U.S. patent application number 11/705300 was filed with the patent office on 2007-08-23 for scale-inhibited water reduction in solutions and slurries.
Invention is credited to Robert L. Sloan, Harry D. JR. Smith, Kevin W. Smith.
Application Number | 20070193739 11/705300 |
Document ID | / |
Family ID | 38052349 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070193739 |
Kind Code |
A1 |
Smith; Kevin W. ; et
al. |
August 23, 2007 |
Scale-inhibited water reduction in solutions and slurries
Abstract
A cavitation device is used to reduce the water content of used
or wastep solutions and slurries, including oil well fluids and
muds, solution mining fluids, industrial oil/water emulsions, and
other used or wastep aqueous industrial fluids. A main reason for
reducing the water content of such fluids is to facilitate their
disposal or reuse. Thermal energy from the steam and vapor produced
by the non-scaling cavitation device is recycled in steam turbines
or piston expander engines, or otherwise facilitates evaporation
through a membrane or condensation to useful fresh water; the
efficiency of the process can be enhanced by mechanical vapor
recompression.
Inventors: |
Smith; Kevin W.; (Houston,
TX) ; Sloan; Robert L.; (Katy, TX) ; Smith;
Harry D. JR.; (Montgomery, TX) |
Correspondence
Address: |
William L. Krayer
1771 Helen Drive
Pittsburgh
PA
15216
US
|
Family ID: |
38052349 |
Appl. No.: |
11/705300 |
Filed: |
February 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11352889 |
Feb 13, 2006 |
7201225 |
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11705300 |
Feb 12, 2007 |
|
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60652549 |
Feb 14, 2005 |
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60652711 |
Feb 14, 2005 |
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Current U.S.
Class: |
166/250.01 |
Current CPC
Class: |
E21B 21/063
20130101 |
Class at
Publication: |
166/250.01 |
International
Class: |
E21B 47/00 20060101
E21B047/00 |
Claims
1-20. (canceled)
21. Method of evaporating water from a water-containing industrial
fluid comprising passing said fluid through a cavitation device to
increase its temperature, said cavitation device being driven by a
mechanical power source, and converting thermal energy from said
fluid having an elevated temperature to mechanical energy.
22. Method of claim 21 wherein said converting of thermal energy to
mechanical energy is performed in a steam turbine.
23. Method of claim 22 wherein mechanical energy from said steam
turbine is used to supplement the mechanical power source for said
cavitation device.
24. Method of claim 22 wherein mechanical energy from said steam
turbine is used to generate electricity.
25. Method of claim 24 wherein said electricity is used to power an
electric motor.
26. Method of claim 25 wherein said electric motor is used to
supplement the mechanical power source for said cavitation
device.
27. Method of claim 21 wherein said converting of thermal energy to
mechanical energy is performed in a steam cylinder engine.
28. Method of claim 22 wherein mechanical energy from said steam
cylinder engine is used to supplement the mechanical power source
for said cavitation device.
29. Method of claim 22 wherein mechanical energy from said steam
cylinder engine is used to generate electricity.
30. Method of claim 24 wherein said electricity is used to power an
electric motor.
31. Method of claim 25 wherein said electric motor is used to
supplement the mechanical power source for said cavitation
device.
32. Method of removing water from a water-containing industrial
fluid comprising passing fluid through a cavitation device to
increase its temperature, said cavitation device being driven by a
mechanical power source, passing said fluid at said increased
temperature to a flash tank to separate vapor and steam from said
fluid, passing said vapor and steam to a compressor and compressing
said vapor and steam to further elevate its temperature, condensing
said vapor and steam so compressed at its elevated temperature to
obtain distilled water, and optionally passing said distilled water
through a heat exchanger to conserve its heat energy
33. Method of claim 32 wherein said heat exchanger is used to heat
said water-containing industrial fluid before entering said
cavitation device.
34. Method of claim 32 including removing fluid remaining in said
flash tank from said flash tank and recycling it to said cavitation
device.
35. Method of claim 32 including using at least one component of
said fluid remaining in said flash tank as an ingredient in another
industrial fluid.
36. Method of evaporating water from an industrial fluid comprising
heating said fluid in a cavitation device and contacting the heated
fluid so obtained on the retentate side of a membrane capable of
passing water vapor.
37. Method of claim 36 wherein said membrane is a hydrophilic
membrane.
38. Method of claim 36 wherein said membrane is hydrophobic
membrane.
39. Method of claim 38 including recycling at least a portion of
said fluid into contact with said membrane.
40. Method of claim 38 wherein said heated fluid from said
cavitation device is passed to a flash tank and wherein vapors from
said flash tank are passed into contact with said retentate side of
said membrane.
Description
RELATED APPLICATION
[0001] This application claims the full benefit of copending
application Ser. No. 11/352,889, filed Feb. 13, 2006, which in turn
claims the benefit of provisional application 60/652,549 filed Feb.
14, 2005 and 60/652,711 filed Feb. 14, 2005.
TECHNICAL FIELD
[0002] A cavitation device is used to reduce the water content of
used or wastep solutions and slurries, including oil well fluids
and muds, solution mining fluids, industrial oil/water emulsions,
and other used or wastep aqueous industrial fluids. A main reason
for reducing the water content of such fluids is to facilitate
their disposal or reuse. Thermal energy from the steam and vapor
produced by the non-scaling cavitation device is recycled in steam
turbines or piston expander engines, or otherwise facilitates
evaporation or condensation to useful fresh water.
