Drill Bits (Tricone & PDC): 6-Signal Field Guide

This document describes post-run evidence, dull condition review, failure hypotheses and what’s learned for the next run. The approved drilling program, controlled supplier documents and responsible engineering authority remain the major controls.

Drill bits (Tricone & PDC) should be reviewed based on field evidence rather than comparing a new design with an old one. A useful question to ask after a run is which dull condition, hydraulics, and operating response can help explain failure evidence and guide one controlled next-interval change.

Decision boundary: This guide describes dull evidence, damage location, synchronized run records, failure hypotheses, and next-run review. The existing Drill Bits (Tricone & PDC) solution page remains the owner for available design options, supply scope, customization, lead time, and quotation.

Don’t arrive at a root cause from a dull code or photo alone. The starting point is always six evidence signals and naming what’s unknown. Carry one documented hypothesis and contingency into the next run review.

That boundary is important because drill bits (Tricone & PDC) serve two different reader needs. A buyer needing products requires a configuration and supply discussion on the commercial page. A post-run reviewer in oil and gas needs a way to connect damage location, downhole dysfunction, hydraulics, dull condition, and time- and depth-aligned records.

The method below may conservatively cover types of drill bits in the drilling industry where tricone and PDC comparisons help diagnose the returned bit; it doesn’t provide universal weight on bit tables, state that one family always drills faster, or consider a certificate as evidence of field performance. Published data from lab and field tests are kept at test conditions. The named frameworks are tools for completeness of the record, and aren’t standards or guaranteed root-cause models.

Crushing, Chipping, and Shearing: Forensic Context for What the Rock Sees

Tricone indentation and PDC shearing explain different damage exposure; Sandia research cautions against inferring cause from wear alone.

A tricone tooth creates a concentrated indentation and chips rock as the cones rotate. A PDC cutter, the diamond cutting element held in the bit body, removes rock by means of a tangential shear. The path of the energy and the means of survival are different, but failure also depends on confinement, rock abrasiveness and hardness, discontinuities, cleaning, heat, and dynamics of drillstring.

Condition	Rock-removal response	Damage exposure	Record to inspect
Continuous, drillable interval	Sustained cutting may reward a fixed-cutter layout	Heat and wear can accumulate	ROP, torque, MSE, temperature context
Abrupt interbed	Depth of cut and contact force change quickly	Impact, chipping, and dynamic excitation	Depth-matched lithology and vibration
Fractured rock	Contacts alternate between support and release	Shock and uneven loading	Losses, torque, vibration, and dull location
Abrasive rock formation	Sharpness and gauge can erode over footage	Wear flats, broken inserts, gauge loss	Mineralogy, gauge measurements, photos
Cleaning-limited bottom	Cuttings interfere with fresh-rock contact	Recutting, heat, erosion, packing	Flow, pressure, nozzles, returns
High thermal exposure	Material and component response becomes design-specific	Seal, lubricant, bearing, braze, or cutter damage	Temperature estimate and component limits
High confinement	Force and chip formation can differ from ambient tests	Higher load for the same apparent depth of cut	Depth, pressure, stress model, and response
Stick-slip	Intermittent angular speed changes cutting depth	Torsional overload and cutter damage	Surface and downhole RPM plus torque
Whirl or lateral motion	Contacts move outside their intended path	Gauge and shoulder damage	Vibration mode, BHA, and damage location
Bit bounce	Repeated separation interrupts stable cutting	Axial impact and broken elements	Axial vibration, WOB, and lithology

Sandia’s work on hard rock drilling reported that failure of PDC cutters can happen from impact before appreciable wear can be observed. This can be a good forensic warning. A bit can look new, and it may not have been worn significantly, but it can have experienced a dynamic event that damaged the bit.

Bit, BHA, formation and operational records have to be read in conjunction with one another.

A roller-cone mechanism, as found in roller cone bits, may be identified by three rotating cones, but this doesn’t identify the cause of failure.

