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MINISTRY OF EDUCATION AND TRAINING

HANOI UNIVERSITY OF MINING AND GEOLOGY------------***-----------

PHAM DUC THIEN

Research on drilling fluid flow in well

drilling to enhance drilling efficiency

Major: Drilling and completion oil and gas wells

Code : 62.53.50.01

ABSTRACT OF THESIS

OF DOCTORATE IN ENGINEERING

HANOI - 2012


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Research finished at Department of Surface Mining

Engineering, Faculty of Mining,

Hanoi University of Mining and Geology

Supervisors:

1. Assoc. Prof. Dr. Cao Ngoc Lam,


2. Assoc. Prof. Dr. Vo Xuan Minh,


Examiner 1: Dr. Khieu Huu Bo

Examiner 2: Dr. Nguyen Van Minh

Examiner 3: Dr. Nguyen Van Ngo

This thesis is going to be defended at the council of doctorate thesis

examiners of Hanoi University of Mining and Geology(Dong Ngac commune, Tu Liem district, Hanoi)

On ……Date……

This thesis can be found at Hanoi National Library

or Library of Hanoi University of Mining and Geology


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PREFACE

1. Necessary requirement of research

In drilling well, there are many paramerters effect of drillingefficiency, as kind of drilling rig, application technology, driling

fluid. A mong of them there is a respect which effect on drillingefficiency is driling fluid circulation to separate and cutting transport

out of the hole.

Research on driling fluid circulation to know clean capable

bottom hole and cutting transport. If the regime of driling fluid floware sensible, the cutting are separated and transported efficiency out

of the hole.

For this reason, “Research on drilling fluid flow in wellbore toenhance effective drilling” is imperative and have sience and reality

meaning.

2. The research purpose of thesis

The thesis reseach on drilling fluid flow with three respect are:- Reseach on flow regime of drilling fluids in annulus and

drillingpipe, application of drilling fluids used in Nam Con Son and

Cuu Long basin.

- Reseach on cutting transport capable of drilling fluids flow invertical annulus segment and effect of paramaters on cutting

transport efficiency, application for drilling in Nam Con Son andCuu Long basin.

3. Objectives and Scope of Research - Reseach on flowing Newtonian and non Newton fluid flow in

annulus and drillingpipe.- Reseach on flowing of drilling fluids used to drilling well in

Nam Con Son and Cuu Long basins.- Reseach on cutting transport in annulus and effecting

parameters, application for drilling well in Nam Con Son and Cuu

Long basins.

- Reseach on cleaning bottom hole base on optimum bithydraulic with maximum horsepower and impact force.

4. Content and Mission of Research

- Reseach on flowing of drilling fluid flow in annulus and

drillingpipe, following:


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+ Establish friction pressure equtions of drilling fluid in lamilar

flow in annulus and drillingpipe, Newtonian equivalent viscousity of

now Newton fluid and regime flow;

+ Drilling fluid flowing in eccentric annulus;+ Determine friction pressure of drilling fluids in lamilar and

turbulent flow in annulus and drillingpipe;+ Collect pratical drilling data to determine flowing of drilling

fluids in annulus and drillingpipe;

- Reseach on cutting transport in vertical annulus segment with

respects:+ Determine essence of cutting transport in vetical segment

annulus;

+ Simulate determination effect of paramerters, as annulusvelocity, fluid rheology, fluid density, parlical density, cutting size,

rate of penetration on cutting transport and losses of pressure.

- Reseach on cleaning bottom hole of drilling fluid flow,

contents:+ Establish horsepower hydraulic and impact force optimum

equations of drlling fluid flow through bit nozzoles;

+ Simulate determination horsepower hydraulic and impact

force optimum with change of paramerters as flowrate, fluidrhealogy, rate of pemetration.

5. Research methodsTo perform the reseach contents, the thesis used some method of

reseach:

1- Theorytical of reseach: used some consumes, laws,

mathemathic to reseach on flowing of drilling fluids in annulus anddrillingpipe.

2- Collection and treatment pratical data wich used to drill in Nam Con Son and Cuu Long basins.

3- Build program and simulate determination by matlab sofware

to perform:

- Reseach on effecting of paramerters as annulus velocity, fluidrheology, cutting density, fluid density, and rate of pemetration on

cutting transport and friction pressure losses;

- Reseach on optimum cleaning bottom hole base on two

criterion are horsepower and impact force hydraulic of drilling fluidflow through bit nozzoles.


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6. Basic literature of thesis

- The thesis was build base on basic literatures hydraulic,

drilling fluids, drilling hydraulic, cutting transport, multiflow, and jet

flow wich were pushlished in and out counting.- In building thesis, the author used many literature about

drilling fluid, fluid rheology, cutting transport in vertical, deviate,horizontal well, bit hydraulic, eg, wich were published on journals in

and out the country.

- Base on knowledge and personal experience of the author in

science reseach and employment history in University of Mining andGeology

7. Defended points of thesis

1. In drilling wells in Nam Con Son and Cuu Long basin, mostdrilling fluid are lamilar flow in annulus and turbulent flow in

drillpipe.

