U.S. patent application number 13/241361 was filed with the patent office on 2012-09-27 for control of fluid flow during treatment of subterranean sites using well fluid injection.
This patent application is currently assigned to E. I. DU PONT DE NEMOURS AND COMPANY. Invention is credited to ALBERT W. ALSOP, Scott Christopher Jackson.
Application Number | 20120241148 13/241361 |
Document ID | / |
Family ID | 45938620 |
Filed Date | 2012-09-27 |
United States Patent
Application |
20120241148 |
Kind Code |
A1 |
ALSOP; ALBERT W. ; et
al. |
September 27, 2012 |
CONTROL OF FLUID FLOW DURING TREATMENT OF SUBTERRANEAN SITES USING
WELL FLUID INJECTION
Abstract
Disclosed herein is a method to control distribution of injected
microorganisms, nutrients or other chemical treatment fluids from a
single injection well to multiple production wells. The sweep
efficiency is improved preventing premature production of fluids
from production wells with short breakthrough times. This is a
useful technique for treatment of subterranean target sites for
practice of Microbial Enhanced Oil Recovery and bioremediation.
Inventors: |
ALSOP; ALBERT W.;
(Wilmington, DE) ; Jackson; Scott Christopher;
(Wilmington, DE) |
Assignee: |
E. I. DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
45938620 |
Appl. No.: |
13/241361 |
Filed: |
September 23, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61387494 |
Sep 29, 2010 |
|
|
|
Current U.S.
Class: |
166/246 ;
166/270.1 |
Current CPC
Class: |
C09K 8/582 20130101;
E21B 43/20 20130101 |
Class at
Publication: |
166/246 ;
166/270.1 |
International
Class: |
E21B 43/22 20060101
E21B043/22 |
Claims
1. A method for treatment of a subterranean target site comprising
the steps of: a) determining fluid flow patterns of injection fluid
between an injection well and one or more production wells in the
subterranean site; b) injecting a well treatment fluid in the
subterranean site; and c) controlling the distribution of the well
treatment fluid amongst the production wells, wherein oil recovery
is improved.
2. The method of claim 1 wherein determining fluid flow patterns of
injection fluid is by reservoir modeling, tracer testing, or
approximation methods,
3. The method of claim 1 wherein controlling the distribution of
the well treatment fluid is by selective shut off or flow
restriction of one or more production wells.
4. The method of claim 1 wherein the well treatment fluid is
selected from the group consisting of a chemical treatment fluid, a
polymer fluid, a surfactant fluid, a high pH fluid, a low salt
fluid, and combinations thereof.
5. The method of claim 4 wherein the chemical well treatment fluid
is a nutritional chemical fluid for feeding native microorganisms
in said subterranean target site.
6. The method of claim 4 wherein the chemical treatment fluid is a
suspension of exogenous microorganisms in a nutritional chemical
fluid.
7. The method of claim 4 wherein said polymer fluid consists of
carboxymethylcellulose, hydroxyethylcellulose,
carboxymethylhydroxyethyl-cellulose, guar gum, hydroxypropyl guar.
carboxymethylhydroxypropyl guar, polyacrylamide, polyamines,
xanthan, polysaccharides or polyvinyl-alcohol derivatives, or a
combination therefrom.
8. The method of claim 4 wherein said surfactant consists of
anionic sulfonates, nonionics (ethylene oxide derivatives),
quaternary ammonium compounds, fluorosurfactants, amphoterics or
glycol ethers, or a combination therefrom.
9. The method of claim 4 wherein said high pH fluid comprises a
material with a pKa greater than 10, wherein the material consists
of sodium silicate, sodium hydroxide or sodium carbonate, or a
combination therefrom.
10. The method of claim 6 wherein the exogenous microorganisms
comprise one or more species of: Pseudomonas, Bacillus,
Actinomycetes, Acinetobacter, Arthrobacter, Schizomycetes,
Corynebacteria, Achromobacteria, Arcobacter, Enterobacteria,
Nocardia, Saccharomycetes, Schizosaccharomyces, Vibrio, Shewanella,
Thauera, Petrotoga, Microbulbifer, Marinobacteria, Fusibacteria,
and Rhodotorula.
11. The method of claim 4 wherein a combination of polymer,
surfactant, and high pH fluids is used together.
