U.S. patent application number 10/985344 was filed with the patent office on 2006-03-16 for method and apparatus for generating pollution free electrical energy from hydrocarbons.
Invention is credited to Steven A. Sarada.
Application Number | 20060054318 10/985344 |
Document ID | / |
Family ID | 30443304 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060054318 |
Kind Code |
A1 |
Sarada; Steven A. |
March 16, 2006 |
Method and apparatus for generating pollution free electrical
energy from hydrocarbons
Abstract
The present invention relates to the generation of substantially
pollution free energy by utilizing hydrocarbons to create
electrical energy, while reinjecting exhaust fumes or other
byproducts into a subterranean formation. Thus, remote, low reserve
oil and gas fields may be exploited and produced without requiring
the construction of expensive gas transmission lines.
Inventors: |
Sarada; Steven A.;
(Englewood, CO) |
Correspondence
Address: |
SHERIDAN ROSS PC
1560 BROADWAY
SUITE 1200
DENVER
CO
80202
US
|
Family ID: |
30443304 |
Appl. No.: |
10/985344 |
Filed: |
November 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10199430 |
Jul 18, 2002 |
6820689 |
|
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10985344 |
Nov 9, 2004 |
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Current U.S.
Class: |
166/266 |
Current CPC
Class: |
E21B 41/0057
20130101 |
Class at
Publication: |
166/266 |
International
Class: |
E21B 43/40 20060101
E21B043/40 |
Claims
1. A method for generating substantially pollution free electrical
power from a hydrocarbon wellbore for use in a local electrical
transmission grid, comprising: a) producing a hydrocarbon fluid
from at least one wellbore from a subterranean formation to a
surface location; b) separating non-combustible constituents from
said hydrocarbon fluids at said surface location, wherein water is
substantially removed from said hydrocarbon fluids; c) generating
electrical energy from said hydrocarbon fluids at said surface
location or proximate thereto; d) transforming said electrical
energy from a first voltage to a second voltage which is compatible
with a local electrical transmission line; e) transmitting said
electrical energy into said local electrical transmission line
which is located between an offsite electrical power generating
facility and an end user; and f) injecting a waste byproduct
exhaust gas from said generating electrical energy substantially
onsite into at least one of said subterranean formation or a
secondary subterranean formation.
2. The method of claim 1, further comprising metering said
hydrocarbon fluids prior to generating electrical energy.
3. The method of claim 1, wherein producing a hydrocarbon fluid
comprises commingling produced hydrocarbon fluids from a plurality
of producing wells.
4. The method of claim 1, wherein the pressure in said subterranean
formation is increased by injecting said waste byproduct exhaust
gas into the subterranean formation.
5. The method of claim 4, further comprising compressing said waste
byproduct exhaust gas from a low pressure to a high pressure prior
to injecting said waste byproduct exhaust gas into the subterranean
formation.
6. The method of claim 5, further comprising utilizing exhaust gas
obtained compressing the waste byproduct exhaust gas to generate
steam.
7. The method of claim 1, further comprising separating water and
other liquid phase byproducts from said waste byproduct exhaust gas
prior to injecting the waste byproduct gas into a subterranean
formation.
8. The method of claim 1, wherein transmitting said electrical
energy further comprises interconnecting a conductive electrical
line between a generator to said local electrical transmission
grid.
9. The method of claim 1, wherein said hydrocarbon fluids comprise
at least one of an oil, a condensate and a natural gas.
10. The method of claim 1, wherein said hydrocarbon wellbore is
used for both the production of said hydrocarbons and the injection
of a waste byproduct gas.
11. The method of claim 10, wherein the waste byproduct gas is
injected between a substantially continuous string of tubing and
casing, and the hydrocarbons are produced from the substantially
continuous string of tubing.
12. A method for generating substantially pollution free electrical
energy for local distribution and use from a remote location,
comprising: a) providing a wellbore which extends from a surface
location to a subterranean formation which contains hydrocarbons;
b) producing the hydrocarbons from the subterranean formation to
the surface location; c) separating non-combustible constituents
from said hydrocarbons at said surface location; d) operating an
engine at least partially with said hydrocarbons to generate
electrical energy and create a first waste exhaust gas; e)
transmitting said electrical energy into an electrical transmission
line which is located between an electrical power generating
facility and an end user; f) metering said electrical energy to
provide an accounting of the electrical energy transmitted; g)
scrubbing said waste exhaust gas to substantially remove
non-volatile constituents from said waste exhaust gas; h)
compressing said waste exhaust gas to increase a pressure of said
waste exhaust gas; I) capturing a second waste exhaust gas from
compressing the waste exhaust gas; and j) injecting at least one of
said first waste exhaust gas and said second exhaust gas into the
subterranean formation or a secondary formation, wherein
substantially no waste exhaust gas from said operating an engine
and compressing said waste exhaust gas is discharged into the
atmosphere.
13. The method of claim 12, wherein said wellbore which produces
said hydrocarbons is further utilized for the injection of at least
one of said first waste exhaust gas and said second exhaust
gas.
14. The method of claim 12, further comprising the step of
injecting said water separated from said hydrocarbons into a
subterranean formation.
15. The method of claim 12, further comprising the step of storing
said waste exhaust gas in a storage vessel prior to injecting said
waste exhaust gas.
16. The method of claim 12, wherein providing a wellbore comprises
drilling a well into the subterranean formation and running at
least one string of production piping to facilitate the extraction
of said hydrocarbons.
17. The method of claim 12, wherein providing a wellbore comprises
utilizing a pre-existing wellbore which penetrates the subterranean
formation.
18. The method of claim 12, wherein separating non-combustible
constituents comprises flowing the hydrocarbons and the
non-combustible constituents through at least one vessel which
utilizes in part a gravitational force to separate the hydrocarbons
and the non-combustible constituents.
19. The method of claim 12, wherein transmitting the electrical
energy further comprises providing a transformer to selectively
alter the amount of voltage associated with the electrical
energy.