A tricone bit and PDC drill bits may show damage in different locations across soft and hard formations; a review of PDC bits and tricone bits still has to test evidence rather than accept a bit-family label as the reason for failure.

Read the Returned Bit by Evidence Field, Not Family Ranking

This forensic comparison is done after a bit has been pulled. Each row poses what the returned tricone or PDC bit may reveal and which run record is needed to assign a cause. The columns don’t recommend a product family. They distinguish observable conditions from an explanation that must still prevail through the event timeline.

Returned-bit comparison for failure review, not a winner table
Decision field	Tricone evidence to inspect	PDC evidence to inspect	Evidence still required
Rock-removal marks	Dented, chipped, worn, or lost teeth and inserts by cone position	Wear flats, chipped cutters, delamination, and damage by blade position	Depth-matched lithology, confinement assumptions, cuttings, and drilling response
Moving components	Cone rotation, bearing condition, seals, lubricant evidence, and shirttail wear	No rotating cones; inspect blades, cutter pockets, body, and connection instead	Bit serial, runtime, temperature context, repair history, and BHA condition
Cutting elements	Milled teeth or tungsten carbide inserts, including location and retention	Polycrystalline diamond compact cutters, including exposure, rake, and substrate condition	As-run design record, labeled photographs, scale, orientation, and event window
Impact signature	Broken inserts, cracked teeth, cone damage, and localized loading marks	Chipped or lost cutters, braze or pocket damage, and shoulder concentration	Transitions, fractures, shock, axial/lateral vibration, RPM, and torque by depth
Abrasive signature	Gauge, teeth, shirttail, cone shell, and bearing-area condition	Wear-flat progression, gauge loss, erosion, matrix or steel-body wear	Mineralogy, solids, cuttings, return condition, accepted footage, and comparable photographs
Interval continuity	Check whether damage changes between cones or near abrupt formation transitions	Check whether wear or impact clusters align with continuous or interrupted cutting	Depth-matched markers and event data, not a broad formation label
Cleaning signature	Packed cone areas, erosion, balling, recuttings, and nozzle condition	Blade loading, cutter cooling evidence, junk-slot packing, erosion, and recutting	Fluid properties, flow, pressure, nozzles, losses, solids, and returns
Directional loading	Uneven cone, gauge, or shirttail condition tied to side force and toolface response	Localized shoulder, gauge, blade, or cutter damage tied to lateral motion	Inclination, azimuth, dogleg, steerability record, BHA, and downhole vibration
Trip reason	State whether the bit, bearing system, another BHA component, or the plan ended the run	State whether cutter/body condition, another tool, or a field event ended the run	Daily report, accepted footage, residual condition, handling record, and event chronology
Inference limit	The family name and visible damage do not prove the initiating mechanism	The family name and visible damage do not prove the initiating mechanism	A competing hypothesis, confidence statement, contingency, and next-run discriminating evidence

The 6-Signal Dull-to-Dysfunction Crosswalk

Six evidence groups retain measured, inferred, conflicting and unknown status rather than assigning a root-cause score.

The 6-Signal Dull-to-Dysfunction Crosswalk is a post-run completeness method. It contextualizes interval behavior against drilling response, abrasiveness, and impact exposure, and evaluates cleaning margin and prior bit/BHA behavior against the observed dull condition. It doesn’t determine the cause, but shows which evidence is in conflict, what hypotheses of failure remain, and what should be tested next.

This differentiation is critical. The crosswalk isn’t an IADC method, probability model, or surrogate for responsible engineering. Its purpose is to prevent a team from hiding a missing variable behind a confident root cause claim. Each signal is classified as measured, inferred, conflicting, or unknown. “Unknown” is retained. It doesn’t become favorable evidence.

How should you investigate tricone or PDC damage when offset data are incomplete?

