U.S. patent application number 13/038098 was filed with the patent office on 2011-07-21 for tagged propping agents and related methods.
This patent application is currently assigned to CARBO CERAMICS INC.. Invention is credited to Robert Duenckel, Thomas C. Palamara, Brett A. Wilson.
Application Number | 20110177984 13/038098 |
Document ID | / |
Family ID | 34959684 |
Filed Date | 2011-07-21 |
United States Patent
Application |
20110177984 |
Kind Code |
A1 |
Wilson; Brett A. ; et
al. |
July 21, 2011 |
Tagged Propping Agents and Related Methods
Abstract
A proppant particle comprising a sintered proppant composition
that comprises a non-radioactive, detectable tracer uniformly
distributed throughout a ceramic composition, wherein the tracer is
one or more tracer metal oxides and the tracer metals are selected
from a group consisting of lanthanides, strontium, barium, gallium,
germanium, tantalum, vanadium, and manganese.
Inventors: |
Wilson; Brett A.;
(Lafayette, LA) ; Duenckel; Robert; (Southlake,
TX) ; Palamara; Thomas C.; (Eufaula, AL) |
Assignee: |
CARBO CERAMICS INC.
Houston
TX
|
Family ID: |
34959684 |
Appl. No.: |
13/038098 |
Filed: |
March 1, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11667324 |
May 8, 2007 |
7921910 |
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PCT/US2005/009511 |
Mar 22, 2005 |
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13038098 |
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60559600 |
Apr 5, 2004 |
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Current U.S.
Class: |
507/219 ;
507/270 |
Current CPC
Class: |
C09K 8/80 20130101; E21B
43/267 20130101; E21B 47/11 20200501; C09K 8/805 20130101 |
Class at
Publication: |
507/219 ;
507/270 |
International
Class: |
C09K 8/80 20060101
C09K008/80 |
Claims
1. A proppant particle comprising a sintered proppant composition
that comprises a non-radioactive, detectable tracer uniformly
distributed throughout a ceramic composition, wherein the tracer is
one or more tracer metal oxides and the tracer metals are selected
from a group consisting of lanthanides, strontium, barium, gallium,
germanium, tantalum, vanadium, and manganese.
2. A proppant particle as set forth in claim 1 wherein the tracer
metals are selected from the group consisting of lanthanum, cerium,
strontium, barium, gallium, and germanium.
3. A proppant particle as set forth in claim 1 wherein the tracer
metals are selected from the group consisting of lanthanum and
cerium.
4. A proppant particle as set forth in claim 1 wherein the tracer
comprises a plurality of distinct tracer metal oxides.
5. A proppant particle as set forth in 1 wherein each tracer metal
oxide present in the proppant composition is at a concentration
that is at least about 0.005 percent by weight of the ceramic
composition.
6. A proppant particle as set forth in 1 wherein each tracer metal
oxide present in the proppant composition is at a concentration
that is at least about 0.01 percent by weight of the ceramic
composition.
7. A proppant particle as set forth in 1 wherein each tracer metal
oxide present in the proppant composition is at a concentration
that is at least about 0.02 percent by weight of the ceramic
composition.
8. A proppant particle as set forth in 1 wherein each tracer metal
oxide present in the proppant composition is at a concentration
that is at least about 0.03 percent by weight of the ceramic
composition.
9. A proppant particle as set forth in claim 1 wherein the tracer
is not present in the ceramic composition or is present in the
ceramic composition in a concentration that is less than about
1,000 ppm based on weight.
10. A proppant particle as set forth in claim 1 wherein the tracer
is present in the proppant particle at a concentration that is from
about 0.005 to about 0.5 percent by weight of the ceramic
composition.
11. A proppant particle as set forth in claim 1 wherein the tracer
is present in the proppant particle at a concentration that is from
about 0.01 to about 0.3 percent by weight of the ceramic
composition.
12. A proppant particle as set forth in claim 1 wherein the tracer
is present in the proppant particle at a concentration that is from
about 0.03 to about 0.2 percent by weight of the ceramic
composition.
13. A proppant particle as set forth in claim 1 wherein the tracer
is present in the proppant particle at a concentration that is from
about 0.05 to about 0.15 percent by weight of the ceramic
composition.
14. A proppant particle as set forth in claim 1 that is
substantially free of resin.
15. A proppant particle as set forth in claim 1 that consists
essentially of the non-radioactive, detectable tracer uniformly
distributed in the ceramic composition.
16. A proppant particle as set forth in claim 1 wherein the
non-radioactive, detectable tracer is in contact with the ceramic
composition.
17. A proppant particle as set forth in claim 1 wherein the
particle further comprises a coating material that at least
partially coats the composition.
18. A proppant particle as set forth in claim 17 wherein the
coating material is resin.
