SPE 13858 MS_Fracturing Without Proppant
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Transcript of SPE 13858 MS_Fracturing Without Proppant
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SPE/DOE
ociety
of
U.S. Dopartmtnt
Petrolwm Engineers
of Energy
SPE/DOE 13858
Fracturing Without Proppant
by T.R. Harper,* J,T. Hagan, and J.P. Martins, British
Petrdeurn Co.
SPE Member
Copyright1985, Sooietyof PetroleumEn9inaars
This paperwas presentedet theSPE/DOE 1965 LowPermeebiMyGee l+aaewoi~ held inDenver,ColoreUo,Mey 19-22, 19S5.The Material iasubjectto
mrraohn by the author. Permissionto copy is restrictedto an abstractOfnot more then S00 wds. Write SPE, P.O. SoxS2SS2S,Richardson,Texas
750sMSS6. Telex 7S0S8SSPE DAL.
MS ERACT
The recordsrefer to productionoperationsconducted
in ‘E@ami, mostly before 1W.
The resultsof fracturestimulation
.—------- .--1 -.---b A . ..4+h .mA w+
+hfi,, + m.nmn+ ~Z
Possiblereaaonswhy fracturingsrithout
Treamw3uw3
MIIPLCUU-IA4 W. . . . -U.. .& . .. . . . =.. rr--=
pmpparit may give rxse
~Q ~ ~Q~&J~ ~ ~v~ ~~~~el
agents in two reservoirain England are compared.
The‘effectupon the conductivity of proppant-fee
includeshear displacementbetweenopposingfracture
faces ao that a mismatchresultswhen the fracture
e-..+,,-..O* e
m~~~~ denarture
of the wellboreaxis
..e”.-.””“.
--=——-—.
=ttempts tQ clwee
In naturallyfractured
from a principalstress plane ia asseased.
reservoirs,large a ale block slidingand dilation
3
f jointsmay occu .
This investigationis
restrictedto reservoirswhich are not naturally
IREoDueTIoE
fracturedto any substantialdegree,and therefQre
does not considerthe block slidingmechanism.
In 1960 it was reportedthat wells in the
Los Angelesbasin had been
Yucc:eyr:ez;;u:;
AVAILABLEREPOETSOF PROPPAHT-FREBFRACTOIW
stimulatedwithout proppant.
sTIm3LATxon
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2
FRACTURINGWITHOUTPROPPANT
SPE
13888
,ecoveryattributableto proppedfracturetreatments
schedulesand proppant-freetreatments,both using
xceeded that achievedby proppant-freetreatments.
crude oil as the fracturingfluidand all conducted
.,-..+4,.-1 w,l.1 1.S
L.grnbert and Trevits2and Mahoney et a13
i~ v=. .AtimA .-A.*-.
eported proppant-freestimulationof the 2.2 feet
0.76m) thick Mary Lee coal bed at a depth of
Fracture stimulationtreatmentsin the
Egmantonand Eathemealloil fields were carried out
,pproximetely200 feet (366m). Mhoney et al
beportedthat the coal was brokan down with water
primarilyin the CarboniferouaNo.1 sandstoneGroup,
comprisingthe Crawshawand Sub-Altonsandstones.
,ndthen stimulatedat 2-6 bbl/minwith foam
In the Egmantonfield these formstionaare a series
incorporatingfluorescentpaint.
The magnitudeof
be nnmt-nt.imulnkinn rlmilvproduction was described
of channelsandstonesinterbeddedwith shales;up to
=... .---— ----- .---4
=--——-.—_—
v l.m.lA.+,...a.m+. .-- mmasam+ the +fi+.1hit-lrnanm
IS
acceptable. Minebackrevealedthat both vertical
f ====-UV=-~..- =.- Y---”-”
.“... ...-”..-”--
md horizontalsurfaceawere paint-stained
of the interbeddedsandstone-shalesequencebeing
;hroughoutan ellipticalarea and in part the
approximately20-25m.
These sandstoneunits are
largelycontinuousacroas the field. Any natural
‘ractureconaiatedof numeroueparallalsurfaces
fracturingwhich may be present is not obvious from
rithinthe naturallyfracturedcoal.
The authora
‘eportedthat fractureawere not propagatedinto the
cores but wells are verticaland bedding essentially
horizontal.
In the Bothamsallfield, the Sub-Alton
ltrataoverlyingthe coal bed.
