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Similaire à 2007 drilling drlg sym - optimizing bit performance
Similaire à 2007 drilling drlg sym - optimizing bit performance (10)
2007 drilling drlg sym - optimizing bit performance
- 1. Drilling Optimization with Mechanical Specific Energy SPE Drilling Studies Group Christine Guerrero, Drilling Engineer Drilling Solutions Team April 5, 2007 © Chevron 2005 DOC ID
- 2. Global MSE Opportunity Reduce “Invisible Lost Time” component of drilling costs, by: Maintaining optimal drilling parameters for the life of the bit Increasing ROP to the system maximum regardless of bit type Knowing when to replace a bit when performance is suboptimal © Chevron 2005 DOC ID
- 3. Mechanical Specific Energy Specific Energy Principle relates the Amount of Energy Required to Destroy a Unit Volume of Rock with the Destruction Efficiency of the Bit. Teale’s eqns for SE in rotary drilling at atmospheric conditions (‘65): Es = WOB + 120 * π * N * T AB AB * ROP T µ = 36 DB * WOB Es min EFFM = Es Es min = CCS Pessier validated these eqns for drilling under pressure (SPE 24584 ‘92) © Chevron 2005 DOC ID
- 4. Mechanical Specific Energy Equation SPE 92194, 2005 MSE = 0.35 * (WOB + 120 * π * RPM * T ) AB AB * ROP Where: MSE = Energy Input, psi WOB = WOB (lbs) AB = Bit Area, sq. inches RPM = Rotary Speed T = Torque, ft-lbs ROP = Rate of Penetration, ft/hr Factor = 0.35 (Efficiency factor) © Chevron 2005 DOC ID
- 5. Trending Approach SPE 92194, 2005 At perfect drilling efficiency, the MSE equals rock compressive strength. However, bits are typically only 30-40% efficient even at peak performance. That is where the Efficiency Factor comes into place (35%). Operators commonly set the Efficiency uniformly to 0.35 regardless of bit type or WOB. Though the value may not be as accurate as possible, the uniformity of the shift allows the curve to still be used effectively as a visual trending tool. MSE typically uses surface drilling data only to calculate specific energy. Surface torque, WOB, and change in lithology could lead to wrong assessments in particular when drilling directional wells as surface torque and WOB do not take into account the friction losses between borehole and drillstring. © Chevron 2005 DOC ID
- 6. Digital Data Requirements Readily Deployed Thru Existing Driller’s Console, Mudlogger, MWD/LWD Systems REQUIRED Depth ROP Total RPM WOB (kips) Mud Weight (ppg) Torque (amps or ft-lbs) RECOMMENDED Downhole Vibration Measurements Expected Rock Strength (UCS & CCS) Log Real-time GR for Correlation © Chevron 2005 DOC ID
- 7. Real-Time Data Display (Driller’s Console, Mudlogger, MWD/LWD) © Chevron 2005 DOC ID
- 8. What is a Drill Off Test? A drill off test is simply a step by step process of altering drilling parameters to maximize penetration rate and determine “Founder Point” • “Founder Point” defined as point at which ROP stops responding linearly with increasing WOB and RPM. Due to sensitivity of PDC bits to formation changes and the effects of wear, these tests must be performed periodically as the bits performance dictates. 2 methods of Drill Off Tests: • Active and • Passive © Chevron 2005 DOC ID
- 9. Active DOT 1. Select Minimum recommended WOB and moderate RPM’s. 2. Maintain initially selected WOB by replacing it as drilling occurs and record average ROP. 3. Increase WOB in increments of 2000 lbs, continuing to record average ROP. 4. Continue until ROP no longer increases as incremental amounts of WOB are applied or ROP exceeds cleaning capacity. 5. Repeat steps 1-4 using RPM’s that are incrementally increased and decreased from initial RPM’s. 6. Plot data WOB vs. ROP and select the weight and rpm combination which provide the highest ROP. This will correspond to the highest feed rate (ROP/RPM) for the selected rotary speed. Best suited for fast drilling conditions. © Chevron 2005 DOC ID
- 10. Passive DOT 1. Select the WOB to start the test that is 80% of maximum bit weight range, as specified by vendor. 2. Select a moderate rotary speed that is above the minimum recommended. 3. Lock the break down and record the time elapsed to drill off 2000 increments. Do not add any weight to the bit during the test. Allow the bit to drill until no further drill off can be noticed. 4. Incrementally increase and decrease rotary speed from initially selected rotary speed and repeat steps 1-3. 5. Compare the data and select the weight increment and rotary speed requiring the least amount of time to drill off. Best suited for slower drilling conditions. © Chevron 2005 DOC ID
- 11. DOT Example WOB and RPM test are conducted by observing MSE while increasing parameters. If the MSE remains close to the baseline value while raising WOB, the bit is as efficient at the high load as before. ROP will continue to increase linearly with WOB. RPM test are conducted in a similar manner (SPE 92194). © Chevron 2005 DOC ID
