STUDY OF SPECIFIC ENERGY METHOD OF BIT SELECTION ON THE BASIS OF DRILL BIT …€¦ · ·...

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International Journal of Mechanical Engineering and Technology (IJMET)

Volume 6, Issue 10, Oct 2015, pp. 103-114, Article ID: IJMET_06_10_012

Available online at

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=6&IType=10

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication

STUDY OF SPECIFIC ENERGY METHOD

OF BIT SELECTION ON THE BASIS OF

DRILL BIT-DEPTH DATA IN UPPER ASSAM

OIL FIELDS

Mrinmoy Jyoti Borah

Department of Petroleum Engineering

AMET University, Chennai

ABSTRACT

Drilling bit is the most important and crucial tool for smooth and

economic drilling of an oil well. Achieving the desired rate of penetration with

the least possible bit wear and minimal hole problems is the goal of every

drilling engineer. Drilling engineers deal with many challenges before and

during drilling a new well even in a known area. There are many parameters

related to hardware and daily operations that are planned and also modified

as the drilling progress. Bit selection is one of the important parameters for

planning and designing a new oil or gas well. The aim of this research work is

to study and compare the performances of different drill bits in similar

formations by specific energy method of bit selection.

Key words: Drilling, Drill bit, Rate of penetration, Bit selection.

Cite this Article: Mrinmoy Jyoti Borah. Study of Specific Energy Method of

Bit Selection on The Basis of Drill Bit-Depth Data In Upper Assam oil Fields,

International Journal of Mechanical Engineering and Technology, 6(10),

2015, pp. 94-102.

http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=6&IType=10

INTRODUCTION

Once it has been established that a potential oil-bearing structure exists, the only way

of confirming the existence of oil is to bring the oil to the surface and to do this we

have to drill a well. The process is called drilling and one of the most important

equipment used in this process is called drill bit. The drill bit represents the heart of

the drill string. The bit is the tool on the bottom of the drill string assembly that

actually drills the formation.

Achieving the desired rate of penetration with the least possible bit wear and

minimal hole problems is the goal of every drilling engineer. Drilling engineers deal

with many challenges before and during drilling a new well even in a known area.

There are many parameters related to hardware and daily operations that are planned

http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=6&IType=7

Study of Specific Energy Method of Bit Selection on The Basis of Drill Bit-Depth Data In

Upper Assam oil Fields


and also modified as the drilling progress. Bit selection is one of the important

parameters for planning and designing a new oil or gas well. The selection of a proper

bit is a difficult task since the factors affecting the bit performance are complex

relationships between formation properties, bit hardware design and operational

parameters.

A worldwide review of drilling performance has shown that 10 to 40% of the dry

hole cost of a well is mostly bit related which makes bit selection a vital issue. The

right rock bit for the right job cuts the cost of drilling. There are thousands of drilling

bits available in the market. Right selection of drilling bit is a very important thing to

get the best drilling performance and to reduce the cost of drilling. Correct bit

selection is becoming increasingly important; given the high cost of drilling a well

and the possible lower return from it, every effort must be made to drill faster and

further with every bit used.

Bit Selection Methods

Technological advances in bit design and cutter technology are greatly assisting

drilling engineers in bit selection for any given application. Nowadays great emphasis

is also given to petro-physical properties of formations for selection of appropriate bit,

since these properties have direct bearing on bit life. Compressive strength analysis

has been widely accepted as a key formation property for determining the drillability

of formations. Leading bit manufacturers like Hughes, Smith, and Halliburton

manufacture and supply bits based on formation characteristics (Compressive

strength). This requires formation logs in digitized form as inputs which are fed in

their software for the manufacture of a particular bit suitable for the formation.

There are several conventional methods prevalent for bit selection. They are as

follows:

Cost per meter method.

Dull bit grading method.

Formation consideration method.

Offset bit record method and

Specific energy method.

As the study is completely based on specific energy method, we will concentrate on

the same.

SPECIFIC ENERGY METHOD

The specific energy method is a simple and practical method for the selection of bits.

Specific energy (SE) may be defined as the energy required removing a unit volume

of rock. The specific energy equation can be described by considering the mechanical

energy, E, expended at the bit in one minute. Thus,

E = W x 2πR x N. (I)

Where, W = weight on bit (lb).