Select a working hypothesis, not a permanent verdict. State the best-supported failure mechanism, and name the unverified mechanism that could defeat it. Provide one alternative explanation. Describe the evidence that would allow you to switch hypotheses. Limit the first comparison to a reasonably comparable interval and avoid changing the bit, BHA, hydraulics, WOB, and RPM all at the same time. Otherwise, the drilling project produces footage, not reusable knowledge. One example of why chatter and impact evidence needs to be tied to the run is the Sandia hard-rock study.

The 6-Signal Dull-to-Dysfunction Crosswalk
Signal / observation	Evidence	Tricone evidence to test	PDC evidence to test	Evidence or stop condition
1A. Interval continuity	Depth-matched lithology and offset response	Check whether abrupt transitions align with damage	Check whether continuous cutting aligns with observed wear	Stop claim if offsets are not comparable
1B. Thermal context	Expected downhole temperature and component limits	Verify bearing, seal, and lubricant envelope	Verify cutter, braze, substrate, body, and cooling	No generic temperature ceiling
1C. Confining-stress context	Depth, pressure, stress model, laboratory boundary	Keep as a force and chip-formation modifier	Keep as a force and MSE modifier	Do not transfer ambient-test values directly
2A. Strength and drilling response	ROP, WOB, RPM, torque, MSE by depth	Check tooth or insert engagement	Check depth-of-cut and efficient response region	Stop a WOB increase when response flattens or dysfunction rises
3A. Abrasiveness	Mineralogy, cuttings, gauge and wear photos	Check teeth, shirttail, gauge, and bearing protection	Check cutter grade, gauge, body, and erosion exposure	Switch review if wear rate threatens accepted footage
4A. Fractures and transitions	Markers, losses, shock, lateral and axial vibration	Check cone and tooth damage at transition depths	Check cutter damage against impact and dynamics records	Stop on repeated impact or localized cutter damage
4B. Torsional dysfunction	Surface/downhole RPM and torque	Review cone contact and BHA interaction	Review stick-slip and depth-of-cut control	Do not blame formation from averages alone
5A. Cleaning margin	Flow, pressure, nozzles, fluid, returns, losses	Check bottom and cone cleaning	Check junk slots, cutter cooling, and recutting	Stop parameter escalation when hydraulics limit response
6A. Prior dull location	Labeled face, shoulder, gauge, cone, bearing photos	Connect tooth/bearing/gauge condition to the run	Connect cutter/body/gauge condition to the run	A code without photos is incomplete
6B. BHA and trip reason	Assembly, drive system, events, why the bit was pulled	Separate bit limit from another tool’s limit	Separate bit limit from another tool’s limit	Do not call a BHA trip a bit failure

IADC Codes and Dull Grades: Evidence, Not Root Cause

IADC classification and dull grades describe design or observed condition; photos and synchronized records are needed to test cause.

A pre-run IADC classification describes a design family, and a post-run dull grade describes a condition. Neither proves a single root cause, guarantees the next run, nor eliminates the need for pictures, synchronized formation, BHA, hydraulics, and operating data. State which grading practice and revision was utilized for the run.

What does IADC dull grading tell you about the next run?

Information shows where trained reviewers located damage on returned bits. The evidence doesn’t necessarily show the root cause of the damage. It can’t, by itself, distinguish among design, formation, WOB, RPM, cleaning, and directional demand. It can’t, by itself, distinguish among an unrelated trip, BHA dysfunction or a dysfunctional bit.

On April 9, 2026, the International Association of Drilling Contractors announced a new Bit and BHA Dull Grading Manual. Its public release joins drilling forensics, bit and BHA grading, failure reporting, visual information, and run-data management. That date should be recorded because a current manual and a legacy code aren’t interchangeable evidence systems.

Forensic reminder: “IADC dull grades are insufficient.”

Paul Pastusek, ExxonMobil Bit and BHA Forensics material hosted by Drilling Contractor. The surrounding material calls for labeled photos, BHA information, daily reports, surface and downhole data, and formation context.

