U.S. patent application number 12/813663 was filed with the patent office on 2010-10-28 for method of developing and producing deep geothermal reservoirs.
Invention is credited to Harry B. Curlett.
Application Number | 20100272515 12/813663 |
Document ID | / |
Family ID | 35782348 |
Filed Date | 2010-10-28 |
United States Patent
Application |
20100272515 |
Kind Code |
A1 |
Curlett; Harry B. |
October 28, 2010 |
METHOD OF DEVELOPING AND PRODUCING DEEP GEOTHERMAL RESERVOIRS
Abstract
A method of drilling, completing and producing a deep geothermal
reservoir to allow the economical extraction of thermal energy from
geologic strata, which may be termed as Hot Dry Rock (HDR).
Inventors: |
Curlett; Harry B.; (Cody,
WY) |
Correspondence
Address: |
WINSTEAD PC
P.O. BOX 50784
DALLAS
TX
75201
US
|
Family ID: |
35782348 |
Appl. No.: |
12/813663 |
Filed: |
June 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10581648 |
Apr 13, 2007 |
7753122 |
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PCT/US05/22305 |
Jun 23, 2005 |
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12813663 |
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60582626 |
Jun 23, 2004 |
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60650667 |
Feb 7, 2005 |
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Current U.S.
Class: |
405/55 ; 166/245;
166/308.1; 175/331; 175/424 |
Current CPC
Class: |
E21B 43/17 20130101;
F24T 10/20 20180501; Y02E 10/10 20130101; Y02E 10/14 20130101 |
Class at
Publication: |
405/55 ;
166/308.1; 175/424; 166/245; 175/331 |
International
Class: |
B65G 5/00 20060101
B65G005/00; E21B 43/26 20060101 E21B043/26; E21B 7/18 20060101
E21B007/18; E21B 43/30 20060101 E21B043/30; E21B 10/08 20060101
E21B010/08 |
Claims
1. A method of extracting thermal energy from a rock formation, the
method comprising the steps of: drilling a plurality of wells to a
depth sufficient to allow development of at least one fracture
joint cloud reservoir; hydraulically fracturing at least one of the
plurality of wells; dilating the at least one fracture joint cloud
reservoir; forcing cooled water under high pressure and volume into
at least one of the plurality of wells to charge the reservoir;
alternately opening and closing a plurality of discharge control
valves and a plurality of injection control valves to provide
continuous flow from the plurality of wells and permit discharge
from the reservoir; removing heated water from the wells; and
passing the heated water to a heat exchanger.
2. The method of claim 1, wherein the step of drilling includes the
step of hydraulic drilling.
3. The method of claim 2, wherein the step of hydraulic drilling
includes particle jet drilling.
4. The method of claim 1, wherein a volume of the at least one
fracture joint cloud reservoir is increased through simultaneous
mechanical and thermal cycling.
5. The method of claim 1, wherein heat values in the at least one
fracture joint cloud reservoir are maintained through mechanical
and thermal cycling of the reservoir rock.
6. The method of claim 5, wherein the volume of heat that may be
swept in the at least one fracture joint cloud reservoir is
increased through thermal and mechanically cycling reservoir
rock.
7. The method of claim 1, wherein the step of charging and
discharging of the system is further includes the step of timing
the charging and discharging to produce a sequence of cycles with
steady state load following production cycles generated while still
inducing coincidental thermal mechanical cycling that results in
brecciation and spallation of the reservoir rock.
8. The method of claim 7, wherein the method of heat production is
further facilitated by utilizing at least two wells wherein an
injection well injects periodically at different injection rates so
that the rate is greater than the continuous production rate
produced from the production well such that the reservoirs
alternately expanded and then allowed to contract in order to
generate the combined thermal and mechanical stresses necessary to
generate in situ reservoir brecciation while the reservoir is being
produced at a continuous rate.
9. The method of claim 7, wherein the method is further facilitated
by utilizing at least three wells.
10. A method of completing geothermal production wells including
the steps of: drilling a plurality of wells from at least one
wellhead through a plurality of earthen formations; utilizing a
first type of drill bit through first upper earthen formations for
the generation of the well bore; utilizing a particle jet drilling
bit for bore hole creation within a hot dry rock region disposed
beneath the first earthen region; terminating a first plurality of
bore holes in a first Precambrian formation to a depth of
sufficient temperature to allow the development of one or more
discreet formation fracture joint clouds which are oriented
vertically or horizontally as determined by the rock formation;
terminating a second of the plurality of bore holes into a lower
region for creating a lower fracture joint cloud generally
horizontally disposed beneath the first cloud; and hydraulically
fracturing each cloud to produce a reservoir volume of dilated
joints in the formation by pumping at pressures in excess of the
joint dilation pressure and the formation break down pressure.
11. The method as set forth in claim 10 and further including
terminating a third bore hold beneath the regions of termination of
the first and second bore holes.
12. The method as set forth in claim 10, wherein the step of
fracturing includes imparting a pressurization cycle to charge the
reservoir followed by the depressurization of the reservoir to
flush the heated water from the dilated joints that produce the
heat absorbed by the water during the pressurization and
depressurization cycle.
13. The method as set forth in claim 12 and further including
repeating the process of charging and depressurizing each cloud to
develop an aggregate of a plurality of discreet reservoirs that
will accept pressurized water to charge the reservoir during
dilating the joints allowing the water to travel into the reservoir
to be heated and then expelled from the reservoir when the heated
water pressure is lowered in the well bore from a wellhead.
14. The method of claim 13 including the step of continuously
producing heated water by timing the pressure cycling of the well
bore to provide one well being injected into at twice the rate the
well is reversed flowed.
15. The method of claim 14 and further including routing cooled
well bore fluid back down the well bore through a control valve to
an injection pump.
16. The method of claim 14 and further including discharging cooled
well bore fluid from the heat exchanger to a surface reservoir
pit.
17. The method of claim 1, wherein the step of fracturing comprises
the step of dilating a plurality of material joints in the
formation.
18. The method of claim 1, wherein the step of drilling includes
drilling an upper well portion with a rotary mechanical drill
bit.
19. The method of claim 18, wherein the rotary-mechanical drill bit
comprises PJARMD methodology.
20. A method of drilling deep well bores from a wellhead into
Precambrian and Hadean Era crystalline rock formations for
accessing thermal energy therein comprising the steps of:
establishing a bore hole drilling system from the wellhead with at
least a first and a second type of drilling methodology, the first
methodology including rotary-mechanical drilling and a second
methodology including hydraulic drilling; drilling a first bore
hole section from the wellhead and into a first formation utilizing
the first methodology of the rotary-mechanical drilling; drilling a
second bore hole section beneath the first bore hole section into
the crystalline rock formation with the second drilling methodology
of hydraulic drilling; and exposing the thermal energy within the
crystalline rock for the access thereto.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a continuation of U.S. patent
application Ser. No. 10/581,648, filed on Apr. 13, 2007. U.S.
patent application Ser. No. 10/581,648 is a U.S. National Stage
filing of International Application Number PCT/US2005/022305, filed
on Jun. 23, 2005. PCT/US2005/022305 claims priority from U.S.
Provisional Patent Application No. 60/582,626, filed on Jun. 23,
2004 and U.S. Provisional Patent Application No. 60/650,667 filed
on Feb. 7, 2005. PCT/US2005/022305, U.S. patent application Ser.
No. 10/581,648, U.S. Provisional Patent Application 60/582,626, and
U.S. Provisional Patent Application No. 60/650,667 are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the drilling of well bores,
well completion methods, and the extraction and/or utilization of
thermal energy from rock formations beneath the surface of the
earth.
[0004] 2. History of Related Art
[0005] Permeable geologic strata having high temperatures are found
in numerous site-specific locations around the globe. When meteoric
water percolates down into these formations, the water is heated
and may flow to the surface as geysers and hot springs. Impermeable
geologic rock formations, typically Precambrian rocks, having high
temperatures are found almost everywhere around the globe and are
generally located at deeper depths than high temperature permeable
geologic strata which is typically sedimentary rock in nature.
These impermeable Precambrian formations are generally considered
dry and heat may be recovered from these formations by means of the
hot dry rock (HDR) geothermal production process in which water is
pumped down a well drilled into these deep hot impermeable rock
formations and heated by contact with the rock. If the rock in its
natural state does not have a sufficient network of cracks and
fissures for the water to flow through to pick up heat, as is the
usual case, the rock is hydraulically fractured to produce such a
fracture network by means of fluid pressure. Various means to
continuously circulate the heat from these HDR formations have been
established.