20. A method for exploiting a hydrocarbon reservoir in a remote
location without producing exhaust gas byproducts to the atmosphere
and providing electrical power to a local electrical transmission
grid, comprising: a) providing a wellbore which extends from a
surface location to a hydrocarbon reservoir positioned below the
earth's surface; b) producing a hydrocarbon fluid from said
hydrocarbon reservoir to said surface location; c) removing any
non-combustible components from said hydrocarbon fluid at the
surface location; d) utilizing said hydrocarbon fluid to generate
electrical energy at the remote location; e) transforming said
electrical energy from a first voltage to a second voltage which is
compatible with said local electrical transmission line. f)
transmitting said electrical energy into the local electrical
transmission line which is located between an electrical power
generating facility and an end user; and g) injecting a waste
exhaust gas created from generating said electrical energy into
said hydrocarbon reservoir or a secondary subterranean formation,
wherein substantially no waste exhaust gas is emitted into the
atmosphere.
21. The method of claim 1, further comprising gathering
substantially all waste byproduct exhaust gases prior to injecting
the waste exhaust gas, wherein the remote facility emits
substantially no hydrocarbon exhaust into the atmosphere.
22. The method of claim 1, further comprising metering said
electrical energy prior to transmitting the electrical energy,
wherein an accounting of the electrical energy transmitted may be
determined.
23. The method of claim 1, further comprising metering said waste
exhaust gas prior to injecting into at least one of said
hydrocarbon reservoir and said secondary subterranean
formation.
24. An apparatus for producing substantially pollution free
electrical energy from a subterranean formation at a substantially
remote location between an electrical end user and an electrical
power generating plant, comprising: at least one wellbore extending
from a surface location to a subterranean formation, said at least
one wellbore comprising an upper end and a lower end; at least one
production separator in operable communication with said upper end
of said at least one wellbore, said production separator having at
least one internal baffle to separate a combustible hydrocarbon
fluid from a non-combustible fluid; a storage vessel in operable
communication with said at least one production separator for
storing said non-combustible fluid; an electrical generator in
operable communication with said at least one production separator
and located at said substantially remote location, said electrical
generator capable of converting said combustible hydrocarbon fluid
into electrical energy; a gas collection vessel in operable
communication with said electrical generator, wherein exhaust gas
from said electrical generator is collected in said gas collection
vessel; a transformer in operable communication with said
electrical generator, said transformer transforming at least one of
a first voltage, a first phase and a first amperage of said
electrical energy to a second voltage, a second phase and a second
amperage; a compressor in operable communication with said gas
collection vessel, wherein the exhaust gas is compressed from a
first pressure to a second pressure prior to injection into a
subterranean formation; and an electrical transmission line for
transmitting the electrical energy from the substantially remote
location to the end user.
25. The apparatus of claim 24, wherein said collection vessel is a
pipe.
26. The apparatus of claim 24, further comprising a pump for
injecting the non-combustible fluid from said storage vessel into a
subterranean formation.
27. The apparatus of claim 24, wherein the hydrocarbon fluid
comprises at least one of an oil, a condensate, a natural gas or
combinations therein.
28. The apparatus of claim 24, further comprising at least one
meter for determining a volume of at least one of the combustible
hydrocarbon fluid, the non-combustible hydrocarbon fluid and the
electrical energy.
29. The apparatus of claim 24, further comprising a second storage
vessel for storing the combustible hydrocarbon fluid.
30. The apparatus of claim 24, wherein said electrical generator
comprises an internal combustion engine which drives a shaft
coupled to a plurality of magnets to create an electrical current.
Description
[0001] This application claims priority to and is a
Continuation-in-Part application of pending prior application Ser.
No. 10/199,430, filed Jul. 18, 2002 and is incorporated in its
entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to electrical power
generation, and more specifically substantially pollution free
power generation obtained from naturally occurring hydrocarbons
with the reinjection of waste byproducts into subterranean
formations.
BACKGROUND OF THE INVENTION
[0003] As a result of worldwide industrialization in the 19th and
20th centuries and the discovery of the internal combustion engine,
an ever increasing demand for hydrocarbon fuel exists throughout
the world. More specifically, "hydrocarbons" as discussed herein
include all carbon based combustible fuels such as coal, petroleum
products such as oil and tar, and natural gas, and any organic
compound of hydrogen and carbon which occurs naturally in gaseous,
liquid or solid form and is generated through either biogenic or
thermogenic means. Although extremely beneficial as a fuel source,
these hydrocarbon energy sources emit toxic fumes and carbon
containing compounds in their exhaust when burned, and are thus
believed to be a major contributor to global warming, air pollution
and other undesirable conditions known to cause harm to human
health and the environment.
[0004] Although recent improvements to power generating exhaust
systems including catalytic converters, exhaust scrubbers and other
similar products have improved the efficiency and reduced emissions
of power plants which rely on hydrocarbon fuel sources, there is
still a significant problem with regard to how these toxic
emissions from hydrocarbon fuels can be significantly reduced or
eliminated.
[0005] In conjunction with the aforementioned problem of toxic and
carbon containing gas emissions, an additional problem exists in
producing and transporting hydrocarbon fuels from remote locations
to existing electrical power plants located near high population
densities. More specifically, significant numbers of hydrocarbons
reservoirs, and more specifically natural gas fields are discovered
in remote locations which are often hundreds of miles from a major
city or power plant. Since the discovered reserves are not
sufficient to justify the economic expense of a gas transmission
pipeline, many of these smaller hydrocarbon reservoirs are never
exploited, thus preventing the production of valuable energy
resources from remote locations.
[0006] Thus, a significant need exists for an apparatus and method
for exploiting hydrocarbon reservoirs in remote locations to
provide cost effective; and substantially pollution free energy to
local communities and municipalities.
SUMMARY OF THE INVENTION
[0007] It is thus one aspect of the present invention to provide a
cost effective, economical apparatus and method to exploit and
produce combustible products from hydrocarbon reservoirs and
generate electrical energy in remote and isolated locations. Thus,
in one embodiment of the present invention, produced natural gas
from a subterranean formation is utilized to power an electrical
generator which produces electrical energy for transmission through
local power lines and grid systems.
