Exxon-Limiter Redesign-Reaming and Hole Conditioning 09-14-19.ppt
- 1. Joseph (Joe) W. Witt STP-A Drilling Performance D&S Technical / Drilling Support Team SECTION 17: Reaming and Hole Conditioning
- 2. 2 Objectives • Understand mechanical drag due to filter cake build-up & how to mitigate it • Recognize potential for tool joint related borehole groove patterns • Understand mechanism for bit darting & how to prevent it • Recognize trajectory & steering related borehole patterns • Institute recommended operational practices in preparation for tripping & while tripping • Know how safely backream, if backreaming is required • Diagnose possible causes for drilling BHA/bit torqueing and recommend solutions • Determine root cause of increasing drag on connections and implement operational changes • Diagnose tight spots while tripping and recommend possible mitigation actions
- 3. 3 Outline • Tight Hole Mechanisms • Tripping • Backreaming • Tight Spot Recognition and Response • Closing Summary
- 5. 5 Causes of Tight Hole • Filter cake build-up • Mechanical sliding wear (tool joint wear groove) • Bit darting • Micro-doglegs • Trajectory oscillation patterns • Ledges • Cuttings • Cavings • Other such as undergauge hole or junk
- 6. 6 Cake Growth and Shear Strength Permeable Formation Filtration Control (Bentonite & Polymers) Shear strength develops as the cake is sealed and the differential causes the grain-to-grain stress and shear resistance to increase 3 P 2 Blocking Barite Cake thickens as particles are captured, but it may initially have minimal shear strength Filtrate Blocking and Drill Solids Initial leaky cake contains drill solids and barite 1
- 7. 7 Mechanical Sticking Due to Shear Strength Progression of Mechanical Sticking (not differential sticking) 1. Differential pressure creates force between the grains 2. The grain contact force and the material “friction angle” determine shear strength 3. Pipe becomes stuck when shear strength and shear area exceed available pull Permeable Formation P Filtrate Stab • Will discuss Differential Sticking in separate lecture
- 8. 8 Mechanical Drag in High Strength Cake 8.5" Hole - Drilling Drag Plots Oso 69C Casing FF = 0.20 : OH = 0.25, MW=12.0pgg 7500 8500 9500 10500 11500 12500 13500 14500 150 200 250 300 350 400 Weight indicator with block weight (70kips) Measured Depth (ft) Slack Off (plan) Rotate (plan) Pick Up (plan) Slack Off (actual) Rotate (actual) Pick Up (actual) Pick Up off of slips (actual) S/O (TIH after backream) P/U (TIH after backreaming) ROT (TIH after backreaming) P/U off slips (TIH after backream) Max P/U to break over (TIH) 1-Y1 Top Reduced PU after BR Hookload (kips) 8½” Drilling Drag Plots Formation change Shale to Sand Diverging trend Measured Depth (ft)
- 9. 9 Mechanical Cake Sticking • Mechanical sticking occurs when a thick filter cake is deposited (or re-growth occurs) and the stabilizers/ bit are pulled into the cake • Happens during pipe movement, not when pipe is stationary • Seen as high pulls • Pulling force depends on cake shear strength, which depends on differential pressure across the grains of the cake • Minimizing contact area does not prevent it • Cake may have to be removed by reaming • Can minimize it with use of smaller OD stabilizers, but still have to deal with the bit
- 10. 10 Mitigate Filter Cake Growth and Re-growth 1. Treat fluid with appropriate blocking solids based on Particle Plugging Apparatus test results, not APl FL (Seepage Mitigation Guide) • PPA test simulates downhole temperature, pressure and permeability • Use Aloxite ceramic disks that represent formation permeability • Contact the Mud Specialists for specific details 2. Optimize blocking solids before using “fluid loss” additives to reduce fluid loss 3. Backream each stand once when drilling through permeable formations • Backream at reduced rotary under “vibrations managed” MR MC wow parameters • Conduct reaming whirl test to avoid whirl & any side cutting action
- 11. 11 Manage Filter Cake Growth and Re-growth 4. Use Drill and Seal technique to further condition filter cake, especially in low weight muds (<11.0 ppg) or high overbalance (2000 - 3000 psi) 5. Rotate to break connection, if required 6. Record and plot T&D data to confirm improvement 7. If all this does not work, engage Drilling Technical • There are some specialty additives that may do the trick Discussion: You are planning to drill a 12-1/4” hole that includes sections with very permeable sands. The DD has prepared a proposed BHA which includes a “full gauge stabilizer”. Should you be concerned?