[0006] Today, energy is supplied primarily by fossil fuels such as
coal, oil, and gas. These resources are finite and are expected so
to be in short supply in the readily foreseeable future. Also, the
use of fossil fuels appears to cause serious environmental
problems. Further, the United States currently imports a large
percentage of its oil. Dependence on foreign oil is increasing as
domestic reserves diminish. Thus, development of alternative
sources of energy is necessary. When coal is burned, significant
amounts of sulfur and nitrogen oxides are released to the
atmosphere. These gases combine with water in the atmosphere to
produce acids, which are brought to earth by rainfall downwind of
the emissions source. This "acid rain" has a deleterious effect on
aquatic and plant life. On a mere long-range scale, the atmosphere
may be warming because of the "greenhouse effect" which may be
caused by large quantities of carbon dioxide being released to the
atmosphere as a result of burning of fossil as fuels. The long-term
consequences of the greenhouse effect are currently a matter of
debate; they may include melting of the polar ice caps, with the
resultant increase in sea level and flooding of coastal cities, and
increased desertification of the planet. Evidence pointing toward
greenhouse effect warming includes increases in the carbon dioxide,
content of the atmosphere over the past century and weather records
that seem to indicate an upward trend in atmospheric temperatures.
These facts point to the need, to consider mitigating action now,
before we are overtaken by our own emissions.
[0007] Hydropower, the world's primary non-fossil energy source, is
both inexpensive and clean. Hydropower has been widely developed in
many parts of the world, but will never fill more than a small part
of the world's total energy needs. Other alternative energy sources
are nuclear fission, solar, wind, fusion, and geothermal. Nuclear
fission is already widely used, but is currently suffering from a
lack of public confidence, particularly in the United States, as
the result of common knowledge of such incidents as Three Mile
Island and Chernobyl. There are few nuclear power plants currently
in the planning or construction stages. Solar power has been
demonstrated on a small scale, as has wind power. Although both of
these are renewable energy sources, they are subject to the whims
of local weather conditions and can be relied upon to deliver power
only intermittently. Nuclear fusion is, potentially, an almost
unlimited source of energy, relying for fuel upon isotopes of
hydrogen, which are found in abundant amounts in seawater. However,
fusion has been unambiguously demonstrated only in the highly
intractable form of a thermonuclear explosion. Decades may pass
before ignition and containment of a fusion reaction by
controllable, non-nuclear ignition sources, such as lasers, will be
developed to the point where nuclear fusion may find practical
application as a power source.
[0008] Geothermal resources, in the form of naturally occurring
hydrothermal fluid systems, are being exploited today to provide
useful energy as electrical power or heat in many parts of the
world. At present, hydrothermal sources provide only a minute
fraction of the world's energy needs, though the potential resource
base available for exploitation is of the same order of magnitude
as fossil fuel resources. Hydrothermal resources are much cleaner
than fossil fuels with regard to greenhouse gas emissions,
generally releasing only about 10 percent or less of the amount of
carbon dioxide produced by burning an energy-equivalent amount of
fossil fuel. However, hydrothermal resources are of limited
geographical extent, occurring primarily in areas of tectonic or
volcanic activity. Thus, many densely inhabited parts of the world
are poorly located for the exploitation of hydrothermal
sources.
[0009] Hot Dry Rocks (HDR), typically Precambrian rocks, underlie
much of the globe. Unlike hydrothermal resources, HDR is widely
distributed about the earth, generally underlying the sedimentary
based hydrothermal formations. The HDR resource potential is a
resource of vast magnitude and, like fusion, HDR can provide an
almost unlimited source of energy for the planet. Hydrothermal
plants now in operation demonstrate conclusively that the heat of
the earth can be used as a practical source of both thermal and
electrical energy. The HDR process is a logical extension of
hydrothermal technology to tap into a vastly larger and universally
distributed energy resource.
[0010] The conventional teaching of extracting energy from HDR
involves creation of a closed liquid circulation system comprised
of an HDR reservoir and the aboveground equipment. Initially, an
injection well is drilled into hot dry rock and hydraulic
fracturing techniques are used to induce permeability by
stimulating existing natural joints or creating new fractures.
Hydraulic stimulation and fracturing are widely used in petroleum
recovery. An HDR reservoir is thus created, the size of which is
governed by the pressure, rate and volume of the hydraulic
fracturing fluid applied to the rock, the nature of the rock
structure, and in situ stresses as have been clearly demonstrated
in modern HDR completions such as those cited in Geodynamics
Limited Quarterly Report period ending Mar. 31, 2004. Additional
wells are subsequently drilled to provide the rest of the fluid
circuitry necessary for establishing the closed loop circulation
system. To produce heat production, liquid is pumped down the
injection well, heated by the hot rock of the HDR reservoir, and
recovered from a second well, a production well, drilled into the
reservoir at some distance from the injection well. Multiple
injection and recovery wells may be used within the basic closed
loop circulation system. Heat exchangers at the surface are used to
recover the heat from the water for use in electric power
generation or for direct thermal applications. The water is then
re-injected into the HDR reservoir via the injection well. In this
manner, heat can be continuously mined from otherwise inaccessible
geothermal sources. Essentially no venting of gaseous or saline
fluids to the environment occurs. Thus, the HDR process does not
emit carbon dioxide or acid rain precursors, such as sulfur
dioxide, and is in the same class as solar, wind, or hydropower in
being an environmentally benign source of energy. The primary
application of water heated in an HDR reservoir will be to generate
steam or to vaporize another working fluid, such as ammonia or
isobutane, for use in producing electric power.
[0011] U.S. Pat. No. 3,786,858, issued Jan. 22, 1974, describes the
HDR process. A publication issued by the Los Alamos National
Laboratory in July, 1989 which is designated LA-1 15 14-MS and
entitled "Hot Dry Rock Geothermal Energy a New Energy Agenda for
the 21st Century, describes a number of concepts for use of HDR
energy. There are experimental HDR sites in Europe, Japan, the U.S.
and commercial HDR ventures in the process of being developed in
Europe and Australia. The Geothermal Resources Council periodically
publishes a bulletin dealing with geothermal energy matters. The
SPE Paper No. 30738 titled--"Hot Dry Rock: A versatile Alternative
Energy Technology" by D. V. Duchane, Earth and Environmental
Sciences Div., Los Alamos National Laboratory, presented October
1995 describes the current state of the HDR development.
[0012] The public offering prospectus offered by Geodynamics
Limited of Australia, entitled "Geodynamics Limited--ABN 55 095 006
090--Power from the Earth Prospectus" dated Aug. 13, 2002 provides
the most modern thought process and effort to develop and
commercialize a HDR electrical generation system. The Geodynamics
HDR model provides for multiple "lens" of opened natural rock joint
groups to be vertically interconnected through common injection and
production well bores to provide the basis from which to mine heat
from a "triplet" of wells. The heat is mined from the reservoir
rock through continuous circulation from an injector well to
multiple production wells that provide a pressure sink in order to
induce directional circulation. This commonly-known configuration
provides a point-to-point directionally-specific pressure-sink-type
closed-loop circulation system.
[0013] Companies which provide electric power must have sufficient
power generating capacity to not only meet base load demand but
also must meet peak demand, or maximum demand, which usually occurs
in the late afternoon of a hot summer day. Power production
apparatus which is in reserve must be capable of being brought
on-line very quickly, in order to prevent "brown-outs" or load
shedding. Load shedding refers to cutting off power to some users
in order to avoid catastrophic shut-down of the entire system. Such
apparatus is commonly termed "spinning reserve". Spinning reserve
power, or peaking power, is costly because the equipment used to
generate spinning reserve power is in revenue-generating use only a
portion of the time rather than 24 hours a day. Also, the equipment
is generally more expensive to purchase and operate than base-load
electric power production equipment.
[0014] U.S. Pat. No. 5,685,362, issued Nov. 11, 1997 describes a
method for meeting peak power demands with a HDR heat mining system
and a power generating plant. Thus, the U.S. Pat. No. 5,685,362
invention effectuates use of an HDR power generation system for
electric load following. The U.S. Pat. No. 5,685,362 invention may
also be termed on-demand power peaking. Peaking power from an HDR
system would be cheaper to generate than peaking power from other
sources yet can be sold at the same price as peaking power
generated by other means, such as a gas turbine. Use of an HDR
system in a load-following mode rather than just to provide
base-load power will reduce the total cost of operation of an HDR
system. The incremental cost of equipment to operate in peaking
mode is expected to be modest. This process is described in an
undated paper titled "The Geothermal Analog of Pumped Storage for
Electrical Demand Load Following" by Donald W. Brown, Los Alamos
National Laboratories, Earth and Science Division, Los Alamos, N.
Mex. 87545. The invention U.S. Pat. No. 5,685,362 invention teaches
the practice of heat mining by continuous fluid circulation through
an injection and multiple production wells coupled with the method
of periodic reduction of the production well back pressure to allow
a short term flow of a greater volume than the steady state flow
volume to be produced thereby providing periodic "peaking" power
capacity to provide electrical generation load following
characteristics.
