Note: Descriptions are shown in the official language in which they were submitted.
PF 71557 CA 02825360 2013-07-22
Process for mineral oil production from mineral oil deposits with high deposit
temperature
The present invention relates to a two-stage process for mineral oil
production from mineral oil
deposits with a deposit temperature of more than 70 C and a salinity of 20 000
ppm to
350 000 ppm, in which an aqueous formulation comprising at least one glucan
with a p-1,3-
glycosidically bonded main chain, and side groups 3-1,6-glycosidically bonded
thereto and
having a weight-average molecular weight M of 1.5*106 to 25*106g/mol, are
injected into a
mineral oil deposit through at least one injection borehole and crude oil is
withdrawn from the
deposit through at least one production borehole. The aqueous formulation is
prepared in two
stages, by first preparing an aqueous concentrate of the glucan, and diluting
the concentrate on
site with water to the use concentration.
In natural mineral oil deposits, mineral oil is present in the cavities of
porous reservoir rocks
which are sealed toward the surface of the earth by impermeable top layers.
The cavities may
be very fine cavities, capillaries, pores or the like. Fine pore necks may,
for example, have a
diameter of only approx. 1 m. As well as mineral oil, including fractions of
natural gas, a
deposit comprises water with a greater or lesser salt content.
In mineral oil production, a distinction is drawn between primary, secondary
and tertiary
production.
In primary production, after commencement of drilling of the deposit, the
mineral oil flows of its
own accord through the borehole to the surface owing to the autogenous
pressure of the
deposit. According to the deposit type, however, usually only approx. 5 to 10%
of the amount of
mineral oil present in the deposit can be produced by means of primary
production; thereafter,
the autogenous pressure is no longer sufficient for production.
After primary production, secondary production is therefore used. In secondary
production, in
addition to the boreholes which serve for the production of the mineral oil,
known as the
production boreholes, further boreholes are drilled into the mineral oil-
bearing formation. These
are known as injection boreholes, through which water and/or steam is injected
into the deposit,
in order to maintain the pressure or to increase it again. As a result of the
injection of the water,
the mineral oil is gradually forced through the cavities in the formation,
proceeding from the
injection borehole, in the direction of the production borehole. However, this
works only for as
long as the cavities are completely filled with oil and the more viscous oil
is pushed onward by
the water. As soon as the mobile water breaks through cavities, it flows on
the path of least
resistance from this time onward, i.e. through the channel formed between the
injection
boreholes and the production boreholes, and no longer pushes the oil onward.
By means of
primary and secondary production, generally only approx. 30 to 35% of the
amount of mineral
oil present in the deposit can be produced.
It is known that the mineral oil yield can be enhanced further by measures of
tertiary oil
production. Tertiary oil production includes processes in which suitable
chemicals are used as
PF 71557 CA 02825360 2013-07-22
2
assistants for oil production. This includes what is called "polymer
flooding". Polymer flooding
involves injecting an aqueous solution of a thickening polymer into the
mineral oil deposit
through the injection boreholes instead of water. As a result of the injection
of the polymer
solution, the mineral oil is forced through said cavities in the formation
from the injection
borehole proceeding in the direction of the production borehole, and the
mineral oil is finally
produced through the production borehole. Due to the elevated viscosity of the
polymer
solution, which is matched to the viscosity of the mineral oil, the polymer
solution is thus able to
break through cavities at least not as easily as is the case for pure water,
if at all. Parts of the
deposit not accessible to the water are reached by the polymer solution.
For polymer flooding, a multitude of different thickening water-soluble
polymers have been
proposed, both synthetic polymers, for example polyacrylamide or copolymers of
acrylamide
and other monomers, especially monomers having sulfo groups, and polymers of
natural origin,
for example glucosylglucans, xanthans or diutans.
Glucosylglucans are branched homopolysaccharides formed from glucose units.
Homopolysaccharides formed from glucose units are called glucans. The branched
homopolysaccharides mentioned have a main chain formed from 3-1,3-bonded
glucose units, of
which ¨ viewed statistically ¨ about every third unit is P-1,6-glycosidically
bonded to a further
glucose unit. Glucosylglucans are secreted by various fungal strains, for
example by the
filamentous basidiomycete Schizophyllum commune, which, during growth,
secretes a
homopolysaccharide of the structure mentioned with a typical molecular weight
M of
approx. 5 to approx. 25*106g/mol (trivial name: schizophyllan). Mention should
also be made
of homopolysaccharides of the structure mentioned secreted by Sclerotium
roffsii(trivial name:
scleroglucans).
The production of such glucosylglucans is disclosed, for example, in EP 271
907 A2,
EP 504 673 Al, DE 40 12 238 Al and WO 03/016545, and they are produced
specifically by
fermenting suitable fungal strains while stirring and venting, and removing
the polysaccharide
formed.
Our prior application EP 09179716.7 discloses a process for producing
concentrated
glucosylglucan solutions with concentrations of more than 3 g/I.
CA 832 277 A discloses the use of aqueous solutions of glucosylglucans for
polymer flooding.
