COMMISSIONER'S DECISION
Obviousness: Leaching of Subterranean Mineral Deposits
Explosive Fracturing of a deep rock ore body is known. Injection of the leaching
solution in the less severely fractured zone and recovering it in the more
severely fractured zone is not shown in the prior art.
Rejection: Reversed
**************
This decision deals with the refusal of claims C1 to C18 of patent
application 205,542 (Class 166-23). The refusal appears in a letter dated
April 7, 1978, issued as a result of a re-examination of the claims under
Section 45(4) of the Patent Act, i.e. during conflict proceedings.
The application was filed on July 24, 1974 by E.I. Du Pont de Nemours and
Company, and is entitled "Explosive Fracturing of Deep Rock." The Patent
Appeal Board held a Hearing on October 25, 1978 at which Mr. R.E. Vernon
and Mr. A. Brooks, the inventor Mr. Coursen, and Miss C. Asconci, the
applicant's United States agent, represented the applicant.
The invention relates to the leaching of subterranean mineral deposits
in the earth. A network of underground rock fractures produced by
means of explosives prepares the ore bodies for in situ leaching. Figures
1 and 2 of the drawings indicate what the invention is about.
(see formula 1)
Claims C1 to C18 stand rejected in view of the following references;
United States
3,278,233 Oct. 11, 1966 Hurd et al
3,542,131 Nov. 24, 1970 Walton
3,574,599 Apr. 13, 1971 Ortloff et al
3,630,278 Dec. 28, 1971 Parker
3,640,579 Feb. 8, 1972 Lewis
3,647,261 Mar. 7, 1972 Stenger et al
3,666,014 May 30, 1972 Beard
In the rejection it was said, inter alia, that:
The Beard patent shows the use of a high energy explosive device
in the formation of a zone of high permeability, and the creation
of a "chimney" or rubbled zone. A zone of permeability 17 within
and around the fragmented formation is formed surrounding the
chimney. When used throughout the specification (3,666,014), the
terms "fragmented zone" and "fragmented zone of rubble" refer
to the rubbled zone 15 or any other rubbled or fracture-permeated
zone formed by any means well known in the art. The patent also
teaches the injection of a gas (fluid) into the fragmented zone.
The Stenger et al patent teaches solution mining of a metal.
The patent teaches, in column 2 at line 6, that "Permeability
may also be improved by underground fracturing techniques, such
as are employed in the oil industry, although it is desirable
that the brine pass through the ore itself rather than through
cracks in the ore".
The Ortloff et al patent teaches a recovery method for the
in situ disintegration of a solid material comprising an in situ
conversion of the solid material to a fluid solution by chemical
conversion. In column 3 at lines 21 to 28 there is discussed
a procedure if insufficient permeability exists to establish
fluid permeability in the deposit and the residence time of
the leach solution which can be controlled by the rates of
injection and withdrawal of the solution.
The Hurd et al patent teaches that the permeability may be
increased by suitable means, such as hydraulic fracturing in
the in situ leaching of deposits.
The Lewis patent teaches the use of an oxidizing gas which is
percolated through the broken ore and oxidizes the minerals to
form an acid leach solution in the reaction.
The Walton patent teaches the use of explosives to form cavities
and to provide a fractured and cracked permeable zone.
The Parker patent teaches the placing of the input well around
the periphery of the fractures extending out from the fragmentation
zone.
The Stenger et al patent teaches that techniques common in
the oil industry can be used in the solution mining of minerals
and hence, it must be concluded that such techniques would
be considered to be obvious to one working in the mineral
recovery art. It has been well established that a claim may
be struck down on the ground of lack of an inventive step
if it can be shown that it covers a variation of an individual
prior proposal, which variation it would be obvious to make
in the light of the relevant common general knowledge.
The patents to Ortloff et al, Stenger et al, Hurd et al, and
Lewis can be classed as belonging to the mineral leaching
aspect, whereas the Parker, Walton and Beard patents show
techniques that are used in the oil industry which are applicable
to the mineral recovery industry, and in particular the placing
of the injection wells outside the rubblized zone which is
taught in the Parker and Beard patents.
Therefore claims C1 to C18 are rejected on the Ortloff et al,
Stenger et al, Hurd et al and Lewis patents when taken in
view of what is taught in the Parker, Walton and Beard patents.
The first group of patents teaches the leaching of minerals
in situ and such variations as are being claimed are considered
to be obvious variations when taken in the light of the
relevant common general knowledge as exemplified by the
patents to Parker, Walton and Beard.
...
In his response dated July 6, 1978 the applicant stated (in part):
...
