Note: Descriptions are shown in the official language in which they were submitted.
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IN-SITU MICROBIAL OXYGEN GENERATION AND HYDROCARBON CONVERSION IN A
HYDROCARBON CONTAINING FORMATION
BACKGROUND OF THE INVENTION
The invention relates to a method for in-situ oxygen
generation in a hydrocarbon containing formation.
Such a method is known from US patent 5,163,510.
The method known from this prior art reference comprises:
- injecting into the formation a fluid comprising a
source of oxygen that chemically releases oxygen into the
formation;
- inducing micro-organisms present in the formation to
multiply using the oil as their carbon source and the
chemically produced oxygen in the injection water as
their oxygen source; and
- allowing the multiplied micro-organisms to convert oil
from the environment.
In this known method the source of oxygen is provided
by injecting water comprising an oxidizing compound
selected from the group consisting of H202, NaC1O3, KC1O4,
NaNO3 and combinations thereof, which are assumed to be
chemically converted to result in oxygen. This assumption
is based on the fact that oxygen generation from
Microbial Chlorate Reduction was for the first time
reported in 1996 by van Ginkel at al in 1996, Archives of
Microbiology 166:321-326.
In accordance with the teachings of US patent
5,163,510 the chemically generated oxygen is then used by
microbes to convert hydrocarbons.
Limitations of the use of the known oxidizing
compounds known from US patent 5,163,510 for chemical
oxygen generation are that H202 may dissociate during or
shortly after the injection process, and that chemical
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conversion of NaNO3r NaClO3 and KC1O4do not generate oxygen
at temperatures lower than 1200 Celsius.
Moreover, the microbes Pseudomonas putida, Pseudomonas
aeruginosa, Corynebacterium lepus, Mycobacterium rhodochrous
and Mycobacterium vaccae disclosed in US patent 5,163,510
are non-thermophilic micro-organisms, which are unable to
reduce chlorate and/or multiply at temperature of at least
60 C. This will prevent the method known from US patent
5,163,510 to be beneficial for application throughout an
entire hydrocarbon containing formation as the ambient
temperature in a hydrocarbon containing formation often
exceeds 60 C.
The use of microbial chlorate reduction as mechanism for
in-situ oxygen generation and thereby stimulating microbial
activity using hydrocarbons as carbon and energy source has
been reported for the bioremediation of hydrocarbon spills
at ambient atmospheric temperatures in the following prior
art references:
- Coates et al., 1998, Nature 396(6713): 730
- Coates et al., 1999, Applied Environmental Microbiology
65(12): 5234-5341
- Coates et al., 2004, US patent 2004/0014196A1 , which
prior art references are collectively referred to as Coates
et al (1998, 1999, 2004)
- Tan et al., 2006, Biodegradation 17(1): 113-119
- Mehboob et al., 2009: Applied Microbiology and
Biotechnology 83(4): 739-747
- Langenhoff et al., 2009, Bioremediation Journal, 13(4):
180-187
There is a need to provide an method for in-situ
thermophilic microbial oxygen generation wherein a
controlled amount of oxygen is microbiologically produced
in-situ deeper in the hydrocarbon containing formation where
the temperature is at least 60 C.
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There is furthermore a need to provide an enabling
process for the stimulation of in-situ thermophilic
microbial conversion of hydrocarbons wherein oxygen is
microbiologically produced from the injected oxygen source
only at high temperature locations in a hydrocarbon
containing formation where injected or indigenous micro-
organisms encounter the injected electron acceptor in
addition to an electron donor, such as hydrocarbons,
volatile fatty acids, etc.
There is also a need for a method for thermophilic
microbial oxygen generation through chlorate reduction at
the oil water interface, in contrast to chemical generation
of oxygen known from US patent 5,163,510 that can also occur
in oil-poor parts of the reservoir.
Utilization of microbes to enhance hydrocarbon recovery
is hampered by the limited bioavailability and
biodegradability of the hydrocarbons under hot reservoir
conditions.
