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Drilling Technology
By
Dr. Khaled Abdel Fattah
CONTENTSCONTENTS
1. Introduction
2. Drill String Design
3. Formation Pressure Prediction
4. Fracture Pressure Determination
5. Casing Setting Depth Selection
6. Casing Design
7. Cementing Design
8. Borehole Problems
INTRODUCTIONINTRODUCTION
Drill String Design
PURPOSE OF DRILL STRINGPURPOSE OF DRILL STRING
Provide Fluid Conduit from Rig to Bit
Impart Rotary Motion to the Bit
Provide Weight on Bit
Lower and Raise Bit in the Well
Allow Formation Evaluation & Testing
DRILL STRING COMPONENTSDRILL STRING COMPONENTSDrill PipeBottom Hole Assembly
– Drill Collars– Stabilizers– Jars– Reamers– Shock Subs– Bit
DRILL PIPE DRILL PIPE
Consists of pipe Body and Tool joint
Available in three Length Ranges
Range Length, ft
1 18-22
2 27-30
3 38-45
DRILL PIPE DESCRIPTIONDRILL PIPE DESCRIPTION Pipe OD
Nominal Weight
Pipe Grade
Type of Upset
Connection Thread
Premium Classification
DRILL PIPE GRADESDRILL PIPE GRADES
GradeYield Strength, psi
E75,000
X95,000
G105,000
S135,000
API SEAMLESS INTERNAL UPSET API SEAMLESS INTERNAL UPSET DRILL PIPE DRILL PIPE STRENGTHSTRENGTH
PIPE SIZEPIPE SIZE Pipe OD is Outside Diameter of Plain End pipe Available Sizes are :
– 2-3/8”, – 2-7/8”,– 3-1/2”, – 4”, – 4-1/2”,– 5”, – 5-1/2”,– 6-5/8”
DRILL PIPE WEIGHTDRILL PIPE WEIGHT
Nominal Weight of pipe per foot
including wt of regular API connection
Adjusted Weight is Actual Weight of pipe
and Connection
Depends on Grads and Connection Type
DRILL PIPE DRILL PIPE CLASSIFICATIONCLASSIFICATION
New No wear and has never
Premium Uniform wear and a minimum wall thickness of 80% of original wall
Class 2 Allows drill pipe with a minimum wall thickness of 65 % with all wear on one side so long as the cross-sectional area is the same as premium class, i.e. based on not more than 20 uniform wall reduction
Class 3 Allows drill pipe with a minimum wall thickness of 55% with all wear on one side
SINGLE DRILL PIPESINGLE DRILL PIPE
fWBfBHWHLfBcWcLMOPY
L
9.0
MOPBWLBWLLWBfHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC +
Weight of HWDP+MOP
DRILL COLLARSDRILL COLLARS
Large OD Small ID Great Stiffness Thirty- Foot Joints
FUNCTIONS OF DRILL FUNCTIONS OF DRILL COLLARSCOLLARS
Provide Weight on Bit
Stabilize Bit
Provide stiffness to BHA and
Minimize Directional Control Problems
COLLAR SIZE SELECTIONCOLLAR SIZE SELECTION
Minimum Collar OD =
2(Casing Coupling OD) – Bit OD
Select Largest Drill Collar
That can be fished out of hole
WEIGHT ON BIT CALCULATIONSWEIGHT ON BIT CALCULATIONSBUOYANCY FACTOR METHODBUOYANCY FACTOR METHOD
CoscWBF
SFWOBcL
WOB = Weight on Bit, IbSF = Safety Factor (1.1-1.15)BF = Buoyancy Factor Wc = Drill Collar Weight in Air, Ib/ft
= Maximum Hole Angle at BHA, degrees
HEAVY WEIGHT DRILL PIPEHEAVY WEIGHT DRILL PIPE
Reduces failures at transition zone
Reduces downhole torque and drag in
directional drilling
Reduces differential sticking
DRILL STRING DESIGNDRILL STRING DESIGN Drill Collar DesignDrill Collar Design
Bit weight (lbs) Air Weight (DRILL COLLAR) = _____________
B. F. x S. F.
Where: B.F. = Buoyancy Factor S.F. = Safety Factor
(i.e., 0.90 = 10% S.F.; 0.70 – 30% S.F.)
