US3730592A

US3730592A - Method of subterranean drilling and mining

Info

Publication number: US3730592A
Application number: US00148527A
Authority: US
Inventors: W Wenneborg; P Bunnelle; B Payne
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1971-06-01
Filing date: 1971-06-01
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

A method is provided for drilling into and mining a subterranean deposit of granular ore. The method incorporates a drilling function, a mining function and a novel change in function between drilling and mining by imposition of a hydraulic actuating force originating from the ground surface. The method is capable of mining a granular ore deposit located in proximity with or below an aquifer without substantially removing water from the aquifer. An embodiment of the method permits the change in function between drilling and mining to be repeated as often as necessary to mine several layers of granular ore having intervening layers of overburden.

Description

0 United States Patent 1191 [111 3,73%,592 Wenneborg et al. 1 May 1, 1973 METHOD OF SUBTERRANEAN 3,439,953 4/l969 Pfefferle ..299 17 DRILLING AND MINING Primary ExaminerErnest R. Purser [75] lnvemors' 2 3 ii g gfi i i f gggg Att0rney-Nicholas DeBenedictis, Frank Lanno, Eu- Clara P iW R y Char gene G. Seems and Pauline Newman leston, W. Va. ABSTRACT [73] Asslgneez FMC Corporation New York A method is provided for drilling into and mining a [22] Filed: June 1, 1971 subterranean deposit of granular ore. The method incorporates a drilling function, a mining function and a [21] Appl' 148527 novel change in function between drilling and mining by imposition of a hydraulic actuating force originat- [52] U.S. Cl. ..299/l7, 175/67, l75/2l3, in from the ground surface. The method is ca able of g P 175/422 mining a granular ore deposit located in proximity [51] Int. Cl ..E2lc 43/00 with or below an aquifer without substantially remov- [58] Field of Search .1 .299/4, 5, l7; ing water from the aquifer.

175/25 422 An embodiment of the method permits the change in [56] Referencs Cited function between drilling and mining to be repeated as often as necessary to mine several layers of granular UNITED S E PATENTS ore having intervening layers of overburden. 3,155,177 1 1/1964 Fly fins/25 x 9 Claims, 2 Drawing Figures METHOD OF SUBTERRANEAN DRILLING AND MINING BACKGROUND OF THE INVENTION 1 Field of the Invention Our invention involves drilling into subterranean deposits of granular ore and mining the granular ore employing well drilling hydraulic apparatus.

2. Description of the Prior Art Known methods for well mining of granular ore such as phosphate ore require pre-drilling a well into a granular ore matrix and lining the well bore with mud or casing. A mining tool inserted through the well casing disintegrates the ore by jetting a mining fluid, usually water, into the ore matrix. A slurry containing the mining fluid and the granular ore is formed and pumped upward through the mining tool to the ground surface. Such methods are expensive because of the cost of lining the well, assembling and disassembling the drilling pipe string and assembling and disassembling the mining tool. In order for a combined drilling and mining method to be practical it is necessary for the changing of function between drilling and mining to be highly dependable. I

US. Pat. No. 3,3 l 1,414 discloses drilling a well with a mining tool without pre-drilling. Such use of the mining tool is suitable only where no layer of overburden such as limestone or cap rock covers the ore matrix. Normally there is such a layer, and the well must be pre-drilled before insertion of the mining tool.

US. Pat. No. 3,155,177 discloses a method for underreaming a well, utilizing an apparatus that can also be used to bore deeper into the well. Valves operated by electric motors located within the drilling and min ing head convert the apparatus from drilling operation to under-reaming operation. The amount of force that can be applied to convert the apparatus from drilling operation to under-reaming operation is limited by the size of the electric motor that can fit within the drilling tool inserted in the well. The apparatus is further limited by utilizing a common flow path for returning both the drilling fluid and the mining fluid to the ground surface.

US. Pat. No. 1,851,565 shows a mining apparatus that is inserted into a pre-drilled hole. A mining fluid is projected from a nozzle to fluidize the substance to be mined and the accumulated mixture is lifted by an ejector upward through the mining apparatus to the ground surface. No provision is made for drilling with the mining apparatus.