12. The method of claim 4 wherein polymer, surfactant and high pH
fluids are used in sequence.
Description
[0001] This application claims the benefit of U.S. Provisional
Application 61/387,494, filed Sep. 29, 2010.
FIELD OF INVENTION
[0002] This disclosure relates to the field of enhanced oil
recovery or bioremediation. More specifically, it relates to
controlling flow of treatment fluids and/or microorganisms into
subterranean strata to enhance oil recovery or bioremediation.
BACKGROUND OF THE INVENTION
[0003] Primary techniques used in oil recovery which utilize only
the natural forces present at an oil well site allow recovery of
only a minor portion of the crude oil present in an oil reservoir.
Oil well sites are locations where wells have been drilled into a
subterranean stratum, containing oil, with the intent to produce
oil from that stratum. An oil reservoir typically refers to a
deposit of subterranean oil in a subterranean stratum. Secondary
oil recovery methods, such as water flooding, that is injection of
water through injection wells into the oil reservoir, have been
used to force oil through the subterranean strata toward production
wells and thus improve recovery of the crude oil (Hyne, N. J.,
2001, "Non-technical guide to petroleum geology, exploration,
drilling, and production", 2nd edition, Pen Well Corp., Tulsa,
Okla., USA). Production and injection wells are channels made by a
well bore from the surface to the subterranean oil bearing strata
with enough size to allow for pumping of fluids either from the
surface and into the strata (injection wells) or from the strata to
the surface (production wells). Configuration of injection and
associated production wells for enhanced oil recovery and
bioremediation may take many forms, as is well known in the art
("Standard Handbook of Petroleum & Natural Gas Engineering",
2nd Edition, Editors, William C. Lyons, Ph.D., P.E., Gary J.
Plisga, B.S., Gulf Publishing, Elsevier, Burlington, Mass.,
USA).
[0004] Enhanced oil recovery (EOR) methods that utilize surfactant,
polymer, alkali and microbial treatments have been known to improve
water flooding performance of subterranean target sites.
Subterranean target sites refer to any subterranean site that is
subject to treatment for EOR, microbial enhanced oil recovery
(MEOR) or bioremediation. As water moves through the reservoir, it
displaces oil therein to one or more production wells through which
the oil is recovered. One problem commonly encountered with water
flooding operations is that the heterogeneity of the subterranean
strata can lead to reduced sweep efficiency of the water. Sweep
efficiency is related to the fraction of the oil-bearing
subterranean stratum that has seen water passing through it in
order to move oil to the production wells. Sweep efficiency can be
reduced by several factors such as high permeable streaks, geometry
of the wells and the strata, and viscous fingering. In such cases,
water preferentially channels through the watered-out strata of the
oil reservoir as it travels from the injection well to the
production wells, thus bypassing the subterranean oil-bearing
strata that are not watered-out. In watered-out areas the injection
water has preferentially flowed through these strata and has
removed most of the oil in that strata in contrast to adjacent
strata that have seen little or no water.
[0005] Various methods have been used to combat poor sweep
efficiency. U.S. Pat. No. 4,561,500 describes a method of reducing
permeability of the underground formation by injecting
microorganisms capable of producing insoluble exopolymers which
accumulated in higher permeability zones. WO2005005773 describes
increasing sweep efficiency during oil recovery by injecting a
consortium of microorganisms that produce surfactants. U.S. Pat.
No. 3,771,598 discloses injection of a mobilizing fluid into an
injection well at a predetermined pressure and increasing the
pressure in the formation by throttling outflow at the production
well. U.S. Pat. No. 4,184,549 discloses application of a
low-viscosity fluid which forms a high-viscosity coarse emulsion
with residual hydrocarbons thus reducing the permeability of the
stratum to fluids.
[0006] With the ever-increasing demand on oil, there is a constant
need for methods to improve recovery of oil from oil reservoirs
thus development of novel techniques to improve sweep efficiency
during EOR is desired.
SUMMARY OF THE INVENTION
[0007] The disclosed method is a method for treatment of a
subterranean target site during oil recovery or bioremediation by
controlling distribution of a well treatment fluid into said target
site, the method comprising the steps of: [0008] a) determining
fluid flow patterns of injection fluid between an injection well
and one or more production wells in the subterranean site; [0009]
b) injecting a well treatment fluid in the subterranean site; and
[0010] c) controlling the distribution of the well treatment fluid
amongst the production wells,
[0011] wherein oil recovery is improved.