The aqueous solutions used have, at a concentration of 1% by weight, a
viscosity at 24 C of at
least 500 mPa*s, and the concentration of the glucosylglucans is 0.005 to 1%
by weight,
preferably 0.01 to 0.3% by weight. The solutions used may additionally
comprise further
components, for example surfactants, biocides or bases, for example alkali
metal hydroxides.
EP 271 907 Al discloses a process for producing glucosylglucans, fungal
strains particularly
suitable for this purpose, and the use of such glucosylglucans for tertiary
mineral oil production.
3
The document further discloses measurements of the viscosity of aqueous
solutions in saline water
at temperatures of 25 C to 60 C.
lido Rau, Andreas Haarstrick and Fritz Wagner, Chem. lag. Tech. 64(6) (1992),
pages 576/577
propose the use of schizophyllan solutions for polymer flooding of mineral oil
deposits with high
temperature and salinity, without describing details of a process.
Uo'o Rau, "Biosynthese, Produktion und Eigenschaften von extrazellularen Pilz-
Glucanen"
[Biosynthesis, production and properties of extracellular fungal glucans] in
Berichte aus der
Biotechnologie, Shaker Verlag, Aachen, 1997, pages 106 ff. mentions that
schizophyllan solutions
have thermal stability up to 135 C and should therefore be suitable for
tertiary mineral oil
production in deep deposits, for example in the North Sea. It is also
mentioned that schizophyllan
has a reversible decrease in viscosity up to shear rate of 40 000 s-1. It is
additionally pointed out
that the viscosity of schizophyllan solutions is barely influenced by the
presence of alkali metal and
alkaline earth metal ions.
It was an object of the invention to provide an improved process for polymer
flooding for deposits
with deposit temperatures of at least 70 C using glucosylglucans.
Accordingly, the invention provides a process for mineral oil production from
a deposit with a
deposit temperature TL of at least 70 C, wherein the process comprises at
least the following
process steps:
(1) providing a concentrate (K) of at least one glucan with a 3-1,3-
glycosidically bonded
main chain, and side groups 3-1,6-glycosidically bonded thereto and having a
weight-
average molecular weight M of 1.5*106 to 25*106 g/mol, in water with a
concentration
of more than 3g/I to 30 g/I,
(2) preparing an aqueous formulation (F) the at least one glucan by
diluting the concentrate
(K) provided in step (1) on site with water to a glucan concentration of 0.05
g/I to 3 WI,
with the proviso that the concentration is selected such that the viscosity
TiF, measured
at 7 s-1 and TL, of the aqueous formulation (F) is at least 3 mPa*s, the
viscosity riF being
selected in comparison to the viscosity flail measured at TL such that fir <
iii. and
(3) injecting the aqueous formulation (F) into a mineral oil deposit through
at least one
injection borehole, and withdrawing crude oil from the deposit through at
least one
production borehole,
wherein said deposit comprises oil and deposit water with a salinity of 20 000
ppm to
350 000 ppm, and wherein said oil has a viscosity rioii measured at Ti. of at
least 3 mPa*s.
CA 2825360 2018-08-03
PF 71557 CA 02825360 2013-07-22
4
With regard to the invention, the following should be stated specifically:
To execute the process according to the invention, at least one production
borehole and at least
one injection borehole are sunk into the mineral oil deposit. In general, a
deposit is provided
with a plurality of injection boreholes and with a plurality of production
boreholes.
To execute the process according to the invention for mineral oil production,
an aqueous
formulation (F) at least comprising a glucan with a 8-1,3-glycosidically
bonded main chain and
side groups 8-1,6-glycosidically bonded thereto is used, and injected into a
mineral oil deposit
through at least one injection borehole.
In this context, the term "mineral oil" of course does not mean single-phase
oil, but rather the
term also comprises the customary crude oil-deposit water emulsions. As a
result of the
pressure generated by the formulation injected, called the "polymer flood",
the mineral oil flows
in the direction of the production borehole and is produced through the
production borehole.
The deposit temperature of the mineral oil deposit to which the process
according to the
invention is applied is, in accordance with the invention, at least 70 C,
especially 70 C to 150 C,
preferably 80 C to 145 C, more preferably 90 C to 140 C, even more preferably
100 to 135 C
and, for example 105 C to 130 C.
Such comparatively high deposit temperatures are encountered in particular in
the case of
comparatively deep mineral oil deposits.
It is clear to the person skilled in the art that a mineral oil deposit can
also have a certain
temperature distribution. The deposit temperature mentioned relates to the
region of the deposit
between the injection and production boreholes, which is covered by the
polymer flooding.
Methods for determining the temperature distribution of a mineral oil deposit
are known in
principle to those skilled in the art. The temperature distribution is
generally undertaken from
temperature measurements at particular sites in the formation in combination
with simulation
calculations, and the simulation calculations take into account factors
including amounts of heat
introduced into the formation and the amounts of heat removed from the
formation.