19. A proppant particle as set forth in claim 17 wherein the
particle is substantially free of resin.
20. A proppant particle consisting essentially of a sintered
proppant composition that consists essentially of a
non-radioactive, detectable tracer uniformly distributed in a
ceramic composition, wherein: (a) the tracer is one or more tracer
metal oxides and the tracer metals are selected from a group
consisting of lanthanides, strontium, barium, gallium, germanium,
tantalum, vanadium, and manganese; (b) each tracer metal oxide
present in the proppant composition is at a concentration that is
at least about 0.005 percent by weight of the ceramic composition;
(c) the tracer is present in the proppant particle at a
concentration that is from about 0.005 to about 0.5 percent by
weight of the ceramic composition; and (d) the tracer is not also
present in the ceramic composition or is present in the ceramic
composition in a concentration less than about 1,000 ppm based on
weight.
21. A proppant particle as set forth in claim 20 wherein the tracer
metals are selected from the group consisting of lanthanum, cerium,
strontium, barium, gallium, and germanium.
22. A proppant particle as set forth in claim 20 wherein the tracer
metals are selected from the group consisting of lanthanum and
cerium.
23. A proppant particle as set forth in claim 20 wherein each
tracer metal oxide present in the proppant composition is at a
concentration that is at least about 0.01 percent by weight of the
ceramic composition and the tracer is present in the proppant
particle at a concentration that is from about 0.01 to about 0.3
percent by weight of the ceramic composition.
24. A proppant particle as set forth in claim 20 wherein each
tracer metal oxide present in the proppant composition is at a
concentration that is at least about 0.03 percent by weight of the
ceramic composition and the tracer is present in the proppant
particle at a concentration that is from about 0.03 to about 0.2
percent by weight of the ceramic composition.
25. A proppant particle as set forth in claim 20 wherein the
ceramic composition is selected from the group consisting of
bauxite, kaolin, other clays, alumina, silica, and combinations
thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 11/667,324, filed May 8, 2007,
which was the National Stage of International Application No.
PCT/US2005/009511, filed Mar. 22, 2005, which claims the benefit of
U.S. Provisional Application No. 60/559,600, filed Apr. 5, 2004,
all of which are incorporated herein by reference in their
entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to propping agents, and more
particularly to propping agents that are labeled to enable
detection of the presence of the propping agent.
[0004] 2. Description of the Related Art
[0005] One of the problems encountered in attempting to maximize
recovery of hydrocarbons such as crude oil and natural gas from
underground formations is the entrapment of hydrocarbons within low
permeability formations. In fact, wells often contain large amounts
of the hydrocarbon entrapped in such low permeability rock
formations. The entrapped hydrocarbon, of course, does not flow
readily to the well bore.
[0006] Thus, subterranean formations that contain entrapped
hydrocarbons are often "fractured" to enhance the recovery of the
entrapped hydrocarbon from the formations. Fracturing typically
involves the injection of viscosified aqueous or hydrocarbon fluids
into the well bore at a rate and pressure in excess of the
formation stresses, thereby causing rock fatigue and opening or
inducing new fractures in the formation. Fractures are natural or
induced fissures or channels in the formation matrix. The injected
fluids usually contain a proppant material, commonly referred to as
a "propping agent" or simply a "proppant." Proppants are
particulate solids such as sand or ceramic particles, which may or
may not be coated with another material such as resin. After the
exerted injection pressure has been relieved, the fractures, which
would otherwise tend to close, are propped open by propping agent
left behind in the fracture. More conductive channels are thus
provided to allow the oil or gas to flow to the well bore after the
injection pressure is relieved.
[0007] Frequently, however, a substantial portion of the proppant
does not remain in the fractures, but flows back to the well bore.
Such proppant flowback not only results in inefficiency due to the
failure of the proppant that has flowed back to serve its purpose
of propping open the fractures, but also can cause serious wear in
the production equipment. In wells that contain more than one zone
to which proppant has been delivered it can be very difficult to
determine which of the zones may be the source of the proppant
flowback problem. Therefore, the proppant flowback problem is
particularly troublesome in such wells.
[0008] Some techniques have been developed which provide a means to
identify the zone or zones that are the source of the proppant
flowback. Generally, such techniques involve tagging the proppants
with a tracer or marker that can be detected by some standard
method. According to such techniques, the proppant delivered to
each zone is tagged with a tracer distinct from the tracers
associated with the other zones. By detecting which tracer is
present in the proppant that has flowed back from the formation, it
can then be determined the zone from which the proppant flowed.
[0009] However, none of the techniques so far developed are
entirely satisfactory. For example, radioactive tracers have been
used, but radioactive materials can have a short shelf-life and may
be difficult to handle and can be hazardous to the environment.
