Note: Descriptions are shown in the official language in which they were submitted.
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1 3 3 0 2 5 6 005g50-lg7
STEAM ENHANCED OIL RECOVERY METHOD `:
USING 8RANCHED ALKYI, AROMATIC SULFONATES
Field of the Invention
The present invention relates to enhanced
oil recovery from a petroleum-bearing formation. More
particularly, it relates to ~n improved method of
steam or gas stimulation, or drive, of petroleum from
such a formation wherein a foam-forming surfactant is
injected into a well along with the steam or gas.
lo It has been postulated that steam or gas and
surfactant coact with formation fluids to form foam
~; which tends to block highly permeable gas, or steam,
channels that may cause "fingering" or "gravity
override", of the steam or gas through the formation. ~ -
lS ~ In a mature steam drive, residual oil saturations - .
(Sor) are frequently less than 15% in the highly
permeable steam override zones or isolated channels.
In these circumstances, it is desirable to divert the
steam from the high permeability channels at low oil
saturation into the less permeable zones at high oil ~ ;
saturation levels. The best foaming surfactant in -~
these cases foams to provide resistance to f}ow in
the oil depleted zones, but does not foam and block
~; access to the zones~at high oil saturation levels.
An example of a surfactant with these properties is
provided by U.S. Patent 4,556,I07. In other cases,
there are high permeability ~channels that become ~ -
resaturated by oil gravity drainage or there are
override zones with oil saturation leve}s which are
higher than those found in mature steam floods. For
improved steam mobility control and enhanced oil
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1 330256 ~ -
-2-
recovery in these circumstances, it is desirable to
use a foaming surfactant which foams both at low oil ~-
saturation levels and at relatively high oil
6aturation levels. Accordingly, this invention most -
particularly relates to improving blocking of gas or
6team permeability channel6 where the residual oil
content of the fluid passageway6 i~ relatively high
by use of 6urfactants which preferentially foam not
only in oil-depleted passageways, but also in
formations containing 15% or more residual sil. Such
foaming serves to provide steam mobility control and
improve oil recovery from the high pe~meability
streaks and to divert steam into the ~urrounding
areas to increase oil mobilization and oil recovery
from the oil-rich portions of the reservoir. ~ -
; In a preferred form, the foaming composition
is a surfactant ~olution containing an alkyl aromatic
urfactant (AAS) component with a branched alkyl
group having at least three secondary and/or tertiary ~
carbon atoms. In another preferred embodiment, the ~;
solution includes a branched alkyl aromatic sulfonate
component and (1) an alpha olefin sulfonate dimer
component, or (2) a 60dium metasilicate component, or
(3) a sodium chloride component, or mixtures of (1),
(2) and (3). Such compositions prepared in ;
;~ accordance with the present invention have been
demonstrated to have superior response time and ~-
provide effective foam blocking and movement of oil
through cores containing 6ignificant amounts of
residual oil.
It is a particular object of thi6 invention
to inject into a petroleum-bearing formation P
foam-formin~ 6urfactant composition in a water
colution which ~ubstantially more effectively blocks
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1 330256
-3- 61936-1799
'
highly permeable gas, or steam channels in the presence of sub~
stantial amounts o~ residual oil. Such oaming composition not
only mobilizes the residual oil as it blocks the gas permeable
portlon of the reservoir, but effectlvely enhances steam or gas ~ ;
contact of the oll-rich, less-permeable, petroleum-bearing
portions of the formation.
In qualitatlve terms, the new surfactant compositions
include a foam-forming surfactant component selected for its hlgh
effectiveness as a foamer in the presence of gas or steam contain-
ing at least some water and rasidual oil. In a preferred form,
the injected surfactant solutlon is a multiply-branched alkyl
aromatic sulfonate having a high molecuIar weight on the order of
at least 400, and speciflcally, an average molecular weight of
from 400 to 600 exhibits superior foaming and steam mobillty ~;
~ control in high permeability channels containing water and
;~ signlficant amounts of resldual oll. If deslred for foam per-
sistence under reservoir conditions, a non-condensable gas, such
as nitrogen, carbon monoxide, methane or the like may be added to
the steam before injection with the foam-forming components. -
BACKGROUND OF THE INVENTION
:.:
Steam stimulation of petroleum-bearing formations, or
re ervolrs, has become one of the preferred methods of enhanced
oil recovery. This`is because steam is cost-effective to supply
heat to low-gravlty, high viscosity oils. Heat reduces resistance
of oil flow from a reservoir to a produclng well over a wide range
of formation permeabilities. Further, such steam injection en-
hances the natural reservoir pres~ure, above that due to the ;~
hydrostatic head, or depth-pressure
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1 330256
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gradient, to increase the dif~erential pressure
between oil ln the reservoir and the producing well
bore.
