AU514112B2 - Solution well mining - Google Patents

Description

U COMMONWEALTH OF AUSTRAQ~ Mt A 1 0 I PATENTS ACT 1952

14 APPLICATION FOR A PATENT (CONVENTION OR NON CONVENTION)

;IQ 37418 /78 xv We ,UNITED STATES OF AMERICA Represented by the Secretary, United States Department of Commearce, NTIS of 5285 Port Royal Road, Springfield, Virginia, United States of America,

hereby apply for the grant of a Patent for an invention entitled

"WELL PERFORATING METHOD FOR SOLUTION WELL MINING"

which is described in the accompany specification. complete The application is a Convention application and is based on the application(s) for patent or similar protection made in United States of America on 24th June., 1977 under No. 809,881

0 g~\Pell

Oraddres:. for service is care of DAVIES COLLISON, Patent Attorneys, of 1 Little Collins Street, Melbourne, in the State of Victoria, Commonwealth of Australia.

Dated this 8th7 day of SEPTEMBER 498

(A member of the firm of DAVIES COLLISON) for and on behalf of the Applicant.

(b)

To: THE COMMISSIONER OF PATENTS Davies Collison, Melbourne and Canberra.

OR (CO!AIDINEDl NON'-CONNVFNTION4 COMMONWEALTH OF AUSTRALIA PATENT$ ACT 1952-1969

DECLARATION IN SUPPORT OF CONVENTION OR NON-CONVENTION APPLICATION FOR A 37418 /78 PATENT OR PATENT OF ADDITION

(The declaration shall be rnade by 'he applicant, or, if the applicant is a body corporate, by a person authorized by the body coi. )rate to make the declaration on its behalf).

In support of the Application made for a ptn.for an invention entitled Irnset title of invention. TELL PERFORATING MSIEOD FOR SOLUTON WELIL 1P'tENING

insert full name(s) and address(es) I Peter F. Urbach, Authorized Siqnatory Officer: for of declarant(s). -We- UNITED STATES OF AMERICA, represented by the Secretary, United States DeparbTrent of Corrnerce, NTIS 5285 Port Royal Road Springfield, Virginia, U.S.A.

do solemnuly and sincerely declare as follows I am lam~ atnt Delete the words which are not applicable. we ppa ff f -add!F1ffn Insert full name of applicant Com- or I am authorized by pany. UNITED STATES OF AMERICA

the applicant fur the patent to make this declaration on its behalf.

Delete the wor"~ which are not applicable. Insert full name(s) and address(es) or George A. Savanick and Walter G. Krawza, respectively of actual inventor(s). r-esidents of 154 Juniper Lane, Apple Valley, M-innesota, U.S.A., and 11881 205th Street, West Lakeville, Minn-esota, U.S.A.

Yx the actual inventors...of the invention and the facts upon which the applicant.... are entitled to make the application are as follows State manner in which opplicant(a) derive title from actual inventor(s). An Assignnrent dated June 26, 1978 whereby the applicant is the assignee of the said inventors.

(Paragraphs 3 and 4 apply onl to Convention applications). 3. The basic application as defined by S-3ction 141 of the Act .m ade

Insert country and date of Mllsn in Uited States of America on the T .97.7 of each applicstion on which prio- by Savanick an qale G5 rwza fily is based.

Insert full namp o f Applicant in by escL basic application.

4. The basic application referred to in paragraph 3 of -this Declaration wYaS the, first application made in a Convention country in respect of the invention the stubjoL~t of the applicati Ion, Virginia, U.S.A. Sinatuse(a) of declarant(s). Declared at Springfield,/ this, 31 day of July,, 1973.

(12) PATENT ABRIDGMENT (11) AU-Bl-37 418/78 (19) AU J-3 AUSTRALI A

(54) Solution well mining (71) United States of America, represented by the Secretary United States of America. NTIS.