The process according to the invention can be employed especially in the case
of mineral oil
deposits with an average permeability of 10 mD to 4 D, preferably 100 mD to 2
D and more
preferably 200 mD to 1 D. The permeability of a mineral oil formation is
reported by the person
skilled in the art in the "darcy" unit (abbreviated to "D" or "mD" for
"millidarcies"), and it can be
determined from the flow rate of a liquid phase in the mineral oil formation
as a function of the
pressure difference applied. The flow rate can be determined in core flooding
tests with drill
cores taken from the formation. Details on this subject can be found, for
example, in K.
VVeggen, G. Pusch, H. Rischmuller in "Oil and Gas", pages 37 ff., Ullmann's
Encyclopedia of
Industrial Chemistry, online version, Wiley-VCH, Weinheim 2010. It is clear to
the person skilled
PF 71557 CA 02825360 2013-07-22
in the art that the permeability in a mineral oil deposit need not be
homogeneous, but generally
has a certain distribution, and the statement of the permeability of a mineral
oil deposit is
accordingly an average permeability.
5 The mineral oil present in the deposit has a viscosity nod of at least 3
mPa*s, especially at least
10m Pa*s (measured at the deposit temperature TO. The viscosity depends ¨ in
addition to the
temperature ¨ on factors including the type of mineral oil. According to the
type of oil, it may
also be 10 000 mPa*s or more. The viscosityflodis preferably up to 30 000
mPa*s, more
preferably 100 to 10 000 mPa*s and most preferably 20 mPa*s to 1000 mPa*s (in
each case
measured at TO.
In addition to the oil, the mineral oil formation comprises deposit water with
a greater or lesser
salt content. The salts in the deposit water may especially be alkali metal
salts and alkaline
earth metal salts. Examples of typical cations comprise Na, K+, Mg2+ or Ca2+,
and examples of
typical anions comprise chloride, bromide, hydrogencarbonate, sulfate or
borate. According to
the invention, the salt content of the deposit water is 20 000 ppm to 350 000
ppm (parts by
weight based on the sum of all components of the deposit water), for example
100 000 ppm to
250 000 ppm. The amount of alkaline earth metal ions, especially of Mg2+ and
Ca2+ ions, may
be 1000 to 53 000 ppm.
In general, the deposit water comprises one or more alkali metal ions,
especially Na + ions. In
addition, it is also possible for alkaline earth metal ions to be present, in
which case the weight
ratio of alkali metal ions/alkaline earth metal ions is generally 2,
preferably 3. The anions
present are generally at least one or more than one halide ion, especially at
least chloride ions.
In general, the amount of CI- is at least 50% by weight, preferably at least
80% by weight, based
on the sum of all anions.
Glucans used
"Glucans" are understood by the person skilled in the art to mean
homopolysaccharides formed
exclusively from glucose units. According to the invention, a specific class
of glucan is used,
specifically those glucans which comprise a main chain formed from13-1,3-
glycosidically bonded
glucose units, and side groups which are formed from glucose units and are p-
1,6-glycosidically
bonded thereto. The side groups preferably consist of a single p-1,6-
glycosidically attached
glucose unit, with ¨ viewed statistically ¨ every third unit of the main chain
13-1,6-glycosidically
bonded to a further glucose unit.
Fungal strains which secrete such glucans are known to those skilled in the
art. Examples
comprise Schizophyllum commune, Sclerotium rolfsii, Sclerotium glucanicum,
Monilinia
fructigena, Lentinula edodes or Botlytis cinera. Suitable fungal strains are
specified, for
PF 71557 CA 02825360 2013-07-22
6
example, in EP 271 907 A2 and EP 504 673 Al, claim 1 of each. The fungal
strains used are
preferably Schizophyllum commune or Sclerotium rolfsii and more preferably
Schizophyllum
commune, which secretes a glucan in which, on a main chain formed from 13-1,3-
glycosidically
bonded glucose units ¨ viewed statistically ¨ every third unit of the main
chain is
p-1,6-glycosidically bonded to a further glucose unit; in other words, the
glucan is preferably
what is called schizophyllan. Typical schizophyllans have a weight-average
molecular weight
Mw of approx. 1.5 to approx. 25*106 g/mol, especially 2 to approx.
15*106g/mol.
The production of such glucans is known in principle. For production, the
fungi are fermented in
a suitable aqueous nutrient medium. In the course of fermentation, the fungi
secrete the
abovementioned class of glucans into the aqueous fermentation broth, and an
aqueous polymer
solution can be removed from the aqueous fermentation broth.
Processes for fermenting such fungal strains are known in principle to those
skilled in the art, for
.. example from EP 271 907 A2, EP 504 673 Al, DE 40 12 238 Al, WO 03/016545 A2
and õlido
Rau, "Biosynthese, Produktion und Eigenschaften von extrazellularen Pilz-
Glucanen",
Habilitationsschrift, Techni:sche Universitat Braunschweig, Shaker Verlag
Aachen 1997", each
of which also mentions suitable nutrient media. The fermentation systems may
be continuous or
batchwise systems.