Observed record	It reports	It does not prove	Check next
Pre-run classification	A described design category	Performance in the next section	Detailed design and application basis
Inner cutting-structure wear	Condition and location	Abrasion as the only cause	Lithology, heat, loading, and images
Outer/gauge wear	Loss or damage near outer structure	A single directional or abrasive cause	Gauge measurements, side force, hole condition
Chipped or broken cutter/insert	Localized element damage	Whether shock, overload, flaw, or handling caused it	Damage map, vibration, transitions, handling record
Bearing failure	A failed or degraded bearing condition	Whether seal, heat, load, fluid, or runtime initiated it	Seal, lubricant, temperature, time, and load
Erosion	Material loss pattern	The responsible fluid path or solids mechanism	Nozzles, fluid, solids, pressure, and location
Lost component	A missing part or portion	Where it is or why retention failed	Recovery exposure, retention, debris, and event time
Pulled for a non-bit reason	The trip reason was not the bit	The bit had reached its life limit	BHA event, field decision, residual condition
Unlabeled photo	Only a visual appearance	Location, orientation, timing, or progression	Bit ID, face position, scale, angle, and depth context

If a broken element may have remained downhole, the post-run team should document the exposure and route the recovery issue under the approved plan. The relevant commercial equipment is fishing and milling tools; this manual won’t describe a recovery operation.

Map Construction Clues Before Naming a Failure Cause

Construction details should be explained because they show the location of the evidence and not because they select a new bit. Each observation should include a labeled damage map and design revision, and serial number. The intended effect column describes the design function and doesn’t speculate that it created the field result.

Construction fields for a returned-bit evidence map
Construction field	Intended effect	Evidence to request	What can reverse the benefit
Cutting-structure identity	Establish the exact teeth, inserts, or cutter layout that entered the hole	Serial, revision, face map, element count, locations, and labeled photographs	Wrong revision, repair substitution, missing identity, or unlabeled damage
Cone, bearing, and seal system	Support roller-cone motion while retaining lubricant and excluding debris as designed	Cone freedom, bearing debris, seal condition, lubricant evidence, hours, and temperature	Heat, overload, contamination, loss of seal integrity, or unrelated handling damage
Body material and blade or cone support	Carry drilling loads and retain cutting elements in the as-built geometry	Steel or matrix record, erosion map, cracks, pockets, cone shell, and repair history	Impact, erosion, fatigue, manufacturing variance, or an unrecorded repair
Gauge and shoulder	Maintain hole size and manage outer-radius contact under the approved design	Before/after gauge measurements, wear location, side-force history, and hole condition	Whirl, abrasiveness, undergauge running, directional loading, or poor stabilization
Nozzles and flow passages	Deliver the hydraulic layout recorded for bottom cleaning and component cooling	Installed sizes, total flow area, orientation, plugging, erosion, pressure, and flow	Solids, losses, recirculation, damaged nozzles, or a configuration different from the record
Cutter, insert, braze, or retention interface	Transfer load while retaining the cutting element in its intended position	Fracture surface, pocket condition, missing material, neighboring damage, and event time	Shock, overload, heat, flaw, debris impact, or post-run handling
Thermal path	Keep seals, lubricant, cutters, braze, substrate, and body within controlled limits	Temperature estimate, cooling record, discoloration, material evidence, and exposure time	Poor cleaning, frictional heat, stalled motion, high ambient temperature, or model error
Erosion protection	Protect exposed body, nozzle, blade, shirttail, and gauge locations from the planned fluid path	Material map, erosion location, solids loading, fluid properties, and nozzle condition	A changed flow path, abrasive solids, cavitation, recutting, or damaged hardfacing
Connection and make-up record	Transfer torque and axial load through the documented interface	Connection identity, make-up record, shoulder condition, cracks, and handling chronology	Incorrect make-up, galling, misalignment, overload, or surface handling damage
Repair and reuse status	Preserve traceability of changes that could affect the returned condition	Prior inspection, repair scope, replaced parts, release record, and previous dull history	Incomplete traceability, mixed components, undocumented rework, or non-comparable prior service

Scope Controls for Transferring Evidence Between Applications

Application and feature labels may describe a run, but none, by itself, should be considered the root cause. Maintain the as-run state, including subsurface geological conditions, when a lesson learned is transferred between drilling applications, bit families, formations, or industries.