The producing wel:L may be the 6ame well
through which 6team is periodically injected to
stimulate petroleum flow from the reservoir
(popularly called "huff and puff"). Alternatively,
one or more producing wells may be spaced from the
injection well so that the injected steam drives
petroleum through the reservoir to at least one such
producing well.
Almost all earth formations forming
petroleu~ reservoirs are created by sedimentary
deposition, with subseguent compaction or
crystallization of the rock matrix. Such deposition
of detrital materials, with varying composition and ~
over extensive geological times, occurs at varying
rates. The resulting compacted rocks in which
petroleum accumulates are permeable, but in general
the flow paths are quite heterogeneous. Accordingly,
a petroleum reservoir formed by such rock formations ` ;~
;; are inherently inhom~geneous as to both porosity andpermeability for fluid flow of either native
(connate) or injected fluids. Furthermore, flow ~`
permeability for connate gas, oil and water i~
substantially different for each liquid or mixture.
Because of these differences in permeability, it is
now common practice to inject foam forming
surfactants with the injected 6team to block the more
permeable gas passages that may develop in the
formation. The desired result i6 to divert 6team
~rom the more permeable gas passageway to less
permeable oil-rich zones of the reservoir.
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1 330256
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~he foaming component ls usually an organic
surfactant material.
Another particular feature of 6uch
inhomogeneity of sedimentary rock formations appears
to be their ~hale or clay content. It is known that
such clay material is 6usceptible to alteration when
contacted by water and particularly when the injected
water i6 in the form of 6team having little salt
content. In general, clays have large surface area
to volume ratios and when altered by water or steam
tend to affect adversely contact between connate oil
and reservoir rock. Most specifically, reservoirs
containing viscous oils having organo-metallic and
; acidic components are particularly susceptible to
both steam and 6urfactant materials used in enhanced
oil recovery. Further, the solubility of surfactant
in the connate water of the formation and the
reservoir oil may have a deleterious effect on the ~m
foaming ability or 6tability of the foam where gas
permeability and steam loss has increased by
fingering or gas override. Thus, the foam may not be
active where residual oil in the highly permeable
`~ channels exceeds more than a few percentage of the
pore volume. Hence, there is a need for foam forming
surfactant compositions which preferentially form ;~
foam in contact with residual oil within or around
the 6team- or water-permeable passageways of the
~; formation, but without significant foam formation
where they contact oil in oil-rich flow channels
through the reservoir. `
This invention i6 an improvement over prior
methods of using foam-forming compositions to
enhance petroleum production from oil-~earing
formations. Many o~ these are mentioned and
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~ 330~56
discussed in U.S. Patent No. 4,086,964. Others
include l~.S. Patents Nos. 4,393,937, 4,532,993 and
4,161,217. It is also an improvement over previously
known methods of foam forma1:ion to control
"fingering" or "over-ride" by injecting a ~oam-
forming surfactant w1th gas or steam which primarily
foams upon contact with residual oil port~ons of the
reservoir created by gas or steam flow paths ~
therethrough. ~:
The need for 6urfactants which foam in the
presence of both oil and water has been known for
some time. Bernard ("Effect of Foam on Recovery of
Oil by Gas Drive" Prod. Monthly 27, No. 1, 18-21,
1963) noted that the best foaming surfactants for ~ -
iml;iscible di6placements such as steam floods are
those which foam when both oil and water are present.
Dilgren et al. (U.S. Patent 4,086,964) recognized the
importance of non-condensable gas and added
electrolyte ~uch as sodium chloride for steam foams
and discloses the use of an alkyl aromatic sulfonate,
dodecylbenzene sulfonate, for this use. Other
patents teach the use of alkyl aromatic sulfonates
for this use without recognizing a difference in -~
performance for the branched and linear structures
(U.S. patents 4,532,993; 4,161,217 and 3,348,611).