- 12. Determine Founder Point : Establish Baseline DOT data showing non-linear response below the minimum depth of cut and above the founder point (SPE 92194). © Chevron 2005 DOC ID
- 13. Causes of Founder - Inefficiency Dull / Damaged Bit Vibration Inadequate Hole Cleaning Bit Balling Bottom Hole Balling Rig / BHA Limits © Chevron 2005 DOC ID
- 14. General Guidelines for Drill-Off Tests in Soft Formations with PDC Bits Responds well to increases in rotary speed since they fail in shear. The absence of formations that require sufficiently high WOB to produce accelerated thermal wear allows drilling at relatively high RPM’s >150. Cutter wear resulting from elevated rotary speeds will be low in soft non-abrasive formations. Combination of relatively low WOB and higher RPM’s generally will yield the best performance. © Chevron 2005 DOC ID
- 15. General Guidelines for DOTs in Medium to Medium-Hard Formations w/ PDC Bits Fail by a combination of shearing, chipping, and plowing. These formations respond better to higher WOB rather than higher RPM’s. Cutter wear will increase and bit life decrease to the generation of heat as harder more abrasive formations are drilled. Only moderate increases in penetration rate are usually achieved by increasing rotary speed. Bit weight should always be increased over rotary speed until the upper limit of the recommended weight range is obtained. For PDC & TSP bits, higher WOB and moderated RPM’s should be utilized. © Chevron 2005 DOC ID
- 16. General Guidelines for Drill-Off Tests w/ TSP bits TSP bits will generally be drilling harder formation requiring higher WOB to effectively drill, perhaps as much as is normally applied to rock bits. Moderate to high WOB in conjunction with moderate rotary speeds yield the best results. Feed rate (ROP/RPM) should be maximized while attempting to maintain ROP. © Chevron 2005 DOC ID
- 17. Drill Off Test Findings The drilling parameters that the DOT yields can be expected to produce the optimum drilling rate only through the formation in which the test was taken. Most formation changes will require bit weight and rotary speed changes to maintain optimum conditions. When formation changes, a new DOT is required. Additional DOTs are recommended every 5-6 hours to validate/confirm optimal parameter selection. © Chevron 2005 DOC ID
- 18. Real-Time MSE Procedure 1. Verify current formation type via downhole Gamma reading. 2. Drill-Off Test to determine optimum WOB & RPM 3. Calculate MSE. (The amount of mechanical energy input at the rig floor per unit volume of material removed). 4. Establish “new bit” MSE trend as bit drills ahead Observed while bit is sharp and adequate hole cleaning is achieved. 5. Monitor and compare the RT MSE to the “new bit” MSE. Increase in MSE could indicate a drilling inefficiency! Estimate the wear by comparing the current w/ the “new bit” MSE © Chevron 2005 DOC ID
- 19. Relative Performance vs. Dull Grade Qualitative description of formation and drilling tool dependencies (SPE 74520). © Chevron 2005 DOC ID
- 20. RT MSE Log Display DH Vibration and Balling Inefficiency… © Chevron 2005 DOC ID
- 21. InterAct RT MSE Log Display DH Vibration Impacting Drilling Efficiency… © Chevron 2005 DOC ID
- 22. Know when to pull the bit… UK Sector North Sea - 7 Bladed PDC © Chevron 2005 DOC ID
- 23. Know when to pull the bit… Offshore Angola - 6 Bladed PDC © Chevron 2005 DOC ID
- 24. Parameter Selection… © Chevron 2005 DOC ID
- 25. Parameter Selection… © Chevron 2005 DOC ID
- 26. DW West Africa : DOT Impact © Chevron 2005 DOC ID
- 27. DW West Africa : DOT Impact © Chevron 2005 DOC ID
- 28. Deepwater Brazil : Exploration © Chevron 2005 DOC ID
- 29. Deepwater Brazil : WOB Transfer © Chevron 2005 DOC ID
- 30. Deepwater Brazil : Deep Exploration © Chevron 2005 DOC ID
- 31. Deepwater GOM : Vibration © Chevron 2005 DOC ID
- 32. Recommended Reading Teale, R.: “The Concept of Specific Energy in Rock Drilling,” Int. J. Rock Mech. Mining Sci. (1965) 2, 57-53. Waughman, R., Kenner, J., Moore, R.: “Real-Time Specific Energy Monitoring Reveals Drilling Inefficiency and Enhances the Understanding of When to Pull Worn PDC Bits,” paper SPE 74520 presented at 2002 SPE Drilling Conference, Dallas, Texas, 26-28 February 2002. Dupriest, F. and Koederitz, W.: “Maximizing Drill Rates with Real- Time Surveillance of Mechanical Specific Energy,” paper SPE 92194 presented at 2005 SPE Drilling Conference, Amsterdam, The Netherlands, 23-25 February 2005. Caicedo, H., Calhoun, W., Ewy, R.: “Unique ROP Predictor Using Bit- specific Coefficient of Sliding Friction and Mechanical Efficiency as a Function of Confined Compressive Strength Impacts Drilling Performance,” paper SPE 92576 presented at 2005 SPE Drilling Conference, Amsterdam, The Netherlands, 23-25 February 2005. © Chevron 2005 DOC ID
Notes de l'éditeur
- We talk a lot about None Productive Time, but the opportunities for efficiency improvement in drilling & tripping are substantial.
