Basics of Production Technology

8/10/2019 Basics of Production Technology

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BASICS OF PRODUCTIONTECHNOLOGY


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Density difference

Viscosity difference

Leads different shear stresses

Expansion of gas Leads Faster Velocity

Basics of Production Technology


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Since 1930, several Theories

Leads to Multiphase Vertical

Flow and Multiphase

horizontal flow



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1. Specific volume of fluid varies with pressure and

Temperature; small gas at the bottom & more at top

2. Energy loss due to Frictional, loss due to turbulence

& slippage loss due to specific weight difference.

Multiphase Vertical Flow-Distinguishing Features



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Affected by

1. ID, acceleration due to gravity, wetted angle on

pipewall, interfacial tension, etc.

2. Flow regime due to variation of press & temp.,

buoyancy, turbulence, inertia & surface tension.



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(i) Frictional loss varies inversely with ID.

(ii) Combined frictional losses of gas & liquid is morethan that of each phase individually.

iii) Varying heights of pipeline layout profile

iv) Flow pattern varies with pressure, temperature,flow velocity and rate.


Multiphase Vertical Flow-Distinguishing Features


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Pf Ps

FIG -1.2



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Producing Oil WellsMainly oil, Multiphase Flow

Producing Gas WellsMainly gas, very high GOR


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A plumbing system connecting reservoir drainage

boundary to the first stage separator at surface.

Several Nodes are formed. Inflow Curve (IPR) Measures Reservoir Capacity to

Produce.

Outflow Curve (TIC) measures ability to lift fluid to

surface.

Inflow/outflow intersection provides solution point or

natural flowing point.

Wellbore Hydraulics (Nodal Analysis) means:



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Reservoir Drainage area

Path Sector 4

Separator

Liquid out let

PathSector

3

Tubing

Path Sector 2

Path Sector 1

Gas

Schematic Diagram of different

Path - Sectors of fluid

flow from Reservoir to surface

Well head

Beam

Fig 1.4a



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Liquid RateLiquid Rate

PP

Decreasing GLRDecreasing GLR

Inflow Vs Outflow CurvesInflow Vs Outflow Curves

IPRIPR

00

Keeping THP ConstantKeeping THP Constant



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Multiphase flow (Vertical/Inclined), known as Outflow or

Tubing Intake Curve (TIC) Vs. IPR, known as Inflow.

Liquid

Rate

Fig. 1.4 (c)

P

OperatingPoint

IPR

TIC

Pwf

QL

Pr

QL max0

KeepingGLR & THPconstant


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Q max for Straight P.I. >> Q max for IPR

FIG.1.4-1 : Actual Case For P I

Pwf

q

STRAIGHT P.I . AND IPR

STRAIGHT P.I.

Q maxQ max

IPR

Pwf = Pr



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PR

E

S

S.

P

I

G

O

R

CUMM. PROD.

P I

FIG. 1.4-2 : Typical Performance For an Active Water Drive Reservoir

GOR

PRESSURE



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CUMM. PROD.

FIG. 1.4-3 : Typical Performance For A Solution Gas Drive

Field Reservoir.

RESV.PRESS

GOR

PI

PI

GOR

RESV.

PRESS.



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.

CUMM. PROD.

RESV.

PRESS.

GOR

PIGOR

P.I

RESV.

PRESS.

FIG. -1.4-4 : Typical Performance For A Gas cap Expansion DriveReservoir.



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RATE.

PRESS .

00

Pwf

Pb

qqmaxqb

JPb/1.8

VOGEL

BEHAVIOR

CONSTANT J

Pr

FIG.1.4-5: Combination Constant PI and Vogel Behaviour Case,

when Pr>Pb



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FIG. - 1.4-6 : Computer Calculated Inflow Performance

Relationships For A Solution Gas Drive Reservoir- Pattern of

IPR with Cumulative Recovery.

PRODUCING RATE , M3/D

Np/N = 0.1%

2 %

4 %

6 %

8 %

10 %

12 %

14 %

CUMM. REC.,

% OF

ORIGINAL OIL

IN PLACE



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INTRODUCTION ON ARTIFICIAL LIFT

CONCEPT OF PRODUCTIVITY INDEX

P.I = Q / ( Pr - Pwf )

Where ,

P.I = Productivity index.

Q = Total quantity of fluid.

Pr = Reservoir Pressure.

Pwf = Flowing bottom hole pressure.

Q Pr - Pwf

Q = K (Pr - Pwf)

K = Q / (Pr - Pwf)

Where K is a constant, known as PI

Pwf Pr

Pwf = Pr

Pwf

Pwf = 0

Q Qmax


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INFLOW PERFORMANCE

VOGELS WORK ON IPR :

From general IPR equation i.e.

J= qo/(Pr-Pwf)--------------- ( 1 )

WhenPwfis zero , theqobecomes maximum and denoted asqmax.

