Contents Figures...........................................................................................................................................................................................................vii Tables..............................................................................................................................................................................................................xii PREface..........................................................................................................................................................................................................xiii 1

Terms and Calculations............................................................................................................................................ 1-1

Definition of UBD.........................................................................................................................................................................................................1-1 Formation Pressure......................................................................................................................................................................................................1-1 Hydrostatic Pressure...................................................................................................................................................................................................1-2 Basic Pressure Calculations.....................................................................................................................................................................................1-3 Pressures............................................................................................................................................................................................................................1-5 UBD Matrix .....................................................................................................................................................................................................................1-6 Summary............................................................................................................................................................................................................................1-7

2 UBD Guidelines......................................................................................................................................................................2-1 Uses of UBD....................................................................................................................................................................................................................2-1 Conditions that Control UBD................................................................................................................................................................................2-4 UBD in Horizontal Drilling......................................................................................................................................................................................2-7 Geothermal Drilling.....................................................................................................................................................................................................2-8 UBD Drilling Programs..............................................................................................................................................................................................2-8 Summary............................................................................................................................................................................................................................2-9

3 Surface Control Equipment.................................................................................................................................. 3-1

BOP Stacks in UBD......................................................................................................................................................................................................3-1 Rotating Equipment.....................................................................................................................................................................................................3-3 Annular Preventers................................................................................................................................................................................................... 3-10 Ram Preventers ...........................................................................................................................................................................................................3-12 Chokes...............................................................................................................................................................................................................................3-12 Choke Manifolds.........................................................................................................................................................................................................3-14 Separators........................................................................................................................................................................................................................3-15 Standpipe Manifolds.................................................................................................................................................................................................3-19 Snubbing Units.............................................................................................................................................................................................................3-19 Summary.........................................................................................................................................................................................................................3-20

4 Downhole Tools................................................................................................................................................................. 4-1 Drill Pipe Valves..............................................................................................................................................................................................................4-1 Snubbing Units...............................................................................................................................................................................................................4-6 UBD with Motors ........................................................................................................................................................................................................4-8 Air Hammers .............................................................................................................................................................................................................. 4-10 Special Systems for Gaseated Mud.................................................................................................................................................................4-12 Bits........................................................................................................................................................................................................................................4-13 MWD, LWD, EMWD, and Steering Tool Systems...................................................................................................................................4-13 Summary..........................................................................................................................................................................................................................4-15

5 Gases and equipment..................................................................................................................................................... 5-1 Introduction......................................................................................................................................................................................................................5-1 Air...........................................................................................................................................................................................................................................5-1 Nitrogen..............................................................................................................................................................................................................................5-3

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Natural Gas.......................................................................................................................................................................................................................5-6 Exhaust Gas......................................................................................................................................................................................................................5-8 Summary............................................................................................................................................................................................................................5-9

6 Circulation and The Fluid Column............................................................................................................... 6-1

UBD Bottomhole Pressure Reduction..............................................................................................................................................................6-1 Mud Flow...........................................................................................................................................................................................................................6-2 Stripping and Snubbing............................................................................................................................................................................................6-5 Mud Caps..........................................................................................................................................................................................................................6-6 Summary............................................................................................................................................................................................................................6-9

7

Flow and Mud-Cap Drilling.................................................................................................................................. 7-1

Driller's Method.............................................................................................................................................................................................................7-1 Liquid, or Flow, Drilling.............................................................................................................................................................................................7-1 Summary............................................................................................................................................................................................................................7-9

8 Liquid-Gas Fluids................................................................................................................................................................ 8-1 Introduction......................................................................................................................................................................................................................8-1 Use and Advantages of Gaseated Systems..................................................................................................................................................8-2 Problems and Limits to Gaseated Drilling.....................................................................................................................................................8-4 Equipment.........................................................................................................................................................................................................................8-5 Techniques.........................................................................................................................................................................................................................8-8 Summary..........................................................................................................................................................................................................................8-10

9

Foam Drilling......................................................................................................................................................................... 9-1

Introduction......................................................................................................................................................................................................................9-1 Foam Systems.................................................................................................................................................................................................................9-1 Foam Makeup.................................................................................................................................................................................................................9-3 Uses.......................................................................................................................................................................................................................................9-3 Problems and Limits with Foam..........................................................................................................................................................................9-6 Equipment for Foam Drilling.................................................................................................................................................................................9-7 Techniques with Foam Systems...........................................................................................................................................................................9-8 Surface Problems with Foam...............................................................................................................................................................................9-10 Workover Operations with Foam Units........................................................................................................................................................9-11 Foam Materials.............................................................................................................................................................................................................9-11 Foam Disposal..............................................................................................................................................................................................................9-11 Corrosion Control......................................................................................................................................................................................................9-12 Summary..........................................................................................................................................................................................................................9-13