BRIEF DESCRIPTION OF FIGURES OF THE INVENTION
[0012] FIG. 1 depicts an inverted five spot injection well (1) and
production wells (2) system.
DETAILED DESCRIPTION OF THE INVENTION
[0013] According to the disclosed method, during treatment of a
subterranean target site, for EOR or bioremediation, fluid flow is
controlled to ensure that well treatment fluids flow from the
injection well to all of the surrounding production wells and are
distributed throughout the subterranean strata so that adequate
volumes of well treatment fluids flow to all areas of the
subterranean strata without bypassing some areas and without
excessive loss of fluids out of one or more production wells with
short breakthrough time. The volume of fluid that can be produced
from a production well between the time a well treatment fluid is
introduced at an injection well and the time that a significant
amount of that well treatment fluid is seen at a production well is
known as the "breakthrough volume" for that injection and
production well pair. At a constant flow rate of production, the
elapsed time required for a breakthrough volume to be produced is
defined as the "breakthrough time" for that injection and
production well pair. "Short breakthrough time", as used herein,
refers to a breakthrough time that is shorter than the time
required for the well treatment fluid to affect the desired changes
in the subterranean target site and improve sweep efficiency. For
example, it can be the time required for MEOR microorganisms to
consume nutrients in nutritional chemical fluids used as treatment
fluids (e.g., less than one day for low salt fluids, and less than
5 days for high salt fluids). Low salt fluids are those well
treatment fluids that contain less than 17 parts per thousand (ppt)
of sodium chloride (hereafter referred to as "salt") and high salt
fluids are well treatment fluids that contain 50-60 ppt or higher
levels of salt.
[0014] One example of a suitable configuration of an injection well
and associated production wells in an oil reservoir, which is a
subterranean target site, is shown in FIG. 1. The single injection
well (1) is in the center of the pattern and is labeled as "I".
There are four flow paths illustrated with arrows pointing away
from this single injection well to the production wells (2): P-1,
P-2, P-3 and P-4. Other flow paths are possible depending on the
nature of the rocks at the subterranean target site.
[0015] Any one of the flow paths illustrated in FIG. 1 can take
significantly more of the introduced well treatment fluid and
channel it to a particular production well and thus bypass parts of
the subterranean target site. This phenomenon can cause treatment
of only some parts of the subterranean target site and loss of well
treatment fluids out of one or more producing wells before the well
treatment fluid can affect the desired changes necessary to improve
sweep efficiency and to increase oil production from the
subterranean target site. The method disclosed herein allows for
detection and elimination of this undesirable bypassing.
[0016] The fluid useful for water flooding according to the present
method comprises water. Water can be supplied from any suitable
source, and can include, for example: sea water, brine, production
water, water recovered from an underground aquifer, including those
aquifers in contact with the oil, or surface water from a stream,
river, pond or lake. As is known in the art, it may be necessary to
remove particulate matter including dust, bits of rock or sand and
corrosion by-products such as rust from the water prior to
injection into the one or more well bores. Methods to remove such
particulate matter, e.g., filtration, sedimentation and
centrifugation, are well known in the art.
[0017] According to the disclosed method, before starting use of
any treatment fluid, such as chemical treatment fluids optionally
including microorganisms, an analysis of the fluid flow pattern
between an injection well and one or more production wells in the
target subterranean site and the breakthrough volumes of the
production wells is made. Reservoir modeling, tracer testing,
approximation methods, or any other method well known in the art
can be used to estimate the breakthrough volume of any production
well.
[0018] In the currently disclosed method determination of
distribution of the well treatment fluid allows identification of
any particular flow path (e.g., as illustrated in FIG. 1) which
takes significantly more of the well treatment fluid and channels
it to a particular production well thus bypassing some parts of the
subterranean target site. Chemical or radioisotope tracer tests are
common methods used in the oil industry to determine such bypassing
and are suitable for use in the present invention. Tracer chemicals
used for this purpose include anions such as bromine, iodine, and
nitrate or dyes such as the sodium salt of Fluorescein dye,
commonly known as Uranine (CAS 518-47-8, Part number A833-500,
Fisher Scientific, Pittsburgh, Pa.). Radioisotope tracers such as
hexacyanocobaltate, thiocyanate, tritiated water, halides or
alcohols that contain radioisotope elements like Cobalt 60, Cobalt
58, Cobalt 57, Carbon 14, Tritium, Sulfur 35, Chlorine 36 or Iodine
125 are often used for tracer tests.
