A GUIDELINE TO BEST PRACTICES FOR EFFICIENT HOLE CLEANING IN DIRECTIONAL WELLS

1. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
1

2. TWO PRIMARY ACTIVITIES ASSOCIATED
WITH DRILLING A WELL
 1. PENETRATING SUBTERRANEAN
FORMATIONS WITH THE DRILL BIT.
 2. REMOVING THE DRILLED
MATERIAL FROM THE HOLE THUS
DRILLED

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
2

3. THIS LATTER PROCESS WHICH WE CALL HOLE
CLEANING DOES NOT GET THE ATTENTION IT
DESERVES
 WE MERELY ASSUME THAT THE ACT OF
CIRCULATING DRILLING MUD UP AND DOWN
THE HOLE CAN TAKE CARE OF THIS ACTIVITY.
 THIS MAY SOMETIMES BE TRUE IN VERTICAL
WELLS BUT IT IS SELDOM THE CASE IN
DRILLING HIGH ANGLE DEVIATION WELLS

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
3

4. IN THESE HIGH ANGLE DEVIATED WELLS
THE CUTTINGS FOLLOW A COMPLEX AND
TORTUROUS PATH TO THE SURFACE IN
WHICH
SOME
OF
THE
CUTTINGS
GRAVITATE TO THE LOW SIDE OF THE
HOLE.
 FAILURE TO CLEAN THESE CUTTINGS OUT
OF THE BOREHOLE LEADS TO MANY
SERIOUS PROBLEMS WE ENCOUNTER IN
THESE WELLS.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
4

5. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
5

6. THE RATIO OF THE RATE AT WHICH THE CUTTINGS ARE
REMOVED FROM THE HOLE TO THE RATE AT WHICH THEY
ARE GENERATED AT THE BIT IS THE HOLE CLEANING RATIO.
IDEALLY WE WOULD LIKE THIS TO BE = 1.
BUT IT WOULD BE A COINCIDENCE IF THIS WERE TO
ACTUALLY HAPPEN – YOU HAVE TO BE LUCKY TO GET THIS
IDEAL SCENARIO.
NORMALLY THE RATE OF CUTTING REMOVAL LAGS THE
RATE OF CUTTING GENERATION
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
6

7. THIS LAGGING BEHIND LEADS TO
ACCUMULATION OF SOME CUTTINGS IN
THE HOLE.
 SO LONG AS THIS ACCUMULATION DOES
NOT HAMPER NORMAL OPERATIONS YOU
CAN TOLERATE IT.
BUT WHEN THIS
ACCUMULATION STARTS HAMPERING OUR
NORMAL OPERATIONS WE ARE IN
TROUBLE.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
7

8. CUTTINGS
CAN
BE
DEGRADED
CHEMICALLY AND PHYSICALLY WHILE
STILL IN THE ANNULUS.
 DEGRADATION/DISPERSION
OF
THE
CUTTING IN THE ANNULUS MUD STREAM
DECREASES THE SIZE OF THE CUTTINGS
LEADING TO AN IMPROVEMENT IN THE
HOLE CLEANING EFFICIENCY

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
8

9. DISPERSION OF CUTTINGS INTO THE MUD STREAM
CAN HAVE SERIOUS UNDESIRABLE EFFECTS ON THE
PROPERTIES OF THE MUD.
SOBMs DO NOT ALLOW THE CUTTINGS TO DISPERSE
IN THE MUD OR DEGRADE IN THE MUD AND HENCE
THEIR HOLE CLEANING EFFICIENCIES ARE LESS AS
COMPARED TO WATER BASED MUDS WHICH AID
DISPERSION OF CUTTINGS.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
9

10. SMALL VOLUME OF CUTTINGS AT THE SHAKER AS COMPARED TO THE
VOLUME OF THE HOLE DRILLED.
LARGE AMOUNT OF FILL AFTER TRIPS
INCREASING DRAG
INCREASING TORQUE
REGROUND (SMALL AND ROUNDED) CUTTINGS
INCREASED ECD AS MEASURED BY THE PWD TOOL
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
10