Use the 7-Channel Operating Record for Time-Aligned Forensics

Seven operating channels need depth and time alignment; isolated averages cannot establish a drill-bit failure cause.

An operating record for the driller aligns seven channels by depth and time: WOB, RPM, flow and pressure, nozzle configuration, torque, vibration and drilling response. Limits come from the bit, BHA, drive system, hydraulics, formation and approved plan. An isolated average doesn’t explain why the response changed.

Channel	Unit and source	Context retained	Response question	Limit owner
1. Weight on bit	lbf or kN; surface and modeled/downhole	Depth, transfer loss, bit size	Did added load create useful cutting?	Bit/BHA/drive approved envelope
2. Rotary speed	rpm; surface and downhole	Motor/RSS contribution, stick-slip	Was cutter speed stable?	Bit, motor, rotary system
3. Flow and pressure	gpm or L/s; psi or MPa	Mud, depth, losses, solids	Was cleaning margin maintained?	Hydraulic program and equipment limits
4. Nozzle configuration	Count, size, total flow area	Installed serial and change history	Did the pressure response match the plan?	Approved bit and hydraulic design
5. Torque	lbf·ft or kN·m; surface/downhole	Depth, RPM, lithology, filtering	Did cutting load or torsional dysfunction change?	Rig, BHA, connection, and bit limits
6. Vibration	Mode-specific sensor record	Location, sample rate, time alignment	Was impact, whirl, bounce, or stick-slip present?	Tool and operating procedure
7. Drilling response	ROP, MSE, cuttings, returns	Accepted footage and formation markers	Did the change improve useful work without damage?	Drilling program and decision owner

An approved change to a single input is made in defined steps. During the change, other inputs are observed. The outcome is noted and can be a positive or negative response. A rise in surface ROP is not enough if downhole vibration rises, torque becomes unstable, or pressure behavior changes. Cuttings can also indicate recirculation. Directional drilling adds toolface response and steerability to the review. Stop signals and final limits belong in the drilling operations program.

There are other factors beyond the bit that can shape the forensic record. The motor, rotary steerable systems, drill collars, jars, subs and measurement while drilling (MWD) tools can all impact the forensic record. The entire configuration of downhole drilling tools in the recorded assembly should be evaluated to understand how bit damage can be attributed to BHA interaction and how it influences the overall well trajectory; surface trip and handling records should also be evaluated prior to determining downhole damage.

Pipe handling tools should also be considered when evaluating the surface trip and handling chronology.

Close the Loop from Dull Condition to the Next Bit Run

A next-run trial changes one controlled variable and preserves competing hypotheses; cost per foot alone cannot prove cause.

This review aid links eight record groups for a next-run decision: bit identity, bit interval and formation; planned vs. actual operations; hydraulics, BHA and drive system; time-aligned dysfunctions; dull photos and grading; accepted footage with trip reason. Change one controlled variable to produce reusable evidence in the next run, if feasible.

A dull photo doesn’t end an investigation. The ExxonMobil forensics material connects surface drilling data and bit images to possible dysfunction such as stick-slip, whirl, bit bounce, and overload in heterogeneous formations. The analyst still needs time and depth alignment of the recorded drilling conditions. A damage mark without the associated event window is weak evidence.