In order to drill from the ground surface through any stratum to a deposit of granular ore, it is customary to use a rotary type drill rig. When the granular ore deposit, which can be hundreds of feet below the ground surface, is reached mining of the ore is achieved by jetting a stream of fluid into the ore matrix to form a slurry mixture of ore and fluid and pumping the slurry to the surface. It is desirable to combine the drilling and mining operation into a single operation.

A problem encountered in developing a method which combines drilling and mining without removing the tool from the Well is the establishment of reliable controls on the ground surface by which the underground operation of the tool can be converted from drilling to mining. A serious problem associated with converting the underground operation of the tool from drilling to mining without removing the tool from the well is the possibility of plugging or jamming of the tool mechanism with particles during drilling or mining. Such particles may prevent or impede the changing of function and require substantial forces to effect conversion between mining and drilling.

Usually granular ore deposits are located in proximity with or below an aquifer; that is, a water-bearing permeable stratum such as rock, sand or gravel. In such situations it is necessary to drill or mine through or into proximity with the aquifer in order to reach the granular ore deposits. When a well is drilled into or just above an aquifer, then water from the aquifer enters the area being mined. This occurs even though the aquifer is situated slightly below the granular ore deposit, because the aquifer has a pressure head sufficient to raise its water to the level of the water table in the area. Drilling a well through an aquifer into granular ore causes water to cascade from the aquifer down through the well into the granular ore. To avoid this difficulty, open pit mining has been tried in combination with large capacity pumping systems which remove sufficient water to lower the water table in the surrounding area and prevent water from entering the pit. Although open pit mining in combination with pumping to lower the water table is practiced, it has disastrous consequences upon the surrounding areas that use the aquifer as a source of water, because removing large quantities of water from the aquifer to lower the water table interferes with others obtaining water from the aquifer. Lowering of the water table has caused wells used by the surrounding population for potable water to become dry. Legislation prohibiting such activities is being considered and may have been enacted in some localities. Therefore, a mining method which eliminates the need to lower the water table may soon be the only possible method of mining granular ore in areas having an aquifer and such a method is provided by our invention.

SUMMARY OF THE INVENTION The present invention provides a method for drilling into and mining a subterranean deposit of granular ore. A well is drilled with a tool and then our method changes the function of the tool from drilling to mining while the tool is in the well. The change in function of the tool is effected by a hydraulically actuated apparatus in the tool. This hydraulic actuated apparatus is responsive to a hydraulic actuating force originating from the surface and transmitted through atool string to the tool by an actuating fluid. During both drilling and mining, our method pumps fluid from the surface down through an annulus in a tool string. However, our method employs two distinct paths for returning the fluid to the surface, one path is used during drilling and another path during mining.

During drilling, the fluid flows from the annulus through a drill bit attached to the bottom of the tool string and the method returns the fluid and cuttings to the surface through the space between the tool string and the well bore. During mining the fluid is divided into two portions. One portion of the fluid flows from the annulus in the tool string through a mining element into the granular ore to form an ore slurry. The remaining portion of the fluid flows from the annulus through an eductor up to the surface through a passage centered within the tool string. This flow of theremaining portion'of the fluid draws the ore slurry to the-eductor and lifts it to the surface through the samecenter passage in the tool string. I v j v Drawing the ore slurry from around the tool creates a cavity in the granular ore surrounding the tool. If the granular ore deposit is situated in proximity with or below an aquifer, then water from the aquifer tends to flow into this cavity. This water interferes with the mining of the granular ore by substantially increasing the quantity of fluid that must belifted up to the surface along with the ore. Our method can substantially prevent the flow of water from the aquifer into the cavity by mining with the cavity filled and pressurized with the mining fluid.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a broken sectional view in elevation of an apparatus capable of performing the present inventive method with the apparatus depicted in the drilling mode.

FIG. 2 is a sectional view in elevation of the lower portion of the same apparatus depicted in the mining mode.