That is J = qmax / (Pr- 0)

or J= qmax /Pr----------------- ( 2 )

Contd.--------------


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Dividing equation ( 1 )by ( 2 )

J / J = qo/(Pr-Pwf) * Pr/ qmax

or qo / qmax =(Pr -Pwf ) / Pr

or qo / qmax =( Pr / Pr )-(Pwf / Pr )

or qo / qmax =1-(Pwf / Pr )since IPR curve below bubble point is not a straight line , he

created a parabolic equation from the above.

Contd.----------------

INFLOW PERFORMANCE


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He distributed {Pwf /Pr }in the following manner

20 % of{Pwf /Pr } & 80 % of {Pwf /Pr }

Therefore , the new equation is established as :-

qo / qmax = 1 - 0.2 {Pwf /Pr } - 0.8 {Pwf /Pr }

He then plotted dimensionless IPRs in two dimensional plane ,

where X- axisrepresents qo / qmax and Y- axisrepresents Pwf

/Pr Contd.----------------

INFLOW PERFORMANCE


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The minimum and maximum values qo / qmax and Pwf /Prin each case is 0 and 1.0.

Inflow performance relationship for solution gas drive reservoirs (afterVogel).

00

0.20

0.40

0.60

0.80

1.00

1.000.800.600.400.20

Pwf/Pr

qo / qmax

INFLOW PERFORMANCE


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STANDINGS EXTENSION OF VOGELS IPR

FOR DAMAGED OR IMPROVED WELL :According to him, flow efficiency is defined as :

F.E = Ideal drawdown/Actual drawdown

=(Pr - P'wf) / (Pr - Pwf) ---(1)Where,

P'wf = Pwf + (DP)skin

(DP)skindefined by Van Everdingen is as below :

(DP)skin= S q / 2kh

Contd.-----

PrPwf

(DP) Skin

So, Pwf = Pwf + (DP) Skin

INFLOW PERFORMANCE


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PREPARATION OF FUTURE IPR -

For planning future requirement of

Artificial Lift, Surface and Downhole

equipment



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IPR of Gas Wells

Qg= C (P2r

P2

f)n

C is a constant and it includes reservoir thickness,

permeability, temp., wellbore & drainage radii etc.

n depends upon turbulent flow near the well bore.



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Fig. 1.4.9 : Inflow Performance Curve of a Gas Well

(in log-log graph)

qg

(Pr2 P

f2)

102

100


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FLOW PATTERNS

+ Multiphase Correlations

+ Usefulness of multiphase Correlations

Basics of Production Technolgy


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MULTIPHASE FLOW

Number of flow regimes may be divided into two broad

divisions :

Where one phase is continuous.

Ex: Bubble , Spray & Froth flow.

Liquid is the continuous phase in bubble flow and gas is the

continuous phase in the other two.

Where both phases are continuous.


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SINGLE PHASE FLOW

Refers to one fluid medium only

MULTIPHASE FLOW

Refers to more than one fluid medium , for example

Oil , Water and Gas.

SINGLE & MULTIPHASE FLOW


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MULTIPHASE FLOW

HORIZONTAL FLOWVERTICAL /

INCLINED FLOW

STRATIFIED INTERMITTENT ANNULAR DISPERSED BUBBLE

SMOOTH WAVY SLUG ELONGATED BUBBLE

BUBBLE SLUG CHURN ANNULAR

MULTIPHASE FLOW

MULTIPHASE FLOW


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STRATIFIED SMOOTH FLOW(LOW GAS & LIQUID RATES - PHASES SEPARATED BY GRAVITY)

STRATIFIED WAVY FLOW(SAME AS ABOVE WITH RELATIVELY HIGH GAS FLOW RATE)

HORIZONTAL FLOW Fig2.2A

Fig-2.2B

MULTIPHASE FLOW


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INTERMITTENT SLUG FLOW(INTERMITTENT FLOW OF LIQUID AND GAS - GAS POCKETS DEVELOPES)

ELONGATED BUBBLE FLOW(SAME AS ABOVE ; EARLIER THAN SLUG FLOW, WHEN GAS RATES ARE

LOWER)

HORIZONTAL FLOW Fig-2.2C

Fig2.2D

MULTIPHASE FLOW

MULTIPHASE FLO

W


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ANNULAR FLOW

GAS OCCUPIES CENTRAL PORTION LIKE A

CYLINDER AND LIQUID REMAINS NEAR THE

PIPEWALL; CENTRAL PORTION ENTRAINSLIQUID DROPLETS. OCCURS AT VERY HIGH

GAS FLOW RATE.

HORIZONTAL FLOWFig-2.2E

MULTIPHASE FLOW

MULTIPHASE FLO

W


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DISPERSED BUBBLE FLOW

AT VERY HIGH LIQUID FLOW RATE, LIQUID

PHASE IS CONTINUOUS & GAS PHASE IS

DISPERSED ALL AROUND LIQUID IN THE FORMOF DISCRETE BUBBLES.

HORIZONTAL FLOW

Fig2.2F

MULTIPHASE FLOW

MULTIPHASE FLO

W


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BUBBLE FLOW

VERTICAL / INCLINED FLOW

OCCURS AT RELATIVELY

LOW LIQUID RATES.

