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Improving Drilling Performance By Applying Advanced Dynamics Models Mark W. Dykstra, Ph.D. Shell Exploration and Production Society of Petroleum Engineers Distinguished Lecturer Program www.spe.org/dl
The Message Drilling system vibration affects drilling efficiency Uncontrolled vibrations can lead to poor hole quality Image logs difficult to interpret Completions difficult to run Formation damage Advanced dynamics models are helping us understand and mitigate vibrations Reference: Santos, et al. Consequences and Relevance of Drillstring Vibration on Wellbore Stability, SPE/IADC 52820
Reference: ASME Journal Considering Engineering Simulation?
Types of Dynamics Models Engineering Models Research Models Everyday use BHA design Linear Finite Element Analysis Beam elements Simplified contact geometry Idealized vibration inputs Estimates for planning and post-analysis Buckling load Static and dynamic loads and stresses Natural frequencies and mode shapes (critical speeds) More detailed analyses Bit designs (PDC, RC) BHA design Bit/BHA system performance Nonlinear FEA Beam elements Complex contact geometry Complex vibration inputs Refined load and stress estimates Transient dynamic loads and stresses Post-buckling analyses Improved computational horsepower has made use of research models more practical
Research Model Applications PDC Bit Dynamic Stability Evaluated via laboratory testing Constant speed (often 120 RPM) Increment weight on bit (ROP) Identify transition from unstable to stable Time consuming and costly Needed a predictive model Unstable 8.500-in. M434 Stable 8.750-in. M123
Bit Dynamics Model Stability Prediction Dynamic Load Evaluation 120 RPM, 3 ft/hr Force vectors shown in yellow and green Unstable 8.500-in. M434 Reference: Hanson, Hansen Dynamics Modeling of PDC Bits, SPE/IADC 29401
If PDC Cutters Could Talk
Verification of Stability Predictions Laboratory Tests 12 27 designs, 5.875 to 17.500-in., various IADC classes Measured Stable ROP Step 10 8 6 4 2 7.875-in. M434 3 ft/hr, 120 RPM 0 0 2 4 6 8 10 12 Predicted Stable ROP Step
Improving PDC Bit Stability Laboratory Tests Hard limestone (c o =15 kpsi), 120 RPM 90% Probability of Stability (%) 80% 70% 60% 50% 40% 30% 20% 10% 0% Latest Generation (>25 bits) Previous Generation (>50 bits) 0 3 6 9 12 18 24 36 48 Rate of Penetration (ft/hr)
50,000 45,000 Dynamic Load Predictions Cutter Power vs. Cutter Damage 7.875-in. M123 Diamond Table Loss 100% 90% Power (BTU/hr) 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 Avg. Dynamic Power Smooth Rotation Power Max. Dynamic Power 80% 70% 60% 50% 40% 30% 20% 10% Diamond Table Loss 0 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0% Bit Center Cutter Scaled Radial Position Bit Gauge
Load Predictions Through Beds Formation changes affect load distribution Soft Hard (nose) Soft Hard Soft Hard Soft Hard Segmented core used for laboratory tests Hard Soft (cone, shoulder)
Research Model Applications... Roller Cone Bit Design Elimination of off-center running tendencies Cone Wear Uneven Gauge Wear
Research Model Applications... BHA Dynamic Stability Unbalanced components feed whirl Mass imbalance in collars Eccentric rotor rotation Eccentric rotor rotation Frictional interaction with wellbore triggers BHA whirl High average accelerations Extreme impacts Needed a predictive model Whirl caused by mass imbalance
Drillstring Dynamics Model 8.500-in. Horizontal Hole Instrumented motor MWD tool LWD tool Operating Conditions WOB = 22.4 klb TOB = 4.6 klb-ft ρ M = 11.7 ppg 88 ft 490 ft Reference: Heisig, Neubert Lateral Drillstring Vibrations In Extended-Reach Wells, IADC/SPE 59235