2. The sensible annulus fluid velocity when cutting transport of

wells in Nam Con Son and Cuu Long basins are 0.7 to 1.3 m/s, theminimum annulus fluid velocity should not lower 0.4 m/s.

3. The optimum horsepower hydraulic criterion are only used for

low and medium deep of drilling, the optimum hydraulic impact

force criterion can use for high deep of drilling.8. Innovations of thesis

1. Propose logic mathermatic menthod to establish equationsfriction pressure loss for Newtonian, non Newtonian fluid flowing

through drillpipe and annulus well in lamilar regime. This from

translate non Newtonian fluid to Newtonian fluid by equivalent

Newtonian viscosity.2. When reseach on flowing of drilling fluid in annulus and

drillingpipe of drilling wells in Nam Con Son and Cuu Long basins,the author discovered most drilling fluids are lamilar flow in annulusand turbulent flow in drillpipe.

3. Propose a model and program simulate determination

efficiently of cutting transport, from that can to easy evaluateeffecting of parameters on cutting transport.

4. When simulate determination pressure gradient in annulus,

the author discovered in cutting transport drilling wells in Nam Con

Son and Cuu Long basin as the annulus velocity is increase up to 1.3m/s, the pressure gradient decrease and strong decrease at lower 0.4


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m/s. The interval annulus velocity have low pressure gradient is 0.7

to 1.3 m/s. The minimum shoud not lower 0.4 m/s.

5. The first time simulate determination optimum bit hydraulic

and propose condition application of optimum criterions, that is theoptimum horsepower hydraulic criterion are only used for low and

medium deep of drilling, the optimum hydraulic impact forcecriterion can use for high deep of drilling.

9. Scientific and Practical Significances

1- Scientific significances

- The thesis was reseached logic and full about mathermaticalwhen establish friction pressure losses equations of drilling fluid in

lamilar regimes flow. From that define flow regime of non

Newtonian fluids base on Newtonian equivelent viscousity.- Evaluation and illustration effect of annulus velocity, fluid

rheology, fluid density, cutting density, cutting size, and rate of

pemetration cutting transport in vertical segment well.

- Propose optimum hydraulic condition of drilling fluid flowthrough bit nozzoles and application range optimum bit hydraulic.

2 - Practical significances

- The thesis is basic for drilling engineer plan drilling program

10. Thesis structureThe thesis are content prefere, four chater, conlusions and

recommendations, and references. All the thesis are performed in150 page. There are 45 figures, 89 tables and appendix

Chapter 1

Literature review of reseaching on drilling fluid flow1.1. Introducion

Cutting transport and cleaning well is important in drillinginsustrial. According to history devlopment, there are many scientist

to be interested in reseaching. The reseaching to concentrate onflowing of fluid, kind of cutting transport, drilling fluid flow through

bit nozzoles.

There are mumerous mathematical and empirical models for the

prediction and interpretation of hydraulics of cutting transportmechanism. Common problems with most of these cutting transport

models include inaccurate prediction, when compared with the


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experimental results or insitu drilling results. Thus, a new

mathematiacl model is necessary to overcom some of the limitation

of the existing hydraulic model.

1.2. Literarure Review1.2.1. Experimental study

The literatures experimental study care about mud rheology,flow rate in annulus, cutting size, fluid viscousity, rate of penetration

in cutting transport and bottom hole cleaning.

1.2.2. Theoretical Study

The literatures theoretical study carried out cutting transportmodels include two layer, three layer hydraulic model in vertical,

transit and horizontal segment.

1.2.3. Jet bit hydraulic literaturesThe jet bit hydraulic literatures care about optimum hydraulic

paramerters and consumption pumb hydraulic horsepower.

1.3. Sumary and evaluate

Base on literature review about drilling fluid flow. There aresome problems need studying:

- General method to define flow regimes of drilling fluid with

dfferent rheology;

- Theoretical and general reproduce effective of paramerters oncutting transport in annulus.

- Reseach on flowing regimes of drilling fluids in drillingpipeand annulus.

- Determine pressures gradient of flowing drilling fluids when

cutting transport in annulus.

- Mathermatical development to find optimum bit hydrauliccondition and application condition.

- Determination sensible range of annulus fluid velocity and pratical application.

Chapter 2

Drillling fluids and flowing of drilling fuids in drillingpipe

and annulus2.1. Drilling fluids and rheology

2.1.1. Drilling fluids rheologyRheology is correlation of fluid shear tress and shear rate.

Almost drilling fluids are non Newtonian fluids, general following:


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2.1.1.1. Newtonian fluids

The Newtonian fluids are defined by equation:s

where: τ

- shear tress; s - shear rate; µ - Newtonian viscousity.2.1.1.2. Non Newtonian fluids1- Bingham fluid

The Bingham fluid is defined by equation

s py

where: y - yield point; s- shear rate; p - plastic viscousity.

2- Power law fuid

The Power law fluid is defined by equation:nks

where: k - consistence factor; n - flow index.

3 - Herschel Bulkley fluid (yield Power Law fluid)The Herschel Bulkley fluid is defined by equation:

n

y ks The API considered the power law fluid is standard fluid use in

oil field.