Correcting S.F. after Air Weight Design is complete
=100 - (desired bit weight) x (100)
(Air Weight Calculated) x (B.F.)
Example of Drill Collar DesignExample of Drill Collar DesignFind the correct drill collar Air Weight to pick
up. if desired bit weight is 70,000 Ibs.. and the Mud Weight is 9.1 Ib/gal. (68 pcf). The hole size is 171/2", and a tapered string with 15% S.F. is desired. Consider using;
11" x 3" (8970 Ib/single)9-3/4" x 3" (6900 Ib/single) 8 1/2" x 3" (5070 Ib/single)
70,000 lbsAir Weight = 0.86 x 0.85 = 95,800 lbs.
B.F. = ( 65.44 – 9.1) / 65.44 = 0.86*S.F. (15%) = 100 - 15 = 85% (0.85)Try (1):(3) 11" drill collar = 26,910 Ibs,(3) 9 3/4" drill collar = 20,700 Ibs,(3) 8 1/2" drill collar = 15,210 Ibs,Total = 62,820 Ibs,Required = 95,800 Ibs,Remaining = 32,980 Ibs,
Example of Drill Collar DesignExample of Drill Collar Design
Second, Try: (3) Additional 9-3/4" = 20,700 Ibs
(3) Add. 81/2" = 15,210 Ibs.
Total 35,910 Ibs.
So With:
(3) 11" drill collar = 26,910 Ibs
(6) 9 3/4" drill collar = 41,400 Ibs
(6) 81/2" drill collar = 30.420 |bs.
98,730 Ibs.
Example of Drill Collar DesignExample of Drill Collar Design
Actual Air Weight = 98.730 Ibs Calculated Air Weight = 95,800 Ibs.
Difference. = 2,930 Ibs.
Corrected S.F. = 100 - (70,000) x (100)
(98,730) x (0.86)
100 - 82.4 = 17.56% (New S.F.)
Example of Drill Collar DesignExample of Drill Collar Design
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
L = Length of the Drill Pipe, ft
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
Lc = Length of the Drill Collar, ft
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
LH = Length of the Heavy Weight Drill Pipe, ft
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
wH = Nominal weight of the H/Weight Drill Pipe, lb/ft
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
wc = Nominal weight of the Drill Collar, lb/ft
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
w = Nominal weight of the Drill Pipe, lb/ft
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
Bf = Buoyancy Factor, fraction
= (1 – m/steel)
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
MOP = Max Overpull on the drill string by the Drawworks, lb
DRILL STRING DESIGNDRILL STRING DESIGNSINGLE-GRADE DRILL PIPESINGLE-GRADE DRILL PIPE
MOPBwLBwLLwB fHHfccf
0.9 × Yield Strength = Weight of DP + Weight of DC + Weight of HWDP + MOP
f
fHHfcct
wB
BwLBwLMOPPL
9.0Pt = Yield Strength of pipe, lb
DRILL STRING DESIGNDRILL STRING DESIGNDUAL-GRADE DRILL PIPEDUAL-GRADE DRILL PIPE
f
fHHfccf
Bw
BwLBwLBwLMOPYL
2
112
9.0
L1 = Length of the Drill Pipe—Grade-1, ft
w1 = Nominal weight of the Drill Pipe—Grade-1, lb/ft
L2 = Length of the Drill Pipe—Grade-2, ft
w2 = Nominal weight of the Drill Pipe—Grade-2, lb/ft
MAXIMUM OVERPULLMAXIMUM OVERPULL(MOP)(MOP)
Maximum Overpull should not exceed 90% of Tensile Strength of Weakest
Drill Pipe
Pa = Pt x 0.9
Where:Pa = maximum allowable design load in tension, lb.Pt = theoretical tension load from hand book, Ib.