[0008] It is a further aspect of the present invention to provide a
method and apparatus for generating substantially pollution free
energy from hydrocarbon reservoirs which contain oil and natural
gas. Thus, in one embodiment of the present invention the exhaust
byproducts from an engine used to drive an electrical generator is
contained, scrubbed to remove water and other impurities, and
reinjected into a subterranean formation to eliminate emissions of
toxic and carbon containing exhaust gases to the atmosphere.
[0009] It is a further aspect of the present invention to provide
an apparatus and method for improving in a cost effective manner
the productivity of an existing hydrocarbon reservoir, which at the
same time substantially eliminating toxic gases and exhaust
byproducts from entering the atmosphere. Thus, in one aspect of the
present invention the exhaust gases created during electrical
generation are collected, compressed and reinjected into the
producing hydrocarbon reservoir. The injection of the exhaust gases
thus increases the reservoir pressure and enhances the production
rate and ultimate recovery from the hydrocarbon reservoir.
[0010] Thus, in one embodiment of the present invention a method
for creating substantially pollution free energy is provided,
comprising the steps of: [0011] a) producing hydrocarbon fluids
from a subterranean formation; [0012] b) separating non-combustible
constituents from said hydrocarbon fluids; [0013] c) generating
electrical energy from said hydrocarbon fluids; [0014] d)
transmitting said electrical energy into a local electrical
transmission line; and [0015] e) injecting a waste byproduct gas
from said generating electrical energy step into at least one of
said subterranean formation or a secondary subterranean
formation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a flow schematic identifying one embodiment of the
present invention and depicting a producing wellbore, process
equipment, an injection wellbore and electrical power transmission
lines;
[0017] FIG. 2 is a front elevation view identifying a producing
hydrocarbon wellbore and the various components associated
therewith;
[0018] FIG. 3 is a flow schematic of process equipment utilized
downstream from a producing wellbore in one embodiment of the
present invention;
[0019] FIG. 4 is a flow schematic of additional process equipment
related processing produced hydrocarbon and exhaust gases in one
embodiment of the present invention;
[0020] FIG. 5 is a front elevation view of an injection wellbore in
one embodiment of the present invention and depicting the injection
of waste gas into a subterranean formation; and
[0021] FIG. 6 is a front elevation view of a combined production
and injection wellbore which depicts the production of hydrocarbon
fluids from production tubing and the reinjection of exhaust gas
into a second non-producing subterranean formation through the
annulus defined by the production tubing and production casing.
DETAILED DESCRIPTION
[0022] Referring now to the drawings, FIG. 1 depicts a flow
schematic of one embodiment of the present invention and which
identifies the flow path of a hydrocarbon fluid and the creation of
electrical energy associated therewith. More specifically, the flow
schematic depicts a producing geologic formation 2 which generally
comprises a porous and permeable subterranean formation which is
capable of storing, a hydrocarbon fluid such as oil, natural gas,
condensate, or other combustible hydrocarbons (hereinafter
"hydrocarbon fluid"). The natural gas may be comprised of methane,
ethane, butane, propane, as well as liquid condensate associated
therein. As well known in the oil and gas industry, these
hydrocarbon fluids may be produced through a producing wellbore 6
either naturally due to a high bottom hole pressure in the
producing geologic formation, or by means of artificial lift using
pumps, down-hole motors, sucker-rods, and other available means
well known in the art to extract the hydrocarbons from the geologic
formation to a surface location.
[0023] Upon production of the hydrocarbon fluids through the
producing wellbore 6 the hydrocarbon fluids generally flow through
a wellhead 44, which typically has a plurality of valves 38 and
pressure gauges 40. The valves 38 or "choke bodies" generally
restrict and regulate the pressure and flow rate of the hydrocarbon
fluids. After flowing downstream from the wellhead 44, the
hydrocarbon fluids generally enter a phase separator 10 which is
used to separate the condensate liquid and gas components of the
hydrocarbon fluid stream from any water which may be present in the
fluid. The water is generally removed to an oil/water storage
vessel 42, where it is transported via a truck to a secondary
location and/or the water is treated and reinjected into a
subterranean geologic formation.
[0024] Once the substantially water free hydrocarbon fluids exit
the phase separator 10, the hydrocarbon fluids typically flows
through a metering device 12 to identify the volume of dry gas or
liquid condensates being produced. After discharge from the meter,
the hydrocarbon fluids are used to run a reciprocating or turbine
engine 16, which in turn drives an electrical generator 16 to
produce electrical energy in the form of an electrical current.
[0025] As identified in FIG. 1, the electrical energy generated
from the electric generator 16 may be transformed with an electric
transformer 18 to modify the amount of voltage being introduced
into the electric transmission grid 20. This electric transmission
grid 20 is preferably an electrical power line which is located in
close proximity to the producing wellbore, and thus reduces the
significant costs involved with installing a gas utility pipeline
for transmission of the natural gas to an electrical generating
plant at a distant location, this process is generally known in the
art as distributive power generation.
[0026] As further depicted in FIG. 1, the exhaust gas 50 generated
from the engine 6 flows into an exhaust gas collection and
treatment/cooling vessel 22 which is further used to treat the
exhaust gas 50 and remove any water content and/or vapor associated
therewith. The engine 16 is generally an internal combustion engine
(IC), a combustion turbine engine (CT) or a reciprocating
combustion engine (RC), which are well known by those skilled in
the art. The water is removed to a secondary water storage vessel
42 where it is either reinjected into a subterranean formation or
transported via a truck to a secondary location for treatment. The
exhaust gas 50 produced from the turbine or reciprocating engine is
now substantially cooler and dryer and is piped to an exhaust gas
compressor 26 which increases the pressure of the exhaust gas from
a low of between about 0-50 psi to a high of 10,000 and 30,000 psi
between about psi, the discharge pressure being determined by the
pressure of the subterranean geologic formation used for injection
purposes. At rates from 10 active to over 10,000 active.