2.1.2. Paramerters practice rheology of driliing fluidsThe result of experimental [44]:

The water based mud has: τy = 2.2 Pa, k = 2.15 Pa.sn; n = 0.3858

The oil based mud has: τy = 4.35 Pa, k = 4 Pa.sn; n = 0.3561

Mojis [44] studied the water based fluids with two main typesare: water base mud with Bentonite and added, and Brines with

polymer and added. Water based mud with Bentonite base on basic

fluid (CLN). CLN: 15g Bentonite in 350 ml water + caustic soda.

Table 2.1. Rheology of drilling fluidsDrilling fluids

density

(kg/m3)τy (N/m

2) n k (Pa.sn)

CLN+KCl 1290 7.9033 0.48 1.612

CLN+KF 1171 9.74 0.3 2.71

KCl+PHPA 1200 1.62 0.74 0.06

KCl+Xanthan 1166 12.02 0.412 2.117

KF+PHPA 1166 0.91 0.763 0.03

KF+Xanthan 1172 13.172 0.478 1.491

The two types of salts used are KCL and KF, two types of


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polymers are Xanthan and PHPA, paramerters and drilling fluid

rheology were shown in table 2.1.

In VietNam, acording to data presented drilling fluids has many

kinds and performance in Bingham plastic model.Table 2.2. Rheology of drilling fluids in Nam Con Son basinOrdinal Drilling fluids Fluid density,

kg/m3

YP, N/m2

PV,Pa.s

1 SW/GEL/PAC 1114 8.1 0.0120

2 SW/GUAR GUM 1084 6.7 0.0210

3 VISKOPOL 1042 4.8 0.0235

4 VISKOPOL/PRE.BENTONITE 1090 8.1 0.0440

5 SW/POLYMER 1078 7.2 0.0120

6KCL/PHPA

1108 8.4 0.01607 PAC/CMC 1132 7.2 0.0190

8 GEL/VISKOPOL/PRE.BENTONIT 1120 9.1 0.0475

9 GEL/CMC 1048 5.7 0.0325

10 ANCO 2000 1132 7.4 0.0175

11 KCL/POLYMER 1084 6.0 0.0185

12 ULTRADRIL 1174 11.3 0.0305

Table 2.3. Rheology of drilling fluids in Cuu Long basinOrdinal Drilling fluids Fluid density,

kg/m3

YP, N/m2

PV,Pa.s

1 ULTRADRIL 1210 5.3 0.0315

2 SW HIVIS SWEEP 1042 1.0 0.0030

3 KCL/POLYMER/IDCAP D 1282 6.2 0.0235

4 KCL/IDCAP/MUD 1174 6.5 0.0180

5 SPUD MUD 1078 5.3 0.0080

6 SOBM 1234 8.1 0.0180

7 OLEFIN SOBM 1234 11.3 0.0175

8 SBM 1318 14.6 0.0200

9 NaCl/BRINE 1150 3.4 0.006010 RDIF 1150 8.6 0.0225

11 KCL/POLYMER 1108 6.9 0.0235

12 PREHYDRATED/BENTONITEHIVIS PIL

1019 4.6 0.0175

13 KCL/POLYMER/LCM 1108 8.4 0.0270

14 SW/GUA GUM/CMC 1150 10.3 0.0380

15 SW/GUA GUM/GEL/CMC 1090 6.7 0.0155

16 GEL/POLYMER 1090 4.8 0.0245

17GEL/CMC

1078 5.5 0.0155


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L

2

ip

ms2

v

D

l p

Re

7,18

D

2lg274,1

1

ip

9,0ip Re

25,21

Dlg214,1

1

2.2. Friction pressures losses in drilliingpipe and annulus

2.2.1. Friction pressures losses in drilliingpipe and annulus when

lamilar flow

To define relatively friction pressure with shear tress and piperadius, we considered the force active independent on fluids, fluid

flow in drilling pipe and annulus are concentric cylindrical shell.By force balance equations and develop mathermatical to define

friction pressure equations, the result obtained friction pressures

equations of Newtonian, Bingham, Power Law, Herschel- Bulkley

fluids in lamilar flow in drillingpipe and annulus.

2.2.2. Equivalent viscousity

By balance friction pressures equations of Newtonian and non

Newtonian fluids in lamilar flow, we obtain equivalent viscosityequations of non Newtonian fluids.

2.2.3. Flow regimes of non Newtonian fluids

The drilling fluid is lamilar flow when the Reynolds number

with equivalent viscousity lower 2320 and turbulent flow higher2320.

2.2.4. Friction pressure in lamilar flow

The Darcy-weisbach equation to define friction pressure losses

the Newtonian fluids in pipe:

where: pms - friction pressure losses; - friction factor; L - fluid

density.

When fluid flow lamilar, the friction factor is define byequation:

Re/64 2.2.5. Friction pressure losses when turbulent flow

There are some equations to define the Darcy friction factor, but

two equations used usually are:

Colobrook equation [30]:


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Tomita equation [30]:

where:ε

- rough of pipe.2.2.6. Friction pressure losses in eccentric annulus

2.2.6.1. Hydraulic diamerterIn lamilar flow, the hydraulic eccentric annulus contens two

area: lamilar and turbulent area. Heigh of the lamilar area depend on

eccentricity and radius ratio. In one area the hydraulic diamerters

equations are established.2.2.6.2. Friction pressure losses

Base on the hydraulic diamerters equations, the Reynolds

numbers and friction factors are determined.