MAXIMUM OVERPULLMAXIMUM OVERPULL(MOP)(MOP)
M.O.P. = Pa / P
Where:P submerged load hanging below
the top joint of drill pipe, lb.
fdcdcdpdp BwLwLP )(
dp
dcdc
fdp
t
W
LW
BSFW
PL
**
9.0
COLLAPSE PRESSURECOLLAPSE PRESSURE
. .
Collapse RatingAllowable Collapse
S F
Collapse P = External P – Internal PCollapse P = External P – Internal P
BURST PRESSUREBURST PRESSURE
. .
Burst RatingAllowable Burst
S F
Burst P = Internal P – External PBurst P = Internal P – External P
Torsional StrengthTorsional Strength
The actual torque applied to the pipe during drilling is difficult to measure, but may be approximated by the following equation.
T = HP x 5,250 RPM
Where: T = torque delivered to drill pipe, ft.-lbs.HP = horse power used to produce rotation of pipeRPM = revolutions per minute
Examples of Drill Pipe DesignExamples of Drill Pipe DesignExample 1Anticipated T.D. 12,000 ft.Hole Size 12 1/4 inches.Expected Mud Wt. 13.4 Ib/gal. (100 pcf).Desired S.F. or Safety (Margin of over pull) 50, 000 Ibs. (collapse S.F. 1.125).Length and Size Drill Collars (3) 10" drill collar, I.D. = 2 13/16" (12) 9" drill collar, I.D. = 2 13/16" Total Length 450 ft. Total Air Wt. 92, 340 Ibs.HWDP (21 joints) 5" x 3" x 50 Ib/ft. Total Length 630 ft. Total Air Wt. 31, 500 Ibs.Drill Pipe 5", 19.5 Ib/ft., XH, Class-2. Adj. Wt. 20.99 Ib/ft. Grade "E" and /or Grade"95“ (21.09 Ib/ft.)Tensile Strength Grade "E" API Class 2 = 311,540 Ibs. Grade "95" API Class 2 = 394,600 Ibs.Buoyancy Factor 0.795 w/13.4 Ib/gal. mud.
Examples of Drill Pipe DesignExamples of Drill Pipe Design
Solution Length of drill pipe (5", 19.5 Grade "E") to go above Hevi-wt. and drill
collar's. Pt x 0.9 - M.O.P. – WcLc = Ldp
Wdp x Bf Wdp
Ldp = ( 311,540 x 0.9) - (50,000) _ 123,840 lbs. 20.99 x 0.795 20.99 = 13,806 - 5900 = 7,906 ft. (will use 7900 ft.)*123,840 - Total Air Weight of drill collar's and Heavy weight drill pipe
(2) Calculate Air Weight hanging below this top joint of Grade "E" drill pipe
P = (ldp x Wdp ) + (Lc x Wc ) (not corrected for buoyancy) P = [(7900 ft.) x (20.99) + (123,840)]= 165,821 Ibs. + 123,840 Ibs. = 289,661 Ibs.
Examples of Drill Pipe DesignExamples of Drill Pipe Design
Solution
(3) Accumulate Length of Drilling AssemblyTapered drill collar 450 ft. Hevi-Wt. 5" 630 ft. Grade "E" 5" 7900 ft. Accum. Total 8980 ft. Require 12,000 ft.Remaining Grade 3,020 ft.(4) Length of drill pipe No.2 5” Grade "95”Ldp No2 = ( 394,600 x 0.9) - (50,000) - 289,661 lbs.
(21.09 x 0.795) 21.0918,199 - 13.735 = 4465 ft. (will use only 3020 ft.) *•289,661 Ibs. = Total Air Wt.at DRILL COLLAR Hevi Wt.,
Grade "E".