BACKGROUND OF THE INVENTION
[0003] In oil and other hydrocarbon production, drilling,
completion and workover, fluids are typically circulated down the
string of tubes and upwards around the outside of the tubes,
contacting the formation surface of the wellbore from which the
hydrocarbons are to be produced. In the case of a completion,
drilling, or workover fluids an original clear brine is typically
prescribed to have a density which is a function of the formation
pressure. Oil well fluids may include calcium, zinc, ammonium
and/or cesium as cations, and chloride, formate and particularly
bromide as anions from any source. Typical sources include cesium
chloride or formate, calcium chloride, sodium chloride, sodium
bromide, calcium bromide, zinc chloride, zinc bromide, ammonium
chloride, and mixtures thereof as well as their cation and anion
forming moieties from other sources. The salts and other additives
in the completion, drilling, or workover fluid may be partially
diluted by the formation water, as a result of contact with the
formation. The brines can also become diluted deliberately by the
well operator, who may add water to replace fluid lost into the
formation, or to reduce the density following a decision that it is
too high. Oil field fluids commonly include as ingredients not only
various salts but also polymers, corrosion inhibitors, densifying
agents such as barium compounds, biocides, solids such as mud
additives, and other compounds. Whether or not they are diluted,
the oil field operator is ultimately faced with the problem of
disposal or reuse. Frequently, finding a permissible site for
disposal of such solutions and slurries is difficult and very
expensive Disposal is also difficult for other common oil well
fluids such as water/oil (or oil/water) emulsions of widely varying
composition, including muds. A related point is that if the excess
water in dilute fluids is not eliminated or recovered for various
purposes, the volume of fluid at the wellsite continues to
increase. The cost of trucking to an approved disposal or
processing site can be prohibitive in many instances, and
accordingly a significant reduction in the volume of such materials
is needed in the art. All such fluids originating in the
hydrocarbon production industry--the oil and gas fields--may be
referred to herein collectively as "oil well fluids." All such
fluids for which our invention is useful, including oil well
fluids, may be referred to herein collectively as "industrial
fluids." They will all include at least some water which is to be
removed.
[0004] Conventional methods of dewatering such fluids, such as
distillation or simple evaporation, are very susceptible to scale
formation on the heat exchange surfaces, which soon renders the
distillation or evaporation equipment inoperable. Conventional
methods tend also to be energy inefficient, and do not lend
themselves to the use of thermal and electrical energy commonly
available at the well site.
[0005] Production of hydrocarbons from underground formations
generally includes water from the same formations. In 2007 the
ratio of water produced to oil produced worldwide is about 5
barrels of water for every barrel of oil produced. As oilfields
mature the produced water volumes typically increase. Unfortunately
the water produced with oil is not fresh water and is typically
highly contaminated with both dissolved salts and suspended solids
that include very hard to remove oil droplets. It typically comes
from much greater depths than the fresh water aquifers.
[0006] At the same time there is only a small amount of
chloride-free, fresh water in the world compared to the amount of
sea water. It has been logical and common practice to extract fresh
water from sea water or other "brackish" waters. One can simply
boil sea water and then condense the steam as fresh water. Today
desalination of sea water into fresh water is a commonly accepted
technology in wide use around the world. Units range from a few
gallons per day to 1,000,000's gallons per day. The technology for
desalination is evolving with several dominate technologies
generally defined as either evaporation or reverse osmosis and as
of 2007 the two technologies represent about 50% of the new plants
built; although, with the current rate of new membrane technology
development it is generally expected that the use of reverse
osmosis will grow relative to evaporation. Each has its advantages
and there are numerous methods defined in the literature to
describe both technologies in detail.
[0007] Like seawater, the water produced from hydrocarbon
extraction contains chlorides, and it seems logical that technology
from desalination could apply to such produced water. In some
produced water applications desalination technology does work and
is being used successfully. Unfortunately there are some key
differences between seawater and produced water. Seawater can be
considered a consistent feedstock; therefore, you can design for
the most efficient operation based on a number of choices and then
amortize the cost of the plant over a long life. You can control
the flow into the plant and assume the feedstock will never change.
Furthermore, generally size is not an issue and size can improve
efficiency particularly with heat exchangers, membranes etc.
[0008] Unfortunately, water obtained in hydrocarbon production is
not a consistent feedstock. It can vary even in the same field, and
composition can change over time. Harsh chemicals are often used in
the production of hydrocarbons and the well treatment chemicals
contaminate the associated produced water. Typically, produced
water contains significant dissolved and suspended organics.
Produced water is reactive and changes over time. The water in the
formation is in a reduced state; whereas, seawater is fully
oxidized and non reactive. Surface handling of produced water often
adds oxygen that oxidizes the components of the produced water.
Changes in temperature and pressure cause significant scale
deposition. Unlike a seawater desalination plant where you control
the flow into the plant, with produced water, you must cope with
the flow from the formation. Not only does the produced water
volume from a well typically increase with time, there are upsets
that change everything. An example of an upset might be where oil
overwhelms an oil/water separator and the oil intrudes into the
desalination process. Typically a desalination plant requires
pretreatment of the seawater feedstock. Given the variability of
the produced oilfield water it has been very difficult to design
the pretreatment system particularly for reverse osmosis
membranes.
[0009] To evaporate produced water there are some major issues. One
is economics. Generally most produced water is re-injected into the
same or similar formations. Downhole disposal is an environmentally
acceptable alternative to evaporation and it is one of the least
expensive alternatives; however, it often requires trucking or
piping that adds considerable cost. The other major problem is
scale. Scale is inversely soluble with heat. As temperature
increases the scaling salts are less soluble. Scale is detrimental
to an evaporation process that uses heat. The scale will form first
on hot surfaces and that includes heat exchanger surfaces. First
there is loss of efficiency. as the scale starts to insulate the
hot heat exchanger surface from the fluid. Scale buildup also plugs
the heat exchanger. Unfortunately, corrosion must also be
considered. Heat can speed the corrosion process and since most
produced waters contain chlorides, one must consider chloride
stress cracking of metals.