2.3. Flow regimes of drilling fluids in drillingpipe and annulus

2.3.1. Pratical paramerters of drilling in VietNam

By studying the data about drilling paramerters from 2003 to

2010, contents 34 well in Nam Con Son basin, 73 well in Cuu Long basin, The paramerters are shown in table 2.4

Table 2.4 Drilling paramerters in Viet NamWell diameter Drillingpipe diameter Flow rate

inch mm inch mm gpm l/s26 660.4 5 127 10001100 63.169.4

17 ½ 444.5 5 127 6931033 43.765.212 ¼ 311.15 5 127 628855 39.653.98 ½ 215.9 5 127 500606 31.538.26 152.4 3 ½ 88.9 230245 14.515.5The average velocity in drillingpipe and annulus are determined,

the result are shown in table 2.5.

Table 2.5 The average velocity of drilling fluids flow indrillingpipe and annulus

Drillingpipe diameter,

mm

Fluid velocity, m/sWell diameter, mm

ouside inside va v p 660.4 127 108.5 0.19 0.21 6.83 7.51444.5 127 108.5 0.31 0.46 4.73 7.06311.15 127 108.5 0.63 0.85 4.29 5.83215.9 127 108.5 1.32 1.6 3.41 4.13152.4 88.9 70.2 1.21 1.29 3.75 4.01


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1n

n

n2n

e

8

n4

1n3k

vDRe

2.3.2. Determination of flow regimes of drilling fluids in drillingpipe

and annulus

Base on the average velocity of drilling fluid in table 2.5, fluidsrheology in table 2.1 to 2.3, equivalent viscosity, Reynolds number

of Dodge and Metzner. Determination program is shown inappendix. The Reynolds number of Dodge and Metzner for non

Newtonian fluids are define by equation [22]:

2.3.2.1.Drilling fluids with rheology n < 1- Drilling fluids flow in annulus

Table 2.7: Flow regimes of drilling flluid CLN+KCl in annulusDrilling

fluidva Equivalent

viscousity, Pa.sReynolds

number

Dodge and

Metzner

Reynolds

number

Flowregimes

0.19 0.21 0.5451-0.5175 240-279 125-145 lamilar

0.31 0.46 0.3566-0.2904 356-469 205-372 lamilar0.63 0.85 0.2146-0.1837 697-1100 463-729 lamilar1.32 1.6 0.1288-0.1165 1175-1575 1004-1345 lamilar

CLN+KCl

1.21 1.29 0.1139-0.1101 871-960 748-825 lamilar- Drilling fluids flow in drillingpipeTable 2.14: Flow regimes of drilling flluid CLN+KCl in drillingpipe

Drillingfluid v p

Equivalentviscousity, Pa.s

Reynoldsnumber

Dodge andMetzner

Reynolds

number

Flowregimes

6.83 7.51 0.0356-0.0339 26867-31037 13434-15518 turbulent4.73 7.06 0.0431-0.0350 15371-28255 7685-14127 turbulent4.29 5.83 0.0453-0.0386 13251-21121 6625-10561 turbulent3.41 4.13 0.0511-0.0462 9347-12507 4674-6253 turbulent

CLN+KCl

3.75 4.01 0.0388-0.0374 8763-9703 4382-4852 turbulent

2.3.2.2. Drilling fluids wich used in Nam Con Son and Cuu Long basins

- Drilling fluids flow in annulus


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L

Ls

D

p

sC

gd

3

4v

Table 2.25: Flow regimes of drilling flluid SW/GEL/PAC in annulus

Drilling fluid va Equivalentviscousity, Pa.s

Raynoldsnumbers

Flowregimes

0.19 0.21 0.08550.0834 13211497 lamilar0.31 0.46 0.20140.0194 544839 lamilar0.63 0.85 0.55020.5452 235319 lamilar1.32 1.6 2.29672.2934 5769 lamilar

SW/GEL/PAC

1.21 1.29 4.49334.4915 1921 lamilar- Drilling fluids flow in drillingpipe

Table 2.32: Flow regimes of drilling flluid SW/GEL/PAC in

drillingpipe

Drilling fluidv p Equivalent

viscousity, Pa.sRaynoldsnumbers

Flowregimes

6.83 7.51 0.09780.0900 844210084 turbulent4.73 7.06 0.13590.0950 42088934 turbulent4.29 5.83 0.14860.1125 34906264 turbulent3.41 4.13 0.18380.1539 22423244 turbulent

SW/GEL/PAC

3.75 4.01 0.11310.1065 25932944 turbulent

Acording to the simulation results from table 2.4 to 2.19 for

drilling fluids with rheology three parameters, table 2.20 to 2.43 for

drilling fluids used in Nam Con Son, Cuu Long basins with rheologytwo parameters, table 2.44 to 2.45 for water show that drilling fluid

lamilar flow in annulus, turbulent flow in drillingpipe. The water and

drilling fluid with viscousity equivalent water turbulent flow in

annulus.

