US3864917A

US3864917A - Geothermal energy system

Info

Publication number: US3864917A
Application number: US021052A
Authority: US
Inventors: Charles H Jacoby
Original assignee: International Salt Co
Current assignee: Akzo Nobel Salt Inc
Priority date: 1970-03-19
Filing date: 1970-03-19
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11

Abstract

The heat conducting capability of a vertically extending dome or spire or vein or other type deposit of a highly heat conductive mineral such as rock salt, is utilized to pipe heat from a deepseated high temperature geologic structure inaccessible to modern bore hole drilling equipment into a heat exchange/conversion reservoir which is developed at an underground level within reach of modern bore hole completion techniques. Energy derived from the heat flowing into the reservoir through the conductive mineral structure from the deep-seated structure is thereupon transmitted to a useful facility, such as any heat-powered system or machine, located either above or below ground. The invention provides a cheap and unlimited ''''clean'''' heat delivery system, entirely free of any air polluting by-products or the like.

Description

United States Patent Jacoby Feb. 11, 1975 1 GEOTHERMAL ENERGY SYSTEM 3552.128 1/1971 Shook 61/.5 24,318 5195 't' c .5 [75] Inventor: Charles H. Jacoby, Dalton, Pa. 7 Pd 6H [73] Assignee: International Salt Company, Clark FORElGN PATENTS OR APPLICATIONS Summit Pa 498,700 5/1930 Germany 159/1 G I 313,257 6/1919 Germany 159/1 G [22] Filed: Mar. 19, 1970 OTHER PUBLICATIONS 1211 P IO-121,052 Scientific American. Oct. 27, 1917, 2 pages.

Science and Mechanics, Oct. 1951, pages 95 thru 97.

[52] US. Cl 60/641, 166/302, 62/260,

165/45, 165/106, 165/132, 61/.5, 299/4, Primary Examiner-Wilbur L. Bascomb 299/5, 159/] G, 23/272 AH, 23/293 R Assistant Examiner-S. .l. Emery [51] Int. Cl. E21b 43/00, B65g 5/00, BOla 1/00 Attorney, Agent, or FirmBean and Bean [58] Field of Search 23/312 AH, 309, 293 R;

159/1 G; 299/4, 5; 60/26; 165/45, 106, .132; 57 ABSTRACT 61/05; 62/260; 166/57 256 The heat conducting capability of a vertically extending dome or spire or vein or other type deposit of a [56] References cued highly heat conductive mineral such as rock salt, is

UNITED STATES PATENTS utilized to pipe heat from a deep-seated high tempera- 1,917,154 7/1933 ture geologic structure inaccessible to modern bore 2,461,449 2/1949 hole drilling equipment into a heat exchange/conver- 215O31456 4/1950 s ion reservoir which is developed at an underground level within reach of modern bore hole completion 3l40'986 751964 techniques. Energy derived from the heat flowing into 3274769 9/l966 the reservoir through the conductive mineral structure 312781234 [0/1966 Helvensmnw from the deep-seated structure is thereupon transmit- 3,348,883 10/1967 Jacoby ted to a useful facility, such as any heat-powered sys- 3,386,768 6/1968 Jacoby tern or machine, located either above or below 3,421,794 l/1969 Jacoby ground. The invention provides a cheap and unlimited 3,432,205 9 Holman" clean heat delivery system, entirely free of any air 3,433,530 3/1967 Holms polluting by pmducts or the like, 3,464,219 9/1969 Closs 3,470,943 10/1969 Van Huisen 159/1 G 3 Claims, 3 Drawing Figures fi fl fl w M i fl l t l I MONlTOR 1 1 1 'n l l 27 1| 1 1 26 29 1 l f 1 2 H ENERGY I PUMP 28E E c w i eE I l fl w w, c fl fl i CAVITY l' HEAT IN PATENTEUFEHI m 3.864.917

SHEET 71 0F 3 MOTHER SALT BED INVENTOR.

CHARLES H. JACOBY ATTORNEYS IPATEHTEDFEB 1191s I 88 4.9 17

sum 20F 3 INVENTOR.

' CHARLES H JACOBY BY @6007 q @401 ATTORNEYS I I l I l I I I PATENTED 1 v 3.854.917

SHEET 3 BF 3 Eli; v zo r l. MON iTOR' 1' 2 7 i f #26 1: 29? 1. ENERGY I PUMP- 28/ E N GE L l CAVITY HEAT IN INVENTOR.

