Drill Bit Selection
Objectives
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Bit Selection Processes
Which Bit to Choose?
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Roller Cone or Fixed Cutter? If Roller Cone:
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Steel teeth or tungsten carbide inserts? Projection and Pitch of teeth / inserts? Journal bearing or roller bearings? PDC or natural diamonds? Cutter size & shape? Number of blades, hydraulics, bit profile?
If Fixed Cutter:
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Bit Selection Process Overview
Bit selection is at the heart of a process that begins and ends with the customer
CUSTOMER
Well Program
Summary Bit of Predicted Recommendations Well Data Performance Operating Parameters Hydraulics Economics Calculation Pricing
Offset Product Information Information
Drilling Fluids Influence
Mud Type Mud Weight
Request
BIT SELECTION Geology Influence
Rock Type Strength Stickiness Abrasiveness
Directional Drilling Influence
Build & Walk rate reqd. Tangent angle Drive type
Gather Data:
Well Prognosis Mud Program Directional Plan Offset Bit Records Offset FRR s Mud Logs Electric Logs
Prior Drilling History
Bit types used Performance standards Types of vibration
Parameters Recommendation
Analyze Data
Selection Process
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Applications
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geological knowledge is essential enhanced selection process using offset bit records, well log Analysis / GeoMechanics bit selection should meet actual criteria necessary to fail specific rock types and satisfy the cleaning requirements
Bit Selection Process - Details
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Collect data
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geology offset bit records, mud logs, well logs length of hole sections, drill out casing? drilling fluids directional drilling objectives geology
Analyze the proposed well plan
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Bit Selection Process (continued)
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Consider the rocks properties
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hardness / drillability / compressive strength abrasiveness stickiness
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Determine the Engineering Classification for the rock Identify best candidates from the Roller Cone Bit Selection Table and offsets
Bit Selection Process (continued)
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Identify opportunity for fixed cutter bit
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use Fixed Cutter Selection Table PDC, TSP or diamond? cost per foot breakeven analysis
Make an economic forecast
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Select the bit Check and fine-tune answer
Estimating Compressive Strength of the Rock
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Provide offset logs to Security DBS
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sonic log, density log, porosity log gamma mud log
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Security DBS performs GeoMechanics analysis Results in a computed strength log Strength values matched to bits
Engineering Classification for Intact Rock
Classification Very Low Strength Low Strength Medium Strength High Strength Very High Strength Compressive Strength, psi < 4000 4000 - 8000 8000 - 16000 16000 - 32000 > 32000 ROP ft/hr > 70 35 -70 15 - 35 5 -15 <5
Engineering Classification for Intact Rock
Classification Very Low Strength Low Strength Medium Strength High Strength Very High Strength Compressive Strength, MPa < 27.6 27.6 - 55.2 55.2 - 110.4 110.4 - 220.8 >220.8 ROP m/h > 21.3 10.7 - 21.3 4.6 - 10.7 1.5 - 4.6 < 1.5
Roller Bit Selection Table
IADC CODES
Classification Very Low Strength Low Strength Medium Strength High Strength Very High Strength
Milled Tooth codes 1xx 1xx - 2xx 2xx - 3xx 3xx n/a
TCI codes N/A 4xx - 5xx 5xx - 6xx 6xx - 7xx 8xx
Identify Opportunities for PDC Drill Bits
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Potential PDC Applications
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long shale, mudstone or claystone sections chalk, limestone, salts and anhydrite gumbo shales with oil based mud researched sandstone intervals absence of hard, well cemented, angular abrasive sands absence of chert, pyrite, quartzite motor/turbine drilling (high RPM)
Identify Opportunities for Natural Diamond / Impregnated Drill Bits
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hard siltstones, sandstones hard limestone, dolomite, motor or turbine drilling (high RPM) roller bit ROP < 6 ft/hour (1.8 m/h) roller bit footage < 50 ft (15 m) per run
Economics of Bit Applications
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Cost of the drill bit is not the concern ! Performance is more important
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projected ROP projected footage includes raw bit cost daily operations cost dominates trip time must be considered
Relevant cost parameter is Cost per Foot
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Cost per Foot (CPF)
CPF = bit cost + rig rate (trip time + rotating time) footage drilled CPF = (C + R ( t + T )) / F Where: bit cost, C, is in dollars rig rate, R, is in dollars per hour trip time, t, and rotating time, T, are in hours footage drilled, F, is measured in feet
Cost per Meter (CPM)
bit cost + rig rate (trip time + rotating time) CPM = length drilled
C + R(t+T) CPM = L Where: C R t T L bit cost, Rubels rig rate, Rubels/hour trip time, hour rotating time, hour meters drilled, meter
Rub/m
Bit Selection Process - Summary
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Collect all necessary offset data Perform GeoMechanics Analysis Identify bit types for all intervals to be drilled Identify any PDC bit applications Make an economic forecast
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cost per foot breakeven analysis
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Select the bits Build bit program, operating parameters, hydraulics
Thank you