- Es theory is not new; it has been used for quick bit performance assessment for years. Equations 1, 2, and 3 are Tale’s specific energy equations for drilling under atmospheric conditions. Equations 1. We denote specific energy by Es. Teale’s equation for the amount energy, in units of psi, input into a drill bit is defined by the following equation. 2: Teale defined a coefficient of sliding friction µ to express torque as a function of WOB, which is used to compute Es in the absence of reliable torque measurements. If you know μ and WOB, you can use this relationship to calculate bit torque. Equation 3. Teale further defined the mechanical efficiency of rock destruction. He defined the minimum energy input as equal to the rock strength, and therefore the mechanical efficiency, EFFm, is equal to Es min (or rock strength) divided by Es (the actual energy input). More recently, Pessier validated the specific energy theory for drilling under confined pressure conditions, where the apparent strength of the rock to the bit, Es min, is CCS rather than UCS.
- So, let’s talk about what ExxonMobil has done…. At perfect drilling efficiency, the MSE equals rock compressive strength. However, bits are typically only 30-40% efficient even at peak performance. That is where the Efficiency Factor comes into place. ExxonMobil sets the Efficiency uniformly to 0.35 regardless of bit type or WOB. Although this value is known from lab data to commonly vary from 0.30 to 0.40, as a trending tool – this error is acceptable. AS Calculation of MSE from surface measurements contain even larger sources of error. AND as any consistent margin of error will tend to shift the curve uniformly left or right. Though the value may not be as accurate as possible, the uniformity of the shift allows the curve to still be used effectively as a visual trending tool.
- CCS Min and Max is preferably acquired from an offset RMA NT study. However, it can be predicted using general field UCS estimates from bit vendors.
- CCS Min and Max is preferably acquired from an offset RMA NT study. However, it can be predicted using general field UCS estimates from bit vendors.
- So, at the rig – WOB and RPM tests are conducted as new formations are entered and the MSE is observed by increasing parameters. If the MSE remains close to the baseline value while raising WOB, the bit is as efficient at the high load as before. ROP will continue to increase linearly with WOB. RPM tests are conducted in a similar manner. Spurious spikes are disregarded unless they persist for several feet. They occur at connections and are associated with light WOB while re-establishing the bottom hole pattern.
- Here is the Drill Off Test example presented in Exxons paper. Notice where the slope of the line is relatively constant for a given formation, bit type, and Rotary Speed. The point at which the ROP stops responding linearly with increasing WOB is referred to as the founder point. This is taken to be the optimum WOB. The founder point is close to the highest ROP that can be achieved within the current operating system (rig limits).
- SPE 74520 recommends pulling a bit when the MSE value has doubled the DOT result in the same formation.
- Brazil BMS-7K 12-1/4” hole section 1 st bit run Smith bit, 7 blades and 19 mm cutters Depth in: 2158m Depth out: 3695 m (1537 m drilled) Dull grade: 8-2-CR-N-X-Y-NR-PR Bit was cored In interval 2340 m to 2675 m it appeared that WOB was not fully transferring to bit. Higher actual SE mix an SE Mu values (CVX equations) as well as high predicted ROP values were observed. Recommended immediate action included wiper trip and/or other such action (mud parameters) to reduce potential drag effects. The torque was steadily increasing as well. Wiper trips were performed and specific energy values decreased indicating that WOB transfer issue had been resolved.
- North Sea – UK Sector 8.5” hole section Depth in: Depth out: Dull grade: Real-Time InterAct Schlumberger Display of MSE and DH Vibration response. Vibration is the most common cause of drilling inefficiency.
- Offshore North Sea, UK Sector 12.25” hole section Depth in: Depth out: Dull grade: Wear Bit Example….when to pull the bit. Actual SE baseline is >200% more than Optimal SE baseline.