10 Air-Gas, Mist, and Foamed Mist Drilling.................................................................................................10-1 Introduction....................................................................................................................................................................................................................10-1 Advantages to Air-Gas Drilling..........................................................................................................................................................................10-1 Limits to Air-Gas Drilling.......................................................................................................................................................................................10-2 Cutting Size.....................................................................................................................................................................................................................10-3 Mist......................................................................................................................................................................................................................................10-4 Bit Selection....................................................................................................................................................................................................................10-4 Volume Requirements..............................................................................................................................................................................................10-4 Gases for Air-Gas Drilling.....................................................................................................................................................................................10-5 Air Compressors..........................................................................................................................................................................................................10-6 Air-Gas Drilling Tools...............................................................................................................................................................................................10-7 Location Setup...........................................................................................................................................................................................................10-11 Techniques....................................................................................................................................................................................................................10-11 Misting............................................................................................................................................................................................................................10-12 Summary.......................................................................................................................................................................................................................10-13

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11 Problems....................................................................................................................................................................................11-1 Choke Washes Out....................................................................................................................................................................................................11-1 Choke Plugs....................................................................................................................................................................................................................11-2 Gas Reaches Surface.................................................................................................................................................................................................11-2 Lost Circulation............................................................................................................................................................................................................11-2 High Annular Pressure.............................................................................................................................................................................................11-3 Hole in Drill Stem........................................................................................................................................................................................................11-3 Parted Pipe.......................................................................................................................................................................................................................11-3 Plugging............................................................................................................................................................................................................................11-4 Nozzle Wash Out........................................................................................................................................................................................................11-4 Other Problems............................................................................................................................................................................................................11-4 Workover..........................................................................................................................................................................................................................11-5 Sumary...............................................................................................................................................................................................................................11-6

12 Corrosion and Scale....................................................................................................................................................12-1

Corrosion.........................................................................................................................................................................................................................12-1 Scale.....................................................................................................................................................................................................................................12-6 Summary..........................................................................................................................................................................................................................12-7

13 Rigging UP.................................................................................................................................................................................13-1 Locations Considerations......................................................................................................................................................................................13-1 Gas Sources....................................................................................................................................................................................................................13-1 BOP Stack.........................................................................................................................................................................................................................13-2 Flare and Blooey Lines............................................................................................................................................................................................13-2 Standpipe Manifold...................................................................................................................................................................................................13-2 Separators........................................................................................................................................................................................................................13-3 Rig Checklist...................................................................................................................................................................................................................13-4 Summary..........................................................................................................................................................................................................................13-4

14 Flares and Flaring..........................................................................................................................................................14-1 Introduction....................................................................................................................................................................................................................14-1 Common flare Practices..........................................................................................................................................................................................14-1 Everyday Concerns.....................................................................................................................................................................................................14-2 Proper Flare Operation............................................................................................................................................................................................14-4 Additional Practices...................................................................................................................................................................................................14-5 Flare Design....................................................................................................................................................................................................................14-5 Summary..........................................................................................................................................................................................................................14-6

Appendix................................................................................................................................................................................................... A-1 Glossary.................................................................................................................................................................................................. G-1 Bibliography........................................................................................................................................................................................B-1

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vi

Figures 1.1. 1.2. 1.3. 1.4. 1.5. 1.6.

Choke controls pressure against standpipe gauge................................................................................................... 1-1 Pressures............................................................................................................................................................................. 1-1 Formation pressure.......................................................................................................................................................... 1-2 Earth pressures.................................................................................................................................................................. 1-3 Average gradients in ppg of several muds................................................................................................................... 1-5 Annulus density varies in UBD...................................................................................................................................... 1-6

2.1. 2.2. 2.3. 2.4. 2.5. 2.6. 2.7. 2.8. 2.9.