Tnusp the desired
and Crawshawaandatoneato which stimulation
~eightgrowth controlwas achieved.
However,a
treatmentswere appliedtypicallyhave a
:omparableproppedfracturestimulationof smaller
permeabilityof less than lmd. Locationsof the
rolumer sul.tedin a greaterwell productivity
2
Bothameallwells, and the petrologyand diagenetic
.ncrease.
history of the N . 1 sandstoneGroup are shown in a
8
Freeman et a14 describeda seriesof
paper by Hawkins .
Litrogenstimulati=eatmants of shaly
Depthe of completedintervalavaried
Egmantonsthalation treatments
ormstions.
from2436 ft (742m)to 4470 ft (1362m). The shale
Initialatimulationein 1956 were
is reportedlynaturallyfracturedand production
Lncreaseawere achieved. No comparisonwaa made
performedby pumpingcrude oil direct to the
caaing.
IXI1957 and 1958,25 hydraulicfracture
rithsand-proppedfracturea.
Laboratoryteatsof
flowthroughfracturedsamplearevealedthat losses
treatment using 20-40 sand aa proppantand fluid
loss additivewere performed. Crude oil without
>f permeabilitywith change of confiningpressure
acrerepresentedby a higher gradientof
sand, but with fluid loss additive,waa again used
in 1958. All treatmentswere pumpedat
permeability/pressureor saw cut samplesthan for
approximately5-7bbl/min.
Intervalstreatedwere
~tural fractures. The authora relatedthis to the
typicallyin the range of 20-45ft (6-14m). Table 1
Zreatersize of asperitiesassociatedwith natural
Fractures.
Bloreover,ased on the shape of the
auzmarisesthe resultsof some
of
these
treatment. The resultsshouldnot be taken as
permeabilityv. confiningpressurerelationships,
theauthorsconcludedthat much of
the production
directlycomparablebecause of the variationof
near-wellboreconditions. Nevertheless,the results
Lossesassociatedwith drawdownof a well stimulated
by no-proppantfracturingwould occur early in the
in Table 1 indicatethat proppant-freefracturing
W=S g~n~~~~~v aucceesful
—-------— ;
antipLl~tiCUlar successwas
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SPE 1385S
T.R. Harper,J.?. iiagaiinti2.F. ii~=tirls
~
we of fluid loss additive. The crude oil smPle
Yom this well contained19$ by weight wax and a
meflush of wax diaperaantwas includedin the
subsequentfracturetreatmentwith proppant.
Fluid
.OSSadditiveand aand with a concentrationof
~pProxtitely 1.51bs/gallwere incorporated,and an
Lfterfluahof hot water.
The treatmentwas very
—s.-
,--------- -.--a..”+
... s..,.”l
mcceasxu~, ~ncrwae~u~
PL UUUCUAUU ..vIM ac
kmignificantamount to 500 gallonsper day of oil
;nd300 gallons per day of water.
However,the
?umpingrate in the treatmentwith sand was a factor
)f 1.3-2greaterthan the previoustreatment,and
khevolume of fluid twice as great.
It is
?easonableto asaume that the largertreatment
zonductedat a higher pump rate createda more
3xtensivefracture.
These resulte,therefore,do
lot demonstratethat the presenceof the aand acting
isa proppingagent was a criticalfactorin the
........ -e tbbe.nA +mam+man+.
.Wuu=-- “.
“-u- . ..-—.-..
J?othameallell No. 3 was drilledwith a
bentonite/watermud and completedin the Sub-Alton
3andstonewith perforationsfrom 3236-3248ft B.R.T.
(986-9901z) and 3254-3284ftB.R.T. (992-10C)lm);the
permeabilityof the upper zone was determinedto be
less than O.lmd, of the lower zone 10-25md.
Four stimulationtreatmentswhich can be
asmznedto have involvedfracturingwere conducted
overa period of some 10 years (Figure
4).
Treatment1 was curtailedfor operationalreasons
and only 18 bbls of
~rude oil were pumpedto the
formationthrough2 /8 inch drill pipe at a WHTP of
3800 psi (26 MPa).
Despite the smallvolume of
fluid pumped, the effectof this was to increase
productionfrom 1833 gallons,ofoi&?:r $aY (g.p.d.)
(6.9 m’/day) to 5375 8.p.d. (2-.3 m’ldaY),reducing
9
to a steady 1250 g.p.d. (4.7 m /day) of crude oil.