An aqueous solution comprising glucans is ultimately removed from the
fermentation broth
which comprises dissolved glucans and biomass (fungal cells, with or without
cell constituents),
leaving an aqueous fermentation broth in which the biomass has a higher
concentration than
before. The removal can especially be effected by means of single-stage or
multistage filtration,
or by means of centrifugation. It will be appreciated that it is also possible
to combine several
removal steps with one another.
In the removal, it should be ensured that the biomass is very substantially
retained. Biomass
remaining in the filtrate can block fine pores of the mineral oil formation.
The quality of the
filtrate can be determined in a manner known in principle by means of the
millipore filtration ratio
(MPFR). The test method is outlined in EP 271 907 B1, page 11, lines 24 to 48.
The MPFR of
the filtrates should be at a minimum, and especially 1.001 to 3, preferably
1.01 to 2Ø
The filtration can preferably be undertaken by means of crossflow filtration,
especially crossflow
.. microfiltration. The crossflow microfiltration process is known in
principle to the person skilled in
the art and is described, for example, in "Melia, Rautenbach, Membranvetfahren
[Membrane
processes], Springer-Verlag, 3rd edition, 2007, page 309 to page 366'.
"Microfiltration" is
understood by the person skilled in the art here to mean the removal of
particles of a size
between approx. 0.1 pm and approx. 10 pm.
In crossflow filtration ¨ for example by means of a suitable circulation pump
¨ a flow of liquid to
be filtered is applied in parallel to the surface of the membrane used as the
filtration material.
PF 71557 CA 02825360 2013-07-22
7
There is a thus a constant liquid flow over the filter membrane, and this
prevents or at least
reduces the formation of deposits on the membrane surface.
The filtrate obtained can preferably be used as such for the process according
to the invention.
It can, however, for example, be concentrated further, or the glucan can be
removed from the
solution and isolated in solid form, for example by precipitation by means of
suitable solvent,
followed by drying.
The fermentations should preferably be run such that the concentration of the
glucans to be
produced in the fermentation broth to be filtered is more than 3 g/I,
preferably at least 5 g/I and
more preferably at least 8 g/I. The concentration may especially be 5 g/I to
30 g/I and, for
example, 8 g/I to 20 g/I.
Process step (1)
To execute the invention, in a first process step (1), a concentrate (K) of a
glucan of the
structure outlined above in water with a concentration of more than 3 g/I to
30 g/I is provided.
More particularly, the concentration of the concentrate (K) is 5 g/I to 30
g/I, preferably 5 g/I to
25 g/I, more preferably 8 g/I to 22 g/I and, for example, 10 g/I to 20 g/I.
In a first embodiment of the invention, such a concentrate (K) can be produced
by dissolving
solid glucan in the desired concentration. In this embodiment of the
invention, the concentrate
can advantageously be produced on site, i.e. on the oil field or at least
close to the oil field. For
this purpose, solid glucans are supplied as a dry product, for example in big
bags. Solid glucans
can especially be produced by the method outlined above. For dissolution, the
powder can be
added, for example manually or via a conveyor belt, through a funnel, into a
stirred tank
together with water. To improve the wetting and the dissolving operation, it
is additionally
possible to add a surfactant.
The water used for dissolution may be fresh water or salt-containing water,
for example fresh
water taken from groundwater horizons, or deposit water. In offshore
applications, it is possible
to dissolve using especially seawater or processed seawater, i.e. seawater
from which some
minerals and/or sulfur compounds have been removed. When the presence of
particles in the
water is expected, it should be filtered.
In a second embodiment of the invention, the production of concentrate (K) is
undertaken by
fermenting fungal strains which secrete glucans of the structure mentioned in
an aqueous
nutrient medium, and removing an aqueous solution of the glucan formed with a
concentration
of more than 3 g/I from the aqueous fermentation broth comprising glucans and
biomass.
Details of the production method and preferred production methods have already
been
described above. The filtrate is used as such for the process. In other words,
in this method, a
PF 71557 CA 02825360 2013-07-22
8
concentrate (K) is obtained from the fermentation broth without isolating
solid glucans. This
avoids quality losses which can occur as a result of the isolation of a high
molecular polymer
and the redissolution of the high molecular weight polymer.
In this embodiment, the production of the concentrate can take place on the
oil field or close to
the oil field, or it can take place in a production facility remote from the
oil field. When the
production of the glucan takes place in a production facility remote from the
oil field, the
concentrate (K) obtained is subsequently transported to the oil field. In
order to save transport
expenditure, the concentration of the concentrate (K) is preferably at least 5
g/I and more
preferably at least 8 g/I. The concentration may especially be 5 g/I to 25 g/I
and, for example,
8 g/I to 22 g/I.
The concentrates (K) obtained can be stored intermediately before further
processing in suitable
liquid stores, for example tanks.
Process step (2)
In process step (2), the aqueous formulation (F) intended for injection is
produced by diluting
the concentrate (K) provided in step (1) with water. It is optionally possible
in this step to add
further additives, for example biocides or oxygen scavengers.
