U.S. patent application number 12/421462 was filed with the patent office on 2009-08-13 for purification of oil field production water for beneficial use.
This patent application is currently assigned to Produced Water Development, LLC. Invention is credited to David Rakestraw Stewart.
Application Number | 20090204419 12/421462 |
Document ID | / |
Family ID | 45445063 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090204419 |
Kind Code |
A1 |
Stewart; David Rakestraw |
August 13, 2009 |
Purification of Oil Field Production Water for Beneficial Use
Abstract
A method for generating new water with attached water rights
comprising identifying a source of production water and treating
the water in appropriate ways to provide water appropriate for
beneficial use such as agriculture, irrigation, industrial or
municipal or potable applications. Appropriate permits are obtained
to create the new water with attached water rights.
Inventors: |
Stewart; David Rakestraw;
(Fort Collins, CO) |
Correspondence
Address: |
HENSLEY KIM & HOLZER, LLC
1660 LINCOLN STREET, SUITE 3000
DENVER
CO
80264
US
|
Assignee: |
Produced Water Development,
LLC
Fort Collins
CO
|
Family ID: |
45445063 |
Appl. No.: |
12/421462 |
Filed: |
April 9, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11784569 |
Apr 6, 2007 |
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12421462 |
|
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60789846 |
Apr 6, 2006 |
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Current U.S.
Class: |
705/1.1 ;
210/652; 210/669; 210/718; 210/724; 210/806 |
Current CPC
Class: |
C02F 2101/322 20130101;
B01D 2311/16 20130101; B01D 61/58 20130101; B01D 61/16 20130101;
C02F 2209/11 20130101; C02F 1/001 20130101; C02F 2101/20 20130101;
C02F 1/441 20130101; C02F 1/74 20130101; B01D 2311/06 20130101;
C02F 1/283 20130101; C02F 1/42 20130101; C02F 1/20 20130101; C02F
1/444 20130101; C02F 1/5236 20130101; B01D 71/024 20130101; C02F
2101/32 20130101; B01D 2311/04 20130101; C02F 2209/06 20130101;
C02F 1/66 20130101; C02F 9/00 20130101; C02F 1/24 20130101; C02F
2101/325 20130101; B01D 61/025 20130101; B01D 61/147 20130101; C02F
1/40 20130101; B01D 2311/04 20130101; B01D 2311/18 20130101; B01D
2311/2642 20130101; B01D 2311/06 20130101; B01D 2311/2626 20130101;
B01D 2311/2623 20130101 |
Class at
Publication: |
705/1 ; 210/806;
210/718; 210/669; 210/652; 210/724 |
International
Class: |
G06Q 90/00 20060101
G06Q090/00; C02F 9/02 20060101 C02F009/02; C02F 1/28 20060101
C02F001/28; C02F 1/52 20060101 C02F001/52; C02F 1/42 20060101
C02F001/42; C02F 1/44 20060101 C02F001/44 |
Claims
1. A method for creating new rights for beneficial use of water,
said method comprising: identifying a production water source;
treating a liquid obtained from the production water source that
previously was not placed to any beneficial use and had no rights
associated with beneficial use; and obtaining a beneficial use
right in the production water based on an executed contract for end
user beneficial use.
2. A method according to claim 1, further comprising obtaining a
right from the mineral operator or working mineral interest owner
in the production water source.
3. A method according to claim 1, further comprising conducting a
geological investigation to determine the non-tributary or fossil
water status of the production water source.
4. A method according to claim 1, further comprising obtaining one
or more discharge permits for point source discharges to surface
water or shallow ground water.
5. A method according to claim 1, further comprising obtaining
approval from a regulatory authority.
6. A method according to claim 5, wherein the regulatory authority
is a state oil and gas commission.
7. A method according to claim 1, further comprising securing water
rights associated with the point source discharge to facilitate
beneficial use by augmentation or exchange.
8. A method according to claim 1, further comprising using the
production water directly for beneficial uses.
9. A method according to claim 1, wherein the liquid is treated
sufficiently to render the liquid potable.
10. A method according to claim 1, wherein the liquid is treated
using a filtration process.
11. The method of claim 10, wherein the filtration process
comprises ceramic microfiltration.
12. The method of claim 10, wherein the treatment further comprises
a process selected from the group consisting of: activated carbon
treatment; membrane separation by reverse osmosis; ion exchange
chromatography; or pH adjustment.
13. A method according to claim 10, wherein the liquid is subjected
to post-filtration treatment.
14. A method of generating new water with attached water rights,
the method comprising: obtaining a liquid mineral mixture from a
non-tributary source, the liquid having rights attached thereto and
owned by a first party; processing the liquid mineral mixture to
yield liquid waste product including at least a water component and
a hydrocarbon component; processing the liquid waste product to
separate at least portions of the hydrocarbon component to produce
a separated water component having a higher water quality grade
than the liquid waste product; obtaining evidence in a tangible
medium of a transfer of rights in the liquid waste product to a
second party; and obtaining evidence in a tangible medium of a
conversion of the rights in the liquid waste product to beneficial
use rights in the separated water component owned by the second
party and based on evidence in a tangible medium of assignment of
beneficial use interest in the separated water component to that
second party.