[0010] While evaporation in the oilfield is not as simple as
desalination, it can be accomplished with a careful process design
and it is a proven effective way to dispose of brine. Evaporation
is a key technology in numerous industries, including food,
chemicals and minerals processing. There are a wide variety of
processes and many variations. Different evaporation processes and
components were considered in developing this technology. Generally
the methods to design such systems are to work out the mass and
heat balances of the system and then each component. Components
generally include a flash tank where steam vapor separates from the
liquid, a source of heat, pumps to add fluid to the process and
remove fluid, crystallizers to remove dry solids, solids handling
equipment, heat exchangers, mixers, calandrias, evaporative cooling
towers, condensers, vacuum pumps, compressors, piping,
heat-transfer fluids, vents, packing trays, mist eliminators,
economizers, and combinations of all these components. Furthermore
the chemistry of the water must be considered as part of the design
process. Typically with seawater desalination there is a
pretreatment to remove hardness, or to mitigate its effect in the
process. Unfortunately oilfield waters typically contain an order
of magnitude greater concentration of hardness. Furthermore the
hardness can vary from a relatively benign calcium carbonate
compound to a nuisance calcium sulfate, but there is also hazardous
barium sulfate scale and even radioactive strontium sulfate
scaling. In designing a plant a chemical balance must be considered
along with the heat and mass balance. Oilfield water chemistry is
well defined in various reference books such as the classic
textbook by Dr. Charles Patten entitled "Oilfield Water Chemistry"
available through DA Campbell and Associates. There are many text
books on water chemistry, but Patten is different because it deals
with oilfield waters. There are graphs to predict scale formation
based on water analysis, pressures and temperatures that are proven
reliable and universal for oilfield waters. The scaling indexes
have since been refined and reduced to computer programs.
[0011] Many evaporation technologies and system layouts are well
known and have been practiced for at least 100 years, if not
longer.
[0012] For example, a simple system might be a source of heat and a
flash tank.
[0013] One could use any number of components to improve the design
and function of a flash tank. For example there is natural
circulation and forced circulation to consider. Fluid to be
evaporated can be pumped into the tank to turn it into a simple
continuous process. For example if you pump the same weight of
water into the evaporation tank to equal the pounds of steam vapor
being removed then you would have a continuous process. If you
consider the mass balance and heat balance you need to know that it
takes 1 BTU of heat to raise the temperature of one pound of water
one degree. Unfortunately it then takes 970.4 BTU per pound of
water to vaporize that water into steam. To evaporate water using
this method, you must add heat, generally know as sensible heat, to
raise the temperature of the base fluid from the starting point to
the boiling point. Then you must add the latent heat of
vaporization to run the evaporation. The mass and heat balance are
simple equations and for one pound of water evaporated, you need to
add the sensible heat to the latent heat and then you can decide
how much you want to process per hour and you will know how much
energy is required and then you can design your system around your
requirements using standard chemical engineering texts, vendor
input, handbooks, etc. It is typical to start with a proposed
Process and Instrumentation Diagram or P&ID and then work
though the mass balance and heat balance. In doing such work it
becomes obvious that this simple design is not efficient. If steam
is the ultimate goal, or if steam is required in another process
then this simple flash tank evaporator works, and one can continue
through the design to size the unit and then specify components to
build the system. These types of units are typically called steam
boilers. They are packaged readily available for purchase, lease or
rental in a multitude of sizes and configurations from a variety of
sources. Steam drove the industrial revolution and again the
technology is very well known and has evolved over time. A
conventional steam boiler is not an ideal evaporator of oilfield
waters because scale and corrosion rapidly foul the unit and can
even cause serious injury.
[0014] If you do not need the steam, then it becomes a cost. With
desalination, you need fresh water for civilizations to survive.
You can afford to pay for fresh water. Oilfield water is a cost
that you want to minimize since it offsets the revenue from the
hydrocarbons. It is not only a cost, but often an environmental
hazard. Using a conventional steam boiler is a very inefficient way
to evaporate oilfield waters. The first law of thermodynamics is
the conservation of energy. If you make steam, the energy in the
steam goes somewhere. If you evaporate produced oilfield waters,
the steam in the simple evaporation design goes to global warming.
That is both costly and not environmentally sound. If you take
advantage of the first law of thermodynamics and "recycle" the
steam into the evaporation process, you become far more efficient.
That is it takes less energy. For example you could run a simple
evaporation process but use the steam to further evaporation with a
simple evaporative cooling tower.
[0015] If you add a cooling tower to your process essentially you
can double the evaporation of the system. One could term this
multiple-effect evaporation. There are numerous multiple effect
evaporators and generally to be economical you need at least five
effects. Simply you must utilize the 2.sup.nd law of thermodynamics
which says heat moves from hot to cold. Steam at atmospheric
pressure cannot boil water at atmospheric. It can only provide
sensible heat--that is heat the water to the vaporization point. It
cannot boil the water because heat will not move between two bodies
that are the same temperature. As you compress steam it goes up in
temperature. With some compression you can get more heat in the
steam and then take advantage of the second law of thermodynamics.
With a multiple-effect arrangement generally the first evaporation
tank is at the highest pressure. High pressure steam goes to the
next flash tank that is operating at lower pressure and the heat
boils that liquid. That steam moves to the third, tank that is
lower pressure than the second tank and so on. Systems have been
built with 20 or 30 effects. It still takes 970 BTU/pound of water
evaporated, but by recycling the steam through multiple effects;
you can divide the 970 BTU/pound by the number of effects to get
the actual number of BTU's used for pound evaporated. For example,
if you have 5 effects essentially you can evaporate water 5 times
more efficiently or put another way use only 200 BTU per pound.
