Lyons W.C. (ed.). Standard handbook of petroleum and natural gas engineering.2001- Volume 1

Drilling Bits and Downhole Tools

815

Nomlnal

sln

Tool

(A)

12

10

8

7

6%

Sp.cn1-m

CJolnt

'Sugg..l.d

.

C.mr

Makaup

HobSlt.

RacomNndad

iM

0m.t

OD

R-lb)

Pmrformance

Bar.

17YlmrU30

2'h

2'910 Spec@

TO80

160

30

120

3070

70.000

SpecifW 148

23

116

2OXI

55.000

12hlhru 15 2% 2'14

athru 12V4

2% 2'4

Sizeand

SameOD

149

23

110 1635 41.000

BMlhru 11

2'sis

2'14 AsDrill 145

23

112 1400

35.m

Collar

143

23

111 1100 27.000

144

23

111

890

2c.m

mmrus

2v4

2

Type

6%.

thru

9

2'/.

1

'h

Nota

1

All

dimensions

are given

in

Inches. unless otherwse staled

'2 Recommended

lor

optimum

IwI

life

'Courtesy

Smith

International, Inc

deviation problems, the shock absorber should be place as shown in Figures 4-171B

and 4-171D.

For turbine drilling, it is recommended that the shock absorber be placed

on top of the first stabilizer above the turbine as in Figure 4-171A.

Jars

Jars provide an upward or downward shock (or jar) to the entire drill string.

Early attempts to recover stuck drill pipe motivated the development of jars.

Types of Jars.

There are two general classes of jars: fishing jars and drilling jars.

A

fishing jar

is

used to free stuck drill string, and is added to the drill string

only when the string becomes stuck.

The drilling jar

is

used as a part of the drill string to work any time

it

is

needed. With modern drilling requiring more safety and less cost per foot,

it

has become more economical to use drilling jars. In areas where possible sticking

conditions exist, the drilling jar is ready to free a stuck pipe through calculated

string over-pull or slack-off. The jars are used immediately when the string

becomes stuck, which prevents excessive downtime and costly tripping. Unlike

the fishing jar, the drilling jar has the additional function of transmitting the

high amount of drilling torque to the bit.

Drilling Jar Design.

The jarring and bumping characteristic

of

drilling jars

is

determined by their specific type of release elements and stroke. There are three

basic types of release elements:

(1)

hydraulic,

(2)

mechanical, and

(3)

a combina-

tion of hydraulic and mechanical. Hydraulic mechanism employs a sleeve, or

valve that is pulled through a restricted area that allows only a small amount

of hydraulic oil to pass through. Once the sleeve, or valve passes through the

restricted area and enters the larger chamber,

it

is

free to travel upwards until

reaching the anvil that creates a sudden stop and sends a shock throughout

the string.

Mechanical mechanisms involve the following types of dynamic action:

1.

Adjustable spring pressure against locking system.

2.

T-slots system. A combination of upward overpull or string weight, and

right-hand torque is required. When torque is released, shots disengage for

jarring.

816

Drilling ai

nd

Well

Completions

MALE SPLINE

SAL

CAP

SPLINE

INSERT

FEMALE

SPLINE

MANDREL

1

80WL

BEL LEWLLE

SFWINGS

MAWEL

2

CIXVPBVSATlNG

PISTaV

Figure

4-170.

Christensen’s

Shock

Eze.

(Courtesy

Hughes

Christensen.)

Drilling

Bits

and Downhole Tools

817

A

B

C

D

Figure

4-171.

Recommended placement

of

the

Shock Eze. (Courtesy

Hughes

Christensen.)

3.

J-slots system. The slots will roll

out

with enough overpull or string weight.

Sets of springs apply lateral pressure holding mandrel in place.

4.

Firing racks system.

A

lateral pressure

is

applied by adjusting racks. Angle

on firing racks give it a

2:l

release factor when overpull or string weight

is applied.

818

Drilling and Well Completions

Types

of Drilling Jars.