;~ U.S. patent 4,161,217 teaches that mixtures of low
molecular weight (300-400) and high molecular weight
(400-600) alkyl aromatic sulfonates are useful
foaming agents for hot water non-condensable gas foam
drives. A still more recent patent (U.S. 4,562,727)
teaches that olefin sulfonates such as alpha olefin ;;
sulfonates are substantial improve~ents over alkyl
aromatic sulfonates. The present invention
~dentifies a class of branched alkyl aromatic ;~
` 1 330256
-7- 61936-1799
sulfonates which offer substantlal advantages over the surfactants
of the prior art to produce better foaming behavior in the
presence of varying amounts of residual oil. They are especially
useful ~or improving oil recovery fxom reservoirs with high
permeability zones containlng varying amounts of residual oil
having pore volume saturatlons of fxom a few percent to 30% or
higher.
SUMMARY OF THE INVENTION
The present invention is directed to a composition for,
and an improved process of enhancing petroleum recovery from a `~
petroleum reservoir using steam and involves injecting lnto the
reservoir, along with such steam, a surfactant composition which
upon injection is capable of co~actiny with such steam in the ;~
presence of residual or relatively depleted oil portions of the
reservoir, to form a foam. Preferably the steam is at least
partially wet to assist the formation of such foam in contact with
residual oil and includes in its gaseous phase from about 1% to
50% of a non-condensable gas. The steam may also additionally
contain 0.01~ to 5% of an electrolyte and the water phase of the
:, :,
steam may contain 0.1 to 5% of an added anionic surfactant of
different struc~ure.
In a preferred form, the foaming composition is a `
~ , ~. ,. :
surfactant solution containing (1) a branched alkyl aromatlc -~ -~
surfactant component with the alkyl group containing at least
three tertiary and/or secondary carbon atoms and with a molecular
welght on the order of at least 400, and speclflcally, an average ~; ~
molecular welght of from 400 to 600 and with the aromatic ~`f~i'
~omponent containing 0-2 normal alkyl substltuents wlth 0-3 carbon
~ ~n
1 330256
-7a- 61936-1799
atoms in addition to ~he alkyl group. In a further preferred
form, the compositlon may be a mixture of (1) in combination with
(2) a second anionic sur~actant component such as an alpha olefln
sulfonate or alpha olefin sulfonate dimer component, or (3) an
electrolyte such as sodium chlorlde or sodium metasllicate
component, or mixtures of (1), with ~2) and (3). More preferably, ~ :
components (1) and (2) or components (1) and (3), are present ln a
ratio of 12 10 to 10,1 and their concentration ls from 0.1% to 10%
by welght. Such compositions prepared in accordance with the
present invention have been demonstrated to have a superior
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1 330256
-8- 61936-1799
combination o beneficlal propertles including a rapid response
and a strong foa~ ln the presence of variable amounts of resldual
oil.
In a most preferred ~orm, the foam-forming component is
an alkyl aroma~ic sulfonate which is preferably a multiply-branch- ;
ed alkyl aromatic sulfonate having a molecular weight of at least
400, and speclfically, an average molecular weight of from 400 to
600, as described earlier, which can be injected lnto a producing
formation, either intermittently or continuously, and either in a
; 10 water solution, or as an additive to wet steam. Preferably, the ;~
alkyl aromatic sulfonate in from about 0.01% to 5% of the water
phase of the steam. Desirably, such branched alkyl aromatic -~
sulfonates are capable of interacting with the injected steam to
form foam primarily in the residual oil portions of the reservoir
formation and either block or mobilize residual oil in such
permeability channels.
; : .
In preferred forms of such multiply-branched alkyl
aromatic sulfonates, the branched alkyls, having from 15 to 30 ;~
carbon atoms are each attached to the aromatic component, ~ ~ ~
~; 20 desirably benzene, toluene, or xylene and the sulfonate component ; ~-;
is attached to the aromatic ring. The alkyl aromatic sulfonates
~ ~ :
may be prepared from the branched alkyl aromatic component by
conventional laboratory or commercial sulfonation processes. The
branched alkyl aromatics can be prepared by alkylating the -
aromatic component with a branched olefin. The branched olefins
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1 330256
~8a- 61936-1799
of appropriate molecular weight may be prepared by olefin
oligomerization processes such as the action of an appropriate
aatalyst on propylene. Examples of aatalytia propylene ~:
oligomerization proaesses suitable for the present invention are
the well known phosphoric acid or boron trifluoride catalyzed
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1 330256 -~
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oligomerizations. U.S.patent 3,932,553 provides
examples of suitable oligomerization processes.