[0015] The gasification of organic material under supercritical
water conditions as taught by Modell et al in U.S. Pat. No.
4,113,446 issued Sep. 12, 1978, titled: Gasification Process, is
known in the art. Also the use of a subterranean well bore for the
purpose of providing a gravity based reactor vessel from which to
perform continuous supercritical water chemical reactions as taught
by Titmas in U.S. Pat. No. 4,594,164, issued Jun. 10, 1986, titled:
"Method and Apparatus for Conducting Chemical Reactions at
Supercritical Conditions", is exemplary of the state of the art
that is also known. These teachings provide a process of conversion
of organic material by way of supercritical water anaerobic
gasification. Oil and gas resources are a finite resource whose
production capacity is rapidly declining and it is therefore
essential that the organic carbon found in coal that is found in
vast quantities on a world wide basis become useful through the
ability to convert coal to clean burning fuel gasses and liquids
while capturing the various other marketable or harmful
constituents for useful sale or disposal as the case may be.
[0016] The HDR concept of generating geothermal heat has been know
for many decades and has generally been relegated to a
non-commercial technology due to the prohibitively high cost of
drilling multiple wells into the deeply buried crystalline type
Precambrian hot dry rock formations. Modern attempts to
commercialize the HDR method of generating geothermal energy have
to locate a very unique set of conditions in geologic areas that
exhibit exceptionally high geothermal gradients to provide
manageable project drilling costs vis-a-vis relatively shallow
drilling depths. Typically, these developments seek a site that has
significant sedimentary overburden before drilling into the
Precambrian formations to access the HDR thus being minimizing
drilling costs by drilling a minimal section of the well bore in
the Precambrian type rock. Further, these modern attempts to
commercialize the HDR geothermal production are economically
restricted by the high cost of drilling injection and multiple
production wells. The high cost well bores severely constrain the
project design from being designed as an optimal production system
to mine the maximum heat available in the source rock.
[0017] The present invention provides a method of drilling,
completing and producing a geothermal reservoir in order to a)
economically locate said geothermal reservoirs in most all areas of
the world, even those areas with lower thermal gradients that are
currently uneconomical to produce, b) economically locate said
geothermal reservoirs at depths that provide supercritical water
conditions, c) maximize the effective recovery of geothermal heat,
per unit volume of HDR formation and d) provide a method of
producing and utilizing said geothermal heat energy for individual
or simultaneous direct and/or indirect applications such as any
individual or combination of the generation and use of high
temperature geothermal process steam, the generation and use of
geothermal heat energy for the production of electricity and/or the
generation and use of geothermal heat energy in the processing of
organic carbon or other chemical reactions.
SUMMARY OF THE INVENTION
[0018] The present invention relates to a method of drilling,
completing and producing a deep geothermal reservoir to allow the
economical extraction of thermal energy from geologic strata, which
may be termed as Hot Dry Rock (HDR).
[0019] In one embodiment, the present invention relates to a method
of economically drilling deep well bores in Precambrian and or
Hadean Era crystalline rock, such as granites basalts and the like,
which is typical of HDR formations. The cost of drilling well bores
into HDR using the current practice of rotary-mechanical drilling
methods has virtually eliminated the opportunity to tap the vast
HDR potential. The novel application of using a predominantly
hydraulic based drilling method to overcome the inherent
disadvantages of the rotary-mechanical system such as slow rate of
penetration and crooked hole tendencies will provide an economical
means of tapping into the vast HDR potential. Specifically
contemplated is the use of Particle Jet Drilling (PJD) methods of
hydraulic drilling to overcome the rotary-mechanical disadvantages.
A major advantage of certain embodiments of the present invention
includes combining the use of PJD of deep well bores terminating in
HDR formations. This should sufficiently reduce the cost of
accessing the higher temperature HDR depths providing the highest
energy density production possible for economic exploitation of the
vast HDR source.
[0020] In another embodiment, the present invention relates to a
method of developing a high temperature HDR geothermal reservoir to
supply the geothermal heat energy for applications such as
electrical power generation, including base load and load following
capabilities, the processing of various organic materials to
produce marketable products such as clean burning fuel gasses and
liquids, purified liquids, processed organic waste materials and
other chemical reactions.
[0021] In another aspect, one embodiment of the present invention
relates to a system which provides the sequenced charging and
discharging of the HDR reservoir from one or more groups of
vertically or horizontally separated dilated rock joint groups or
reservoirs. This aspect of the invention provides the ability to
produce significantly greater volumes of heat energy from each HDR
reservoir system of fractures when compared to the conventional
method of producing heat energy from an HDR reservoir system of
fractures. Additionally, this method of producing an HDR reservoir
system provides an increase in the HDR reservoir productivity over
time due to the reservoir enlarging effects of simultaneous thermal
and mechanical pressure cycling of the reservoir system when
compared to the conventional method of producing an HDR
reservoir.
[0022] In another aspect, one embodiment of the present invention
relates to a method of extracting thermal energy from a rock
formation. The method comprising the steps of drilling a plurality
of wells to a depth sufficient to allow development of at least one
reservoir comprising a cloud of fracture joints, hydraulically
fracturing at least one of the plurality of wells, dilating at
least one fracture joint cloud reservoir, forcing cooled fluid
under high pressure and volume into at least one of the plurality
of wells, alternately opening and closing a plurality of discharge
control valves and a plurality of injection control valves to
provide either periodic or continuous flow from the plurality of
wells, removing heated fluid from the wells, and either passing the
heated fluid to a heat exchanger or using the produced fluid for
direct use applications.
[0023] In another aspect, embodiments of the invention provide a
method of reducing the high cost of drilling deep well bores
terminating in Precambrian and or Hadean Era crystalline rock that
are well known in the oil and gas and geothermal industries. The
cost of drilling these wells into the Precambrian or Hadean rock is
a major part of the cost that limits the depth, diameter, and
number of wells that can be used to economically exploit the HDR
geothermal resources. The first part of the invented method for
producing widespread geothermal resources is the significant
reduction of the drilling costs associated with drilling deep well
that terminate in Precambrian and or Hadean rock for the purpose of
developing HDR engineered reservoirs. The significant drilling cost
reduction is achieved by the use of particle jet drilling (PJD)
methods to drill the well bore necessary to access, generate and
produce the HDR reservoirs.
[0024] The experimental use of jetted particles intended for
drilling oil and gas wells has been well documented by the oil and
gas industry. There are primarily two forms of drilling processes
incorporating high mass particles entrained in the drilling fluid.
The use of high mass particles entrained in drilling fluids was
demonstrated by Gulf Oil Company in the early 1969's based, on U.S.
Pat. No. 3,348,189, issued May 21, 1968 and the more recent use of
larger diameter high mass particles entrained in the drilling fluid
has been patented by the inventor as U.S. Pat. No. 6,386,300 issued
May 14, 2002. These references particularly focus on the use of
Particle Jet Assisted Rotary Mechanical Drilling (PJARMD). The
referenced methods of drilling deep wells with PJARMD embodies the
process of entraining discrete high density solid particles in the
drilling fluid in order to cut the formation using the impulse
energy imparted to the rock by the momentum transmitted from the
high mass particles to abrade, chip, fracture, crack, displace or
generally fail the formation and remove the formation at a rapid
rate. PJARMD processes have been successfully demonstrated in lab
tests to increase the drilling rate of various earthen formations.
Certain experimental PJARMD field tests have been conducted in
conjunction with the drilling of oil and or gas wells in
sedimentary formations. The testing of a fully Hydraulic Particle
Jet Drilling (HPJD) method of jet drilling crystalline rocks has
also been lab and field tested. The application of PJARMD and HPJD
for reducing the cost of well bores terminating in Precambrian or
Hadean formations is fundamental to the widespread development of
the HDR potential. Specifically, PJD provides a means to
economically drill large diameter, very deep injection and
production well bores for HDR production purposes.
[0025] The utilization of the two PJD methods, in concert with
specialized completion and production methods further described
herein will collectively serve to generate widespread development
and use of HDR geothermal energy. Cost effective geothermal well
bore drilling provides the ability to locate economical HDR
geothermal energy production close to existing end-users in order
to displace fossil fuel usage especially when the end-user
application is situated on a low thermal gradient site.
[0026] The ability to hydraulically dilate the existing natural
joints in the crystalline rock at depth to form a network of
pressure dilated joint permeability in which fluids can be
circulated is well documented in the HDR literature.
