1. Introduction to Underbalanced Drilling Technology(M2)
Start by asking audience if their companies have drilled UBD. Positive responders will be low. Most will not know what UBD is. No point talking about DEA-101 project, then. Therefore start with short intro on UBD.
This is a general introduction to Underbalanced Drilling Technology. Almost everything discussed here will be covered again in a later module.

2. Wellsite UBD Equipment
Nitrogen
UB operators
Geology
Separator
Rotating Head
Camp
Largel UB location, Canada in summer. Location needs room for the gas
source, nitrogen source if used, separators, mud tanks and solids control
and office space for data So UB locations generally need a little more space
than normal mud jobs.
Mud Treatment

3. UB DRILLING - JOBS ©1998 Spears & Assoc.
This is a 1958 view of the ub job description. Now Canada and US are
about the same in UB, with Canada perhaps slightly ahead. Columbia and
Venezuela now have a larger percentage as does the N. Sea. China and SE
Asia are also increasing.
©1998 Spears & Assoc.

4. UBD - Types Normally Pressured Reservoirs
Applications for normal to above normal pressured reservoirs utilizing fluid systems in a controlled flow (mudcap) drilling technique.
Depleted Reservoirs
Where a multi-phase circulating fluid is necessary to achieve required Bottom Hole Circulating Pressure (BHCP) - underbalanced or with minimal overbalance.
Notes: This is an oversimplification. More work is being done near or at balance in normal and overpressured formations

5. Barriers to UB Drilling
There are a number of barriers to UB Drilling. The main one is phsycological
resistance to a new idea after all these years of well control discussions.
Well control is based on being overbalanced

6. REGULATORY BARRIERS to UnderBalance Drilling
The regulators need assurance and details
The regulators need assurance. Their interest is not to make a mistake,
not gamble on new techniques.

7. BARRIERS TO UB D&C Regulatory Lack of Standards Lack of knowledge
Little statistical history
Concern about well control
Environmental questions
This is about it. The regulator needs protection against criticism. He has
a Civil Service

8. OPERATORS BARRIERS The Operator needs experience and confidence.
In our new economy, the operators engineering group are not a gamblers

9. Unfamiliar with the system Lack of experienced people
OPERATORS PROBLEMS
Unfamiliar with the system
risk of the new
Lack of experienced people
Economics - Too expensive
Concern- liability
Concern- well bore stability
Pretty straight forward.

10. REASONS FOR UB GROWTH There are driving economic reasons
Straight forward

11. Awareness of skin damage Limits of lost circulation matl.
REASONS FOR UB GROWTH
Depleted reservoirs
Awareness of skin damage
Limits of lost circulation matl.
Cost of differential sticking
These are reasons for growth, not necessarily local reasons which tend to
have more to do with lost circulation

12. Service co. competition Trade journal publications Horizontal drilling
REASONS FOR UB GROWTH
Service co. competition
Trade journal publications
Horizontal drilling
Consultants available
This page shows the big driving forces. Competition among the service
companies and their sales efforts.

13. TECHNICAL IMPROVEMENTS
We were not ready to put all of this together until the 1990’s
UB drilling was tried as far back as we have records. The move to rotary rigs
from cable tools slowed it down, but people have always been trying.

14. TECHNICAL IMPROVEMENTS
Compressor Evolution
Hammer drills
Nitrogen
Increased availability
Reduced cost
On site generation
The compressors before 1965 were pretty poor.
The same is true for hammer drills before 1985
Nitrogen on site generation started in 1991

15. TECHNICAL IMPROVEMENTS
Recyclable foam systems
Better gas separators
Closed loop circulation
Hydraulics models
Improved rotating heads
Wire line wet connect
All of this started to be available in 1990 to 1995., and the technology is
still improving.

16. TECHNICAL IMPROVEMENTS
Improved MWD
Rig assist snubbing units
Coiled tubing equipment
Non-damaging drilling fluids
Top drive
This continues the items that have become practical and available since
1995 and 1996

17. Expandable sand screens Retractable bit
WORKING ON
Well Control Concepts
Deployment valves
Casing Drilling
Expandable casing
Expandable sand screens
Retractable bit
In 2000, all of these are in the development or field testing stage.

18. COMPLETION TECHNIQUES
Improved gravel packing fluids
Improved completion fluids
General technique improvement
Completion techniques for UB drilling operations are starting to come of age
in 2000, and we should continue to see real efforts to complete at balance or
underbalance without killing the well.