There are two types commonly used commercial drilling

jars, combination of hydraulic (upward) and mechanical (downward) motion, and

purely mechanical action. The examples of both types follow.

Christensen-Mason

Jar.

(See Figure

4-172

and Table

4-103 [57].)

This

is

a

combination tool, offering possibility to jar upwards hydraulically and to bump

downward mechanically. The jar is equipped with a special releasing (locking)

mechanism,

so

that the jar cannot be fired upwards until the locking system

has been released. It has a 6-in. jarring stroke upwards and 30-in. for downward

bumping

[57].

Hevi-HitterrM Christensen

Jar.

(See Figure

4-173 [57A].)

This is a mechanical

drilling jar with firing racks system applied. Its jar force is constant regardless

of

torque applied.

TOOL

ASSEMBLED

(OPEN)

OUTER TUBE

INNER

TUBE

Flex

Joint

fl

El

J!y-iin.

i

Bumping Nut

;&

Compensating Piolon

(upver)

Mrndrrl

1

Mandrrl2

VdVO

Comprnsrting Plslon

(lower)

Locking Platon

~Mardrri

5

Packing

Ring

Buihing

Figure

4-172.

Christensen’s mason drilling jar.

(Courtesy Hughes Christensen.)

Drilling Bits and Downhole

Tools

819

I

II

Table 4-103

Christensen’s Mason Drilling Jar

I

1

Courtesy Hughes Christensen.

II.

.O

0

II

I

.....

Included in the drill string, the Hevi-Hitter jar can fire either upward or

downward. The jarring force, which can exceed

700,000

pounds on the larger

sizes, can be controlled from the surface by applying and holding right-hand

torque to increase impact, and by applying and holding left-hand torque to

decrease impact. Because the Hevi-Hitter jar recocks automatically, jarring

operations can proceed swiftly until the stuck pipe is free. Various impact forces

can be generated dependant upon weight of drill collars (or heavy weight drill

pipe) above the jars and the value

of

surface pull, as shown in Table

4-104

[57A].

Underreamers

The term “underreaming” has been used interchangeably with “hole opening.”

Underreaming is the process of enlarging the hole bore beginning at some point

below the surface using a tool with expanding cutters. This permits lowering

the tool through the original hole to the point where enlargement of the hole

is to begin.

820

Drilling and Well Completions

Table 4-1 04

Hevi-HitterTM Jar Impact Forces (1,000

Ibm)

[57A]

-~

Heavy-Welght

Drill Pipe or Drlll

Collar

Weight

Above

Jars

(Ibs.

x

1,000)

4 6

8

10

12

14 16 18

20

45

9

4 60

6 90

cri

p

7 105

E

8 120

.P

9 135

10 150

11 165

h

12 180

$

13 195

14 210

=

15 225

a'

16 240

h

83

E5 75

v

2

68

90

113

135

158

180

202

225

247

270

229

31 5

337

359

90

120

150

180

210

240

270

300

330

359

389

41 9

449

479

113

150

187

225

262

300

337

374

41 2

449

487

524

562

599

135

180

225

270

31 5

359

404

449

494

539

584

629

674

71 9

157

21

0

262

31 5

367

41 9

472

524

576

629

681

733

786

838

180

240

300

359

419

479

539

599

659

71 9

778

838

898

958

202

270

337

404

472

539

606

674

74 1

808

876

943

1010

1078

225

300

374

449

524

599

674

748

823

898

973

1048

1122

1197

Courtesy

Hughes Christensen.

Hole opening is considered as opening or enlarging the hole from the surface

(or

casing shoe) downward using a tool with cutter arms at a fixed diameter.

Thus, the proper name for the tools with expandable cutting arms is under-

reamers. The cutting arms are collapsed in the tool body while running the tool

in the hole. Once the required depth is reached, mud circulation pressure moves

the cutters opening for drilling operation. Additional pressure drop across the

underreamer orifice gives the operator positive indication that the cutter arms

are extended fully and the tool is underreaming at full gauge.