Well P.I. declinedby a factorof
successfullyarresteda productiondecline in the
first instance. Whether or not the pre-existing
fracturewae re-openedhas not been determined;the
major effectof the treatmentmay have been a result
of the chemicalsused in the vicinityof the sand
face. The final (proppant-free)fracture
stimulationemployedinjectionrates four times
L Lb-— L-_ ,---.
..* A---& ..- 4n ----“ A..1
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4
FRACTURINGWITHOUT PROPPANT
SPE 13858
Blockswere hydraulicallyfracturedwith
Fracturedasmpleaof Hopeman Sendstoneand
oil and 1.48 inch (37.5mm)plugs were cored through BirchoverGritstone(Table2) were tested in the
the fracturewith the long axie of the core lying
laboratoryat a range of ahear dieplacementa
withinor close to the plane of fracture. A
extendingfrom zero to 0.5 mm.
This was achievedby
confiningstreea differenceof not less than 1000
pai wae imposedduring fracturing. Sampleswere
placingone piece of approximatelysemi-circular
then cleanedby a toluene-methanolsequenceusing
perforatedsh~ materialof known thicknessat each
end of a sample,but on opposingsides of the
soxhletextractiontechnique.
The sampleewere
fracture. By this arrangement,the ahear
confinedin a Hock triaxialcell and simulated
formationbrine flowed to determineasmple
displacementia achievedat the outeet of the
permeability. The simple assumptionthat flow
experimentwithoutfrictionalslidingbetweenthe
opposingfractureaurfacea.
This is repreeentative
occurredindependentlyin the fractureand the rock
of the growth of a hydraulicfractureout of a
matrix (flow parallel to fractureplane), with a
principalplane.
Initially,when the fractureis
linearpressuredrop, was usetito calculatevalues
for fractureconductivity. Thus, the permeability
ellipticaland one axis is short,shear diaplace-
mente are small. As the fracturegrows, the ahear
of intact samplesof each material (withoutany
fracture)were teatedat a range of confining
displacementoccure in an open (negativeeffective
stress)condition.
pressures. These values for intactmaterial,Ko,
were subtractedfrom the Darcy permeability
The higher shear displacementswhich were
calculatedfor the fracturedeample,K, with the
includedin the teat programmeare appropriateto
appropriategeometricalfactorapplied to give a
value for fractureconductivity:
greater deptha,where stressdifferencesare
greater. For example,at 10,000feet (3050m), a
maximum atresadifferenceof 4000 psi - 5000 pai
& (K - Ko)
(27-34MPa) may be more common. This ie approx-
eK. =
J
(1)
imatelythree times greater than that used in the
above example,and for the same,geometryand
materialpropertiesa ahear displacementof 0.3 mm
where e K. = fractureconductivity(red.cm.), D =
$“
would be predicted.
Where wellboresare
cross-seclonal width of fracture (equivalentto
piug diameter).
intentionallydeviated,the value of shear
displacementcould be significantlygreater.
The range of shear displacementsof 0.1 -
THE EFFECTOF WEAR D18PLAC=03-FEACI’ORE
0.5mm wae chosen to be primarilyrepresentativeof
CONDUCTIVITY
subverticalwellboree. Referringto Table 2, it may
be noted that these values are of the order of one
It is highly improbablethat a wellbore
grain diameterfor the Hopeman sandstone. The
EirchoverGritstonegrain size range ia greater,and
,..
w1ll be driiied preciaeiyin a principaletrees
the range of shear displacementsimposedis of the
plane. Even where wells are intendedto be
order of the lower end of the grain size range.
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SPE 13858
T.R. Harper,J.T. Hagan and J.P. Martins 5
McGuire-Sikoratype of relationshipscan be used to
asseas the influenceon well productivityof such
~;;~~~a?~nductivit
y: formationpermeability
The laboratorydeterminationsyield a
fractureconductivity(darcyft.): formation
permeability(red)ratio of 0.01 - 0.1 for a 1 md
reservoir,or 0.1
- 1.0 for a 0.1 md formation.
The significanceof samplesize upon
observedpermeability,must how ver, be taken into
%
EscoiiGt.TaaEg SE* F;therspecllCc=clcd$tithst
large-scaleundulation(wavineaa),rather than the
small scale roughnesswhich is superimposedon the
waviness,controlsthe mechanicaland hydraulic
propertiesof fractures.
In the expertients
reportedhere, the maximum cross-sectionalwidth of
fractureavailablefor flow was only 37.5 mm.