15. A method according to claim 14, further comprising: removing
volatile hydrocarbons, paraffins and asphaltines from the liquid
waste product to create pretreated production water; and subjecting
the pretreated production water to filtration using a ceramic
microfilter to produce the permeate water for beneficial use,
whereby the removal of the volatile hydrocarbons, paraffins and
asphaltines is effective to a sufficient extent to enable the
ceramic microfilter to operate continuously except for routine
cleaning and backwashing.
16. A method according to claim 15, wherein the removing of
volatile hydrocarbons, paraffins and asphaltines includes treating
the liquid waste product with a walnut shell filter.
17. A method according to claim 15, wherein the removing of
volatile hydrocarbons paraffins and asphaltines includes aerating
the liquid waste product to produce an aerated production water and
then treating the aerated production water with a walnut shell
filter.
18. A method according to claim 15, wherein the permeate water is
treated with activated charcoal.
19. A method according to claim 18, wherein the water passing
through the activated charcoal is further treated by a process
selected from the group consisting of reverse osmosis and ion
exchange.
20. A method according to claim 15, wherein the filtration with a
ceramic microfilter is conducted at a pressure of approximately 20
psi to 75 psi.
21. A method according to claim 15, wherein the filtration using a
ceramic microfilter is conducted using a filter constructed of a
material selected from the group consisting of titanium, alumina,
and zirconium having an average pore size of 5 microns to 10
microns.
22. A method according to claim 15, wherein the filtration using a
ceramic microfilter is conducted using a filter having an average
pore size of 0.05 microns to 1 micron.
23. A method according to claim 15, wherein the pH of the
production water is adjusted to remove iron by precipitation.
24. A method according to claim 14, wherein the liquid mineral
mixture is further processed to produce a separate mineral
component.
25. A method according to claim 14, wherein the non-tributary
nature of the water is determined by at least one member of the
group consisting of a state engineer and a Water Court.
26. A method of generating new water with attached beneficial use
rights, comprising: identifying a source of production water;
conducting a geological investigation for non-tributary water
determination; obtaining a permit allowing beneficial use of the
non-tributary production water; obtaining water user approval for
purchase or lease; securing water rights for a surface water source
including an augmentation plan and/or exchange using the
non-tributary production water; designing a production water
treatment plant to provide treated production water; obtaining
discharge permits for surface water discharge of the treated
production water; obtaining any approvals from an oil and gas
commission; constructing the production water treatment facility;
treating the production water using the production water treatment
facility; and obtaining a right in the treated production water
based on an executed contract or other assignment so that
beneficial use rights may be leased or sold.
27. The method of claim 26 wherein the processing of production
water comprises a step of microfiltration.
Description
[0001] This application claims priority pursuant to 35 U.S.C.
.sctn. 120 to and is a continuation application of U.S. patent
application Ser. No. 11/784,569 filed 6 Apr. 2007 (the '569
application), which claimed the benefit pursuant to 35 U.S.C.
.sctn. 119(e) of U.S. provisional patent application No. 60/789,846
filed 6 Apr. 2006 (the '846 application). The '569 and '846
applications are each hereby incorporated by reference in their
entirety as though fully set forth herein.
I. FIELD OF THE INVENTION
[0002] This invention relates to a system and method for simply and
economically producing agricultural augmentation water or potable
water from oil production water. In particular, the invention
relates to a system and process for microfiltration of production
water so that it can be used beneficially, rather than being
reinjected into the geological formation.
II. BACKGROUND OF THE INVENTION
[0003] Current water demands have prompted the investigation of
alternative water sources and ways to augment current water
supplies. It has been said that, "Nothing in the future will have a
greater impact on our ability to sustain our way of life and
preserve our environment for future generations than water." (The
Statewide Water Supply Initiative, Colorado Department of Natural
Resources.). These concerns transcend Colorado and the Western
United States and apply to the world resource outlook in
general.
[0004] One potential source of augmentation water is the water
included in hydrocarbons extracted from geological formations
containing oil and natural gas. The water included with the oil
and/or gas produced from the well is termed "produced water" or
"production water." Prior to this invention, production water had
not been considered a potential source of augmentation water.
Indeed, it was a difficult and expensive task just to make
production water suitable for disposal.
[0005] Typically production water is separated from the
hydrocarbons using an "API" oil water separator. The principle of
the API separator is to allow for the non-aqueous phase liquids
(primarily the organics which are lighter than water) to float to
the surface. Then the organics are removed from the production
water and concentrated through the use of a heat treatment unit,
which drives off the remaining water through evaporation.
[0006] The API separator will recover the majority of the oil, but
dissolved materials and volatile organics will remain in the
aqueous segment. Thus, production water usually contains high
concentrations of hydrocarbons and other inorganic constituents.