[0027] More specifically, the exhaust gas is compressed in the gas
compressor 26 to a pressure which is sufficient to allow the
exhaust gas 50 to be injected down an injection wellbore 8 (and
overcoming the friction pressure loss in the pipe) and into a
subterranean formation with a lower pressure.
[0028] Thus, the exhaust gas is metered for volume and constituent
and then injected through an injection wellbore 8 which is in
operable communication with either a porous and permeable
non-producing geologic formation 4, or the producing geologic
formation 2 itself. In summary, FIG. 1 depicts an apparatus and
process which utilizes produced hydrocarbon products to create
electrical energy for transmission through an electrical grid
system, and which reinjects any exhaust gas or other pollutants
into either a secondary subterranean formation or the producing
geologic formation to substantially eliminate any pollution created
from the producing hydrocarbon.
[0029] Referring now to FIG. 2, a front elevation view of a
producing wellbore used in one embodiment of the present invention
is provided herein. More specifically, FIG. 2 depicts a producing
geologic formation 2 which is typically a porous and permeable
sandstone or other rock formation capable of storing significant
volumes of hydrocarbon fluids. Upon penetration of the geologic
formation 2 by a producing wellbore 6, the producing wellbore is
stabilized by running surface and production wellbore casing 34 to
prevent earth materials from collapsing into the producing wellbore
6. To enhance production, the producing geologic formation may be
"fractured" with high pressure fluids and supported with sand or
other proppant materials to improve the relative permeability of
the hydrocarbon reservoir and enhance production. Wellbore tubing
36 is subsequently lowered into the wellbore casing 34, and which
provides a flow pathway for the hydrocarbon products produced from
the producing geologic formation 2. The wellbore tubing 36 is
generally isolated from the wellbore casing 34 by means of a packer
58, which provides a seal to isolate the producing formation and
fluids from the annulus and casing positioned above the packer
58.
[0030] To allow flow from the producing geologic formation 2 into
the production casing 34 and production tubing 36, perforations 48
are provided which are generally a plurality of apertures
positioned in the casing to provide communication from the
producing geologic formation 2 and the wellbore production tubing
36. In a typical hydrocarbon fluid production operation, the bottom
hole pressure of the producing geologic formation 2 is generally
greater than the surface pressure, and the hydrocarbon fluids flow
from the producing geologic formation 2 to the surface wellhead 44
which is otherwise known in the art as a "Christmas tree".
Preferably, a valve 38 is used to control the producing wellbore
and thus regulate the flow rate and surface pressure. Numerous
types of "chokes" and other valves are additionally well known in
the art and can be made from a variety of different materials and
designs. Upon flowing through the valve 38, the hydrocarbon fluids
flow towards the process separator as shown in FIG. 3, and which
may include oil, natural gas, and water.
[0031] Referring now to FIG. 3, an equipment battery depicting one
embodiment of the present invention is provided herein, and which
identifies the various process equipment generally required to
scrub i.e., clean the hydrocarbon produced liquids, create
electrical energy, and transmit the electrical energy through an
existing electrical transmission grid. More specifically, produced
hydrocarbon fluids enter a phase separator 10 which is generally
either two phase such as a "gun barrel" or three phase depending on
the particular design. A two phase separator typically separates
gas from liquids with a plurality of vanes or baffles, while a
three phase separator separates gas from liquid and additionally
the water component from the hydrocarbon fluids in the liquid
phase. In either embodiment, the liquid phase i.e. typically water,
is removed from one portion of the phase separator 10 by means of
the baffles and gravity, while the dry natural gas flows downstream
through a meter 12. As previously stated, the water from the phase
separator 10 is either trucked to a secondary location, or
reinjected into a subterranean formation.
[0032] Once the natural gas flows through the gas meter 12, the
hydrocarbon fluids flows into a combustion engine 14 which creates
sufficient horsepower to drive an electrical generator 16. The
combustion turbine engines may be similar to aircraft turbofan
engines, or heavy framed models with massive casings and rotors.
Either type generally have a multi-fuel capability, and can be
operated with natural gas or high quality hydrocarbon liquid
distillates (dual fuel). Reciprocating combustion engines 14 have
numerous designs, and can again run on different types of
hydrocarbon fluids. Although, reciprocating engines are generally
more efficient than turbine engines, they generally generate higher
levels of toxic emissions and noise and require greater
maintenance.
[0033] The electrical generator 16 creates electrical current from
a rotating shaft driven from the combustion turbine or
reciprocating combustion engine 15, which is transformed into
electrical power at a rate ranging from a low of 20 kw to a high of
over 1000 kw. Electric power created by the generator is
transmitted to a transformer 18 which converts the current to an
output suitable for an electric line, generally 3 phase 480 volt.
Transforming equipment used to transform electrical energy from a
first voltage to a second voltage which is compatible with a local
electrical transmission line can include, but is not limited to
rectifiers, inverters, transformers, main breakers, automatic
transfer switch/switchgear, paralleling and synchronizing relays,
and an interfacing transformer as appreciated by one skilled in the
art. The electrical current is subsequently transmitted through an
electrical transmission grid 20 which is typically located in close
proximity to a small town or other community which utilizes the
electrical current for household needs such as light and power
generation, etc.
[0034] Both combustion turbine engines and reciprocating combustion
engines utilize produced mechanical energy in the form of a
rotating shaft to drive an electric generator in power rating sizes
generally ranging from 20 to 500 kW although large heavy-farmed
turbines can drive generators in excess of 1000 kW. These single
shaft generator designs produce high frequency electric power at
cycle speeds greater than 1000 Hz, which in turn is converted to
high voltage DC current and then inverted back to 60 Hz current.