- 12. 12 Use Seepage Guide and Confirm with PPTs Mud Weight (ppg) 10 11 12 13 0 Permeability (Darcy) Barite Solids Only Are Adequate 8 9 1.0 2.0 3.0 4.0 5.0 5 micron CaCO3 5 ppb 5/25 micron CaCO3 5 ppb 5 micron CaCO3 5-10 ppb 5/25 micron CaCO3 5-10 ppb 5/25 micron CaCO3 5 ppb + MicroFiber 5 ppb Contact Operations Support for seepage mitigation design in permeability > 2-3 Darcy
- 13. 13 Mechanical Sliding Wear (Tool Joint Groove) All high angle 3D logs seen to date have contained grooves the length of the borehole that were created by the tool joints
- 14. 14 Mechanical Sliding Wear Increased contact area due to groove • Contributed to differential sticking (Sakhalin, Germany, W. Canada) • Logically worse in soft rock and high angle (EG, Nigeria, Malaysia) • Seen in firm rock with high rotational hours (Hibernia) • Minimize contact area, still pipe time, and rotations • Minimize HWDP at high angle to reduce sticking potential of tool joints • Monitor pulls required to initiate pipe movement after connections • Drill fast and minimize rotating time Wear groove
- 15. 15 Bit Darting EHS Effective Hole Size (EHS) EHS = Bit Dia + O.D. Above Bit 2 If EHS is < OD of Casing Connection: • Increase drill collar size • Run oversized bit sub • Run small stabilizer above bit • Run packed assembly • Use PDC with long gauge (4”+) • Use only newest design bi- center bits – double profile • Can also act like hole curvature Bit Dia OD Above Bit Design BHA to Achieve Effective Hole Size (EHS)
- 16. 16 EHS Exercise • A pendulum assembly is run with 6.25” DCs and 12¼” bit. What is the Effective Hole Size (casing size that can be run without concern for hanging up)? (6.25 + 12.25) / 2 = 9.25” EHS is less than casing collar OD • The rig has an 8” bit sub. Will this provide the EHS required to run 9⅝” casing safely? (8 + 12.25) / 2 = 10.125” EHS is greater than casing but not the collar which is 10.625” • Will a 9” bit sub work? Yes, the EHS is (9+12.25) / 2 = 10.625”
- 17. 17 Micro-Doglegs Are Due to Whirl 1. Bit becomes unbalanced on lamination and whirls 2. High side forces create side cutting 3. DOC is greater on soft formation side Microdoglegs are reduced by standard whirl mitigation practices and redesign Harder Softer If the bit cannot cut sideways (whirl) the bit cannot change direction Can also call this bit-darting
- 18. 18 Ledges - Steering Patterns? Is the RSS steering process creating a pattern?
- 19. 19 Ledges - Reaming Patterns? • There’s instability, but did reaming enhance enlargement? • Enlargement due to repeated reaming to remove cavings? • Shoulder due to difference in rock strength across fault?
- 20. 20 Trajectory Oscillation Patterns Simple Sinusoid Spiraling Hour Glassing Typical patterns that are created by the drilling and reaming process
- 21. 21 Hour Glassing 1. Stabilizer arrives at enlarged hole and develops lateral vibration 2. Bit cuts sideways due to lateral vibration at stabilizer How does an hour glass pattern develop? 3. Stabilizer arrives at gauge hole and bit becomes stable and drills gauge hole 4. Stabilizer arrives at previous bit- enlarged hole and vibration occurs again 5. Gain develops until side-cutting becomes limited
- 22. 22 Trajectory Oscillations with RSS Hour glass pattern with RSS 7m Repeating pattern Rough Ride ?
