A Model for Borehole Oscillations

Pastusek, Paul; Brackin, Van

doi:10.2118/84448-ms

Cited by 70 publications

(38 citation statements)

References 11 publications

(13 reference statements)

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“…Internally the Limiter Redesign Process was renamed Fast Drill The FDBM initiative was the continued evolution of the Fast Drill Process. Research and field trials confirmed that poor borehole quality [12][13][14][15][16][17][18] (enlargement, borehole patterns, hole out of round, ledges, etc.) contributed significantly to drilling dysfunction and inadequate hole cleaning.…”

mentioning

confidence: 89%

Maximizing Capital Efficiency by Expanding the Limiter Redesign Process to Flat Time Operations

et al. 2014

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The operator's drilling efficiency program has been expanded to a Limiter Redesign Process that seeks to optimize all rig time, including flat time. As drilling efficiency gains have been achieved, flat time now accounts for roughly 80% of the total rig time and approximately 70% of the total cost of drilling and completions operations; leaving 20% of rig time for drilling. This fact led to the generation of a comprehensive Flat Time Reduction (FTR) program.The Fast Drill Process has become a well-known workflow to identify hole-making limiters and mitigate them through "relentless redesign to the economic limit of performance". Efforts to increase drilling efficiency continue, and this process has yielded a continuous increase in the overall footage per day and a reduction in flat time within individual hole sections.To address operations that do not include drilling of rock, the operator has launched a similar effort and workflow process which focuses on "flat time" portions of the well construction process. This has become a key focal point in the organizations approach to maximize capital efficiency. The Flat Time Reduction process provides an environment in which operations are optimized while further enhancing a workplace where "Nobody Gets Hurt."This process is yielding significant savings globally and has been accomplished through planning, "real-time" recognition and response, collaboration with service providers, and a focus on Non-Productive Time (NPT) reduction while continuously improving safety performance. Field applications of limiter redesign are discussed in this paper. The purpose of this paper is to present the current status and specific approaches being used to reduce flat time and share the workflow process.In 2004, the operator started a pilot program to determine if drilling performance could be improved by analyzing and reacting to trends in Mechanical Specific Energy (MSE) 1, 2, 3 by rig site personnel on a real time basis. MSE is a performance measurement parameter that approximates the bit's drilling efficiency and is a function of the weight-on-bit (WOB), surface torque, bit rotation per revolution (RPM) and the rate of penetration (ROP) for a given hole size. When the bit is drilling efficiently, MSE will be steady and will approximate the rock's confined compressive strength. When dysfunction occurs, MSE increases

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confidence: 89%

Maximizing Capital Efficiency by Expanding the Limiter Redesign Process to Flat Time Operations

et al. 2014

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“…(Pastusek and Brackin 2003) When the near bit stabilizer (or other contact point) encounters a small ledge or perturbation in the borehole, it is pushed to the side as it drills past this perturbation. This lateral force causes the bit to cut sideways at the same time.…”

Section: Vibrationally Induced Borehole-pattern Limitersmentioning

confidence: 99%

“…While whirl mitigation is important, there are three other major factors that can be controlled by design or operational practices. Increasing the ROP per revolution will reduce the number of gauge trimmer passes required to drill a given hole section and thus there will be less total side cutting (Pastusek and Brackin 2003). The higher the ROP, the smoother the hole will be.…”