19. Reasons for UB drilling
Lost circulation
Lost circulation has been and is still the primary driver for ub drilling.

20. Reasons for UB drilling
Lost circulation
Faster Drilling
Increase drilling rate is the primary driver for air drilling and is becoming more
recognized in other UB applications.

21. Reasons for UB drilling
Lost circulation
Faster Drilling
No Differential Sticking
Differential sticking is a primary UB driver in horizontal wells.

22. Reasons for UB drilling
...
Reduce Reservoir Damage
Reduced reservoir damage is a primary issue in Canada and is becoming
recognized in Venezuela. However it is still more talk than actual because
of the problem of completions.

23. Reasons for UB drilling
...
Reduce Reservoir Damage
Improve Prod. Evaluation
This is a technical selling point, but not used as much as it could.
One of “next years” projects.

24. Effect of Skin on Production Rates
BOPD
1,000
800
600
400
Skin damage is a measure of production reduction from the “original condition”
In all reservoirs, we are just starting to try to reduce skin damage when drilling
instead of using enhancement techniques. Skin damage is the inverse of return permeability.
200 -3 -2 -1 5 10 15
SKIN

25. Physical Limitation to UBD
Borehole Instability
Unconsolidated Sands
Weak Formations
Geopressured Shales
Salt Beds
Inadequate Casing
Bore hole instability:
Unconsolidated sands - but we are now finding foams work well
Weak formations - this is more a matter of broken dipping formations, but again new foam techniques are helping
Geopressure shale beds- just cannot be drilled UBSalt - is a plastic and needs to be drilled over balance
Casing needs to take this and the productive zone into account
UBD is another tool in the toolbox,
not a Panacea.

26. Production Limits to UBD
Permeability is so low the zone needs to be fraced.
Zones must be isolated
Now we are sort of guessing. There are obvious limits that probably look
like this, but there is little good published data.

27. Types of Flow Regimes AERATED LIQUID FOAM MIST GAS LIQUID
Five forms of liquid for UB drilling. Actually all of these grade into each other
at some point due to compression of gas. The flow patterns and lifiting
capacity will change with gas percent and fluid properties such a viscosity
and foamers.
AERATED
LIQUID
FOAM
MIST
GAS
LIQUID

28. Fluid Phase Continuity
AIR/GAS
WATER
Aerated muds and foam have fluid as the continuous phase. When gas is
the continuous phase, lifting capability become the main problem.
FOAM
MIST
(0-97% AIR)
(97-100% AIR)

29. Generalized “Fluid” Systems
Actually everything from areated fluid to air/mist tends to overlap in the area
between 0.8 and 0.2 spg. There are very few hard limits

30. CONTROL EQUIPMENT
Basic control equipment

31. Equipment - Rotating Head
Notes There are at least ten companies that build rotating heads or rotating blow out preventers, and at least three distinct types.
Shaffer Rotating Blow-Out Preventor
2,500 psi rotating - 5,000 psi static

32. Closed Loop Circulation System
FLARESTACK
SEPARATOR
SAMPLE
CATCHERS
TOP
OIL
DRIVE
TANKS
NITROGEN
SYSTEM
PUMPERS
CHOKE
MANIFOLD
R-BOP
WATER
The closed loop circulating system was developed in Canada first by
Northland Production Testing to control H2S has and other gasses
produced from an under balanced well.. There are now probably 10 or 12
companies that have closed systems.
TANKS
RETURN
RIG
CUTTING
MUD
RIG
PUMPS
TANKS
N2 / FLUID
MIX

33. Choke Manifold
Flexible flow manifolds with hydraulic chokes have been in the oil field
since the 1970’s

34. Equipment - Lots More To shale shaker ESD Manifold Sample catchers
Willis choke
Flare
Separator
200 psi vessel
Rig Manifold
There is more new equipment technology, and it it will be covered during
the next few days.l
Choke
Oil storage/transport
Water returned to tanks
HCR
Flare pit
Choke

35. AIR DRILLING A brief summary

36. Air Drilling
Air/Gas drilling (“dust”) is a technique used in areas where the formations are “Dry” i.e., there is no influx of water or liquid hydrocarbons.
This medium requires significant compressed gas volumes to clean the well with average velocities of over 3,000 ft per minute.

37. Air Drilling Dusting
Do not know the source of the picture

38. Air Drilling Benefits Increased Rate of Penetration
Reduced Formation Damage
Improves Bit Performance
Lost Circulation Control
Continuous Drill Stem Test

39. Air/Dust Drilling Layout
Note kelley bypasses to the blooie line

40. Air Drilling Waited upon Large Portable Compression
Simple and convenient to drill with air inexpensively and anywhere.