The effect on drilling rate of reduced mud weight or reduced differential pressure........................................ 2-1 Reduce lost circulation with UBD................................................................................................................................ 2-2 Mud filtrate damages formation..................................................................................................................................... 2-3 No filter cake or filtrate forms in UBD because flow is into wellbore................................................................ 2-3 Differential sticking and filter cake................................................................................................................................ 2-4 Geopressured shale is unstable and sloughs............................................................................................................... 2-5 Salt flows to zone of least pressure.............................................................................................................................. 2-5 Shattered coal forms washouts...................................................................................................................................... 2-6 Unconsolidated sand can collapse into the hole and create problems as shown in this horizontal section.................................................................................................................................................................................. 2-6





3.1. Typical underbalanced blowout preventer stack....................................................................................................... 3-1 3.2. Variable rams..................................................................................................................................................................... 3-2 3.3. Simple BOP stack on workover rig.............................................................................................................................. 3-3 3.4. Stake down blooey lines.................................................................................................................................................. 3-3 3.5. DHS 1400........................................................................................................................................................................... 3-4 3.6. Rotating control heads.................................................................................................................................................... 3-4 3.7. Rotating control head elements.................................................................................................................................... 3-5 3.8. Hydraulic module.............................................................................................................................................................. 3-5 3.9. Workover stripper head Type JU.................................................................................................................................. 3-6 3.10. Cutaway of Varco Shaffer Pressure Control While Drilling PCWD...................................................................... 3-6 3.11. Rotating blowout preventer........................................................................................................................................... 3-7 3.12. Rotating blowout preventer cutaway........................................................................................................................... 3-7 3.13. Model 7100........................................................................................................................................................................ 3-8 3.14. Smith-Grant rotating head.............................................................................................................................................. 3-8 3.15. Causes of packer damage................................................................................................................................................ 3-9 3.16. Annular preventer........................................................................................................................................................... 3-10 3.17. Hydril GK......................................................................................................................................................................... 3-11 3.18. Shaffer Annular................................................................................................................................................................ 3-11 3.19. Cameron Annular............................................................................................................................................................ 3-11 3.20. Pipe, blind, and shear rams............................................................................................................................................ 3-12 3.21. Swaco super choke 10,000 and 20,000 psi capability............................................................................................. 3-13 3.22. Swaco super choke........................................................................................................................................................ 3-13 3.23. Cameron plug type choke............................................................................................................................................. 3-13 3.24. Example of choke manifold........................................................................................................................................... 3-14 3.25. Gas buster........................................................................................................................................................................ 3-16 3.26. West Texas separator..................................................................................................................................................... 3-16 3.27. Cutaway of West Texas type open separator........................................................................................................... 3-16 3.28. Closed surface separation system...............................................................................................................................3-17 3.29. Schematic of closed separator......................................................................................................................................3-17 3.30. Closed vertical separator for marine use................................................................................................................. 3-18 3.31. The standpipe has valves to direct the flow of mud and gas through it............................................................. 3-19

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4.1. Bit float................................................................................................................................................................................ 4-1 4.2. String float.......................................................................................................................................................................... 4-2 4.3. Weatherford/Techcorp retrievable drill pipe float valve.......................................................................................... 4-2 4.4. Pump-down check valve.................................................................................................................................................. 4-3 4.5. Lower kelly cock............................................................................................................................................................... 4-3 4.6. Techcorp deployment valve............................................................................................................................................ 4-4 4.7. Using underbalanced drilling deployment valve to trip in....................................................................................... 4-4 4.8. Using underbalanced drilling deployment valve to trip out.................................................................................... 4-5 4.9. Halliburton downhole preventer valve........................................................................................................................ 4-5 4.10. Mechanical snubbing unit................................................................................................................................................. 4-6 4.11. Hydraulic snubbing unit................................................................................................................................................... 4-7 4.12. Tesco PPM (push-pull machine) floor-mounted portable snubbing unit.............................................................. 4-8 4.13. Cross section of drilling motor..................................................................................................................................... 4-8 4.14. Lobe patterns for power section.................................................................................................................................. 4-9 4.15. Pump pressure with motor drilling............................................................................................................................... 4-9 4.16. Hammer drill.................................................................................................................................................................... 4-11 4.17. Hammer bits.................................................................................................................................................................... 4-11 4.18. Jet sub................................................................................................................................................................................ 4-12 4.19. Parasite string.................................................................................................................................................................. 4-12 4.20. Dual casing strings.......................................................................................................................................................... 4-12 4.21. Measurement while drilling (MWD) system............................................................................................................. 4-13 4.22. MWD pulses.................................................................................................................................................................... 4-14 4.23. Steering tool run on wireline....................................................................................................................................... 4-14 4.24. Electromagnetic MWD tool......................................................................................................................................... 4-15

5.1. 5.2. 5.3. 5.4. 5.5. 5.6. 5.7. 5.8. 5.9. 5.10. 5.11. 5.12. 5.13. 5.14. 5.15. 5.16. 5.17.