If we
can ignore the possibilityof long term embedment,
or of pluggingby fines,a higher conductivityfor
fractureageneratedin the field than that observed
in the small samples in the laboratorymust be
assumed.
Unfortunatelyno definitionof the size
effectis ava lable. Based upon recognised
+
relationships, an order of magnitudeincreasein
fractureconductivitybetween laboratoryse=p:escf
sandstoneand field-scalefracturee
in
the East
Midlandawould representan approximateincreaseof
well productivityby a factorof 2-3 attributableto
no-proppantfracturing.
Therefore,if the outcrop
sandstone which were testedare assumed to be
approximatelyrepreaentativeof the Egm.sntonnd
Bothamsallreservoirrocks, it may not be necessary
to invokefracturingthroughskin damageor
“perforationbreakdown”as the reasonfor the
auccesaof the proppant-freetreatments. In cases
where increasesof well productivityapproachedan
order of magnitude,however, it is concludedthat
fracturingthroughdamage or into a more permeabie
fracturesinitiatein the plane of the wellboreare
conduciveto high shear displacements,but
subsequenteffectivenormal streaaesacting on the
fracturesare higher.
COECLUSIOMS
i.
2*
=---4 ---- -----4.” -s s..--+....: . . . .. +h ,. .. + . ,” ,, ,. .. .m+
rL-WVLUU~ &-CpUL-kZ5 WA LA~tibULLU6 “AWL”IA” pLWYp~AA.
are confined to naturallyfracturedreservoirs
and a reservoirhaving abrupt lateral facies
changee. The Egmantonand Bothameallfields are
not notably naturallyfractured,and at least in
the Egmantonfield the sandstonehorizonsare
largely continuousacross the field. A
comparisonof fracturingwithoutproppantand
fracturingwith proppantat low sand
concentrations,using crude oil as fracturing
fluid, demonstratesthe following:
a)
fracturingwithoutproppantwas effectively
used to increasewell productivity;
b) no evidencefor a more rapid decline in
well productivityafter fracturingwitinout
proppantrelativeto proppedtreatment
could be observedin the productiondecline
curves;
c)
the fracturetreatmentswith proppant(and
usually fluid leas additive)were more
effectivethan those without proppant.
‘theoreticalnd laboratorystudiessuggestthat
the conductivityof unproppedhydraulic
fractureais increasedas a resultof shear
displacementof a magnitudecomparableto a
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l?QArViTIRTNt? WTTHnIIT PRfIPP&NT
6
. .-- .”..-..- “------- ------ ----
SPE 13858
mlIEwLATmtE
K-
K“
D
e
v
u
x
c
al, U2
B
permeability
permeabilityof fracturedsample .
diameterof core plug
fractureaperture
Poi8son’sratio
shear displacement
distancefrom centre of fracturein plane
of fracture
fracturehalf-length
principal.9tresses,pproxhately vertical
and horizontal
inclinationof principalplane to plane of
fracture
A XUOULEDGEHEMTS
The authorswish to acknowledgethe
interpretationsand qualityof the recordsprepared
by Messrs. C.M. Adcock and J.H. Edwardsduring the
developmentof the Egmentonand Wthameall
oilfields,and the assistanceduring the
investigationof Mr. IL Milton-Taylerand also
Mr. p.
King. The
authorswish to thank the management
of the BritishPetroleumCompanyPLC for permissionL
publish this paper.
.—-”-
M6s.suGm
1.
2.
Ghauri,il.K.
Results
of
well stimulationby
hydraulicfracturingand high rate oil
backflushing,J. Pet. Tech., June 1980.
Lambert,S.W., Trevits,M.A. The feasibilityof
no-proppantstimulationto enhanceremoval
of methane from the Mary Lee @albed, U.S.
Dept. of EnergyReport of Investigation,
April, 1980.
