Gohfer-培训英文课件8-proppant-transport

Proppant

Transport&

Screenout

BehaviorR.D.

BarreeProppant

Transport&

Screenout

1©

2009In

this

session

…•

Look

at

traditional

proppant

transport

and

its

assumptions•

Look

at

common

remedies

for

early

screenout•

What

factors

actually

affect

proppant

transport?©

2009In

this

session

…•Look2©

2009Proppant

Transport

&

Settling•

Simple

models

assume

1‐D

flow

and

model

single

particle

settling

(Stokes’

Law)•

Fluid

and

particle

velocity

profiles

are

much

more

complex

in

3‐D

flow.–

Slurry

density

gradients

cause

gravity

under‐running,

fluid

shear,

and

non‐homogeneous

concentration

profiles.–

Fluid

properties

and

leakoff

cause

transverse

particle

migration–

Lateral

particle

motion

changes

transport

and

leads

to

screenout©

2009Proppant

Transport

&

Set3Traditional

Prop

TransportFrac

height(assumed

to

beconstant)Suspended

proppant

slurry(uniform

concentration)Clean

pad

fluid

tocreate

w=3-6xd

Fracture

half-lengthSettled

sand

bank

©

2009Traditional

Prop

TransportFrac4©

2009

Common

Assumptions:

Fluid

Loss/Transport/Screenout•

Proppant

is

homogeneously

distributed

–

Vertically,

laterally,

transversely•••••Sand

and

fluid

travel

togetherPad

is

required

to

open

width

for

sandPad

is

depleted

by

leakoffScreenouts

caused

by

prop

bridgingProp

concentration

increased

by

leakoff

False

assumptions

lead

to

failed

remedies©

2009 Common

Assumptions:

•5Common

Remedies

for

Early

Screenout

(If

caused

by

pad

depletion

and

bridging)•••••Pump

more

pad

volumeIncrease

pump

rateUse

higher

viscosity

fluidsUse

smaller

proppantsUse

fluid‐loss

additivesSometimes

they

work,

and

sometimes

NOT!

©

2009Common

Remedies

for

Early

Scre6©

2009Factors

Affecting

Proppant

Transport•Particle

velocity

profile

in

fracture•Concentration

distribution

across

fracture

width•Slurry

viscosity

increase

with

solids

addition•Single

particle

“Stokes”

settling

velocity•“Hindered”

particle

settling•Convection

from

slurry

bulk

density

gradients•Proppant

holdup•Proppant

bridging©

2009Factors

Affecting

Proppa7Cum.

Particle

Count©

2009

10.80.60.40.2

0Velocity

Distribution

of

Particles

Between

Parallel

Plates

1.20123456Particle

Velocity,

cm/secFor

a

uniform

particledistribution,

the

velocityprofile

is

given

by

thecumulative

frequencyplot.Cum.ParticleCount©

2009 1Vel8Cum.

Particle

Count©

20090.80.60.40.2

0

Particle

Velocity

Profiles

Normalized

to

Fluid

Velocity1.2

100.20.40.60.811.21.41.6Relative

Particle

VelocityCv=0%Cv=10%Cv=25%Cv=35%Cv=55%Cum.ParticleCount©

20090.8 P9Velocity,

cm/sec

Proppant

notHomogeneously

Distributed654321000.20.40.60.81Normalized

Slot

Width

©

2009Particles

at

high

concentrationParticles

at

low

concentrationVelocity,cm/sec Proppant

not610©

2009Single

Particle

Settling

Velocity

Predictions•

Terminal

settling

velocity

for

a

single

particle

in

an

infinite

fluid

body:–

Stokes

Law

for

laminar

flow–

Allen’s

Equation

for

transition

flow–

Newton’s

Equation

for

turbulent

flow•

Terminal

velocity

can

be

modified

for

multiple

particle

interactions.•

Wall

effects

can

be

considered

for

narrow

channels.

©

2009Single

Particle

Settling11(ρμ

)vt

=1.74d⎛

g(ρs

−

ρl)⎞⎜

⎟©

2009

Single

Particle

Terminal

Settling

VelocitiesStokes

‐

laminar

flow

regime

18μAllen

‐

transition

flow

regime0.721.180.20d(g(ρs

−

ρl)

ρl)