- 23. 23 Trajectory Oscillations How do sinusoid and spiral develop? Stab or steering unit Gauge torque if not undercut Bit torque due to DOC Whirl allows side- cutting, then reactive torque steers the bit Simple Sinusoid Spiraling RSS control logic can easily produce these patterns
- 24. 24 Example Sinusoidal Trajectory Oscillations 1:75 SCALE COMPOSITE LOG WELL: FIELD: 10.12.21.5 Quirk Creek Depth Rotary RPM & Torque RPM (RPM) 0 100 TORQUE (NM) 0 30000 Bit ROP & WOB WOB (TON) 0 50 ROP (M/HR) 0 50 CaliperX CAL(X) IN 10 7.5 GAUGEX IN 10 7.5 CaliperY CAL(Y) IN 7.5 10 GAUGEY IN 7.5 10 MSE MSE (KSI) 0 300 GAMMA RAY API 0 150 1420 1430 1440 1450 Depth TORQUE (NM) 0 30000 RPM (RPM) 0 100 Rotary RPM & Torque ROP (M/HR) 0 50 WOB (TON) 0 50 Bit ROP & WOB GAUGEX IN 10 7.5 CAL(X) IN 10 7.5 CaliperX GAUGEY IN 7.5 10 CAL(Y) IN 7.5 10 CaliperY GAMMA RAY API 0 150 MSE (KSI) 0 300 MSE Period equal distance from bit to bottom motor stab (~1m) EBXS42 (Insert bit) EBXS42 (Insert bit) 1900 1950 2000 2050 2100 2150 2200 TORQUE (NM) 0 30000 ROP (M/HR) 0 50 GAUGEX IN 10 6 GAUGEY IN 6 10 GAMMA RAY API 0 150 1:240 SCALE COMPOSITE LOG WELL: FIELD: 10.12.21.5 Quirk Creek Depth Rotary RPM & Torque RPM (RPM) 0 100 TORQUE (NM) 0 30000 Bit ROP & WOB WOB (TON) 0 50 ROP (M/HR) 0 50 CaliperX CAL(X) IN 10 6 GAUGEX IN 10 6 CaliperY CAL(Y) IN 6 10 GAUGEY IN 6 10 MSE MSE (KSI) 0 300 GAMMA RAY API 0 150 1900 1950 2000 2050 2100 FM3751 (PDC) Period equals distance from bit to top motor stab (~10m)
- 25. 25 Cuttings and/or Cavings Build-up • Insufficient or inadequate hole cleaning • Possibly hole breakout • May be associated with gauge hole section or enlarged hole area • May only be a “dune” • Could be for 100’s of feet or meters
- 26. 26 Tripping
- 27. 27 Tripping Procedure • Is a drilled hole a “clean enough” hole to trip? • Definitely NOT!!! • In low angle / vertical holes, cuttings are only suspended in the drilling mud so you need only to circulate them out • Tripping is possible without cleaning up the hole but this is not generally a good practice • In high angle holes, there is ALWAYS a cuttings bed • You must “MR MC wow” (maximum rotation and maximum circulation without whirl) the hole clean first; however, a steady-state equilibrium cuttings bed will remain no matter how long you MR MC wow • Drilling operations can actually continue with a very high bed; however, tripping may plant the drill string
- 28. 28 In Preparation for Tripping • Must 1st clean up the hole • For low angle / vertical holes, the old tried & true practice of “circulating bottoms up 1-1/2 times and POOH” is fine (can be dangerous on high angle wells) • For high angle wells, must MR MC wow until shakers clean up (i.e. return to normal background circulating levels like what you would expect to see after circulating 1-1/2 bottoms up on low angle hole) - THIS DOES NOT MEAN NO CUTTINGS AT ALL!!! • Monitor ECD to level out and stabilize indicating steady- state conditions with respect to cuttings removal • Reduce off-bottom rotary speed to manage vibrations • Typically requires 3 - 5 bottoms up cycles • Cuttings (and especially cavings) sort of “hop, skip and jump” out of the high angle hole requiring multiple cycles • Goal is to reduce the cuttings bed to a “safe tripping level”
- 29. 29 Example MR MC wow’ing Cuttings Returns While Circulating: 8-1/2" Hole Drilled w/ PowerDrive 0 3 5 8 10 13 15 18 20 23 25 28 30 33 35 38 40 2 : 3 0 4 : 1 0 4 : 5 5 5 : 2 5 6 : 3 0 1 1 : 1 0 1 2 : 0 0 1 3 : 0 0 1 4 : 0 0 1 6 : 0 0 1 6 : 3 5 1 7 : 2 0 1 7 : 5 5 1 8 : 2 0 1 8 : 5 0 1 9 : 2 0 1 9 : 4 5 2 0 : 1 0 2 0 : 5 0 Time Cuttings returns ( lb/min ) Circulating immediately after drilling to TD @ 11,012' MD. Rotating at 120 RPM, 585 GPM on hole, 242 GPM on booster. B/U#2 @ 04:45 B/U#1 @ 03:50 B/U#3 @ 05:30 B/U#4 @ 06:30 BU#1 @ 11:20 BU#2 @ 12:20 Circulating at TD after making a wiper trip to the 9-5/8" shoe and running back to bottom. Rotating at 150 RPM, 580 GPM on hole, 242 GPM booster. BU#3 13:30 BU#1 16:10 BU#2 17:20 BU#3 18:10 Backreaming below 9-5/8" shoe after wiper trip run to TD. BU#4 19:00 BU#5 20:10
- 30. 30 In Preparation for Tripping • While MR MC wow’ing, rack back 1 stand every 30 minutes so as not to create an enlarged area / ledge from rotating and reciprocating (R&R) too long in one spot • Recommend slow R&R cycles (10 – 15 minutes) • In soft rock that is prone to undercutting and dropping angle, slide back down (instead of rotating) with bit pointed slightly upwards if possible • Not critical in low angle / vertical wells and/or hard rock • However, if bit / BHA is whirling you still may enlarge the hole MR MC wow