Typically production water is disposed of by being re-injected
under pressure back into the geologic formation, through a Class II
injection well, permitted by the US EPA. Because of the
contaminants in the production water, injection into other
geological formations that can be used for a drinking water source
or into surface water is usually prohibited. In addition,
re-injection is costly because it requires substantial pressure
(and, therefore energy) to overcome the resistance within the
geological formation. The Department of Energy estimates that 30 to
40 percent of the energy obtained from the formation as oil is used
to re-inject or move this water. (DOE--Sandia Conference, Salt Lake
City, January 2006.) In addition, re-injection of production water
into the formation dilutes subsequently-produced oil, adding
additional costs to the recovery and processing of those
hydrocarbons. Nevertheless, prior to the present invention,
re-injection was the most straightforward method to dispose of
production water, since it was quite difficult and costly to clean
the production water sufficiently for direct discharge. "Direct
discharge" is a term of art connoting discharge directly through a
pipe to the surface water course or stream.
[0007] Thus, an efficient and effective treatment for upgrading
production water would be beneficial both in providing high-quality
water that can be used in various water conservation schemes and in
avoiding the costs and other detriments of re-injecting the
production water under ground.
[0008] As used herein "production water" means water separated from
the production stream of oil and gas wells. An example of the
constituents in a sample of production water from Wellington,
Colo.--after API separation--is shown in Table 1
TABLE-US-00001 TABLE 1 Produced Water Quality Parameters After the
Oil/Water Separation Process Typical Range of Values mg/l
Inorganics Total Dissolved Solids (TDS) 1200 6000 Total Hardness as
CaCO3 30 300 Total Alkalinity as CaCO3 1000 4000 Chloride (Cl) 40
1000 Fluoride <1 10 Phosphate (PO4) <0.5 30 Nitrite + Nitrate
- Nitrogen <0.5 40 (NO2 + NO3 - N)* Metals Antimony (Sb)
<0.005 1.00 Arsenic (As)* <0.005 1.00 Barium (Ba)* 3.00 30.00
Berylium (Be) <0.0005 1.00 Boron (B) 1.00 10.00 Cadmium (Cd)
<0.001 1.00 Chromium (Cr) <0.02 1.00 Copper (Cu) <0.01
1.00 Iron (Fe)* 0.10 30.00 Lead (Pb) <0.005 5.00 Manganese (Mn)*
<0.005 10.00 Mercury (Hg) <0.0002 0.10 Nickel (Ni)* <0.05
10.00 Selenium (Se) <0.005 5.00 Silver (Ag) <0.01 5.00
Thallium (Tl)* <0.002 1.00 Zinc (Zn) <0.005 10.00 Organics
Oil and grease* 20.0 200.00 Benzene* 1.00 10.00 Toluene* 1.00 5.00
Ethylbenzene* 0.10 1.00 Xylenes, total* 1.00 5.00 n-Butylbenzene*
0.01 0.50 sec-Butylbenzene* 0.01 0.10 tert-Butylbenzene* 0.01 0.10
Isopropylbenzene* 0.01 0.10 4-Isopropyltoluene* 0.01 0.10
Naphthalene* 0.01 0.10 n-Propylbenzene* 0.01 0.10
1,2,4-Trimethylbenzene* 0.10 1.00 1,3,5-Trimethylbenzene* 0.10 1.00
Bromoform* <0.001 1.00
This production water also contains paraffins and asphaltenes in an
unmeasured, but not insignificant, amount.
[0009] Production water contains both inorganic and organic
constituents that limit the discharge options available to the
producer. Produced water contains a range of constituents including
dispersed oil, dissolved or soluble organics, produced solids,
scales (e.g., precipitated solids, gypsum (CaSO.sub.4), barite
(BaSO.sub.4)), bacteria, metals, low pH, sulfates, naturally
occurring radioactive materials (NORM), and chemicals added during
extraction (Veil, et al., 2004). The oil related compounds include
benzene, xylene, ethyl benzene, toluene, and other compounds of the
type identified in the sample analysis shown in Table 1 and in
other crude oil and natural gas sources. Normally, the production
water will also contain metals, e.g., arsenic, barium, iron, sodium
and other multivalent ions, which appear in many geological
formations.
[0010] In order to produce a higher grade of water, for example,
either "agricultural" or "augmentation" water, both the hydrocarbon
components and heavy metals need to be removed. As used herein,
"agricultural water" means water that will meet the basic standards
dictated by the EPA or state agency as the primary agency for water
quality in surface waters. "Potable water" means water that meets
the primary and secondary drinking water standards as defined by 40
CFR Sec.136.