Examples of Drill Pipe DesignExamples of Drill Pipe DesignSolution (5) Calculate Total Air Weight of stringP = {(3020 ft. x 21.09) + 289,661 Ibs.} = 63.692 + 289,661 = 353,353 Ibs.
(6) Corrected for BuoyancyWeight in 13.41 Ib/gal. mud = 353,353x 0.795= 280,916 Ibs.( 7) Summary of Design Calculation Weight in
Items Length 13.4 Ib/gal.mud
-----------------------------------------------------------------------------------------------------
DRILL COLLAR 10" and 9" tapered 450 ft. 73,410 Ibs. Hevi-Wt. drill pipe (5" - 50 Ib/ft.) 630 ft. 25,043 Ibs. DRILL PIPE Grade "E" (5". 19.5 - 20.99) 7,900 ft 131,828 Ibs. DRILL PIPE Grade '•95" (5". 19.5 - 21.09) 3,020 ft. 50,635 Ibs.
Totals 12,000 ft. 280,916lbs.
Examples of Drill Pipe DesignExamples of Drill Pipe DesignSolution (8) Check on Margin of OverpullGrade “ E “ (311,540 x 0.9) - (230,281) = 50,105 IbsGrade "95" (394,600 x 0.9) - (280,916) = 74,224 Ibs.(9) This design Could Be Used Down To 13, 445 f t.Note: Only 3020 ft. of Grade"95" was used and this allowed another
1466 ft. of Grade "95" for use.(10) AIIowable Collapse Pressure For 5", 19.5, Grade "E", API Class - 2 = 4760 psi. Btm 5" @10,920'Pac = ( 4760) = 4231 psi ( 1.125) (11) Net Collapse Pressure Pc = (10,920 ft )(13.4 Ib/gal.) = 7600psi 19.251 (12) Tension Safety Factor Grade “ E” = 280,386 = 1.22 230,281 Grade "95" = 355,140 = 1.26
280,916
Drill Pipe Design Using Two Drill Pipe Design Using Two Different Grades of PipeDifferent Grades of Pipe
Example:Anticipated Total Depth with this String...................... 1 5, 000 feet
Hole Size (9-5/8" Casing (@ 12,000 feet) ....................... 81/2 inches
Expected Mud Weight......................................... 1 3. 4 Ib/gal.
Desired S.F. of Safety Margin - Collapse - 1.125, M.O.P. . 50, 000 Ibs.
Length and Size of Drill Collars 61/2 " x 2 13/16 x 950 ft.
wt. Ib/ft. 91 Total Wt. (air) 86,450 lbs.
Drill Pipe; 5", 19.5 x H, Grade "E" 20.99 Ib/ft. API Class No. 2
5” , 19.5, x H, Grade "95" 21.09 Ib/ft. APl Class No.2
Tensile Strength; Grade "E". API Class No. 2................ 311, 540 Ibs.
Grade "95". API Class No. 2 …………………............... 394,600 Ibs.
Buoyancy Factor w/13.4 Ib/gal............................................... 0.795
Drill Pipe Design Using Two Drill Pipe Design Using Two Different Grades of PipeDifferent Grades of Pipe
Solution1. Length of drill pipe (5" 19.5 Ib/ft., Grade "E") to go above drill collar
Ldp = (311,540 x 0.9) - 50,000 _ 86,450 Ibs.
20.99 x 0.795 20.99
= 13,806 - 4119 = 9688 ft.
2. Calculate Air Weight Hanging Below This Top Joint of Grade "E" d.
p = (9688 x 20.99) + 86,450 Ibs. = 203,351 + 86,450 = 289,801 Ibs.