Section: Vibrationally Induced Borehole-pattern Limitersmentioning

confidence: 99%

Borehole-Quality Design and Practices To Maximize Drill-Rate Performance

Dupriest¹,

Elks²,

Ottesen³

et al. 2011

SPE Drilling &Amp; Completion

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In 2005, the operator implemented a workflow that ensured that drilling-performance limiters were identified, redesigned, and extended continuously. The use of mechanical-specific-energy (MSE) surveillance to address bit limiters and dysfunction has been published previously. The purpose of this paper is to discuss additional practices that have been developed to extend the nonbit performance limiters, particularly those related to borehole quality.There have been more than 40 nonbit performance limiters identified and redesigned globally. While these are diverse, those with the greatest global impact were found to be tied directly to borehole quality. Consequently, in 2008, the performance-management workflow was modified to increase awareness of borehole quality as a performance limiter. The result was that acceptable borehole quality became defined as that which would not limit footage per day. Quality is now redesigned to the "economic limit of performance" in the given interval. The economic limit of performance is a significantly higher standard than the common industry objective for borehole quality, which is to achieve low trouble time and to run casing successfully.The average drilling footage per day drilled by the 23 operations that have been active since the performance-management process was implemented has improved by approximately 63%. Instantaneous drill rates have typically increased 100-300%. Advances in bit and nonbit limiters appear to have contributed equally, and the majority of the gain in nonbit limiters has come from improved borehole quality. Other gains have come from related limiters, such as an increased understanding of the manner in which cuttings transport and tripping operations are controlled by borehole quality.The paper discusses the technical models that are used to understand the major borehole limiters, the engineering design, and the real-time practices that have been developed, as well as the field results.

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“…Borehole spiraling is an expression of the self-excited oscillations of the bit tilt that arise from the geometric influence of the stabilizers on the drilling direction at the bit as they interact with the borehole (Pastusek and Brackin 2003;Perneder 2013;. Indeed, as the BHA is constrained by the stabilizers to conform to the borehole, the resulting geometric constraints tend, under certain conditions, to amplify progressively, at the bit, local perturbations in the borehole geometry.…”

Section: Introductionmentioning

confidence: 99%

“…The self-perpetuating nature of the spiral was first discussed by Pastusek and Brackin (2003), who also described how the geometry of the BHA could lead to a growing oscillating pattern in the borehole trajectory. Downton (2007) demonstrated that a rigid BHA having three-point contact with the borehole is always directionally unstable, except for a few discrete configurations.…”

Section: Introductionmentioning

confidence: 99%

Spiraled Boreholes: An Expression of 3D Directional Instability of Drilling Systems

Marck

Detournay

2015

Day 1 Tue, March 17, 2015

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The occurrence of borehole spiraling is predicted by analyzing the delay differential equations that govern the propagation of a borehole. These evolution equations for borehole inclination and azimuth are obtained by considering the following three model components: (i) a bit/rock interaction law that relates the force and moment acting on the bit to its penetration into the rock; (ii) kinematic relationships that describe the local borehole geometry from the bit penetration; and (iii) a beam model for the bottom-hole assembly (BHA) that can be used to express the force and moment at the bit from the external loads applied on the BHA and the geometrical constraints arising from the stabilizers conforming to the borehole geometry.The analytical nature of borehole propagation equations makes it possible to conduct a stability analysis in terms of a key dimensionless group that controls the directional stability of the drilling system. This group depends on the downhole weight on bit (WOB), on properties of the BHA, on the bluntness of the bit, and on parameters characterizing its response. The directional stability of a particular drilling system can be assessed by comparing the magnitude of this group with a critical value that depends only on the BHA configuration and on the bit walk. If this dimensionless group, which depends on the actual drilling conditions, is less than the bifurcation value, the system is deemed to be directionally unstable, and borehole spiraling is likely. Stability curves for an ideal BHA with two stabilizers are shown to depend on the bit walk. An application to a field example is discussed. Borehole simulations, based on solving the equations of propagation, also are presented to illustrate that, for unstable systems, the model reproduces spiraled boreholes with a pitch, comparable to what is observed in the field.

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A Model for Borehole Oscillations

Cited by 70 publications

References 11 publications

Maximizing Capital Efficiency by Expanding the Limiter Redesign Process to Flat Time Operations

Maximizing Capital Efficiency by Expanding the Limiter Redesign Process to Flat Time Operations

Borehole-Quality Design and Practices To Maximize Drill-Rate Performance

Spiraled Boreholes: An Expression of 3D Directional Instability of Drilling Systems

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