(21) 3' 418/78 514 112 (22) 23.6.78 (23) 23.6.78 (24) 24.6.77 (31) 809881 (32) 24.6.77 (33) US (43) 3.1.80 (44) 22.1.81 2 E21B 43/114 E21C 45/00 (51) E21B 43/00

(72) Savanick, and Krawza, W.G. (74) DM (57) Claim 1. a solution mining method wherein an In injection well and at least one recovery well are employed which extend at least to the depth of a mineralized zone, and a leaching solution is pumped from the injection well through the mineralized zone to the recovery well and pumped up from the latter iL a liquid solution containing the mineral to be recovered and wherein the walls of said wells include a cemented plastic casing, the improvement in said method comprising the step of perforating the cemented plastic casing of the walls

of said injection well and said at least one recovery well using a high pressure water jet so asto provide a plurality of holes therein, the pressure of said high pressure jets being several thousand psi, said holes in the recovery well being on a non-uniform, predetermined pattern along the height of the well adjacent to the mineralized zone with their greatest density being near the bottom of the mineralized zone and the least density of holes being adjacent to the top of the mineralized zone.

Dl 1.2

51 4 1 1 2 COMMONWEALTH OF AUSTRALIA

PATENTS ACT 1952 This docupment cionlains ihe amendments made under Setion 49. COMPLETE SPECIFICATION

(Original) and is correct for pri .ig. FOR OFFICE USE DPEC 1 37418/78 Class Int. Class

Application Number: Lodged:

Complete Specification Lodged: Accepted: Published:

Priority:

Related Art:

Name of UNITED STATES OF AMERICA A 4-z- i

Address 5285 Port Royal Road, Springfield, Virginia, United States of America

Actual Inventor(s): GEORGE A. SAVANICK and WALTER G. KRAWZA

Address for Service: DAVIES COLLISON, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

Complete specification for the invention entitled:

"WELL PERFORATING METHOD FOR SOLUTION WELL MINING"

The following statement is a full description of this invention, including the best method of performing it known to us

An improved method of solution well mining is provided

which, among other advantages, enhances the injectivity of the

,o wells and eliminates the need for underreaming and the use of I-

oO well screens. In solution well mining, a leaching solution

dr is pumped into an injection well so as to flow through a

i mineralized zone to a plurality of production wells, the solution

which contains the mineral to be recovered being pumped out of

the production wells. The invention provides for using a high

pressure water jet to perforate the cemented casings of the

-well so as to, inter alia, enhance injectivity and provide sand

control. The perforations are arranged in a preselected

non-uniform pattern in the production well, with the density

being the greatest at the bottom of the zone, so as to promote

uniform flow of the solution.

la

;-iiili;;-i;l~

Field of the Invention

The present invention relates to an improved method

of solution well mining and, more particular, to the use of a

water jet perforator in such mining.

Background of the Invention

As noted hereinabove, the present invention is

particularly concerned with solution well mining, such as is CO Z employed in mining uranium, wherein a leaching solution is co ,tilized. In general, such an operation employs a plurality of wells including an injection well into which the leachant

e is pumped and at least one production or recovery well which is

located some distance from the injection well. The wells

extend into a mineralized zone, a substratum containing

the mineral sought to be recovered, and the leaching solution

passes through the zone from the injection well to the recovery

well and carries with it the mineral to be recovered, viz.,

uranium.

Such uranium leaching wells are conventionally cased

with polyvinyl chloride and cemented to depth beyond the

mineralized zone. The grouted casing in the mineralized zone is

then removed with a mechanical reaming device and a so-called

well screen is placed in the mineralized zone of the well.

This well screen is designed to permit only essentially sand

free liquid to flow into the well bore. It will be appreciated

that sand must not be permitted to enter the well bore because

such sand will drastically accelerate the wear of the downhole

submersible centrifugal pumps used to lift the leachant to the

surface. It will be understood that the process described

above, wherein the well is underreamed and a well screen used to

prevent the ingress of sand, is relatively expensive and time

~~i~i~iL~i-.ri 'i-il-:l1Lui i 1 consuming.

A further, more general problem associated with

uranium leaching wells is that many wells exhibit below standard

injectivity so that little or no mineral recovery is achieved.

Although well stimulation methods such as "acidizing" are

available, these simply are not effective in many instances.