11. LOST CIRCULATION DUE TO PACK OFF OR HIGH ECD
STUCK PIPE
HIGH TORQUE AND DRAG
DIFFICULTIES IN RUNNING AND CEMENTING CASING
DIFFICULTY IN GETTING THE LOGGING TOOLS TO THE REQUIRED
DEPTH
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
11

12. HOLE SIZE
HOLE ANGLE
ROP
FLOW RATE
DRILLING FLUID PROPERTIES
PIPE ROTATION
CUTTINGS SIZE AND SHAPE
MINERALOGY OF THE CUTTINGS
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
12

13. THE BEHAVIOR OF CUTTINGS IN THE WELL
BORE IS LARGELY DEPENDENT ON THE
ANGLE OF INCLINATION OF THE WELL
BORE
 WE CAN CLASSIFY WELL BORES INTO
THREE TYPES

› STRAIGHT OR NEAR STRAIGHT
› HIGH ANGLE HOLES
› EXTREMELY HIGH ANGLE HOLES
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
0 - 300
30 - 650
65 - 900
13

14. 
DRILL CUTTINGS EXHIBIT DISTINCTLY
DIFFERENT BEHAVIOR IN EACH OF THESE
HOLE TYPES

EACH WELL TYPE REQUIRES DIFFERENT
CONSIDERATIONS WITH RESPECT TO
EFFICIENT HOLE CLEANING.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
14

15. THE MOTION OF
THE CUTTINGS IS
THE STRAIGHT HOLE
IS LARGELY
DOWNWARD WHEN
THERE IS NO
CIRCULATION AND
UPWARD WITH
CIRCULATION
15

16. THE VECTOR OF THE DOWNWARD MOTION IS
CONTROLLED BY THE FORCE OF GRAVITY AND
IS INFLUENCED BY:
• BUOYANCY
• VISCOSITY OF THE DRILLING FLUID
• SIZE OF THE PARTICLE
THE UPWARD MOTION OF THE PARTICLE IS
GOVERNED BY ALL OF THESE AND BY THE
VELOCITY OF THE DRILLING FLUID.
THE MATTER OF HOLE CLEANING IS A MATTER
OF SUFFICIENT CIRCULATION OF THE
WELLBORE
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
16

17. LIFE BECOMES SLIGHTLY COMPLEX HERE DUE TO THE
TENDENCY OF THE CUTTINGS TO SETTLE ON THE LOW SIDE OF
THE HOLE EVEN WHEN MOVING UP DUE TO CIRCULATION OF
THE MUD.
THE AVALANCHING OF THE
CUTTINGS IN THESE HOLES
MAKES THEM THE MOST
DIFFICULT TO CLEAN.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
17

18. CUTTINGS TEND TO SETTLE ON THE LOW SIDE OF THE
HOLE BUT WHEN CIRCULATION IS STOPPED
THE CUTTING DO NOT
AVALANCHE DOWN THE
WELLBORE WHEN
CIRCULATION IS STOPPED
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
18

19. ANNULAR VELOCITY


HIGHER THE BETTER IS A GOOD RULE OF
THUMB PROVIDED THE FORMATIONS ARE
COMPETENT
IN STRAIGHT HOLES MUD VISCOSITY AND
ANNULAR VELOCITY ARE THE ONLY
CONSIDERATIONS.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
19

20. 
FOR HIGH ANGLE AND EXTREME HIGH
ANGLE WELLS IT IS NECESSARY TO
OPTIMIZE THE ANNULAR VELOCITY WITH
THE HIGHEST PRACTICAL FLOW RATE

BUT THIS FACTOR WILL NOT OBTAIN
ADEQUATE HOLE CLEANING.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
20

21. RECOMMENDED MINIMUM FLOW RATES
AND ANNULAR VELOCITIES
HOLE SIZE INCHES
FLOW RATE
GPM
ANNULAR VELOCITY
FT/MIN
17 1/2
900 – 1200
76 – 100
12 1/4
700 – 1000
133 – 190
9 7/8
600 – 850
197 – 279
8 1/2
400 - 600
202 - 303
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
21

