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

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

5
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
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
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
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
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
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
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
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


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

15
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
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
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
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


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

23


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
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





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






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

27
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

28
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
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
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
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
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

33
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

34
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

35
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

36
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
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
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
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
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
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
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
DISADVANTAGES

DILUTION

HIGH
VOLUMES

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

HIGH
COSTS

44
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
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
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
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

48
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

49
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
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
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
 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
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

54
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

55
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

56
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

57
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

58
GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI

59
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
Thank You Very Much

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

61

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GUIDELINES FOR EFFECTIVE 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 27
  • 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 33
  • 34. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI 34
  • 35. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI 35
  • 36. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI 36
  • 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 48
  • 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 54
  • 55. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI 55
  • 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 57
  • 58. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI 58
  • 59. GUIDELINES TO EFFECTIVE HOLE CLEANING - DR. S. V. DOSHI 59
  • 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 61