[0011] As used herein "augmentation water" means water that can be
used to augment a water source, i.e., agricultural, industrial,
municipal, irrigation or potable water. In a more restrictive sense
it also means water that is supplied to keep a stream whole. In the
nomenclature used for water rights in the Western portion of the
United States "augmentation water" means water that protects
individuals or water users that have a prior appropriation for the
use of that water. A water augmentation plan is a procedure for
replacing water to a stream system whose flows are depleted by the
consumption of water, where the water user does not have a right to
the water consumed. Consumption or "consumptive use" means the
water has been placed in the evapo-transpiration cycle or otherwise
not returned to the stream system. According to current ground
water laws in the west with prior appropriation, if water under the
land would reach a stream system within approximately 100 years, it
is deemed to be "tributary" to that stream system; it supports the
stream's flow. Other users may have rights to the stream flow;
therefore, a new user cannot consume the water unless the new user
has a "water right" (decreed by a Water Court or by a State
Engineer) which allows their use of the water. Otherwise, a
downstream user with senior water rights could be damaged because
he might not have enough water for his purpose. So, absent a water
right, the new user must figure out a way to replace or "augment"
his water use so the existing stream flow remains the same as
before he used it. Augmentation may be made by purchasing water
rights on the affected stream system or by physically replacing the
water used from another legal water source. An augmentation plan is
submitted to the Water Court or State Engineer which governs the
particular drainage basin in which the affected stream system lies.
If the Court or State Engineer approves the plan, it will issue a
decree which grants the use of the "tributary" water, provided that
ongoing augmentation (replacement of used water) of that use occurs
per the plan that is used by junior appropriators to obtain water
supplies through terms and conditions approved by a water court
that protect senior water rights from the depletions caused by the
new diversions, under the Prior Appropriation Doctrine. Typically
this will involve storing junior water when in priority and
releasing that water when a call comes on; purchasing stored waters
from federal entities or others to release when a river call comes
on; or purchasing senior irrigation water rights and changing the
use of those rights to off-set the new user's injury to the stream.
These plans can be very complex and it is suggested that an
engineering consultant be retained to allow for proper
consideration of all hydrologic and water right factors.
[0012] Prior art methods of cleaning and upgrading production water
have been ineffective and/or overly expensive. These methods
include: [0013] Oil Water Separation (API method): The normal
method for oil water separation is the use of an API oil water
separator. The principal of the API separator is to allow for the
non-aqueous phase liquids ("NAPL's") to float to the surface. Then
the organics or NAPL's are removed from the production water and
concentrated through the use of a heat treatment unit. The oil
water separator will recover a majority of the oils, but any
dissolved materials in the remaining production water will not be
removed by the API unit. Thus, the method is useful in recovering
incremental amounts of oil from the production water, but is
ineffective in removing other contaminants from the production
water. [0014] Precipitation: Precipitation is used for the removal
of both dissolved oils and heavy metals. The precipitation will
react with the dissolved oil and then flocculate and precipitate
the oil into a particle. This particle can then be removed through
floatation and filtration, i.e., the coagulant entraps both the
metal and oil particles and makes them "bigger" so they can either
float or be filtered from the solution. In some instances, it has
been suggested to further clean the effluent from the precipitation
stage by reverse osmosis. However, precipitation and filtration is
still ineffective in removing volatile organic compounds, such as
benzene. Further, processing would be required to remove those
organic compounds. [0015] Adsorption: Activated carbon adsorption
has been used for many years as a method for the removal of
dissolved organics. Activated carbon will remove organics typically
below method detection limits listed in 40 CFR 136. However, this
technology is very expensive, and it does not normally remove heavy
metals. [0016] Nano Filtration: Nano filtration has been used for
the removal of sulfate ions in the field and has been shown to be
very effective. However, this would require microfiltration and
activated carbon for organic removal. [0017] Organo-thiol ligands:
The use of organo-thiol ligands has proved very promising in the
removal of specific toxic heavy metals and dissolved organics from
wastewater. However, they are very expensive and work on a limited
number of metal ions. [0018] SMZ Removal--Application of
"surfactant modified zeolites" is also a technique utilized on
produced waters for the removal of benzene, toluene, ethylbenzene,
and xylene, i.e., "BTEX," and other volatile organics. The
technique is most effective on benzene but is also effective on
other organics. This technology does not remove heavy metals,
unless they are associated with the organics being removed.
[0019] These prior art processes are all limited to certain aspects
of cleaning up production water and do not present a comprehensive
solution for upgrading production water to agricultural grade or
potable water. Methods that have attempted to achieve that result
comprise expensive multiple step processes that sequentially and
separately attempt to address each problem in cleaning up
production water. Thus, for example, one process of cleaning up
production water included separate steps for: warm softening;
coconut shell filtration; cooling (fin-fan); trickling filtration;
pressure filtration; ion-exchange; and reverse osmosis. (R. Funston
et al., "Evaluation of Technical and Economic Feasibility of
Treating Oilfield Produced Water to Create a `New` Water Resource,"
(Ground Water Production Council Conference, Produced Waters
Workshop, Colorado Springs, Colo., October 2002.)
[0020] Obviously, there is a need for a simple, economic process to
produce higher grade water such as agricultural and/or potable
water, from oil and gas production water.
[0021] Although the following description and example are focused
on production water from oil and gas wells, it is anticipated that
the invention may also have applicability to production water from
gas wells, and other similar water-containing hydrocarbon
materials, such as coal bed methane water, obtained from geological
formations.