DETAILED DESCRIPTION OF THE INVENTION The method provided by our invention is for drilling into and mining a subterranean deposit of granular ore.

Drilling employs both mechanical and hydraulic forces that are transmitted from the surface to a bit through a tool and tool string. The hydraulic forces are applied to the bit by a fluid used for drilling. Our method returns the drilling fluid to the surface from the bit in the space between the tool-string and the well bore and the returning fluid carries with it the cuttings from the drilling of the well. The bit can be rotated by rotating the tool string and/or by utilizing the hydraulic forces transmitted-by the drilling fluid to the bit. Mining is accomplished by pumping the fluid used for mining through the tool string and a mining element into the granular ore matrix to form an ore slurry and educting the ore slurry to the surface. The fluid used for drilling and for mining can be the same fluid and is usually water.

Conventional apparatus for drilling and for mining is required on the surface, including a platform from which the tool, tool string and bit are suspended, means for supplying the fluids for drilling and mining to the tool string, means for rotating the tool string, means for raising and lowering the tool string for drilling and means for adding to or removing tool sections from the tool string.

A subterranean deposit of granular ore can be economically mined employing ,the method provided by our invention as follows:

Drilling a well from the surface into the granular ore by rotating a bit connected to a tool and a tool string;

transmitting a fluid during drilling to the bit from the surface through an annular path within the tool string;-- I

removing the cuttings from the drilling operation by the fluid through the space between the well and the tool string; when the tool has reached thegranular ore, adjusting a hydraulic actuating force exerted on the tool by the actuating fluid to effectuate a change in the tools function from drilling to mining by diverting the" flow of fluid from the bit to an eductor and a mining element of the tool; directing a portion of the fluid through the mining element into the granular ore matrix thereby making a granular ore slurry surrounding the tool bydisintegrating the ore matrix with the fluid; directing the remaining portion of the fluid to an eductor; drawing the granular ore slurry into the eductor and educting the slurry to the surface through a passage within the tool string and surroundedby the annular path.

Mining the ore surrounding the tool creates a cavity around the tool. If the granular ore deposit is situated in proximity with or below an aquifer then the water from the aquifer will flow into the cavity. Pressurizing this cavity with a fluid preferably having equal or greater density than water prevents the aquifers water from flowing into the cavity if the pressure of the fluid in the cavity approximately equals the hydrostatic head exerted by the aquifers water. The mining fluid is employed as the pressurized fluid in the cavity. The cavity can be pressurized with the mining fluid to a desired pressure level and controlled at that level by adjusting the proportioning of the mining fluid between the mining element and the eductor.

The mining element and the eductor preferably contain variable nozzles. Since the portion of fluid flowing through these nozzles may be varied, either one or both of the nozzles preferably contain an adjustable throat. The throat can be adjusted tocontrol the amount of fluid flowing through the nozzle.

During mining, the fluid is essentially divided between the mining element and the eductor. Therefore controlling the portion of fluid flowing through the mining element necessarily controls the remaining portion of fluid flowing through the eductor. The proportioning of fluid between the mining element and the However, the use of an orifice, deflector or similar device is inefficient and results in a substantial pressure drop and loss of power as compared with a controllable nozzle.

'The mining element preferably contains a modulating or closable nozzle that is capable of impinging a high velocity stream of fluid upon the surrounding granular ore matrix and causing formation of a granular ore slurry by disintegrating the matrix. The portion of the fluid that flows through the nozzlev is controllable and capable of being jetted into dense media effectively even when submerged.

The best mode contemplated for practicing the combined drilling and mining method includes adjusting the proportioning of the fluid during mining between the mining element and the eductor. The fluid flowing through the mining element is emitted as a high velocity stream that impinges upon the surrounding granular ore matrix and caused theformation of a granular ore slurry by disintegrating the matrix. The remaining portion of fluid flows through the eductor and draws this granular ore slurry from the surrounding cavity into the tool and lifts the ore slurry up to the surface.

