The Selection of Optimized PDC Bits in the12 ¼”

Hole Section (Upper Part) of Gas Fields

Aryan Javanmardian Dana Bit & Down-Hole Co. / Drilling Optimization Dep., Tehran, Iran

Email: Javanmardian.aryan@danaenergy.ir

Vahab Hassani and Pedram Rafiee Dana Bit & Down-Hole Co. / Drilling Optimization Dep., Tehran, Iran

Dana Drilling Co. / Geology Dep., Tehran, Iran

Abstract—Selection of the optimized bit is the most

important factor to prevent the high Cost per meter and

approaching the long interval drilling and ROP. The goal of

this paper is to investigate the PDC bit performance in the

12 ¼” hole section From Hith-Eva.B for one of the gas fields

in Iran. The interval is mainly composed of thick white

anhydrite beds, dolomitic streaks and limestone. It was also

observed traces of cherts in the layers of gray claystone

throughout the interval. At this interval, the optimized one

is PDC with 8 blades of 13mm cutter size, Nozzle Quantity:

8 and 30.7 square inches Junk Slot Area. The average $/m is

good amount and ROP for this bit is 12 m/h respectively for

drilling 4 various wells. The most important feature for this

bit is related to hard formation with high compressive

strength. The recommendations that must be noticed for

this bit are manufactured based on matrix body with heavy

cutter layout density, Force balanced design ensures less

vibration while drilling, Special enhanced gauge protection

and dynamic flow simulating technology is used for

hydraulic design to ensure optimum bottom hole flow

pattern and anti-balling and benefit for increasing ROP.

Index Terms—PDC bit, optimization, cost per meter, rate of

penetration, bit nozzle

I. INTRODUCTION

The South Pars gas field was discovered in 1990. It is

located on the Qatar Arc in Iranian part of the Persian

Gulf approximately 100Km from Assaluyeh, 105 km

from Qatar and 330Km from Dubai.

The main Pars gas field is an anticline which its axis is

elongated and curved from the North (in Qatar) to the

Northeast. The flanks are dipping 0.5° to the Southeast

and 0.6° to the Northwest.

The hydrocarbon reservoir of the Kangan and Upper

Dalan Formations and equivalent to the Upper Khuff

reservoir in the Arabian plate contain some of the most

important gas reservoir in the Middle East region, as well

as the world. They are Middle-Late Permian to Early

Triassic in age and made up of cycles of carbonate-

evaporite deposits [1]. The Kangan-Upper Dalan

Manuscript received November 29, 2013; revised April 12, 2014.

successions in South Pars Gas Field (and also in the

North Field) include four reservoir units, respectively, K1,

K2, K3 and K4 with increasing depth [2].

A. Geology

Hith Formation from 1706-1850 MD: Hith

Formation is mainly composed of thick anhydrite

beds and thin dolomitic streaks. The age of this

formation is Upper Jurassic. 13 ⅜" Casing was set

10 meter Inside Hith Formation at 1716 meter.

Surmeh Formation from 1706-1850 MD: Surmeh

Formation is Middle to Upper Jurassic in age and

divided into 9 members as following:

Upper Surmeh Member from 1850 to 1974 MD:

This member is mainly composed of light brown

to cream dolomite and white amorphous anhydrite.

The Upper Surmeh Member is Upper Jurassic in

age.

Upper Dolomite Member from 1974 to 2081 MD:

This member is predominantly composed of

limestone and dolomite. There were also observed

some anhydrite at the top of this interval. The

Upper Dolomite Member is Upper Jurassic in age.

Upper Limeston Member from 2081 to 2272 MD:

This member is Middle Jurassic in age and is

composed of light cream to off-white limestone

inter-bedded with hard dolomite.

Cherty zone Member from 2272 to 2422 MD: This

member is Middle Jurassic in age and was entirely

composed of white to off-white limestone inter-

bedded with cream to light brown dolomite.

Middle Limeston Member from 2424 to 2594 MD:

This member is Middle Jurassic in age and was

entirely composed of limestone inter-bedded with

some dolomitic streaks. It was also observed some

black spots in lower part of this formation.

Mand Member from 2594 to 2776 MD: Mand

Member is Middle Jurassic in age. It is entirely

composed of limestone inter-bedded with some

gray to light gray dolomitic streaks in the lower

parts.