- 31. 31 In Preparation for Tripping • Do not R&R the same stand for extended periods especially across permeable formations • May create a tool joint trench • May whirl cut the filter cake leading to poor quality cake and getting differentially stuck • Monitor the shakers throughout the entire process recording cuttings size, shaker loading, cuttings weight vs. time, cuttings volume vs. hole volume drilled, sloughing shale, cavings, etc This operation has stuck several BHAs Wear Groove
- 32. 32 Tripping: Low Angle / Vertical Wells 1. Finish circulating out the hole clean 2. Confirm tripping swab is not an issue with respect to wellbore instability as discussed in WBS lecture • If swabbing causes hole collapse, then backream out of hole and/or slow pump out as per Top 40 #12: Pump out of the hole on trips 3. If swabbing is not an issue, POOH on top drive or elevators (no pumps & no rotation) 4. Record PU drag per stand and plot vs. predicted on a drag risk chart (overlay with previous trips) 5. Monitor drag risk plot looking for trends that diverge from predicted or previous trips (will discuss drag monitoring later)
- 33. 33 Tripping: Low Angle / Vertical Wells 6. Assume all tight spots are borehole hole quality related (i.e. borehole patterns, ledges, grooves, etc.) unless BHA is pulling through permeable formation 7. Set overpull limits for tripping that minimize getting mechanically jammed in the hole (i.e. 20 – 30k lbs max) 8. If limit is reached, then slack back off until assembly is free and clear of the tight spot 9. If you have a top drive, then bring up rotary and circulation rates (over about 30 secs) in preparation for backreaming
- 34. 34 Tripping: Low Angle / Vertical Wells 10.Slowly wash and ream thru the tight spot while maintaining the rotary speed at reduced rate to minimize whirl 11.Ream only as needed to eliminate tight spot 12.Re-check tight spot without pumps or rotary 13.If the tight spot is in a permeable formation, then it may be due to filter cake quality or re-growth Permeable Formation P Filtrate Stab Do not attempt to pull through as you may wedge-in the stabilizers
- 35. 35 Tripping: Low Angle / Vertical Wells 14.If determined to be filter cake related, then condition and treat the permeable formation as per earlier Manage Filter Cake Growth discussion 15.If you working on a kelly rig, then you will have to circulate and ream as best you can 16.Continue process of POOH on elevators or top drive, repeating above steps as needed
- 36. 36 Tripping: High Angle Wells 1. Finish MR MC wow’ing 2. Confirm tripping swab is not an issue with respect to wellbore instability • If swabbing causes hole collapse, then backream out of hole and/or slow pump out as per Top 40 #12 3. If swabbing is not an issue, POOH on top drive or elevators (no pumps & no rotation) 4. Record PU drag per stand and plot vs. predicted on a drag risk chart (overlay with previous trips) 5. Monitor drag risk plot looking for trends that diverge from predicted or previous trips (will discuss drag monitoring later) 6. Assume all tight spots are cuttings (and/or cavings) beds
- 37. 37 Tripping Through Cuttings Beds Remember, you always have a steady-state cuttings bed remaining no matter how long you MR MC wow (say 1 - 3” thick, maybe more) Bed can also have dunes in it, especially around enlarged hole sections – and may also contain cavings
- 38. 38 Tripping: High Angle Wells 7. Limit PU drag overpull to 25 - 30k lbs 8. Do not attempt to just pull through tight spots - This can be dangerous - You will get stuck 9. Do not initiate rotation and circulation in the tight spot • If it is cuttings beds, then you could fluidize the high bed and cause a pack-off 10.Run back in the hole 1 - 2 stands to get BHA away from the tight spot • If tight spot was encountered immediately (i.e. no signs of increasing drag over the stand being pulled), then just dropping back to bottom of the stand will probably be sufficient 11.Initiate pumps slowly and then initiate rotation slowly • It is preferred to get the mud circulating before starting rotation, especially at avalanching angles
- 39. 39 Tripping: High Angle Wells 12.Bring both rotation and pumps up to full speed (in 30 secs or so) 13.MR MC wow at reduced RPMs for 15 - 30 minutes to displace cuttings uphole 14.Shutdown and attempt to pull back through tight spot on top drive or elevators 15.If tight spot has disappeared, then tight spot was probably cuttings (or cavings) 16.Continue POOH on top drive or elevators 17.Be aware that you may encounter cuttings bed tight spots further up hole - If so, then you may want to MR MC wow for 2 - 3 bottoms up again