Each specific proportioning of fluid between the mining element and the eductor has a corresponding steady state or equilibrium condition with respect to free-surface level of ore slurry in the cavity and pressure in the cavity. The actual equilibrium conditions that correspond to specific proportions of fluid depends upon such factors as the characteristics of the granular ore deposit being mined, the density of the ore slurry and the depth of the ore deposit.

Both the pressure and the quantity of ore slurry in the cavity can be controlled by regulating the proportioning of fluid between the mining element and the eductor. Whenever the proportioning of fluid between the mining element and the eductor is adjusted then the free-surface level of ore slurry in the cavity and the corresponding pressure in the cavity adjust to new equilibrium conditions.,An adjustment in the proportioning that increases the portion of fluid flowing through the mining element has the following effects; (I) the remaining portion of fluid flowing through the eductor decreases and (2) the free-surface level of ore slurry in the cavity and the corresponding cavity pressure rise until the cavity is filled at which point only cavity pressure increases with an increased portion of fluid flowing through the mining element. An adjustment in the proportioning that decreases the portion of fluid flowing through the mining element has the following effects; l) the remaining portion of fluid flowing through the eductor increases, (2) the free-surface level of ore slurry in the cavity lowers and/or (3) the pressure in the cavity decreases. The pressure in the cavity is normally measured at the depth of the eductor and therefore corresponds to the height of the free-surface level of ore slurry in the cavity until the cavity is filled.

The free-surface level of the slurry in the cavity and the pressure in the cavity can also be increased or decreased by controlling the remaining portion of fluid flowing through the eductor.

There are three preferred sets of conditions for the pressure'and the free-surface level of ore slurry in the cavity during mining. The preferred sets of conditions are referred to hereinafter as HIGH, MEDIUM and LOW conditions. The best conditions contemplated during mining, either HIGH, MEDIUM or LOW, depend upon the characteristics of the granular ore being mined; in particular, the depth of the ore and the types of strata intervening between the surface and the ore.

The HIGH conditions correspond to equilibrium conditions having a high fluid pressure in the cavity and is preferably practiced with the granular ore deposit being mined is at a great depth or when it is desired to reduce the mining power requirements. To change to HIGH conditions for mining from LOW or MEDIUM conditions, the proportioning of fluid between the mining element and the eductor is adjusted to cause the ore slurry to fill and pressurize the cavity. This is obtained by increasing the portion of fluid flowing through the mining element. The fluid pressure in the cavity assists the educting of the ore slurry up to the surface by reducing the net pressure head required of the eductor. The net' pressure head that must be supplied by the eductor is equal to the pressure head of the ore slurry in the center return passage to the surface minus the fluid pressure in the cavity. At a particular mining depth and ore slurry density, the net pressure head decreases as the cavity pressure increases. In order to maximize the assistance to educting by reducing the net pressure head, the cavity pressure is maintained as high as possible without fracturing the ore matrix or breaking through to adjoining cavities.

The MEDIUM conditions correspond to equilibrium conditions having a medium fluid pressure in the cavity and is preferably practiced during mining when there is an aquifer above or in proximity with the granular ore deposit. To change to MEDIUM conditions, the proportioning of fluid between the mining element and the eductor is adjusted to cause a resulting equilibrium slurry pressure in the cavity that is sufficient to essentially prevent the flow of water from the aquifer into the cavity. This pressure is referred to as the preventive pressure. At equilibrium conditions corresponding to cavity pressures lower then the preventive pressure, the

amount of fluid educted up to the surface is greater than the amount of fluid pumped into the well when water from an aquifer is entering the cavity. The difference in amounts of fluid entering and exiting equals the amount of water entering the cavity from the aquifer. The preventive pressure has been reached when this difference is zero; that is the amount entering equals the amount leaving. Therefore the preventive pressure for a particular mining area can be determined by comparing the quantity of fluid pumped into the well with the quantity educted out of the well.