As will be discussed hereinbelow, the present invention F- concerns the use of a water jet perforator in uranium solution CO r- mining and like applications. It is noted that casing

perforators using fluid jets have been used for cutting steel

casings in oil wells. Although this art is not thought to be

relevant, reference is made to U.S. Patent Nos. 2,638,801

(Klassen et al); 2,302,567 (O'Neill); 2,315,496 (Boynton);

3,066,735 CZingg); and 3,130,786 (Brown et al) which disclose

various forms of perforating apparatus for this purpose.

Characteristically, these apparatus employ a drill fluid which

contains an abrasive such as sand or grit and/or a chemical

used in enhancing perforation. The use of an abrasive jet

presents operational problems particularly with regard to wear.

Moreover, the pressures used are generally substantially lower

than employed in accordance with the present invention.

Summary of the Invention

In accordance with the present invention, a method

for improving the operation of solution well mining is provided

wherein high pressure jets of water are utilized to perforate

the casinos of the wells. This method provides for stimulation

of the injection of leachant solutions through uranium leachinc

injection wells even where these wells exhibit subpar

injectivity and do not respond to conventional well stimulation

methods, such as the use of acids. Further, the method

Sprovides enhancement of the permeability of the uraniferrous

sand in the vicinity of the well bore (in an annulus of about

one-foot thickness through the length of the mineralized zone)

by selective removal of clay particles in the mineralized zone. cc IZ In addition, the method of the invention eliminates the c00 expense and time required in underreaming the casing and the placement of well screens to achieve sand control as described

3 hereinabove.

A further very important feature of the method of the

present invention is ability to provide a more uniform flow

pattern through the mineralized zone from the injection well

to the recovery well. This is accomplished by the placement

of a higher density of holes at the base of the mineralized

zone than at the top of the zone near to the centrifugal

suction pump. This technique is used in the recovery well to

prevent "channelizing" of the mineral zone and to ensure that

the centrifugal pump provides equal suction throughout the face

of the zone opening on the recovery well and thus provides

uniform flow within the mineralized zone.

Other features and advantages of the invention will be

set forth in, or apparent from, the detailed description of a

preferred embodiment found hereinbelow.

Brief Description of the Drawings

Figure 1 is a schematic diagram used in the

explanation of the operation of a solution mining well system,

with the use of a water jet perforator in accordance with the

invention being illustrated therein;

Figure 2 is a schematic side elevational view of a

water jet perforator in accordance with a presently preferred

embodiment of the invention;

V

Figure 3 is a longitudinal cross-sectional view, to

an enlarged scale, of the nozzle of Figure 2.

Description of the Preferred Embodiments

As was briefly explained in the introductory portions

of this application, solution well mining is a relatively

recently developed technique for recovery of minerals,

particularly uranium, from zones or substrata located beneath

the surface of the earth. Referring to Figure 1, such a

"7 mineralized zone is indicated at 10. The technique employs an

t- injection well, denoted 12 in Figure i, and a plurality of

production or recovery wells arranged about the injection well.

A single recovery well 14 is shown in Figure 1 but conventionally

the wells are arranged in a five spot pattern and are spaced

from the injection well by distances of between 10 and 100 feet.

The wells are characteristically 4 to 8 inches in

diameter and present practice in the uranium leaching industry

is to case and cement the sidewalls of the wells to a depth

beyond the mineralized zone. Characteristically, polyvinyl

chlocride (PVC) is used as the casing material. The cemented

casings are indicated at 12a and 14a in Figure i. In the

conventional systems described above, the grouted casing in the

mineralized zone is removed with a mechanical reaming device

and a well screen is placed in the mineralized zone to permit

only essentially sand free liquid to flow into the well bore.

In operation, a surface pump (not shown) is used to

inject a leachant into the injection well which passes

therefrom through the mineralized zone 10 in the direction

indicated by arrows 16 to the recovery well 14. An electronic

centrifugal suction pump 18 is located down in the well 14 and

is used to recover the liquid which passes through the mineralized zone, this liquid containing the uranium or other mineral sought to be recovered. As noted, sand must not be permitted to enter the well bore because such sand drastically accelerates the wear on such downhole submersible centrifugal pumps used to lift the leachant to the surface.