U.S. Pat. No. 6,691,780 discloses a technique for tagging proppants
with non-radioactive materials, but that technique employs a tag
within a resin coating over the proppant. Thus, the technique is
limited to resin-coated proppants and is susceptible to loss of the
tags if the coating is lost by friction, heat or other means.
[0010] As a result, superior tagged proppants, and methods of
producing them, that avoid the aforementioned problems are still
needed. In particular, it is desired that the tagged proppant be
non-radioactive and be tagged in a way that is not susceptible to
loss of the tracer by friction and the like. Moreover, because the
proppants must be suspended in the carrier fluid and must withstand
substantial forces to prop open fractures, and because the purpose
of the proppants is to increase flow-through or "conductivity" of
fluids, the tagged proppant should maintain the strength and
density of the untagged proppant, and should provide at least a
similar conductivity (that is, fluid flow-through) as does the
untagged proppant.
SUMMARY OF THE INVENTION
[0011] Briefly, therefore, the present invention is directed to a
novel proppant composition comprising a non-radioactive, detectable
tracer at least partially embedded in a ceramic composition.
[0012] The present invention is also directed to a novel method for
producing a particle comprising a non-radioactive, detectable
material and a ceramic material, the method comprising
agglomeration of granules of the ceramic material and granules of
the non-radioactive, detectable material to produce the particle by
compression.
[0013] The present invention is also directed to a novel method for
producing a substantially resin-free particle that need not be
resin-coated, but may be (if so desired) at least partially coated
with resin, comprising agglomeration of granules of the ceramic
material and granules of the non-radioactive, detectable material
to produce the substantially resin-free particle comprising the
non-radioactive, detectable material at least partially embedded in
the ceramic material. If a coating is desired, the substantially
resin-free particle thus formed may then at least partially coated
with a coating material.
[0014] The present invention is also directed to a novel method for
tracking the backflow of proppants in a fractured subterranean
formation into which a plurality of such tagged proppant
composition particles have been introduced. According to the
method, a sample of the backflow is analyzed by detecting for
presence of the tracer in the sample.
[0015] Among the several advantages found to be achieved by the
present invention, therefore, may be noted the provision of a tag
that is integral with the ceramic material rather than associated
with the ceramic material by means of a coating; the provision of a
proppant that bears such a tag; the provision of such proppant that
maintains desirable strength, density and conductivity despite the
presence of the tag; the provision of a method for preparing such
tagged proppants; and the provision of a method for tracking
particulate flowback with such proppants.
[0016] Further features and advantages of the present invention, as
well as the structure and operation of various embodiments of the
present invention, are described in detail below with reference to
the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a graph of the conductivity for an untagged
proppant compared to that of the proppant tagged with a tracer "A"
and that of the proppant tagged with a tracer "B," wherein tracer
"A" is lanthanum oxide and wherein tracer "B" is cerium oxide.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] In accordance with the present invention, it has been
discovered that, surprisingly, a non-radioactive tracer may be
embedded in a ceramic proppant without diminishing the strength or
conductivity of the proppant or undesirably altering its density.
In fact, the proppants can even be tagged according to the methods
of this invention to allow different versions of the tagged
proppant with identical strengths and densities to be
distinguished. Moreover, because the tag is embedded in the
ceramic, it is not prone to wearing or flaking off of the proppant
due to friction, heat or other causes typically encountered by the
proppant. And, because the tracers of the subject invention do not
break down like radioactive tracers, they are not hazardous and
have virtually unlimited shelf-lives.
[0019] While particles comprising or derived from bauxite (low
grade or "true" bauxite), kaolin or other particles comprising one
or more clays, alumina, silica and mixtures of any of the foregoing
have been found particularly suitable for tagging according to the
preparation techniques of the present invention, it is believed
that any ceramic proppant may be tagged according to the
preparation techniques of this invention. Many ceramic materials
suitable for proppants are well known. For example, Lunghofer U.S.
Pat. No. 5, 120,455, Fitzgibbon U.S. Pat. Nos. 4,427,068 and
4,879,181, and patents cited in each of the foregoing patents,
identify a variety of proppants and proppant materials, and are
incorporated herein by reference. The proppant materials themselves
will be referred to herein as "ceramic compositions" in contrast
and distinction to the tracer that is applied thereto.
[0020] It is believed that the tagged proppant of this invention
made be prepared by any standard pelletizing or tabletting
technique well known in the proppant manufacture, pelletizing and
tabletting arts for agglomerating a powder into a proppant, pellet
or tablet, but wherein the powder is a mixture of ceramic
composition and tracer, as discussed below, and the resulting
particle, pellet or tablet is of appropriate size, shape, strength
and density as is well known for suitable proppants. Thus, for
example, the tagged proppant may be prepared by continuous spray
atomization, spray fluidization, spray drying, or compression. An
example of a compression technique is that has been formed to the
yield excellent tagged proppants is described in U.S. Pat. No.