The LOW conditions correspond to operating with the ore slurry free-surface level drawn down to below the mining element and corresponds to a low fluid pressure in the cavity. LOW conditions are preferably practiced when. ore depth is not very great and no other complications are present such as aquifers. To change to LOW conditions when operating under higher conditions, the proportioning of fluid between the mining element and the eductor is adjusted to reduce the fluid pressure in the cavity to a minimum which corresponds to an equilibrium pressure that occurs during mining when the cavity is not filled with fluid. In addition to not filling the cavity, the free surface level of the ore slurry is below the level of the mining element.

Mining under the LOW conditions has the advantage of maximizing the effective mining distance. This is because the free-surface level of the ore slurry in the cavity is below the mining element and does not restrict the distance that the mining fluid can be jetted by the mining element.-

Mining under LOW conditions maximizes the rate at which ore can be mined and size of the ore cavity that i can be mined. Mining under MEDIUM conditions prevents interference from an aquifer. Mining under HIGH conditions permits mining at great depths, assists the educting of the ore slurry up to the surface and minimizes the power required for educting.

The actual proportioning of fluid between the mining element and the eductor that corresponds to equilibrium conditions of either HIGH, MEDIUM or LOW depends upon the specific characteristics of the mining element and the eductor employed, the characteristics of the ore deposit and the density of the ore slurry.

Some subterranean deposits of granular ore exist as layers separated by strata of limestone or other hard layers. In such deposits, an embodiment of the method provided by this invention is particularly useful because after first drilling into and then mining a layer of granular ore, the tool is changed back to the drilling mode. This is accomplished by adjusting the hydraulic actuating force exerted on the tool by the actuating fluid to effectuate the change in mode. With the tool in the drilling mode, the well is drilled through the intervening stratum and the tool changed back to the mining mode with the hydraulic actuating force. This permits drilling through intervening layers of overburden and mining the subsequent layers of granular ore without removing the tool from the well.

With the method provided by our invention it is unnecessary to line the well or to pull the drill after drilling because our method employs the tool string both as a drilling string and a mining conduct and employs the tool both as a drilling tool and a mining tool. Our method controls the tool from the ground surface by adjusting the hydraulic forces exerted on the tool by the actuating fluid to an amount sufficient to change the function of the tool between drilling and mining.

Fluid for mining and drilling is transmitted to the tool through an annulus within a tool string. In the drilling mode our method returns the fluid and cuttings to the surface through the space between the tool string and the larger diameter well bore. in the mining mode, the fluid and ore are returned to the surface through a passage centered within the tool string. Returning the drilling fluid by a path outside the tool string prevents cuttings from damaging or interfering with the tool and tends to maintain the well bore open. Returning the mining fluid with its entrained ore to the surface through a center passage rather than an annular passage inside the tool string permits larger pieces of ore to pass up through the center passage. This is because a center passage has greater clearance than an annular passage having the same cross-sectional area.

' This greatly minimizes the possibility of ore pieces becoming lodged inside the passage or interfering with the mining element.

Employing the center passage rather than the annulus for returning the ore slurry to the surface has the advantage of minimizing the pressure drop in the return flow line. A lower return passage pressure drop decreases the pumping power required to educt the ore slurry to the surface. The eductor is relatively inefficient and cannot supply sufficient pumping power for mining at great depths without the improvement supplied by our method; namely, reducing the pressure drop by employing a center passage in combination with the pumping assistance obtained by pressurizing the cavity.

The ore slurry has an abrasive effect upon the walls of conduits in which it flows. Employing a center passage rather than an annulus has the added advantage of limiting the abrasion to the less expensive center tube rather than wearing out both the center and outer tubes by abrasion. This effect is significant since a tool string can be designed with a replaceable center tube.

fluid flow to the bit to maintain the material about the bit in a fluidized state. This prevents binding of the bit in the well and assures that the fluid passages remain open for subsequent drilling.

The mining fluid and the drilling fluid are usually the same fluid and flow through the same annular passage within the tool string from the surface down to the tool.