The production of the aqueous formulation (F) is undertaken on site, i.e. on
the oil field or at
.. least close to the oil field. Larger oil fields on land frequently have
central plants in which the oil
produced is processed and stored. Mineral oil produced is supplied from the
individual
production sites to the central processing plants by pipeline, and the water-
oil separation is
undertaken there. It is likewise possible to convey liquids to be injected, in
the simplest case
deposit water removed, from the central plant in pipelines to the injection
boreholes. Such
central plants should also be classified as on site". In the case of offshore
platforms,
"production on site" means of course that the production is on the platform.
For dilution, it is possible to use fresh water, or else water comprising
salts. It will be
appreciated that there may also be mixtures of different salts.
In one embodiment of the invention, seawater or partly desalinated seawater
can be used to
dilute the concentrate (K). In a further embodiment of the invention, produced
deposit water can
be used, which is reused in this manner. In the case of production platforms
at sea, the
formulation is generally diluted with seawater or with partly desalinated
seawater.
The total amount of all salts in the aqueous formulation (F) is guided by the
type of water used
to make up and to dilute the concentrate (K). The amount of the salts may be
up to
PF 71557 CA 02825360 2013-07-22
9
350 000 ppm (parts by weight), based on the sum of all components of the
formulation. Such
high values can be achieved when deposit water with a high salt content is
used both to make
up and to dilute the concentrate (K). In general, the salinity of the
formulation (F) is 20 000 ppm
to 350 000 ppm, especially 20 000 ppm to 250 000 ppm. When seawater is used to
dilute the
concentrate (K), the salt content is generally 20 000 ppm to 50 000 ppm and,
when formation
water is used, generally 100 000 ppm to 250 000 ppm. The amount of alkaline
earth metal ions
may especially be 1000 to 53 000 ppm. When alkali metal and alkaline earth
metal ions are
present, the weight ratio of alkali metal ions/alkaline earth metal ions is
generally 2, preferably
3. The anions present are generally at least one or more than one of the
halide ions,
especially at least Cl-. In general, the amount of Cl- is at least 50% by
weight, preferably at least
80% by weight, based on the sum of all anions.
The use concentration of the aqueous formulation (F) is 0.05 g/I to 3 g/I,
preferably 0.08 g/I to
0.5 g/I, and more preferably 0.1 g/I to 0.4 g/I.
The viscosity riF of the aqueous formulation (F) is, according to the
invention, at least 3 mPa*s,
preferably at least 10 mPa*s (in each case measured at 7 s-1 and TO, the
viscosity of the
aqueous formulation riF being selected in comparison to the viscosity of the
oil f oil (measured at
TO such that fi <fol. The viscosity of the aqueous formulation may thus quite
possibly be
smaller than the viscosity of the oil phase. Even when the aqueous formulation
(F) has a lower
viscosity than the oil phase, it is already possible to achieve an increase in
the oil yield
compared to the use of pure water. In one embodiment of the invention, riF
<Thi and, in a further
embodiment of the invention, 11r i5 in the range from 0.1 foil to 0.99 foil.
The desired viscosity
can be established easily via the concentration of the glucan.
In addition to the components mentioned so far, the aqueous formulation (F)
may comprise
additional components or additives.
Examples of additional components comprise one or more biocides which can be
added to
prevent polymer degradation by microorganisms. In addition, oxygen scavengers,
for example
sodium bisulfite, can be added. In a further variant, it is additionally
possible to add basic
compounds, for example alkali metal hydroxides.
Further examples of additional components comprise thickening polymers which
are chemically
different from the glucans used, for example synthetic polymers or
biopolymers.
In addition, additional components may be surfactants, especially nonionic,
anionic or
zwitterionic surfactants. The addition of surfactants allows the deoiling
action to be enhanced
further. Surfactants reduce the interfacial tension between the aqueous phase
and the oil phase
and thus enable additional mobilization of mineral oil. In a preferred
embodiment of the
invention, they are anionic and/or nonionic surfactants.
PF 71557 CA 02825360 2013-07-22
These may in principle be any nonionic, anionic or zwitterionic surfactants,
preferably nonionic
and/or anionic surfactants, provided that they are suitable in principle for
tertiary mineral oil
production. The person skilled in the art is aware of corresponding
surfactants. Suitable
surfactants for tertiary mineral oil production comprise, as hydrophobic
molecular moieties,
5 especially hydrocarbyl radicals, preferably aliphatic radicals having 10
to 36 carbon atoms,
preferably 12 to 36 carbon atoms and more preferably 16 to 36 carbon atoms.
Examples of such surfactants comprise anionic surfactants with sulfo groups,
such as
olefinsulfonates such as a-olefinsulfonates or i-olefinsulfonates, paraffin
sulfonates or
10 alkylbenzenesulfonates, nonionic surfactants such as alkyl
polyalkoxylates, especially alkyl
polyethoxylates, alkyl polyglucosides. One example of zwitterionic surfactants
is
alkylamidopropyl betaines. The surfactants may also be those which comprise
both nonionic
hydrophilic groups and anionic hydrophilic groups, for example alkyl ether
sulfonates, alkyl ether
sulfates or alkyl ether carboxylates.
