Testing of New PDC Cutter Edge Geometry Doubles Penetration Rate and Reduces Torque

Barton, Steven Paul; Setlur, Deepthi Raj; Clegg, John Martin

doi:10.2118/116173-ms

Cited by 7 publications

(2 citation statements)

References 13 publications

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“…3. The effect of altered chamfer edge geometry was presented by Barton et al (2008) providing increased ROP, while also seeing a reduction in torque as the rock is drilled more efficiently. It was confirmed that stability of the PDC bit design was not affected by this change in terms of the cutter aggressiveness, hence it was thought to be a better way of introducing a more aggressive and efficient PDC cutting structure to the hard chalk application.…”

Section: A Different Approach To Bit Selectionmentioning

confidence: 99%

Faster ROP in Hard Chalk: Proving a New Hypothesis for Drilling Dynamics

Akutsu

Rødsjø

Gjertsen³

et al. 2015

SPE/IADC Drilling Conference and Exhibition

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A well documented path to improving overall efficiency in project execution is through an integrated team approach which involves both the operator and the service suppliers. This paper describes what can be achieved when such a team adopts a fearless approach to new technology, and dares to think outside existing conventions. To be more specific, the paper covers the engineering, planning, and execution of a HTHP exploration program in the central North Sea by a Norwegian operator.Large areas of the North Sea contain the Cretaceous period of sediments which comprise of a massive hard layer of chalk that historically has posed a major drilling risk and expense to operators in the area. To mitigate expected problems an integrated team was gathered to thoroughly analyze drilling records and lessons learned from previous offset wells and re-engineer the drilling process with the aim of minimizing cost and uncertainty when drilling the most challenging chalk interval.The paper presents the hypothesis that formed the basis for the team effort, and the measures implemented based on said hypothesis. This includes an unconventional bit selection and the use of modern vibration measurement technology and mitigation techniques, as well as a key electro-mechanical modification of the advanced logging and directional suite completed by the lead service provider. The discussion and reasoning behind each step is included and the method was repeated in several wells with the same results, verifying the validity of the findings and making the paper a valuable input for drilling hard chalk.The nominal result from applying the new methodology was a doubling of the rate of penetration (ROP) in the harder layers, and the entire section of problematic strata was drilled in one single bit run. Drilling time was reduced by 12 days when compared to average figures from recent offset wells representing an estimated cost saving of 15 -20% on the overall well budget. The method and savings presented are primarily of interest to stakeholders in the central North Sea, but can also be applicable to other areas with hard chalk and stringers with similar characteristics.

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Section: A Different Approach To Bit Selectionmentioning

confidence: 99%

Faster ROP in Hard Chalk: Proving a New Hypothesis for Drilling Dynamics

Akutsu

Rødsjø

Gjertsen³

et al. 2015

SPE/IADC Drilling Conference and Exhibition

View full text Add to dashboard Cite

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“…While drilling the Lance Pool it is common to penetrate over 30 hard sandstone units. The sand-shale sequences found in the upper, middle, and lower Lance have unconfined compressive strengths ranging between 10 and 20 ksi, with confined compressive strengths averaging between 20 and 30 ksi, and as high as 100 ksi (Barton et al 2008) (Gent et al 2009). Much of the bit dysfunction observed is associated with the transition between softer and harder strata.…”

Section: Introductionmentioning

confidence: 99%

Successful Design and Operational Practices to Mitigate Common Bit Damage Mechanisms in Hard Laminated Formations