[0027] The method of HDR heat mining by means of continuous
circulation between multiple wells that are so arranged to create a
directionally specific point to point pressure sink type flow path
through a cloud of dilated joints or fractures that are
artificially generated by means of hydraulically fracturing the
normally impermeable HDR formation is well documented in the
general HDR literature. The present invention relates to the method
of producing from a HDR fracture cloud system by means of
alternating the hydraulic expansion and contraction of the fracture
cloud system in such a manner as to generate coincidental or
sequenced thermal and mechanical cycling of the HDR formation in
order to generate periodic or continuous near facture surface
brecciating within the HDR formation. This brecciation serves the
purpose of incrementally exposing new high thermal differential
surfaces, on an incremental basis, that will provide the means to
maintain high temperature production, mine the HDR formation of
heat more effectively through incremental surface exposure and
generate an increased reservoir capacity over time through
formation brecciation which will increase the surface area that is
being swept over time.
[0028] Embodiments of the present invention further relate to
generating a reservoir production method that eliminates the
conventional directionally specific point to point pressure sink
type flow path of the commonly known conventional HDR production
system. The present invention utilizes the hydraulic pressurization
of the reservoir on a per cycle basis to inject fluid into all
areas of the reservoir. This charging action stores elastic strain
energy in the HDR formation. The reservoir is then allowed to
produce the injected fluid to one of more production wells within
the reservoir through the contraction of the reservoir volume due
to the relaxation of the elastic strain energy stored in the
reservoir rock. The flow distributive and recovery flow paths
through the joint system generated by this type of production
method is omni-directional both during the injection cycle and the
production cycle. This has the effect of substantially increasing
the surface area swept by the working fluid as opposed to the
commonly known methods of point to point pressure sink
directionally specific flow paths of the current HDR production
methods.
[0029] Embodiments of the present invention further relate to the
step of developing one or more discrete reservoirs through dilating
a group of joints to form said reservoir. This reservoir is then
alternately charged and discharged with a fluid in order to dilate
the reservoir and cause the fluid to pass into and then
subsequently out of the reservoir. This method is expected to force
the fluid to sweep the dilated joint surface in two directions thus
providing a longer duration for the fluid to be able to absorb the
heat from the rock. The cyclical inducement of simultaneous
mechanical and thermal stress reversals on the reservoir rock face
stresses the crystalline rock at or near the reservoir rock face
and causes the reservoir rock face to continuously brecciate or
spall exposing new reservoir rock surface. This type of brecciation
is termed shear banding and generates a network of crisscrossed
fractures on the surface of the larger fracture surface being swept
of its heat. This shear band brecciation can form brecciated or
spalled rock pieces that range in size from very small to very
large depending on many variables. This type of active brecciation
continuously provides newly exposed reservoir surface area that
will promote greater heat transfer due to incremental exposure of
the rock massive to the water sweeping its heat. Further, the
brecciation process will provide an ever increasing surface area
from which to sweep heat and therefore an increased capacity to
produce heat over time. This cyclical method of multiple stress
reversals results in a continuous and incremental increase in the
high thermal differential surface area exposed and an increase in
reservoir volume. The rock formation being broken down by these
cyclical stress reversals is expected to provide the ability to
continually sweep the heat from the rock formation in a manner that
allows an increased efficiency in removing a greater amount of the
heat density available per unit volume than with conventional HDR
production methods. Additionally, this method of reservoir
production provides for little or no water loss as normally
characterized by directionally specific point to point pressure
sink type flow path closed loop circulation through two or more
wells as practiced by prior hot dry rock production methods. These
conventional directionally specific point to point pressure sink
type flow path HDR production methods tend to hydraulically isolate
great portions of the reservoir which may not be produced using the
conventional HDR production methods. The production method of the
present invention provides a nearly full flow recovery on each
pressure cycle of the charged reservoir volume to a central
production point(s) due to the omni-directional charge and flow
back fluid paths. As the reservoir of the present invention
matures, fluid cross-circulation is expected to occur within the
reservoir which will assist in convectional heat recovery from the
reservoir.
[0030] The reservoir systems can be a) a single discrete reservoir
that is independently cycled to produce a cyclical or periodic
production, b) a set of multiple independent reservoirs that can be
cycled and sequenced so as to produce a continuous production flow
that can be steady state or fluctuating for purposes such as load
following and/or c) a single reservoir that has multiple wells that
can serve the purpose of simultaneous injection and production in a
manner that the injection wells inject periodically at a rate that
exceeds the production rate on a cycled basis in order to
cyclically expand the reservoir and store energy in the form of
elastic strain while a production well continually produces at a
steady or fluctuating rate.
[0031] Embodiments of the present invention further relate to
reservoirs that can be a) vertically stacked but remain independent
and isolated from adjacent reservoirs and b) horizontal arranged
but remain independent and isolated from adjacent reservoirs. The
arrangement of the reservoirs will be generally dependant on the
type and magnitude of the stress field associated with the local
HDR formations. The timing of the charging and discharging of the
systems can be timed to produce a sequence such that a cyclical or
a steady state or steady state with load following production
cycles can be generated while still educing coincidental thermal
and mechanical cycling that results in the brecciation or
spallation of the reservoir rook. Each of the production cycles
will have specific production characteristics that can be matched
to the end use of the heat energy.
[0032] One method of heat production from this type of engineered
reservoir is accomplished by the development and production of one
or more independently and separated joint system groups through the
coordinated cycling of a set of the separated rock joint groups
oriented vertically or horizontally to each other such that there
is a continuous production of thermal energy from the reservoir
group for direct use applications as well as peak load following
capacity for such end uses as the generation of electricity.
[0033] Another method of heat production from this type of
engineered reservoir is accomplished by the development and
production of a single jointed reservoir with two or more wells in
which the injection well(s) inject periodically or continuously at
different injection rates so that the rate is greater than the
continuous production rate produced from the, production well(s)
such that the reservoir is alternately expanded and then allowed to
contract, in order to generate the combined thermal and mechanical
stresses necessary to generate in situ reservoir brecciation, while
the reservoir is being produced at a continuous rate, either steady
state or load following state, from the production well bore. The
principle in this case is the operation of single reservoir in a
manner that alternately charges the reservoir at a greater rate
than the production rate in order to expand the reservoir and then
reducing or terminating the injection cycle to allow the reservoir
to contract in order to produce the reservoir from the reservoirs
stored energy. This type of pressure cycling still provides the
benefits of coincidental thermal and mechanical brecciation as
heretofore described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] A more complete understanding of the method and apparatus of
the present invention may be obtained by reference to the following
Detailed Description when taken in conjunction with the
accompanying Drawings wherein:
[0035] FIG. 1 depicts a simplified general schematic view of a
prior art point to point directionally specific pressure sink type
closed loop circulation system designed to draw heat from the rock
formations;
[0036] FIG. 2 depicts an improved version of a prior art fractured
rock closed loop circulation system that is being experimented with
in modern developments such as the commercial hot dry rock attempt
being made by Geodynamics Limited of Australia; and
[0037] FIG. 3 depicts a general schematic of one embodiment of the
HDR production system of this invention and its initial operation
cycle.
[0038] FIG. 4 depicts a general schematic of a second embodiment of
the HDR production system of this invention to generate geothermal
heat energy.
[0039] FIG. 5 depicts a general schematic of a third embodiment of
the HDR production system of this invention utilizing geothermal
heat energy to process organic carbon under supercritical
conditions;
[0040] FIG. 6 is a diagrammatic illustration of the principal
components necessary to drill a geothermal well bore utilizing PJD
methodology;
[0041] FIG. 7 is a diagrammatic schematic of a wellhead and
drilling system illustrating the utilization of multiple types of
drilling methodology in exposing hot dry rock for developing
geothermal reservoirs; and
[0042] FIG. 8 is a flow chart illustrating one embodiment of the
principles of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0043] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
constructed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art.
[0044] The present invention is based on the development of a
discrete system of dilatable fractures in hot rock formations and
the subsequent extraction of heat from the hot rock by means of
elastically cycling the "inflation" and "deflation" of the
reservoir by injecting and recovering an injection fluid such as
water. The joints in the rocks open as the reservoir pressure
increases due to injecting water into the well bore. The joints in
the rock close as the reservoir pressure is decreased due to
production of the injection water which has been heated by the
reservoir rock. This water can be pumped into the reservoir to be
stored and can be withdrawn when water is needed or its production
timed to produce in conjunction with other dilatable fracture
systems to produce a net continuous flow of produced hot water.