In addition, the surfactants may also be oligomeric or polymeric surfactants.
Examples of such
polymeric surfactants comprise amphiphilic block copolymers which comprise at
least one
hydrophilic block and at least one hydrophobic block. Examples comprise
polypropylene oxide-
polyethylene oxide block copolymers, polyisobutene-polyethylene oxide block
copolymers, and
comb polymers with polyethylene oxide side chains and a hydrophobic main
chain, the main
chain preferably comprising essentially olefins or (meth)acrylates as
structural units.
The polymers and surfactants mentioned may be constituents of the formulation
(F), but they
may also be injected separately from the formulation (F) in the form of
aqueous formulations.
To execute process step (2), the concentrate (K), the water used for dilution
and further,
optionally used components or additives, are mixed with one another. This is
generally done
using one or more suitable mixers, for example static mixers or dynamic
mixers. Preference is
given to performing process step (2) using one or more static mixers. The
formulation (F) can
optionally be filtered once more before use in order to free the solution of
any agglomerates or
coarse particles still present. This should prevent blockage of the mineral
oil formation.
In this case, process step (2) should be undertaken such that oxygen
introduction into the
aqueous formulation (F) should be suppressed if possible or at least greatly
reduced.
Introduced oxygen can cause or at least promote a reduction in viscosity under
some
circumstances under the conditions of the formation. In a preferred embodiment
of the
invention, process step (2) should therefore be performed under oxygen-free
conditions. This
can be achieved in particular by use of closed apparatuses, and optionally the
use of protective
gas. The oxygen content in the formulation (F) before injection should
preferably not exceed
50 ppb. Any oxygen introduced in spite of this can be removed by addition of
oxygen binders to
the formulation (F).
PF 71557 CA 02825360 2013-07-22
11
Process step (3)
In process step (3), the aqueous formulation (F) is injected into the mineral
oil formation, and
crude oil is withdrawn through at least one production borehole.
The injection of the inventive aqueous formulation can be undertaken by means
of customary
apparatus. The formulation can be injected into the mineral oil formation by
means of customary
pumps through one or more injection boreholes. The injection can preferably be
effected with
positive displacement pumps. In this case, pressures of several 10s up to more
than 100 bar
may occur at the borehole head. It should be noted here that legal regulations
exist in various
countries, which limit the injection pressure on entry into the rock formation
to 1.1 times the
original deposit pressure. This limit is intended to prevent artificial
breakup of the rock formation.
The injection boreholes are typically lined with steel tubes cemented in
place, and the steel
tubes are perforated at the desired point. The formulation enters the mineral
oil formation from
the injection borehole through the perforation. The pressure applied by means
of the pumps, in
a manner known in principle, fixes the flow rate of the formulation and hence
also the shear
stress with which the aqueous formulation enters the formation. The shear
stress on entry into
the formation can be calculated by the person skilled in the art in a manner
known in principle
on the basis of the Hagen-Poiseuille law using the area flowed through on
entry into the
formation, the mean pore radius and the volume flow rate. The average
permeability of the
formation can be determined in a manner known in principle by measurements on
drill cores. Of
.. course, the greater the volume flow rate of aqueous formulation (F)
injected into the formation,
the greater the shear stress.
The rate of injection can be determined by the person skilled in the art
according to the
conditions in the formation. Preferably, the shear rate on entry of the
aqueous polymer
.. formulation into the formation is at least 30 000 s-1, preferably at least
60 000 s1 and more
preferably at least 90 000 s-1.
The crude oil produced through the production boreholes can be processed in a
manner known
in principle to the person skilled in the art. More particularly, the crude
oil is separated into a
phase comprising essentially deposit water and a phase comprising essentially
oil. The oil can
subsequently be transported into a refinery. The deposit water removed can
subsequently be
freed of oil residues in a further workup step. This may be required
especially offshore, when
the water is subsequently to be released into the sea.
In a preferred embodiment, at least a portion of the deposit water removed is
used to dilute the
concentrate (K) in process step (2). This allows a substantially closed water
circuit to be
realized.
PF 71557 CA 02825360 2013-07-22
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The process according to the invention can be effected at different times in a
deposit
development. For example, the process according to the invention can be
performed after water
flooding. In addition, it can be performed after a surfactant flooding of the
deposit. Surfactant
flooding involves injecting a suitable aqueous formulation of surfactants into
the formation. The
reduction in the water-oil interfacial tension allows surfactants to promote
the mobilization of
mineral oil. However, it is also possible to perform the process directly
after the end of primary
mineral oil production, i.e. without performing water flooding beforehand, or
¨ if primary
production is not possible due to the circumstances in the deposit ¨ directly
after the
development of the deposit. Dispensing with water flooding allows fingering or
excessive
fingering to be avoided from the outset under some circumstances.