III. SUMMARY OF THE INVENTION
[0022] The present invention provides both a method and system to
produce agricultural grade or potable water from oil and gas
production water. An important part of the process is the use of an
appropriate ceramic filter to facilitate separation of hydrocarbons
and other contaminants from the water. Appropriate pretreatment
steps are used to assist in the initial separation and to remove
materials from the process stream that would cause particular
problems in fouling the ceramic filter. The water that passes
through the ceramic filter may be subjected to additional
treatments to "finish" the water for the particular application
intended.
[0023] In one embodiment of the present invention production water
from an API oil/water separator is treated by aeration and the
aerated water is then subjected to filtering in a standard walnut
shell filtration unit. The pre-treated water is then subjected to
filtration with a ceramic filter to remove volatile organic
compounds, e.g., benzene that may remain and should be removed. Any
residual benzene in the permeate can be removed utilizing activated
carbon. Alternatively, the benzene may be removed using surface
modified zeolites of an appropriate mesh size, e.g., 14 to 100
mesh.
[0024] Purified water from the ceramic microfiltration step can
then be discharged to the land surface as "agricultural water" or
it can be sent to subsurface discharge. Because it has been
purified, it need not be injected into a subterranean oil and gas
formation normally at a depth of 4,000 to 5,000 feet.
[0025] Alternatively the discharge from the ceramic microfilter can
be further treated by activated carbon adsorption, reverse osmosis
and/or ion exchange treatment for further purification. Indeed,
water from the ceramic filtration--and with or without one or more
of these additional processes--may be deemed "potable."
IV. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The present invention may be more readily described by
reference to the accompanying drawings in which:
[0027] FIG. 1 is diagram of one embodiment of the production water
purification process of the present invention.
[0028] FIG. 2 is a diagram illustrating one embodiment of a
supplemental reverse osmosis purification procedure.
[0029] FIG. 3 is a diagram illustrating a typical engineering/legal
process for establishing design criteria for the beneficial water
to be derived from production water using the present
invention.
V. DETAILED DESCRIPTION OF THE INVENTION AND A PREFERRED
EMBODIMENT
[0030] One preferred embodiment of the present invention is
depicted in FIG. 1 (a process schematic) and the following
description.
[0031] Oil field production fluids 2 recovered from a well 1 are
subjected to a separation process in a "knockout" tank or "API"
separator unit 3 where water and oil separate under gravity
conditions. Typical API units include water separation systems such
as Envirex API Oil Water Separators available from US Filter
Corporation recently acquired by Siemens AG and now known as
"Siemens Water Technologies" headquartered in Warrendale, Pa. In
addition it is desirable to add a "reverse breaker" to the knockout
tank to assist in the removal and separation of emulsified oil.
Appropriate "reverse breaker" compositions include a metal
chloride, such as aluminum chloride, commercially available as
"Petrolite" available from Baker Hughes Petroleum, Inc. in Sugar
Land, Tex.
[0032] The oil overflow from the knockout tank is then processed
through a heater treater unit (not depicted in FIG. 1) to improve
the oil/water separation. The oil is stored in oil storage tanks
for eventual sale. Usually, the water driven off in this process is
vented to the air under permit from the EPA.
[0033] These initial steps, including the use of the "reverse
breaker," are conventional procedures employed in the industry in
removing water from the oil and gas recovered from the well.
Typically the water with remaining oil and other contaminants is
then reinjected into the geological formation. Instead, the present
invention can be used to treat this water so that it can be
employed beneficially as agricultural water, drinking water or in a
number of other uses, e.g., cooling water for power generation
plants and other processes.
[0034] In the present invention, the water underflow from the
knockout tank, i.e., the production water 4, then flows to an
aeration tank 5. The aeration process typically will have a large
tank, with a hydraulic detention time of at least 60 minutes, but
preferably 3 hours. This will utilize a fine bubble diffuser to
strip the well head gasses from the API unit. There is a gas/liquid
ratio that is determined in the laboratory for the best efficiency
to achieve the desired water quality. The equipment is custom made.
But the design of this equipment for this purpose is readily known
to one of ordinary skill in the art without undue experimentation.
Among other things, the aeration process is intended to remove
carbon dioxide and hydrogen sulfide. Aeration also drives off
volatile organic compounds ("VOCS") to the atmosphere, through a
stripping process. The VOCs removed include the BTEX compounds.
[0035] Theoretically, the aerated production water 6 could then be
subjected to microfiltration. However, in many applications, the
aerated production water still contains a number of
contaminants--especially organic compounds--that would rapidly
impair the operation of the ceramic filter and would necessitate
frequent cleaning with concomitant loss of production. Accordingly,
it is highly desirable to send the aerated production water to a
dissolved air flotation ("DAF") tank and/or organic filtration step
to remove organics and any floating oils that might have been
changed. This occurs because stripping of the VOCs, changes the
organic contents, which change the overall reaction to the
filters--i.e., the parafins are soluble with the VOCs present, but
when the VOCs are stripped, then the parafins come out of solution
due to the aeration step. These processes are intended to remove
any heavy fraction (e.g., paraffins and asphaltenes) to
non-detectable levels prior to ceramic microfiltration. If
detectable amounts of paraffins and asphaltenes are included in the
water treated by the ceramic microfilter, the ceramic microfilter
will soon become fouled to the point of rendering that process
inoperable. For example, in one test in which "walnut shell
filtration" was not employed, the ceramic microfiltration process
was rendered inoperable after only about four weeks of operation.