Chapter 3

Reseach enhance efficiency of transport in drillingpipe and

annulus

3.1. Slip velocity and drag coefficient

3.1.1. Slip velocity

Slip velocity is falling of solids in static fluids. The forces on thesolids spheres falling in static fluidds content: Drag force, gravity

force, buoyancy force. By force balance equation, have:


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cosv

1v1

cosv

vR

a

s

a

tt

cosgAA

1Gradp ahd ms

a

where: vs- slip velocity, dp- solid diameter, CD- drag coefficient.

3.1.2. Drag coefficient

3.1.2.1. Newtonian fluidDrag coefficient is defined by three area with Shah’s equations.

3.1.2.2. Non Newtonian fluidsDrag coefficient is defined by three area with Mayer ’s equation.

3.2. Property of cutting transport in vertical segment well

Cutting transport in vertical segment well base on slip velocity

that performance of ratio transport:

Where: vt -transport velocity;va-annulus velocity; -deviation angle.3.3. Equations development

Balance force acting on flowing in annulus, have:

where: Gradp- pressure gradient;ms

-friction shear strees; - wetted

perimeter;hd

-effective density; g- gravity;Aa-annulus cross section.

3.4. Simulate determination effecting of paramerters on

efficiency of cutting transport3.4.1. Algorithm simulate determination

Step 1: Import the parameters: va, L , s , n, d p,

Step 2: Calculate the drag coefficient, solid Reynolds number,

slip velocity by iteration method.

1- Assume the particle Reynolds number in one of three are:2- Calculate the drag coefficient respect;

3- Calculate the slip velocity;

4- Calculate the particle Reynolds number;Iterate from 2 to 4 until the particle Reynolds number between

previous and present values are approximate.

Step 3: Calculate the transport velocityStep 4: Calculate the transport ratio

3.4.2. Simulate determination principle


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0

0.1

0.2

0.3

0.4

0.5

0.60.7

0.8

0.9

1

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Annu lu s velo ci ty Va, m /s

T r a n s p o r t r a t i o R

t

0

0.1

0.2

0.3

0.4

0.5

0.60.7

0.8

0.9

1

900 1000 1100 1200 1300 1400

Drill ing fluid density, kg/m3

T r a n s p o r t r a t i o

R t

The simulate determination is performed by matlab sofware and

base on basic data in table 3.1. When run program simulate

determination, the parameters: annulus velocity, rheology fluids,

cutting density, fluid density, cutting size are changed in turn, theother paramerters following the basic data. The results of running

program was presented under part.Table 3.1. The parameters of basic data

Paramerters Value

Yeild tresse y 7,18 N/m2

Flow behavior index n 0,32

Consitancy factor k 1,37 Pa.sn

Hole diameter 311,15 mmOutside drillingpipe diamerter 127 mm

Cutting density 2600 kg/m3

Drilling fluid density 1100 kg/m3

Average cutting size 5mm

Rate of penetration 0,005556m/s (20 m/h)

3.4.3. Results and discusstionTable 3.4a: Rheology of drilling fluids

Rheology CLCS Fluid A Fluid B Fluid Cy (N/m

2) 7.18 7.18 7.18 7.18

n 0.32 0.32 0.32 0.32

k (Pa.sn) 1.37 0.5 1.0 2.5

L(kg/m3) 1100 1100 1100 1100

tdN (Ns/m2) 0.5327 0.1944 0.3889 0.9721

Figure 3.3: Cutting transport

efficiency following va in vertical

Figure 3.3: Cutting transport efficiencyfollowing fluid density in vertical well

with va= 0.7m/s


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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1600 1800 2000 2200 2400 2600 2800 3000 3200

Cutting density, kg/m3

T r a n s p o r t r a t i o

R t

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8 9 10

Cutting size, m m

T r a n s p o r t r a t i o R

t

From the result of simulation cutting transport efficiency when

change of paramerters showed that the increase in annulus velocity,

viscosity, flow behavior index, drilling fluid density leads to increase

cutting transport. The increase in cutting density, cutting size, rate of penetration leads to decreases cutting transport.

3.5. Simulate determination pressure gradient in annulus

3.5.1. Algorithm simulate determinationStep 1: Import the paramerters;

Step 2: Calculate Newtonian equivalent viscousity in annulus;Step 3: Calculate cross section annulus;

Step 4: Calculate the total of concentration;

Step 5: Calculate effective density;

Step 6: Calculate wetted perimeter;Step 7: Calculate the Reynolds number;

Step 8: Calculate friction factor;Step 9: Calculate friction shear tresseStep 10: Calculate pressure gradient


The simulate determination is performed by matlab sofewareand base on basic data in table 3.1. When run program simulate

determination, the paramerters: annulus velocity, rheology fluids,

cutting density, fluid density, cutting size are changed in turn, the

other paramerters following the basic data. The result of running program was presented under part.