3. Accumulated Length of Drilling Assembly
DRILL COLLAR ........................................... 950 feet
DRILL PIPE Grade "E“ .............................. 9,688 feet
Total ........................................ 10,638 feet
Require ...................................... 15, 000 feet
Remaining Crade "95“ ....................... 4, 362 feet
Drill Pipe Design Using Two Drill Pipe Design Using Two Different Grades of PipeDifferent Grades of Pipe
Solution
4. Length of drill pipe No. 2 (Grade "95")
Ldp No2 = (394,600 x 0.9) - 50,000 - 289,801
21.09 x 0.795 21.09
= 18,199 - 13,741 = 4,458 ft. (will use 4,362 ft.)
5. Calculate Total Air Weight of String
P = [4362 (21.09) + 289,801] = 91.995 + 289,801 = 381,796 Ibs.
6. Corrected For Buoyancy
Weight in 13.4 Ib/gal. mud =
0.795 x 381,796 Ibs. = 303, 528 Ibs.
Drill Pipe Design Using Two Drill Pipe Design Using Two Different Grades of PipeDifferent Grades of Pipe
Solution7. Summary of Design Calculation
Item Length (ft.) Weight in13.4 Ib/gal. mud
--------------------------------------------------------------------------------------------------------------
DRILL COLLAR (61/2 x 2-13/16 x 9501) 950 68,728 Ibs.
DRILL PIPE (19.5 20.99 Grade "E") 9,688 1,6b4
DRILL PIPE (19.5 - 21.09 - Grade "95") 4,362 73,136
Total 15,000 ft. 303,528 Ibs.
8. Check on Margin of Overpull (M.O.P.)
5", (19.5 - 20.99) Grade "E" -- (311,540 x 0.9) - 230.392 = 50.000 Ibs.
5". (19.5 21.09) Grade “95" - - (394,600 x 0.9) - 303.528 = 51,612 Ibs.
9. Tension Safety Factor
Grade -E" = ( 311,540 x 0.9) = 1.22
230,392
Grade- “95” = (394,600 x 0.9) = 1.17
303,528
Many engineers feel that the design S.F. should be approximately 1.25 - 1.33
Drill Pipe Design Using Tapered Drill Pipe Design Using Tapered Drill Pipe StringDrill Pipe String
Example:Anticipated Total Depth.......................................... 18,000 feet
Hole Size (7" liner - 18,000 - 11, 500 ft.)........................ 6-1 / 8 inches
Expected Mud Weight (0.833 psi/ft.)..... ...................... 16. 0 Ib/gal.
Designed Safety Factor - M.O.P. ................................ 50,000 Ibs.
Length and Size of Drill Collars ................................. 950 ft.
Weight drill collar (Air) 4 3/4” x 2 x 950 ft.) 50 Ib/ft.. ................ 47, 500 Ibs.
Drill Pipe – 31/2. 13.30 - 14.06. Grade "E", API Class-2, XH
5", 19.50 - 20.99, Grade "E", API Class-2, XH
5", 19.50 - 21.09, Grade "95", API Class-2, XH
Tensile Strength
31/2", 13.30. Grade "E", API Class-2, 212,250 Ibs.
5", 19.50, Grade "E", API Class 2, 311,500 Ibs.
5", 19.50, Grade "95", API Class-2, 394,600 Ibs.
Buoyancy Factor w/16.0 Ib/gal. ................................. 0.756
Drill Pipe Design Using Tapered Drill Pipe Design Using Tapered Drill Pipe StringDrill Pipe String
Solution1. DRILL PIPE Design ( 31/2, 13.30, Grade "E") for Below Top of liner to
T.D. 6600 ft. required.)
Ldp = (212,250 x 0.9) - 50,000 - 47,500
14.06 x 0.756 14.06
= 13,267 - 3378 = 9889 ft. (will use 5650 feet) .
2. Air Weight of String Supported by Top Joints of 31/2" drill pipe
P1 = (5650 ft.x 14.06) + (950 ft. x 50 Ib/ft.)
= 79,439 + 47,500 = 126,939 Ibs. (31/2" drill pipe + 4-3/4" drill collar)
3. drill pipe Design for 5" 19.5. Grade "E" (above 31/2", 13.30)
Ldp No.2 = (311,500 x 0.9) - 50,000 - 126,939 = 8469 ft.