[0019] In the currently disclosed method, when lack of distribution
of fluid to some parts of the subterranean target site is found and
it is determined that some production wells have short breakthrough
times which would result in unacceptable loss of well treatment
fluid through bypassing between the injection well and one or more
production wells, the flow through these production wells is
controlled during treatment to allow distribution of the well
treatment fluid throughout the subterranean target site and in
particular to the areas that have not been watered-out.
[0020] By using the determined breakthrough times for several
injection to production well pairings it is possible to
sequentially restrict (or throttle) the flow of treatment fluid by
partially closing the production valves or alternatively completely
shutting off the flow from the production wells with short
breakthrough times. This allows the treatment fluid to penetrate
throughout the subterranean strata between the injection well and
production wells with longer breakthrough times, and to provide for
treatment across an entire subterranean target site. As used
herein, the terms "restricting or throttling the flow" refers to
reducing the flow from one or more production wells in order to
allow the well treatment fluid to get distributed through the
subterranean target site.
[0021] In instances where MEOR is used, sequential shut off or
throttling of production wells allows microbial inocula to be
distributed into the subterranean strata thus allowing the
nutritional chemical fluids and the inocula to move deeper into the
reservoir without losing the inoculum and/or the nutritional
chemical fluid through production wells with short breakthrough
times. As used herein, the terms "inoculum and inocula", refer to
microorganisms introduced into an injection well in a well
treatment fluid.
[0022] In the current method, "nutritional chemical fluids" refers
to a fluid used for growth and colonization of either native
microorganisms of the subterranean target site or exogenously added
microorganisms for MEOR applications. "Native microorganisms", as
used herein, refers to a variety of microorganisms that naturally
exist in the subterranean target site. "Exogenous microorganisms"
or "exogenously added microorganisms" refers to microorganisms that
are grown outside of the subterranean target site and then
introduced into the site. This may include microorganisms that were
isolated from the target or other subterranean site and then grown
outside of the subterranean site before introduction.
[0023] In one embodiment, the well treatment fluid can be a
chemical treatment fluid and can comprise one or more polymeric
fluids. Polymeric fluids useful for the current method include, but
are not limited to, water soluble polymers such as
carboxymethylcellulose, hydroxyethylcellulose,
carboxymethylhydroxyethylcellulose, guar gum, hydroxypropyl guar,
carboxymethylhydroxypropyl guar, polyacrylamide, polyamines,
xanthan, polysaccharides or polyvinylalcohol derivatives as those
disclosed in commonly owned U.S. Pat. No. 7,6677,305, or polymers
of 1,3 propanediol as disclosed in commonly owned and co-pending
U.S. Patent Application 20090197779, which are herein incorporated
by reference in their entireties.
[0024] In another embodiment, the chemical treatment fluids may
also comprise one or more surfactants. The one or more surfactants
useful for the current method include, but are not limited to:
anionic sulfonates, nonionics (ethylene oxide derivatives),
quaternary ammonium compounds, fluorosurfactants, amphoterics and
glycol ethers or a mixture thereof.
[0025] In another embodiment, the chemical treatment fluid may
comprise at least one base having pKa above 10 wherein the
resulting pH of the well treatment fluid is greater than 10. Bases
useful in the practice of the present invention include, but are
not limited to: sodium silicate, sodium hydroxide or sodium
carbonate or a mixture thereof. The treatment can include any
combination of polymer, surfactant and alkali treatment chemicals
used at once or used in sequence. The treatment fluid may also be a
low salt fluid.