- Offshore Cabinda, Angola 8.5” hole section Hughes bit, 6 blades and 16 mm cutters Depth in: Depth out: Dull grade: 4-2-ER-N-X-I-WT-TD Wear Bit Example….when to pull the bit. Actual SE baseline is >200% more than Optimal SE baseline.
- BW-02 Offshore Cabinda, Angola 8.5” hole section All 8 Bladed PDC Bits – MSE values decline w/ RPM increases. Actual SE baseline is >200% more than Optimal SE baseline.
- BW-04 Offshore Cabinda, Angola 8.5” hole section Select bit w/ the best MSE. Actual SE baseline is >200% more than Optimal SE baseline.
- Figure 2 – SeROP Drilling Performance Log for 12 ¼” Hole Section in a Deepwater West Africa Development Well -------------------------------------------------------------------------------------------- This figure illustrates the rock mechanics characterization and real-time SeROP deployment in one of the west African wells. From 12,700’ to 12,850’ drilling inefficiencies were observed due to stickslip caused by high heave. The rig heave compensator system was not functioning properly. As a result, WOB varied from 30 klbs to 0 klbs causing bit bouncing and stick slip. When the problem was resolved a DOT was performed and we can see the established specific energy baseline matching the optimal baseline when optimal cutting efficiency is achieved.
- Figure 3 – SeROP Drilling Peformance Log for Drilling Inefficiency Interval of a Deepwater West Africa Development Well -------------------------------------------------------------------------------------------- There was overall good drilling performance from 12,850’ to TD. However, there are 2 zones of higher SE values indicating drilling inefficiencies at 14,420 to 14,480’ and 14,520 to TD. Whenever specific energy trends increase in this manner beyond optimal baseline values DOTs are performed in attempts to reduce energy consumption and improve cutting efficiency. At 14,480’ we can see how the ROP increased and specific energy improved when optimal parameters where identified. The final interval represents bit wear as the run nears TD.
- Figure 5 – SeROP Drilling Performance Log for a Deepwater Brazil Exploration Well --------------------------------------------------------------------------------- The next study is of a deepwater exploration well in Brazil. The pre-drill offset data was limited to a single well located 33 miles away. The CCS was expected to range between 4000 and 14000 psi with hard stringers approaching 28000 psi. The lithology was interbedded with high shale reactivity issues.
- Figure 6 – SeROP Drilling Performance Log for a Shallow Hole Section for a Deepwater Brazil Exploration Well ------------------------------------------------------------------------------------ Taking a closer look … from 7660’ thru 8000’ it appeared that WOB was not fully transferring to the bit. Higher specific energy values and high predicted ROP values were observed. Recommended immediate action included wiper trips and/or other such action (mud parameters) to reduce potential drag effects. The torque was steadily increasing as well. A wiper trips was performed and specific energy values decreased indicating that WOB transfer issue had been resolved.
- Figure 7 – SeROP Drilling Performance Log for a Bottomhole Section of a Deepwater Brazil Exploration Well ------------------------------------------------------------------------------------------- Intervals from 11,210’ thru 11,880’ experienced high SE values that were identified as possible bit balling (WBM in an area where reactive shales are present). When decreases in ROP and resulting increases in SE occurred, fine nut plugs were pumped to clean the bit. ROP improvement occurred as drilling resumed. At 12,150 m, SE increased and excessive SE values were observed. Fine nut plugs were pumped with no effect (ROP improvement) which indicated a different cause of the inefficiency (not bit balling) possibly bit damage. The bit was pulled and found to be “cored” Ultimately, this run completed 5075’ with a 30% increase in ROP compared with the offset well where the corresponding interval had a maximum run of only 3930’.
- Figure 9 – SeROP Drilling Performance Log Identifying Drilling Inefficiencies Caused by Downhole Vibration of a BHA with 12 ¼” PDC Bit and a 13 ½” Under-Reamer in a Deepwater GOM Development Well ----------------------------------------------------------------------------------------- 12.25” bit w/ 13.5” Anderreamer Hughes bit, 7 blades and 16 mm cutters Depth in: 23071 ft Depth out: 24333 ft (1262 ft drilled) Dull grade: 1-1-CT-N-X-IN-NO-TD ----------------------------------------------------------------------------------------- From the start of this run a DOT was performed identifying the optimum SE baseline accompanying an ROP of 100 fph. Geologic uncertainty dictated an ROP reduction to 75 fph to maintain log correlation. The corresponding reduction in WOB did not provide adequate axial stability and allowed for downhole vibration and drilling inefficiency shown by both the LWD tool response and real-time specific energy monitoring. This is a prime example of how the specific energy can be used with any bit and BHA to gain a better picture of system performance.