As discussed hereinbefore, the present invention CO r-i concerns the use of a water jet perforator for the well casings

t- which provides dramatic improvement in the min.lng operation. The water jet perforator is indicated schematically af- 20 in

Figure 1 and, as shown in more detail in Figure 2, basically

comprises a hose 22 connected to a pump (not shown in Figure 2

but indicated schematically at 24 in Figure a swivel 26

supported on a swivel support frame 28, a string o- high-

pressure pipe 30, and a nozzle 32. A pipe coupler or couplers

34 are also employed and the nozzle 32 is connected to the

pipe 30 through an elbow 36.

The pump 24 generates a pressurized flow of water

which is conducted through the flexible hose 22 to the swivel

26 mounted at the top of the pipe string 30. Swivel 26 permits

the pipe string 30 to be rotated and also provides a location

to connect the flexible hose 22 to the pipe. The pipe string

is comprise. of 20-foot sections connected by high-pressure

couplers such as indic-ted at 34. The nozzle assembly,

including elbow 36 and nozzle 32, at which the pipe string

is terminated, changes the flow direction from vertical, down

the length of the pipe 30, to horizontal, at the exit of

nozzle 32. It will be appreciated that the nozzle converts the

high-pressure energy of the water into kinetic energy thereby

producing the cutting jet.

Considering a specific embodiment of the invention,

-the pump 24 can be a Kobe Size 4J 30,000 psi horizontal

triplex pump driven by a 150 h.p. 1,800 rpm motor. The triplex

pump is equipped with either a 1-1/16" or 5/8" diameter plunger

and liner assemblies and has a 5-inch stroke. When the pump is

o fitted with the 1-1/16" diameter plunger and liner assembly,

OO 21 gpm is displaced at a pressure of 10,000 psi. When the pump

is fitted with a 5/8" diameter plunger and liner assembly, 7 gpm at 30,000 psi pressure is displaced. In general, the C%_J water pressure utilized is between 8,000 and 25,000 psi, with

10,000 psi being used for many applications.

The piping 30 is, as stated, composed of

lengths of 1" OD by 9/16" 1D, 316 stainless steel, 15,000 psi

working pressure seamless pipe. The nozzle assembly comprises

the high-pressure elbow 36 with a welded steel centralizer

and containing a Nikonov-Shavlovskii nozzle 32 in the outlet

port. Nozzle 32 is illustrated in Figure 3 and includes a 130

conical taper (c 130 with a straight section adjacent to the

nozzle outlet. The nozzle 32 is constructed of beryllium-copper

and heat treated, after machining, to minimize wear caused by

the fluid jet. Preliminary tests have indicated that it is

unnecessary to use nozzle diameters less than 0.018 inch or

pressures in excess of 10,000 psi to provide acceptable

perforat.ons. Further, nozzles with diameters of 0.018 inch

or less are impractical in a field environment because of

plugging problems. Moreover, in the nozzle size range of

0.026 to 0.043 inch, the larger diameter nozzle appear to be

more effective.

It is noted that in order to raise and lower the

water jet perforator within the borehole, the perforator tool is

suspended from a device (not shown) which is designed for this purpose, such as a Smeal derrick fitted with a reel and cable. As stated hereinabove, in accordance with a very important feature of the invention, the perforations made in the production or recovery well 14 are arranged so as to e.nhance flow through the mineralized zone. In this regard, when water enters a production well it will flow toward the intake of the pump (pump 18) which is usually located just above the screen referred to above. 'The phygics of the pump suction cause most of the water to enter into the well bore at the top of the screen section, thereby forcing most of the leachant to flow across the top of the screen interval. Thus, mineralization located toward the base of the screened section is less accessible to leachant. By placing the perforations in the production well in such a manner that the perforation density is greatest at the base of the mineralized zone and least at the top nearest the pump, the leachant can be forced to flow uniformly through the length (height) of the mineralized zone. Further, in addition to providing a graded hole pattern, the holes can be limited to the side of the casing adjacent the mineralized zone. In general, the holes produced by the perforator in the recovery section are about O.l'-inch in diameter. It will be understood that since the injec-tion well does not use such a pump, the gradation of the perforations, described above with respect to production wells, k.s not necessary in injection wells and a more uniform 'pttern would typically be used. The number of perforations actually used, is a matter of choice to some extent, with exemplary field operations employing 209 pe-.cforations in a 12.5 ft. zone, at a bottom depth of 436 ft.; 310 perforations in a 7.5 ft. zone, at a bottom depth of 438.5 ft; 326 perforations in a 9 ft. zone, at a bottom depth of 425 ft.; 125 perforations in a 7.75 ft. zone, at a bottom depth of 425.25 ft.; 250 perforations in a 9 ft. zone, at a bottom depth of 425 ft.; and 532 perforations in a 13 ft.