The cumulative mineral oil production from a mineral oil deposit which can be
achieved under
economic considerations is also referred to as the final yield. This final
yield divided by the total
amount of oil originally present in the mineral oil deposit (= initial oil
content) is also referred to
as the final yield level or yield factor.
By means of the process according to the invention, it is still possible,
using glucans, even in
very hot and highly saline mineral oil deposits, to achieve a significant
increase in the mineral oil
yield when customary polymers for tertiary mineral oil production already no
longer lead to
satisfactory results.
PF 71557 CA 02825360 2013-07-22
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The examples which follow are intended to illustrate the invention in detail:
For the tests which follow, the following thickening polymers were used:
Polymer 1
Glucan with a 3-1,3-glycosidically bonded main chain and p-1,6-glycosidically
bonded side
groups (inventive)
The apparatus used to produce the glucan is shown in figure 1. It consisted of
a stirred jacketed
reservoir vessel B1 with a volume of 120 liters, the eccentric screw pump P1,
the tube bundle
heat exchanger W1, the pressure-retaining valve V1 and the two filter modules
Fl and F2. The
filter modules Fl and F2 were backflushed by means of the three-way taps V3
and V4, with
permeate at intervals of 300 s in each case, with 200 ml of permeate in each
case; the nitrogen
pressure was 7 bar. By means of the jacket of the vessel B1 and the heat
exchanger W1, the
contents of the crossflow filtration system were cooled to 24 C.
In the filter modules Fl and F2, a symmetrical tubular membrane was used,
specifically a
5-channel element from TAMI composed of ATZ ceramic
(alumina/titania/zirconia). The pore
size D90 of the membrane was 3.5 pm. The membrane was of symmetric structure
and did not
have a separating layer or intermediate layers. The length of the membrane
tube was 1 m; the
external diameter was 20 mm. The membrane area of a module element was 0.11
m2. The
hydraulic diameter of a channel was 6 mm.
For the tests, Schizophyllum commune was used; specifically, the schizophyllan
as described in
"Lido Rau, Biopolymers, ed. A. Steinbachel, Verlag WILEY-VCH, Volume 6, pages
63 to 79"
was produced in a batch fermentation. The fermentation time was 96 hours. 99.6
kg of this
fermentation broth (= feed) were introduced into vessel B1 (fig. 2) and
circulated at a circulation
rate of 7 rn3/h by means of the pump P1 at pressure 4 bar for 45 minutes. The
contents of the
vessel were analyzed and a content of 9.8 grams of schizophyllan per liter was
found.
Then the circulation rate was adjusted to 5.1 m3/h and a transmembrane
pressure of 1.1 bar
was applied. The through-flow rate was 5 m/s. The permeate leaving the filter
modules was
collected and weighed. During the first 10 minutes of the experiment, 0.75 kg
of permeate was
obtained. This corresponds to a permeate flow rate of 20.4 kg/h/m2. The
transmembrane
pressure was 2.9 bar. The filtration was operated for 16 hours and in this
time 6.18 kg of
permeate were obtained.
The collected permeate was analyzed and a glucan content of 6.7 grams per
liter was found.
The MPFR of the permeate was 2.8.
The concentrate obtained was diluted to the temperature desired in each case
for the tests.
PF 71557 CA 02825360 2013-07-22
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Comparative polymer 1:
Commercial synthetic polymer formed from approx. 75 mor/o of acrylamide and 25
mol% of
the sulfa-containing monomer 2-acrylamido-2-methylpropanesulfonic acid (sodium
salt),
weight-average molecular weight Mw of approx. 11 million g/mol
.. Comparative polymer 2:
Commercial biopolymer xanthan (CAS 11138-66-2) (biopolymer produced by
fermentation with
the bacterium Xanthamonas Campestris) with a weight-average molecular weight
M, of approx.
2 million g/mol.
Comparative polymer 3:
Commercial biopolymer diutan (biopolymer produced by fermentation with
Sphingomonas sp.)
The inventive glucans and the comparative polymers were used to perform the
viscosity
measurements described hereinafter.
Performance of the viscosity measurements:
Test instrument: shear stress-controlled Physica MCR301 rotary viscometer
pressure cell with double-gap geometry DG 35/PR/A1
Measurement range: 25 to 170 C, as specified in each case
Shear rate: as specified in each case
The complete measurement system including the syringe with which the sample is
taken and
introduced into the rheometer was purged with nitrogen. During the
measurement, the test cell
was pressurized with 8 bar of nitrogen.
PF 71557 CA 02825360 2013-07-22
Test series 1:
The viscosity of solutions of the polymers P1, V1 and V2 was measured at
different
concentrations of 0.2 g/I to 2 g/I. The measurements were carried out in
synthetic deposit water.
5 For this purpose, the polymers were dissolved in superconcentrated salt
water or ¨ in the case
that the polymer is already present as solution ¨ a solution of the polymer is
mixed with
superconcentrated salt water, and the resulting salt solution is subsequently
diluted so as to
give the concentrations stated below. The measurements of P1 and V2 was
performed at 54 C,
and the measurement of V1 at 40 C.
