What is claimed is
1. A system for producing a material selected from oil, gas, chemicals, minerals, metals and the like from a geological formation including a subsurface stratum containing at least one of said materials overlying a dry, subsurface geothermal zone having an abundant supply of naturally occurring heat and having a naturally occurring temperature substantially greater than said stratum, comprising in combination:
2. A system according to claim 1 further including outlet means containing a valve connected to said casing above the surface for flowing said well at the surface of the earth.
3. A system according to claim 1 further comprising a cement layer surrounding and engaging said plug and the exterior of the casing below the surface of the earth and said layer containing said perforations and an aperture for receiving said pipe.
4. A method for recovering a material selected from oil, gas, minerals, chemicals, metals and the like from a geological formation including a subsurface stratum containing at least one of said materials and a lower, dry, geothermal zone having an abundant reservoir of heat and a natural temperature substantially above the temperature of the stratum comprising the steps of:
5. A method according to claim 4 in which said injected liquid is water.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to the utilization of geothermal heat energy for the recovery of oil, minerals, metals, and chemicals which can be more efficiently mined or produced by coming in contact with increased temperatures and pressures that serve to increase viscosities, create solutions, and enhance recovery.
Brief Summary of the Invention
The present invention relies upon the geothermal zones which exist within the interior depths of the earth and contains vast sources of heat energy resulting from the earth's calorific production which is housed in formations at various depths within the earth. In one of its aspects, the present inventive system provides for the direct utilization of steam or hot liquid contained within the geothermal stratum under sufficient pressures to allow it to enter a perforated or slotted well casing, which has been enclosed in cement and inserted in a well bore drilled into the geothermal stratum from which steam and heated fluid can flow through the well casing to and into another stratum penetrated by the same well bore and casing where entry is permitted through perforations or slots at such stratum. In another aspect, the present inventive system utilizes geothermally heated zones or formations which do not contain moisture or gas sufficient to effect the desired heat transfer from one stratum to another by employing a system through which water or other suitable fluids or materials can be injected into the geothermal stratum through this inventive system and after it is geothermally heated can return into the well casing through perforations or slots in the well casing and thence into the desired stratum for in situ mining or retort utilization. In another aspect, this inventive system embodies the utilization of the bottom portion of the well casing which has been submerged into a geothermal stratum and into which fluid is injected which will absorb heat energy from the surrounding geothermal stratum and after it has attained sufficient heat and pressure will flow through the well casing into the stratum which surrounds the perforations or slots made for its escape into the desired zone. The top portion of the well casing being closed at the surface of the well restrains the flow of the geothermally heated gas or fluids and thus permits the guaging of volumes and pressures rising within the inventive system by recording guages at the well head and permits escaping into the stratum selected for in situ retorting. This aspect of the inventive system also permits a controlled escape of geothermal fluids or geothermally heated fluids through control valves located at the well head which, when open, will tend to encourage flow from the geothermal stratum and also permit utilization of the geothermal energy at the well's surface when desired.
The geothermal in situ mining and retorting system of the invention is peculiarly adaptable to a novel method of oil and gas recovery where pressures are required and where oil is waxy and/or viscous, and flows with difficulty at ambient formation temperatures.
The present invention proposes to exploit many important mineral deposits in the United States that are too deeply buried to permit open-pit mining or exist in a state of viscosity and in an environment of low ambient temperatures which prohibit their economical production with present-day technology.
Prior to recent conservation methods employed in the oil and gas producing industry, many oil fields were improperly produced to secure maximum potential production, with the result that only a fraction of the oil in place was produced and the remaining oil lacked sufficient gas pressure, ambient temperature, or viscosity to permit recovery by the then-existing production methods. As oil consumption increased and overtook new discovery replacement reserves, the oil producing industry returned to the dormant oil fields where in situ reserves challenged its ingenuity for innovation. To release in situ oil from such depleted oil strata, a system of water-flooding was commenced that entailed the injection of water from the surface into the oil stratum where the oil rising above the injected water became available for pumping to the surface. Another method in this so-called secondary recovery method of producing depleted oil wells is a method of steam-flooding, wherein water is heated to steam at a well's surface and then injected into the oil stratum to create the increased oil production. This method involved the consumption of one energy-producing substance in order to produce another. Other methods attempted to promote secondary oil recovery included the emplacement of heating elements within well bores adjacent to oil strata, injection of chemical solutions, fire-flooding, and more recently, the explosion of nuclear devices.