[0016] Another well known method to enhance evaporation is by using
compression. You can use one flash tank, but compress the steam and
use a heat exchanger to condense the steam into fresh water. The
fluid circulates from the flash tank through a heat exchanger where
you condense high pressure steam on the outside of the same heat
exchanger. By condensing the steam you get back the latent heat of
vaporization and fresh water as a by product. The steam must be
hotter than the evaporative fluid. By compressing the steam the
temperature goes up and heat moves from the hot to cold or from the
hot steam into the lower temperature (although still hot) fluid
being evaporated. Vapor compression can either be by
thermocompressor or by mechanical vapor recompression (MVR). A
thermocompressor simply mixes high pressure steam with low-pressure
steam to raise the temperature of the steam. The MVR system relies
on an engine driving compressor. MVR can be a very efficient
process. There are numerous references in the literature to the
efficiency of compression. Systems can equal 50-effect evaporators.
If you have high pressure steam, or another high pressure gas
thermocompression makes the most sense; otherwise, MVR would be the
choice.
[0017] All of the above systems use, and require, one thing in
common: heat exchangers that are prone to fouling in oilfield
environments. Heat exchangers by definition have a hot surface.
Again heat moves from hot to cold; therefore, heat moves from the
hottest fluid to the heat exchange surface (usually metal) and then
to the colder fluid. That means the heated surface is hotter than
the fluid and scale is inversely soluble with temperature. That
means scale starts to form on the heat transfer surface. As scale
forms heat transfer efficiency decreases. There are numerous
designs to minimize scale build up on heat transfer surfaces. There
are mechanical devices to even scrape the surfaces to prevent scale
buildup. A crystallizer is simply a heat exchanger designed to
handle very high solids, and is often used in the situations were
scale can be a problem. There are a multitude of heat exchanger
designs and patented systems to improve heat transfer and to
prevent scale buildup. Chemicals can also be used to treat for
scale and are often utilized in the oilfield since scale even
builds up downhole; however, chemicals add to the cost of systems
and an important goal is to minimize costs.
[0018] One method to evaporate produced water is to remove the
scale-forming chemicals first and then further process the water
with the steam into a crystallizer or conventional MVR system. If
you remove the hardness, any of the conventional evaporation
systems will work. It is common practice to precipitate scale with
chemicals or by other means. One method is to seed liquid as you
heat it to precipitate the scale in the "fluid" instead of on the
heat transfer surfaces. You can also keep the fluid below the
scaling index by selecting systems that run at lower temperatures,
or by using vacuum, among other methods. Seeding compounds and
techniques are selected according to the composition of the
concentrate and the type of scale likely to deposit under the
circumstances.
[0019] The present method avoids the use of conventional heat
exchangers in the dirty fluids to a great extent, recycles thermal
energy wherever feasible, and promotes scale-free evaporation to
obtain useful fresh water without undue energy use. As will be seen
below, a cavitation device, or SPR, is a versatile device for
converting shaft horsepower into heat without using a conventional
heat exchange surface. The SPR can be used in various heat and
energy saving systems to realize cost savings in many ways while
making copious amounts of useful fresh water and concentrating
otherwise used wastep fluids so they can be economically reused or
disposed of.
SUMMARY OF THE INVENTION
[0020] This invention dewaters dilute and contaminated solutions
and slurries--industrial fluids--by passing them through a
cavitation device which generates shock waves to heat the fluid and
facilitate the removal of moisture, thereby reducing the volume of
wastep material for disposal. Preferably the cavitation device is
one manufactured and sold by Hydro Dynamics, Inc., of Rome, Ga.,
most preferably the device described in U.S. Pat. Nos. 5,385,298,
5,957,122 6,627,784 and particularly 5,188,090, all of which are
incorporated herein by reference in their entireties. In recent
years, Hydro Dynamics, Inc. has adopted the trademark "Shockwave
Power Reactor" for its cavitation devices, and we use the term SPR
herein to describe the products of this company and other
cavitation devices that can be used in our invention. The
cavitation device will heat the fluid without accumulating any
scale. The reason is that the generation of thermal energy takes
place within the fluid and not on a heat exchange surface.
[0021] Definition: We use the term "cavitation device," or "SPR,"
to mean and include any device which will impart thermal energy to
flowing liquid by causing bubbles or pockets of partial vacuum to
form within the liquid it processes, the bubbles or pockets of
partial vacuum being quickly imploded and filled by the flowing
liquid. The bubbles or pockets of partial vacuum have also been
described as areas within the liquid which have reached the vapor
pressure of the liquid. The turbulence and/or impact, which may be
called a shock wave, caused by the implosion imparts thermal energy
to the liquid, which, in the case of water, may readily reach
boiling temperatures. The bubbles or pockets of partial vacuum are
typically created by flowing the liquid through narrow passages
which present side depressions, cavities, pockets, apertures, or
dead-end holes to the flowing liquid; hence the term "cavitation
effect" is frequently applied, and devices known as "cavitation
pumps" or "cavitation regenerators" are included in our definition.
Steam generated in the cavitation device can be separated from the
remaining, now concentrated, water and/or other liquid which
frequently will include significant quantities of solids small
enough to pass through the reactor.
[0022] The term "cavitation device" includes not only all the
devices described in the above itemized U.S. Pat. Nos. 5,385,298,
5,957,122 6,627,784 and 5,188,090 but also any of the devices
described by Sajewski in U.S. Pat. Nos. 5,183,513, 5,184,576, and
5,239,948, Wyszomirski in U.S. Pat. No. 3,198,191, Selivanov in
U.S. Pat. No. 6,016,798, Thoma in U.S. Pat. Nos. 7,089,886,
6,976,486, 6,959,669, 6,910,448, and 6,823,820, Crosta et al in
U.S. Pat. No. 6,595,759, Giebeler et al in U.S. Pat. Nos. 5,931,153
and 6,164,274, Huffman in U.S. Pat. No. 5,419,306, Archibald et al
in U.S. Pat. No. 6,596,178 and other similar devices which employ a
shearing effect between two close surfaces, at least one of which
is moving, such as a rotor, and/or at least one of which has
cavities of various designs in its surface as explained above.