22. HOLE SIZE IS A MAJOR FACTOR IN HOLE CLEANING. ANNULAR VELOCITY
OF 140 FT/MIN OR MORE IS HIGHLY DESIRABLE IN HIGH ANGLE WELLS BUT
THESE RATES CAN BE ACHIEVED ONLY IN SMALLER HOLES
HOLE
SIZE
17 ½
AND
LARGER
14 ¾
AND 12
¼
9
CHARACTERISTICS
EXTREMELY DIFFICULT TO CLEAN. PROBLEM COMPOUNDED BY
USE OF SOBMs. LUCKILY WE DON’T USE SOBMs IN THESE
SECTIONS. ALL AVAILABLE TOOLS AT HAND MUST BE BROUGHT
INTO PLAY TO CLEAN THE HIGH ANGLE WELLS OF THIS SIZE
HOLE CLEANING REMAINS A PROBLEM IN THESE HOLE SIZES
TOO. SOBMs ARE FREQUENTYLY USED IN THESE SECTIONS
COMPOUNDING HOLE CLEANING PROBLEMS.
HOLE CLEANING BECOMES EASIER IN THESE SECTIONS IF GOOD
7/8 PRACTICES ARE FOLLOWED.
22
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

23. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
23

24. 
THE DRILL PIPES AND CUTTINGS LIE ON THE
LOW SIDE OF THE HOLE.

THE AREA OF THE HIGHEST FLUID VELOCITY
TENDS TO BE AT THE HIGH SIDE OF THE
HOLE WHILE THE LOW SIDE CONTAINS AN
AREA OF LOW FLOW RATE THAT IS
EFFECTIVELY A DEAD ZONE
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
24

25. THIS TYPE OF FLOW PROFILE
CREATES HUGE PROBLEMS
WHEN THE CUTTINGS SETTLE
INTO A SPACE OF LITTLE OR NO
FLOW ON THE LOW SIDE OF THE
HOLE.
THE EFFECT GETS MORE
PRONOUNCED AS THE PIPE
ECCENTRICITY INCREASES
THE CLEANING DEPENDS ON
REMOVING THE CUTTING FROM
THE LOW SIDE OF THE HOLE
INTO THE AREA OF HIGH FLOW.
D/P ROTATION IS THE MOST
EFFECTIVE TOOLS FOR
ACHIEVING THIS.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
25

26. 


THE CUTTINGS MOVE UP-HOLE INTO THE
HIGH FLOW AREA UNTIL THEY ONCE MORE
SETTLE INTO THE DEAD SPACE ON THE LOW
SIDE OF THE HOLE.
THEN THEY ARE THROWN INTO THE MAIN
STREAM BY THE ROATION OF THE D/P
THIS START STOP PRACTICE CONTINUES
UNTIL THE CUTTINGS REACH THE STRAIGHT
HOLE SECTION AND ARE CIRCULATED OUT
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
26

27. 


THE CUTTINGS IN THE START-STOP MOTION ARE
ABRADED
MECHANICALLY
BY
THE
D/P
ROTATION AND BECOME SMALLER AND
ROUNDED.
THIS UP AND DOWN JOURNEY IS SLOW AND
TAKES LONGER THAN THE BOTTOMS UP TIME
EVEN WITH OPTIMUM D/P ROTATION.
WITHOUT D/P ROTATION THE CUTTINGS BED MAY
REMAIN IN PLACE WITH VERY LITTLE UPWARD
MOTION AND MAY EVEN SLIDE DOWNWARDS
WHEN CIRCULATION IS STOPPED
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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28. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
28