20.99 x 0.756 20.99
4. Air Weight of String Supported by Top Joint of 5", 19.5, "E"
P = (8469 x 20.99) + 126,939 = 177,764 + 126,939 =
= 304,703 Ibs. (5", 19.5, "E" +31/2 + 4-3/4drill collar)
Drill Pipe Design Using Tapered Drill Pipe Design Using Tapered Drill Pipe StringDrill Pipe String
Solution
5. drill pipe Design for 5", 19.5, Grade "95", (above 5", Grade "E")
Ldp No.3 = (394,600 x 0.9) - 50,000 - 304.703
21.09 x 0756 21.09
= 4690 feet (will use 2931 ft.)
6. Air Weight of String Supported by Top Joint of 5", 19.5, Grade ’95’
P3 = (2931 ft. x 21.09) + 304,703 - 61,815 + 304,703 = 366, 518 Ibs.
(complete string weight in air)
7. Buoyancy Weight of String
366,518 x 0.756 = 277,087 lbs.
Drill Pipe Design Using Tapered Drill Pipe Design Using Tapered Drill Pipe StringDrill Pipe String
Solution
8. Summary of Drill Strinq Design
Weight in 16.0
Item Length (ft.) Ib/gal. mud (Ibs.)
Drill collars (4-3/4 x 2 x 950) 950 35,910
Drill Pipe (31/2, 13.30, Grade "E") 5,650 60,056
Drill Pipe (5", 19.5, Grade "E") 8,469 134,390
Drill Pipe (5", 19.5. Grade "95") 2,931 46,732
Totals. ............................ 18,000 ft. 277,0881bs.
Drill Pipe Design Using Tapered Drill Pipe Design Using Tapered Drill Pipe StringDrill Pipe String
Solution9. Margin of Overpull Check
31/2. 13.30, Grade "E" = (212,250 x 0.9) - 95,966 = 95,059 Ibs.
5", 19.50, Grade "E" = (311,500 x 0.9) – 230,056 = 50,294 Ibs.
5", 19.50, Grade "95" = (394,600 x 0.9) - 277,088 = 78,052 Ibs
10. Torsional Yield
31/2", 13.30. Grade "E", API CIass No. 2 =11,710 ft. Ib.
5". 19.50, Grade "E", API Class No. 2 = 26,320 ft. Ib.
11. Collapse Pressure
31/2”, 13.30, Grade "E".............10,250 psi
Pc = 17,050 ( 16.0lb/gal.) = 14,170 psi
19.251
Therefore, this pipe must be protected against collapse and a D.S.T. may result in failure.
BOTTOM HOLE ASSEMBLYBOTTOM HOLE ASSEMBLY
Purpose:
– Drill usable hole economically
– Maximize penetration rate
– Minimize formation of dog legs
– Prolong service life of bit and drill pipe
BHA COMPONENTSBHA COMPONENTSHeavy weight drill pipe
Drill Collars
Stabilizers
Shock Absorbers
Jars
Reamers
Bit
FUNCTIONS OF STABILZERSFUNCTIONS OF STABILZERS
Centralize Drill Collars in hole and increase
Stiffness
Increase ability of Drill Collars to drill
smooth straight hole
Wipe wall of hole to ensure full gage
Spiral
Stabilizers
SHOCK ABSORBERSSHOCK ABSORBERSReduce or Eliminate vertical oscillations
Maintain uniform bit load
Increase bit life
Increase ROP
Reduce drill collar failures
JARRING DEVICESJARRING DEVICES
There are sloughing formations There are sensitive shales Mud system does not have good suspension
properties There is expensive equipment in BHA
Generate upward or downward load to free stuck pipe or release fish
Jars are needed when :
Hydraulic JarsHydraulic Jars
TYPES OF BOTTOM HOLE TYPES OF BOTTOM HOLE ASSEMBLIESASSEMBLIES
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