Figure 3.8: Cutting transport efficiency

following cutting density in vertical wellwith va= 0.7m/s

Figure 3.10: Cutting transport efficiency

following cutting size in vertical well withva= 0.7m/s


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11000

11500

12000

12500

13000

13500

14000

0 0.3 0.6 0.9 1.2 1.5 1.8

Ann ulus v el oc ity Va, m /s

P r e s s u r e

g r a d i e n t i n

a n n u l u

s ,

P a / m

11000

11500

12000

12500

13000

13500

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Annulu s velo cit y Va, m/s

P r e s s u r e

g r a d i e n t i n a

n n u

l u s ,

P a / m

C LCS F luid A Fl uid B Fluid C

9000

10000

11000

12000

13000

14000

15000

16000

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Annulus velocity, m/s

P

r e

s s u

r e

g

r a d

i e n

t

i n

a

n

n

u

l u

s ,

P

a

/ m

Fluid density 950 kg/m3 Fluid density 1100 kg/m3 Fluid density 1300 kg/m3

10000

10200

10400

10600

10800

11000

11200

11400

11600

1800 2000 2200 2400 2600 2800 3000 3200

Cutting density, kg/m3

P

r e s s

u

r e

g r a d

i e n t i n

a n

n u

l u s ,

P

a / m

10000

11000

12000

13000

14000

15000

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Ann ulu s velo city , m /s

P r e s s u r e

g r a d i e n t i n

a n n u l u s ,

P a / m

Cutting density 2200 kg/m3 Cutting density 2600 kg/m3 Cutting density 3000 kg/m3

9000

10000

11000

12000

13000

14000

15000

16000

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Annulu s velocity, m/s

P r e s s u r e

g r a d i e n t i n

a n n u l u s , P

a / m

ROP= 0,002778 m/s ROP= 0,005556 m/s ROP= 0,008333 m/s

3.5.3. Result and discussion

Figure 3.12: Presssure gradient in

annulus of vertical well following va


annulus of vertical well following

drilling fluid rheology and va

Figure 3.19: Presssure gradient inannulus of vertical well following

cutting density with va= 0.7 m/s



cutting density and va


annulus of vertical well following rate

of penetration and va

Figure 3.17: Presssure gradient inannulus of vertical well followingdrilling fluid density and va


18/27

From the result of simulation on figure, we showed that there is

one point similar: In the low range of annulus velocity when increasein annulus velocity, the pressure gradient decrease. The increase in

annulus velocity to 1,3m/s the pressure gradient to minimum value.If continuos increase in annulus velocity, the pressure gradient

increase. The range of annulus velocity from 0,7 to 1,3 m/s leads to

sensible low value of pressure gradient and this range are sensible

annulus velocity to cutting transport. The other respect when theannulus velocity increase reach to 0,4 m/s, the pressure gradient

significant decrease. As the annulus velocity higher 0,4 m/s, the

pressure gradient decrease slowly. This presented that the decrease inannulus velocity reach to 0,4 m/s, the pressure gradient significant

increase. We can concludation that in drilling should not using the

annulus velocity lower 0,4 m/s.

- Pressure gradient of drilling fluids use in Nam Con Son, CuuLong basins

To define rule of changing between pressure gradient and

annulus velocity, the author simulate determination pressure gradient

as changing annulus velocity for some drilling fluids used in NamCon Son and Cuu Long basins

Simulate determination principle base on basic data in table 3.1and rheology of drilling fluid in table 2.2, 2.3.

The results of simulate determination was presented in tables

and figues following.

Table 3.25: Pressure gradient in annulus in vertical wellGradp, Pa/mva,

m/sVISKOPOL/

PRE.BENTONITE

KCL/POLYMER ULTRADRIL KCL/POLYMER/

IDCAP D

GEL/POLYMER

0,1 13530 13438 14446 15049 13462

0,3 12113 11970 13113 13809 11981

0,5 11909 11724 12902 13627 11725

0,7 11904 11679 12879 13618 11673

0,9 11969 11703 12923 13671 11692

1,1 12068 11762 13000 13753 11747

1,3 12188 11840 13097 13854 11823

1,5 12321 11931 13209 13967 11914

1,7 12466 12032 13331 14090 12015


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2

d

2

t

2

cCgA2

Q p

9000

9250

9500

9750

10000

10250

10500

10750

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Annulus velosity, m/s

P

r e s

s u

r e

g

r a d

i e n

t

i n

a

n

n

u

l u

s ,

P

a / m

CLCS Fluid A Fluid C

10000

10500

11000

11500

12000

12500

13000

13500

14000

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Ann ul us ve loci ty, m /s

P r e s s u r e

g r a d i e n t i n a

n n u l u s ,

P a / m

The tables and figures showed that rule of changing pressure

gradient drilling fluids with Bingham rheology same the drilling

fluids in part previous. This to asserted rule of changing between pressure gradient and annulus velocity.

- Pressure gradient in annulus with velocity when drilling fluidsnot cutting transport.

To addition clear, the author simulate determination pressure

gradient in annulus velocity when drilling fluids not bring cutting.

The result simulate determination showed that the increase in

annulus velocity, the pressure gradient increase.From this asserted that the equations were established to

determine effecting of paramerters on cutting transport areconfidency and essensibly.