Underreamer Design.

There are two basic types of underreamers:

(1)

roller

cone rock-type underreamers and

(2)

drag-type underreamers. The roller cone

rock-type underreamers are designed for all types of forma-tions depending upon

the type of roller cones installed. The drag-type under-reamers are used in soft

to medium formations. Both types can be equipped with a bit to drill and

underream simultaneously. This allows for four different combinations of

underreamers as shown in Figure

4-174 [58].

Nomenclature of various under-

reamer designs are shown in Figures

4-175, 4-176,

and

4-177 [58].

Underreamer Specifications.

Table

4-105

[58]

shows example specifications for

nine models of Servco roller cone rock-type underreamers. Table

4-106

contains

example data for four models of Servco drag-type underreamers

[58].

Underreamer Hydraulics.

Pressure losses across the underreamer nozzles

(orifice) are shown in Figures

4-178

and

4-179

[58].

The shaded area represents

the recommended pressure drop required for cutters to fully open. These

pressure drop graphs can be used for pressure losses calculations (given pump

output and nozzles) or for orifice (nozzle) selection (given pump output and

pressure loss required).

Rock

Typre

Underreamer

Drilling

Bits

and Downhole Tools

821

Rock-Drtiftng

Type

Underreamer Underreamer

Figure 4-1

74.

Types

of

underrearners.

(Courtesy

Smith

International,

Inc.)

822

Drilling and Well Completions

Figure 4-1 75.

Rock-type underreamer nomenclature.

(Courtesy

Smith

International, Inc.)

Figure 4-1

76.

Rock-drilling underreamer nomenclature.

(Courtesy

Smith

International, Inc.)

Figure 4-177.

Drag-type underreamer nomenclature (open arms).

(Courtesy

Smith International, Inc.)

Drilling Bits and Downhole Tools

823

Table 4-105

Rock-type Underreamers (Servco)

[58]

Through

Casing.

Inches

Underreamer

Eody

Dia,

Inches

4112

5112

7

7-518

8-518

9518

l(1314

133/8

18-518

3518

4112

5w4

6

7-114

8-114

9-112

1

1-314

14-314

TOP.

Conrmtlons,

API

Reg.

2-3/8

3112

4112

6518

8518

2-718

4314 through

6112

6

through

9

8

through

11

8

through 13

9

through

14

10

through

15

13through

18

15

through

22

through

28

Courtesy Smith International, Inc

Table 4-106

Drag-type Underreamers (Servco)

[581

Model

Number

Specifications

57DP

72

DP

95DP

110DP

Body Dia.

544,

7-114.

9-112"

11"

Top

Conn.

3112"

4112"

6518"

Length (shoulder)

66''

71"

57'

57"

Expanded Dia.

16"

22" 28'

30"

(max.)

Standard Orifice Flo-Tel

Flo-Tel

314"

314'

Reg.

Courtesy Smith International, Inc.

Stabilizers

Drill collar stabilizers are installed within the column of drill collars. Stabilizers

guide the bit straight in vertical-hole drilling or help building, dropping, or

maintaining hole angle in directional drilling. The stabilizers are used to

1.

provide equalized loading on the bit

2.

prevent wobbling of the lower drill collar assembly

3.

minimize bit walk

4.

minimize bending and vibrations that cause tool joint wear

5.

prevent collar contact with the sidewall

of

the hole

6.

minimize keyseating and differential pressure.

The condition called "wobble" exists if the bit centerline does not rotate

exactly parallel to and on the hole centerline

so

the bit is tilted.

824

Drilling and Well Completions

Figure 4-1 78.

Pressure drop across underreamer (rock-type or drag-type

underreamer with one nozzle).

(Courtesy Smith International, Inc.)

Figure 4-179.

Pressure drop across underreamer (rock drilling underreamer

with three nozzles).

(Courtesy Smith International, Inc.)

Lyons W.C. (ed.). Standard handbook of petroleum and natural gas engineering.2001- Volume 1

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