Many of the methods devised for secondary oil recovery have economical or technological limitations that have become apparent by their application. In contrast, the present invention proposes the capture and utilization of the earth's native heat energy for such vital projects as oil recovery, mineral recovery, chemical recovery, metal recovery, and in situ water recovery. The system of this invention permits the capture of heat energy from the depths within the earth and the removal of such captured heat energy into preselected strata or zones where its heat will serve to assist the recovery of oil, minerals, chemicals, metals, or water that may be contained in the preselected stratum or zone. One distinct advantage of this invention is the unlimited quantity of heat that exists within the depths of the earth, reachable by present-day oil drilling technology. Another distinct advantage is that geothermal strata within the earth contain sufficient heat volumes and pressures to permit the invasion of most oil, mineral, chemical, metal, and water strata when communication between a geothermal zone and such product-containing zone is permitted as described herein (in the specification and drawings).
The advantages of the system, as compared to the prior art of mining, are apparent. Secondary recovery methods for depleting oil and gas fields have devised elaborate systems for steam-flooding to increase production and yield from depleting oil fields. In most cases, they consume the very product they are seeking to produce to create the steam for injection into the stratum. Pollutants that result from the consumption of fossil fuels which are used to create steam for such steam-flooding projects, will not result from the use of this inventive system. Also, certain minerals, chemicals, and metals that are soluble in water and temperature but are located too deep within the earth for conventional mining methods may become economical to extract with the use of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
These and many other attendant advantages of the inventive system will readily be appreciated as they become better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which:
FIG. 1 is a schematic view showing how communication is established between two zones in a well where steam and/or hot water from one zone can escape from its habitat through perforations made through the well casing and into the stratum formation and after entering the well casing the steam or hot water is able to flow to another zone where similar perforations allow its entry to promote in situ mining or retorting of minerals, chemicals, or metals which may be contained therein.
FIG. 2 is a cross-sectional view of a well similar to FIG. 1 but adds the potential for injecting water or other fluids through a pipe conducted through the well casing and into the geothermal stratum which may contain sufficient heat but lacks sufficient moisture.
FIG. 3 is a cross-sectional view of a well similar to FIG. 1 and FIG. 2 and contains no perforations in that portion of the well which extends into a geothermal stratum but uses that portion of the well as a fluid reservoir which will absorb heat energy by exchange from the surrounding formation and after attaining sufficient pressure will flow into the perforated mineral, metal, or chemical zone.
Referring now to FIG. 1, the system of this embodiment includes a metal well casing 2 which has been inserted into a well drilled into the earth into a geothermal stratum 11 and the well casing 2 has been surrounded with cement 1 and sealed with a plug 3 at the bottom.
Above the plug 3 located at the lower extremity in the well casing 2, perforations 4 have been made through the well casing 2 and the surrounding cement 1 and penetrating the adjacent geothermal stratum 11 which will permit the escape of steam and/or hot water from the geothermal stratum 11 through the perforations 4 and into the well casing 2.
The heated geothermal fluids which have entered the well casing 2 will now rise up the well casing 2 filling the entire well casing 2 and pass through pipe 9 and valve 8 until a continuous strong production is maintained from the geothermal stratum 11 into the well casing 2 as measured by gauge 7 for temperature and pressure, located above the well's cap 6.