[0045] FIG. 1 depicts an apparatus that has been experimented with
by Los Almos National Laboratories to produce hot water from hot
rock formations in which the injection fluid, water in this case,
was circulated in a continuous closed loop manner. A well bore 20
was drilled from the earth's surface 1 through overlying
sedimentary type formations 2 and impermeable crystalline
Pre-Cambrian rock formation 10. Cool water 75 was pumped into the
cased well bore 20 to dilate the natural joints in the Pre-Cambrian
formation to form a network or cloud of interconnected fractures or
joints in geothermal reservoir 15. Due to formation stresses of the
Pre-Cambrian rock, the reservoir of interconnected fractures is
normally elliptical or oblong in shape and may be oriented either
horizontally, vertically, or any degree in-between. A second well
bore 70 is drilled and cased into the geothermal reservoir 15 in
order to create a point to point directionally specific pressure
sink type closed loop circulation subsurface system that would
provide a pathway to the surface for producing the geothermal
heated fluid 80 from the reservoir. Once the reservoir has been
generated and the well(s) drilled and cased, surface based
equipment is added to create a closed loop circulation system.
Wellhead(s) 30 and 65 are installed onto the well bore casing and a
heat exchanger 45 is installed to capture the mined heat.
Appropriate flow line piping, control valves 60 and pumps 35 are
installed. The well can then be circulated by injecting cooled
water 75 by means of pump 35 through well bore 20, exiting well
bore 20 into the geothermal reservoir 15 in the direction as shown
by arrow 25. The water passes through the reservoir in a point to
point directionally specific flow path created by the hydraulic
pressure sink of production well bore 70 and enters the production
well bore 70 as shown by the arrow identifying geothermal heated
fluid 85 and is thereby heated. The geothermal heated fluid 80 then
returns to the surface through well bore 70 and wellhead apparatus
65. The heated water flows through control valve 60, which is used
to maintain adequate back pressure on the production well bore to
maintain the dilated fracture joints open sufficiently to minimize
flow impedance between the well bores. The heated water proceeds
through heat exchanger 45 where the water is cooled by an exchange
of heat to a second fluid being flowed through lines 40 to line 50.
The cooled water is re-injected down well bore twenty by means of
pump 35. This arrangement provides means to flow water through the
geothermal reservoir 15 from the injection well bore 20 to the
production well bore 70 in what is considered generally as a point
to point circuit by means of a pressure differential between the
well bores. This type of arrangement does not allow the use of the
large amount of heated water stored in the dilated joints that are
not flowed through due to becoming pressure isolated between the
two well bores. As the geothermal reservoir 15 reacts to the long
term dilation pressure, the geothermal reservoir 15 tends to
establish pressure equilibrium and therefore grows by enlarging
itself until pressure and thermal equilibrium is reached. This
process could require the continuous addition of large quantities
of make up water which would be injected into the cooled water flow
line at point 55 but normally isolated from the production cycle
due to pressure isolation as described above. This type of water
loss provides a significant disadvantage to the widespread use of
this form of HDR completion and production.
[0046] The above described system suffers from high flow impedance
during the circulating of water through geothermal reservoir 15.
Attempts to increase production through increased injection
pressure produces greater pressure stimulation of the geothermal
reservoir 15 causing further reservoir equilibrium related
expansion with the resultant loss of additional water to the
pressure isolation described above. Therefore, economic flow rates
can only be achieved in this system through drilling multiple wells
to provide additive flow in the ends of the geothermal reservoir
15. The over-all system economics is very sensitive to the total
cost of the well bores. Therefore, in attempts to minimize the
drilling cost, the development of multiple wells and multiple
fracture cloud reservoirs is illustrated in FIG. 2.
[0047] FIG. 2 illustrates injection well bore 70 and producing
wells 71 and 72 being drilled from the earth's surface through
overlying sedimentary formations 2 and Pre-Cambrian rock formation
10. Well bore 70 is used as the development well to hydraulically
generate separate fracture cloud lens 16,17 and 18. The method used
to generate these wells is to run and cement a casing string just
above the bottom of the well bore. The lower uncased section of the
well bore would be hydraulically pressured to induce facture/joint
dilation. This lower section would then be hydraulically isolated
by filling the lower section with sand to some pre-determined
height or a down hole packer set. The well would then be perforated
above the sand pack/down hole packer isolation height and the well
hydraulically pressured to induce a second discrete fracture cloud
at some vertical distance above the lower fracture cloud. Normally
these fracture clouds would be oriented vertically up to vertical
heights in excess of 3,000 ft. Due to the non-linear increase in
drilling cost in Pre-Cambrian rock as a well is deepened, it is
likely that only one or two lenses can be economically developed
with the economic limits of the depth that can be achieved with
normal drilling processes. Once the repetitive cycle of developing
the intended number of vertically spaced facture cloud systems has
been completed, the sand pack intended to hydraulically isolate
lower well bore sections can be removed by direct circulation to
clean out the sand plugs and expose the lower fracture clouds to
the injection well bore pressure and flow during production
operations. In combination, injection well bore 70 and production
well bores 71 and 72 develop a point to point directionally
specific flow path created by the hydraulic pressure sink of
production wells in a closed loop circuit system that can generate
a cumulative flow rate that may produce commercial volumes of hot
water or steam. A similar control and heat recovery system as that
used in FIG. 1 can be used in the system of FIG. 2.
[0048] FIG. 3 depicts one embodiment of the completion scheme and
production method of this invention in order to produce heat energy
for use in direct and indirect use applications such as producing
bitumen and the generation of electricity. Wells 320, 325 and 330
are drilled from the earth's surface 1 through any sedimentary
formations 2 overlying the Precambrian rock formation 10, into the
Precambrian rock formation 10 to a depth of sufficient temperature
and to allow the development of one or more discrete formation
fracture joint clouds 300, 305, 310 which are oriented vertically
or horizontally, as determined by the rock formation predominant
stress fields, in respect to one another. The deepest well 320, in
the case of vertical orientation of the formation fracture clouds,
may need to be drilled to a depth greater than 30,000 feet
(depending on the thermal gradient of the formation and the
required temperature for the end user of the geothermal heat) in
order to reach sufficiently high bottom-hole rock temperatures to
allow the development of one or more reservoirs above the
bottom-hole reservoir. If the facture cloud develops vertically due
to the least principle stress being positioned in the vertical
position, then each fracture cloud reservoir will need to be
separated in the order of 5,000 feet. The second deepest well 325,
in this case, would need to be drilled and cased to a depth of
25,000 feet and the third well 330 would need to be drilled and
cased to a depth of 20,000 feet. The lowermost portion of each well
could be hydraulically fractured to produce a reservoir volume of
dilated joints in the formation by pumping at pressures in excess
of the joint dilation pressure and the formation break down
pressure, which is estimated in the order of 1.0 psi/foot depth.
The well bore would then be useable for the pressurization cycle to
charge the reservoir followed by the depressurization of the
reservoir to flush the heated water from the dilated joints and
produce the heat absorbed by the water during the pressurization
and depressurization cycle. The same well bore completion process,
would be repeated in each of the other two shallower wells in order
to develop an aggregate of three discrete reservoirs that would
accept pressured water to charge the reservoir through dilating the
joints allowing the water to travel into the reservoir, be heated
and then expelled from the reservoir when the water pressure is
lowered in the well bore. Absorbed heat could be continuously
produced by timing the pressure cycling of the well bore to provide
one well being injected into at twice the rate that the well is
reverse flowed. By offsetting the timing of the flow back cycle of
these wells, it is possible to provide continuous, high flow rate
production from this arrangement of reservoirs. A similar process
would be necessary to develop reservoirs that are horizontally
spaced with the reservoirs in either the vertical or the horizontal
orientation.
[0049] FIG. 3 shows the necessary configuration to produce
continuous high flow heated water flow from three discrete
reservoirs separated vertically from each other. Pre-charge pump
360 supplies cooled water from surface reservoir pit 350 to
injection pump 385. Injection pump 385 forces cooled water under
high pressure and volume into one of the three Hot Dry Rock (HDR)
reservoirs. Injection pump 385 is sized to be able to fully charge
a single reservoir at a rate that is equal to the discharge rate of
flushing the heated water from the other two HDR reservoirs. In
this manner a three well production scheme could provide two wells
producing at half the injection rate thereby providing continuous
flow by matching the injection and production rate between the
three well bores. The wells are managed by alternately opening and
closing discharge control vales 410, 405, 400 and injection control
valves 390, 415, 420 to provide the proper sequence each 24 hours.
The high volume heated water is brought to the surface by the
pressure energy stored in the rock during the charging cycle. The
heated water is then conducted through a heat exchanger 45 where
the heat is transferred from the well discharge flow by means of
flowing a second fluid through the heat exchanger lines 40 to 50.
The cooled well bore fluid is routed back down the well bore
through control valve 370 to injection pump 385. Alternately, the
cooled well bore fluid can be discharged from the heat exchanger to
the surface reservoir pit 350 by means of line 380 and line 365 on
opposite sides of choke valve 375 which controls the system
back-pressure. The surface reservoir pit 350 would be used to store
any reserve water necessary to provide make-up water as the
reservoirs mature.