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Journal of Industrial and Intelligent Information Vol. 2, No. 4, December 2014

©2014 Engineering and Technology Publishingdoi: 10.12720/jiii.2.4.329-332

Email: {Hassani.Vahab, Rafiee.Pedram }@danaenergy.ir

Lower Limeston Member from 2776 to 2959 MD:

The age of Lower limestone Member is Middle

Jurassic. It is composed of light gray to cream

limestone and minor light brown to cream

dolomites in the middle part.

Lower Surmeh Shale Member from 2959 to 3075

MD: Lower Surmeh Shale Member is Middle

Jurassic in age. It predominantly is composed of

off-white to gray limestone inter-bedded with

argillaceous limestone, minor gray dolomite and

gray to dark gray elongated shale. Traces of pyrite

have been observed in some interval.

Lithiotis Member from 3075 to 3122 MD: The age

of Lithiotis Member is Middle Jurassic. It mainly

consists of light cream to light gray dolomite with

sucrosic texture. It was also observed some white

to off-white limestone and gray to dark gray

claystone.

Neyriz Formation from 3122 to 3162 MD: Neyriz

Formation mainly consists of gray to light cream

dolomite inter-bedded with thin streaks of

limestone and minor claystone. The age of this

formation is Lower Jurassic.

Upper Dashtak Member from 3162 to 3294 MD:

Upper Dashtak Member mainly consists of

crystalline dolomite inter-bedded with white to

gray argillaceous limestone. It was also observed

some white anhydrite in lower part and some gray

claystone in upper and lower parts of the member.

Evaporate B from 3294 to 3466 MD: Evaporite B

mainly consists of anhydrite with thin dolomitic

beds which becomes locally argillaceous towards

the base.

II. MATERIAL AND METHODS

This paper is to investigate and Compare the PDC bits

configuration and performance in the 12 ¼” hole section

From Hith till Eva.B (upper part of 12 ¼” section) for one

of the gas fields in South of Iran.

To achieve this approach, we will evaluate and select

the appropriate bit for the related hole section (12 ¼”

section, upper part) first and then the results of

experimental data (bit records) are shown at the second

level.

A. For First Approach (Theorical Approach)

Bits were selected with systematic approach from data

of original wells.

Each selection was evaluated in terms of

lithological characteristics by use of master, Sonic,

Gamma Ray logs when available [3].

Rock Mechanics characteristics, such as porosity,

abrasiveness, hardness, compressive strength,

plasticity were analyzed [2].

We used the mud logging data of another phase

that logs specifications are similar to considered

(papered) phase and import these data to Rock

Strength Analysis Software (ROCKY3.3) for

selecting the PDC bit generally.

Instantaneous ROP, weight on Bit, Speed, Torque

and other drilling parameters from bit records

were correlated with lithology.

Dull bits were analyzed [4]

Mud programs, casing programs and rig systems

were evaluated to improve performance

The analysis technique was effective. Because the bit

design was not altered significantly after the original

wells were drilled.

B. For Second Approach (Experimental Approach)

After selection the appropriate PDC bit, the running

operation was started and bit records were registered. The

characteristics of PDC bit selection are listed below:

Bit size: 12 ¼”, 8 Blade 13mm Cutter

Bit Specification:

Number of Blade: 8, Primary cutter size (mm): 13,

Nozzle Quantity: 8, Junk Slot area (in^2): 30.7, Body

Material: Matrix

Bit size: 12 ¼”, 7 Blade 16mm Cutter

Bit Specification:

Number of Blade: 7, Primary cutter size (mm): 16,

Nozzle Quantity: 7, Junk Slot area (in^2): 35.7, Body

Material: Matrix

At these bit records, various parameters are mentioned

such as Depth in, Depth out, Drilling Meters, Drilling

hours, Rate of Penetration, Drive procedure, Cost per

meter and the related formation.

Cost per Meter, a primary factor in comparing bit

performance in an unconstrained environment, becomes

only an indicator in today's constrained drilling market

[5].

The typical cost-per-Meter formula used to compare

the efficiencies of drilling operations is:

(1)

At the above formula:

During this investigation it was note that rotational

method (i.e., conventional rotary, Positive Displacement

Downhole Motor) had a significant impact on cost per

meter and drilling performance. The frequency and

severity of downhole problems, such as inadvertent pack

offs, stuck pipe and twist offs, tended to be functions of

certain bit/motor combinations. Historical drilling data

were used for optimal pairing of the rotational technique

with the proper bit type to achieve minimal cost per meter

[6] [7].