The sulfonates are 6uitably in salt form,
particularly ~alts of 60dium, potassium, ammonium or
other water-soluble cations. The preferred ~alt is
sodium. However, acid form~ of the sulfonates may
also be used in the present invention.
Desirably, but not necessarily, the steam
may include an injectable, non-condensable gas along
with the surfactant composition. The non-conden6able
gas component may be injected continuously or at
least periodically with the steam. Further, the gas
may be misci~Ie in the oil phase of the reservoir
fluids. Such gas may be nitrogen, methane, flue gas,
carbon dioxide, carbon monoxide or air. Further, the
team and the 6urfactant composition may be injected
continuously into one well for producing oil from an
adjacent well penetrating the same reservoir.
Alternatively, the steam including the foam-forming
composition may be injected cyclically into one well
and petroleum periodically produced from the same
well.
Further objects and advantages of the
present invention will become apparent from the
following detailed description taken with the ~-
drawings which form;an integral part of the present
pecification.
, .
Descri~tion of the Drawinqs
; ~Fig. 1 is a schematic elevational
representation of an injection well penetrating a
petroleum reservoir formed by a sedimentary earth
formation wherein 6team i~ injected to reduce
vi6cosity of the oil and a 6urfactant composition
including the foam-forming component.
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~ 330~56
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Fig. 2 is a 6chematic flow diagram of
test arrangement for generating foam in the presence
of ~il and water representative of connate fluid6 in
a reservoir in which foam i6 formed for flow through
S a permeable core so that a ~urfactant formin~ 6uch
foam may be evaluated as to its usefulness to block
~team permeable paths through oil-depleted or
residual oil in a flooded-out core and to measure its
: resistance to foaming under varying liquid conditions
: 10 in the core.
: Fig. 3 is a graph of test results obtained
with the test arrangement of Figure 2 and illustrates
a portion of a method of evaluating surfactant
,
:~ compositions as to their foam-forming capability and :~
lS stability in the presence of residual oil and brine
~: in the core.
DESCRIPTION OF THE INVENTION
The present invention is, at least in part,
based on the discovery that non-obvious and
beneficial advantages are obtained by using a
composition of matter which includes using particular
. branched alkyl aromatic sulfonate surfactant ,~
;:~ components for foam-:injection into a petroleum `:
reservoir which are more effective in the presence of ~ :
~:~ 25 steam to foam and mobilize residual oil in gas
permeable:passageways than previously known
urfactant compositions. The essential feature of
such a composition of matter is its superior ability -~.:
' to foam where a ~ubstantial fraction of the flow ~:
paths contain residual oil, but substantially higher `~
~: percentages of gas or 6team, than other portions of a : -
reservoir. The result of usinq such a composition in
~team-as6isted oil recovery is that the high
permeability 6treak6 in the reservoir channels which
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1 330256
contain substantial volumes of residual oil are
effectively plugged preferentially by the foam.
T~us, residual oil i6 effectively mobilized and moved
through the channels. Such preferential foam
plugging divert~ steam or gas flow through the
formation to less permeable zones containing
substantially higher oil concentrations.
Accordingly, it will be noted that the present
process has the beneficial effects of enhancing
recovery of petroleum from petroleum reservoirs, by
rore rapidly forming foam in the presence of
~ubstantial amounts of residual oil to divert steam
or gas from the more gas permeable, relatively oil~
depleted zones, ~o that lesser volumes of gas
increase oil flow from petroleum-rich, but less
permeable, zones of the reservoir.
~; Fig. 1 iIlustrates 6chematically an
arrangement for injecting the foam-forming surfactant
composition of the present invention into an at least
partially depleted oil reservoir where it is
desirable to reduce the ~team or gas permeability.