APPEHDIX
A
F)TSPFACmEEIPS AT TEE -AI= (M’ A-——-—
?LAT
ELLIPTIC CRACK
The displacementsat the surface of an
elliptichole (FigureAl) in an infiniteelastic
medium are given by Jaegerend Cook . Using theirl
nomenclature,the displacementsare given by the
real and imagina~ parts of ths followingexpression
2G(UC + iUn)
“
[xdz -z7GT
-m [mT/w’ c l”2
Conaidera flat crack of length 2C (givenby 50 = O)
in which case $, $’,$ reduce to:
1
P C{cos 2
4’=72
+ i (1-COS~g’
---—-
‘ ” ‘
“TP2
4J=+P2
Cos 2 13- sin 2 S cot n-i(l-coa211)ot rI}
c {- sin 2 (rI-6)+ i (1-cos26)}cosec n
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NUMSER
OF TYPE OF FRACTURE
PRODUCTIONDURING
FACTOR
WELLS
STIMULATION “
ONE YEAR PERIOD
OF
(TONS)
INCREASE
IN
PRODUCTION
WITNOUT
GAIN AS
FRACTURE A RESULT
STIMULATION OF FRACTURE
STIMULATION
5
Crude oil without proppsnt
2348
1800
1.76
pumped direct to casing
15
Crude oil with proppant 5075 15968
4.15
pumped through drill pipe
4 Crude oil without proppant 414 2520
7.09
pumped through drill pipe
with fluid loss additive
TABLE 1. RESULTS OF SONE FRACTURE STIMULATION TREATMENTS CONDUCTED IN EGNANTON FIELD IN 1956 AND 1958
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./ \
Q
y-$=’
BOTHAMSALL
L
m
EGMANTON
—
SCALE
: 2040
eowml
F@. l- lace tion of Egmanton and 2othemeel l oi l f ie lds.
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a
a
g
c
(-J
-1000
-1
5
z
“’’”~
.—————————_-——_—_____
500
1 ------ ~. I--WQ-——
o
I
D
wELL7— __
———— ———__ —______
<
——— —____
——— ——_—J__
—————— ———— ___
JiFIMIAIMIJ1 JIAIS1OINIOJ lFIMr AI MIJIJ lAls 10 INlo
*
1958
1959
Fig. 3-Oecline cu vea before and ah propped fracture sfimulatbn in 1S5S inwelle in the Egmanton f ield previously
fracture.etimulefed without pmppant,
N
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,1 1
1 1 I I II
_.–’ .-,---- )’. -~, l.-l 1,1,
I I I I
I I
I
Ii Ill
I>, ’J. J ”)”.,--,. ,’1
1- I
,, /,----
,-., ,J
->
‘-, ,
, ,’. ” .
‘- ).-l-~ .
,-
,
,),’, -’ZJ, “-- -f~,
\-
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- .
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,. .
)
,- A’-’,, }J’ -,-J\ ,,
,-
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.-
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‘ I I
111’ l, l:\’.’--”.’ J- JJI’11’IIIL.C
lll l~l ~]l’,,’l.’-:) .’. )’, \’.’. ”,(li Iillll l
-
8/20/2019 SPE 13858 MS_Fracturing Without Proppant
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F@. 8-:711- d ImcturssilledwithO OXYin inBhchowrgrilstomunderMV stress-Wins 8fww
acwnmlsof0.1 and0.5 mmwereimpmd onlmcwo8- (a) 81 w dlsplvxmeti on I rwtura 0.? mm. CZ51W
f imng WE88WW 1JIM Pi axial pressufu l ,,WO WC (b) a imaf d@@acemem onImcluw 0.1 mm. Umf in ing
PfeCSUrn5,? Pd. a id Pmwm,:5,500 w (c)ahaaf t isc4awnwnt cmImclurw 0.5 mm. canning v-w
1,~ p i, amd PIWWrn 1,Wl P9Kand(d)sheafduF+Icament onf racture 0.5 mm, confiningpmswm 5,LW2
W, W pmwurw5 ,540ps i.
-
8/20/2019 SPE 13858 MS_Fracturing Without Proppant
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woo
*------4 .-
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----
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,
,
I , “= 0.25mm
,
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1000 2000
20
40
MPO
EFFECTIVE NORMAL STRESS ON FRACTURE
~.
B-VWIINIWI 01
fKIIXIM CC+NIIXHVW wnheffedva normalstressonfradu*Bim~ g~~.
5000
1000
*
--s..
-.
.
‘.
‘b.
i
\\
\8
“./”u=
25mm
‘a
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8,
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.,
.-.
-----
--------- --
)
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=
d
E
01
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t
I
1
moo 2000 &
4000
P r;
EFFECTIVE NORMAL ‘STRESS ON FRACTURE
* . g -va riauon d
fCSCIUreCOWJUCt”~ with efkotwa nonnaI stress on
lracIur6-HoPmm sandxw.
~. A1-ElllPtk hole
ln Sm63pz
al
infinity.