N = rotary speed (rpm)

R = radius of bit (in).

Mrinmoy Jyoti Borah


The volume of rock removed in one minute is:

V = (πR2) x PR....................... (ii)

Where, PR = penetration rate in ft/hr.

Dividing equation (i) by equation (ii) gives specific energy in terms of volume as

=

= 10

in-lb/ (iii)

Replacing R by D/2, where D is the hole diameter, then equation (iii) becomes,

SE = 20

in-lb/

And in metric units,

SE = 2.35

MJ/

Where, W is in Kg; D is in mm; and PR is in m/hr.

Based on this method different drill bits having different IADC codes are

compared and their individual specific energy consumption is calculated in this study.

The bit that requires lowest specific energy for drilling is the best bit for drilling the

formation.

CALCULATIONS AND RESULTS

The study is divided into four cases viz. case A, case B, case C and case D. The cases

are classified on the basis of formation and bit size. The study was conducted on four

oil wells viz. BAGHJAN- 15, MKM-51, NHK-64, and MRN-116.

CASE A:

Formation: Sand/clay

Bit size: 12.15 inches

Type of Drilling: Directional Drilling

The study was carried out between BAGHJAN-15 and MKM-51.

Table 1 MKM-51

Type Of Bit Footage Per Day Cumulative Footage W In Kg N In Rpm

W X N Daily Bit Hrs Cumulative Bit Hrs Specific Energy

12.25inch In meters In meters

In MJ/

Bit type 1 397.536 397.536 8000 70 560000 12 12 127.5271402

527.424 924.96 8000 70 560000 29 41 232.2929065

533.32 1458.28 8000 70 560000 27 68 213.8817515

Bit Type 2 163.344 1621.624 8000 70 560000 15 83 387.9590711




SE

Cumulative footage

Graph 1 MKM-51

Table 1 shows the drilling bit-depth data from well MKM-51, where,

Bit Type 1is G-11FH (IADC: 1-1-7),

Bit Type 2 is G-12FH (IADC: 1-2-7).

From graph 1 it is clear that Bit Type 1 G-11FH (IADC: 1-1-7) with specific

energy 127.52 MJ/ with the other parameters has the lowest specific energy. It can

be accounted to the less daily bit Hrs. It should be noted that, though Bit type 2 was

signed for less footage per day and less bit hrs the specific energy consumption was

highest. Thus bit type 2 is not suitable according to specific energy method in this

type of formation. So let us check some other bit types in similar formations and

compare the suitability.

Table 2 Baghjan-15

Type Of Bit Daily Footage Cumulative Footage W In Kg N In Rpm W X N Daily Bit Hrs Cumulative Bit Hrs Specific Energy

12.25inch in meters in meters In MJ/

Bit type 1 479 479 16000 70 1120000 18.5 18.5 326.3352959

BIT TYPE 2 1297.896 1776.896 6000 95 570000 103 121.5 341.2573372

SE

Cumulative footage

Graph 2: Baghjan-15

Table 2 shows the drilling bit-depth data from well BAGHJAN-15, where,

Bit Type 1 is G11FH (IADC: 1-1-7)

Bit type 2 is PDC (Polycrystalline diamond compact) bit.

Mrinmoy Jyoti Borah


From Graph 2 it is clear that G11FH (IADC: 1-1-7) has lower specific energy than

PDC bit. But if we refer to table no 2, PDC bit was subjected to a high daily footage

but still the difference in specific energy between the two bits is just 15 MJ/ .

Result

If we compare both the wells, we find that G-11FH (IADC: 1-1-7) has the lowest

value of specific energy i.e. 127.52 MJ/ with the corresponding parameters (Table

1). But we also have to note that PDC bit with high daily footage, RPM, weight on bit

and highest daily bit Hrs consumes very less specific energy compared to the other bit

types. Thus, it can be assumed that a PDC bit with lesser footage, RPM, Bit Hrs will

consume much lower specific energy than G-11FH (IADC: 1-1-7). Thus from the

study we can say that PDC bit will prove to be suitable.

Now let us study the same formation (sand/clay) using the drilling-bit depth data

from the same two wells (BAGHJAN-15 and MKM-51) but with a different bit size.

The study was carried outbetweenBAGHJAN-15 and MKM-51.