In addition, Applicant does not agree with the assertion that
the invention of claims C1 to C18 is an obvious variation of
the techniques of solution recovery of mineral values as disclosed
by Hurd et al in U.S, patent 3278233, Ortloff et al in U.S.
patent 3574599, Lewis in U.S. patent 3640579 and Stenger et al
in U.S. patent 3647261 in view of the teachings of Beard in U.S.
patent 3666014, Walton and Parker.
In all of claims C1 to C18 a leach solution is injected into
a less severely fractured zone in an ore body, which surrounds
a more severely fractured zone in the ore body, and pregnant
leach solution is recovered from the more severely fractured
zone of the ore body.
It is respectfully submitted that none of the cited references
teach or suggest the specific direction of flow of the leach
solution from the less severely to the more severely fractured
zone in accordance with the invention of claims C1 to C18.
The Hurd et al, the Stenger et al, and the Ortloff et al
references indicate that permeability of the ore body may be
increased by fracturing the ore body, but no indication is
given that the presence or location of both more and less
severely fractured zones is of any importance in relation to
maintaining the flow of leach solution.
The discussions by Ortloff et al and Stenger et al about
increasing the permeability of natural subterranean form-
ations is somewhat vague, giving no inkling of any benefits
of particular fracture patterns or of particular flow
directions of leach solution.
It is clear that Hurd et al recognized the difficulties of
maintaining the flow of mineral-pregnant solution resulting
from the formation of impermeable precipitated plugs in the
ore body. There is no indication, however, that increasing
the permeability of the ore body by fracturing minimized
these difficulties, or that any particular type of fracturing
or direction of flow of leach solution was more beneficial
than any other.
It is not clear therefore, how the Hurd et al, Stenger et al,
or the Ortloff et al disclosures taken singly, or in view of
actual common general knowledge, provides any insight into the
solution recovery process of the present invention.
Lewis discloses percolation of a gas through the highly
fractured zone of a so-called nuclear chimney which is flooded
with water. In the invention of Lewis the gas is injected into
a lower portion of the highly fractured zone and mineral-
pregnant solution is withdrawn from the upper portion of the
highly fractured zone i.e. both injection and recovery takes
place within the highly fractured zone. It should be noted
that the fractures in the highly fractured zone in a nuclear
chimney is essentially uniform. This is quite different to
the invention of present claims C1 to C18, which makes use of
more and less severely fractured zones.
...
At the Hearing and in his response to the letter Mr. Vernon questioned the
involvement of the Patent Appeal Board at this point in the conflict proceed-
ings. In addition he also questioned the grounds of rejection and presented
his interpretation on the manner in which art submitted during a Section
45(4) situation may be applied. However Section 45(4) of the Patent Act states
that the Commissioner shall decide if the subject matter of conflict claims
is patentable. If the Commissioner wishes to obtain the assistance of the
Board in making that decision, he is fully entitled to do so (cf. Monsanto v
Commissioner of Patents, F.C.A., June 24, 1977). Furthermore the applicant
himself requested an oral hearing before the Board (letter of June 6, 1978),
and consequently estopped by his own deed from objecting to its involve-
ment.
Claims C1 to C18 were rejected on prior art in the Commissioners letter
dated April 7, 1978. As we have indicated earlier Section 45(4) states
that the Commissioner shall decide if the subject matter of such claims is
patentable and the question before us is whether or not the conflict claims
are patentable over the art.
Mr. Coursen, the inventor, outlined the history of leaching subterranean
deposits and the associated problems. This application increases the network
of fractures in an ore body by detonating an explosive charge and the sub-
sequent introduction of a lixiviant.
Initially the leaching process will cause the heavily shocked rock near the
shot point to decrepitate to fines at a particularly high rate. In time
the chemical attack on the rock by the leaching solution will generate further
fines as well as slimes. The problem that this application is designated
to overcome is the loss of fracture permeability and the plugging of fractures
caused by the presence and production of these various kinds of fines and
their movement during leaching. Accordingly this application directs
the lixiviant flow from less severely fracture zone having small perforations
to the more severely fractured zone with its larger perforations thereby
preventing clogging by the fines and slimes.
Considering the prior art we find that Ortloff shows a method of leaching
copper ore in situ. In this process a well extending from the earth's surface
to the deposit allows a leach solution to be injected to react with the ore.
A second well serves to recover the pregnant leachant. In this patent the
ore is normally used in its natural condition although Ortloff recognized that
it may be necessary to increase permeability ".., by means known to those
skilled in the art of fracturing subterranean formations...." We find no
further indication how permeability can be increased nor do we find any
problem relating to the plugging of fractures with fines or the direction
of fluid flow.