41. Misting
Addition of 6 to 30 bbl/hr of fluid to the air stream.
Clean and lubricates the bit
Carries the cuttings to the surface as a mist or more normally in a modified two phase flow.

42. FOAM DRILLING Basic Comments
Basic comments on the process
TT96-86

43. Foam Drilling The most versatile of the gas-generated systems.
Effective operating range from 0.2 to 0.6 s.g.
Mixture of gas phase and foaming solution.
Foam flow varies with depth in the hole.
Adjustable effective BHP.
Enhanced lifting and well bore cleaning.
A “displacing medium”, not a propelling medium.
Foam is the fluid of the future because it can be controlled and modified to fit
the needs of the job. The major weakness of foam jobs is with large oil flows
which tend to flatten the foam.

44. Foam (Heading)
Foam will head if improperly handled. Good procedures would not let this
happen

45. Improved Hole Cleaning
This is how a foam system should look

46. Foam Drilling Benefits
Faster Penetration rate
Low Air requirements
Low fluid requirements
Low Hydrostatic head
No damage to formation
Continuous Drill Stem test
Best for large holes
Gas and fluid rates are less than half of gaseated systems and 1/4 to 1/10th
of gas volumes needed for gas drilling.
Foam is most economically favorable for large shallow holes, but works well
in deep small holes.

47. Mist or Foam Drilling Layout
Best procedures for the foam additions are to use metering pumps.
The control of the injection pump is very important and it is difficult to get
stable pressure with foam using the rig pumps.

49. GASEATED OR AERATED DRILLING
Next to the cable tool and possibly gas drilling, aerated mud is the oldest
way of reducing mud weight for lost circulation. Records show gaseated mud
used the the Sour Lake Field in South East Texas in 1938.

50. Mist Water Transition Gas Gaseated
In a gaseated or aerated system, the gas is injected into the system. The gas
is compressed at the bottom of the hole and expands as it goes up. It may
change the phase and convert into a mist if there is enough air and it is
allowed to expand. The only thing that holds the gas to the mud is mud
viscosity, the upward velocity of the mud and gas, and the size of the bubbles
. The gaseated system is a mixture that will separate into gas and fluid..

51. Aerated Fluid Gasification of Primary Drilling Fluid.
Initially designed as a technique to lighten mud to reduce lost circulation.
Methods
Standpipe injection
Jet Sub
Parasite String
Dual Casing String
As an UB fluid, it is easiest to control in small holes.
Gaseated fluids work best as a means of preventing lost circulation.

52. Parasite String Small injection string run simultaneously
with intermediate casing.
Injected gas does not affect
bit hydraulics.
• Injected gas does not effect
MWD
The parasite string is an old method of solving the problem of pressure
surges in gaseated systems while making connections and starting again
after trips.

53. Jet Sub Similar to Parasite String Gas induced thru drill pipe
Selective jet sizing dictates amount of air to be injected
Jets are Similar to Bit Jets
The jet sub is the commenest method in use today because it requires
Minimal special equipment.

54. Parallel Casing String (Teichrob)
N /air 2
N /water 2
N /air/water/oil 2
150 m TVD, 150 m MD
89-mm (3-1/2 in.) Drill Pipe
244.5-mm (9-5/8 in.) Intermidiate Casing o
177.8-mm (7 in.) Tie Back Liner
724 m MD at
64 inclination
Parallel casing strings or a slim string is an idea that came out of Canada o
159-mm (6-1/4 in.)
Hole Diameter
12 m Slotted
Joint
892 m MD
at 90 Inclination
694 m TVD o
Foam Cement o
TD = 1,440 m MD at 90
Inclination, 696 m TVD o

55. Aerated Fluid Layout

56. Aerated Drilling Problems
Rotating BOP’s
Compressor/N2
Cost
Solid/Liquid/Gas
Separation
Corrosion
Hydraulic Calculations
Vibration
Cuttings Lifting
Fluid Influx
Fire/
Explosions
Underbalanced
Completion
High Torque/
Drag
Borehole Stability
MWD Transmission

57. UB Drilling & Completions Manual
Candidate Selection
Air/Gas/N2/Mist Drilling
Foam Drilling
Aerated Fluid Drilling
Flow “Live” Drilling
Surface Equipment
Downhole Equipment
Field Operations
Downhole Problems
Environment, Safety, Reg.

58. END OF INTRODUCTION