III. RESULTS

A. Results of First Approach (Theorical Approach)

We entered logging data including sonic data, Gamma

ray and formation density of another phase that similar to

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©2014 Engineering and Technology Publishing

the planed phase into Rock Strength Analysis software

(Rocky 3.3) and related results were received. The

considered interval depth is based on 1500m–2750m. As

you see at the rock strength analysis report, the UCS

(unconfined strength) of rocks for this interval is

approximately between 17000–28000 psi. For these

quantities of Rock UCS, regard to the bit selection

standards, we should select a PDC bit that appropriate

with hard formations and equal or more than 8 blades

regard to 13mm or 8 mm cutters size. At the next page,

you can mention the UCS, lithology, Sonic data and

Gamma ray diagrams from Depth of 2300m till 2500m

that Max. amount of the UCS are considered at this

interval.

B. Results of Second Approach (Experimental Approach)

For concerned 6 wells (Directional wells), according to

offsets and our analysis, we used 2 types of PDC bits

(item1 and item 2) and the result of bit running operation

is explained and shown at Table I-Table IV (Both bits

have been run with motor (7:8) lob configuration, same

BHA, same hole deviation and drilling parameters):

At starting of section 12 ¼” drilling operation, for one

well from Hith-Eva.b, we use PDC bit (Item 1). The

related record is shown at Table I (dull condition: lost in

Hole, because of BHA failure):

TABLE I. BIT RECORDS OF PDC BIT (8 BLADES,13MM CUTTER WITH

MOTOR ROTATION)

Type S/N Depth

(m) Hrs ROP $/M Inc IN Out

Item 1

(8b13c) A 1675 2817.0 1142 64.3 17.8 579.3 62

For second well from Hith-Eva.B, we used PDC bit

(item 2). The related record is shown at Table II (dull

condition: 5-3-BT-N-X-I-LT-PR):

TABLE II. BIT RECORDS OF PDC BIT (7 BLADES,16MM CUTTER WITH MOTOR ROTATION)

Type S/N Depth

in

Depth

Out Meters Hrs ROP $/M Inc

Item 2

(7b16c)* A 1620 2910 1290 268 4.8 1873.0 52

Regard to the above records, the PDC bit with 8 blade

of 13mm cutter (item1) is better than one (item 2). But

for more investigation about the PDC bit with 7 blade of

16mm cutter, we used new one again for another well and

the below records are mentioned at Table III (dull

condition: 1-3-CT-G-X-1/16-PN-HP):

TABLE III. BIT RECORDS OF PDC BIT (7 BLADES,16MM CUTTER WITH MOTOR ROTATION)

Type S/N Depth

in

Depth

Out Meters Hrs ROP $/M Inc

Item 2 (7b16c)*

B 1646 2546 900 91.8 9.8 1042.0 41

Regard to comparison of the above records, the

performance of the PDC bit (item 1) such as ROP, Cost

per meter are better than performance of PDC bit (item

2).In this reason, for the rest of wells from Hith-Eva. B,

we used PDC bit (Item 1). The records are shown at

Table IV

TABLE IV. BIT RECORDS OF PDC BIT (8 BLADES,13MM CUTTER WITH MOTOR ROTATION)

Type S/N Depth

in

Depth

out M Hrs ROP $/M Inc

Item 1 (8b13c)*

B 1686 3195 1509 124 12.2 775.0 50

Item (8b13c)

1**

C 1635 2915 1280 133 9.6 974.0 54.5

Item

(8b13c) 1***

D 1630 2920 1290 158 8.4 1072.0 52

Dull conditions of above items are explained below [4]:

(*): 4-1-BT-A-X-I-CT,RO-DTF

(**): 3-4-CT-A-X-I-BT-BHA

(***): 6-4-RO-A-X-I-PN,LT-PR

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©2014 Engineering and Technology Publishing

The below Diagrams (Fig. 1) show the brief of above

bit record for 6 various wells with lithology from Hith-

Eva. B (Hole 12 ¼”, Upper section):

Figure 1. Bit records for 6 various wells at 12 1/4" Hole section (upper part)

IV. DISCUSSION

The destination of this paper is to investigate and

Compare the PDC bit configuration and performance in

the 12 ¼” hole section From Hith till Evaporate B (Top

Section) for one of the gas fields in South of Iran. The

interval is mainly composed of thick white anhydrite beds,

cream to off-white dolomitic streaks and white to off-

white limestone. It was also observed traces of cherts in

the middle and layers of gray claystone throughout the

interval.