Mann

Dupriest

Noynaert

2016

IADC/SPE Drilling Conference and Exhibition

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An extensive data collection, training, and field trial program was implemented to develop practices to mitigate a common form of bit damage in hard laminated formations. Analysis improved understanding of the physical phenomena causing the damage and a variety of operational practices and technical redesigns have resulted in reduced levels of bit dysfunction, increased bit life, as well as increased drill rate.In hard laminated formations bit life is often limited by severe damage occurring in only the two outside cutter rows on the bit shoulder (Fig. 2). In 2014, the operator began a performance improvement program in the Greater Green River Basin, which included investigating the physical process through which this damage was occurring. High frequency downhole vibrations data was recorded on multiple wells at points throughout the BHA as well as at the bit. The data revealed that synchronous torsional oscillations (STO) were occurring, and these were enabling high lateral bit whirl. While the root cause is a form of stickslip, the damage observed has the appearance of whirl. Analysis showed that as the bit drilled the laminated interfaces, higher modes of STO may occur along with the basic primary torsional oscillation mode. STOs occur when the drillstring is rotated at specific speeds that cause higher frequency torsional resonance to develop in addition to the primary large torque and speed cycles that rig crews observe with stickslip. The high frequency oscillation within the drillstring had small amplitude, but it created sufficient loss of depth of cut that allowed the bit to move freely in the lateral direction, enabling high lateral vibrations. The effect is particularly pronounced in hard laminated formations where the depth of cut has already declined at each transition due to the increase in rock hardness.It has generally been observed by the industry that high levels of whirl are rarely seen simultaneously with high stickslip. The observations in the described case are significant in that they may explain those instances where they are seen together. Also, the operations personnel are generally not aware that primary and higher order torsional oscillations may be excited by specific rotary speeds and that new field practices are needed to identify and avoid these in real time. Field trials were conducted that included RPM step tests to determine non-resonant rotational speeds, WOB step tests to avoid the onset of full-stick, bits designed with depth-of-cut control to reduce torsional oscillation, roller reamers to ensure stabilizer drag wasn't contributing to stickslip, and extension of bit gauge length to reduce the lateral movement of the bit in response to lateral force from the BHA.Direct measurement, using high frequency downhole data, showed it is possible to achieve moderate reduction in bit dysfunction in hard laminated formations through these changes in practices and design. Greater gains might be expected with drillstrings having higher torsional stiffness than the 14,000 ft of 4 inch pip...

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New Generation Thermally Stable Cutters Deliver High Penetration Rates While Maintaining Durability in the Troll Field, Norway

Roberts

Ludvigsen

Haereid

2013

SPE/IADC Drilling Conference

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One of the main challenges drilling within the Troll field, offshore Norway is maintaining a high Rate of Penetration (ROP) while drilling through hard calcite cemented stringers (Jones et al. 2008a; Gunderson et al. 2008). The calcite distribution in this field is complex and can be difficult to predict, while it is easy to maintain a high ROP when drilling the sand sections between the stringers. Early wear or damage to the cutting structure limits the bit's ability to apply sufficient point loading to efficiently cut through the calcite and remaining lithologies, so the key aspects in solving this challenge is to retain the sharpness of the Polycrystalline Diamond Compact (PDC) cutters and minimize the risk of impact damage when hitting these thin inter-bedded stringers at high penetration rates. Following an in-depth study of the application, the drill bit design evolved following several iterations that included computational fluid dynamics to optimize fluid impingement angles and reduce fluid induced shear stress on both the bit body and cutter substrates. Torque control components were introduced to improve the design's response to weight-on-bit, minimize stick-slip and improve directional response. Detailed laboratory tests were conducted to investigate a new edge preparation applied to a new thermally stable PDC cutter, and the cutter-rock interaction was modeled to investigate complex wear, involving impact, abrasion and thermal mechanisms, while drilling these highly inter-bedded formations. The results of this research led to new cutter and bit technologies which have proven that the combination of improved thermal resistance and more efficient cutter geometry enables the cutters to stay sharp while drilling through the hardest stringers and maintain greater durability to complete the section. The improved designs have now drilled further and faster than any previous attempts, resulting in significant cost savings for the operator.

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Testing of New PDC Cutter Edge Geometry Doubles Penetration Rate and Reduces Torque

Cited by 7 publications

References 13 publications

Faster ROP in Hard Chalk: Proving a New Hypothesis for Drilling Dynamics

Faster ROP in Hard Chalk: Proving a New Hypothesis for Drilling Dynamics

Successful Design and Operational Practices to Mitigate Common Bit Damage Mechanisms in Hard Laminated Formations

New Generation Thermally Stable Cutters Deliver High Penetration Rates While Maintaining Durability in the Troll Field, Norway

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