Optimization of Deep Drilling Performance with Improvements in Drill Bit and Drilling Fluid Design

Black, A.D.; Bland, R.G.; Curry, David; Ledgerwood, L. W.; Robertson, Homer; Judzis, Arnis; Prasad, Umesh; Grant, Tim

doi:10.2118/112731-ms

Cited by 23 publications

(9 citation statements)

References 6 publications

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“…Whitfill et al (2002) showed by review of field data that penetration rates in salt formations tended to be higher with synthetic based fluids than water based fluids. There is abundant evidence that drilling fluid composition influences the drilling process and drilling efficiency under otherwise constant borehole pressure and operating parameters, for instance as indicated recently by Black et al (2007) and Curry et al (2008). These latter studies showed markedly higher penetration rates and lower mechanical specific energy levels with PDC bits in Crab Orchard sandstone, a hard and tight sandstone, and Mancos shale, a moderately hard and relatively water insensitive shale, when drilled with base oil than when drilled with an invert emulsion field mud based on the same fluid but containing brine emulsion droplets, weighting material, viscosifying and fluid loss control agents.…”

Section: Discussionmentioning

confidence: 97%

The Effect of Borehole Pressure on the Drilling Process in Salt

Curry

Lourenco

Ledgerwood

et al. 2015

SPE/IADC Drilling Conference and Exhibition

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Wells penetrate long intervals of salt to access hydrocarbon reservoirs in many locations. High mud weights are frequently used to stabilise the wellbore while drilling through salt formations. High borehole pressures reduce penetration rates in many sedimentary rocks. This effect is significant and contributes greatly to the low penetration rates and high costs associated with deep drilling. This paper presents the results of an integrated laboratory study of the effect of borehole pressure on the drilling process in salt. The study included full-scale laboratory drilling tests, visual single-point cutter tests and triaxial compression tests. The drilling tests were performed using a Polycrystalline Diamond Compact (PDC) bit and a synthetic-based drilling fluid typical of field practice. The visual single-point cutter tests used a clear drilling fluid, enabling observation and video recording of the salt cutting process at elevated borehole pressures along with simultaneous measurement of the cutting forces.The effect of borehole pressure on drilling salt is seen to be small; increasing borehole pressure does not reduce penetration rates in salt as much as it does in many other sedimentary rocks. In contrast to other sedimentary rocks, salt deforms plastically to relatively large strains in compression without loss of mechanical integrity, even at low confining pressures. In addition, the shear stress to achieve a given strain does not increase greatly with confining pressure. Rock cutting forces in the single-cutter tests increased only moderately as borehole pressure was increased from 300 to 6,000 psi. Full-scale bit penetration rates also decreased by relatively small amounts over the borehole pressure range investigated (1,000 to 6,000 psi). Mechanical specific energy levels showed corresponding small increases. These levels, however, were consistently much higher than the compressive stresses required to cause even large strains at a confining pressure equivalent to the borehole pressure. Observations of the deformation and cutting processes in salt combined with results of finite-element analyses of rock and metal cutting explain the low sensitivity to borehole pressure of halite penetration rates and its relatively high specific energy.This study fills a gap in industry knowledge of pressure effects in drilling and sheds light on the processes involved in drilling rock salt. The key practical conclusions are that penetration rates and mechanical specific energy in salt are not greatly influenced by borehole pressure. Consequently, if a high borehole pressure is required to stabilise the wellbore through a salt formation, there is little penetration rate penalty to be paid, except perhaps if increasing the mud weight involves significant changes to the drilling fluid properties other than its density. The comparison of results from visual single point cutter and full-scale bit tests suggests, unsurprisingly, that reducing bit cutter density and modifying drilling fluid properties may both offer routes to ...