Single-shaft turbine/generator designs mount the compressor,
turbine, and electrical generator on a single shaft, which
generally has only one major moving part. Dual-shaft designs
require that a gearbox and associated moving parts be mounted
between the turbine and the generator. Single-shaft systems require
power electronics to convert high frequency generated power to
standard 50 or 60 Hz power. Dual-shaft systems rely on gear
reductions to regulate generator rotation speed to produce the
desired standard frequency power.
[0035] Reciprocating combustion engine driven electric generators
16 range in size from lightweight, portable designs with an output
of around 10 kW or less, to very large, low speed designs that can
generate up to 25 MWe of electrical output. Typically,
reciprocating combustion engines are classified as low speed
(300-750 rpm), medium speed (750-1,200 rpm), and high speed
(>1,200 rpm). The latter are more compact and lighter than low
speed designs and are often used for emergency/back-up or peaking
power with reduced operating hours. Low speed designs are typically
used for baseload power applications due to their lower maintenance
requirements. Combustion turbine driven electric generators range
in size from small micro turbines ranging in size from 30 to 80 kW,
all the way up to very large, stationary designs that deliver up to
175 MWe in output in a simple cycle mode.
[0036] One technique for improving the efficiency and/or output
from a combustion turbine is to recover some of the energy in the
hot exhaust gases--commonly referred to as waste heat recovery. By
directing the exhaust gases into a heat recovery steam generator,
high pressure steam can be generated to drive a steam turbine for
additional electrical output. This is referred to as a combined
cycle process because it is a combination of both a Brayton cycle
(the air-gas working fluid of a combustion turbine) and a Rankine
cycle (the water-steam working fluid used to drive the steam
turbine). Alternatively, a waste heat recovery boiler can be used
to generate hot water and/or low pressure steam that can be used
for process heat in a commercial or industrial application.
[0037] Waste heat recovery is also commonly used with combustion
engine applications. In this process, hot water and low pressure
steam can be generated by circulating water/antifreeze solutions
through the engine block and oil cooling systems, or by installing
heat exchangers in the exhaust gas path. The recovered heat can
then be used in various industrial and commercial processes. An
efficiency enhancement technique used for waste heat recovery on a
combustion turbine engine is to utilize the energy in the exhaust
to pre-heat the combustion air prior to entering the combustion
zone. This improves the simple cycle efficiency and is accomplished
via an air-gas heat exchanger called a recuperator.
[0038] These devices are commonly used on micro turbines and small
combustion turbines (less than 10 MWe), but become complex and cost
prohibitive on larger designs, in part due to increases in
operating pressures and the associated air gas sealing requirements
of the recuperator.
[0039] Microturbines operate a low compression ratios (4-5:1) and
firing temperatures, resulting in relatively low simple cycle
efficiencies. When equipped with recuperators, simple cycle
efficiencies between 20 and 28% (LHV) can be expected. Efficiencies
for small to medium-sized simple cycle combustion turbines in the
500 to 25,000 kW size range typically vary between 25% to 35%
(lower heating value-LHV) depending on pressure ratio and turbine
inlet temperature. High pressure ratios and turbine inlet
temperatures, achieved by using more exotic turbine blade materials
and/or blade cooling technologies, results in higher efficiencies
in the 35% to 40% range. Combined cycle applications boost the
efficiency to levels in the 35% to 55% range. The efficiencies of
combustion turbine driven power systems are dependent on
temperature, with values increasing at lower ambient or compressor
inlet temperature. Typical efficiencies for IC engines vary between
25% and 40% (LHV).
[0040] There are numerous manufacturers of reciprocating combustion
engine generators 16 in the U.S. and around the world. These
include Caterpillar, Waukesha, Wartsila, Jenbacher, Cummins,
Kohler, Cooper Bessemer, Fairbanks-Morse, Detroit Diesel, and
General Motors. An example of Caterpillar's natural gas fired
engine line is listed below: TABLE-US-00001 Model kW Output Speed
G3304 55-65 High - 1,800 rpm G3306 85-150 High - 1,800 rpm G3406
150-240 High - 1,800 rpm G3408 175-310 High - 1,800 rpm G3412
250-475 High - 1,800 rpm G3508 210-395 Medium - 1,200 rpm G3512
365-600 Medium - 1,200 rpm G3516 465-820 Medium - 1,200 rpm G3606
1,070-1,135 Medium - 900 rpm G3608 1,430-1,515 Medium - 900 rpm
G3612 2,160-2,290 Medium - 900 rpm G3616 2,880-3,050 Medium - 900
rpm
[0041] Major manufacturers of micro turbines include Capstone (30
and 60 kW models), Ingersoll-Rand (70 kW), Elliott/Ebara (80 kW),
Bowman, and Turbec. Manufacturers of larger turbine units include
General Electric, Siemens-Westinghouse, Ahlstom, Solar (a division
of Caterpillar), Rolls-Royce, Pratt-Whitney, US Turbine, Allison,
Hitachi and Kawasaki. Solar's line of turbine generator sets,
typical of the mid-range sizes used in distributed power
applications, are listed below: TABLE-US-00002 Model KW Output Type
Saturn 20 1,210 Simple Cycle Centaur 40 3,515 Simple Cycle Mercury
50 4,600 Recuperated Centaur 50 4,600 Simple Cycle Taurus 60 5,200
Simple Cycle Taurus 70 6,890 Simple Cycle Mars 90 9,285 Simple
Cycle Mars 100 10,685 Simple Cycle Titan 130 12,832 Simple
Cycle
[0042] The exhaust gas created from the turbine or reciprocating
engine is subsequently piped though exhaust gas piping 50 for
further treatment and injection as shown in FIG. 4. With regard to
the electric power generation, there are generally 1) direct
current generators and 2) alternating current generators as
discussed herein:
[0043] A generator is fundamentally a magnet spinning inside a coil
of wire. If a magnetic core, or armature, revolves between two
stationary coils of wire called field poles an electric current is
produced. This produced current in the armature moves in one
direction during half of each revolution, and in the other
direction during the other half. To produce current moving in only
one direction it is necessary to provide a means of reversing the
current flow outside the generator once during each revolution. In
original generators this reversal was accomplished by means of a
commutator, a split metal ring mounted on the shaft of the
armature. The two halves of the ring were insulated from each other
and served as the terminals of the armature coil. This was
accomplished by having fixed brushes of metal or carbon being held
against the split metal ring as it revolves. As the armature turns,
each brush is in contact alternately with the halves of the ring,
changing position at the moment when the current in the armature
coil reverses its direction producing a current flow in one
direction, or direct current (DC). In modem DC generators this
reversal is accomplished using power electronic devices such as
diode rectifiers. DC generators have the advantage of delivering of
comparatively constant voltage under varying electrical loads over
short line distances.