Portable air compressors appeared about 1954 working out of Grand Junction, Colorado......................... 5-1 Modern air compressors usually use a rotary compressor for the first stage, called the primary compressor, and a piston compressor as the booster stages................................................................................ 5-1 Compressor hazards include high noise levels, hot temperatures, and high pressures.................................... 5-2 Refrigerated tank trucks deliver cryogenic nitrogen to a rig site......................................................................... 5-3 Cryogenic nitrogen pumping equipment includes a pump and a vaporizer, which pressurizes and warms liquid nitrogen to gas for injection into the well......................................................................................... 5-4 Membrane nitrogen-producing unit first used in 1996........................................................................................... 5-4 Large and modern membrane nitrogen generation unit......................................................................................... 5-5 Weatherford membrane nitrogen generator............................................................................................................ 5-5 Hollow gas separation fibers (membranes) pass through the eye of a needle.................................................. 5-5 Feed air, which is composed of nitrogen, oxygen, and water vapor, goes into one end of the hollow membrane fiber................................................................................................................................................................. 5-6 A compressor sends air into the membrane system and a booster compressor further raises nitrogen pressure for the rig to use............................................................................................................................................. 5-6 Where available, natural gas is good to use in air-gas drilling................................................................................ 5-7 An auxiliary gas line tied into the main pipeline to supply gas to the rig; although not shown, a gas meter is usually added to measure the gas going to the rig................................................................................... 5-7 Typical natural gas drilling hookup; the line in the foreground is downstream from the separator and goes to the rig through a meter and pressure regulator......................................................................................... 5-7 The operator of the Crossfield project in Canada recycled 80 percent of the gas used in this drilling project................................................................................................................................................................................. 5-8 Exhaust gas unit................................................................................................................................................................ 5-8 Exhaust gas nitrogen generator.................................................................................................................................... 5-9



Gas and liquid exit the blooey line on a UBD rig..................................................................................................... In UBD, gas displaces mud from the hole and reduces hydrostatic pressure..................................................... As gas bubbles go up the hole, they get larger because pressure is less near the surface.............................. Four types of fluid flow.................................................................................................................................................. Flow patterns in a gas-liquid mixture change with increasing velocity.................................................................

6.1. 6.2. 6.3. 6.4. 6.5.

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6-1 6-1 6-1 6-2 6-2

6.6. 6.7. 6.8. 6.9. 6.10. 6.11. 6.12. 6.13.

Increasing pressure on gas causes its volume to decrease..................................................................................... 6-3 A gas bubble expands in the wellbore as it moves toward the surface............................................................... 6-3 Graph of bottomhole pressure plotted against gas volume increase; as gas volume increases, bottomhole pressure decreases until critical pressure is reached....................................................................... 6-4 Lag time depends on (1) the pump rate, (2) the volume of gas in the hole, (3) the choke size, and (4) the pressure in the hole........................................................................................................................................... 6-4 Lag times can vary from 20 seconds to 1 hour, depending on hole depth and the fluid in the hole............ 6-5 In a pipe-heavy situation (A), pipe can be stripped into or out of the hole; in a pipe-light situation (B), pipe must be snubbed into or out of the hole.......................................................................................................... 6-6 Mud caps can control bottomhole pressure on trips and help control lost returns........................................ 6-6 To strip pipe with a mud cap (which exerts extra weight to control the reservoir), displace clear fluid opposite the reservoir, displace the volume of drill pipe pulled from hole through the fill-up line, and be sure not to overdisplace, which forces mud back into the reservoir................................................................... 6-8

7.1. 7.2. 7.3. 7.4. 7.5. 7.6. 7.7. 7.8. 7.9.

In flow drilling, the hydrostatic pressure of the mud is lower than formation pressure; consequently, formation fluids flow into the wellbore...................................................................................................................... 7-1 Range of bottomhole pressures created in a 10,000-ft (3,000-m) well by drilling fluids of various densities............................................................................................................................................................................. 7-2 Geopressured shale sloughs into the hole and salt flows into the hole if drilled underbalanced................. 7-3 When gas-cut mud enters the wellbore, no significant bottomhole pressure reduction occurs; further, no pit gain occurs and pump pressure is not reduced............................................................................................ 7-3 Reducing the size of the choke opening increases bottomhole pressure........................................................... 7-4 When drilling with total lost returns, use low pump pressure to pump drilling fluid down the annulus to clear cuttings and prevent stuck pipe.......................................................................................................................... 7-5 A floating mud cap increases bottomhole pressure during lost circulation....................................................... 7-6 Basic equipment required for flow drilling................................................................................................................. 7-6 In liquid, or flow, drilling, formation pressure is greater than hydrostatic pressure, so fluid flows to the surface................................................................................................................................................................................. 7-7