CASE B:

Formation: Sand/clay


Type of well: Directional Drilling.

Table no 3 MKM-51


8.5inch in meters in meters

In MJ/

Bit type 1 5.904 5.904 4000 60 240000 5.5 5.5 2433.564169

53.136 59.04 3000 55 165000 9.5 15 321.0952723

251.904 310.944 4000 40 160000 27 42 186.6654334

BIT TYPE 2 503.808 814.752 3000 30 90000 47.5 89.5 92.36050091

BIT TYPE 3 738 1552.752 10000 50 500000 36 125.5 265.4797275

221.4 1774.152 10000 70 700000 37.5 163 1290.526453

246 2020.152 9000 80 720000 37.5 200.5 1194.658774

53.1 2073.252 10000 70 700000 3 203.5 430.4671288

SE

Cumulative footage

Graph no 3 MKM-51




Table no 3 shows the drill bit-depth data of a 8.5 inches bit in MKM-5 where,

BIT TYPE 1: SS-TMGP (1-1-7)

BIT TYPE 2: M1516 PX PDC

BIT TYPE 3: S 13GP (1-3-7)

From the graph, we get to know that M1516 PX PDC has the lowest specific

energy consumption i.e. 92.3 MJ/ in the whole drilling process. Now let us study

another well using 8.6 inches in same type of formation. After the study we can

compare between the two wells and analyze the optimum 8.5 inches bit for this type

of sand/clay formation.

Table no 4: Baghjan-15


8.5inch in meters in meters

In MJ/

Bit type 1 99.384 99.384 14000 75 1050000 19.25 19.25 2213.700079

BIT TYPE 2 57.072 156.456 14000 95 1330000 14.25 33.5 3614.586592

BIT TYPE 3 442.8 599.256 5000 90 450000 65.5 99 724.538423

BIT TYPE 4 47.232 646.488 14000 70 980000 14.5 113.5 3274.710875

43.2 689.688 12000 70 840000 12.5 126 2645.579229

BIT TYPE 1 10.824 700.512 12000 70 840000 4.25 130.25 1700.030287

SE

Cumulative footage FD

Graph no 4 Baghjan-15

Table no 4 shows the drill bit-depth data of 8.5 inches drill bit in Baghjan-15 where,

Bit type 1: G11FH (1-1-6)

Bit type 2: S13G (1-3-7)

Bit type 3: FC613 PDC

Bit type 4: HP43A (4-3-7)

It is seen that Bit Type 3, FC613 PDC has the lowest specific energy consumption

in the whole drilling process i.e. 724 MJ/ .

Mrinmoy Jyoti Borah


Result

After carefully comparing both the wells, it is seen that bit type 2 from MKM-51 i.e.

M1516 PX PDC consumes the lowest specific energy of 92.3MJ/ . It is to be noted

that in both the wells, PDC bit proves to be more optimum on the basis of specific

energy method. Thus we can say that for sand/clay formations in 8.5 inches bit size

category PDC bit proves to consume less specific energy and emerges as the most

suitable bit for drilling on the basis of specific energy bit selection method. Now let

us study a different type of formation using different sizes of drill bits.

CASE C:

Formation: sand/clay/coal/shale


Type of well: directional drilling.

The study was carried out on MRN-116 outfit: S8 and NHK-604 outfit: S-1.

Table no 5 MRN-116 outfit: s-8



In MJ/

Bit type 1 618.936 618.936 10000 80 800000 43.5 43.5 424.1732838

BIT TYPE 2 501.84 1120.776 10000 70 700000 59.91 103.41 630.4372941

351.288 1472.064 10000 70 700000 54.75 158.16 823.0546261

BIT TYPE 3 180 1652.064 15000 70 1050000 42.5 200.66 1870.318352

BIT TYPE 4 224.352 1876.416 15000 70 1050000 82.75 283.41 2921.710406

SE

Cumulative footage

Graph 5 MRN-116 outfit: s-8

Table no 5 shows the bit-depth data for MRN-116 outfit S8 where,

Bit type 1: G11FH (1-1-7) in sand/clay/coal

Bit type 2: G11FH (1-2-7) in sand/clay/coal

Bit type 3: XS4GS (2-1-7) in sand/coal/shale

Bit type 4: QH12S (4-3-7) in sand/coal/shale




From the graph it is seen that bit type 1 i.e. G11FH (1-1-7) has the lowest specific

energy i.e. 424.4MJ/ in case of sand/clay/coal formations.