[0044] Like a CD generator an alternating current (AC) generator is
a simple generator without a commutator which will produce an
electric current that alternates in direction as the armature
revolves. Alternating current is more efficient over long line
electric power transmission distances. Due to this inherent
efficiency most power generators in use today are of the AC type.
Because it is often desirable to generate as high a voltage as
possible, rotating armatures as found in simple AC generators are
not practical because of the possibility of sparking between
brushes and slip rings and the danger of mechanical failures that
might cause short circuits. To eliminate this problem, AC
generators known as alternator rises to a peak, sink to zero, drop
to a negative peak, and rise again to zero numerous times each
second at a frequency dependent on input shaft rotation speed.
Single winding armatures produce single-phase alternating current
while two windings produce two phase current and so on. A larger
number of phases may be obtained by increasing the number of
windings in the armature, but in modern electrical-engineering
practice three-phase alternating current is most commonly used, and
the three-phase alternator is the dynamoelectric machine typically
employed for the generation of electric power.
[0045] A typical small-to-mid-sized combustion turbine that could
be used for distributed power by an electric utility, or for
on-site commercial or industrial power is the Solar Taurus 60. This
combustion turbine generator has a continuous ISO output of 5,200
KWe and heat rating of 11,263 Btu/kW-hr. The exhaust temperature
for this machine is 906.degree. F. at ISO conditions. The
combustion turbine and generator comes in a skid-mounted package
with a length of 28 ft.--9 in. and 8 ft.--6 in. in height and a
weight of approximately 65,000 pounds. The package includes an
exhaust collector, turbine assembly, combustor, compressor, air
inlet, gearbox, base frame, including fuel and oil systems,
generators, starter, and microprocessor-based control system. The
system may be purchased with an optional weather-resistant outdoor
enclosure, fire protection system, inlet air filters and ducting,
and outlet silencers and exhaust ducting. Along with this
equipment, a complete installation will include natural gas or fuel
delivery systems (piping, pressure regulation, metering, filtering,
valving), substation equipment (step-up transformer, breakers,
protective relaying, electrical metering equipment), foundations,
compressor wash equipment, stack, perimeter fencing, and lighting.
The site may also include a natural gas compressor (if required),
distillate storage and transfer equipment, emissions control
equipment (including stack analyzers), control room.
[0046] Upon creation of the desired electrical current from the
electrical generators, an electrical transformer substage may be
utilized. More specifically, several microturbine designs operate
at very high speed (greater than 50,000 rpm) and are coupled to an
electric generators on the same shaft. High frequency alternating
current (AC) is converted to direct current (DC) via a rectifier,
and then to 50 or 60 Hz AC power via an inverter. However, most IC
engine and CT electric generators, including one of the
microturbine designs, used a gearbox between the power unit and the
generators so that the generator rotates at 3,600 rpm (or a
multiple of this) to produce 60 Hz AC power.
[0047] The most common electrical output for microturbines and
small IC engine or CT generators is 3 phase, 480 volt power,
although there are variations in this between manufacturers. Larger
units typically produce 3 phase, 5 to 15 kilovolt power. In all
cases, a step-up (or step-down) transformer will be required if the
generators is to be connected to an electrical circuit or
distribution system that operates at voltages different than
these.
[0048] A large number of small industrial and commercial buildings
are connected to a 3 phase, 480 volt power supply. In this
instance, a microturbine with this output would not require a
step-up transformer. Electric distribution lines typically operate
at higher voltages.
[0049] Examples would be 7.2 kV, 12.5 kV, 24.9 kV, 44 kV and 69 kV.
Electric transmission lines operate at even higher voltages
including 115 kV, 230 kV, 345 kV, 500 kV and higher. In all cases,
transformers will be required if the voltage output of the
electrical generator is different than the electrical circuit at
the point of interconnection.
[0050] Electric generators that supply power to an isolated circuit
are said to be operating in a stand-alone or grid-independent
configuration. If the electric generators simultaneously supplies
power to both a low voltage circuit (building or industrial
process) and an electric distribution or transmission system, it is
said to be operating in a grid-parallel mode. In the event of a
loss (fault) on the electric distribution or transmission line, an
automatic transfer switch can be used under the right circumstances
to transfer power directly from the electric generators to the low
voltage circuit.
[0051] Upon generation of the electricity from the turbine or
reciprocating engine 14, electric generator 16 and electric
transformer 18, the electrical current must be compatible for
transmission into an existing electrical line grid 56. More
specifically, the lines of high-voltage transmission systems are
usually composed of wires of copper, aluminum, or copper-clad or
aluminum-clad steel, which are suspended from tall latticework
towers of steel by strings of porcelain insulators. By the use of
clad steel wires and high towers, the distance between towers can
be increased, and the cost of the transmission line thus reduced.
In modern installations with essentially straight paths,
high-voltage lines may be built with as few as six towers to the
mile. In some areas high voltage lines are suspended from tall
wooden poles spaced more closely together. For lower voltage
subtransmission and distribution lines, wooden poles are generally
used rather than steel towers. In cities and other areas where open
lines create a hazard, insulated underground cables are used for
distribution. Some of these cables have a hollow core through which
oil circulates under low pressure. The oil provides temporary
protection from water damage to the enclosed wires should the cable
develop a leak. Pipe-type cables in which three cables are enclosed
in a pipe filled with oil under high pressure (14 kg per sq cm/200
psi) are frequently used. These cables are used for transmission
and subtransmission of current at voltages as high as 3465,000 V
(or 345 kV).