As indicated, the invention is particularly directed
to the problem of controlling ~team injection into a
producing formation to heat the petroleum and thereby
~ 25 reduce its vi~cosity. The ~team may also increase
- pressure in the formation to enhance the natural gas
or tratigraphic pressureis to increase petroleum flow
into the same well, or ~n adjacent well, penetrating
the formation. For this purpose a steam generator 10
typically generates 6team from water in a single-pass
through a continuous boiler tube 12 heated by a gas
or oil-fired burner 13. Water for steam generation
i6 6upplied by pump 34 and typically it will include
minerals and 6alts which replicate or, are compatible
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1 330256
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with, connate water in the formation. Desirably,
water may pass through a "water-softener", or ion
exchange medium 14, and i6 heated in boiler tubes 12
sufficiently to form a low quality or "wet" 6team,
preferably having a quality of less than 80%. Such
steam is injected into well 16 through well head 38 -~ ~
by ~team pipe 36 out of heat exchanger 15. Steam iB ~ ~ .
then injected into a pipe 6tring 18 running down well
casing 17. Pipe string 18 may be spaced as by
centralizers 2~ from ca6ing 17 to prevent loss of
heat from the steam to earth formations along the
length of casing 17 to the desired injection depth,
~uch as earth formation 24 forming reservoir 22.
The permeability of nearly all sedimentary
earth formations which form petroleum reservoirs,
such as 22, are inherently inhomogeneous to flow of ~.
connate fluids, water, oil and gas. Each of these
fluids tends to flow selectively in permeability
channels that have the least resistance to such flow.
The resistance to flow of each fluid primarily
depends upon its viscosity either alone or in mixed
phase with the other fluids. Typically, the
resultin~ or relative permeability of the flow paths
for each fluid is different within each formation.
Since gases are more mobile than ei~her oil or water,
; or their mixtures, injected 6team in general tends to
flow through more permeable gas channel~ and may form
"fingers" 26 in formation 22 as indicated by dotted
lines. Thi6 gas flow by-passes; "tighter" or less
permeably zones wherein the oil-permeable passages
are ~maller or the oil is more tightly ~ound to the
~urface of the rock. In particular, the oil may al60 ~ `
be in contact with clay or ~hale material with 6and
or carbonate components that ~orm the permeable
~__~ f
1 330256
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channel6. Thus, "fingering" develops as indicated by -
channels 26, or "gas override" occurs as indicated by
area 25 at the top of forwation 22. Where these -
develop, energy is lost and large portions of the
liquid oil are not heated by the injected steam.
With f~team flow predominantly through lower
permeability gas channels 25 and 26, the injection
profile is distorted, as indicated generally by I. ;~
dotted line 28.
As discussed above, distortion of the
injection profile may be corrected by addition of a
foam-forming component to steam injection line 36.
For this purpose, fsurfactant solution is supplied by
tanks 30 and 31 through metering pump 35 and
injection line 37. Foam may be created within the ~
formation either by forming it with gas or fsteam ~ .
within the steam supply line or upon contact with
formation fluids. The foam 60 injected
I f preferentially flows with the steam to gas-permeable
~ ~ 20 channels 25, 26. It effectively plugs them
-~ ~ temporarily so that steam in the formation is then
diverted to heat the oil-rich portions of the , -
formation. The desired result is indicated by the
relatively piston-like movement of the steam front
indicated by dotted lines 24.
- However, a particular difficulty i6 forming
and maintaining foam~as a blocking agent in those
team or gas permeable channels arises where they
contain 6ubstantial or significant amounts of `
residual oil, that is, in excess of a few percent.
In particu}ar, it has been found that previously
known surfactants are not effective in reservoirs
having a residual oil content of more than a few l ~
percent. In accordance w~th the present invention, f -'' '
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1 330256
-14~
I have found that the branched alkyl aromatic
~ulfonates are remarkably effective $n forming foam
in the presence of 6ignificantly higher percentages
of ~uch residual oil, 6ay up to 30% or higher of the
available pore volume.
In the present il:Lustration, oil is
produced from an adjacent producing well, such as 50,
by a pump 52. It will also be understood that
formation 22 may be cyclically heated by 6team, and
then periodically oil produced from injection well 16
through pipe 18 by rearranging well head 38 ~o that
it 6upports a pumping unit similar to pump 52 on well
string 53 in well 50.
The surfactant composition prepared in
accordance with the present invention, is preferably
supplied as a liquid solution and pumped as a foam
forming concentrate from tank 30 for mixing with
reservoir compatible water from tank 31. The
solution is metered by pump 35 through line 37 at a
desired rate to contact steam flowing in line 36 or
pipe 18. Alternatively, the foam may be formed with
gas from a gas source (not shown). Suitable gases
may include nitrogen, flue gas, methane, carbon
dioxide, carbon monoxide or air. Such gas would be
added through well head 38 as by line 36.