29. THERE IS A GREAT DIFFERENCE IN THE
CUTTINGS REMOVAL FROM 100 AND 120
RPM
 A SIMILAR CHANGE OCCURS BETWEEN
150 AND 170 RPM
 OPTIMUM PIPE ROTATION IS THE SINGLE
MOST EFFECTIVE WAY TO OBTAIN
SIGNIFICANT
INCREASES
IN
HOLE
CLEANING

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
29

30. HOLE SIZE – (INCHES)
MINIMUM PIPE ROTATION SPEED
RPM
17 1/2
120
12 1/4
120
9 7/8
120
8 1/2
80
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
30

31. INCREASING VISCOSITY TO CLEAN THE
HOLE USUALLY WORKS IN A STRAIGHT
HOLE.
 17 ½”AND 20” HOLES ARE GENERALLY
DRILLED WITH A LOW MUD WEIGHT SO
THEY CAN BE CLEANED BY INCREASING
THE VISCOSITY OF THE MUD WHERE Yp >
Pv IN ORDER TO OVERCOME THE LOW
BUOYANCY AND THE LOW ANNULAR
VELOCITY OF THE MUD.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
31

32. IN SMALLER HOLES MUD WT. AND ANNULAR
VELOCITY INCREASE AND HOLE CLEANING
IMPROVES ACCORDINGLY.
 IN SMALLER HOLES ECD IS ALSO AN
IMPORTANT FACTOR TO BE CONSIDERED IN
DETERMINING THE OPTIMUM VISCOSITY OF
STRAIGHT HOLES.
 HIGHER ANNULAR VELOCITY ALLOWS FOR
USE OF LOVER FLUID VISCOSITY WITHOUT
COMPROMISING THE CLEANING
EFFICIENCY.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
32

33. HIGH VISCOSITY DOES NOT
NECESSARILY PROMOTE IMPROVED
HOLE CLEANING IN DEVIATED HOLES.
BOTH HI VIS AND LOW VIS ARE
DETRIMENTAL TO HOLE CLEANING IN
THESE WELLS.
A RANGE OF MODERATE VISCOSITY
PROMOTES THE BEST HOLE CLEANING.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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34. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
34

35. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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36. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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37. HIGH VISCOUS SWEEPS CAN BE EFFECTIVE IN
STRAIGHT HOLES BUT THEY ARE NOT VERY HELPFUL
IN HI ANGLE HOLES.
IN FACT THEY CAN BE DETRIMENTAL TO HOLE
CLEANING IN HI ANGLE HOLES
THIS IS DUE TO THE FACT THAT HI VIS SWEEPS CAN
ENLARGE THE DEAD ZONE ON THE LOW SIDE OF
THE HOLE
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
37

38. HIGH DENSITY SWEEPS ARE VERY
EFFECTIVE IN REMOVAL OF CUTTING BEDS
AND HAVE BECOME STANDARD PRACTICE
IN THE DRILLING OF HI ANGLE HOLES.
 THEY ARE TYPICALLY WEIGHTED UP 1 TO 3
PPG (0.12 TO 0.36 SG) OVER THE BASE
MUD AND VISCOSITY IS NOT INCREASED
BEYOND
WHAT
THE
ADDITIONAL
WEIGHING MATERIAL CONTRIBUTES.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
38

39. THESE SWEEPS ARE SMALL IN VOLUME (30-50 BBL)
USUALLY 200 – 500 FT OF ANNULAR HEIGHT.
SO THE DANGER OF INCREASING THE
HYDROSTATIC HEAD OF THE MUD COLUMN AS THE
SWEEP MOVES UP THE ANNULUS IS AVOIDED.
LARGE SWEEPS ARE ALSO PROBLEMATIC WHEN THE
CUTTING BEDS ARE LARGE.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
39