Lock identity: record bit serial number, size, connection, family, design revision, repair status, nozzles and installed configuration.
Define the interval: mark tops and bottoms, lithology, fracture, loss zones, temperatures and in-situ assumptions.
Preserve the plan – retain the approved WOB, RPM, hydraulic, directional and stop-condition plans.
Align actual channels – time and depth synchronize surface and downhole records; maintain sample rate and positions of sensors.
Map dull condition, photograph face, shoulder, gauges, cutting elements, cones, bearings and other pertinent body parts, indicating scale, label and orientation.
Separate observation from inference – define each inference that explains the observation and the evidence that might help resolve the inference.
Explain the trip – state why assembly was pulled; state why run ended (because of bit, other BHA component, plan, field event).
Approve one learning change – specify the changed variable, the predicted response, the owner and the evidence to be collected; define the state of affairs that will cause the change to end.

In conjunction, the seven-channel operating record and eight-stage next-run loop provide means to connect operating data with dull condition, and to do so without invoking first-party field performance data. The numbered sequence is a review aid, not a claim that every failure path will have eight causes, or that the method provides a measured prediction rate.

Following a series of bad runs, several teams consider changing almost everything. While it’s tempting to want to change everything, keep in mind that changing everything makes it impossible to know the cause of an improvement, or gives no attribution. Let’s say a team changes their bit from tricone to PDC, changes motor bend, increases flow, changes nozzle area, increases WOB, and increases rotary speed. If the run improves, no one is able to say which adjustment made the run better. If the run is still poor, no one is able to say which adjustment caused the issue. At least the adjustment should be clear to everyone.

A supplier-authored field case by Alexis Garcia of National Oilwell Varco in Drilling Contractor records footage, average rate, lithology, bit design, and two BHA-related trips. The lesson isn’t the reported performance number. The lesson is that trip reason belongs with footage; otherwise, another tool’s limit can be assigned to the bit design.

Why Cost per Foot Cannot Prove a Failure Cause

All values below are deliberately hypothetical. This isn’t a current estimate, a China Welong field-performance claim, or a recommendation for a particular bit.

Assumption and source ledger for the hypothetical sensitivity check
Input	Hypothetical value	Replace with	Sensitivity
PDC bit cost	$45,000	Comparable approved quote	Changes the numerator but does not identify a physical cause
Rig time rate	$1,500/h	Project time-dependent rate	Magnifies time difference and trip exposure
PDC success footage	3,600 ft in 60 hours	Comparable accepted footage	Strong denominator effect; retain interval comparability
PDC rotating time	60 hours	Time-aligned field record	Affected by response, dysfunction, and non-bit limits
Normal trip time	20 hours	Well-plan estimate	Applies once per scenario; record the actual trip reason
Premature-event footage	900 ft after 24 hours	Failure-mode event tree	Dominant denominator risk and a trigger for forensic review
Premature-event consequence	$25,000	Non-time event cost only	Must not duplicate trip hours or invent a cause

While a cost result can signal where a post-run analysis should be directed, it can’t distinguish between wear, impact, and/or cleaning loss, as well as malfunction of other BHA components or a trip caused by another component. Keep the cost scenario downstream of the dull review. If the likelihood of an event occurring, or the potential consequence of the event lacks comparable evidence, mark the situation as judgment and don’t create a product family recommendation.

The 7-Record Post-Run Evidence Dossier

The seven-record dossier ties formation, bit, BHA, hydraulics, direction, offsets and dull evidence to their confidence limits.

The section and formation, bits and interfaces, BHA and drive, hydraulics and drilling fluids, directional plan, offset performance, and dull/failure data are included in the 7-Record Post-Run Evidence Dossier. Each piece of data is identified as measured, estimated, conflicting or unknown. Reviewers can use these inputs to formulate competing failure hypotheses.