[0050] FIG. 4 depicts another embodiment of the completion scheme
and production method of this invention in order to produce heat
energy for use in direct and indirect use applications such as
producing bitumen and the generation of electricity. Well 70 would
drilled and cased from the earth's surface 1 through any
sedimentary formations 2 overlying the Pre-Cambrian rock formation
10, into the Pre-Cambrian rock formation 10 to a depth of
sufficient temperature to allow the development of a discrete
formation fracture joint clouds which are oriented vertically or
horizontally, as determined by the rock formation predominant
stress fields, in respect to one another. The geothermal reservoir
15 would be hydraulically fractured to produce a desired reservoir
volume of dilated joints in the formation by pumping a liquid at
pressures in excess of the joint dilation pressure and the
formation break down pressure, which is estimated in the order of
1.0 psi/foot of depth. Additional wells 68, 69 and 20 would be
drilled and cased into geothermal reservoir 15 at some predetermine
distance from the production well 70. The preferred embodiment
would use two wells 70 and 68. FIG. 4 illustrates the use of an
additional well 69 as an injection well to illustrate the
flexibility of the engineered nature of the present invention in
order to reduce parasitic pressure losses in the injection wells.
Further additional production wells may be desirable to reduce the
parasitic pressure losses in the production well(s). The wells 68,
69 and 20 would act as injection wells in order to pressurize the
geothermal reservoir 15. Additional fracturing of the geothermal
reservoir 15 may be desirable to increase the productive volume of
geothermal reservoir 15 once the injection wells 68, 69 and 20 have
been drilled, cased and hydraulic communication has been
established with production well 70. The production well 70 would
be utilized to produce injected fluids at a rate commensurate with
the end use. This production rate could be a) a steady production
rate, b) a steady production rate with periodic increases and/or
decreases to accommodate load following needs of the end use and/or
c) a periodic stop and start flow rate tuned to the end use
requirements. The injection wells 68, 69 and 20 are intended to
inject at a higher injection rate than is being produced in the
production well 70 until the maximum elastic energy of the
geothermal reservoir 15 is reached. The injection flow will then be
cut back or terminated in order allow the stored elastic strain in
the geothermal reservoir 15 be relieved by deflating the reservoir
and producing the heated water contained in the geothermal
reservoir 15. The pressure level in geothermal reservoir 15 will be
allowed to be reduced through the relaxation of the geothermal
reservoir 15 stored elastic strain to a predetermined level
sufficient to maintain the dilation of the joints in the geothermal
reservoir 15. Once this predetermined level of relaxed elastic
strain has been relieved to the predetermined level, the injection
of fluid will begin or increase as the case may be. This method of
repeated dilation and deflation of the geothermal reservoir 15 will
produce a) omni-directional flow of the injection fluid setting up
conditions that allow the production of the injection fluid from
omni-directional flow paths towards the production well, b) produce
the simultaneous and/or periodically alternating thermal and
mechanical cycling in order to produce brecciation or spallation of
the joint surface areas producing newly exposed high thermal
differential surfaces that can be swept of their heat, c) the
arrangement of the injection wells to the production wells is
intended to provide a secondary convectional sweeping of heat as
the fluid circulates through the geothermal reservoir 15 as well as
the primary conduction sweeping of heat from the surface of the
dilated joints and d) the arrangement of the injection wells to the
production wells is intended to minimize thermal depletion near the
production well by remotely injecting the working fluid forcing it
through both conduction and convection type flows. The geothermal
reservoir 15 would be useable for the pressurization cycle to
charge the geothermal reservoir 15 followed by the depressurization
of the geothermal reservoir 15 to flush the heated water from the
dilated joints and produce the heat absorbed by the water during
the pressurization and depressurization cycle.
[0051] FIG. 5 depicts another embodiment of the completion scheme
and production method of this invention in order to produce and
utilize geothermal heat energy for use in the processing of organic
carbon under supercritical fluid conditions. The basic steps of
processing organic carbon under supercritical conditions is well
documented in the public domain. Exemplary are the descriptions
provided by Modell in U.S. Pat. No. 4,113,446 issued Sep. 12, 1978,
titled: Gasification Process and further in U.S. Pat. No. 4,338,199
issued Jul. 06, 1982, titled: Processing Methods for the Oxidation
of Organics in Supercritical Water. Titmus and others have describe
the use of deep cased well bores as pressure containment vessels in
various configurations in order to continuously process chemical
reactions by using the various tubular configurations within the
well bores as pressure containment vessels and utilizing the
natural hydrostatic head gradient within the well bore as a means
to conveniently inject feedstock and recover product. Titmus
describes in U.S. Pat. No. 3,853,759 issued Dec. 14, 1974, titled:
Dynamic Hydraulic Column Activation Method the method of using deep
well bores as reaction vessel for continuous processing of various
chemical reactions. Titmus further describes the use of deep well
bores for the purpose of reacting continuous chemical processes
under supercritical water conditions in U.S. Pat. No. 4,594,164,
issued Jun. 10, 1986 and further in U.S. Pat. No. 4,792,408, issued
Dec. 20, 1988. The descriptions of Modell and Titmus require a
chemical, electrical or fuel based process to initiate and then
maintain the elevated internal temperatures within the pressure
vessel reactor sections at temperatures necessary to promote
supercritical water conditions. In Modell's description, the
requisite supercritical water condition pressure is generated by a
pumping means and in Titum's description; the requisite
supercritical water condition pressure is achieved by the
assistance of the natural hydrostatic head of the well bore. The
present invention combines certain understandings and aspects of
the teachings of Modell and Titmus and further adds the aspect of
providing an integrated geothermal heat production system to
initiate and sustain chemical processes under supercritical fluid
conditions through the use of a pressure vessel reactor system
installed within the production well of a geothermal heat
production system as generally described in the description of FIG.
4.
[0052] The embodiment of FIG. 5 builds on the embodiment of FIG. 4
with the additional step of inserting a tubular reactor vessel 73
into the cased well bore 70 through wellhead 64 modified to accept
said the tubular reactor vessel 73. In principle, the geothermal
reservoir 15 is located in an HDR formation that provides the
ability to produce a supercritical fluid which is preferably water.
The geothermal production system is set up to circulate
continuously according to the description of FIG. 4, and will be
mined for its heat content for a) heating the reactor vessel to
promote a continuous chemical reaction within the reactor vessel,
b) providing heat to generate useful work at the surface such as
generating electricity by means of circulating the geothermal water
produced from said geothermal reservoir 15 to the surface where it
can be used and 3) preheat the organic feed stock as described
hereinafter.
[0053] The embodiment of the invention shown in FIG. 4 is modified
in the embodiment of FIG. 5 only in that the geothermal reservoir
15 is developed at such a depth as to produce geothermal fluid
temperatures in excess of 375.degree. C. and preferable above
450.degree. C. The produced geothermal heated fluids 85 and 86 is
flowed around a reactor vessel 73 placed concentrically within
cased well bore 70 to the surface. The produced geothermal heated
fluids 85, 86, 80 and 81 conducts heat into reactor vessel 73 in
order to heat heterogeneous organic carbon slurry 761, 760, 770 and
771 to a temperature above 375.degree. C. The produced geothermal
heated fluids 80 and 81 are passed through wellhead 64, through
control valve 750, through line 690 and into heat exchanger 45
where the geothermal working fluid is expanded and then condensed
to remove the bulk of its heat. The condensed geothermal liquid is
then flowed from heat exchanger 45 through line 590 where it is
combined with effluent from the reactor vessel where the combined
fluids are circulated through heat exchanger 605 to provide heat
energy to preheat the heterogeneous organic carbon slurry as herein
after described.
[0054] A heterogeneous organic carbon slurry is formed within
mixing processor 530 by combining water from water reservoir 200
pumped by pump 500 to mixing processor 530 through supply line 220
and 550 and organic carbon material and appropriate catalysts or
retarders sourced from stockpile 570 through line 560. The
heterogeneous organic carbon slurry is then pumped by pump 600
through line 580 and through heat exchanger 605 where the
heterogeneous slurry is preheated by the final enthalpy transfer of
the produced geothermal heated fluid 80. The heterogeneous organic
carbon slurry flows through line 610 from heat exchanger 605 and
into reactor vessel annulus space through wellhead 730. The
heterogeneous organic carbon slurry is thereby pumped down the
annular space between the concentric walls of reactor vessels 73
and where it is heated above supercritical water temperature by the
action of the geothermal heated fluids 80, 81, 85 and 86 produced
from geothermal reservoir 15. As the heterogeneous organic carbon
slurry is pumped down the reactor vessel annulus, it is subjected
to pressures greater that supercritical water pressures at which
point the heterogeneous organic carbon slurry reacts and forms a
single phase fluid with some non-organic precipitates The length of
the reactor vessel flow path is such that the dwell time of the
organic material under supercritical water conditions provides
sufficient circulation time to exceed the necessary reaction time
for the disassociation of the organic material into its elemental
constituents. The fluid is flowed or pumped around the end of
reactor vessel 800 into the interior of reactor vessel 800 through
chamber 773 where the produced fluid 741 and 740 is returned to the
surface and through wellhead 720. The produced fluid 741 and 740
heat the descending heterogeneous organic carbon slurry as they
pass the common tubular wall of reactor vessel 800. The produced
fluid 740 passes through wellhead 720 and into particulate
separator 620, where the inorganic process product particulate is
separated from the liquid stream and where the solid particulate is
passed through line 710 to solid particulate storage container 700.