[0052] Long transmission lines have considerable inductance and
capacitance. When a current flows through the line, inductance and
capacitance have the effect of varying the voltage on the line as
the current varies. Thus, the supply voltage varies with the load.
Several kinds of devices are used to overcome this undesirable
variation, in an operation called regulation of the voltage. The
devices include induction regulators and three-phase synchronous
motors (called synchronous condensers), both of which vary the
effective amount of inductance and capacitance in the transmission
circuit. Inductance and capacitance react with a tendency to
nullify one another. When a load circuit has more inductive than
capacitive reactance, as almost invariably occurs in large power
systems, the amount of power delivered for a given voltage and
current is less than when the two are equal. The ratio of these two
amounts of power is called the "power factor". Because
transmission-line losses are proportional to current, capacitance
is added to the circuit when possible, thus bringing the power
factor as nearly as possible to 1. For this reason, large
capacitors are frequently inserted as a part of power-transmission
systems.
[0053] Modem electric power grid systems use transformers to
convert electricity into different voltages. With transformers,
each stage of the system can be operated at an appropriate voltage.
In a typical system, the generators at the power station deliver a
voltage from about 1,000 to 26,000 volts (V). Transformers step
this voltage up to values ranging from 138,000 to 765,000 V for the
primary transmission line. At the substation, the voltage may be
transformed down to levels of 69,000 to 138,000 V for further
transfer on the subtransmission system. Another set of transformers
step the voltage down again to a distribution level such as 2,400
or 4,160 V or 15, 27, or 33 kilovolts (kV). Finally the voltage is
transformed once again at the distribution transformer near the
point of use to 240 or 120 V.
[0054] Referring now to FIG. 4, the exhaust gas 50 is shown being
processed and reinjected with additional process equipment needed
in one embodiment of the present invention. More specifically, the
exhaust gas piping 50 is operably interconnected to a subsequent
two phase separator 10 which removes any vapor and/or water content
from the exhaust gas. The piping is preferably high temperature
corrosion resistant materials which are specifically designed for
high temperature corrosive environment applications. The separator
10 may be a dehydration vessel with coalescing elements in one
compartment and a knitted wire mesh mist extractor in a second
compartment. These types of vessels are well known in oil and gas
industry and are manufactured by companies such as Anderson, Van
Air, J.L. Bryan, Process Equipment Co. and Wright-Austin.
[0055] The vapor or water removed from the exhaust gas is
subsequently reinjected into a subterranean formation and/or placed
in the storage tank for removal at a later date. The exhaust gas
exits the phase separator 10 and subsequently enters into a heat
exchanger/cooler which additionally removes any impurities from the
exhaust gas and/or creates condensation to remove additional water
content. Electrical or mechanical power produced in the power
generation stage could be used to power air cooling fans in the
exhaust gas collection and cooling stage. One example of such a
device is a blazed or aluminum heat exchanger to cool the gas to
allow efficient compressor operation. These types of coolers are
manufactured by companies such as Lytron, Fafco, Sewep, Power
Equipment and Hydro Thrift. The remaining cooled and dry exhaust
gas is then piped to a low pressure exhaust gas storage reserve
vessel which may be used to store static volumes of between about
6,000 scf and 60,000 scf of exhaust gas as desired.
[0056] The exhaust gas storage vessel 52 is in operable
communication with a gas compressor 26, which may be driven by an
electric motor 54 which obtains the electrical energy from the
electric generator which is being run by the produced hydrocarbon
fluids. The gas compressor may also be driven by direct mechanical
connection (shaft) from the generator or have its own secondary
drive engine. The gas compressor 26 is generally used to increase
the exhaust pressure from between about atmospheric pressure and
2.5 psi to about 420 and 5000 psi depending on the downhole
reservoir pressure of the subterranean formation in which the gas
is intended to be injected. Thus, the size and horsepower required
for the compressor 26 is dictated by the bottom hole pressure of
the subterranean formation utilized for reinjection purposes.
[0057] Compressors are designed to increase the pressure and
decrease the volume of a gaseous fluid. The three general types
currently in manufacture are 1) positive-displacement, 2) dynamic,
or 3) thermal types. Positive displacement compressors fall into
two basic categories including 1) reciprocating and 2) rotary.
Reciprocating compressors consist of one or more cylinders each
with a piston or plunger that moves back and forth, displacing a
positive volume of gas with each stroke. Rotary compressors types
are either lobe, screw, vane or liquid ring, with each having a
casing with one or more rotating elements that either mesh with
each other such as lobes or screws, or that displace a fixed volume
with each rotation. Dynamic type compressors include radial-flow,
axial-flow and mixed flow machines which are all rotary continuous
flow compressors in which rotating elements (impellers or blades)
accelerate the gas as it passes through the element. Thermal
"ejector" compressors use a high velocity gas or stream jet to
entrain an inflowing gas, then convert the velocity of the mixture
to pressure in a diffuser. Reciprocating (positive displacement)
compressors, which makeup the majority type for oil and gas
applications, have horsepower ratings that vary from fractional to
more than 20,000 hp per unit. Pressure ranges from low vacuum at
suction to 30,000 psi and higher at discharge with inlet flow
volumes ranging from less than 10 cubic feet/minute (cfm) to over
10,000 cfm. Reciprocating compressors are supplied in either
single-stage or multi-stage configurations depending on the overall
compression ratio needed. The compression ratio per stage is
generally limited by the discharge temperature and usually does not
exceed 4:1, although some small sized units are furnished with
compression ratios as high as 8:1. On multistage machines,
intercoolers may be installed between stages to remove the heat of
compression from the gas and reduce its temperature resulting in
overall higher efficiencies. Reciprocating compressors should be
supplied with clean gas as they cannot handle liquids and solid
particles that may be entrained in the inlet gas. Compressor types
and flow ratings to be unutilized for exhausted gas compression for
subterranean injection is dependent on the producing well(s) outlet
flow rate to the combustion generators, combustion engine types and
number, exhaust flow rates and cooling efficiencies. Some current
manufacturers of compressors for oil and gas facility applications
include Ariel, Atlas, Copco, Cooper, Dresser-Rand, Gardner Denver,
Gemini, Howden, Mycom, Neuman & Esser, Rix and Sundyne.