The 7-Record Post-Run Evidence Dossier
Record	Minimum contents	Status field	Decision consequence if missing
1. Section and formation	Hole size, depth, interval, lithology, continuity, abrasiveness, fractures, temperature and stress context	Measured / inferred / unknown	Cutting structure and risk premise differ
2. Bit and interface	Size, connection, gauge need, nozzles, prior design, repair status, required records	Controlled / provisional / unknown	Damage cannot be tied to the exact as-run configuration
3. BHA and drive	Motor/RSS/rotary, bend, stabilizers, collars, jars, tools, limits and dynamics history	As-run / planned / unknown	Steerability and loading assumptions change
4. Hydraulics and fluid	Mud properties, flow, pressure, nozzle area, solids, losses, cuttings and temperature	Measured / modeled / unknown	Cleaning and erosion exposure cannot be compared
5. Directional plan	Inclination, azimuth, build/turn need, dogleg target, toolface response and hole-quality need	Approved / draft / unknown	Directional loading cannot be separated from bit interaction
6. Offset performance	Comparable depth, design, WOB, RPM, flow, ROP, footage, hours, trip reason and cost basis	Comparable / partial / not comparable	The comparison may mix unlike intervals or trip reasons
7. Dull and failure evidence	Grade revision, labeled photos, damage map, event window, vibration, BHA condition and competing causes	Complete / partial / absent	The next design may repeat an unidentified failure route

An estimated temperature provides some evidence if the uncertainty and source are captured. A copied offset ROP is weak evidence if depth, lithology, BHA, and trip reason are missing. Reviewers should state which assumptions materially affect a failure hypothesis and the next controlled change.

Once the dossier is complete, use the existing Drill Bits (Tricone & PDC) solution page for available product design options, customization, supply scope, lead time, and quotation. China Welong states that it was founded in 2001 and operates as an international integrated supply-chain service provider; its background remains on the About Us page, commercial inquiries remain on the solution or contact page, and this guide stops at post-run evidence instead of duplicating the commercial selection brief.

Frequently Asked Questions

What can an IADC dull grade prove?: It records observed condition and location under a stated grading practice. It does not prove a single root cause without photographs and synchronized formation, BHA, hydraulic, and operating evidence.
Can a PDC cutter fail before obvious wear appears?: Yes. Sandia reported impact-related PDC cutter failure before appreciable wear was visible, so a new-looking surface does not exclude a damaging dynamic event.
Why must records be aligned by depth and time?: Alignment lets reviewers test whether vibration, torque, pressure, lithology, and damage location belong to the same event window rather than to unrelated parts of the run.
What should change on the next controlled run?: Where practical, change one owned variable, state the predicted response, retain a contingency, and define the evidence and stop condition before the run.
Does an ISO 9001:2015 or API 7-1 statement explain a drill-bit failure?: No. Verify the exact legal entity, site, current scope, design-family controls, offered-item evidence, and order record; none of those alone proves the field cause or outcome.

Turn the Dull Review into a One-Page Next-Run Record

A next-run record connects as-run context, observed damage, uncertainty and one controlled trial with explicit stop conditions.

To choose the right next controlled trial, write a one-page review record before asking for a new winner. Cite the interval, as-run bit identity, observed damage, evidence confidence, BHA, seven operating channels, competing failure hypotheses, contingency, and stop conditions. Attach the seven-record post-run dossier and retain the surface-data and dull-image evidence used to test failure hypotheses. Then state where each conclusion depends on an assumption rather than a measured input.

There are many factors that may be unknown. For example, factors such as temperature or vibration may be uncertain. There may be unknown offset comparability. There may be uncertainty about the dull condition. These uncertainties should be considered in the decision.
A universal operating table shouldn’t be copied. The approved limit owner is the bit/BHA/hydraulic system and drilling program.
Don’t change six variables and call the next run a test. Retain attribution if operations allow.

This may result in a controlled tricone trial, a PDC trial or a hybrid of the two. The main thing is each change should test a documented failure hypothesis and be attributed for the next dull round review.