Thus there is also a need to provide a way to improve
bioavailability and biodegradability in hot hydrocarbon
containing formations where the ambient temperature is at
least 60 C.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a
method for in-situ oxygen generation in an underground
hydrocarbon containing formation, the method comprising
injecting into the formation an oxygen generating
composition which releases oxygen (02) by reduction of
chlorate (C103-), wherein:
- the formation has a temperature of at least 60 C;
- the composition comprises thermophilic chlorate reducing
micro-organisms, which multiply at an ambient temperature of
at least 60 C,; and
- the multiplied thermophilic chlorate reducing micro-
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organisms convert the hydrocarbons and/or other pore fluids
in-situ into transportable or disposable products.
In an embodiment the thermophilic chlorate reducing
micro-organisms comprise bacteria of the genus
Archaeoglobus, Geobacillus and/or Thermus and use hydrogen
(H) and electrons(e) provided by hydrocarbons, volatile
fatty acids and/or other pore fluids in the formation
followed by dismutation of chlorite(Cl02-) by the micro-
organisms on the basis of the reactions:
C103 + 2H+ +2e -> C102- +H20
C102 -> Cl- +02
In a suitable embodiment the thermophilic chlorate
reducing micro-organisms multiply at an ambient temperature
of at least 800 C and comprise bacteria of the genus
Archaeoglobus fulgidis.
Optionally, the method according to the invention
furthermore comprises:
- injecting into the formation an oxygen generating
composition, which comprise or generates chlorate in the
formation and which releases oxygen (02) by thermophilic
microbial reduction of chlorate(C103) by the micro-
organisms, using hydrogen (H) and electrons (e) provided by
the hydrocarbons, volatile fatty acids and/or other pore
fluid components, such as oil & gas contaminants such as H2S,
thiophenes and mercaptanes, followed by dismutation of
chlorite (C102) by micro-organisms on the basis of the
reactions:
C103 + 2H+ +2e -> C102- +H20
C102- -> Cl- +02;
- inducing multiplication of the thermophilic chlorate-
reducing micro-organisms (Archaeoglobus, Geobacillus,
Thermus), other chlorate-reducing thermophilic micro-
organisms and other micro-organisms that can use the
hydrocarbons, volatile fatty acids and/or other pore fluid
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components (e.g. oil & gas contaminants as H2S, thiophenes
and mercaptanes) as their carbon source and/or electron
donor and the injected composition or the oxygen generated
by thermophilic chlorate reduction thereby as their electron
5 acceptor and/or oxygen source; and
- inducing the multiplied micro-organisms to convert the
hydrocarbons and/or other pore fluid components in-situ into
transportable products, such as in Microbial Enhanced Oil
Recovery(MEOR) and/or ECBM Enhanced Coal Bed Methane(ECBM)
processes.
The multiplied thermophilic micro-organisms generated
in accordance with the method according to present
invention may be used for in-situ conversion of coal,
shale oil, oilshale, bitumen and/or a viscous crude oil
into a synthetic crude oil with a reduced viscosity
and/or to convert associated contaminants, such as H2S,
thiophenes and mercaptanes, into oxidized sulfur
fractions that remain within the reservoir brine.
The method according to the invention may be used to
improve bioavailability and biodegradability of
hydrocarbons at thermophilic (60 - 120 C) & anaerobic
conditions in underground formations containing
hydrocarbons, volatile fatty acids and other pore fluid
components and micro-organisms, by the process of
Thermophilic Microbial Chlorate Reduction. The process
will generate oxygen in-situ that will enhance
bioavailability and biodegradability, which subsequently
will enables enhanced recovery of hydrocarbons (of
improved quality) via other process like Microbial
Enhanced Oil Recovery (MEOR), Microbial Enhanced Coalbed
Methane (MECBM) or pretreatment of heavy hydrocarbon
crudes (heavy oil, bitumen) prior to processes as Steam
Assisted Gravity Drainage (SAGD).