CHARLES H. JACOBY @eam4@eam ATTORNEYS 1 GEOTHERMAL ENERGY SYSTEM- Whereas numerous proposals have been previously made whereby to employ socalled underground heat" to useful purposes, certain practical limitations have invariably minimized the economic importance and/or commercial successes of such efforts. This has been due to such factors as the relatively low and fluctuating temperatures available from hot underground water or steam well sources such as have been suggested for such purposes, as well as their unreliability and depletion-prone characteristics and the expense and difficulties attending attempted bore hole operations through ordinarily encountered formations with a view to reaching such depths as would tap rock structures competent to support a constant and sufficiently high temperature heat abstracting operation. See for example US. Pat. Nos. 2,461,449; 3,140,986; 3,274,769; and 3,363,664. Other suggestions such as involve use of hot volcanic products are similarly inherently infeasible, and in many cases necessarily involve concomitant air pollution problems.

The present invention derives from the discovery that integral structures of certain highly heat conductive minerals such as rock salt and quartzite and the like sometimes occur, although only rarely, in geologic forms such as are known as spines or spires or domes or veins, or the like; and comprise relatively solid masses intruding upwardly towards the earths surface to within reach of modern drilling equipment. These geologic phenomena which may be described as heat conduits" are not only characterized by their relatively high heat conducting characteristics compared to the more ordinarily encountered underground strata, but also exist in thermal continuities at their bases with intensely hot mother beds or other rock masses which occur at extremely higher temperatures and which are also so highly conductive as to be competent to promptly replenish heat which may be withdrawn from the heat conduit structure. These mother beds or the like are however seated at great distances underground, far beyond reach of modern drilling techniques. Thus, the vertically intruding structures referred to are uniquely adapted by virtue of the present invention to function as conduits for the rapid conduction of practically unlimited quantities of heat from the earths core, through the environmental earths crust structural formations which are relatively heatinsulative, to the extent that the intrusions penetrate the latter.

It has been established for example, that by virtue of the present invention a bore hole driven into a Louisiana Gulf Coast salt dome only to a depth of the order of 10,000 feet will tap a substantially unlimited high temperature heat energy supply drawing from sources as deep as 50,000 feet or more. Such results are attainable because of the fact that solid rock salt as well as a few other minerals to be mentioned hereinafter, are quite unique in that they have heat conductivity coefficients many times higher than the coefficients of other geologic structures such as are usually encountered by underground drilling. Reference is made to: Handbook of Physical Constants, published by the Geological Society of America, Revised Ed., Pages 461-466. It will be noted for example from the above referenced 2 heat conductivity tables, that the quartz (quartzite) minerals and hematite are also notably highly heat conductive. Accordingly, it is contemplated that appropri-' ately situated deposits of such minerals may, when occurring in thermal continuity with deeper seated heat supply mother beds or the like, be utilized in accordance with the present invention to provide reservoirs into which suitable heat flow from more deepseated levels at sufficient replacement rates may be at tained for the purposes of the invention.

However, it will be appreciated that quartz and hematite are notoriously hard" minerals and relatively insoluble in water. Therefore, economic considerations may greatly favor the exploitation of spires or domes or other shaped deposits of rock salt for such purposes. Also, it is a fact that rock salt is readily drillable while forming a tight" (solid, fracture-free, and leak-proof) bore hole wall; and that subsequent to drilling to suitable depth in-a rock salt structure a heat exchange cavity of the desired shape and size may be easily and economically formed at the bottom of the bore hole by a simple solution mining technique. The quartz and hematite minerals or the like do not lend themselves as readily to such methods; but in some situations deposits thereof may nevertheless provide suitable agencies for practicing the present invention, depending upon the economic factors involved.

Accordingly, the invention will behereinafter described with emphasis on practice of the invention in connection with a rock salt deposit penetrated by modern bore hole drilling equipment to a suitable depth, and which is thereupon solution mined to provide a cavity of prescribed shape and dimensions in the salt mass for the heat reservoir of the system. The subsequently emptied cavity is then flushed for heat abstraction purposes by circulating a heat exchange fluid therethrough, or by employment of any other heat abstraction or energy conversion mechanism.

It is of particular importance to note that the system contemplated by the present invention preferably employs a heat exchange fluid which does not solubilize the heat cavity wall structure and which is chemically inert thereto, so that the heat cavity will reamin leakproof and constant as to size and shape. Hence, a uniform and regulatable rate of heat extraction and delivery to the surface facility may be maintained. It is to be understood, however, that means other than simple heat exchange fluid circulation systems may be employed to utilize the heat energy so made available at the heat reservoir.