The clarified produced fluid then passes through flow line 660
through control valve 650 to gas separator 640 where the clarified
produced fluid is processed to allow the gases to be separated from
the liquid component of the clarified produced fluid. The gasses
are drawn off through line 670 and further separated into their
various species in gas classifier 680 and are subsequently removed
for further processing. The heat energy available from the
clarified produced fluid is recovered in heat exchanger 45 to
produce useful heat energy. The fluid then flows from heat
exchanger 45 into line 590 where it is commingled with the fluid
resulting from the heat exchange process of the produced geothermal
heated fluids 80 and 81. The commingled effluents from heat
exchanger 45 are conducted to heat exchanger 605 where any residual
heat is further exchanged as a preheat process for the
heterogeneous organic carbon slurry being flowed through heat
exchanger 605. From heat exchanger 605 the effluent fluid is flowed
through line 540, through control valve 520 and through line 510 to
be discharged into water reservoir 200.
[0055] The embodiment in FIG. 5 provides a method of utilizing
geothermal heat energy contained in produced geothermal fluids that
are above 375.degree. C. to initiate and or maintain a continuous
or periodic supercritical reaction in a reactor vessel immersed
within said geothermal production well.
[0056] FIG. 6 illustrates the principle components necessary to
drill a geothermal well bore utilizing a PJD methods of drilling
the well. It is common knowledge that drilling large diameter deep
well bores in Precambrian rock is prohibitively expensive with
commonly practiced rotary mechanical earthen formation drilling
practices. The slow rate of penetration associated with the
rotary-mechanical drilling systems has been the principle cause of
the huge potential of the HDR geothermal energy resource to
languish. The use of PJD techniques and methods provides a means to
increase the rate of penetration in all formations and particularly
the crystalline rocks sufficiently to reduce the time and cost to a
level that will provide the potential for widespread use of
geothermal energy.
[0057] The experimental use of PJARMD intended for drilling oil and
gas wells has been well documented by the oil and gas industry. The
experimental use of high mass particles entrained in drilling
fluids was demonstrated by Gulf Oil Company in the early 1969's
based, on U.S. Pat. No. 3,348,189, issued May 21, 1968 and the more
recent use of larger diameter high mass particles entrained in the
drilling fluid has been patented by the inventor as U.S. Pat. No.
6,386,300 issued May 14, 2002. The referenced methods of drilling
with jetted particles embodies the process of entraining discrete
high density solid particles into the drilling fluid circulated
during the drilling operation in order to jet impinge the particle
laden slurry against the formation thereby cutting the formation
through the impulse energy imparted to the rock by the momentum
transmitted from the action of the high mass particles. Both the
PJARMD and HPJD processes have been successfully demonstrated in
lab tests to increase the drilling rate of penetration in various
earthen formations. Certain experimental field tests have been
conducted in sedimentary type formations. Heretofore, PJARMD has
been developed and or tested for the commercial purpose of drilling
sedimentary formations that hold oil and gas reserves. These
sedimentary formations are generally found above Precambrian rock
formations. Sedimentary formations are comprised of stratified
shale, sandstone and limestone and or their metamorphosed material.
Drilling sedimentary formations with PJARMD techniques involves the
use of a rotary-mechanical drill bit that is assisted by the use of
jetted particle. PJARMD requires careful balance of the slurry
fluid properties and operating parameters. The Effective
Circulating Density (BCD) of the drilling slurry fluid containing
high mass particles must be maintained carefully so as not to break
down any sedimentary formations such as shale, sandstone or
limestone. The need to carefully control the BCD in sedimentary
formations is expected to have a significant limiting factor in
widespread use of PJD as a means for drilling oil and gas wells in
sedimentary formations due to the potential chronic and problematic
formation breakdown know as loss circulation conditions. Secondly,
the use of PJARMD methods is better suited to the relatively
smaller well bore diameters use in oil and gas production.
[0058] The use of HPJD techniques for drilling Precambrian rocks at
great depth is essential for economic development of deep HDR
geothermal resources. HPJD can be utilized in competent well bore
formations where BCD is not a controlling factor. Formations such
as the crystalline Precambrian and Hadean formations lend
themselves well to minimized BCD effects thereby allowing full use
of HPJD without the need to rotary mechanical drilling assistance.
FIG. 6 illustrates one method of drilling a deep well bore
terminating in crystalline rock for the purpose generating a HDR
geothermal reservoir. The general geometry illustrates the
sedimentary rock formations 870, 860 and 850 which typically
overlay the Precambrian rock formations 840. The sedimentary
formations 870, 860 and 850 are generally stratified formations of
different sedimentary rock material such as shale, sandstone and
limestone. These formations can be drilled by either normal
rotary-mechanical or PJARMD means as is appropriate for the
sedimentary section make-up and thickness. The sedimentary section
of the well bore 880 will be isolated from the deeper well bore 920
by means of a casing tubular 890 which is typically cemented in
place by cement sheath 900. Drill pipe 910 which is manipulated by
a drilling rig (not shown) provides the conduit and tubular
connection to the HPJD drill bit 810. HPJD drill bit 810 provides
the means to jet impinge the high mass particles 830 accelerated
within the typical PJD drill bit nozzle jet flow 820 onto the
Precambrian rock formations in order to rapidly drill said
formations. The novelty of drilling through and isolating the
sedimentary formation in order to expose only the crystalline
Precambrian formation for drilling by means of HPJD methods
provides the ability to utilize optimum HPJD operating conditions
to maximize the rate of penetration while drilling said Precambrian
formations that are not available while drilling sedimentary
formations. The use of low viscosity fluids for HPJD particle
entrainment, transportation, impingement and return circulation
duties are thus available for drilling in Precambrian formation as
there is no need to significantly consider BCD properties due to
the integrity of the Precambrian formation as opposed to the lack
of integrity of integrity of well bore exposed sedimentary
formations. The use of very high PJD fluid flow rates can also be
used while drilling Precambrian formations as there is no need to
significantly consider drilling fluid formation erosion again due
to the integrity of the Precambrian formations.
[0059] The use of PJD methods for reducing the cost of drilling
well bores terminating in Precambrian or Hadean formations is
fundamental to the widespread development of the HDR potential.
Specifically, PJD provides a means to economically drill large
diameter, very deep injection and production well bores for HDR
production purposes. The specific well bore geometry, used in
conjunction with PJD techniques, is unique to producing the
environment to operate the PJD techniques at optimal levels for
rate of penetration performance purposes.
[0060] Referring now to FIG. 7, there is shown a diagrammatic
schematic illustration of the drilling of a well bore within a
plurality of earthen formations. At the wellhead 400 represented by
the diagrammatic illustration of a derrick, a first earthen
formation 404 is penetrated by well bore 402. The type of drill bit
utilized in this particular formation may be a mechanical drill bit
conventional for shallow wells and/or the PJARMD referenced herein.
Diagrammatically represented in lower earthen formation 406 is a
drill bit 414 which may be the same as and/or similar to the drill
bit 412 but may vary in accordance with the principles of the
present invention depending on the type of earthen structure found
in earthen section 406. Likewise, earthen section 408 is a
continuation of the well bore 402 and illustrates,
diagrammatically, a drill bit 416 which may be of a different
methodology in accordance with the principles of the present
invention, depending on the type of structure engaged in earthen
formation 408. Finally, earthen formation 410 is diagrammatically
represented as a Precambrian and/or Hadean crystalline rock wherein
the cross-sectional profile thereof is varied and the bore hole
section 430 is shown penetrated by an hydraulic drilling
methodology found in the drilling tool 418 which may incorporate
particle jet drilling in accordance with the principles of the
present invention for penetrating the Precambrian or Hadean,
crystalline rock formation for accessing the thermal energy therein
and establishing a site within the bore hole for subsequent
hydraulic fracturing and the charging and discharging described
above in accordance with the principles of the present
invention.
[0061] Referring now to FIG. 8 there is shown a flow diagram of one
embodiment of the principles of the present invention. In this
particular flow diagram, the methodology described above is clearly
set forth and shown wherein step 501 includes the establishment of
a bore hole drilling system in accordance with the principles of
the present invention. Step 503 illustrates the drilling of a first
bore hole section with a PJARMD methodology. This methodology may
change depending upon the particular type of the earthen formation
as illustrated in FIG. 7.