4,879,181 for untagged proppants, except that alternative ceramic
compositions, as noted above, besides the calcined clay, alumina,
bauxite and mixtures thereof may be employed as the ceramic
composition in the starting ingredients and a non-radioactive,
detectable tracer is mixed with the ceramic starting ingredients,
and it is this resulting mixture that is milled, homogenized and
pelletized by compression.
[0021] The tracer may be any non-radioactive material that is
detectable in the proppant, particularly detection by methods that
can determine the chemical compositions of samples. For instance,
the tracer material may be one that is detectable by
inductively-coupled plasma (ICP), X-ray fluorescence, or
proton-induced X-ray emission (PIXE). However, other methods that
can detect the presence of the tracer, such as the chemical
analysis, may be used. Techniques for detecting the presence of
certain materials by such methods are well known. Thus, U.S. Pat.
No. 6,691,780 describes a method to detect the presence of a tagged
proppant by ICP. While the proppant of U.S. Pat. No. 6,691,780 is
tagged with a tracer-containing resin coating, the ICP detection
technique of that patent is applicable to the tagged proppants of
the present invention as well. According to the ICP method of U.S.
Pat. No. 6,691,780: [0022] an aqueous sample is nebulized within an
ICP spectrophotometer and the resulting aerosol is transported to
an argon plasma torch located within the ICP spectrophotometer. The
ICP spectrophotomer measures the intensities of element-specific
atomic emissions produced when the solution components enter the
high-temperature plasma. An on-board computer within the ICP
spectrophotomer accesses a standard calibration curve to translate
the measured intensities into elemental concentrations. ICP
spectrophotometers for use according to the ICP method are
generally commercially available from the Thermo ARL business unit
of Thermo Electron Corporation, Agilent Technologies and several
other companies.
[0023] As explained below, other detection techniques, and so
tracers, such as noted in U.S. Pat. No. 6,691,780 may be applicable
as well, so long as the detection is not dependent on the tracer
being exposed in an external coating rather than embedded within
the ceramic.
[0024] It is also preferred that the material employed as a tracer
not be one that is otherwise present in the ceramic composition or
at least is present in the composition in a concentration less than
about 1,000 ppm based on weight. This is desirable to avoid false
concentration measurements resulting from interference from the
material present in the ceramic composition and, in the case of
multi-zone formations, to avoid false measurements resulting from
the presence of the material from proppants flowing back from other
zones. Generally, it is believed that the tracer may be any
substance, particularly a solid, that is detectable by chemical
analysis at a concentration in the proppant (especially when the
proppant is present in the sample to be tested at the lowest
concentration at which the proppant desired to be detected) that
does not degrade the physical properties of the proppant with
respect to density, strength and conductivity.
[0025] Based on such considerations, ceramic forms of certain
metals have been found to be especially good tracer materials.
Examples of such preferred metals include the lanthanide series of
rare earth metals, strontium, barium, gallium, germanium, and
combinations thereof, particularly, lanthanum, cerium, strontium,
barium, gallium, germanium, tantalium, zirconium, vanadium,
chromium, manganese, and combinations thereof, especially
lanthanum, cerium, and combinations thereof. Although the metals
may be employed in elemental form, some metals in their metallic
form are hazardous and it is contemplated that more commonly
compounds containing the metals, such as the ceramic forms (oxides,
hydroxides and carbonates) of the metals will be used. Thus,
references herein to the metals themselves shall be taken in their
broadest sense and so include the molecular, ionic, and
mineralogical forms of the metals. Of course, for multi-zone
applications where it is desirable to distinguish the zones from
which proppant has flowed back, it is desirable for the tracers to
be not just detectable, but detectable in a way that one type can
be distinguished from the others used for other zones.
[0026] Moreover, combinations of types of tracers are particularly
useful for application to subterranean formations in which the
number of zones in the formation exceeds the number of different
available types of tracers. In such situations, a plurality of
different types of tracers may be combined to produce a distinct
tracer defined by the combination. By way of illustration, if
sixteen different types of tracers are available, four of the types
of tracers may be designated, say, A-D, while the remaining eleven
may be designated, say, 1-12. By pairing the tracer types,
forty-eight different tracers in the form of tracer combinations
A1, A2, . . . B1, B2, and so forth can be used to distinguish
forty-eight different zones. As is now apparent, by combining the
tracer types in different ways, many different zones may be
distinguished with a limited number of types of tracers.