' mining although at different pressures, the tool can em- During mining, the flow of fluid to the bit is substantially blocked; however, it is preferred to permit some The fluid used to actuate the change in function of the tool, sometimes referred to herein as the actuating fluid, can be the mining fluid and/or the drilling fluid. The actuating fluid can be a separate fluid with its own supply line to the tool from the surface.

Changing the hydraulic actuating force causes a corresponding change in operation of the tool. Changing the hydraulic force (pressure) exerted upon the tool by the actuating fluid causes a corresponding change in operation of the tool by altering the position (movement) of a hydraulically actuated apparatus in the tool. Valve means in the tool respond to these changes in position to effect the necessary flow of fluid between the bit, the mining element, and the eductor. The hydraulic actuating force originates and is controllable from the ground surface. An example of a method for changing the function of the tool employing hydraulic actuating forces originating from the ground surface is set forth below.

1. Actuating a control pump on the ground surface to create the hydraulic actuating force (pressure). I

2. Transmitting the hydraulic actuating force through an actuating fluid supply line from the surface control pump to one or more hydraulic cylinders (hydraulically actuated apparatus) located within the tool.

3. Controlling the flow of fluid to the bit, the eductor and the mining element by valve means located within the tool responsive to the hydraulic cylinders.

The valve means and hydraulic cylinder (hydraulically actuated apparatus) are interconnected such that when the hydraulic cylinder is in a first position, the valve means in the tool are positioned to permit the flow of fluid to the bit and substantially block the flow of fluid to the eductor and the mining element. When the hydraulic cylinder is in a second position the valve means are positioned to substantially block the flow of fluid to the bit and permit the flow of fluid to the eductor and the mining element. The hydraulic cylinder moves between the first and second positions in response to changes in pressure supplied by the surface control pump. v

Since a single fluid is usually used for drilling and for ploy the single fluid itself as the actuating fluid for changing modes of the tool. This is accomplished by designing the hydraulically actuated apparatus in the tool to be responsive to the different pressures of the single fluid during drilling and mining. The hydrauli cally actuated apparatus is in the first or drilling position when the single fluid is at the drilling pressure. Conversely, the hydraulically actuated apparatus in the tool can be designed to be in the mining or second position when the single fluid is at the mining pressure. Furthermore, the hydraulically actuated apparatus is responsive to the single fluid pressure to change between the first and the second positions when the single fluid pressure changes between the drilling and mining pressures. Therefore the actuating force for changing the function of the tool between drilling and mining is supplied by the fluid used for drilling and mining at an actuating pressure other than the drilling and mining pressures. The actuating pressure is preferably between the drilling and mining pressures. This eliminates the need for a separate actuating fluid and a separate hydraulic fluid supply line to the hydraulically actuated apparatus in the tool.

Apparatus capable of drilling into and mining subterranean granular ore according to the method provided by our invention is shown in the drawings and is operated as follows.

With regard to FIG. 1, fluid 50 flows from surface apparatus 10, down through annulus 18 in tool string 12. When the apparatus is in the drilling mode, the fluid flows from annulus 18 through valve means 32 to bit 34. The fluid after flowing through the bit 34 carries cuttings from the drilling of the well up to the surface through the space 28 between the outer surface of the tool string 12 and the well. Cuttings and the fluid flow up to the surface and exit at 14 during drilling. The bit and tool string are rotated during drilling by surface apparatus 16 to drill into the granular ore through overburden 26. In the mining mode (FIG. 2) the fluid 50 flows down through annulus 18. A portion of the fluid 50 flows from annulus 18 through valve means 46 into the mining element 40 and isjetted through a port 42 in outer tube 16 of the tool string 12 into the granular ore. The jetted fluid forms an ore slurry surrounding the tool and tool string. A remaining portion of the fluid 50, flowing down through annulus 18, past mining element 40, flows through valve means 32, up into eductor 30 and continues up from the eductor through center passage 20 of the tool string. The flow of fluid through eductor 30 draws the ore slurry surrounding the tool and tool string through port 36 into center tube 22 and up through center passage 20 to the surface apparatus for recovery in a slurry collection tank, not shown. Actuating fluid 52 flows from the surface through surface apparatus 10 down actuating fluid supply line 48 to hydraulically actuate apparatus 24. The apparatus depicted in FIG. 1, can be changed between the drilling mode and the mining mode depicted in FIG. 2 with hydraulically actuated apparatus 24. The hydraulically actuated apparatus 24 is controlled from the ground surface by the actuating fluid 52. Apparatus 24 controls linkage 38 which in turn controls valve means 32 and 46 for regulating the flow of fluid to bit 34, mining element 40 and eductor 30. When the hydraulically actuated apparatus 24 is positioned in the drilling mode by fluid 52 then linkage 38 positions valve means 32 and 46 to permit flow to bit 34 but not to mining element 40 and eductor 30. Conversely, in the mining mode, linkage 38 positions valve means 32 and 46 to permit flow to mining element 40 and eductor 30 and substantially block flow to bit 34. A variable orifice 44, located after valve means 46 controls the proportioning of fluid 50 between mining element 40 and eductor 30 by controlling the amount of fluid flowing through the mining element.