[0026] The treatment fluid can also be composed of a nutritional
chemical fluid used by microorganisms to grow and to express a
biological function resulting in improved oil recovery. The
nutritional chemical fluid may contain a suspension of
microorganisms. Microorganisms (i.e., native microorganisms or
exogenously added microorganisms) can be used in the current method
to improve sweep efficiency and/or reduce residual oil saturation
of rock in the subterranean site. Many microorganisms live in
various parts of subterranean strata and comprise the native
microorganisms of such strata. According to the current method, in
one embodiment, nutritional chemical fluids are introduced into the
subterranean strata which encourage colonization and propagation of
the native microorganisms in more permeable strata where they plug
the pores of the permeable strata and thus block water flow through
them. Native microorganisms or exogenous microorganisms that grow
in a subterranean site using nutritional chemical treatment fluids
may also release oil from rock thereby reducing residual oil
saturation.
[0027] In the current method, microorganisms can be exogenously
added to improve sweep efficiency and/or reduce residual oil
saturation. Microorganisms useful in the current method can
comprise classes of facultative anaerobes, obligate anaerobes and
denitrifiers. Various species of microorganisms (bacteria and
fungi) that can be used to improve sweep efficiency and enhance oil
recovery include, but are not limited to, the genera: Pseudomonas,
Bacillus, Actinomycetes, Acinetobacter, Arthrobacter,
Schizomycetes, Corynebacteria, Achromobacteria, Arcobacter,
Enterobacteria, Nocardia, Saccharomycetes, Schizosaccharomyces,
Vibrio, Shewanella, Thauera, Petrotoga, Microbulbifer,
Marinobacteria, Fusibacteria, and Rhodotorula. The terms "genus"
and "genera", as used herein, refer to the category of
microorganisms ranking below a "family" and above a "species" in
the hierarchy of taxonomic classification of microorganisms. The
term "species" refers to a group of microorganisms that share a
high degree of phenotypic, biochemical and genotypic
similarities.
[0028] In various embodiments the inoculum can comprise only one
particular species, or two or more species of the same genera, or a
combination of different genera of microorganisms.
[0029] If well treatment fluids comprising microorganisms are used
for improving sweep efficiency, then chemical well treatment fluid
can comprise one or more nutritional chemical fluids. Nutritional
chemical fluids useful in the present invention include those
containing at least one of the following elements: C, H, O, P, N,
S, Mg, Fe, or Ca. By way of example only, inorganic compounds that
may be used include PO.sub.4.sup.2-, NH.sub.4.sup.+,
NO.sub.2.sup.-, NO.sub.3.sup.-, and SO.sub.4.sup.2- amongst others.
Techniques and various suitable nutrient-containing fluids for
growth and maintenance of facultative and strict anaerobic
microorganisms are well known in the art.
[0030] Growth substrates can include sugars, organic acids,
alcohols, proteins, polysaccharides, fats, hydrocarbons or other
organic materials known in the art of microbiology to be subject to
microbial decomposition. Major nutrients containing nitrogen and
phosphorus (non-limiting examples can include NaNO.sub.3,
KNO.sub.3, NH.sub.4NO.sub.3, Na.sub.2HPO.sub.4, K.sub.2HPO.sub.4,
NH.sub.4Cl); vitamins (non-limiting examples can include folic
acid, ascorbic acid, and riboflavin); trace elements (non-limiting
examples can include B, Zn, Cu, Co, Mg, Mn, Fe, Mo, W, Ni, and Se);
buffers for environmental controls; catalysts, including enzymes;
and both natural and artificial electron acceptors.
EXAMPLES
[0031] The present invention is further defined in the following
Examples. It should be understood that these Examples, while
indicating preferred embodiments of the invention, are given by way
of illustration only. From the above discussion and these Examples,
one skilled in the art can ascertain the essential characteristics
of this invention, and without departing from the scope thereof,
can make various changes and modifications of the invention to
adapt it to various usages and conditions.
Abbreviations Used in the Examples
[0032] "h" means hour(s); "L" means litre; ".degree. C." means
degrees Celsius; "mg" means milligram(s); "mm" means millimeter;
"kg" means kilogram(s); "ppt" means part per thousand; "mM" means
millimolar; "%" means percent; "min" means minute(s); "mL/min means
milliliter per minute; "D" means day(s); ".mu.g/L" means microgram
per liter; "nM" means nanomolar; ".mu.M" means micromolar.