But in case of shale formations bit type 3 i.e. XS4GS (2-1-7) has the lowest

specific energy. It should be noted that in shale formations the weight on bit increased

which requires more specific energy in drilling. As more weight on bit is applied in

formations, it directly adds up to the increase in specific energy.

Thus for shale formations, specific energy values are much higher.

Hence bit XS4GS (2-1-7) is more suitable than QH12S (4-3-7) while drilling shale

formations with the corresponding parameters according to specific energy method of

bit selection. Now let us study another well of same formation type using 12.25 inches

of bit for drilling.

Table no 6 shows you the drill bit-depth data of well no: NHK-604 OUTFIT: S-1

where,

Bit type 1: G11FH (1-1-7) in sand/sandstone

Bit type 2: PDC in sand/clay stone

Bit type 3: RC-137 in sand/clay/coal

Bit type 4: G12FH (1-2-7) in sand/sandstone/clay

Table 6 NHK-604 OUTFIT S-1


12.25 in meters in meters

In MJ/

Bit type 1 100.368 100.368 5000 60 300000 7.33 7.33 165.2874085

Bit type 2 139.728 240.096 3000 90 270000 18.33 25.66 267.2099327

Bit Type 3 459.528 699.624 6000 90 540000 35.34 61 313.2983714

343.416 1043.04 7000 90 630000 35.16 96.16 486.6073917

Bit type 4 296.184 1339.224 12000 90 1080000 33.59 129.75 924.0212875

SE

Cumulative footage

Graph 6 NHK-604 OUTFIT S-1

Mrinmoy Jyoti Borah


From the graph, we see that bit type 1 has the lowest specific energy as the bit hrs is

less. Bit type 2 i.e. PDC bit has the second lowest specific energy but more than type

1 due to more weight on bit. Bit type 4 has the highest specific energy because it has

the highest weight on bit. Thus we can say that the more the weight on bit, the higher

is the specific energy.

Result

By comparing the graphs we note that, for sand/clay/coal formations, RC-137 has the

lowest specific energy of 313.2 MJ/ with the respective parameters and proves to

be the optimum one. Again for sand/coal/shale, XS4GS (2-1-7) proves to be more

suitable with respective parameters.

CASE D:

Bit size = 8.5 inches

Formation: sand/clay/coal/shale

Type of well: Directional drilling

The study was carried out between MRN-116 OUTFIT: S-8 and NHK-604 OUTFIT:

S-1.

Table 7 MRN-116 OUTFIT: S-8



In MJ/

Bit type 1 110.208 110.208 9000 65 585000 33.75 33.75 1949.987117

BIT TYPE 2 125.952 236.16 13000 60 780000 48.09 81.84 3241.600806

Bit type 3 120 356.16 13000 60 780000 51.33 133.17 3631.615331

BIT TYPE 4 122.016 478.176 15000 60 900000 61.83 195 4964.096236

BIT TYPE 5 218.448 696.624 6000 80 480000 68.42 263.42 1636.407474

BIT TYPE 6 50.184 746.808 12000 60 720000 19.5 282.92 3045.208639

SE

Cumulative footage

Graph 7 MRN-116 OUTFIT: S-8




Table no 6 shows you the drill bit-depth data of well no: MRN-116 OUTFIT: S-8

where,

Bit type 1: G11FH 1-1-6

Bit type 2: RC 137 1-3-7

Bit type 3: S13G 1-3-7

Bit type 4: HP43A 4-3-7

Bit type 5: FC613 PDC

Bit type 6: Q30S 5-3-7

From the graph it is seen that bit type 5 i.e. PDC bit has the lowest specific energy.

The highest specific energy is shown by bit type 4 which can be accounted to the

more weight on bit.