The oxygen generating composition may comprise
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perchlorate (Cl04-) from which chlorate(Cl03-) is
generated using electrons released by hydrocarbons,
volatile fatty acids and/or other pore fluid components
(e.g. oil & gas contaminants as H2S, thiophenes and
mercaptanes) as electron donor on the basis of the
following reaction:
C104- + 2H+ + 2e -> C103 + H20.
The hydrocarbons may comprise viscous crude oil, coal
and/or other long chain hydrocarbons and the micro-
organisms may comprise thermophilic (per)chlorate-
reducing bacteria or archaea, such as archaea and
bacteria of the genus Archaeoglobus, Geobacillus, Thermus
and/or other thermophilic genera able to reduce chlorate
and convert fatty acids or long chain hydrocarbons into
short chain hydrocarbons being indigenous to the
formation or introduced by injection.
The other pore fluid components may comprise fatty
acids, natural gas contaminants; H2S, thiophenes, and
mercaptanes, in which case the micro-organisms may
comprise archaea and bacteria of the genus Archaeoglobus,
Sulfolobus, Ferroglobus, Thiobacillus, Thiomicrospira or
other genera able to convert natural gas contaminants.
These and other features, embodiments and advantages
of the method according to the invention are described in
the accompanying claims, abstract and the following
detailed description of a non-limiting hypothetical
example.
The present invention novelty compared to the
inventions previously reported resides in:
Providing a microbial chlorate-reducing and oxygen-
generating process (i.e. different from the invention of
US patent 5,163,510, in which oxygen is assumed to be
chemically produced (not by chlorate-reducing
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microorganisms) and only assumes microbial utilization of
oxygen);
Providing such microbial chlorate-reducing and
oxygen-releasing process that can operate at high
temperatures in the range from 60 C up to 120 C
relevant to hydrocarbon containing reservoirs.
The microbial method according to the invention can
operate at an elevated temperature of at least 600 C and
is therefore different from the bioremediation method
disclosed in US patent application 2004/0014196 Al
(Coates), which releases oxygen at temperatures < 40 C
and the method known from US patent 5,163,510 that
enables the use of micro-organisms at a temperature below
60 C (but not higher) and therefore seriously limits the
application of the known method in hot hydrocarbon
containing formations.
The thermophilic microbial chlorate-reducing and
oxygen-releasing method according to the invention
enhances bioavailability and biodegradability of
hydrocarbons, which subsequently enables enhanced
recovery of upgraded hydrocarbons from hydrocarbon
containing formations optionally by:
a) enhanced oil recovery from oil bearing formations
(MEOR),
b) enhanced methane production of coal reservoirs (ECBM),
c) pretreatment of heavy oil deposits before SAGD
operation; and
d) in-situ conversion of oil and natural gas
contaminants; H2S, thiophenes and mercaptanes, which
conversion involves decontamination of hydrocarbons and
is therefore different from US patent 2004/0014196A1,
which aims to bioremediate hydrocarbons in a shallow low
temperature environment or US patent 5,163,510, which
aims to stimulate MEOR only.
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The method according to the invention generates
oxygen in-situ that will enhance bioavailability and
biodegradability, which subsequently will enable enhanced
recovery of hydrocarbons (of improved quality) via other
process like Microbial Enhanced Oil Recovery (MEOR),
Microbial Enhanced Coalbed Methane (MECBM) or
pretreatment of heavy hydrocarbon crudes (heavy oil,
bitumen) prior to processes as Steam Assisted Gravity
Drainage (SAGD). The process can also enable in-situ
natural gas contaminant removal resulting in upgraded
hydrocarbons. The invention should therefore be
considered as a strong enabling process for other
subsurface thermophilic microbial processes.
When used in this specification and claims the term
thermophilic chlorate reducing micro-organisms means that
these micro-organisms multiply at an ambient temperature
of at least 60 C.
These and other features, embodiments and advantages
of the method according to the invention are described in
the accompanying claims, abstract and the following
detailed description of non-limiting embodiments depicted
in the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG.1 shows the consumption of lactate as an electron
donor and conversion of chlorate to chloride at 85 C by
the thermophilic Archaeoglobus fulgidus DSM4139
microorganism in laboratory experiment that demonstrates
the viability of the method according to the invention at
an elevated temperature.
DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENT
FIG.1 shows the results of a laboratory experiments
which demonstrated that Archaea from the genus
Archaeoglobus can perform chlorate reduction at
temperatures up to 85-95 C.
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Archaeoglobus have often been encountered in
hydrocarbon containing high temperature reservoirs as
evident from molecular and cultivation experiments.
Moreover, members of this genus have been shown to be
able to convert fatty acids and alkanes. Members of this
genus therefore are one of the most relevant candidates
for the thermophilic microbial chlorate-reduction
process.
FIG.1 illustrates the results of a laboratory
experiment in which lactate was consumed as electron
donor and chlorate was converted into chloride at 85 C
by the micro-organism comprising bacteria of the genus
Archaeoglobus fulgidus DSM4139.
It is observed that thermophilic microbial
(Per)Chlorate Reduction at a temperature of at least 60 C
has never been described in the prior art for hot
hydrocarbon containing environments with fatty acids or
hydrocarbons as electron donor and that the experiment
revealed that bacteria of the genus Archaeoglobus
fulgidus DSM4139 will have an unexpectedly good
performance for thermophilic microbial (Per)Chlorate
Reduction in a hot hydrocarbon containing formation at an
ambient temperature of at least 60 C.
EXAMPLE
A suitable embodiment of the method according to the
invention, comprises the following steps:
a)Screening whether a target underground crude oil and/or
natural gas containing reservoir formation has features,
such as temperature, salinity, heterogeneity, oil
characteristics, micro-organisms, volatile fatty acids,
hydrogen ions, acetate, propionate or butyrate and/or
other potential electron donors, etc., which allow use of
the method according to the invention;
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b)Analyzing the composition of the water, oil and/or
natural gas in the formation, for example by screening a
sample taken from the formation;
c)Identification of potentially interesting micro-
organisms with molecular DNA technologies using either
general (16S rRNA-related) primer sets or
enzyme/functional group specific primer sets
(nitrate/nitrite-reductase, (per)chlorate reductases,
chlorite dismutase, or hyrdrocarbon (alkane) degrading
enzymes or using metagenomics;
d)Isolation of potentially interesting indigenous
microbes from available core, formation water, and oil
samples using VFA's (acetate, proprionate,
butyrate,etc.), hydrocarbon components (e.g. long chain
alkanes) or typical gas contaminants (e.g. H2S) as
electron donor and nitrate, oxygen or perchlorate,
chlorate or chlorite as electron acceptor.
e)Determination of the optimal nutrient mix (electron
donor, N/P nutrient, trace elements, SRB-inhibiting
chemicals, etc.) using the identified and/or cultivated
micro-organisms;
f)Microbial incubations using the potential successful
nutrient compositions and gas contaminants, VFA's or oil
components (e.g. long chain alkanes) to prove microbial
activity on lab scale;
g)Optional middle phase could be to verify chance of
success by core flood experiments; and
e)The following actual chemical injection and in-situ
conversion procedure:
el) Shut-in and clean-up of a near wellbore area of the
crude oil, tar sand, shale oil, natural gas and/or other
hydrocarbon containing reservoir formation (either
chemically or by flushing);
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e2)Injection of microbial cultures (single species or
consortia derived from enrichments inoculated with
production fluids from the treated reservoir) into the
formation to boost the required indigenous microbial
species;
e3) Injection of optimized nutrient mixture (main
components being: oxygen, perchlorate and or chlorate
and/or nitrate possibly continuously but more likely
push-wise to avoid the development of a chlorate-
utilizing biofilm limited to the wellbore to ensure deep
placement into the reservoir formation and thereby
stimulating the required indigenous microbial community;
and
e4) Monitoring of the in-situ conversion method according
to the invention based on increase in oil production,
change in water-cut, change in produced oil and/or
natural characteristics and/or composition, detection of
target micro-organism(s) using molecular DNA technologies
and/or cultivation dependent screening.
