Drilling a horizontal well using an electric downhole motor

7/21/2019 Drilling a horizontal well using an electric downhole motor

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DRILLING OF HORIZONTAL WELLS WITH A N ELECTRIC

DOWNHOLE MOTOR

S A Shirin-Zade, 7957Moscow,

6

Leninskiy Prospect; A. H. Mirzadzhanzade, N P O

Burooaya Technika

,

Russia;

A S Oganov and H. G. Gulatarov, 745100

Nebit -Dag

Koturdepinskoe UBR Turkmenistan

Abstract

In Russia, Ukraine and Byelorussia more than 300 horizontal wells have been drilled, mainly, with

hydraulic downhole motors. Yet, the use of the Electric Downhole Motor EDM) for drilling horizontal and

horizontally branched holes holds much promise. The advantage of this drive system is the availability of a

reliable communication channel with the bottom hole. This makes it possible to obtain a continuous informa-

tion on the bit and EDM operation, borehole path parameters while providing the transmission of the power

required for the rock destruction a t the bottom.

The technique and technology available allows us to drill horizontal wells with a long and medium radius of

curvature. The shortened motors of 95 and 105 mm diameter, which are now in the stage of development, will

provide for drilling short radius wells 20-30 m).

In the paper, the results of drilling horizontal wells in Turkmenistan are considered.

In 1990-1992 three wells with a depth

of

3603-3653 m have been completed. 45 more wells at 3500-4150 m

are planned.

Technical and economical drilling performance, casing programs and drill pipes sizes, EDM and surface

equipment characteristics are presented. Efficiency of drilling technology developed on the basis of the self-

organization synergetics) is shown. Drilling experience is generalized with the application of fuzzy set theory

methods and recommendations on

BH s

and drilling practices are given.

INTRODUCTION

Horizontal wells have been drilled with the electric

downhole motor in Russia, Ukraine, Turkmenistan

and Azerbaijan.

The first horizontally branched holes have been

drilled in the West Ukraine to a depth of 3500-

3700 m in the seventies.

In 1978 the horizontal well 196 was drilled in

Novo-Uzybashev area in Bashkiria. Here, horizontal

wells have been drilling with electric downhole

motors EDM) in Lemizinskoe, Mikhailovskoe,

Arlanskoe and other oil fields since 1988. In this

region more than 20 wells have been drilled with a

curvature radius up to 120 m.

In Turkmenistan in 1990-1992 three wells with a

depth of more than 3600 m were drilled with EDM

in the Koturdep area, where the oil recovery

was

increased 5 times and the field development invest-

ment decreased 2.5 times.

1. DRILLING OF HORIZONTAL WELLS

WITH THE ELECTRIC DOWNHOLE

MOTOR IN KOTURDEP AREA WEST

TURKMENISTAN)

1.1. Geological characteristic of the area

From the tectonics point of view in the area

overall brachy-anticline there are marked out four

places which are formed by faulting with the ampli-

tude of about 200 m. The crown central) place is

settled relative to the west one. The north-east side,

in its turn, is downcast to the same extent relative to

the central place. The angle of dip is 12-20 degrees.

The horizontal wells no. 1630, 1631, 1632 were

drilled to the upper levels of low red-coloured soils

NK7) in the west district of the area which was

16 km long and 8 km wide.

The lithologic and stratigraphic section of the area

is characterized as follows.

Proceedingsof the 4th World Petroleum Congress

994

The Executive Beard

of

the World Petroleum Congress

Published by John Wiley Sons

181


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NEW DRILLING TECHNOLOGY

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82

Bakinsky stage (up to 600 m) is represented by the

alternation of low-consolidated clays and sands.

Apsheronsky (600-1600 m) consists, almost fully,

of the so called black clays. They are prone to

spontaneous swelling, dispersion in the mud and

cause drilling problems (borehole restriction, tight-

ening, jamming and sticking of a drill string).

Low red-coloured soil section (1635-4000 m) is

characterized by high clayiness (from

5

to 80 ) and

abnormally high formation pressures, anomaly coef-

ficient being above 1.4. Black clays are met here in

the interval of 1900-2200 m.

All permeable formations (sands, sandstones, silts,

siltstones) are abrasive. The producing horizon NK7

represents a reservoir of granular type with clays and

sands interbedding. The porosity varies from 2 to

30 , permeability-from millidarcy fractions up to

2400 md, carbonate content-from 14 up to 25 .