Laboratory Verification Reference: Aldred, W.D. and Sheppard, M.C Drillstring Vibrations: A New Generation Mechanism and Control Strategies, SPE 24582
Downhole Bending (lb-ft) Simulated Bending (lb-ft) Verification of Bending Predictions Controlled Field Tests 3000 1500 0-1500 12.250-in. hole, RC-STB-MWD-STB-DC Limestone drilling -3000 330 332 334 336 338 340 3000 1500 0-1500 -3000 50 52 54 56 58 60 Time (s)
Research Model Applications... Bit-Drillstring System Performance Effect of BHA vibration on bit loading
Research Model Applications... Bit-Drillstring System Performance The effect of BHA vibration on bit loading Operating parameters for sub-optimal BHAs 2,500 2,000 Cutter Force Distribution 7.875-in. IADC 627 45 RPM, Lab Rig 45 RPM, Slick BHA 90 RPM, Slick BHA Average Force (lb) 1,500 1,000 500 0
Financial Impact: Improved Bits UK North Sea Application Hard and abrasive zones Poor PDC life in offsets Needed to improve in 12.250-in. section Fm. Tops Lithology Series 9443 Tor 10667 Flounder 12133 Herring 12629 Plenus/Hidra 12902 Cromer Knoll 408 609 13262 Kimmeridge 13591 Brae 1 13755 Brae 2&3
12.250-in. Section Performance Focus Well New designs drilled further and faster Bit Type Depth Out (ft) Drilled (ft) Hr. Avg. ROP (ft/hr) Cost/ft (US$/ft) Standard 1.1 13,535 49 11.7 4.1 2,274 New 609 13,930 395 30.1 13.2 467 New 408 14,437 507 42.2 12.0 476 New 608 14,820 383 38.3 10.0 686 Standard 1.2 15,013 193 32.1 6.0 897 Standard 2.1 15,128 115 14.3 8.0 1,049 Versus Offset Section drilled in half the time Savings US $663 per foot US $816,282 for section 400 300 200 100 0 Drilling Hours HP2 HP1
Financial Impact: BHA Refinement Norwegian North Sea Application 6,000-10,000 ft horizontals in reservoir Geosteering to stay above O/W contact Soft sands, some calcite cemented zones Could not steer PDC bits on motors RS systems potentially offered step change Early Challenges Bit performance RS system durability Multidisciplinary Focused Study Advanced models used for both bit and RS system refinement Premature Fatigue Cracks Reference: Fiksdal, Rayton, Djerfi Application of Rotary Steerable System/PDC Bits, SPE/IADC 29401
9.500-in. Hole Section Performance Description Before Study After Study Average interval length 8,856 ft 8,856 ft Calcite stringers 7% 7% Number of runs 8.5 5 Run length 1,273 ft 2,102 ft Bit runs 10.4 (6.7 RC, 3.7 PDC) 4.6 (0.9 RC, 3.7 PDC) ROP 35.1 ft/hr 67.2 ft/hr BHA component failures 3.5 1.9 Failure Distribution < 25 circulating hours 25% 14% 25-75 hr 18% 14% > 75 hr 57% 72% Improved Drilling Efficiency Improved bit performance Improved RS BHAs Savings approach US$1MM per well based on drilling time
Summary Advanced dynamics models are useful for planning Bit design optimization BHA design optimization Advanced dynamics models are useful while drilling Lessons learned provide insights into improved operating parameters Advanced dynamics models are useful for post-analysis Evaluation of downhole vibration measurements Failure analysis of drilling system components Advanced dynamics models improve performance PDC bit efficiency and durability RC bit efficiency and durability LWD tool durability Hole quality
The Next Challenge Potential Performance Rate of Penetration (Or Torque) Region II: Efficient Drilling Performance is enhanced by redesigning to extend the founder point Region III: Founder Bit Balling Bottom Hole Balling Vibrations Region I: Inadequate Depth of Cut Weight On Bit Reference: Dupriest and Koederitz Maximizing Drill Rates with Real-Time Surveillance of Mechanical Specific Energy, SPE/IADC 92194
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