Example 1
Prophetic
To Determine Breakthrough Times in Production Wells
[0033] The breakthrough time for each production well is determined
using a tracer chemical such as a sodium salt of Fluorescein dye,
commonly known as Uranine (CAS 518-47-8, Part number A833-500,
Fisher Scientific, 2000 Park Lane Drive, Pittsburgh, Pa.
15275).
[0034] Uranine (2.7 kilogram, kg) is added to a tank containing
9,000 L of water. The normal flow of injection water to the
injection well to be tested is shut off. The Uranine treated water
is injected over a 7.2 hours (h) period into the injection well at
a rate of injection equal to 1,250 L/h which is the normal
injection flow rate. Upon completion of the injection of the 9,000
L of Uranine solution, the normal injection flow of water is
restored at the normal injection rate of 30,000 L/D. After the
start of Uranine injection, samples are taken from the associated
production wells at various time intervals for example, 6, 12, 18,
24, 36, 48 h following initial tracer fluid injection and it is
then followed by taking samples at longer intervals. For examples
samples are taken at daily intervals. The samples are allowed to
settle and separate into water and oil layers. The water layer is
removed and placed in a small clear glass sample vial and its color
is visually compared against similar tubes of injection water
prepared with known concentrations of Uranine. In the art, it is
generally understood that very low concentrations of Uranine in
water can be visually estimated. Thus by visual comparison with
known standards the dye concentration in the water samples can be
estimated. By comparing relative concentrations of Uranine in the
samples obtained from various production wells, the relative
breakthrough times for various wells can be estimated and wells
with shorter breakthrough times can be identified. Then flow to
those wells can be restricted in order to allow equal distribution
of injected treatment fluid into the subterranean target site to
improve sweep efficiency and assist oil recovery.
Example 2
Prophetic
To Inoculate a Subterranean Site without Loss of Microbial
Inoculum
[0035] In this example, the injection and production wells of a
subterranean site are arranged in an inverted five spot pattern as
shown in FIG. 1. For the purposes of this example, it is assumed
that production well P2 has the shortest breakthrough time followed
by production well P4 with the second shortest breakthrough time. A
microbial inoculum suspension is prepared by making in a 6,000 L
tank a nutritional chemical fluid appropriate for the particular
microorganism used. A microbial inoculum is then added to the
nutritional chemical fluid to produce a suspension at the desired
concentration of microbes and nutrients.
The following steps are then taken: 1) Shut off the normal
injection water flow into injection well. 2) Inject the inoculum
suspension into the injection well at the normal injection rate for
the injection well (i.e., 1,250 L/h for 4.8 h) 3) After start of
injection of inoculum into the injection well, at various time
intervals shut in production well P-2. Production is shut in by
shutting off the producer pump for a period of time such as 2 out
of 3 hours, or by reducing the stroke frequency such as operating
at 20 cycles per minute rather than 60 cycles per minute. 4)
Complete injection of the inoculum suspension. 5) Open production
well P-2 flow valve after inoculum injection is complete. 6) Inject
water into the injection well at the standard injection rate (e.g.,
1,250 L/h for 24 h) to push the microbial inoculum to desired
depths of the subterranean target site. 7) After start of water
injection into the injection well, at various time intervals shut
in production well P-2. 8) After start of water injection into the
injection well, at various time intervals shut in producer well
P-4. 9) Complete injection of water into the injection well 10)
Open production wells P-2 and P-4 after injection of water into the
injection well is complete. 11) Inject for example 2,000 L of
nutritional chemical fluid at the standard flow rate (e.g., 1,250
L/h for 1.6 h) into the injection well 12) Inject water at standard
injection rate (e.g., 1,250 L/h for 24 h) into the injection well
to push nutritional chemical fluid to desired depths of reservoir.
13) After start of water injection into the injection well, at
various time intervals shut in production well P-2. 14) After start
of water injection into the injection well, at various time
intervals shut in production well P-4. 15) Upon completion of
injection into the injection well, shut off the injection flow to
the injection well. 16) Allow well treatment fluids a number of
days to contact the subterranean strata and perform their function.
17) Restart injection flow into the injection well at the standard
injection rates (e.g., 1,250 L/h for 24 h). 18) Restart production
at the production wells.
[0036] It should be noted that total well treatment period does not
exceed the breakthrough times between any well pairing.
* * * * *