[0023] The solution or slurry is increased in temperature in the
SPR and then passed to a next step either for utilizing the heat
energy of the fluid or to enhance the efficiency of its
vaporization. The vapor or steam associated with the heated fluid
can be used, for example, to operate a steam turbine or steam
engine, or it can be subjected to recompression to make its heat
energy readily available for reuse, or it can be passed through a
membrane to enhance the efficiency of vaporization, or simply
passed to a cooling tower.
[0024] The fluid heated by the SPR, or a portion of it, can be
immediately recycled to the SPR to heat it further. Vapor or steam
generated in the SPR can be separated to be passed to one of the
above-mentioned steps, before, after, or at the same time as the
remaining fluid.
[0025] Our invention includes the optional step of filtering the
fluid before it enters the SPR, or after it is concentrated by the
SPR. Because the SPR is able to handle large proportions of solids
in the fluid it processes, our invention enables the postponement
of filtration until after the fluid is reduced in water content by
passing through the SPR to heat it and facilitate removal of vapor;
filters and the filtration process can therefore be engineered to
handle smaller volumes of liquid with higher concentrations of
solids.
[0026] In another aspect, our invention includes a method of
processing a used oil well fluid comprising optionally filtering
the used oil well fluid, passing the used oil well fluid through a
heat exchanger utilizing wastep heat from a power source such as
the exhaust of a Diesel engine, powering a cavitation device with
the power source, passing the oil well fluid through the cavitation
device to increase the temperature thereof, optionally recycling at
least some of the used oil well fluid through the cavitation device
to further increase the temperature of the used oil well fluid,
passing the used oil well fluid into a flash tank to separate steam
and vapor from the used oil well fluid and to obtain a concentrated
fluid, removing at least a portion of the concentrated fluid from
the flash tank, and reusing the at least a portion of the
concentrated fluid in an oil well. The use of a Diesel engine is
not essential; the cavitation device may be powered by any more or
less equivalent source of mechanical energy, such as a common
internal combustion engine, a steam engine, an electric motor, or
the like. Wastep heat from any of these, either in an exhaust gas
or otherwise, may be utilized in a known manner to warm the oil
well fluid before or after passing it through the SPR.
[0027] While the SPR is quite capable of elevating the temperature
of an aqueous solution or slurry to the boiling point of water (at
atmospheric pressure) or higher, it is not essential in our process
for it to do so, as the flash tank, membrane, or other vapor
recovery device may be operated under a vacuum to draw off vapors
at temperatures below the boiling point at atmospheric
pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIGS. 1a and 1b show variations of a cavitation device as
utilized in our invention.
[0029] FIGS. 2A-2D are flow sheets illustrating our process made
more efficient by utilizing steam from the heated fluid to operate
a steam turbine or a steam engine for assisting in operating the
SPR.
[0030] FIG. 3 shows a recompression loop in which steam or vapor
originating in the SPR is recompressed to conserve energy.
[0031] In FIGS. 4a and 4b, a membrane distillation step is combined
with our SPR system; two different configurations are shown.
DETAILED DESCRIPTION OF THE INVENTION
[0032] FIGS. 1a and 1b show two slightly different variations, and
views, of the cavitation devices sometimes known as a cavitation
pump, or a cavitation regenerator, and sometimes referred to herein
as an SPR, which we use in our invention to regenerate solutions
comprising heavy brine components.
[0033] FIGS. 1a and 1b are taken from FIGS. 1 and 2 of Griggs U.S.
Pat. No. 5,188,090, which is incorporated herein by reference along
with related U.S. Pat. Nos. 5,385,298, 5,957,122, and 6,627,784. As
explained in the 5,188,090 patent and elsewhere in the referenced
patents, liquid is heated in the device without the use of a heat
transfer surface, thus avoiding the usual scaling problems common
to boilers and distillation apparatus.
[0034] A housing 10 in FIGS. 1a and 1b encloses cylindrical rotor
11 leaving only a small clearance 12 around its curved surface and
clearance 13 at the ends. The rotor 11 is mounted on a shaft 14
turned by motor 15. Cavities 17 are drilled or otherwise cut into
the surface of rotor 11. As explained in the Griggs patents, other
irregularities, such as shallow lips around the cavities 17, may be
placed on the surface of the rotor 11. Some of the cavities 17 may
be drilled at an angle other than perpendicular to the surface of
rotor 11--for example, at a 15 degree angle. Liquid (fluid)--in the
case of the present invention, a solution containing heavy brine
components, or a used mud emulsion, or a used workover fluid, or
other industrial fluid which may or may not contain solid
particulates,--is introduced through port 16 under pressure and
enters clearances 13 and 12. As the fluid passes from port 16 to
clearance 13 to clearance 12 and out exit 18 while the rotor 11 is
turning, areas of vacuum are generated and heat is generated within
the fluid from its own turbulence, expansion and compression (shock
waves). As explained at column 2 lines 61 et seq in the 5,188,090
patent, "(T)he depth, diameter and orientation of (the cavities)
may be adjusted in dimension to optimize efficiency and
effectiveness of (the cavitation device) for heating various
fluids, and to optimize operation, efficiency, and effectiveness .
. . with respect to particular fluid temperatures, pressures and
flow rates, as they relate to rotational speed of (the rotor 11)."
Smaller or larger clearances may be provided (col. 3, lines 9-14).