Figure 2 schematically illustrates test
apparatus suitable for evaluating steam foam
surfactant compositions and t~e compatibility of
their foaming components in cores containing varying
amounts of residual oil, to evaluate their
effectiveness to form and maintain foams to block
steam or gas flow. In this embodiment, the permeable -
oil-bearing reservoir rock 6ample or core is
~imulatecl by a 6teel wool pack 60. Such a core i6
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1 33û~56
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disposed in an autoclave or visual pressure contalner i~
57 suitable for holding the core at reservoir
temperatures, as by heater coil 61, and pressures.
Heat may be added to the incoming ~luids by preheater
55. Pressure may be applied by ga~ source 63, 6uch
as nitrogen. Temperatures ~n the order o~ 300-F to
500'F and pressures up to 1000 psi are provided.
Fluids are then ~electively 6upplied to the core
under suitable flow conditions. The apparatus
provides a source of steam generator feed water
(SGFW) from ~rine tank 66 under control of valve 79.
Crude Oil from tank 6S is supplied through valve 75
and line 68 to pump 67. Inert Gas such as nitrogen
from tank 63, creates flow through test core 60 under
lS control of valve 82, as measured by flow meter 83.
As indicated, these sources simulate reservoir brine
and crude oil of a subject reservoir. The oil and
brine act as displacing fluids. Selected surfactant ~-~
601utions from tank 64 are added to brine from tank
66 and the mixture is supplied to the core through
preheater 55 under pressure by pump 80. The
;~ surfactant materials from 64 may be introduced into
`~ the test system in selected quantities by valve 78.
Differential pressure across core 60 is measured by -~
DP cell S9 connected across inlet line 62 and outlet -~
~ ~ line 76. The detected pressure difference i6 ...:
`~ desirably recorded as a time-pressure graph, as shown
in Fig. 3, by recorder 72. Inert gas volumes are
measured~by wet test meter 73 connected to ~eparator
tank 74.
Steam-FDam Test
The ~team-foam test consist6 of recording
the pressure drop vs time, as detected by
differential pressure cell 59. A selected ~oaming !~
~. ,.
1 330256
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surfactant flows through eteel wool plug 60 in cell
57 and ~uitably run at 400'F and 500 psig in the
presence of flowing nitrogen.
A typical test sequence is illustrated in
Fig. 3. The first step is to pass Steam Generator
Feed Water ~SGFW~ from brine source 66 and oil, such
as a representative crude irom tank 65, together
through core 69 until a substantially constant
pressure drop v~ time i5 recorded. As shown in Fig.
3, this is followed by flowing SGFW alone until
steady state is again established. This puts the
foam generator in a "Residual Oil" state. Pressure
drop under these conditions i6 typically 0-2 psi.
~ext, a surfactant composition from tank 64
which is to be tested is pumped through the system as
a dilute eolution in SGFW. With a good foaming
` :
composition, the pressure across the steel
wool pack 60 increases over 15-100 min and level6 off
at a new steady state value (typically 20-100 psi);
this condition i6 indicated in the 6ection ~f the
graph of Fig. 3 identified as foam pressure drop
(Pf). The test then continues with introduction of
~; oil alon~ with surfactant composition. The measured
pressure drop under these conditions is typically -~
2-20 psi (Pf+o~.~ Finally, the surfactant solution is --
replaced with brine ~SGFW) alone and the pressure -~ -
drop with brine and residual oil is measured ~Pb+o).
Four performance parameters are measured~ he
; time required to reach a steady state pressure drop
with foam (Response Time), (2) the steady-state
pressure drop with the foam (Pf), (3) the steady~
tate pressure drop with foam + oil ~Pf+o), and (4)
the 6teady-state pressure drop with brine (SGFW) +
oil (Pb+~). These performance parameter6 are labeled
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1 330256
-17-
in FIG. 3. Large values for Pf ~Fig. 3) and low
values for Pf~ (Fig. 3) are desired where res~dual
oil saturation i6 low. Surfactant compositions with
these properties are able to increase the resistance
to steam flow in high permeability zones o~ the
reservoir where residual oil 6aturation i6 low; thus
steam is redirected to portions of the reservoir
where oil content is stil} high. This i6 typical of
gravity override or steam channeling 6ituations as
shown in Fig. 1.