Thus, in accordance with one example of the present invention, a heat spire or heat dome or the like as above described occurring within reach of modern drilling equipment is first located by test drilling or other means, and a heat reservoir is then established in a hot portion of the spire by drilling one or more bore holes from the earths surface into the spire until a level is reached therein at which the desired temperature and heat replacement condition exists. A heat exchange cavity is then formed at the nether end of the bore hole system and established in heat exchange fluid circulation communication (at monitored rates) through the bore holes and/or conduit means extending from aboveground. Thus, for example, a regulated supply of relatively cool fluid may be circulated through the cavity as to become suitably heated therein, and then conducted back up to an aboveground facility for utilization of the heat energy abstracted by the fluid from the environment, through the walls of the reservoir cavity. I

The invention also contemplates automatically controlled circulation of a heat exchange fluid through the bore hole conduit means and heat exchange cavity at such a rate as to obtain delivery of heated fluid uniformly at the desired temperature, to the heat employment facility. Thus, the system will be automatically monitored by temperature and/or flow rate sensors at the output end of the conduit system, controlling velocity of fluid flow through the cavity so as to abstract heat therefrom uniformly and at the desired rate. Also, the invention contemplates that the fluid in the conduit system may be self-moving; the relatively cooler fluid in the down-hole outweighing the relatively hotter fluid in the up-hole. However, in order to positively establish and maintain circulation, a priming pump may be employed and kept on a standby basis and brought automatically into play whenever needed by means of a motor control actuated in response to signals from a rate-of-flow meter in the conduit system.

DETAILED DESCRIPTION Whereas the invention may be applicable to a variety of geological structures as explained hereinabove, it is illustrated and described in detail hereinafter by way of example in conjunction with a sodium chloride rock salt dome such as is known to occur for example in the Louisiana Gulf Coast area of the United States; as will be more fully explained and as is illustrated by the accompanying drawing wherein:

THE DRAWING FIG. 1 is a vertical geoligic sectional view illustrating a typical system installed in a salt dome or spire occurring in the thermal continuity with a mother" salt bed, in accordance with the present invention;

FIG. 2 is a fragmentary enlarged scale view of portions of FIG. 1; illustrating in more detail but schematically, one form of heat abstraction system and one form of aboveground heat utilization system; and

FIG. 3 is a flow diagram of the system illustrated in FIGS. 1, 2.

As illustrated at FIG. 1, in accordance with the present invention, a geological phenomenon such as is known as a salt spire or dome" as indicated at is provided with a heat reservoir cavity 12 by first drilling from an appropriate location at the earths surface a parallel bore hole system as indicated at 16-18. The penetration is conducted to a relatively great depth; say, of the order of 10,000 to 20,000 feet below the earth's surface; whatever may be required to accommodate a heat reservoir as indicated at 12 at a level wherein temperatures such as for example approximating 300F or higher are encountered within a substantial body of solid rock salt such as will be competent to continuously replace the anticipated heat energy abstraction from the reservoir. Because of the solubility characteristics of rock salt, the heat reservoir 12 may be conveniently and economically formed at the desired level in the spire 10 by flowing a stream of water from the surface to the bottom of the bore hole system, and then counterflowing the resultant brine solution upwardly to the earths surface for disposal. A circulation system for this purpose may be established either within a single bore hole by use of concentric casings;

or, alternatively it may be arranged as shown in the drawing herewith by use of

parallel bore holes

16, 18, as explained for example in my earlier US. Pat. Nos. 3,42l,794; 3,348,883; 3,386,768; and Re. 25,682'

It is a particular feature of the present invention that the heat cavity 12 is located within a structurally strong and rigidly solid portion of the geological formation 10 and at such a depth therein as to operate as a heat well for the heat energy which is constantly available for conduction from the earths core, such as by way of the mother bed of salt forming the foundation for the spire 10, as illustrated at FIG. 1. Thus, the cavity 12, after being suitably formed by a solution mining process and then emptied, provides an open heat exchange chamber through which a suitable heat exchange fluid may be circulated. The fluid may comprise any suitable gas 1 or liquid such as will neither dissolve nor react with the mineral forming the wall of the cavity. Circulation may be established such as by pumping the fluid downwardly through the casing 16 so as to displace heated fluid upwardly through the casing 18, for delivery to the heat utilization facility as is illustrated schematically at 20 in the drawing herewith.

It is a particular consideration in connection with the present invention that the heat exchange cavity be engineered in strict accordance with parameters controlling proper operation of the system. These parameters include the temperature encountered at the heat cavity level; the projected mean temperature of the input phase ofthe heat exchange media; and the desired temperature and delivery rate of the output phase of the heat exchange media. The heat replenishment capability of the mineral spire and its mother bed is of course a still further and overriding parameter.

Further by way of example, as illustrated at FIG. 2, a previously specified sized and shaped heat exchange cavity may be engineered by initially driving the bore hole 16 and casing it as illustrated at FIG. 2, while at the same time driving bore hole 18 to a shorter depth such as to the elevation indicated at 22. The bore hole 18 is then inclined so as to continue it in the direction indicated at 24 until its nether end comes into close proximity with the lower end of the casing of borehole l6. Interconnection of the two bore holes is then readily accomplished either by fracturing or solution mining a channel therebetween.