40. THIS IS BECAUSE THE SWEEP CAN PICK UP ENOUGH
MATERIAL TO OVERLOAD THE ANNULUS WITH CUTTINGS
CREATING A POTENTIAL PACK OFF.
HENCE IT IS A GOOD IDEA TO USE A SMALLER HI
DENSITY SWEEP AND CIRCULATE OUT THE CUTTINGS
BEFORE GOING IN FOR ANOTHER SWEEP.
GOOD SHALE SHAKER DISCIPLINE IS REQUIRED HERE,
TO BE AWARE OF THE CUTTINGS COMING OUT BEFORE
SWEEPING THE HOLE WITH THE NEXT HI DENSITY SWEEP
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
40

41. SOMETIME BACK I HAD TALKED OF VERY
FINELY GROUND BARITE – THE WARP
WHILE WE WERE DISCUSSING BARITE SAG.
 NOW I WILL TALK ABOUT VERY COARSE
GROUND BARITE IN MAKING THESE HIGH
DENSITY SWEEPS.
 IT HAS BEEN FOUND THAT COARSE BARITE
IS MORE EFFECTIVE THAN NORMAL BARITE
THAT IS USUALLY USED IN WEIGHING UP
THE MUD.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
41

42. THE SCOURING EFFECT OF THE COARSE BARITE IS
THOUGHT TO PLAY A ROLE IN THE INCREASED EFFICIENCY
OF COARSE BARITE TO REMOVE THE CUTTING BEDS.
“SWEEP WATE” IS A PATENTED PRODUCT BY BAROID
WHICH IS EMPLOYED IN MAKING THESE HIGH DENSITY
SWEEPS.
COARSE NUT HULLS ARE ALSO EMPLOYED IN THE
PREPARATION OF HIGH DENSITY SWEEPS.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
42

43. THE OTHER ADVANTAGE OF USING
COARSE MATERIAL IS THAT THIS CAN BE
PARTIALLY REMOVED BY THE SOLIDS
CONTROL EQUIPMENT AT THE SURFACE.
 SO THE INCREASE IN THE MUD WEIGHT
DUE TO FREQUENT USE OF THESE SWEEPS IS
MINIMIZED.
 WITH
NORMAL
GROUND
BARITE
EMPLOYED FOR THE HIGH DENSITY
SWEEPS, DILUTION BECOMES NECESSARY.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
43

44. DISADVANTAGES
DILUTION
HIGH
VOLUMES
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
HIGH
COSTS
44

45. ONE SHOULD HAVE A REGULAR PROGRAM
FOR EMPLOYING THESE HIGH DENSITY SWEEPS.
FREQUENCY DEPENDS ON THE HOLE SIZE AND
ROP
TYPICALLY THESE SWEEPS ARE EMPLOYED FOR
EVERY 1-3 STANDS DRILLED.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
45

46. HIGH DENSITY SWEEPS (1-3 BBL OVER
THE BASE MUD WEIGHT)
50 – 60 BBL SWEEP
17 ½” HOLE
12 ¼ ” HOLE
8 ½ ” HOLE
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
EVERY 1-2 STANDS
30 – 40 BBL SWEEP
EVERY 1 – 3 STANDS
20 – 30 BBL SWEEP
EVERY 3 – 5 STANDS
46

47. IT IS IMPORTANT TO CIRCULATE AT DRILLING FLOW
RATE WITH OPTIMUM PIPE ROTATION DURING THE
ENTIRE TIME THE SWEEP IS IN THE HOLE.
FOR FLOATING DRILLING RIGS WITH SUB SEA
STACKS, THE SWEEP NEED ONLY BE IN THE RISER
WHEN CIRCULATION THROUGH THE DRILL STRING
STOPS. A BOOSTER PUMP CAN BE EMPLOYED TO
KEEP THE SWEEP IN THE RISER MOVING UPWARDS.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
47

48. CUTTING BEDS ARE FREQUENTLY COMPOSED
OF VERY FINE PARTICLES DUE TO THE
GRINDING EFFECT OF THE BHA AND THE DRILL
PIPE.
 CUTTING BEDS ALSO CONTAIN BARITE
WHICH HAS SAGGED TO THE LOW SIDE OF
THE HOLE IF THE WEIGHTED MUDS ARE BEING
USED.
 THESE FINE MATERIALS MAY NOT BE VISIBLE
ON THE SURFACE UNLESS VERY FINE SHALE
SHAKER MESHES (> 175 MESH) ARE
EMPLOYED.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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49. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
49