1 2 Dri l l ing of the f i rst hor izontal wel ls

The task of the first wells was reduced to:

the investigation of the possibility of drilling in

NK7 producing formation with a horizontal bore-

hole;

the test of drilling technology with EDM in condi-

tions of abnormal formation pressure;

the test of current electrodrilling technique and

equipment in drilling horizontal wells.

The information about the applied drilling tech-

nique and technology are given below.

Drilling equipment. The drilling rig Uralmash 4

was used additionally fitted up with the following

devices and equipment electrodrill, power trans-

former (TM35-630/6), EDM monitoring and pro-

tection device (Y335-83), current consumer (T3-

2MB5), isolation control device (ICD), current

supply by cable sections (KCT1-TT) mounted in drill

pipes as well as devices for the current supply and

EDM maintenance.

The technical characteristics

of

the rig are as

follows

maximum load capacity-2000 kN;

drawworks drive po wer 470 kWt;

alternating-current drive;

pump hydraulic power-500 kWt;

maximum mud pump capacity-51 I s;

maximum operating pressure-25.0 MPa.

Casing program. The actual well casing program is

given in Table I.

All

casings, with the exception of the production

casing were cemented to the surface. The production

casing was cemented with the use of a packer

HAM-140 for open-bottom cementing. Below the

packer there are mounted filtered pipes

of

140 mm

diameter with preliminary drilled holes of

10

mm

diameter with holes per 1 m, placed along the

screw line.

Electric downhole motor.

When drilling the follow-

ing EDM are used for:

surface hole and first intermediate hole drilling-

3290-12AMB5 with a reducing gear insert ( i =

3 ) ;

second intermediate hole drilling-3240-8MB5

( i = 3 ) with a bending mechanism;

production hole drilling-3164-8MB5 ( i = 3) with

a bending mechanism.

In Table II EDM technical characteristics are

tabulated.

Telemetric system.

The control for the three-

dimensional position of the well

in

the slant hole is

accomplished by the telemetric systems 1CT3-215-

Y3 and 1CT3-164-Y3 completed with the surface

control panel llH-3M3.

The telemetric system provides for the constant

measurement of the zenith angle in the 0-120 range,

T BLE I

asing program

Setting depth, m

Name of the casing Casing diameter, mm Well 1630 Well 1631 Well 1632

Conductor

630 5 5 5

Surface casing

426 600 588 395

Extended conductor 530 30 30 30

First intermediate casing

324 1797 1797 1794

Second intermediate casing

245 3442 3426 3346

Combined production casing 140

x

146 x 168 3653 3606 3603


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NEW DRILLING TE HNOLOGY

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TABLE

II

EDM

technical characteristics

Diameter, Length, Rated power, Rotational Torque, Efficiency,

Motor

type mm m

kWt

speed,

s -

kHm

3290-12AMB5

290 14.0- 240 7.58 5.10 72.0

3240-8MB5

240 13.4

210 11.50 2.97 75.0

3164-8MB5

164 12.3

75 11.42

1.10

61.0

drift angle

of

the hole and whipstock orientation

angle in the range of O-360, bit weight and rota-

tional speed of the motor shaft. The measurement

error of each parameter is

&

2.5 . The telemetric

system can be used at a bottom hole temperature up

to 100C.

Rock destruction tool

Operation data

of

bits used

in drilling horizontal wells are given in Table

III.

Drilling fluid

When drilling, the second interme-

diate hole, lignosulphonate drilling mud was used.

Further deepening of the hole was made with an

inhibited micellar mud (density-1 540 kg/m3,

viscosity-28 s water loss-2 sm3, mud cake

th ickness4 .5 mm, shear strength-1-4 mg/m2).

Drilling

Drilling with EDM has its own specific

features. EDM plays a different role in forming the

separate intervals of the well profile. This results

from the less rigidity of EDM (by

30-50 )

and the

greater length (by 1.3-1.4 times) as compared with

the one-sectional turbodrill. Owing to this there is

more possibility for spontaneous hole deviation,

when drilling a vertical hole section.

When drilling a build up angle section with a

deflector mounted above the EDM the possible bore-

hole deviation rate will be less. On the one hand, it is

connected with the increase of the EDM length, and

that results in an increase

of

the radius of the motor

entering into the borehole. On the other hand, it is

connected with a decrease of the

BHA

deflecting

capacity at the expense of EDM rigidity decrease.

The less EDM rigidity can play a positive role, if

the deflectors are mounted below its center of

gravity. In this case the passability of the deflecting

BHA

along the crooked hole is improved. This holds

true for the cases of drilling with straight pipe and

stabilizer.