Additional apparatus capable of drilling into and mining subterranean granular ore according to the method provided by our invention is described in our copending application Ser. No. l48,5()l entitled Subill terranean Slurry Mining Apparatus filed on June 1, 1971.

The best mode contemplated for carrying out the present invention is by the method described above for operating the apparatus illustrated in FIGS. 1 and 2 with the variable orifice 44 being an adjustable nozzle within the mining element for jetting the fluid into the granular ore matrix. The nozzle being adjusted to obtain either the HIGH, MEDIUM or LOW mining condition depending upon the characteristics of the granular ore deposit being mined. This apparatus incorporates the tool inside the bottom section of the tool string and the variable orifice in the nozzle of the mining element.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

What is claimed is:

1. A method for drilling into and mining a subter ranean deposit of granular ore comprising;

drilling a well from ground surface into the granular ore with a tool string having a drilling bit attached to its lower end and containing a tool located above the bit;

flowing a first fluid during drilling from the ground surface through an annular space within the tool string and through the bit;

removing the first fluid and cuttings during drilling up through a passage between the well and the tool string;

changing the function of the tool while in the well i from drilling to mining by adjusting a valve means in the tool with an actuating force exerted by an actuating fluid transmitted from the ground surface to substantially prevent the flow of the first fluid to the bit and to permit flow of the first fluid to both a mining element within the tool and an eductor within the tool below the mining element;

proportioning the flow of the first fluid during mining between a portion flowing through the mining element and a remaining portion flowing through the eductor;

jetting the portion of the first fluid through the mining element into the granular ore to form a mining cavity containing a fluid-ore slurry;

drawing the fluid-ore slurry into the eductor and educting the fluid-ore slurry up to the ground surface through a passage within the annular space of the tool string by means of the remaining portion of the first fluid flowing through the eductor.

2. The method of claim 1 wherein the changing function from drilling to mining is reversible by readjusting the valve means with the actuating fluid whereby the first fluid flows to the bit and not to the mining element and the eductor.

3. The method of claim 1 further comprising adjusting the proportioning of the first fluid between the mining element and the eductor by controlling the amount of one of the portions in order to maintain the cavity filled and pressurized with the fluid-ore slurry at a cavity pressure which substantially equals the hydrostatic head exerted on the cavity by ground water from an aquifer and wherein the first fluid has a density equal to or greater than water.

4. The method of claim 1 wherein the mining element contains an adjustable nozzle through which the first fluid flows and both the portion of the first fluid flowing through the mining element and the proportioning of the first fluid are varied by adjusting the nozzle.

5. The method of claim 1 wherein the eductor contains an adjustable nozzle through which the first fluid flows and both the portion of the first fluid flowing through the eductor and the proportioning of the first fluid are varied by adjusting the nozzle.