0.45

lvt

=0.5Newton

‐

turbulent

flow

regime

0.5⎝

ρl

⎠(ρμ)vt=1.74d⎛g(ρs−ρl)⎞⎜12Settling

Velocity,

cm/sec©

2009

0.10.01

0.0010.11Particle

Diameter,

inches

Single

Particle

Settling

Rates

in

a

1.0

cp

Newtonian

Fluid100

10

1

StokesAllenNewtonActual100

0.011250

40

30

20Mesh

SizeSettlingVelocity,cm/sec©

20013Settling

Velocity,

cm/sec©

2009

Single

Particle

Settling

Rates

in

a

55.0

cp

Newtonian

Fluid100

10

1

0.10.01

0.0010.11Particle

Diameter,

inchesStokesAllenNewtonActual100

0.011250

40

30

20Mesh

SizeSettlingVelocity,cm/sec©

20014©

2009

Slurry

Settling

Experiments

in

a

Vertical

Slot

Model•

Parallel

plate

model

5

feet

x

6

inches

x

0.25

inches•

30%

and

40%

PEG

solutions•

30/50

mesh

and

95

mesh

silica

sand

slurries•

Volumetric

concentrations

from

0‐55%

solids•

Slurry

settling

velocity

compared

to

Stokes

velocity©

2009 Slurry

Settling

Experi15Settling

Velocity,

cm/sec©

2009Solids

Concentration,

Cv

10.1Slurry

Settling

Rates

Controlled

by

Bulk

Density

Gradients

100

1000.10.20.30.40.5Vmeas(95)Vmeas(40)Stokes(40)Stokes(100)

Vcalc

0.010.001SettlingVelocity,cm/sec©

20016(

)

P

g

gh

f

c

f

ρ

∂

+

Δwa

μ

12vs

=©

2009Proppant

Movement

by

Bulk

Flow

or

“Convection”•

Convection[Phys]:”Transmission

of

energy

or

mass

by

a

medium

involving

movement

of

the

medium

itself.”–

McGraw‐Hill

Dictionary

of

Scientific

and

Technical

Terms,

Fourth

Edition∂z2For

fluid

flow

between

parallel

plates.()Pggh17©

2009

Thin‐Fluid

Transport

is

Different

From

Suspension

Transport

Proppant

drops

out

of

fluid

quickly.

All

solid

transport

is

in

a

thin

“traction

carpet”.Bank

height

builds

to

an

equilibrium

based

on

fluidvelocity.

A

clear

fluid

layer

is

maintained

above

thesettled

bank.

The

bank

advances

by

“dune

building”.©

2009 Thin‐Fluid

Transport

is18©

2009Video

of

Slick‐Water

Sand‐Transport©

2009Videoof

Slick‐Water

San19©

2009

Proppant

Bridging

and

Screenouts•

Proppant

particles

bridge

in

a

circular

orifice

3‐6x

the

particle

diameter•

Particles

bridge

in

a

slot

when

the

gap

equals

the

largest

particle

diameterStable

BridgeUnstable-FlowDismantles

Bridge©

2009 Proppant

Bridging

and

S20ΔPVariableSlot

WidthViewing

direction

in

video

©

2009Slurry

Inlet4-12

ppaSlurryOutletFracture

ChannelWidth

=

0.3”Variable‐Width

Slot

Apparatus

Model

Width=18”ΔPVariableViewingdirectionin21Slot

Bridging

Video•••••Flow

is

left‐to‐rightBorate

x‐linked

Guar

fluid8

ppa

20/40

Ottawa

sand

slurryBlack

16/30

ceramic

markersSlot

width

equals

maximum

(16

mesh)

particle

diameter

©

2009Slot

Bridging

Video•Flow

is

le22©

2009Proppant

Bridging

VideoCopyright

B&A©

2009Proppant

Bridging

VideoC23©

2009Summary

of

Bridging

Studies•

Bridge

stability

in

holes

and

slots

is

different•

Slurries

up

to

16

ppa

were

pumped

through

a

slot

1+

particle

diameter

wide•

Proppant

bridges

are

permeable

and

transmit

fluid

pressure•

Slight

opening

of

fracture

width

releases

bridge•

Bridging

alone

is

a

temporary

and

ineffective

screenout

mechanism©

2009Summary

of

Bridging

Stud24Annular

Flow

ApparatusOuter

wallAnnular

gapInner

wall

©

2009Frac

fluid

pressureLeakoff

pathInternal

pressureBottom

-Fluid

InTop

–Fluid

Out

FluidlossAnnular

Flow

ApparatusOuterwa25©

2009Proppant

Transport

in

the

Presence

of

Fluid

Leakoff•

Concentration

profile

across

slot•

Transverse

velocity

from

fluid

loss•

Migration

of

entrained

particles•

Force‐balance

on

particles

at

the

wall©

2009Proppant

Transport

in

th26©

2009Particles

Held

Dynamically

at

the

Fracture

Wall•

Particles

are

pulled

to

the

leakoff

site•

Transverse

fluid

velocity

generates

lift

and

drag•

Leakoff

velocity

imposes

stabilizing

gradient©

2009Particles

Held

Dynamical27©

2009Sand

“Node”

Formation•••••Flow

is

from

bottom

to

topFluid

is

typical

of

crosslinked

guarVelocity

is

1‐2

fpsProp

concentration

is

1.5

ppaFluid

efficiency

is

>90%©

2009Sand

“Node”