The increase of EDM weight as compared to

turbodrills decreases the deflecting capacity of

BHA

when the deflector (bent sub) is mounted above the

EDM center of gravity, and increases the deflecting

TABLE

III

Bit performances when drilling horizontal borehole

Drilling practices

Drilling Bit performances

No.

of

interval, Rotational

Bit weight

according Pump capacity,

wells m Bit

type h,

m

t,

h V

m/h speed, s l to weight indicator,

kN m3 s

1630 3450-3653 J1215.9 20.3 13.1 1.55 1.17 140-300 0.026

MC-THY

R45

1631 3429-3601 J1215.9 14.5 9.6

1.51

1.17 75-500 0.026

MC-THY

R45

J1215.9 12.0 11.0 1.09 3.67 100-450 0.026

MC-rH

R44

I215.9 15.0 12.3 1.22 3.67 100-450 0.026

M-TAY

R54

1632 3351-3603 I1215.9 19.4 5.6 3.46 3.67 120-250 0.022

MC-rHY

R45


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184 NEW DRILLING TE HNOLOGY

capacity, when the deflector is built-in below the

EDM center of gravity. When drilling with the

'straight pipe' without stabilizer, the big weight of

EDM increases the normal weight component on the

lower hole wall and this results in an increase of its

drilling intensity and decrease of curvature.

The actual profiles

of

horizontal wells no. 1630,

1631 and 1632 drilled with EDM in the Koturdep

area are shown in Figs 1 , 2 and 3.

Drilling of intervals from to the second interme-

diate casing setting depth was carried out with EDM.

In the well 1630 the interval of build up angle and

horizontal section of borehole was drilled with EDM

and PDM-deflector of OUI-172 type with hinge

element.

In the well 1631 the interval of build up angle

(3429-3536 m) was drilled with PDM OUI-172, and

the subsequent interval (3536-3606 mbwith EDM

By this means, in these two wells the horizontal

drilling technology with EDM was perfected and this

allowed the well 1632 to be drilled from to the total

depth

(3603

m) with EDM.

The operations on the hole deviation were carried

out with BHA: 295.3 mm bit; EDM 3240-8MB5

i

3) with bending mechanism MM 240-1 x 1.5 ;

3164-8B

i

3).

65

355

I

n 15 100

5 o

Fig. 1. Actual profile of horizontal well no. 1630: 1) verti-

cal section; (2, 3, 5, 9) 'shoes'

of

surface casing, first inter-

mediate, second intermediate and production casing

correspondingly; (4) section of building up zenith angle to

22 ;

(6) section

of

building up zenith angle to 86.3 ; (7, 12)

section of zenith angle stabilization; (8) section of zenith

angle decrease; (10, 11) top and bottom of the producing

formation.

I I

I

J

355

n I 5 0 100 5

o

Fig. 2. Actual profile of horizontal well no. 1631: (1) side-

tracking section; (2) section of building up zenith angle to

81 ; (3) section of drilling with reamer; (4) section of zenith

angle stabilization.

1794

2400

3100

3250

32

3350

345

36 3 I

I

3 w

1

Fig. 3. Actual profile of horizontal well no. 1632: (1) verti-

cal section: (2)

section of building up zenith angle to 37.5 ;

(3) section

of

building up zenith angle to 78.4 ;

(4)

section

of zenith angle stabilization.


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NEW DRILLING TE HNOLOGY

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isolation control device (ICD); drill-collars; drill

pipes.

From the depth of 3400 m to 3450 m the well was

drilled with a stabilized angle of inclination equal to

22 , with BHA including: 295.3 mm bit; EDM 3240-

8MB5

i

3)

with two centralizers

of

290

mm diam-

eter on the motor body and one centralizer

of

290

mm diameter mounted between

ICD

and drill

collar.

For drilling the build up angle interval

(3450-

3510 m) there was used BHA including: 215.9 mm

bit; motor-deflector

ODI-172

with axis skewness

equal to

2

with a hinge element on the top with the

5 skewness of 3.2 m length; telesystem 1CT3-164-

Y3 of

8

m length; ICD; combined drill string of 127

and

140

mm pipe diameter. With this assembly the

inclination angle from

22

to

85

was built up with

a

rate of

10.5

per

1

m) with the azimuth being

255 .

Further, in the

3510-3546

m interval the motor

OIII-172

without bending mechanism was used in

combination with a 215.9 mm reamer. With this

assembly the zenith angle was increased from 85 to

86 25', and after this the reamer was removed and

the well was deepened to 3647 m with a smooth

decrease of angle up to 71 .