MULTIPHASE FLOW

MULTIPHASE FLO

W


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SLUG FLOW


Symmetric about the pipe axis.

Gas phase -like a large bullet

shaped gas pocket with a diameter

almost equal to pipe diameter.

Gas pocket is termed

as Taylor Bubble.

MULTIPHASE FLOW

MULTIPHASE FLO

W


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CHURN FLOW


Similar to slug flow, though it is

chaotic with no clear boundaries

between the two phases.

Flow pattern is characterised

by oscillatory motion.

Occurs at high flow rates; liquidslugs become frothy.

MULTIPHASE FLOW

MULTIPHASE FLOW


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ANNULAR FLOW


Liquid film thickness is almost

uniform around pipe wall.

Characterised by a fast moving

gas core.

Liquid film is highly wavy due tohigh interfacial shress.

MULTIPHASE FLOW


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Effect of variables Line Size

Flow Rate

Gas-Liquid Ratios

WaterCut

Viscosity

Slippage

Kinetic energy term

MULTIPHASE FLOW

HORIZONTAL MULTIPHASE FLOW


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Effect of Variables - I

Pipe DiameterPressure loss (dP) decreases

rapidly with increase in Pipe Diameter.

Flow RateHigher flow rate increases dP

GLRIncreased GLR increases friction,

hence more dP, unlike to vertical flow.




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Effect of Variables - II

ViscosityViscous crude offers more

problem in horizontal flow mode.

Water CutIts effect is not pronounced.

SlippageIts effect is not pronounced.

Kinetic EnergyFor High flow rates & low

density it is considered for computation.




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Effect of variables Tubing Size

Flow Rate, Density

Gas-Liquid Ratio

Water Cut

Viscosity

Slippage ,Kinetic Energy term

Inclination Angle


VERTICAL / INCLINED MULTIPHASE


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Effect of Variables - I

Tubing SizeIt has pronounced effect in

deciding FBHP requirement..

Flow RateIt establishes the required

FBHP, which influences tubing size selection.

GLRIncrease GLR reduces FBHP requi-

rement, after a point reversal takes place.

FLOW

MULTIPHASE FLOW


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FLOWCORRELATIONS

HORIZONTAL

FLOW

VERTICAL

FLOW

INCLINED

FLOW

MULTIPHASE FLOW

VERTICAL / INCLINED MULTIPHASE


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Effect of Variables - II

DensityHigher density increases dP.

ViscosityHigher viscosity increases dP.

Water CutHigher watercut increases dP.

SlippageIt is observed during unstable flow region.

Kinetic EnergyFor High velocity & low density it is

considered for computation.

FLOW

MULTIPHASE FLOW


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VARIOUS ASSUMPSIONS TAKEN FOR

DIFFERENT CORRELATIONS :Fluid must be free from emulsion.

Fluid must be free from scale / paraffin build up.

Mashed or kinked joints should not exist.

Flow patterns should be relatively stable.

No severe slugging should occur.

Oil should not be very viscous.

U S OW



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CORRELATIONS

FOR

HORIZONTAL

MULTIPHASE FLOW

Lockhart & Martinelli Baker

Andrews

et al.

Dukler

et al.

Eaton et al. Beggs & Brill


MULTIPHASE FLOW


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VERTICAL FLOW

CORRELATIONS

Duns & Ros

Orkiszewski

Hagedorn Brown

Winkler &

Smith

Beggs &

BrillGovier

& Aziz

MULTIPHASE FLOW


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INCLINED FLOWCORRELATIONS

FLANIGAN

CORRELATION

BEGGS & BRILL

CORRELATION


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P

Decreasing GLR

Horizontal Multiphase Flow Gradient Curves

Flow line

Length

0

Min. Gradient Curve

Vertical / Inclined l Multiphase Flow Gradient Curves


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P

Increasing GLR

Vertical / Inclined l Multiphase Flow Gradient Curves

Depth

0

Min. Gradient Curve

Well Depth


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Vertical Flowing Pressure Gradients

(Courtesy: The Technology of Artificial Lift Methods By K.E. Brown)

FIG. 1.4-21(a)


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Horizontal Flowing Pressure Gradients

(Courtesy: The Technology of Artificial Lift Methods By K.E. Brown)

FIG. 1.4-21(b)

MULTIPHASE FLOW


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USEFULNESS OF VARIOUS CORRELATIONS :

Selecting tubing sizes.Predicting when the well will cease to flow.

Designing of artificial lift.

Determining flowing bottom hole pressures from the

wellhead pressures.

Determining the flowing bottom hole pressure, which

in turn help in determining P.I. of the well.

Predicting maximum flow rates possible.

Predicting whether the well is able to flow as per thepresent & future profile.


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Vertical/Horizontal Gas Flow

Mostly gas with little oil.

Basically flow of gas offers resistance to flow

in both vertical and horizontal conduits & in

that respect it differs from that with oil flow.



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Assumptions

Acceleration is negligible

Flow is steady & isothermal

No work done by gas

Equations are developed, like Weymouth equation for

horizontal flow, Hagedorn & Brown for Vertical Flow.


Basics of Production Technology

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