This paper has two approaches. The first one is related

to theoretical strategy that related data were calculated by

Rocky 3.3 and the bit design estimation was considered

regard to standard bit design and selection procedure. The

second approach was related to experimental data that we

used 2 types of PDC bits at 6 wells.

At this interval, the optimized one is related to PDC bit

with 8 blades of 13mm cutter size, Nozzle Quantity: 8

and 30.7 square inches Junk Slot Area. The average Cost

per Meter is good amount and Rate of Penetration for this

bit is 12 m/h respectively for drilling 4 various wells.

The results showed that, this bit is a good selection for

drilling the related interval (Upper part of 12 ¼” Section).

These results (theoretical and experimental Data) show

that selection of bit with 8 blades 13mm cutter is more

beneficial than bit with 7 blades 16mm cutter. The cost

per meter is a key factor for comparing two different bit

and it has been approved that the 8 blades 13mm cutter

PDC with the special features such as back cutters is the

most effective selection for this subject.

Now we investigate why this bit is appropriate for this

interval.

This bit type (Item 1) is appropriate for hard and

compact formation with very high compressive strength.

More features of this bit type (item 1) are described

below:

Matrix body with heavy cutter layout density.

Super hard cutter application makes bit capable to

drill high abrasive formation.

Force balanced design ensures less vibration while

drilling.

Special enhanced gauge protection.

Dynamic flow simulating technology is used for

hydraulic design to ensure optimum bottom hole

flow pattern and anti-balling and benefit for

increasing ROP.

Back cutter and back ream cutter features.

V. CONCLUSION

Selection of the optimized bit is the most important

factor to prevent the high Cost per meter and approaching

the long interval drilling and Rate of Penetration (ROP).

The optimized PDC bits in the 12 ¼” Hole section of gas

field for one of the phases in the south of Iran is 8 blades

of 13mm cutter size, Nozzle Quantity: 8 and 30.7 square

inches Junk Slot Area.

ACKNOWLEDGMENT

We are very thankful from Dana Drilling Company for

kindly cooperation.

REFERENCES

[1] H. Motiei, Stratigraphy of Zagros. End Edition Geological Survey

of Iran, Tehran, 2003. [2] P. Rafiee, B. Ziaee, and V. Hassani, Geological Completion report

of South Pars Gas Field. 2012.

[3] Schlumberger. [Online]. Available: www.slb.com [4] IADC Drilling Manual, 2000.

[5] T. B. Martin Jr. and D. McKinnell, Optimization of Bit

Performance for Qatar’s Offshore North Field, 1997. [6] J. V. Venrooy and J. D. Callais, New PDC-Bit Technology Proves

Cost-Effective in Drilling Oman Carbonates, 1997.

[7] V. P. Perrin and G. Mensa-Wilmot, A New Approach to Bit Performance Evaluation, 1997.

Aryan Javanmardian was born on 1986 in

Tehran, Iran that has a Master Science degree of

Mechanical Engineering from Iran University of Science & Technology on 2012. Aryan's major

field is related to the optimization of tools for

drilling operation. He is working at Dana's bit and Down-Hole Company as Senior Optimization

Engineer and he has worked at this company for

approximately 3 years ago. He has 2 Iranian industrial patents ''Patent No. 42998, Self-controlled silencer'', "Patent

No. 46417 , A type of

robot for painting the surfaces of metallic & non-metallic plates''. He is

attending at Iranian Elite Institute and Iranian Inventors Society.

Vahab Hassani was born on 1977 in Shahrood, Iran that has a Master Science degree of Geology from University of Tehran on 2003 while

accepted and graduated as top student. Vahab's major field is related to

the Bit operation and drilling optimization. He is working at Dana's Bit and Down-Hole company as head of bit operation and drilling

optimization and he has worked at this company approximately 5 years

ago while has experienced 6 years as senior optimization & evaluation engineer at ReedHycalog Co. he has one paper " Origin and brine

evolution and evaporate sedimentation in Chah Jam Playa" at 7th

symposium of geology society in Iran 2003" and one translation " surface geochemistry in petroleum exploration, 2002"

Pedram Rafiee was born on 1980 in Shiraz, Iran, that has PHD in

Geology from Islamic Azad University (Science and Research branch, Tehran, Iran). Pedram's major field is related to the geology for drilling

operation. He is working at Dana Drilling Company as senior geologists

of the South Pars Gas fields and he has worked at this company for

approximately 3 years while has experienced 8 years as a geologist at

Statoil, KPE Co.

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©2014 Engineering and Technology Publishing