- 40. 40 Tripping: High Angle Wells 18.If tight spot has not disappeared, then tight spot is probably not cuttings (maybe cavings, ledge, groove, filter cake, etc.) and backreaming may be required 19.Again, run in hole as needed to get BHA away from tight spot (bottom of stand is probably sufficient) 20.Initiate pumps slowly and then initiate rotation slowly while bringing them up to reaming speeds 21.Backream through tight spot at reduced RPMs so as not to whirl enlarge the hole • Normally there is no need to backream at high “drilling- like” speeds; 80 – 120 rpms should be sufficient • It is always a best practice to circulate at maximum rates unless the hole is packing off – If you have enlarged hole, you need all the circulation you can get
- 41. 41 Tripping: High Angle Wells Backreamed interval NO CUTTINGS BED Cuttings Backreaming pushes the tripping cuttings bed immediately above BHA CREATING A DUNE Backreaming
- 42. 42 Tripping: High Angle Wells 22.Backream only through “tight spot” interval (say 1 joint or 1 stand) - Don’t need to backream several hundred feet or back to the shoe 23.As the previous slide showed, backreaming places a large cuttings bed “dune” just above the BHA 24.MR MC wow for 15 - 30 minutes or so prior to tripping again to spread out the cuttings dune • Must reduce the bed back to a safe tripping height before continuing to POOH 25.If several hundred feet or meters are backreamed, then you will need to MR MC wow for 2 - 3 bottoms up again 26.Continue POOH on top drive or elevators 27.Watch PU drag trend and use it as an indictor for additional circulation and rotation needs
- 43. 43 Watch For Pack-offs While Backreaming Pack-offs can occur when the BHA/stabilizer is backreamed through an excessive cuttings bed which accumulates in “caved-in” (enlarged) intervals, lifting a large volume of cuttings into the flowstream. This large volume of cuttings must then pass through the bottleneck created by the drill string & BHA and the more gauge hole ID at the top of the “caved-in” interval. The result is a “pack-off” around the BHA
- 44. 44 Tripping: High Angle Wells 28.If a pack-off occurs, then immediately slow down the pump rate (do not want to “pack it in”) and attempt to drop back down hole away from the pack-off 29.After pack-off has cleared, work the assembly through the interval while staging up circulating and rotary speeds 30.Pack-offs can also occur due to other reasons such as “pulling too fast” or not watching the pump pressure or torque gauge 31.If the pack-off can not be cleared, then you will have to work the assembly playing with torqueing and slumping while attempting to re-gain circulation • Be aware that rotation without circulation can create extreme heat and may fail the drill string – See Top 40 “Oldies But Goodies” #15: Avoid extended periods
- 45. 45 Backreaming
- 46. 46 Backreaming – When and Why • Generally for one of the following reasons: • Remove the cuttings bed in preparation for running casing or liner or completion assembly • Eliminate tight spots • When floating casing or liner (can’t circulate) • When the rig can not provide sufficient MR MC parameters to reduce the cuttings bed to a safe tripping height • Enlarged hole hinders hole cleaning • Mitigate hole instability from swabbing • Because someone wants to do it • When is it really needed? • Not an easy, straight forward answer • In general, most teams only BR when they have to • We recommend that you only BR when you have to
- 47. 47 In Preparation for Backreaming • Normally performed with the drilling assembly; however, the BHA cost, if lost in hole, may warrant using a “cheap dumb-iron assembly” • Each team will have to evaluate this option but normally this is NOT done • Doing this obviously requires POOH, changing assemblies and TBIH • If done so, then all that is needed is a bit (or equivalent like a hole opener), stab, 1-DC, stab and HWDP/jars • Stabs are required to help lift cuttings into flow stream, especially at top DC • Stabilizer fluidizes cutting bed around the HWDP instead of around the larger OD DCs • Use open or large nozzles to maximize flow rates
- 48. 48 Backreaming Video • Tripping out of the hole • Pulling out • Pumping out • Backreaming out URC Video