[0027] Certain techniques can be employed to avoid confusion that
might otherwise arise from mixing tracers. For example, if the
backflow contains tracers A1, A2, B1 and B2, it may be difficult
from the detection of tracer types A, B, 1 and 2 to determine how
much of the tracer type A is from the zone associated with Al and
how much is associated with A2. The presence of additional amounts
of tracer types 1 and 2 from the tracers B1 and B2 might interfere
or complicate the ability to distinguish between A1 and A2 base on
the amounts of tracer types 1 and 2 detected. However, the tracer
combinations may be assigned to disparate zones that would be
unlikely to intermingle backflows, thereby avoiding such
overlaps.
[0028] The amount of tracer that is desirable to mix with the
ceramic composition depends on a variety of circumstances.
Nevertheless, the concentration of the tracer in the proppant
should be sufficient so that its presence in the backflow will be
detectable by the selected detection method when the amount of
proppant in the backflow is at a level at which detection of its
presence is desired. It also is desired that the concentration of
the tracer in the proppant not be substantially above that level,
as the use of more tracer can result in higher cost and, in some
circumstances, might degrade the desirable qualities of the
proppant. Generally, tracer concentrations of at least about 0.03%
by weight are desired for convenient detection by conventional
detection techniques, while in some situations tracer
concentrations in excess of 0.15%, and especially in excess of
0.2%, by weight have been found to change the firing temperature
significantly and may even degrade the properties of lightweight
proppants. Thus, generally, it has been found that tracer
concentrations of from about 0.005 to about 0.5, preferably about
0.01 to about 0.3, more preferably from about 0.03 to about 0.2,
even more preferably from about 0.03 to about 0.15, such as from
about 0.05 to about 0.15, typically about 0.13, percent by weight,
based on the weight of the ceramic composition, are particularly
useful. In situations in which a combination of tracer types is
used, each type should be in a concentration sufficient to be
detectable at the level of proppant desired to be detected.
Generally, in such situations, each type of tracer should be
present in a concentration of at least about 0.005 percent,
preferably at least about 0.01 percent, more preferably at least
about 0.02, and even more preferably at least about 0.03 percent by
weight based on the weight of the ceramic composition. In any
event, however, the minimum concentration depends on the
sensitivity of the method of chemical analysis and so it is
possible that concentrations even lower than 0.01 percent may be
used with some analytical techniques. For example, neutron
activation analysis (NAA) is reported to be able to have detection
limits of 1-5 ppm (or 0.0001-0.0005 wt %) for La.sub.2O.sub.3 and
CeO.sub.2, which would allow detection (and so concentration
levels) in the range of 0.001 wt %.
[0029] As noted above, the tagged proppant may be prepared in the
manner described in U.S. Pat. No. 4,879,181 for untagged proppants,
except that, in the present invention, the tracer is included as
part of the starting proppant ingredients. Therefore, it is
contemplated that tagged proppants according to the subject
invention will be prepared typically by agglomeration of granules
of the ceramic material and granules of the non-radioactive,
detectable material to produce the particle, whether by compression
or some other agglomeration means. For example, a mixture of fine
grains of the ceramic composition and of the tracer can be
compressed together to form a proppant particle. Thus, briefly but
in more detail, the tagged proppant may be prepared as follows.
[0030] Starting materials for the ceramic composition (such as
calcined clay and alumina, bauxite, or mixtures thereof or other
ingredients as discussed above as suitable proppant materials), may
be added to a high intensity mixer, such as a ball mill, in a
predetermined ratio with the tracer in a concentration as discussed
above. The additives to the mixer then may be milled to a fine
powder, which is then stirred to form a dry homogeneous particulate
mixture. For example, the powder may be stirred with a stirring or
mixing device that is obtainable from Eirich Machines, Inc., known
as an Eirich Mixer. Similar mixing equipment is available from
other manufacturers. While the mixture is being stirred, sufficient
water to cause formation of composite, spherical pellets from the
ceramic powder mixture may be added. The resulting pellets may be
dried and the dried pellets then fired at sintering temperature for
a period sufficient to enable recovery of sintered, spherical
pellets having an apparent specific gravity of, for instance,
between 2.70 and 3.60 and a bulk density of, for instance, from
about 1.0 to about 2.0 grams per cubic centimeter. The specific
time and temperature to be employed is, of course, dependent on the
starting ingredients and is determined empirically according to the
results of physical testing of pellets after firing. The resulting
pellets may be screened to produce proppants within a size range
of, for example, about 40 mesh to about 20 mesh, from about 16 mesh
to about 20 mesh, from about 30 mesh to about 50 mesh, from about
30 mesh to about 60 mesh, or from about 16 mesh to about 30 mesh.
More specific details of this process are discussed in U.S. Pat.
No. 4,879,181.
[0031] Other known methods of preparing proppants may be modified
similarly to prepare the tagged proppants of the subject invention.