[0062] Still referring to FIG. 8, the step 505 represents the bore
hole reaching the Precambrian or Hadean crystalline rock formation
where the type of drill bit being used may vary in accordance with
the principles of the present invention. Step 507 illustrates
drilling a second, lower bore hole section through the Precambrian
or Hadean crystalline rock formation with hydraulic drilling
methodology. One form of the HPJD methodology set forth and
described in the present invention is particle jet drilling. Step
509 illustrates the hydraulically fracturing of the hot dry rock
(HDR) to produce a fracture cloud of dilated joints. Step 511
illustrates the step of charging and discharging the fracture cloud
in accordance with one embodiment of the principles of the present
invention. Step 513 illustrates producing thermal energy from the
fracture cloud in accordance with the principles of the present
invention as described above.
[0063] In summary, the above-referenced description has described
and shown the following inventive aspects of the present
invention:
[0064] 1) The use of HPJD for drilling well bores that terminate in
a) non-sedimentary formations or b) Precambrian formations or
Hadean formations for the purpose of developing hot dry rock
geothermal resources.
[0065] 2) The method of drilling and isolating sedimentary
formations, with or without PJD methods for the purpose of drilling
underlying crystalline, non-sedimentary, Precambrian or Hadean
formations with PJD techniques.
[0066] 3) The use of non-rotary-mechanical means to drill well
bores that terminate in a) non-sedimentary formations or b)
Precambrian formations or Hadean formations for the purpose of
developing hot dry rock geothermal resources.
[0067] 4) The use of non-mechanical drill bit means to drill well
bores that terminate in a) non-sedimentary formations or b)
Precambrian formations or Hadean formations for the purpose of
developing hot dry rock geothermal resources.
[0068] 5) The use of low viscosity or Newtonian drilling fluid in
conjunction with PJD for drilling drill well bores that terminate
in a) non-sedimentary formations or b) Precambrian formations or
Hadean formations for the purpose of developing hot dry rock
geothermal resources.
[0069] 6) The use of PJD fluid flow rates equal to or greater than
500 gallons per minute to drill well bores that terminate in a)
non-sedimentary formations or b) Precambrian formations or Hadean
formations for the purpose of developing hot dry rock geothermal
resources.
[0070] 7) The use of non-standard drill pipe to drill well bores
that terminate in a) non-sedimentary formations or b) Precambrian
formations or Hadean formations for the purpose of developing hot
dry rock geothermal resources.
[0071] 8) Using PJD methods to drill well bores that are 9.00'' or
greater in diameter that terminate in a) non sedimentary formations
or b) Precambrian formations or Hadean formations for the purpose
of developing hot dry rock geothermal resources.
[0072] Using PJD methods to drill well bores that are 5,000 feet
deep or greater that terminate in a) non-sedimentary formations or
b) Precambrian formations or Hadean formations for the purpose of
developing hot dry rock geothermal resources.
[0073] The following concepts are thus contemplated to be within
the spirit and scope of the present invention:
[0074] 1) hi generating the HDR reservoirs, the conventional
thought is to continuously circulate the between two or more wells
through flow paths in the induced rock fractures or dilate natural
occurring rock joints in the HDR reservoir. This "hydraulic
short-circuiting" or point to point flow is both limiting in its
capacity to 1) absorb heat, 2) suffer from high flow impedance, and
3) hydraulically isolate the bulk of the fluids contained in the
fracture cloud reservoir. The method of this invention provides
elastic cycling of the charging and discharging of a reservoir
which provides full use of the reservoir fracture system through
omni-directional flow in the charging process and omni-directional
flow reverse flow during the reservoir relaxation process. Further,
the waters ability to absorb heat is a function of its dwell time
when in contact with the surface area of the reservoir. This method
provides relatively longer dwell times as the water has to first be
swept into the rock joints and then swept out of the rock joint
sequentially during the formation charging and relaxation cycle.
Further, the omni-directional flow provides a vastly increased
surface area for the water to be heated from during each cycle when
compared to conventional HDR completion systems. This double pass
flow regime will provide significantly improved heat transfer to
the produced water.
[0075] 2) The use of cyclical stress reversals, both mechanical and
thermal will provide for significant rock surface breakdown over
time due to these combined cyclical stress reversals. By breaking
down the reservoir rock into relatively small blocks or rock chunks
or pieces of rock through shear banding brecciation or spallation,
the reservoir surface area and reservoir volume are increased,
providing an increasing area from which to draw heat as the
omni-directional fluid paths sweep the "hydraulic container"
surface area. The brecciated rock is hydraulically isolated once it
has broken free of the fracture surface. Gravity will pull the
spalled rock to the lower most regions of the reservoir where it
will be pulverized over time through the action of the mechanical
cycling of the reservoir rock. There are two thermal mechanisms to
draw heat from during conduction in this setting, the near field
and far field heat conduction. The near field heat is transferred
by conduction very quickly due to the high temperature
differentials between the rock and the sweeping fluid. Once this
near field heat is drawn to a lower threshold, further heat
transmission is governed by the rock medium diffusivity values. By
far the greatest heat sweeping effects are gained by the continuous
exposure of the injection fluid to the next "hydraulic container"
surface due to cyclical related shear banding brecciation. It is
expected that the shear banding brecciation will continually
produce a new contact surface to interact with the injection fluid
before the high heat levels of the near field region have been
reduced to a level that triggers far field heat diffusivity to act
upon the reservoir wall thus reducing the heat transfer rate. The
described action provides a near-continuous refreshing of the high
temperature differentials available for near field conductive heat
sweeping over time. This is opposed to the conventional HDR systems
that must rely on far field heat diffusivity of the far field rock
massif once the near field heat has been conductively swept which
has the effect of significantly lowering the total heat output and
the production temperature over time. Therefore the ability to
generate a new surface area in an expanding reservoir is the key to
sustaining the near field type conduction values. As the rock
reacts to the thermal and mechanical stresses of repeated cycling
during production, new surface area is generated as the rock
contracts as the effects of thermal change as well coincidental
mechanical displacement act upon the interior rock surface of the
reservoirs "hydraulic container."
[0076] 3) The reservoir can be enlarged through additional fraccing
above the fracture dilation pressures in order to extend or
generate a larger base reservoir. This would serve the purpose of
increasing the base reservoir size, growing the base reservoir more
rapidly than it would with just the cyclical action of the charging
and discharging cycles, to compensate for maintaining temperature
in the reservoir if necessary.
[0077] 4) This method of geothermal production produces a far
greater production rate and ultimate recovery potential than any
other method currently being utilized due to the increased surface
area sweeping and new surface exposures over time.
[0078] 5) The use of produced geothermal temperatures above
375.degree. C. to provide heat energy in support of chemical
reactions in a reactor vessel immersed in the geothermal production
well provides the basis of converting large volumes of organic
carbon, such as coal, oil shale, biomass and waste to useable and
marketable products. The produced geothermal heat energy provides
a) the heat energy to initiate or sustain the supercritical water
chemical process within the reactor vessel, b) provides the
residual heat energy to conduct direct and indirect use of the
produced geothermal fluid for such end uses as generating
electricity through binary type power generation plants, and c)
providing further heat yields to preheat the organic carbon
feedstock. The system derives its economic value by generating
clean electrical power and producing clean burning hydrogen while
separating and capturing any harmful byproducts in forms that can
be further processed, disposed of effectively or marketed. The use
of the cyclical geothermal reservoir flexing production method to
provide steady state production from a single reservoir and
providing the benefits of the cyclical injection process to
maintain high thermal production temperatures, flow rates and
reservoir growth supports the ability to use utilize geothermal
production for large scale continuous as opposed to batch
processing of organic carbon such as coal, oil shale, biomass and
waste to produce clean water and marketable products such as H2
methane or Fischer-Tropsch liquids. This system would be useful in
the processing of coal at existing power plants and supplying them
with clean burning fuel gasses to enhance economics and reduce
industrial production of greenhouse gasses. There are currently
approximately 700 coal fired electrical power plants the US alone
that would significantly benefit from this invention. Further, this
invention provides an enabling technology for the large scale
processing of mineable oil shale.
[0079] It is thus believed that the operation and construction of
the present invention will be apparent from the foregoing
description of the preferred embodiments. While the configurations
and designs as shown are described as being preferred, it will be
obvious to a person of ordinary skill in the art that various
changes and modifications may be made therein without departing
from the spirit and scope of the invention, as defined in the
following claims. Therefore, the spirit and the scope of the claims
should not be limited to the description of the preferred
embodiments contained herein.
* * * * *