Compressors and drive engines/motors are generally sold as modular
units where all the various components are located on one skid or
truck mounted unit. Modular compressor units can be obtained for
any application from low pressure to high pressure. Some currently
available compressor/drive engine modules include the Caterpillar
G379TA/Knight KOA-2, Superior 6GTLB/Superior MW-62, Ajax
DPC-230/Single Stage, Waukesha VRG301/Ariel JGP1-2, and Waukesha
817/Inight KOA-2. Compressor induction exhaust gas flow rates by
constituent in lbs/hr for a 75 kW combustion turbine generator
engine: [0058] O2 1407 [0059] N2 5370 [0060] CO2 87 [0061] NOx 0.03
[0062] CO 0.02 Compressor induction exhaust gas flow rates by
constituent in lbs/hr for a 250 kW combustion turbine generator
engine: [0063] O2 4213 [0064] N2 16079 [0065] CO2 261 [0066] NOx
0.06 [0067] CO 0.07
[0068] Referring now to FIG. 5, a typical injection wellbore 8 of
the present invention is provided herein. More specifically, the
compressed exhaust gas which exits the compressor is operatively
piped via exhaust gas piping 50 to a wellhead of an injection
wellbore 8. In some applications it may be desirable to have the
exhaust gas metered for total volume and monitored for molecular
constituents prior to injection. The injection wellbore may again
include pressure gauges 40 and other valves 38 to regulate the flow
and/or back pressure of the injection wellbore 8 positioned
downstream from the gas compressor 26. In the embodiment shown in
FIG. 5, the injection wellbore 8 comprises wellbore tubing 36 which
is positioned between two or three strings of wellbore casing 34
which protects the wellbore from the surrounding earth materials
and to prevent any unwanted communication of produced fluids. The
production tubing 36 is isolated from the wellbore casing 34 by
means of a packer 58, which prevents communication of the injected
exhaust gas to the wellbore casing 34. The wellbore casing 34
additionally has a plurality of perforations 48 positioned opposite
the non-producing geologic formation 4 and which allows the
injected exhaust gas to flow from the exhaust gas piping 50 through
the injection wellbore 8 and into the non producing geologic
formation 4.
[0069] As appreciated by one skilled in the art, in a further
embodiment of the present invention the exhaust gas may be injected
into a currently producing geologic formation 2 to enhance the
ultimate recovery of the natural gas since the bottom hole pressure
is increased. Depending on the bottom hole pressure of the existing
producing geologic formation 2, and the availability of other
non-producing geologic formations 4, the operator may determine
whether or not to utilize the producing geologic formation 2 and/or
utilize a non producing geologic formation 4 for injection
purposes. On some occasions, the exhaust gas may be injected in
both a non-producing geologic formation 4 and a producing geologic
formation 2 simultaneously as engineering principles and economics
dictate.
[0070] Referring now to FIG. 6, one alternative embodiment of the
present invention is shown herein, wherein the same wellbore is
utilized for both production and injection purposes. More
specifically, the producing geologic formation 2 is shown on the
lower portion of the drawing, while a non-producing geologic
formation 4 is shown positioned above at a shallower depth. Thus,
the natural gas or other hydrocarbons are produced from the
producing geologic formation 2 into the production tubing 36 and
subsequently through the wellhead, into the phase separator 10 and
other process equipment. After treatment of the natural gas and
subsequent generation of electrical energy, the exhaust gas is
returned to the wellbore via exhaust gas piping 50 and is injected
through the production casing/production tubing annulus 60 through
the perforations 48 and into the non producing geologic formation
4.
[0071] Thus, in this particular example, the produced hydrocarbons
are flowed through the production tubing 36, while waste exhaust
gas is reinjected into the wellbore casing/production tubing
annulus 60 and reinjected into the non-producing geologic formation
4. Thus, one producing wellbore can be utilized for both production
and injection purposes, provided that at least one producing
geologic formation 2 is located at a greater depth from a non
producing geologic formation 4. As appreciated by one skilled in
the art, depending on the various geologic formations and available
downhole wellbore designs, any variety of combinations of injection
and/or production scenarios may be utilized to accomplish the scope
of the present invention.
[0072] For clarity purposes, the following list of the components
and the numbering associated therein in the drawings is provided
herein: TABLE-US-00003 Number Component 2 Producing geologic
formation 4 Non producing geologic formation 6 Producing geologic
formation 8 Injection wellbore 10 Phase separator 12 Meter 14
Turbine or reciprocating engine 16 Electric generator 20 Electric
transmission grid 22 Exhaust gas treatment vessel 24 Piping 26 Gas
compressor 28 Gas storage vessel 30 Heat exchanger/cooler 32 Gas
scrubber/cleaner 34 Wellbore casing 36 Wellbore tubing 38 Valve 40
Pressure gauge 42 Oil/water storage vessel 44 Wellhead 46 Ground
surface 48 Perforations 50 Exhaust gas piping 52 Exhaust gas
storage vessel 54 Electric motor 56 Electric line 58 Wellbore
packer 60 Production casing/tubing annulus
[0073] The foregoing description of the present invention has been
presented for purposes of illustration and description. The
description is not intended to limit the invention to the form
disclosed herein. Consequently, the invention and modifications
commensurate with the above teachings and skill and knowledge of
the relevant art are within the scope of the present invention. The
preferred embodiment described above is also intended to explain
the best mode known of practicing the invention and to enable
others skilled in the art to utilize the invention in various
embodiments and with the various modifications required by their
particular applications for use of the invention. It is intended
that the claims be construed to include all alternative embodiments
as permitted by the prior art.
* * * * *