To complete the heat exchange cavity to its prescribed shape and size, the bore hole 18 is cased only to the elevation 22. Thus, it will be understood that as fresh water is pumped downwardly through the casing 16 it will circulate upwardly through the bore hole portion 24 and into the casing of bore hole 18 while simultaneously dissolving salt from the salt body 10 so as to create the cavity 12 in a shape and size such as illustrated in FIG. 2. The bore hole configuration illustrated at 24 (FIG. 2) will of course disappear in the process. The salt dissolution process will be carried on as long as may be necessary to shape the cavity to the desired wall area as previously determined by calculations based upon the temperature and heat exchange data obtained during the bore hole drilling operations.

'As illustrated at FIG. 3, it is further more particularly contemplated that after the heat exchange cavity is properly completed and a heat exchange fluid flow syswill be regulated in its operation so as to displace fluid at a rate consonant with the prescribed requirements of the output media temperature and/or rate of delivery. Accordingly, it will be understood that the monitoring system 27 controlling the operation of the pump 26 will be operable in accordance with the temperature and rate of delivery of the output phase of the medium as sensed by meters as indicated at 28, as the fluid enters the heat exchange apparatus as illustrated at 29. Therefore, it will be understood that a uniform supply of heat at the desired temperature and rate of supply will be furnished the energy exchange device 29 by replenishment of heat from the mother salt bed as illustrated by the arrows 30 (FIG. 1).

I claim:

1. The method of providing a surface facility using heat energy at a predetermined heat flow rate by heat exchange from a fluid heat exchange medium having an initial temperature and flowing at a predetermined fluid flow rate such that the discharge temperature of the heat exchange medium is lowered to a known value, said heat exchange medium being chemically inert to and a non-solvent for sodium chloride salt, which method comprises the steps of:

a. determining the location of a salt dome which extends from a depth accessible by bore drilling techniques to a depth inaccessible by bore drilling techniques and into thermal continuity with a bed of elevated temperature material;

. driving a bore hole into said salt dome to a selected accessible depth of at least about 10,000 feet at which the temperature of the salt is greater than said predetermined initial temperature of the heat exchange medium and at a point within said dome so as to maintain said thermal continuity with said bed of elevated temperature material;

0. solution mining salt at said point within the dome through said bore hole for'a time sufficient to produce, at said selected accessible depth, a cavity having a heat transfer area of that particular size which will elevate the temperature of said heat exchange medium from said discharge temperature to said initial temperature thereof at said ground facility while the medium is introduced into and flows from said cavity at said predetermined fluid flow rate;

d. flushing said cavity through said bore hole with a fluid which will neither react with nor dissolve said salt thereby to terminate the solution mining of step (c) and maintain said particular size of the cavity;

e. circulating said fluid heat transfer medium through said bore hole, into said cavity and back to the ground surface at said predetermined fluid flow rate; and

f. abstracting heat energy from said heat transfer medium fluid at said desired heat flow rate at said surface facility. a

2. The method according to claim 1 including the step of driving a second bore hole substantially to said selected accessible depth and in spaced relation to the bore hole of step (b), and wherein the solution mining of step (c) is effected by passing a solvent for the salt downwardly through the first bore hole and back up the second bore hole.

3. The method according to claim 1 wherein the solution mining of step (c), the flushing of step (d) and the circulation of step (e) all are effected through the same bore hole.

Claims

1. The method of providing a surface facility using heat energy at a predetermined heat flow rate by heat exchange from a fluid heat exchange medium having an initial temperature and flowing at a predetermined fluid flow rate such that the discharge temperature of the heat exchange medium is lowered to a known value, said heat exchange medium being chemically inert to and a non-solvent for sodium chloride salt, which method comprises the steps of: a. determining the location of a salt dome which extends from a depth accessible by bore drilling techniques to a depth inaccessible by bore drilling techniques and into thermal continuity with a bed of elevated temperature material; b. driving a bore hole into said salt dome to a selected accessible depth of at least about 10,000 feet at which the temperature of the salt is greater than said predetermined initial temperature of the heat exchange medium and at a point within said dome so as to maintain said thermal continuity with said bed of elevated temperature material; c. solution mining salt at said point within the dome through said bore hole for a time sufficient to produce, at said selected accessible depth, a cavity having a heat transfer area of that particular size which will elevate the temperature of said heat exchange medium from said discharge temperature to said initial temperature thereof at said ground facility while the medium is introduced into and flows from said cavity at said predetermined fluid flow rate; d. flushing said cavity through said bore hole with a fluid which will neither react with nor dissolve said salt thereby to terminate the solution mining of step (c) and maintain said particular size of the cavity; e. circulating said fluid heat transfer medium through said bore hole, into said cavity and back to the ground surface at said predetermined fluid flow rate; and f. abstracting heat energy from said heat transfer medium fluid at said desired heat flow rate at said surface facility.