Thus, for example, it is believed that alternative methods of
preparation may be according to similarly modified processes
described in U.S. Pat. No. 4,440,866 and referred to in U.S. Pat.
No. 5,120,455. These patents, including the patents referred to in
U.S. Pat. No. 5,120,455, are incorporated herein by reference.
[0032] The resulting tagged proppant, therefore, comprises a
non-radioactive, detectable tracer at least partially embedded in a
ceramic composition. The tagged proppant may be prepared from a
mixture of powdered ceramic composition and powdered tracer and so
comprises not a discrete tracer-containing coating over a
tracer-free ceramic particle, but a mixture--an agglomeration--of
the ceramic composition and the tracer. In fact, at least some of
the tracer is at least partially--and may be completely surrounded
by ceramic composition. Thus, the tracer does not tend to rub off
of the proppant. And surprisingly, it has been found that tagging
the proppants according to the method of the present invention does
not degrade the strength, density or conductivity of the proppants.
Moreover, because the tracer of the proppant particle is thus in
contact with the ceramic composition, in fact, adhered directly to
the ceramic composition, it need not be applied by coating the
particle with a resin containing the tracer. Although the proppant
composition may be substantially or completely free of resin, it
may also be coated partially or completely with a coating material
such as resin if so desired, and the coating may be substantially
or completely free of the tracer. As discussed above, the tracer
may comprise a plurality of distinct types of tracers, generally
distinct types of tracer metals.
[0033] The tagged proppant of the present invention may be used in
place of prior art proppants, and particularly in place of prior
art tagged compositions to determine whether and how much proppant
is flowing back from one or a plurality of zones within a
subterranean formation. In fact, the fact that the tagged proppants
of the present invention are not radioactive, are strong, need not
bear a resin-coating, and so forth, may permit employment of such
proppants in situations in which conventional proppants are not
useful or practical. Moreover, in the case of multiple zones, it is
possible, with the tagged proppants of the present invention, to
identify which zone or zones are associated the flowback.
[0034] In short, a subterranean formation having one or multiple
zones may be treated and backflow from the zone(s) tracked by
introducing tagged proppant into a well bore in the formation, for
example, by way of a fracturing fluid to fracture the well by
standard techniques except for the replacement of convention
(tagged or untagged) proppants with the tagged proppants of the
present invention. In the case of a multi-zone formation, a
plurality of types of tagged proppants, each type of proppant
tagged with a tracer distinguishable from tracers of the other
types of tagged proppants, may be employed by directing each of the
types of proppants to a different zone. As explained above, a
plurality of tracers may be a plurality of combinations of types of
tracers. Flowback from one or more of the zones may then be
analyzed, such as by collecting at least a portion of the flowback,
and the proppants (and so zones) associated with the flowback
identified by detecting the tracer(s) therein.
[0035] The following examples describe the preferred embodiments of
the invention. Other embodiments within the scope of the claims
herein will be apparent to one skilled in the art from
consideration of the specification or practice of the invention as
disclosed herein. It is intended that the specification together
with the examples, be considered exemplary only, with the scope and
spirit of the invention being indicated by the claims which follow
the examples. Percentages identified in the examples are based on
weight.
EXAMPLE 1
[0036] Tests were carried out to investigate whether low addition
levels of tracers to a bauxite-based proppant would change the
final physical properties required of a high strength proppant. Two
different markers (lanthanum oxide and cerium oxide) were lab
tested. Batches of the untagged proppant were made in the lab with
and without marker additions. Testing of the resulting bulk
density, apparent specific gravity, crush at 15 kpsi (103.5 MPa),
and conductivity showed no degradation in physical properties for
batches with either of the two marker additions compared to the
batch without a marker addition.
EXAMPLE 2
[0037] Because lab produced proppant samples can have improved
properties due to the increased control of the process that is
possible in a lab setting with high precision lab equipment,
control batches of the proppant of Example 1, above, without any
tracer additions were made along with batches with tracer additions
to give a more direct comparison of properties of the proppant.
[0038] One batch of the bauxite-based raw material was ground in
the lab without any tracers. Additional batches were blended with a
tracer and then milled in the lab to make a homogeneous blend. Each
batch was made into pellets and sintered in a lab kiln. Each batch
of sintered pellets was sized to the following sieve
distribution:
TABLE-US-00001 U.S. % Mesh Retained +16 0 -16 +20 3.6 -20 +25 34.7
-25 +30 47.0 -30 +35 14.0 -35 +40 0.7 -40 +50 0 -50 0
Density, strength, and conductivity testing was performed on each
batch according to API specifications. Specific gravity was
measured using a Micromeritics Helium Pycnometer. The following
table shows the density and crush strength for the proppant with
tracer A (lanthanum oxide) for two different trials at a
concentration level of 0.03% and the proppant with tracer B (cerium
oxide) at a concentration level of 0.03%.