- 49. 49 How to Backream 1. Drilling engineer should run ToolPro’s hole cleaning model to calculate acceptable pulling speeds based on the given conditions • It pays to be conservative here, so do not push the speed 2. Have rig supervisor review the backreaming procedure with key personnel (e.g. drillers, directional drillers, mud loggers, etc.) • Show backreaming video 3. Rig supervisor or toolpusher or DD should be on the rig floor at all times monitoring the backreaming process 4. Reduce the cuttings bed with MR MC wow before starting the backreaming process • Be sure to reduce rotary speed (60 – 80 – 120 rpms) • Rack back a stand every 15 – 30 minutes as discussed earlier
- 50. 50 How to Backream 5. Not necessary to circulate more than 1 – 2 cycles because you will be re-loading the borehole with the remaining cuttings bed; however, most teams elect to MR MC wow for the full 3 – 5 cycles 6. Initiate pumps slowly and then initiate rotation slowly • It is preferred to get the mud circulating before starting rotation, especially at avalanching angles • Perform a RPM whirl test (or use vibrations sensors) to find vibration sweet spot 7. Allow the pump pressure and torque to stabilize before starting the backreaming process 8. Backream at a pulling speed “no-faster” than 5 minutes per stand 9. Record and monitor PU hookloads and torque trends
- 51. 51 How to Backream 10.Watch torque and pump pressures - Adjust operations based on responses • BEWARE OF ENLARGED HOLE - PACKOFF POTENTIAL • If a pack-off occurs, do not pull up into the bed • Shutdown pumps and RIH 1 - 2 stands • Re-establish full circulation and rotation if possible 11.Prior to racking back each stand, MR MC wow for 3 - 5 minutes • Pushes cuttings bed safely above BHA to provide a clear space in the event: • that avalanching occurs or • that the driller picks up prior to getting the pumps going 12.Do not backream into a casing shoe that has a rathole below it (enlarged area filled with cuttings) • Stop just prior to top of DC’s entering the rathole • MR MC wow for 15 - 30 minutes and then “pull” into shoe
- 52. 52 How to Backream 13.If rathole is problematic (pack-offs), then you may have to slowly wash and ream through it to help clean it out 14.Casing is not a safe haven (will still have cuttings beds) 15.Stop backreaming process when hole angle reaches about 35 - 40° 16.If you have to shutdown for more than 10 – 15 minutes with the BHA in hole angles around 40 - 60°, then BE CAREFUL • You are in avalanching territory • Consider MR MC wow’ing for 1 - 2 bottoms up prior to shutting down 17.Always MR MC wow for 2 - 3 bottoms up after backreaming is completed and before POOH (in both open or cased hole) 18.Finish POOH on top drive or elevators
- 53. 53 Backreaming Problems • If pack-offs start occurring, then you are either: • Picking up before establishing full circulation and rotation and the BHA is “plowing” into the bed above or • Pulling speed is too fast for the MR MC wow parameters or • Pulling the BHA into an enlarged hole section • What’s the “fix” (What is the fix for the next well?) • Get rotation and circulation fully stabilized before pulling • Slow down – typical speeds are 3 – 4 stands / hr • Pulling speed may need to slow to 30 min to 1 hr / stand • Reduce rotary speed preferably to reducing pump rate • Slowly “inch up the hole” and don’t be surprised if you need to drop down a few feet / meters periodically • BE PATIENT and work your way through the interval • If BHA includes Den/Neu/Sonic tools, then get a hole caliper of the problem interval
- 54. 54 Tight Spot Recognition and Response
- 55. 55 Recognition and Response Logical Potential NPT Mitigate hazards to the economic limit of design Historical Near Miss Treat near misses observed in historical data as actual NPT Real-Time Near Miss React to every event observed in real-time NPT i.e., tight hole reported on trips, high LWD failure rate, fishing operations, enlarged hole on calipers, seepage losses, reaming to reduce drag, packoff with high ROP ............. i.e., high overbalance, marginal MW for stability, limited hydraulics for hole cleaning, small drilling window, extreme throw ................ i.e., drag in sands on trips, packoffs while reaming, torque fluctuations, unusual friction factors, cavings on shaker, sweep results, seepage losses, ballooning, cuttings load trends, bridges after trips in vertical wells, bit damage patterns, MSE and vibrations data ........................................................... i.e., stuck pipe, reaming time, LWD failures, sidetracks, lost returns, inadequate formation evaluation, unscheduled casing, poor well productivity, fishing operations.................. ................. • Watch for hole problems while drilling and tripping • Run diagnostic tests to determine problem and solution
