normal steady-state drilling, the elements gradually adjust their exposure to enable fast and efficient drilling. The operating principle of self-adjusting PDC bits is first demonstrated through laboratory drilling tests under confining pressure by use of full-scale prototype bits. The testing was expanded to a research well in the field to assess the ability to self-adapt and mitigate stick/slip vibrations. The field-test facility enables a controlled yet realistic environment with reduced uncertainty that is often not available in the field. The tests compare stick/slip tendencies of bits by building stability maps in weight-on-bit (WOB) and rev/min space by use of downhole measurements under similar operating conditions. Bits with the self-adjusting mechanism led to fewer instances of stick/slip than fixed PDC bits in multiple formation types. Self-adjusting bits significantly expanded the stable operating region and enabled operation at higher ROP. The ability of the DOC-control elements to continuously selfadjust their exposure overcomes several other limitations posed by the fixed nature of traditional DOC control. The technology does not require a fixed predesigned exposure; prevents overengagement because of its ability to retract; and eliminates iterative tuning of DOC control currently in practice. The technology is also anticipated to absorb impacts in interbedded formations and reduce damage from improper starting procedures. With many PDC-bit drilling applications being torque-limited, the technology opens up several possibilities to reduce drilling costs. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Supplemental Index |
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