The removal of these heavy oil fractions allows the ceramic filter
to operate with acceptable run times (e.g., 2 to 3 days) between
cleanings. This compares to run times of 12 to 20 hours without
this pretreatment.
[0036] Accordingly, one preferred form of filtration is the use of
a "walnut shell filter 7," to process aerated production water 6.
The walnut shell filter appears to be particularly affective in
removing paraffins and asphaltenes. Suitable walnut shell filters
are manufactured by HydroFlow, Inc. of Maumee, Ohio or US Filter.
Walnut shell filters normally have an automatic backwash system
based on head-loss across the filter. A particularly suitable
filter is the HydroFlow 125 available from HydroFlow, Inc., Maumee,
Ohio.
[0037] The walnut shell filter may be preceded by the DAF process.
The DAF (dissolved air floatation unit) is sometimes used to remove
any dissolved air that has been injected and any oil that might
have come through the system. This also allows for any additional
sediment to settle out or float to the surface.
[0038] Also, it is possible to replace the DAF step by alternative
designs. For example, if a DAF is not used, then a transfer pump
can convey the water that passes through the walnut shell filter,
i.e., filtered production water, 8 to a pretreatment tank or
coagulant mix tank 9 where iron chloride coagulant can be added.
The pH can be adjusted by the addition of caustic (NaOH), as
required. In either case, the pretreated flow 10 from the mix tank
then passes to the concentration tank 11. The solution 12 from the
coagulation tank is subjected to crossflow ceramic microfiltration.
If the iron chloride coagulant is employed, its use may result in
the production of excess iron hydroxide solids, which would
necessitate periodic blowdown to a sludge storage tank for
subsequent dewatering via filter press. This step is necessary,
because the iron hydroxide sludge cannot be disposed underground
where it would fill void spaces and eventually clog the
formation.
[0039] Generally, the process of the present invention will include
either DAF or pretreatment and sludge filtration--but not both.
[0040] Waste from that DAF and the backwash water from the walnut
shell filter is then sent to a Class II injection well for
disposal. This backwash provides the cleaning of the filter. The
run times for the walnut shell filter are typically 20 to 24 hours
between backwashings.
[0041] The effluent 12 from the coagulation tank 11 is then
subjected to crossflow ceramic microfiltration ("CMF") 13. Suitable
membrane materials include titanium, alumina, and zirconium with a
pore size of 0.5 microns to 1.2 microns. The elemental membrane may
have an average pore size of 5 microns to 10 microns, although the
average pore size is preferably from 0.05 micron to 5 microns. Most
preferred is a method wherein the elemental membrane has an average
pore size from 0.05 micron to 0.1 micron. The membranes are
operated at pressures of 20 psi to 75 psi.
[0042] Suitable CMF filters include alumina membranes with zirconia
coatings 0.01 micron pore size, 37 bore, 3.8 mm diameter, 1200 mm
length available from ATECH Innovations, Gmbh, Gladbeck, Germany or
US Filter.
[0043] Pretreated water 12 from the concentration tank 11 is fed
into the feed port of the ceramic microfilter 13 modules where it
passes tangentially over the membranes. The clean, filtered water
permeates through the membranes and is collected in the shell of
the module and removed through the permeate port. This filtered
water is typically referred to as the "permeate" stream 14 and
contains no or very low levels of oil and heavy metals. The
solution that cannot permeate through the membrane flows down the
length of the membranes, out the reject port, and back into the
concentration tank. This stream is commonly referred to as the
"reject" or "concentrate" stream 15 and contains a suspension of
metal hydroxides and particulates. A small amount of the reject
stream is typically wasted to the solids bleed line and sent to the
oil sale tank in order to prevent the feed stream from becoming too
concentrated with solids.
[0044] The inherent mechanical strength of the ceramic membranes
allows for an on-line cleaning process, which is referred to as
backpulsing. Backpulsing is a procedure by which a small amount of
the permeate water is forced backwards through the membrane into
the feed stream. This displaces solids adsorbed onto the surface of
the membrane. Since the process pump continues to run during the
backpulse, any solids displaced from the membrane surface are swept
back into the concentration tank. Successful backpulsing depends on
a sharp, high-pressure pulse of the permeate water backwards
through the membrane. A separate "clean-in-place" ("CIP") unit is
provided for the periodic cleaning of the microfilters by serial
treatment with acidic solution, basic solution, an enzyme solution
and a rinse. Suitable materials include sulfuric acid, sodium
hydroxide, HOCl, and Ter-G-Zyme.TM. for routine cleanings. On
occasion it may be necessary to use a heavy duty degreasing
"syrup," i.e., BioSol.TM.--MEGASOL to remove organic foulant(s),
i.e., biological material(s) that are likely created in the
aeration tank or walnut shell filter. Biosolve can remove this
material and full recovery of the membranes is possible.