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Section: Discussionmentioning

confidence: 97%

The Effect of Borehole Pressure on the Drilling Process in Salt

Curry

Lourenco

Ledgerwood

et al. 2015

SPE/IADC Drilling Conference and Exhibition

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“…One is to maintain focus on bit torque instead of WOB when drilling with PDC bits. Torque translates directly to ROP for a given rotary speed (Black, et al, 2008), and a target value of 5,000 ft-lb has been used with great success. A second lesson is to mitigate stick-slip by decreasing WOB instead of increasing RPM beyond 120 RPM when drilling hard, abrasive rock; the loss of instantaneous ROP while drilling a few feet of hard rock is usually regained in the softer rock beneath it by preserving the cutting structure.…”

Section: Postwell Analysismentioning

confidence: 99%

A Systematic Approach to Performance Drilling in Hard Rock Environments

2011

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The Haynesville shale gas play in North Louisiana poses a number of significant technical challenges. One of the most daunting is penetrating the hard, abrasive Hosston sandstone-shale sequence and hard Knowles limestone in the intermediate section of the overburden. The high strength and interbedded nature of these formations trigger bit and drillstring vibration that can lead to short, slow bit runs and unacceptably high cost per foot.The operator applied a systematic Drilling Efficiency Optimization (DEO) approach encompassing well planning, well execution and post-well analysis to drive performance improvement through these formations. Optimization efforts focused on polycrystalline diamond compact (PDC) bit design, bit hydraulics, positive displacement motor (PDM) selection, soft torque rotary system (STRS) utilization, bottom hole assembly (BHA) design and active management of drilling parameters. Combined, these efforts reduced cost per foot and days per thousand feet by over 50% while drilling approximately 70 wells over a two year period.

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“…Phase-2 laboratory drilling tests were conducted and reported (Black et al 2008;Black and Judzis 2003). These tests set out to examine the impact of several factors including alternative drilling-fluid chemistries and weighting materials; PDC-bit-design options, such as bit profile and blade count, and impregnated-bit-grit size.…”

Section: Impact Of Bit Design and Mud On Ropmentioning

confidence: 99%

“…The rock tested was the same as during the first phase. The results of the second phase are provided, were published, and presented in 2008 (Black et al 2008;Black and Judzis 2003).…”

Section: Introductionmentioning

confidence: 99%

Optimization of Deep-Drilling Performance—Benchmark Testing Drives ROP Improvements for Bits and Drilling Fluids

Judzis

Black

Curry

et al. 2009

SPE Drilling &Amp; Completion

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A critical cost in future deep-oil and -gas recovery is the cost to drill a well. This cost is dominated by the rate of penetration (ROP) that becomes increasingly important with increasing depth. Improving the technology of drilling and increasing the ROP was the object of full-scale laboratory testing conducted under a joint industry and Department of Energy (DOE) program titled "Improving Deep Drilling Performance" (Black and Judzis 2003). Simulations of deep-well drilling in the Arbuckle play and the Tuscaloosa trend were accomplished during 16 full-scale, high-pressure tests using four different 6-in. drill bits, three types of rock, and five different drilling fluids.This paper describes what is believed to be the first set of fullscale laboratory drilling tests yet performed at bottomhole pressures in excess of 10,000 psi. Accomplishments of the testing and analysis include the following:• Laboratory data was compared with field data to confirm that the simulated laboratory conditions provided similar results to what would be expected in the field.• ROP reductions were significant when "mudding up" at high bottomhole pressures.• Polycrystalline-diamond-compact (PDC) bits provided substantially higher ROP performance than impregnated or rollercone bits in the environment of this study.• The relationship between ROP and confined-rock strength is not a simple function of bottomhole pressure alone.• The mechanical specific energy (MSE) when drilling at high bottomhole pressure is often substantially higher than the rock's compressive strength, even when the bit is drilling efficiently.• Fluid invasion of intact rock and of rock broken up by the bit's cutting structure seems to play a major role in controlling ROP at these high bottomhole pressures.• Drilling-fluid compositions and properties that promote invasion without provoking formation damage, and bit-design features that facilitate the removal of rock debris from the hole bottom, hold promise for improving drilling efficiency in hard rock drilled at high bottomhole pressures.

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Optimization of Deep Drilling Performance with Improvements in Drill Bit and Drilling Fluid Design

Cited by 23 publications

References 6 publications

The Effect of Borehole Pressure on the Drilling Process in Salt

The Effect of Borehole Pressure on the Drilling Process in Salt

A Systematic Approach to Performance Drilling in Hard Rock Environments

Optimization of Deep-Drilling Performance—Benchmark Testing Drives ROP Improvements for Bits and Drilling Fluids

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