- 56. 56 Tight Spots • As noted earlier at start of lecture, tight spots can be from numerous causes: • Filter cake build-up • Mechanical sliding wear (tool joint groove) • Bit darting • Micro-doglegs • Trajectory oscillation patterns • Ledges • Cuttings • Cavings • Junk • Undergauge hole • Other
- 57. 57 String Torqueing Up While Drilling • Indicator of whirl induced borehole patterns • Not drilling a “fully gauge hole” • Stabs and/or bit are getting jammed • Could be due to “undergauged” hole due to undergauge bit • Could be junk • Could be formation based
- 58. 58 Torqueing Diagnostics and Response 1. Re-examine the MSE and vibration sensor data 2. Adjust WOB and RPM as per vibrations lecture 3. PU, shutdown rotary and let all vibrations calm down • Re-start drilling process with med-high WOB and low RPM until 1st stabilizer is buried (try to change the pattern and/or stop the gain) 4. PU off-bottom or 1 – 2 stands to see if erratic torque smoothes out (maybe borehole pattern or junk) • Slowly rotate and slack back off to bottom to determine when erratic torque re-starts 5. Look at offset wells – Could it be formation driven? 6. Pull up real time digital drilling data (1 sec data preferred) • Are we reaming needlessly on connections creating patterns? • Is the RPM reduced before coming off-bottom? • Look for torque and rpm oscillations (back-and-forth)
- 59. 59 Torqueing Diagnostics and Response 7. Examine BHA when retrieved – Take lots of pictures • Worn or damaged stabilizer blades (whirl, drilling on ledges) • Signs of junk damage on BHA • Bit damage • If no near-bit stabilizer or equivalent, then add one 8. Run new bit and/or BHA that is more vibration stable (requires Vybs analysis) • Replace stabilizers with roller reamers to eliminate stabilizer generated torque from high side forces • Redesign bit to increase gauge length, add tapered/undercut gauge and eliminate all active gauge 9. Run multi-arm oriented caliper log looking for borehole patterns – Redesign BHA and bit 10.Examine raw (unfiltered) survey data looking for hidden doglegs – Modify steering assembly
- 60. 60 Increasing Drag on Connections • Cuttings bed build up • Wellbore instability (cavings) • Filter cake growth • Borehole patterns Permeable Formation Filtration Control (Bentonite & Polymers) P Blocking Barite Filtrate Blocking and Drill Solids
- 61. 61 Drag Diagnostics and Response 1. Examine GR/Res & Den/Neu log, if being run • Is the BHA in a permeable formation? • Does the drag increase coincide with the BHA entering a permeable formation? • Does reaming up and down reduce the drag but as soon as you drill the next stand down, the drag is back? • Does the drag occur while picking up or slacking off over the entire stand (not just off-slips)? • Does MR MC wow (30 min to 2 – 3 BU) have minimal effect? • Is BHA stabilized properly (mitigating differential sticking) – If not, then stabilize it as per Top 40!!! 2. If you answered Yes to most of these questions, then you are probably experiencing thick filter cake and/or filter cake re-growth • See Manage Filter Cake Growth info as discussed earlier
- 62. 62 Drag Diagnostics and Response 3. If MR MC wow reduces the drag (especially with multiple bottoms up), then you may be experiencing cuttings load up or cavings • What came across the shakers (cuttings or cavings) and was it excessive? Are large cavings staying in the hole? • Take pictures and discuss with office 4. If cavings, then raise the mud weight and contact Drilling Technical for support in this area 5. If cuttings, then, if possible, increase pump rate and/or rotary speed • Examine mud properties – Do you have sufficient gel strengths and/or 6 rpm values? - Adjust as needed • Does the increased drag pose a problem with respect to drill string tensile or torsional loads or rig capabilities? 1. If yes, then you may have to adjust ROP (or add lubricants, etc) 2. If no, then is it really a problem? Continue drilling
- 63. 63 Drag Diagnostics and Response 6. If the drag is only when “coming off-slips” and your BHA is across permeable formation, then you are getting indicators of differential sticking • Examine BHA and revise as per Top 40 to mitigate differential sticking • Do you have too much HWDP, possibly getting differentially stuck in a keyseat groove (must have permeability)? • Talk with your Drilling Fluids contact in Drilling Technical – May need to adjust mud properties or mud additives to improve filter cake quality 7. If up and down reaming solves the problem (especially if your BHA is not across permeable formation), then you are probably getting indicators of borehole patterns • Look at your GR/Res log – Are you drilling laminated rock that might be causing micro-doglegs and/or bit darting? • See Torqueing Diagnostics and Response