BioSol.TM.--MEGASOL is available from Evergreen Solutions, Inc.,
Calgary, Alberta, Canada.
[0045] The permeate stream 14 is monitored for pH level and
turbidity to ensure that the oil and heavy metals are removed and
the system is operating properly. A fluorescence meter is also used
to monitor for organics and microbiological activity in the system.
If any of the readings are improper (based on process
characteristics identified herein or the intended use of the
beneficial water), the permeate water is re-circulated to the
precipitation tank and an alarm occurs until the condition is
corrected. Bench mark readings for these process parameters, e.g.,
benzene, can be developed on site with laboratory verification for
discharge parameters. Therefore, typical settings for these
parameters will vary with each site and need to be field verified.
This monitoring is within the skill of the art.
[0046] Non-hazardous waste from the ceramic microfiltration process
is sent to a permitted land fill (not depicted on FIG. 1).
[0047] The process as described herein has focused on production
water, i.e., water typically separated from the fluids obtained
from wells producing oil and gas. This production water includes a
number of materials that can substantially foul the ceramic
microfilter and interfere with its economical operation. In other
applications, such as coal bed methane, the raw material does not
contain some of these contaminants, particularly the heavier oil
fractions such as paraffins and asphaltenes. In those
circumstances, the aqueous feedstock may only need to be aerated
before the aerated effluent is treated by ceramic microfiltration.
Treatment in the walnut shell filter or by DAF is not required. The
permeate from the CMF is then treated by reverse osmosis or
electrodialysis reversal ("EDR") to produce water having the
requisite qualities for the intended beneficial purpose.
[0048] Depending on the particular production water involved and
the beneficial use in which the water may be employed, the purified
effluent 14 from the ceramic microfiltration 13 may not require any
further processing. However, it is more likely that one or more
final clean-up stages may be useful to achieve the highest
beneficial use.
[0049] The highest beneficial use of this water is augmentation
water for water supplies. This can be done using the following
process 301 as depicted in FIG. 3: [0050] 1. Once the production
water source is identified, a geologic investigation can be
performed to determine the non-tributary status of the water. FIG.
3, steps 302 and 303. [0051] 2. If interest is obtained FIG. 3,
step 304, then the process can proceed to obtain permits for this
water including the well permit from the state engineer, the
discharge permit from the water quality control agency and the
permit to discharge this water from the oil and gas commission.
FIG. 3, step 304. [0052] 3. If the non-tributary status of this
water can be verified, then potential users of the purified water
can be identified. FIG. 3, step 305 [0053] 4. Once the permits for
discharge have been obtained, a facility can be designed and built
using the process features described above. FIG. 3, steps 307 to
310. [0054] 5. A perpetual water right FIG. 3, step 306 can then be
obtained from the state where the water is located to allow for the
beneficial use of this water. FIG. 3, step 311 By performing the
foregoing steps, it is possible to increase the value of the
purified water by at least 10 times its original value.
[0055] In particular, it is anticipated that the permeate 14 from
ceramic microfiltration 13 will be subjected to treatment with
activated carbon in the contactor 16 to remove additional volatile
organic compounds and to provide final filtration to produce
purified water 17 for beneficial use. As shown in FIG. 1, this
water is sent to storage reservoir 18 and may then be used for
augmentation or another beneficial purpose. Suitable absorption
units include pressure vessels (ASME vessels) available from US
Filter. The empty bed contact time is typically 20 to 30 minutes.
The mesh size is 20 to 40 mesh. The activated carbon base is
typically coconut shells, but will depend on the actual VOCs being
removed.
[0056] Other forms of post-filtration treatment can be employed
depending on the quality of that water and the intended use.
Additional post-treatment processes may be employed to further
treat the water prior to discharge. These include membrane
separation by reverse osmosis ("RO") and/or ion exchange ("IX").
The components that would be included in the RO process include
booster pumping, scale inhibition, pH adjustment (acid/base),
membrane separation and CIP using formulated cleaning agents.
Components required for ion exchange include the exchange columns
and regeneration using acid and base.
[0057] Acidic and basic wastes generated in the CIP of the CMS and
the IX regeneration can be neutralized in tanks and then recycled
through the full treatment process. Enzymes and detergents used in
CMS and RO CIP can be collected and diverted to storage for
eventual underground injection through a Class II injection. It
does not go back into the formation that hydrocarbons are extracted
from, but another formation. As described herein, this stream and
several other streams containing contaminants may be re-injected
back into the ground, but this is only a small portion of the
production water, and the re-injection of this water can be
accomplished at a fraction of the cost of re-injecting all of
production water back into the ground.
[0058] FIG. 2 provides an illustration of the beneficial use of the
purified production water. The production water, as mentioned in
FIG. 1, can be augmentation water. This water is placed into a
surface water or groundwater to augment the current water supply.