Also the interior surface of the housing 10 may be smooth with no
irregularities or may be serrated, feature holes or bores or other
irregularities as desired to increase efficiency and effectiveness
for particular fluids, flow rates and rotational speeds of the
rotor 11. (col. 3, lines 23-29) Rotational velocity may be on the
order of 5000 rpm (col 4 line 13). The diameter of the exhaust
ports 18 may be varied also depending on the fluid treated.
Pressure at entrance port 16 may be 75 psi, for example, and the
temperature at exit port 18 may be 300.degree. F. Thus the heavy
brine components containing solution may be flashed or otherwise
treated in the cavitation device to remove excess water as steam or
water vapor. Note that the position of exit port 18 is somewhat
different in FIGS. 1a and 1b; likewise the position of entrance
port 16 differs in the two versions and may also be varied to
achieve different effects in the flow pattern within the SPR.
[0035] Another variation which can lend versatility to the SPR is
to design the opposing surfaces of housing 10 and rotor 11 to be
somewhat conical, and to provide a means for adjusting the position
of the rotor within the housing so as to increase or decrease the
width of the clearance 12. This can allow for different sizes of
solids present in the fluid, to reduce the shearing effect if
desired (by increasing the width of clearance 12), to vary the
velocity of the rotor as a function of the fluid's viscosity, or
for any other reason.
[0036] Operation of the SPR (cavitation device) is as follows. A
shearing stress is created in the solution as it passes into the
narrow clearance 12 between the rotor 11 and the housing 10. This
shearing stress causes an increase in temperature. The solution
quickly encounters the cavities 17 in the rotor 11, and tends to
fill the cavities, but the centrifugal force of the rotation tends
to throw the liquid back out of the cavity, which creates a vacuum.
The vacuum in the cavities 17 draws liquid back into them, and
accordingly "shock waves" are formed as the cavities are constantly
filled, emptied and filled again. Small bubbles, some of them
microscopic, are formed and imploded. All of this stress on the
liquid generates heat which increases the temperature of the liquid
dramatically. The design of the SPR ensures that, since the bubble
collapse and most of the other stress takes place in the cavities,
little or no erosion of the working surfaces of the rotor 11 takes
place, and virtually all of the heat generated remains within the
liquid.
[0037] Temperatures within the cavitation device--of the rotor 11,
the housing 10, and the fluid within the clearance spaces 12
between the rotor and the housing--remain substantially constant
after the process is begun and while the feed rate and other
variables are maintained at the desired values. There is no outside
heat source; it is the mechanical energy of the spinning rotor--to
some extent friction, as well as the above described cavitation
effect--that is converted to heat taken up by the solution and soon
removed along with the solution when it is passes through exit 18.
The rotor and housing 10, particularly in its interior 20, indeed
tend to be lower in temperature than the liquid in clearances 12
and 13. There is little danger of scale formation even with high
concentrations of heavy brine components in the solution being
processed.
[0038] Any solids present in the solution, having dimensions small
enough to pass through the clearances 12 and 13 may pass through
the SPR unchanged. This may be taken into account when using the
reconstituted solution in for oil well purposes. On the other hand,
subjecting the water-soluble polymers to the localized cavitation
process and heating may break them down, shear them, or otherwise
completely destroy them, a favorable outcome for many purposes. The
condition known as "fish-eyes," sometimes caused by the gelling of
water-soluble polymers, can be cured by the SPR. These effects will
take place in spite of the possible presence of significant amounts
of solids.
[0039] Concentrated and heavy or dense brines are more liable to
crystallize in use than dilute brines, and accordingly their
crystallization temperatures are of concern. The crystallization
point of a highly salt-laden solution does not imply merely that a
small portion of the salts may crystallize out, but that the entire
solution will tend to gel or actually solidify, a phenomenon of
great concern during the transportation of such solutions or in
storage, for example. The ability to concentrate heavy brine
components and their ratios to each other in a solution using a
cavitation device leads to better control over crystallization
temperature and the ability to achieve a good balance between
crystallization temperature and density. Complex relationships
between the concentrations and ratios of heavy brine component ions
and other constituents in the solution rather precisely obtained by
our invention means that the crystallization temperature of a
completion or workover fluid can be more readily controlled while
conserving substantially all of the components available to be
saved.
[0040] The ability to concentrate heavy brine components content in
a solution using a cavitation device also leads to better control
over solution density. Relationships between the rather precisely
obtained concentrations of heavy brine component ions and other
constituents in the solution means that the density of a completion
or workover fluid can be more readily matched with the density of
the drilling fluid.
[0041] Where the fluid treated is a heavy brine containing cesium,
it will commonly contain at least 2.5% cesium by weight. Our
invention includes a method of treating a hydrocarbon producing
formation comprising introducing into the formation through a well
an oil well fluid containing at least 2.5% by weight cesium,
whereby the fluid becomes diluted so that it contains less than
2.5% cesium by weight, circulating the fluid from the well, and
passing at least a portion of the fluid through a cavitation device
to remove moisture therefrom and produce a regenerated fluid
containing at least 2.5% cesium by weight in the fluid.
[0042] Similar percentages may be found in cesium solutions used in
mining cesium, and our invention may be quite useful for
concentrating cesium solutions in cesium mining.
[0043] In FIGS. 2A-D, a dilute solution, slurry or emulsion
(hereafter sometimes a fluid) enters in line 32 from the lower
left, as depicted. It may come directly from a well, from a hold
tank, or indirectly from another industrial fluid source. The SPR
(cavitation device) 30 requires a motor or engine to rotate it.