6. A method for drilling into and mining a subterranean deposit of granular ore comprising;

removing the first fluid and cuttings during drilling up through a passage between the well and the tool string; changing the function of the tool while in the well from drilling to miningby adjusting a valve means in the tool with an actuating force exerted by an actuating fluid transmitted from the ground surface to substantially prevent the flow of the first fluid to the bit and to permit flow of the first fluid to both a mining element within the tool and an eductor within the tool below the mining element;

drawing the fluid-ore slurry into the eductor and educting the fluid-ore slurry up to the ground surface through a passage within the annular space of the tool string by means of the remaining portion of the first fluid flowing through the eductor;

wherein the first fluid for drilling and mining and the actuating fluid are a single fluid which is maintained at an effective drilling pressure during drilling, at an effective actuating pressure during the changing of functions and at an effective mining pressure during mining.

7. The method of claim 6 wherein the actuating pressure is intermediate with the drilling pressure and the mining pressure.

8. The method of claim 6 wherein the changing of function from drilling to mining is reversible by readjusting the pressure of the single fluid between the drilling pressure, the actuating pressure and the mining pressure thereby permitting drilling through overburden layers to subsequent layers of granular ore and mining the ore layers.

9. In a method of hydraulic mining with a well a subterranean deposit of granular ore situated such that water from an aquifer enters the granular ore deposit during mining, wherein a fluid is pumped into the well through a first passage in a tool string and proportioned between a portion flowing to a mining element and a portion flowing through an eductor, the portion flowing to the mining element is jetted into the granular ore to form a cavity containing fluid-ore slurry, and the portion flowing through the eductor draws the fluid-ore slurry into the tool string and lifts the fluid-ore slurry up to ground surface, the improvement which comprises pressurizing the cavity with the fluid by adjusting the proportioning of fluid between the mining element and the eductor to a pressure that prevents the aquifer water from entering the cavity.

Claims

1. A method for drilling into and mining a subterranean deposit of granular ore comprising; drilling a well from ground surface into the granular ore with a tool string having a drilling bit attached to its lower end and containing a tool located above the bit; flowing a first fluid during drilling from the ground surface through an annular space within the tool string and through the bit; removing the first fluid and cuttings during drilling up through a passage between the well and the tool string; changing the function of the tool while in the well from drilling to mining by adjusting a valve means in the tool with an actuating force exerted by an actuating fluid transmitted from the ground surface to substantially prevent the flow of the first fluid to the bit and to permit flow of the first fluid to both a mining element within the tool and an eductor within the tool below the mining element; proportioning the flow of the first fluid during mining between a portion flowing through the mining element and a remaining portion flowing through the eductor; jetting the portion of the first fluid through the mining element into the granular ore to form a mining cavity containing a fluid-ore slurry; drawing the fluid-ore slurry into the eductor and educting the fluid-ore slurry up to the ground surface through a passage within the annular space of the tool string by means of the remaining portion of the first fluid flowing through the eductor.

6. A method for drilling into and mining a subterranean deposit of granular ore comprising; drilling a well from ground surface into the granular ore with a tool string having a drilling bit attached to its lower end and containing a tool located above the bit; flowing a first fluid during drilling from the ground surface through an annular space within the tool string and through the bit; removing the first fluid and cuttings during drilling up through a passage between the well and the tool string; changing the function of the tool while in the well from drilling to mining by adjusting a valve means in the tool with an actuating force exerted by an actuating fluid transmitted from the ground surface to substantially prevent the flow of the first fluid to the bit and to permit flow of the first fluid to both a mining element within the tool and an eductor within the tool below the mining element; proportioning the flow of the first fluid during mining between a portion flowing through the mining element and a remaining portion flowing through the eductor; jetting the portion of the first fluid through the mining element into the granular ore to form a mining cavity containing a fluid-ore slurry; drawing the fluid-ore slurry into the eductor and educting the fluid-ore slurry up to the ground surface through a passage within the annular space of the tool string by means of the remaining portion of the first fluid flowing through the eductor; wherein the first fluid for drilling and mining and the actuating fluid are a single fluid which is maintained at an effective drilling pressure during drilling, at an effective actuating pressure during the changing of functions and at an effective mining pressure during mining.