The 3647-3653 m interval was drilled with the

motor

ODI-172

without centralizers, therewith the

zenith angle decreased to 70 .

When attaining a depth of 3653 m, the drilling of

the well was stopped as the set task was achieved.

In the well

1632

the deviation was begun from

a

depth of 3044 m, and at a depth of 3351 m the zenith

angle of

40.3

was built up. The total vertical devi-

ation was about

71

m.

The operations on the build up angle in this inter-

val were carried out with

BHA:

295.3 mm bit; motor 3240-8MB5 i 3) with

bending mechanism

MH-240 (1 x 1.5 );

telesystem

1CT3-215-Y3

of

8

m length;

ICD;

drill collars

of

203

mm diameter and

25

m length; drill collars of

178 mm diameter and 5 m length and drill pipes

of 140 mm diameter. When attaining the depth of

3247

m the drill collars were removed from the

BHA.

For further building up the angle below the second

intermediate casing there were used the BHAs:

in 3351-3427 m interval-215.9 mm bit; 215.9 mm

reamer; EDM 3164-8MB5

i

3) with 2 deviation

mechanisms

MM-1 x 1.5

of

15

m length; tele-

systems

1CT3-164-Y3

of

8

m length;

ICD

and

combined drill string of 127 and 140 mm diam-

eters. The average rate of build up angle was 3.3 /

1 m, the zenith angle increased from

40.3

to

65.2 ;

in 3427-3462 m interval-215.9 mm bit; 215.9 mm

reamer;

EDM-3164-8MB5

i

3)

with

2

bending mechanisms MH

1 x

1 of

15

m length;

telesystem

1CT3-164-Y3; ICD

and drill pipes of

127 and 140 mm diameters. The zenith angle

increased up to

78.4 (3.8 /10

m).

With the same BHA, but without the bending

mechanism, the well was drilled to a total depth of

3603

m.

After the full complex of geophysical operations

had been carried out, the combined production

casing

(140 x 146 x 168

mm) with filter and

HAM-140 packer was run. The running and cement-

ing were carried out without any problems.

1.3.

The technolo gical and technical

problems revealed in drilling and their

solution

When drilling a horizontal borehole, the main

problem consists in the transmission of the required

weight to the bit and in defeating the resistance

forces during round trips.

From the weight indicator diagrams of

1631

and

1632 wells Figs 4 and 5) it is seen that the bit weight

changed with the zenith angle increase. So in order

to establish the bit weight equal to 160-200 kN

depending on the formations drilled, in different

parts of the borehole it was necessary to make the bit

Fig.

4

Diagram of bit weight in well 1631 to the weight

indicator.


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86 NEW DRILLING TECHNOLOGY

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1

cleaning bottom hole and borehole from the cuttings.

It is established, that the force holding the particles

in suspended state in the horizontal borehole is much

greater than in the vertical one. The introduction of

known measures on drilling mud properties control

and increase the annular flow velocity improve only

slightly borehole cleaning.

The horizontal hole section path control is of great

importance, especially when drilling thin formations

with a gas cap and underlying water-bearing bed.

With the producing formation thickness being less

than 35 m, vertical borehole deviation limit should

be within _ 1.0 m.

In the process

of

drilling the first wells in the

Kurdep area the necessity to improve and develop

the technique for horizontal drilling with E D M was

revealed:

Fig. 5. Diagram of it weight

in

well 632 to the

weight

indicator

weight up to 700 kN. The creation of weights higher

than was used on the bottom hole, made it necessary

to take the drill string off the bottom in order to

avoid it sticking. Practically, drilling of horizontal

sections converted to continuous take-off, pulling out

and running

of

the drill string and very short drilling

up to 20-30 s In order to eliminate this a new BHA

was used in the well no.

1632

from a depth of

3480 m: 215.9 mm bit; 212 mm reamer; E D M

3-164-8MB5

(i =

3); ICD; drill pipes of 127 mm

diameter and 300-375 m length; drill collars of

146 mm diameter and 75 m length; drill pipes of

140 mm diameter.

Actually drill collars were moved to the top part of

the borehole with the angle less than

60 ,

that is to

the shoe

of

the previous string. After this, cases of

drill string hanging-up ceased, and in order to

create bit weight much less load was required. There-

with, the penetration per bit increased also up to

28

m.

In order to decrease the tensile forces in the drill

string, the build up interval should be started deeper.

Another action, providing for the decrease of fric-

tion forces, is the gradual increase of the angle build

up rate. When meeting these conditions in the

section of the highest build up rate, the tensile forces

in the drill string from the resistance forces are

minimum, and the drill string passes through the

remaining borehole with a minimum friction force.