Here, a Diesel engine or other power source, designated Mech. Power
40, powers the SPR through shaft 41 and generates hot exhaust gases
or other wastep heat, which is/are passed to heat exchanger 42,
where the thermal energy of the exhaust gas or other wastep heat is
used to heat the incoming fluid in line 32 through a heat exchange
surface or other conventional or expedient manner. Optionally the
heat exchanger may be bypassed in a line not shown. The incoming
fluid continues through line 31 to the SPR 30 which may be any
cavitation device described above; for illustrative purposes, it
may be substantially as shown in FIGS. 1a and 1b. A supplemental
pump, not shown, may assist the passage of the fluid. In the SPR
30, the fluid is heated as described with reference to FIGS. 1a and
1b, and the heated fluid is passed through line 33 to a flash tank
44, where steam and vapor is separated and removed in line 34.
Alternatively or supplementally, steam or vapor may be vented
through a separate vent, not shown, from the SPR to the atmosphere
or drawn off directly from or in a similar vent associated with
exit port 18 (FIGS. 1a and 1b). The steam may be recycled in a
known manner for thermal energy preservation, for condensing to
make substantially pure water, put to other useful purposes, or
simply flashed to the atmosphere. Optionally a vacuum may be drawn
on the flash tank to assist in removing the vapor and steam. It is
not essential that the temperature of the fluid exiting from the
SPR exceed the boiling point of water, as a vacuum assist can
facilitate the withdrawal of vapors. Concentrated fluid from the
flash tank, in line 35, can be recycled to the well, or analyzed
on-line or after removal in order to determine the best way to
re-establish the ratios of ingredients, a desired crystallization
temperature, a desired density, or other property; it can also be
recycled to line 32 to join with the input to the SPR to become
further concentrated and for further water removal. In FIGS. 2A-2D,
the concentrated fluid in line 35 is shown passing through heat
exchanger 42 where it will contribute its excess thermal energy to
the elevation of the temperature of the incoming fluid in line 32.
For this purpose, line 35 may have its own heat exchanger separate
from one such as depicted deriving its thermal energy from
mechanical power source 40.
[0044] FIGS. 2A and 2B show the steam or vapor in line 34 going to
a steam turbine 36, where the thermal energy is used to rotate the
turbine, generating mechanical rotational power for supplementing
the mechanical power source 40 in the operation of the SPR, through
shaft 45. In FIG. 2B, the turbine 36 is connected to an electrical
generator 37 which generates power sent through wire 49 to electric
motor 39 for rotating shaft 45. Fluid discharged from the turbine
36 in line 38 is condensed by passing through turbine 36 and may be
used as a source of fresh water.
[0045] FIG. 2C is similar to FIG. 2A except that a steam cylinder
engine 43, such as a Spilling engine, is substituted for the steam
turbine 36 in FIG. 2A. Steam and vapor from line 34 is sent to the
steam engine 43, which turns shaft 45 for supplementing the
mechanical power input of power source 40. In FIG. 2D, the steam
engine 43 is coupled to an electric generator 46, generating
electricity sent through wire 49 to motor 39 for rotating shaft 45.
The steam and vapor entering steam cylinder engine 43 of FIGS. 2C
and 2D is condensed while its thermal energy is converted to
mechanical energy, and the condensate may be collected in a
discharge line not shown for any convenient use as fresh water.
[0046] Supplemental pumps, and various filters, meters and valves,
not shown, may be deployed throughout the system of FIGS. 2A-D, as
in any of the other system configurations described herein to
assure the desired flow rates and pressures, and to direct the
fluids in the system to and through the various options described;
automatic or manual controls for the valves pumps and other
components may also be installed. Likewise, the system may utilize
various electric and mechanical power and thermal energy sources
available on site to drive pumps and/or assure the evaporation of
water from the incoming fluid in line 32. It should be understood
that any electric power generated by the system will result in
savings in commercial power otherwise available at the site.
[0047] Referring now to FIG. 3, the SPR is shown in use with
mechanical vapor recompression. An incoming solution or slurry is
passed through line 80 to heat exchanger 81 where it picks up heat
from the condensate in line 82, then passes through line 84 to heat
exchanger 85 to absorb heat from hot concentrated liquid or slurry
in line 86 from flash tank 87, and on through line 88 to the SPR
89. SPR 89 receives rotational power from mechanical power source
62 through shaft 68. The SPR 89 further heats the incoming slurry
or solution and forwards the heated fluid through line 50,
optionally through a devolatilizer 51 and further through line 52
to flash tank 87. The SPR may have a vent not shown for venting
vapor or steam to the atmosphere or for carrying the vapor or steam
to any device in the system that could use the heat or steam power
therefrom. In flash tank 87, steam or vapor is removed through line
56 and sent to compressor 57, which compresses it, at the same time
elevating its temperature because of the increased pressure.
Compressor 57 receives rotational mechanical power from power
source 62 through shaft 69 or from a different power source not
shown, for example an electrical motor which in turn may be powered
by a steam turbine using steam from the system (see FIGS. 2A-2D).
Because the SPR heats the fluid without employing a solid heat
exchange surface, it is virtually scale free; therefore the
relatively high temperatures of the fluid in line 56 are achieved
in a relatively scale-free manner. On the other hand, because the
SPR is able to handle not only highly concentrated brines and other
oilfield fluids containing solids as well as dissolved solids, the
liquid accumulating in flash tank 87 may contain significant
amounts of both dissolved and undissolved solids. The concentrated
fluid can be removed through line 86 and filtered if desired.