Formation•Fl28©

2009Node

Formation

at

Fracture

Leakoff©

2009NodeFormation

at

Fractu29©

2009Sand

Accumulation:

Low

CvLeakoff

Volume

*

Injected

ppaMass

of

Sand

in

Node©

2009Sand

Accumulation:

Low

C30©

2009Stable

channel

flow•••••“Node”

grows

in

lengthFluid

velocity

in

channel

erodes

sandChannel

dimensions

become

stableSand

held

in

place

dynamicallyNote

effects

of

inhibiting

leakoff©

2009Stable

channel

flow•“Nod31©

2009Dynamically

Stable

Channel©

2009Dynamically

Stable

Chann32©

2009Proppant

Holdup

in

Fractured

Systems

‐

Early

InjectionSlurry

injection

at

low

concentration

builds“islands”

or

“nodes”

of

packed

sand©

2009Proppant

Holdup

in

Fract33©

2009Proppant

Holdup

in

Fractured

Systems

‐

Continued

InjectionNodes

interconnect

and

leave

open

channels

for

all

injection

‐

minimalpressure

rise

noted

at

inlet©

2009Proppant

Holdup

in

Fract34©

2009Proppant

Holdup

in

Fractured

Systems

‐

Incipient

ScreenoutEntire

fracture

is

packed

except

for

narrow

flow

channel

<1”.

Screenout

occurs

suddenly

without

warning©

2009Proppant

Holdup

in

Fract35Q=T∂P/

∂L

∂W/

∂P~YME

©

2009

Interaction

of

Fissure

Opening

Mechanisms:

PDL,

Holdup

and

Storage

∂W/

∂PPDL

andStorage

Vp

VfQ=T∂P/∂L Interaction

of

Fissu36©

2009Effects

of

Proppant

Holdup•

First

proppant

in:–

accumulates

at

high

leakoff

sites–

becomes

immobile

at

the

frac

wall•

Later

injected

fluid:–

flows

in

localized

high

velocity

channels–

is

less

subject

to

heat‐up,

aging,

breaking–

remains

near

injected

prop

concentrationTracer

surveys

show

first

proppant

injected

remaining

at

wellbore.

Does

this

indicate

localized

high

leakoff?©

2009Effects

of

Proppant

Hold37©

2009Effects

of

Holdup

(cont.)•

Leads

to

short

propped

length•

Yields

a

non‐uniform

proppant

distribution•

Can

cause

near‐well

screenouts

and

perforation

plugging•

Can

be

linked

to

proppant

induced

pressure

increases•

Can

substantially

affect

final

conductivity

and

well

performance©

2009Effects

of

Holdup

(cont.38Proppant

Holdup

Factor

=

1.2©

2009Example

of

Proppant

Induced

Pressure

Increase

Modeling00:001/2/197000:10

00:20

00:3080007000600050004000300020001000

0A1614121086420B6543210CGOHFER

Bottom

Hole

Pressure

(psi)GOHFER

Slurry

Rate

(bpm)GOHFER

Bottom

Hole

Pressure

(psi)A

GOHFER

Surface

Pressure

(psi)AB

GOHFER

Surface

Prop

Conc

(lb/gal)A

GOHFER

Surface

Pressure

(psi)CACustomer:Well

Description:

TimeJob

Date:

Ticket

#:UWI:

00:40

1/2/1970

GohWin

v1.3.015-Mar-01

15:21ProppantHoldupFactor=1.2©

39©

2009Mitigating

Proppant

Holdup•

High

viscosity

gels–

Minimize

fluid

loss–

Deep

invasion

of

fracture

system–

Possible

severe

productivity

damage•

Particulate

fluid

loss

additives–

Must

bridge

natural

fractures–

Requires

low

permeability

to

stop

leakoff–

Can

minimize

invasion

of

fractures•

Altered

design

philosophy–

Use

clean,

non‐damaging

fluids–

Stay

below

critical

sand

input

concentration©

2009Mitigating

Proppant

Hold40©

2009Leakoff

Control

with

100‐mesh©

2009LeakoffControl

with

10041©

2009Fluid

Requirements

for

Transport•

Pad

volume:–

Not

determined

by

tip‐screenout

criteria

or

fluid

efficiency–

Unnecessary

in

water‐fracs

and

slick‐water

jobs–

How

much

is

enough?•

Fluid

stability–

How

much

viscosity

do

you

need?–

How

long

should

the

fluid

remain

“stable”–

What

temperature

profile

should

be

used

in

break‐test

design?–

What

are

the

implications

on

cleanup

and

production?©

2009Fluid

Requirements

for

T42©

2009Stagnant

FluidFluid

travels

through

small

channelsat

high

rate

with

little

residence

timeor

formation

contact

Variable

Fluid

Rheology

Leads

to

Channel‐Flow

and

Proppant

Bypass