One

of

the major problems of drilling horizontal

wells is the problem of drilling mud selection for

shortened

E D M

and telemetric systems

of

not

more than

6

m length with improved strength

characteristics;

more perfect instruments for carrying out a geo-

physical survey in intervals of intense deviation;

electric deflector (guided) for borehole deviation

and correction immediately in the process of drill-

ing, etc.

1 4 Generalization of drilling results

Horizontal wells were first drilled in the compli-

cated geological conditions of West Turkmenistan

with EDM2s3.

The second intermediate hole of 245 mm diameter

was drilled with the slant angle increase up to 22 at

a depth of 3441 m in the well 1630, up to 29 at a

depth of 3426 m in the well 1631, and up to 40 at a

depth of 3346 m in the well 1632. Casings were run

to these depths and cemented to the surface. In inter-

vals of 3450-3510

m

(1630 well), 3426-3606 m (1631

well), 3346-3603 m (1632 well) drilling with an

increase of zenith angle was continued. The zenith

angle in these wells achieved respectively 85.0

86.5,

86.6 ,

and this provided for bringing the borehole

into the horizontal position in the top intervals of the

low red-coloured soils section.

The combined production casing of

140 x 146 x 168 mm diameters were run to depths

of 3653,3606 and 3603 m respectively.

In the process of drilling the first horizontal wells

with E D M, casing programs were verified, effective

drilling conditions and bottom hole assemblies for

each hole interval providing for the required project

profile were determined.


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r411 NEW DRILLING TECH NOLO Y 187

TABLE

IV

Technical and economical drilling indices

Wells

Indices Vertical Horizontal

Number of wells compared 8

3

Average well depth, m 3655 3621

Number

of

bits, pieces 67 65

Penetration per bit, m

54.2 56.3

Penetration rate, m/h

4.80 4.67

Bit run speed, m/h

2.72 2.64

Cost of 1 m drilled,

100 195

From the results of these drilled wells the technical

project of drilling horizontal well no. 1634 and sub-

sequent ones with

EDM

was made. In Table IV there

are given technical and economical indices on verti-

cal and horizontal wells, drilled with

EDM

in the

Koturdep area during the period 1989-1992. Data in

this Table show that the main technical horizontal

drilling performances with EDM penetration rate,

bit run speed, penetration per bit) are at a level of

corresponding performances for vertical wells drilled

with EDM. The cost of

1

m drilled of

a

horizontal

well is 2 times that of the vertical one.

Oil and gas output from wells 1630 and 1632 are

given in Table V

2

cientifically based drill ing practices

for horizontal boreholes penetrated wit h

the electric downhole motor

It was noted before, that in horizontal drilling drill

string hanging up took place. Data on bit weights,

set up a t the wellhead and used a t the bottom hole of

the well 1632 are given in Table VI.

TABLE

V

Oil and gas output of wells

Pressure, MPa

No.

of

well Choke dia. mm Wellhead Bottom hole Oil, t/day Gas, ths.m3/day

1630 3.5

6.0

8.0

10.0

1632 6.0

7.0

8.0

9.5

16.7

15.0

13.6

11.0

9.6

8.8

8.6

7.2

21.0

15.2

15.1

12.5

14.3

13.2

12.2

11.4

60

145

257

345

45

62

101

106

6.2

14.7

27.6

29.9

41.6

49.8

56.8

66.3

TABLE

V

it

weight in well 632

Angle at the beginning

of the interval, degrees

Bit weight, kN

Weight indicator Calculated according to

Interval, m recordings current

of EDM

3351-3367

3367-3392

3392-3408

3408-3427

3427-3443

3443-3462

3462-3480

3480-3509

3509-3537

3537-3559

3559-3575

3575-3603

40.3

47.5

52.3

58.5

65.2

69.5

78.4

77.5

83.3

82.5

83.0

82.6

82

82

81

83

84

83

83

83

83

84

86

86

250

450

425

525

525

525

450

325

225

225

175

200

180

200

200

200

220

250

180

200

160

180

150

120


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NEW DRILL1

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TECHNOLOGY

Calculations made by us with the use of Herst

method7, show that the tendency of the drill string

hanging-up in the process of drilling was not acci-

dental. It was the result of the technology applied

and it would remain in drilling of subsequent wells.

The evaluation according to Herst consists in

defining the exponent

H

in the formula:

1)

R

;).

R max

x

min

x

In the case, when values 0.5

Drilling a horizontal well using an electric downhole motor

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