Condensation in condenser 83 of the high-temperature compressed
steam from compressor 57 provides a condensed fluid in line 82
having considerable thermal energy for heating the incoming fluid
in incoming line 80 through heat exchanger 81. Additional
mechanical vapor recompression loops can be installed as is known
in the art of mechanical vapor recompression. Some of the steam or
vapor in line 56 may optionally be diverted through line 65 to heat
exchanger 66 designed to capture wastep heat from power source 62,
such as from exhaust gases or a thermal jacket, not shown in
detail; this diverted steam or vapor can be isolated in line 70 for
use as an optional steam or vapor, or, after it gives up its heat
elsewhere, as condensate that can be used separately as a source of
fresh water or combined with the distilled water in line 59. Note
also that concentrate from line 86 or line 71 is desirably recycled
to the SPR in lines 63 or 64, or both, to further elevate its
temperature and/or remove additional water from it and/or further
concentrate the fluid in lines 86 and 71.
[0048] FIGS. 4a and 4b are flow diagrams showing the use of
membranes to enhance evaporation of water in an SPR system. In FIG.
4a, an industrial or oilfield fluid enters the SPR 96 in line 108,
is heated in the SPR as described above and continues in line 108.
After passing through an optional heat exchanger 97, the fluid
output from the SPR 96 in line 90 goes directly to the retentate
side 98 of a membrane 94 selected for its ability to permit heated
water to pass, leaving salts and solids behind. FIG. 4a is adapted
from U.S. Pat. No. 6,656,361, which is expressly incorporated
herein by reference in its entirety. The membrane in FIG. 4a is
hydrophilic, which permits liquid water to pass through its pores.
The fluid introduced from line 90 continues to flow while it
contacts the surface of membrane 94. It may be recirculated in line
91, showing the now concentrated fluid leaving the membrane housing
95 and reentering it after passing through an optional heat
exchanger 99 to increase its temperature, and joining line 90. Heat
exchanger 99 and other heat exchangers shown herein may utilize
wastep heat from any of numerous sources normally available in an
industrial setting and especially in an oilfield site. On the
permeate side 100 of the membrane 94, a slightly negative pressure
may be drawn, leading vapor and/or aqueous droplets into space 92,
where the cooler conditions bring about condensation of vapor to
fresh liquid water. The condensate is removed in line 101 for use
in an associated system such as for makeup of a new oilfield fluid,
or it may be simply collected for use as fresh water. As disclosed
in U.S. Pat. No. 6,656,361, an air blower may assist in moving and
condensing the vapor in space 92. Additional or optional cooling
devices or circulating coolant 103 may be employed on the permeate
side of the membrane also to assist in the condensation process.
The fluid passing through the membrane housing 95, now containing
less water in line 91 may be further recycled through line 102 and
optionally through another heat exchanger 104 to further increase
its temperature, to the SPR 96 for additional heating before being
returned to the membrane. A continuous or intermittent blowdown may
be conducted, for example through line 107 to maintain desired
concentrations of constituents in the circulating fluid; this may
be accomplished by monitoring and controlling the conductivity of
the fluid in line 102, for example.
[0049] In the configuration of FIG. 4b, a hydrophobic membrane is
used to enhance the evaporation of water from the fluid heated in
the SPR 110. The oilfield or other industrial fluid from input line
121 is heated in the SPR 110 and goes through line 111 to flash
tank 112 where it is separated more or less like the fluid in flash
tank 44 of FIGS. 2A-D--that is, part of it remains in the flash
tank as liquid, including undissolved solids or not, and part of it
is given off as vapor or steam. The vapor or steam is directed
(possibly with the aid of a slight negative pressure) to the
retentate side 114 of the membrane 113. Water vapor passes from the
retentate side 114 of the membrane 113 into the air gap 115 defined
by wall 116 more or less parallel to membrane 113. Wall 116 is
cooler than the heated fluid on the retentate side 114, and
accordingly the vapor tends to condense in air gap 115, resulting
in a fresh water condensate which is removed in line 117 for use as
fresh water in any of numerous possible applications. The retentate
may be recycled in line 118 to the retentate side 114 of the
membrane, or in line 119 to the SPR for reheating. A concentrate
stream is removed from the flash tank 112 continuously or
intermittently in line 120 either for use as a source of its
components or for disposal. If it is to be discarded, a
considerable advantage of the process, as with all the methods
disclosed herein, is that it will include far less volume to be
transported or stored. In either case, the fluid in line 120 may be
passed through a heat exchanger not shown to conserve its heat
energy for other purposes, for example to preheat the incoming
fluid in line 121. Because the SPR 110 is able to generate
relatively high temperatures in the original fluid without using a
scale-forming surface, the system is essentially scale-free. As in
FIGS. 2 and 3, various valves, filters, meters, monitors, controls,
heat exchangers and the like may be deployed through out the
systems of FIGS. 4a and 4b as desired or as may be indicated by the
circumstances. In almost all oilfield areas, wastep heat sources
are available and can be adapted to heat exchangers of various
kinds as are known in the art; the heat energy can be used as
illustrated in FIGS. 2A-D to elevate temperatures of fluids, or for
conversion to electrical or mechanical power which also can be used
wherever desirable in the system. Heat exchangers using wastep heat
from any source may be of particular use on the incoming fluids in
line 108 of FIGS. 4a and 121 of FIG. 4b, but of course may be
applied wherever heat will be beneficial. Generally, hydrophobic
membranes are preferred, as by definition they permit only water
vapor, and not water droplets, to pass. If water droplets pass
through the membrane, they may carry dissolved salts with them,
which is counterproductive. However, we do not intend to disclaim
the use of hydrophilic membranes, particularly as their properties
may be improved in the future to reject dissolved salts more
completely. It is a notable advantage of the SPR that it is able to
heat the dirty or salts-laden water without significant scale
formation, while retaining scale-forming salts in the concentrate,
and the vapor or steam that is delivered to the membrane, whether
the membrane is hydrophobic or hydrophilic, presents little danger
of fouling. Both types of membranes are well known in the art of
desalination, medical applications, and for other purposes. Any
membranes which will perform as described with respect to FIGS. 4a
and 4b are contemplated in our invention.
* * * * *