TABLE-US-00002 Control Tracer A Tracer A Tracer B Batch 0.03% 0.03%
0.03% Specific 3.64 3.65 3.64 3.65 Gravity B.D. 1.99 2.02 2.02 1.99
(g/cc) A.S.G. 3.65 3.67 3.66 3.67 Crush @ 2.4 2.9 2.2 3.0 15 kpsi
(103 MPa) (%)
The conductivities of all four batches of the proppant are shown in
FIG. 1. The density and crush strength data and conductivity data
are within the experimental error for each test and consequently
demonstrate that there is no measurable degradation in the
properties of the proppant when either tracer A or tracer B are
added in a concentrations of 0.03%.
EXAMPLE 3
[0039] Samples were sent to two outside labs for X-Ray Fluorescence
(XRF) and Inductively Coupled Plasma (ICP) analysis. Redundant
samples were sent to each lab and all samples were identified only
with a generic, sequential identification number (for XRF 001 . . .
015 and for ICP 001 . . . 010). XRF & ICP on the control
batches measured the background concentration (in wt %) of tracers
A and B as described in Example 2, above. XRF and ICP analyses of
the batches with tracer A or B, measured the total concentration
(in wt %) of tracers A and B.
[0040] For the tagged batches with markers A or B added at a
concentration level of 0.03 wt %, the resulting chemistry measured
via XRF was: [0041] Background concentration of tracer A in six
control batch samples: 0.00% .+-.0.01 [0042] Total measured
concentration of tracer A in five marked batch samples:
0.02%.+-.0.01 [0043] Background concentration of tracer B in six
control batch samples: 0.01% .+-.0.01 [0044] Total measured
concentration of tracer B in three marked batch samples:
0.04%.+-.0.01
[0045] For the tagged batches with tracers A or B added at a
concentration level of 0.03%, the resulting chemistry measured via
ICP was: [0046] Background concentration of tracer A in four
control batch samples: 0.003% .+-.0.001 [0047] Total measured
concentration of tracer A in four marked batch samples: 0.032%
.+-.0.001 [0048] Background concentration of tracer B in four
control batch samples: 0.030% .+-.0.010 [0049] Total measured
concentration of tracer B in two marked batch samples: 0.051%
.+-.0.001
[0050] Both XRF and ICP analysis was able to detected the presence
of the tracers within at least 0.01%.
[0051] All references cited in this specification, including
without limitation all journal articles, brochures, manuals,
periodicals, texts, manuscripts, website publications, and any and
all other publications, are hereby incorporated by reference. The
discussion of the references herein is intended merely to summarize
the assertions made by their authors and no admission is made that
any reference constitutes prior art. Applicants reserve the right
to challenge the accuracy and pertinence of the cited
references.
[0052] In view of the above, it will be seen that the several
advantages of the invention are achieved and other advantageous
results are obtained.
[0053] As various changes could be made in the above methods and
compositions without departing from the scope of the invention, it
is intended that all matter contained in the above description and
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
EXAMPLE 4
[0054] Each of several samples of ground Comalco Bauxite were
blended with no (control) or a particular rare earth additive or
other ceramic additive not found in the bauxite in appreciable
quantities in a Lab Eirich mixer for ten minutes. The blends were
then jet milled to reduce particle size to a powder and to mix the
components intimately. The powders were pelletized to green pellets
and sieved to the -16 to +40 sieve range. Two samples of pellets
formed from each blend were sent to a lab for analysis by
inductively coupled plasma (ICP). On other green pellets from each
blend, three boats of each were sieved to the -16 to +40 sieve
range, fired to peak temperature (about 1500.degree. C.) at
960.degree. C/hr. with a hold of about thirty minutes.
[0055] The ICP analysis showed that the presence of the taggant of
concentration higher than that inherently present (that is, the
background level of the taggant in untreated proppant as
represented by the control) could be detected. In the following
table, the first number in the column labeled "Background Level of
the Taggant Composition" is the concentration (in wgt. %) of the
taggant composition measured in the untreated control for samples
in the form of green pellet samples and the second number is for
samples in the form of dust. The first number in the column labeled
"Measured Level of Taggant" is the concentration (in wgt. %) of the
taggant composition measured in the proppant to which the taggant
has been added is for samples in the form of green pellet samples
and the second number is for samples in the form of dust. The
column labeled "Difference" is the difference between the average
concentration of taggant measured for taggant composition and the
average background concentration of the taggant composition
measured in control samples. For each tagged proppant, 0.1% taggant
was added, except for ZrSiO.sub.4, in which case, 0.25% was
added.