50. IN HIGH ANGLE WELLS BOTTOMS UP OF THE MUD IS
NOT THE BOTTOMS UP FOR THE CUTTINGS.
EXTENDED CIRCULATION TIMES ARE THEREFORE
NECESSARY FOR GOOD HOLE CLEANING
EFFICIENCY.
THIS HAS TO BE ACCEPTED WITHOUT RESERVATION
IN OPERATIONS ON THIS TYPE OF HOLE.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
50

51. THE HOLE SHOULD BE CIRCULATED WITH D/P
ROTATION FOR AT LEAST 10 – 15 MIN BEFORE
MAKING A CONNECTION TO MOVE THE
CUTTINGS AWAY FROM THE BHA BEFORE
CIRCULATION IS STOPPED.
 WHEN DRILLING WITH VERY HIGH ROP OR
AFTER SLIDING A KELLY LENGTH SYMPTOMS
LIKE JERKY TORQUE AND FLUCTUATING PUMP
PRESSURE ARE SURE SHOT INDICATORS THAT
EXTENDED CIRCULATION IS NEEDED TO FLUSH
THE HOLE OF EXCESSIVE CUTTINGS.

GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
51

52. THE HOLE MUST BE CIRCULATED CLEAN PRIOR
TO TRIPS AND THIS MAY TAKE AS MUCH AS 4
TIMES THE BOTTOMS UP FOR SOME HIGH ANGLE
WELLS.
HOLE TYPE
CIRCULATION TIME PRIOR TO
TRIPS
0 – 30o
1.2 TO 1.8 TIMES BOTTOMS UP
30 – 65o
2.0 TO 2.5 TIMES BOTTOMS UP
65 – 90o
2.5 TO 3.5 TIMES BOTTOMS UP
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
52

53.  IT
IS IMPORTANT TO REMEMBER THAT
THESE ARE MERE GUIDELINES FOR
GOOD HOLE CLEANING PRACTICES.
 THE HOLE WILL NEVER BE PERFECTLY
CLEAN BUT WE CAN LIVE WITH THE
FACT THAT THE HOLE IS CLEAN
ENOUGH TO TRIP WITHOUT EXCESSIVE
OVERPULL DUE TO CUTTING BEDS.
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
53

54. THE ACTUAL TIME TO ACHIEVE AN
EFFECTIVELY CLEAN HOLE WILL DEPEND ON
THE ANNULAR VELOCITY, DETAILED HOLE
GEOMETRY, SPEED OF PIPE ROTATION,
VISCOSITY, MUD WEIGHT, CUTTING
MINERALOGY, INHIBITIVE CHARACTERISTICS
OF THE MUD AND THE
COARSENESS/FINENESS OF THE WEIGHING
MATERIAL
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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55. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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56. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
56

57. HOWEVER BACK REAMING HAS BEEN FOUND
TO BE DANGEROUS IN HIGH ANGLE HOLE
WELLS.
THE OVER-PULL CONDITION IS USUALLY DUE TO THE
DRAGGING OF THE BIT AND THE BHA INTO A CUTTINGS
BED AND BACK REAMING CAN RESULT IN A CUTTING
LOAD SO HIGH THAT IT MAY BURY THE BIT AND THE BHA.
PACK OFF WITH LOST CIRCULATION AND/OR STUCK-PIPE
IS OFTEN THE RESULT
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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58. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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59. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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60. KEEP A COMPREHENSIVE PROGRAM FOR MUD
CLEANING HANDY AT ALL TIMES
THE FACTORS TO BE CONSIDERED ARE:
FLOW RATE
PIPE ROTATION
HI DENSITY SWEEPS
EXTENDED CIRCULATION
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
60

61. Thank You Very Much
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI
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