Composition of the deposit water (per liter):
CaCl2 42 600 mg
MgCl2 10 500 mg
NaCl 132 000 mg
Na2SO4 270 mg
NaB02*4 H20 380 mg
Total salinity 185 750 mg
The results are compiled in figure 2. Figure 2 shows that glucan P1 achieves
the best viscosity
efficiency in deposit water, i.e. the samples give the highest viscosity at a
given concentration.
Test series 2:
The viscosity of aqueous solutions of the polymers P1, V1, V2 and V3 in
ultrapure water were
measured in a concentration of in each case 3 g/I at a shear rate of 100 s-1
within the
temperature range from 25 C to 170 C. For this purpose, the solution of
polymer P1 was diluted
correspondingly, and polymers V1, V2 and V3 were dissolved in the
corresponding
concentration in water. The samples were injected into the test cell at room
temperature and the
heating rate was 1 C/min. The results are shown in figure 3.
Test series 3:
The procedure was as in test series 1, except that the solutions were made up
not using
ultrapure water but rather synthetic deposit water. The results are compiled
in figure 4.
PF 71557 CA 02825360 2013-07-22
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Comment for test series 2 and 3:
The tests show the advantages of the glucan P1 used in accordance with the
invention
compared to the comparative polymers V1, V2 and V3 at high temperature and
high salt
concentration. The viscosity of the glucan P1 remains constant both in salt-
containing water and
in ultrapure water at temperatures of 25 to 140 C, and only then begins to
decrease gradually.
In ultrapure water, both the synthetic polymer V1 (copolymer of acrylamide and
2-acrylamido-2-methylpropanesulfonic acid) and the biopolymer V3 exhibits
similar behavior,
while the biopolymer V2 is much worse. In deposit water, however, all
comparative polymers
V1, V2 and V3 are worse than the glucan P1 at relatively high temperatures.
Test series 4:
The viscosity of polymers P1, V1 and V1 as a function of shear rate was
measured in the
presence of various salts and different amounts of salts, specifically
4-1 0.1 g/I NaCl
4-2 120 g/I NaCI
4-3 0.1 g/I CaCl2
4-4 120 g/I CaCl2
4-5 deposit water of the above composition
Polymer concentration: in each case 3 g/I
Measurement temperature: 25 C
Instrument: shear stress-controlled Physica MCR Couette Geometrie
CC 27
rotary viscometer
Radius of the test body: 13.33 mm
Radius of the test cup: 14.46 mm
The samples were tested at steady-state shear beginning at high shear rates
down to low shear
rates and back again.
The results are compiled in figures 5 to 9.
In low-salinity water, all polymers exhibit a decrease in the viscosity with
increasing shear rate.
For all tests, polymer P1 is better than comparative polymers V1 and V2, i.e.
the viscosity
efficiency of polymer P1 is the best.
PF 71557 CA 02825360 2013-07-22
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In high-salinity water and deposit water, the viscosity of the two biopolymers
P1 and V2 remains
about the same, while the viscosity of the synthetic polymer V1 (copolymer of
acrylamide and
2-acrylamido-2-methylpropanesulfonic acid) is reduced very greatly.
Test series 5:
In addition, the viscosity of polymers P1 and V1 was measured as a function of
the shear rate at
different amounts of salt, specifically 0.1 g/I NaCI, 30 g/I NaCI, 60 g/I
NaCI, 120 g/I NaCI, a
mixture of 60 g/I NaCI and 57 g/I CaCl2, and deposit water of the above
composition. The test
series are shown in figures 10 and 11. The viscosity of polymer P1 is
independent of the salt
content, while the viscosity of polymer V1 is reduced very greatly even at a
salt content of 30 g/I
NaCI (corresponds roughly to seawater).
PF 71557 CA 02825360 2013-07-22
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List of figures:
Figure 1 schematic diagram of the apparatus used to prepare the glucan P1
Figure 2 dependence of the viscosity of the polymers P1, V1 and V2 on the
concentration
Figure 3 temperature dependence of the viscosity of the polymers P1, V1, V2
and
V3 in ultrapure water
Figure 4 temperature dependence of the viscosity of the polymers Fl, V1, V2
and
V3 in deposit water
Figure 5 viscosity of polymers P1, V1 and V2 in low-salinity water (0.1 g/I
NaCI) as a
function of shear rate
Figure 6 viscosity of polymers P1, V1 and V2 in high-salinity water (120
g/I NaCI) as
a function of shear rate
Figure 7 viscosity of polymers P1, V1 and V2 in low-salinity water (0.1 g/I
CaCl2) as
a function of shear rate
Figure 8 viscosity of polymers P1, V1 and V2 in high-salinity water (120
g/I CaCl2)
as a function of shear rate
Figure 9 viscosity of polymers P1, V1 and V2 in high-salinity water
(deposit water)
as a function of shear rate
Figure 10 viscosity of polymer P1 at different salt concentrations
Figure 11 viscosity of polymer V1 at different salt concentrations