~; The Response Time and foam pressure (Pf) in
Fig. 3 depend upon the surfactant and the residual ~ ;
oil in the foam (core) generator. In the absence of ;~
residual oil, the response time is very 6hort with a
pressure increase occurring as soon as the foaming -
~urfactant contacts the foam generator. When
residual oil is present, Response Time and Pf depend ~ `
upon how effectively the surfactant mobilizes and ,-
removes oil and how well the 6urfactant foams in the
presence of oil. Foaming surfactants of the prior ! ,~
art which have been used in steam flooding to - ``
counteract override conditions with low residual oil
behave as shown in Fig. 3; the pressure drop with i~
foam + oil (Pf+o) is much lower than the pressure
drop with foam alone (Pf) and either lower or about `~
the 6ame as the pressure drop with brine + oil
(Pb~o), indicating the absence of foaming in the ,~
presence of oil. For circumstances where there are
high permeability channels which contain oil from
qravity drainage or there are override zones with oil
atura~$on level6 which are higher than those found !
$n mature 6team floods, the preferred performance i6 j::
a rapid response with residual oil ~Short Response `~
Time in Fig. 3), a h$gh pressure drop with foam ~f), ~;
~ .
`',
~ 330~56 ~
--18-- ! ~
and ~ ~ubstantial pressure drop with foam plu5 low
level6 of flowing oil (high Pf+o).
Surprisingly, we have found a class of
surfactant~ which have the favorable combination of
properties including a rapiid response rate with
residual oil, a high pressure drop with foam (Pf),
and a pressure drop with foam + oil (Pf+o) which i6
higher than the pressure drop with brine + oil
~Pb+o). These surfactants o~fer the advantages of
providing steam diversion and steam mobility control
in override conditions and low residual oil -
saturation zones as well as in high permeability
channels containing high residual oil levels. The
following examples demonstrate these properties.
The characteristics of the foam generator
used in the above-described Steam-Foam test may
change with time as the ~teel wool pack ages, or `~
it is replaced. This may result in constantly
changing values for the parameters measured in this
test and make it difficult to compare a~solute values
of one surfactant to another. For this reason, a
standard composition known to perform well is run in
the test unit on a given day and results for all
other surfactants tested on the same day and the 6ame
pack are recorded relative to thi6 reference
material. Reproducibility of relative Foam Blocking
and Response Time measurements are generally within
10%.
.~ :
,: ~
; .
s ~
1 330256
--19--
Examples
The surfactan~ were compared in the ~oam
test unit described above and depicted in Fig~ 3.
The foam flow tests were run in a 1/4 inch diameter
by 2-1/2 inch long steel wool foam generator at 400-F
and about 500 psi. ~he surfactants were tested at a
liquid phase flow rate of 2 ml/min. with an active
component concentration of about 0.5% by weight. ~he
gas phase consisted of approximately equal volumes of
steam and nitrogen at a combined approximate flow
rate of 40 ml/min. at test conditions. The tests
with flowing oil were run with 2 ml/min. surfactant ~
solution or SGFW and 0.2 ml/min. of Kern River crude -
oil. The brine, or synthetic S~FW, was prepared by
dissolving NaCl (295 mg/l), KCl (11 mg/l), NaHC03 ~ `;- `
(334 mg/l), and Na2S04 (61 mg/l) in distilled water. ~.~
The following abbreviations are used in the examples: ;
- ~, -
. ' ''
~-
~ ' ~; ''
.: ....
i ~ , . : ; ~' ~ :,
:,
:
'.
.
~ 330256
-20-
LABS ~inear Alkyl Benzene Sulf~nate
LATS Linear Alkyl Toluene Sulfonate
: LAXS Linear Alkyl Xylene Sulfsnate
~ BABS Branched Alkyl Benzene Sulfonate
: 5 BATS Branched Alkyl Toluene Sulfonat~
BAXS Branchedl AlXyl Xylene Sulfonate
BACS Branched Alkyl Cumene Sulfonate
: Example 1
This example compares the performance of
~ .
representative surfactants of the present invention
with 6urfactants w~ich have been used or considered
for use in the field for steam-foam floods. In the
Table I,~relative values are given for the response
rate and foam pressure (Pf) whereas the absolute
value for the Pf+o/Pb+o ratio is given. The
recipro~al of the response times of Fig. 3 were used
to obtain the relative response rates.
~. . .. ..
` 1: :
' `: ~ ` ; . ~ ' :
~ "~
, : ' ~'::
~ 330256
-21- -
Table I
~elative Values `~:~
Rer,ponse ~'"i.'