This water 202 can then be pumped from this shallow groundwater 201
and can be used for: (1) irrigation water 203 and/or (2) raw water
204 for a potable water treatment plant 205. If option (1) is
selected, then the water 203 is placed on crops for agricultural
purposes. If option (2) is selected, then the water 204 is placed
into a holding tank 206 for flow equalization. The next step is a
pre-filtration 207 to remove any particulates. Normally, a caterage
filter 207 will be utilized that has an effective removal of
particles in the size of 1.0 microns or greater. This will remove
any pathogens from the raw water. The next step is to treat the
water for removal of any salts. This is accomplished through a
reverse osmosis system. Normally anti-scalants will be added to
prevent clogging of the RO membrane 208. In addition, normally
about 10 percent of the flow bypasses 209 the RO membranes. The RO
System 210 will remove all salts, which will also remove the taste
of the water. Through the bypass 209, it is possible to keep some
of the salts for a TDS of approximately 300 mg/l. This will impart
a good taste to the finished potable water system 211. From this
location, a disinfectant 212 may be added to meet the USEPA
standards for potable water. Some of the water 213 is saved for
periodic cleaning of the membranes. Thus, FIG. 2 illustrates how
purified production water, initially provided as augmentation
water, can be put to better use.
VI. EXAMPLE
[0059] A treatment facility was constructed using water from an oil
well in the Wellington field of Colorado. The test employed a
typical API unit to provide a rough separation of liquid
hydrocarbons from the production water. The test employed the
following parameters:
[0060] a. The effluent from the API unit flowed into a 2500 bbl
aeration flow equalization tank.
[0061] b. From the aeration tank, the water flowed to a DAF system
sized for 250 gpm.
[0062] c. The water from the DAF flowed into the walnut shell
filter for the removal of asphaltines and parafins.
[0063] d. The next step is the chemical feed tank. The chemical
addition of ferric chloride was added to precipitate any heavy
metals and emulsified oils within the system. The feed rate for the
coagulation chemical ferric chloride varied between 80 to 120 mg/L.
The chemical addition tank had a hydraulic retention time of 20
minutes.
[0064] e. From the chemical addition tank, the oil production water
was pumped to the ceramic membrane having a pore size of 0.1
micron. The normal operating pressure of the CMF varied between 38
to 48 psi. This provided the physical separation of purified water
from the oil and other contaminants including heavy metals.
[0065] e. The permeate from the ceramic membrane was then
transferred to the activated carbon filtration system for final VOC
removal.
[0066] f. During this test, a back pulse system was employed to
allow for longer run times. This back pulse pushed the permeate
water backwards through the membrane to clean it. This was
performed approximately every 90 to 120 seconds. The backpulse
pressure is normally between 400 to 500 psi over a period of less
than 0.1 seconds. This creates a water hammer physically cleaning
the membranes and allowing for longer run times.
[0067] Results demonstrated improved filter runs with reduced
membrane fouling, and satisfactory reduction in VOC concentration,
as shown in Table 2.
TABLE-US-00002 TABLE 2 W3 Produced water effluent quality (Stewart
Environmental, 2004) Raw Water Treated Water Inorganics Total
Dissolved Solids (TDS) 2292 2370 Total Suspended Solids (TSS) 10
<5 Nitrite + Nitrate - Nitrogen <0.5 0.9 (NO.sub.2 + NO.sub.3
- N) Metals Antimony (Sb) <0.005 <0.005 Arsenic (As)
<0.005 <0.005 Barium (Ba) 9.26 0.063 Berylium (Be) <0.001
<0.00011 Boron (B) 2.76 2.42 Cadmium (Cd) <0.001 <0.001
Chromium (Cr) <0.02 <0.005 Copper (Cu) <0.01 <0.01 Iron
(Fe) 0.24 0.13 Lead (Pb) <0.005 <0.005 Manganese (Mn) 0.031
0.040 Mercury (Hg) <0.0002 <0.0002 Nickel (Ni) 0.04 <0.02
Selenium (Se) <0.005 <0.005 Silver (Ag) <0.01 <0.005
Thallium (Tl) <0.002 <0.002 Zinc (Zn) <0.005 0.052
Organics Oil and grease 42 <5 Benzene 2.45 <0.001 Toluene
1.78 <0.010 Ethylbenzene 0.428 <0.010 Xylenes, total 1.989
<0.010 n-Butylbenzene 0.043 <0.010 sec-Butylbenzene 0.022
<0.010 tert-Butylbenzene 0.037 <0.010 Isopropylbenzene 0.065
<0.010 4-Isopropyltoluene 0.033 <0.010 Naphthalene 0.134
<0.010 n-Propylbenzene 0.076 <0.010 1,2,4-Trimethylbenzene
0.372 <0.010 1,3,5-Trimethylbenzene 0.356 <0.010 Bromoform
0.480 <0.010 All results expressed in mg/L
[0068] The foregoing invention has been described with respect to
certain preferred embodiments for use with oil and gas production
water. It is anticipated that the general principles of the
invention may be embodied in other forms of operating systems
without departing from the spirit of the invention.
* * * * *