Stenger also leaches metal values from underground ores by injecting a brine
in one well in the ore body and then collecting the reacted brine in another
well in the ore body. As in Ortloff the ore is used in its natural
condition (no detonation) and there is no mention of fines and slimes. He
recognized that permeability may be improved "... by underground fracturing
techniques such as employed in the oil industry although it is desirable that
the brine pass through the ore itself rather than through the cracks of
the ore...." There is no further description on how the techniques common
to the oil industry can be applicable to increase permeability for leaching
of minerals but it appears that Stenger recognizes that the brine flow
for leaching should be through the ore itself rather than through the cracks
as for oil recovery.
Hurd uses a gaseous leaching solvent for in situ mining of subterranean
deposits. An acidic gas is passed into the ore deposit whereby the metallic
ions are made soluble in previously-added water, wetting the ore. This solution
is then recovered by water flooding. Here,as in Ortloff,and Stenger the ore
is used in its natural state so there is no great alteration of fracture zones
to contend with.
Lewis relates to a leaching method where a nuclear chimney located below water
table in a primary ore deposit serves as an in situ pressure vessel. He
introduces compressed oxidizing gas and lixiviant into the base of the rubble
chimney and recovers pregnant solution at the top of the rubble chimney.
Since both injection and recovery are in the rubble zone which is of
infinite permeability there would be no problem with clogging by the fines.
Parker relates to the in situ production of oil from oil shale by pyrolysis
with hot gases. Permeability of the shale around a nuclear produced chimney
is increased before retorting by pyrolyzing and melting the surface of the
fractures at a temperature of 1400 - 2000øF achieved by reverse combustion.
Oxygen is injected in wells at the periphery of the fractures extending out
from the fragmentation zone. This injected pressurized oxygen moves to the
chimney where reverse combustion takes place. The surfaces of the fractures
are melted to a slag which is left in place.
Walton discloses a method of recovering hydrocarbons from an oil shale
formation by in situ retorting.
Beard is for a method of recovering oil from a subterranean oil shale formation
by circulating a hot extractive fluid between two wells in an explosively
produced chimney in an oil shale formation.
None of the citations before us, which relate to the in situ recovery of hydro-
carbons from oil shale deposits, indicate any problem with flow restriction
due to the formation of fines or slimes. We believe the type of physical
reaction found in the recovery of oil from oil shale to be different from
that of the solvent reaction in the leaching recovery for mineral deposits.
It would appear that the reaction for leaching minerals will tend to produce
fines and slimes which would restrict lixiviant flow whereas the recovery of
oil from oil shale will not be subject to this additional factor of flow
restriction.
In the cited leaching patents to Ortloff,Stenger and Hurd the ore is not fractured
so they are not faced with the problem of fines restricting flow as is the case
in this application. Further the Lewis citation only utilizes the highly
rubblized zone of the nuclear chimney which will not cause any problem with
respect of fine clogging.
The applicant produces a fracture network in a deep rock ore body and injects
his leaching solution in the less severely fractured zone and recovers it in
the more severely fractured zone. There is no doubt that this type of flow
will tend to overcome the loss of fracture permeability caused by the
formation of fines and slimes during their leaching movement. We are satisfied
that there is present an indication of thought, design and a degree of
ingenuity which. in our view, constitutes a patentable advance in the art.
We will now consider the claims. Claim C9 is as follows:
A process for the in situ leaching of an ore body which has been
worked by detonating explosive charges in separate cavities therein
to produce in the ore body immediately adjacent to the site of
each detonation a fracture zone comprised of a most severely
fractured core portion surrounded by a less severely fractured
outer portion, comprising introducing lixiviant for the ore
into the ore body through a plurality of injection holes in the
less severely fractured portions and recovering pregnant leach
solution from the ore body through a plurality of recovery
holes in the most severely fractured portions.
The feature of introducing the lixiviant in the less severely fractured portion
and recovering the leach solution in the most severely fractured portion is
found in the claim. We consider this to define the scope of monopoly of the
invention commensurate with what we find is the invention described in the
specification taking into consideration what is taught by the cumulative
effect of the cited art.
We also find these features in the remainder of the conflict claims and they
too are considered allowable.
To summarize, we are satisfied that the conflict claims represent a patentable
advance in the art and we recommend that the decision of the examiner to
refuse claims C1 to C18 be withdrawn.
G. Asher S. Kot
Chairman Member
Patent Appeal Board, Canada
I concur with the findings of the Patent Appeal Board and return the
application to the examiner for the resumption of prosecution.
J.H.A. Gariepy
Commissioner of Patents
Dated at Hull, Quebec
this 15th day of January, 1979
Agent for Applicant
McCallum, Brooks & Co.
Box 660
Montreal, Que.