: Surfactant Rat.e Pf Pf+o~Pb+o :
SuntechTM IV 1015 1 1 o.l -
ChaserTM SD1000 2 1 0.1
EnordetTM 1618AOS 0.7 0.5 0.4
: EnordetTM LXS 1314 1 0.1 0.2
~:~ : EnordetTM LTS 18 6 1 0.2 .;~
CORTM 180 0.3 0.6 0.7 ;
~: DowfaxTM 2A1 0.5 0.5 1 .
DowfaxT~ 3~2 1.8 0.5 0.6
BATS (457)1 ~ 6 0.9 8.5
BAXS (470)1 8 1 4.3 . ~ `
. .
;~ 15 BABS (504)1 4 1.3 3.1
` ~ (1) Average Values for the Equivalent Weights
; ~ ~ These results 6how that the branched alkyl -~
`::
aromatic sulfonates of the present invention have the
best combination: of~the desi~red properties in each of ~
~: 20 the three values: fast response t6ubstantially higher ::
than l), high foam pressure (Pf)~(about 1), and a -~
high value for the ratio of the pressure of foam +
j ` oil (Pf+O) to the~pressure of brine + oil (Pb+o)
(substantially greater than 1).
, ~ . .
..: . .
1 330256
-22-
Example 2
Tests were run as in Example 1~ These ~:
results show that the branched alkyl aromatic
sulfonates of the present invention have better : ;:
co~binations of the desired properties than the
linear alkyl aromatic 6ulfonates or lower e~uivalent :~
weight branched alkyl aromatic su}fonates.
; ~,.~:
.: ~
':
` :
- ~
,. -: -
1 3 3 0 2 5 h ~ ~
-2 3-
,j~_, "
O ,~
kf ~ ~:
',;: .
~J Ir'f ff~ fN Irtf 'tf 'f~f
$ o o O ~f ~
, ,'
H ~ O O O
R¦ ' ~ D~ ;
U~ : S,, ,':
R : ~ o ~ ~ :
"", ~ , ff~, ~Cf o~ o
U ,1 ~ ,~ L C ~ `
:~ ~ ~ r o .~
~, ff~ , ff~f ~ 0 ,,, , ~ ,
U V~ f U'f V~f ~ S R
m~ a ~m m
r.~, 3,
:``: '~
'~
::
^
~ 3 3 0 2 5 6
-24-
ExamPle 3
Test6 were run as in Example 1. In these i~
cases an additive, either an electrolyte ~r an
ani~nic ~urfactant, was included with the primary
surfactant.
'
,
: - ~
1 330256
-25~
~ o 0
:,
o ~ ~
N ~ ~ S e
-,.'
~ D V V
U to ~
: ~ `' CD OD OD 0
~ u~ O ~ 3 ~ 1
t~t ~ :tt' o
~ 8 ~ o ~ ~ ~
t~ vl ~ Z o z z ~ L
~n
;: ,~ o o :o: o ~ ~
U ~ ~ 0 , , ~,
, ~ ~o ~- :
LI ~r 'r ~ ~ u~ .r u~ u~ ~ L ~ c ~
_ _ _ o ~ ~0:
C. N ~ ~ ~ N; 1
: ~~ ~ 0 0 0 0 ~ o
:H ~ C
: ~ ~:
:~
1 33~256
-26-
The results of Example 3 demonstrate that the
branched alkyl aromatic sulfon~tes of the present
invention respond rapidly, give high foam pressures
~Pf), and give high Pf~o/Pb+o ratios in the presence
of electrolytes or other anionic 6urfactants. Note
that the L~TS/~OSD mixture (last entry above) which
lies outside of the present invention, did not give
high values for all three of the desired properties.
Preferably the sulfonate component is in the
form of a sodium salt. Other salts such as ~
potassium, ammonium ~r other water-s~luble cations ~ -
and mix~ures thereof may be used. Additionally, the
sulfonates may be in acid form in the branched alkyl
aromatic sulf~nates useful in the practice of our
invention.
Various modifications and changes in the
surfactant compositions and their method of use to
enhance recovery of oil from reservoirs undergoing
steam stimulation will become apparent to those
~ 20 skilled in the art from the forgoing description of
; examples and their use. All such modifications or
changes coming within the ~pirit and scope of the
present invention are intended to be included within
; the scope of the claims defining the invention.
We claim:
:
: ~ .':-',
-: ~....
.
. ~< r
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