Chapter 4

Reseach enhance bottom hole clean of drilling fluid flow

4.1. Reseach optimum condition to enhance bottom hole clean of

drilling fluids flow

4.1.1. Pressure loss across jet bitBy energy balance equation, we have:



drilling fluid rheology and va when non bring solid


vertical well annulus drilling fluid VISKOPOL/PRE.BENTONITE


20/27

bmstu p1

1 p

bctu p1

p

where: pc- pressure loss across jet bit; Q - flow rate; At - total area ofthe bit nozzles;C- Constant.

4.1.2. Optimum drill bit hydraulics4.1.2.1. Maximum drill bit hydraulic horsepower, optimum velocity

and nozzoles diameter

Horsepower hydraulic of drilling fluid through bit is defined by

equation: Hc = (p b – pdc – pms).Qwhere: Hc-Horsepower bit hydraulic; p b-pump pressure; pdc- pressure

loss across mud motor; pms- friction pressure losses.

To simple and can define maximum horsepower hydraulic ofdrilling fluid through bit, the friction pressure loss is described:

Q.C pms where: α- flow exponent

yields1

dc bc CQQ pQ pH

The horsepower hydraulic is the denpendent variable and is a

function of flow rate Q

Thus, by use of differential caculus, taking the first derivative ofHc with respect to Q and setting the equal to zezo, we have:

where:pmstu - optimum friction pressure loss; pctu- optimum pressure

drop across the nozzoles.The literature had been published [1], if Hc is know, then

optimum pump can be calculated by equationP btu = 3 Pms

According ro previous chapter 2, chapter 3, the total friction

pressure loss is defined by equation:Pms = Pmsa + Pmsp

where:pmsa - friction pressure loss in annulus; pmsp- friction pressure

loss in drillingpipe.


21/27

2

v

D

L

2

v

DD

L p

2

p

ip

L p

2

a

oph

hd ams

5

ip

2

L p

oph

22

op

2

h

2

hd a

2

msD

L8

DDDD

L8Q p

5

ip

2

L p

oph

22

op

2

h

2

hd a

mstutu

D

L8

DDDD

L8

pQ

.n

A2d tuntu

bd ctu p

1

g2Cv

Following Darcy-Weibach equation, friction pressure loss per

length L of hole well as

wherea

- friction factor in annulus in lamilar flow

p - friction factor in drillingpipe in turbulent flow

Substituting va; v p by Q, can be derived

When friction pressure is optimum, then flow rate is optimum, thus:

where Qtu; pctu are determined, we have:

ctu

2

d

2ctu

tu pgC2

QA

where:Atu- optimum total area of nozzoles

If drill bit have n nozzoles, the optimum nozzoles diamerter

Optimum velocity of drilling fluid through nozzoles bit is

4.1.2.2. Maximum jet impact force

Jet impact force of drilling fluid flow through bit nozzoles is

defined by Newtonian’second law of motion and give by

2

b CQQHBF


22/27

2

1 p p btuctu

2

p p btumstu

where: B - fator, g/2CBd

After differentiating and setting to zero yields

By the literature had been published [1], if Hc is know, thenoptimum pump pressure can be calculate by equation

P btu = 2Pms

The optimum flow rate, firiction pressure, nozzoles size, jetvelocity are defined same over part.

4.2.Simulate determination optimum bit hydraulic

4.2.1. Algorithm simulate determination Step 1: Import parameters

Step 2: Calculate cross section annulus, flow rate, drillingpipe

fluid velocity, annulus fluid velocity

Step 3: Calculate total concentration;

Step 4: Calculate Newtonian equivalent viscousity in annulusand drillingpipe;

Step 5: Calculate effective densityStep 6: Calculate wetted perimerter

Step 7: Calculate Reynolds number in annulus and drilling pipe

Step 8: Calculate friction factor ;Step 9: Calculate friction pressure losses;

Step 10: Calculate optimum pump pressure;

Step 11: Calculate optimum friction pressure;

Step 12:Calculate optimum pressure drop across the bit nozzolesStep 13: Calculate optimum flow rate

Step 14: Calculate total optimum area of the nozzoles;

Step 15: Calculate optimumn nozzoles diamerters;Step 16: Calculate optimum fluid velocity through the nozzoles;


The simulate determination is performed by matlab sofware and

base on basic data in table 3.1. When run program simulate

determination, the paramerters is changed. Simulate determination


23/27

for bit three nozzoles. The result of running program was presented

under part.