zone, at a bottom depth of 258 ft.

As discussed hereinabove, the method of the invention

provides many important advantages over prior art techniques. oa One of the most important of these is the very dramatic

i increase in the so-called "injectivity" and hence productivity

Sof the wells immediately after perforation. In fact, the i injectivity rates of the various wells referred to in the

examples in the preceeding paragraph have been so vastly

improved that the input to all of the wells was subsequently r a I throttled.

It should be noted that the invention has been oQ described with respect to uranium mining but that the same method

is also applicable to, for example, copper leaching.

i

I

::i

Claims (1)

1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:-

   1. In a solution mining method wherein an injection

   well and at least one recovery well are employed which

   extend at least to the depth of a mineralized zone and a

   leaching solution is p!imped from the injection well through

   the mineralized zone to the recovery well and pumped up from

   the latter in a liquid solution containing the mineral to be

   recovered and wherein the walls of said wells include a

   cemented plastic casing, the improvement in said method

   comprising the step of perforating the ceme .ted plastic casing

   of the walls of said injection well and said at least one

   recovery well using a high pressure water jet so as to provide

   a plurality of holes therein, the pressure of said high

   pressure jets being several thousand psi, said holes in the

   recovery well being on a non-uniform, predetermined pattern *go* alongthe height of the well adjacent to the mineralized

   zone with their greatest density being near the bottom of the

   mineralized zone and the least density of holes being adjacent

   to the top of the mineralized zone.

   2. A method as claimed in claim 1 wherein the plurality

   of holes are provided in the well casing solely on the side

   of the casing adjacent to the mineralized zone.

   S3. In a solution mining method wherein an injection

   well and at least one recovery well are employed to extract

   minerals from a mineralized zone located therebetween, the

   wells extending to a depth which is at least that of the

   mineralized zone and at least the recovery well including a

   I 1 el'I I I II I 11, 1 .1.111".-C 11, .1 11-11

   11

   casing on the side walls thereof, and wherein a leaching

   solution is pumped from the injection well through the

   mineralized zone to the at least one recovery well anr

   pumped from the latter in a liquid solution containing

   the mineral to be recovered, the improvement wherein a high

   pressure jet is used to perforate the casing of the recovery

   well to provide a plurality of holes therein arranged in a

   nonuniform pattern along the height of the casing adjacent

   to the mineralized zor.e so as to obtain substantially uniform

   flow through said mineralized zone, said pattern of holes

   being such that the density of holes is greatest at the

   base of the mineralized zone and least at the top of the

   mineralized zone.

   4. A method as claimed in claim 3 wherein said jet

   comprises an abrasive-free water jet.

   In a solution mining method wherein there is an

   injection well with a cemented plastic casing wall and a

   recovery well with a cemented plastic wall which are employed to extend at least to the depth of a mineralized zone com-

   prising the steps of

   prom the plastic casing walls of said

   injection and recovery well with a high

   abrasive-free high pressure water jet to

   forri a non-uniform predetermined pattern of

   holes along the height of the well adjacent

   to the mineralized zone so as to provide

   uniform flow of a leaching solution; and pumping a leaching solution from the injection well by way of the holes perforated in its plastic casing through the mineralized zone and to the recovery well and surface.

   Dated this 14th day of August, 1980

   UNITED STATES OF AMERICA Represented by the Secretary, United States Department of Commerce, NTIS

   by its Patent Attorney DAVIES COLLISON

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   37 ,418/78

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