- 64. 64 Tight Spots While Tripping • Cuttings bed build up (or duning) • Wellbore instability (cavings) • Growing filter cake • Borehole patterns • Undergauge hole (or what appears to be, which is probably borehole pattern related) Simple Sinusoid Spiraling
- 65. 65 Tripping Diagnostics and Response Low Angle / Vertical Hole 1. Did you experience pack-offs? – If yes, then you may have enlarged hole and/or insufficient gel strengths allowing cuttings/cavings to fall in around the BHA • Circulate out and look at the returns • If cavings, raise mud weight • Note: Tripping swab may have caused the problem • Check APWD trip data to check swab (calculate w/ ToolPro) • Pump out of hole or increase mud weight • If cuttings and no signs of cavings, then check your mud properties for sufficient gel strengths • Even if there are no signs of cavings you still may be experiencing hole enlargement (especially in water based mud as shale cuttings can disperse) – May require higher gels strengths if this is the case
- 66. 66 Tripping Diagnostics and Response Low Angle / Vertical Hole 2. Is the BHA tripping through permeable formation? • If yes, then it may be due to filter cake growth or re-growth - See Manage Filter Cake Growth as discussed earlier 3. If not pack-off related or filter cake growth related, then it is most probably borehole pattern related • See Torqueing Diagnostics and Response • Refer back to Bit Performance Limiters lecture on vibrations and whirl patterns 1900 1950 2000 2050 2100 2150 2200 TORQUE (NM) 0 30000 ROP (M/HR) 0 50 GAUGEX IN 10 6 GAUGEY IN 6 10 GAMMA RAY API 0 150 1:240 SCALE COMPOSITE LOG WELL: FIELD: 10.12.21.5 Quirk Creek Depth Rotary RPM & Torque RPM (RPM) 0 100 TORQUE (NM) 0 30000 Bit ROP & WOB WOB (TON) 0 50 ROP (M/HR) 0 50 CaliperX CAL(X) IN 10 6 GAUGEX IN 10 6 CaliperY CAL(Y) IN 6 10 GAUGEY IN 6 10 MSE MSE (KSI) 0 300 GAMMA RAY API 0 150 1900 1950 2000 2050 2100
- 67. 67 Tripping Diagnostics and Response High Angle Hole 1. Always drop down, MR MC wow for 15 – 30 minutes and attempt to pull back through tight spot as per earlier Tripping Procedure discussion 2. If tight spot disappeared, then it is probably cuttings or cavings – Continue as per Tripping Procedure • If tight spot occurs again and above steps indicate cuttings or caving, then MR MC wow for 2 – 3 bottoms up to see returns • If cuttings, then trip process can continue as per Tripping Procedure • If cavings, then raise mud weight and evaluate if swabbing is the root cause (pump out, backream out or raise mud weight) • Also if cavings, then, if possible, obtain Den/Neu/Sonic log across problem interval to look for hole enlargement
- 68. 68 Tripping Diagnostics and Response High Angle Hole 3. If tight spot is not due cuttings or cavings, then does it appear to be related to filter cake growth or re-growth • See Drag Diagnostics and Response discussion • If yes, then condition formation as per Manage Filter Cake Growth discussion 4. Is the BHA across a permeable formation and are you experiencing high drag “coming off slips”? • If yes, then you may be experiencing differential sticking • See Drag Diagnostics and Response discussion 5. If none of the above, then it is probably borehole pattern related • See Torqueing Diagnostics and Response • Refer back to Bit Performance Limiters lecture on vibrations and whirl patterns
- 69. 69 Closing Summary • Do not mistake mechanical sticking problems related to filter cake for differential sticking – Different solutions • Be weary of TJ grooves, especially from HWDP, as they can get you differentially stuck – Run caliper logs • Borehole patterns come in many shapes and sizes & they are always present – Mitigate whirl • MRMC wow for 3 – 5 bottoms up prior to all trips – Optimize based on field experience • Do not reciprocate in the same interval when MRMC wowing – Will dig a trench / groove in soft rock • Always treat tight spots as cuttings beds when tripping in high angle holes – Prove and/or disprove first • Backreaming is risky and we should only do it when the hole requires it
- 70. 70 Closing Summary • Torqueing up while drilling is probably borehole pattern related – Examine your bit and stabs & modify BHA to mitigate • Increasing drag on connections has several causes, some of which may become problematic (patterns and cavings) and some of which may not (cuttings beds) • Tight spots while tripping may stick the drill string if you do not diagnose them correctly