Table 8 NHK-604 OUTFIT S1 Type Of Bit Daily Footage Cumulative Footage W In Kg N In Rpm W X N Daily Bit Hrs Cumulative Bit Hrs Specific Energy

8.5inch IN meters IN meters

In MJ/

Bit type 1 69.864 69.864 8000 65 520000 11.75 11.75 951.9255488

BIT TYPE 2 203.688 273.552 12000 75 900000 47 58.75 2260.425216

BIT TYPE 3 307.008 580.56 3000 90 270000 48.83 107.58 467.4293904

BIT TYPE 4 93.48 674.04 12000 65 780000 36 143.58 3269.592434

BIT TYPE 5 175.152 849.192 13000 65 845000 10.5 154.08 551.3738021

31.488 880.68 15000 75 1125000 30.25 184.33 11763.81117

32.472 913.152 15000 65 975000 6.5 190.83 2124.340623

SE

Cumulative footage

Graph 8 NHK-604 OUTFIT S1

Table no 8 shows the drill bit-depth data of well no NKH-604 outfit S1 where,

Bit type 1: G11F 1-1-6

Bit type 2: S13GP 1-3-7

Bit type 3: FC 613 PDC

Bit type 4: HP21G 2-1-7

Bit type 5: 5177051 (4-3-7)

Mrinmoy Jyoti Borah


From the graph w e come to know that bit type 3 i.e. FC 613 PDC bit has the

lowest specific energy consumption.

Result

By comparing both the graphs we come to a conclusion that, FC 613 PDC has the

lowest specific energy consumption in this type of formation with a specific energy

value of 467.4 MJ/ . It is also to be noted that the weight on bit on FC 613 PDC bit

was less but daily footage was the highest among both the wells. Thus we can say that

PDC bit proves to be the most suitable bit in this type of formation with the respective

parameters on the basis of specific energy method of bit selection.

CONCLUSION

From the study we have come to know that, weight on bit, daily bit hours and footage

per day plays an important role in deciding the specific energy of a drill bit. From

graph 2 we have seen that even a PDC bit with more bit hours and footage per day

demands a more specific energy input. So in any formation, we can achieve an

optimum specific energy input only by balancing the other drilling parameters. Thus

selection of a drill bit on the basis of specific energy mainly depends upon the type of

formation. It is obvious that a harder formation will require more specific energy

input than a soft formation. Moreover, we also came to know that PDC bit is

generally used in deeper and harder formations. The main advantage, we got to know

from the study is that, PDC bit can withstand high weight on bit as well as used for

more bit hrs and more daily footage without affecting the specific energy

consumption significantly. But the main disadvantage of PDC bit is that it is costlier.

So it will add up more value in cost per foot method in bit selection .So while

choosing a bit we have to consider the economic factors too. Thus we can say that,

specific energy method alone cannot be used to select a drill bit for drilling a well. We

have to take into account the economic factors, formation factors, log data too. Thus

we can conclude that, specific energy method together with other factors like

formation, economic factors etc can be suitably balanced to get an optimum drill bit

for a particular formation.

This study of drill bit-depth data will help future drilling operations in the subject

basins and give a detailed outlook towards the specific energy method of bit selection

to the drilling engineers.

REFERENCES

[1] Drill bit- Depth data provided for four wells in upper Assam oil basins by OIL

INDIA LIMITED, Duliajan, Assam

[2] "Wolfram (mathematical software) website: Drilling a square hole".

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[6] Stephen Ambrose Morse US patent 38,119 Improvement in Drill-Bits.

Twist Drill Bit, Granted: April 7, 1863

[7] McMaster-Carr catalog (115th ed.), McMaster-Carr, p. 2440, retrieved

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[8] Oberg et al. 2000, pp. 829,846

[9] Oberg et al. 2000, p. 846

[10] Gillespie, Laroux (2008), Countersinking Handbook, Industrial Press Inc.,

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[11] "Center Drill Chart. I-logic.com. Retrieved 2014-05-10.

[12] McMaster-Carr, p. 2438, 116th edition.

[13] P. Govinda Rao, Dr. C L V R S V Prasad, Dr.D.Sreeramulu, Dr.V. Chitti Babu

and M.Vykunta Rao. Determination of Residual Stresses of Welded Joints

Prepared Under The Influence of Mechanical Vibrations by Hole Drilling Method

and Compared by Finite Element Analysis, International Journal of Mechanical

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[14] T. Prabhu and Mr. A. Arulmurugu. Experimental and Analysis of Friction

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http://www.i-logic.com/utilities/CenterDrills.htm

STUDY OF SPECIFIC ENERGY METHOD OF BIT SELECTION ON THE BASIS OF DRILL BIT …€¦ · ·...

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