4.2.3. Results and discustion

4.2.3.1. Parameters of optimum horsepower hydraulic

0

10

20

30

40

50

60

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Deep of drill ing, m

P r e s s u r e ,

M P a

Friction pressure losses Optimum pump pressure

Optimum friction pressure losses Optimum pressure drop bit

Figure 4.7: Optimum parameters horsepower hydraulic following well deep

at va = 1,3 m/s

4.2.3.2. Parameters of optimum jet impact force

0

5

10

15

20

25

30

35

40

45

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Deep of dril ling, m

P r e s s u r e ,

M P a

Friction pressure losses Optimum pump pressure

Optimum friction pressure losses Optimum pressure drop bit

Figure 4.12: Optimum parameters jet impact force following well deep at va

= 1,3 m/s


24/27

4.2.3.3. Discustion

Fllowing the result of simulate determination, have some

comments:

- As the well drilled deeper, the optimum pressure pump,optimum friction pressure, optimum pressure bit drop, optimum flow

rate increase.- As the well drilled deeper rate of increasing the optimum pump

pressure are maximum and rate of increasing continuous decrease are

optimum pressure bit drop, optimum friction pressure

- As the well drilled deeper the optimum pressure pump for theoptimum horsepower hydraulic criterion very biger as the impact

force maximum criterion

- The flow rate increase, the optimum pump pressure, optimumfriction pressure losse increase.

- From the upper commentations and data in tables, we show

that the value of optimum pump pressure is very big, special in high

deep of well drill. The questions bring out are what condition toaplication optimum bit hydraulic.

The Sunnda Corporation [3], the maximum pump pressure is

5000 PSI (350 at).

Compare the maximum pump pressure and optimum pressure,we show that when optimum horsepower bit hydraulic at va = 1,3m/s

and 2500m deep of drillings (table 4.5, p btu = 35 MPa), the optimum pump pressure reach maximum pump pressure. On the other, when

optimum jet impact force at = 1,3m/s and 3500m deep of well (table

4.15, p btu = 34,8 MPa), the optimum pump pressure reach maximum

pump pressure. Therefore, the optimum horsepower bit hydrauliccriterion were only applied in low deep and medium deep of well,

the optimum jet impact force criterion can apply in high deep ofwell.


25/27

Conclusions and recommendatons

1. Conclusions

With results of research for drilling fluids flow in well drilling

base on two respect are improve cutting transport efficiency invertical segment well and cleaning cutting on bottomhole, the author

have some conclusions:1. Propose mathermatic menthod to establish equations friction

pressure loss for Newtonian, non Newtonian fluid flowing through

drillpipe and annulus well in lamilar regime. This from translate non

Newtonian fluid to Newtonian fluid by equivalent Newtonianviscosity.

2. In drilling wells in Nam Con Son and Cuu Long basin, most

drilling fluid are lamilar flow in annulus and turbulent flow indrillpipe.

3. The cutting transport efficiency increase as the annulus

velocity, fluid density increase. The cutting transport efficiency

decrease as the fluid viscousity, cutting density , cutting size, rate of penetration increase.

4. Significant parameters effect on cutting transport efficiency

are annulus fluid velocity and drilling fluid rheology. But cutting

transport efficiency are effected by parameters in situ as cuttingdensity, cutting size, and

5. Losses friction pressure of drilling fluid flow bring and non bring solid cutting are different. The drilling fluid flow bring solid

cutting as the annulus velocity is increase, the pressure gradient

decrease and then it increase. The drilling fluid flow non bring solid

cutting as the annulus velocity is increase, the pressure gradientincrease.

6. In cutting transport drilling wells in Nam Con Son and CuuLong basin as the annulus velocity is increase up to 1.3 m/s, the

pressure gradient decrease and strong decrease at lower 0.4 m/s. The

interval annulus velocity have low pressure gradient is 0.7 to 1.3 m/s.

The minimum shoud not lower 0.4 m/s.7. With parameters of circulation system was established, kind

of drilling fluid are known, we can find condition bit hydraulic

optimum base on three parameters are maximum horsepower

hydraulic, maximum hydraulic impact force, and velocity, diameterof jet bit optimum.


26/27

8. The optimum pressure pumb following horsepower hydraulic

criterion large biger hydraulic impact force. The optimum

horsepower hydraulic through bit are used for low and medium

depth, The optimum hydraulic impact force through bit are used forhigh depth.

2. Recommendatons

Base on the result of reseach, the author recommend:

- Continuos develope and perfect program, Algorithm simulate

determination;- Build model sofware have interface with user.


27/27

BIBLIOGRAPHY

1. Pham Duc Thien (2009). Application studied resultsdetermination of friction factor to calculate pressure losses of drilling

fluid flow though eccentric annulus. Scientific -Technical Journal of

Mining and Geology, No 27/ 7-2009. University of Mining and

Geology, Ha Noi.

2. Pham Duc Thien (2010). Effects of wellbore deviation on

cuttings bed formation in cuttings transport and cuttings bed anti-

sliding velocity. Meeting of Scientific 19th time, date 11/11/2010.

University of Mining and Geology, Ha Noi.

3. Pham Duc Thien (2011). Newtonian equivalent viscosity and

determination regime of non Newtonian fluid flowing through

drillpipe and annulus. Scientific -Technical Journal of Mining and

Geology, No 33/ 01-2011. University of Mining and Geology, Ha

Noi.4. Pham Duc Thien (2011). Optimum bit hydraulic. Scientific -

Technical Journal of Mining and Geology, No 34/ 4-2011.


5. Pham Duc Thien (2011). Effects of parameters on cuttings

transport in vertical and near vertical well. Scientific -Technical

Journal of Mining and Geology, vol 5, petroleum, No 34/ 4-2011.


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