8.1. When gas is injected into the well, it displaces mud from the hole, and lightens the hydrostatic column................................................................................................................................................................................ 8-1 8.2. At least a 10-to-1 ratio of gas to mud must be used for a gaseated system to be effective.......................... 8-2 8.3. Gaseated mud reduces bottomhole pressure to avoid lost circulation............................................................... 8-2 8.4. (A) When the hydrostatic pressure of the mud is greater than formation pressure, formation damage can occur. (B) Injected gas reduces hydrostatic pressure and eliminates formation damage........................ 8-3 8.5. When hydrostatic pressure is higher than formation pressure, filtrate flows into the formation and leaves a filter cake in which the pipe can get stuck.................................................................................................. 8-3 8.6. A plot of drilling rate vs. bottomhole pressure shows that the drilling rate increases as hydrostatic pressure in the borehole decreases until the bit flounders (becomes unable to drill) because the system is no longer capable of removing cuttings.................................................................................................................. 8-4 8.7. In gaseated liquids, surging, or heading, is caused by the gas and liquid separating........................................... 8-4 8.8. Basic equipment required for gaseated drilling......................................................................................................... 8-5 8.9. A jet sub is a common drill pipe sub into which a housing for a bit jet has been placed................................ 8-6 8.10. A parasite string is a string of 1!/2- to 2#/8-in. (38.1- to 60.3-mm) tubing, which is banded, or strapped, to the outside of the surface casing............................................................................................................................. 8-7 8.11. A dual casing setup consists of streamlined casing temporarily run inside the intermediate casing string..8-8 8.12. To unload the hole with drill pipe injection, inject gas down the drill pipe and follow it with mud and gas................................................................................................................................................................................ 8-9 8.13. The standpipe (drill pipe) gauge reflects bottomhole pressure changes............................................................. 8-9

9.1. 9.2. 9.3. 9.4. 9.5.

Foam consists of bubbles that are surrounded by a liquid film............................................................................. Average minimum densities for water, gaseated water, and foam......................................................................... Foam ratios typically have a foam-to-water ratio of 100 to 1 or 200 to 1......................................................... Foam carries cuttings up the hole with lower slip velocities than water or mud............................................. Foam avoids lost circulation because it reduces bottomhole pressure...............................................................

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9-1 9-2 9-2 9-2 9-4

9.6. 9.7. 9.8. 9.9. 9.10. 9.11. 9.12.

Foam limits reservoir damage because flow is from the reservoir to the wellbore........................................ 9-4 If wellbore pressure is higher than formation pressure, the bubbles in the foam block formation permeability without damaging it................................................................................................................................. 9-5 When drilling underbalanced with foam, no filter cake exists and formation pressure is higher than wellbore pressure............................................................................................................................................................. 9-5 As pressure is reduced up the hole, the gas in the foam expands, which changes the foam’s quality............ 9-6 To prevent mist from forming, increase choke pressure on the well to keep the foam quality at about 90 percent.......................................................................................................................................................................... 9-7 Basic equipment for foam drilling................................................................................................................................. 9-7 One system for recycling foam includes regular rig equipment to which is added a system for adding acid and lime to recover the foam............................................................................................................................. 9-12