After the desired temperature and pressure have been attained at gauge 7 the valve 8 is partially or completely closed to permit the heated gas or fluids from the geothermal stratum 11 to enter perforations 5 and the formation 10 where in situ mining or retorting of contained oil, gas, other minerals, chemicals, and metals may occur. Through other wells not shown which penetrate the formation 10, the oil, gas, and other products are subsequently recovered.
FIG. 2 illustrates the preferred closed system with auxiliary equipment such as the fluid injection pipe 12 and a bottom-hole plug 3 which surrounds the fluid injection pipe 12 completely sealing the metal well casing 2 at the well's bottom. This embodiment of the inventive system contains a pump 13 to inject fluid under pressure into the geothermal stratum 11 as required.
Referring now to the top of the well auxiliary equipment as shown in FIG. 2, there is both a fluid injection pipe 12 and a fluid withdrawal pipe 9 which permits adequate testing of gas or fluid in the well casing 2 prior to partial or complete closing of valve 8 located on the fluid withdrawal pipe 9.
Referring now to the fluid circuit as illustrated in FIG. 2, fluid enters the injection pipe 12, from a source not shown, passing through valve 8 and into pump 13 which controls the pressure of the fluid injected into the geothermal stratum 11. After being heated in the geothermal stratum 11 the steam or hot water enters the well casing 12 through perforations 4 and rises in the well casing 2 to invade the mineralized stratum 10 by passing through the perforations 5 made through the well casing 2, the cement 1, and penetrating the mineralized stratum 10. Pressure and temperature of the steam or hot fluid within the well casing 2 is measured by gauge 7. The valve 8 in line 9 maintains a high pressure within casing 2 when the valve is partially or completely closed.
To initiate recovery of the oil, gas, minerals, chemicals, or metals after in situ retorting has been accomplished in the mineralized stratum 10, other conventional wells, such as a producing well 20 extending from the surface into the stratum 10, would produce the products.
Referring now to FIG. 3, this method of in situ retorting within a mineralized stratum 10 would serve to utilize geothermal stratum 11 which may contain excessive contaminants or lack moisture but possess sufficient heat. This method excludes the perforations 4 and depends upon a sufficient heat exchange to be accomplished to effect heating of the fluid 14 to sufficient temperature to effect its rise and entry into perforations 5 and the mineralized stratum 10.
Recent technology in drilling large diameter wells into the earth provides a means to effect large reservoirs of fluids 14 and large areas of heat exchange surfaces on the well casing 2 which is submerged into geothermal stratum 11.
With respect to the drilling of wells for in situ retorting of gas, oil, minerals, chemicals, or metals, temperatures within the earth increase with depth at a rate of approximately 3° C. for each 328 feet of depth. However, abnormal increases over this mean occur in many instances because of faulting, volcanism, metamorphosis, chemical, and radiological activities. All oil and gas fields are related to entrapments which are related to faults and such faults are rich sources of geothermal heat energy. It has also been noted in many deep wells drilled into the earth that deep-seated faults contain excessive temperatures. At some depth beneath every square mile of the earth's surface lies a vast store of geothermal heat energy which can, in many instances, be put to work for in situ mining or retorting.
When it is desirable to discontinue the flow of geothermal gases or fluids into a preselected zone, it can easily be accomplished by employing conventional well remedial methods such as inserting packers, squeezing off zones, or cementing of well bores.
It is recognized that various, more extensive communication methods between geothermal zones and other zones may become obvious, such as mining the geothermal fluids from one well and returning it into another well and into a different zone.
The possibilities of utilization of this inventive system are infinite, and grandiose schemes are envisioned, such as repressurizing entire oil and gas fields, mining minerals, chemicals, and metals which have heretofore existed too deep for economic mining and opening new vistas of mining procedures by the controlled displacement of geothermal temperatures from one stratum or zone within the earth into other preselected strata or zones.
Whereas the invention has been described with reference to recovery of oil, gas, chemicals and minerals, it is within the scope of the invention to employ the system described hereinbefore to retort impure, salty or brackish waters within strata beneath the surface of the earth in order to recover pure water therefrom.