10.1. When drilling with air or gas, the cuttings explode from under the bit, which increases the rate of penetration...................................................................................................................................................................... 10-1 10.2. When drilling with air or gas, no skin damage occurs because flow is from the reservoir to the wellbore............................................................................................................................................................................ 10-2 10.3. When water enters an air- or gas-drilled hole, it can destabilize shale, causing it to slough into the hole; cause mud rings to form, which clog the hole; and cause cuttings to ball up around the bit and impede drilling................................................................................................................................................................. 10-2 10.4. Downhole fires can occur when drilling with air and a flammable substance is present, such as diesel oil or coal......................................................................................................................................................................... 10-3 10.5. Downhole fires can ruin downhole tools as shown here; further, the ruined equipment usually makes it necessary to plug and sidetrack the hole............................................................................................................. 10-3 10.6. Drill collars, drill pipe, and turbulence in the hole break down the drilled cuttings to dust........................ 10-3 10.7. In the horizontal section of an air- or gas-drilled hole, the cuttings can form dunes when the velocity of the air or gas is not great enough to carry them out of the hole................................................................. 10-4 10.8. Angel’s graph showing circulation rate vs. depth and air volume requirements.............................................. 10-4 10.9. Cryogenic nitrogen is delivered to the rig on mobile units................................................................................. 10-6 10.10. A skid-mounted membrane nitrogen unit at the rig site...................................................................................... 10-6 10.11. A trailer mounted compressor of the 1950s.......................................................................................................... 10-6 10.12. Modern air compressors usually use a rotary compressor for the first stage, called the primary compressor and a piston compressor as the booster stages.............................................................................. 10-6 10.13. Compressor hazards include high noise, heat, and pressure................................................................................ 10-7 10.14. (A) Air hammer and (B) hammer bit.......................................................................................................................... 10-7 10.15. Many types of bit are available for use with air hammers..................................................................................... 10-8 10.16. A plot of bit diameter vs. bit weight shows that large bits require more weight than small bits................ 10-8 10.17. (A) Fire float in normal position (B) Fire float shut................................................................................................ 10-9 10.18. (A) Fire stop open and (B) fire stop shut.................................................................................................................. 10-9 10.19. Gas and cuttings exiting a blooey line. Note the gas flare.................................................................................. 10-10 10.20. Two ways to anchor a blooey line........................................................................................................................... 10-10 10.21. Blooey line jet............................................................................................................................................................... 10-10 10.22. A simple cuttings catcher can be installed in the blooey line............................................................................ 10-11 12.1. 12.2. 12.3. 12.4. 12.5. 12.6. 12.7. 12.8.

Two examples of water that contain substances that cause corrosion: the bucket at left contains produced water with black acid in it......................................................................................................................... Rust on the pipe is often the first indication of oxygen corrosion..................................................................... Severely pitted and corroded pipe............................................................................................................................. Oxygen corrosion rusted the pipe and created broad pits.................................................................................. Oxygen corrosion on this tubing is so bad that it is unusable............................................................................ Tubing with slight oxygen corrosion.......................................................................................................................... This tubing was pulled from a well that was properly treated to prevent corrosion.................................... This tubing was in the lower 1,000 ft (300 m) of a 10,000-ft (3,000-m) well and is coated with a soft iron oxide layer that resembles barnacles................................................................................................................

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12-2 12-2 12-3 12-3 12-3 12-3 12-3 12-4

12.9. Carbon dioxide corrosion........................................................................................................................................... 12.10. CO2 corrosion on the box end of a joint of tubing............................................................................................... 12.11. Elongated pits on the surface of this pipe are characteristic of CO2 corrosion............................................. 12.12. Deep pits are characteristic of H2S corrosion......................................................................................................... 12.13. Stress cracking caused by H2S.....................................................................................................................................

12-4 12-4 12-4 12-5 12-5

13.1. A standpipe manifold rigged for UBD features valves to direct flow of air-gas and mud to the kelly (or top drive) or to the blooey line........................................................................................................................... 13-3 14.1. 14.2. 14.3. 14.4. 14.5. 14.6. 14.7. 14.8.

A flare from a vertical flare stack disposes of combustible gas from a well..................................................... This flare is an excavated earthen burn pit.............................................................................................................. Two ways to restrain a horizontal flare line include chained cross pieces that are driven into the ground and an elevated saddle in which the line is chained; a heavy block weight anchors the saddle and line............................................................................................................................................................................. A cut-off 55-gal drum filled with concrete anchors the 3-in. (75-mm) flare line on this workover rig..... A normal flare is depicted in the center drawing................................................................................................... A smoky flare indicates that not enough air is available to burn all the components coming from the flare line............................................................................................................................................................................ A free-water knockout allows water droplets to settle from the gas before it enters the flare line......... A separator-and-flare-line unit ready to be transported to the rig...................................................................

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14-1 14-2

14-2 14-3 14-4 14-4 14-5 14-5

Tables 1.1. Pressure Calculations....................................................................................................................................................... 1-4 1.2. Mud Weights and Gradients........................................................................................................................................... 1-5 1.3. UBD Classification Matrix.............................................................................................................................................. 1-7 6.1. Floating Mud Colum Calculation................................................................................................................................... 6-7 11.1. Effect of Well-Control and UBD Problems on Pressures, Weight, Pit Level, and Pump Rate........................ 11-1

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