TABLE-US-00003 Background Level of Measured Level Taggant Taggant
Composition of Taggant Difference ZrSiO.sub.4 0.18, 0.20 0.36, 0.36
0.15 ZnO 0.001, 0.001 0.092, 0.091 0.085 SrO(CO.sub.2) 0.002, 0.002
0.10, 0.11 0.10 Nd.sub.2O.sub.5 0.002, 0.002 0.12, 0.11 0.11
Pr.sub.6O.sub.11 0.002, 0.002 0.10, 0.099 0.98 MnO 0.015, 0.018
0.10, 0.097 0.083 CuO 0.002, 0.001 0.10, 0.098 0.097
Cr.sub.2O.sub.3 0.002, 0.042 0.15, 0.15 0.12 NiO 0.001, 0.001 0.95,
0.10 0.096 V.sub.2O.sub.5 0.014, 0.009 0.12, 0.13 0.12
Co.sub.3O.sub.4 0.004, 0.003 0.13, 0.14 0.13 Sb.sub.2O.sub.3 0.002,
0.002 0.086, 0.092 0.087
[0056] Similar tests were conducted on other samples comparing %
added La.sub.2O.sub.3 with the results of the % La.sub.2O.sub.3
measured, compared to controls in which no La.sub.2O.sub.3 was
added, as follows:
TABLE-US-00004 % La.sub.2O.sub.3 Measured % La.sub.2O.sub.3 Added
In Control In Tagged Proppant 0.15 0.004 0.11 0.15 0.004 0.12 0.03
under 0.005 0.02 0.15 under 0.005 0.018 0.03 -- 0.017 0.15 -- 0.018
0.03 under 0.005 0.02 0.15 under 0.005 0.018 0.15 -- 0.024 0.15 --
0.024 0.15 -- 0.11 0.15 -- 0.10
The tests were repeated for CeO.sub.2, with the following
results:
TABLE-US-00005 % La.sub.2O.sub.3 Measured % La.sub.2O.sub.3 Added
In Control In Tagged Proppant 0.03 0.010 0.041 0.03 0.019 0.039
0.03 -- 0.041 0.15 -- 0.13 0.03 -- 0.12
Further tests were carried out using X-Ray Fluorescence (XRF) with
the following measured La.sub.2O.sub.3 concentrations for no
additive and for 0.03% and 0.15% La.sub.2O.sub.3 and CeO.sub.2
added:
La.sub.2O.sub.3:
TABLE-US-00006 [0057] Control 0.03% La.sub.2O.sub.3 Added 0.15%
La.sub.2O.sub.3 Added Under 0.005 0.020 0.11 Under 0.005 0.018 0.10
Under 0.005 0.017 Under 0.005 0.018 Under 0.005 0.020 Under 0.005
0.018 Under 0.005 0.024 Under 0.005 0.024
CeO.sub.2:
TABLE-US-00007 [0058] Control 0.03% CeO.sub.2 Added 0.15% CeO.sub.2
Added 0.008 0.010 0.13 0.008 0.039 0.12 0.011 0.041
Further tests were carried out using ICP with the following
measured concentrations for no additive and for 0.03% and 0.15%
La.sub.2O.sub.3 and CeO.sub.2 added:
La.sub.2O.sub.3:
TABLE-US-00008 [0059] Control 0.03% La.sub.2O.sub.3 Added 0.15%
La.sub.2O.sub.3 Added 0.003 0.032 0.14 0.003 0.032 0.14 0.003 0.032
0.003 0.032 0.003 0.027 0.003 0.030
CeO.sub.2:
TABLE-US-00009 [0060] Control 0.03% CeO.sub.2 Added 0.15% CeO.sub.2
Added 0.028 0.051 0.16 0.030 0.050 0.16
[0061] The resulting pellets also were analyzed for bulk density by
the standard ANSI test, apparent specific gravity by the standard
API test, specific gravity by Helium Picnometer, and crush strength
at 15 ksi (103 MPa) by the standard API test. The following results
were obtained, where the measured content of the taggant was
determined by ICP:
TABLE-US-00010 Short Term Conductivity (Darcy-ft) Bulk 2 ksi 4 ksi
6 ksi 8 ksi 10 ksi 12 ksi Measured Content of Taggant Taggant
Density Crushed Specific Gravity (13.8 (27.6 (41.4 (55.2 (69 (82.8
In Added (gm/cc) (%) Apparent Actual MPa) MPa) MPa) MPa) MPa) MPa)
Control In Taggant Proppant Control 1.99 2.4 3.65 3.6422 9.26 7.93
7.05 6.25 5.58 4.96 N/A N/A 0.03% CeO.sub.2 1.99 3.0 3.67 3.653
9.53 7.78 6.84 6.15 5.25 4.88 0.026 0.0505 0.15% CeO.sub.2 2.01
3.42 3.60 3.6564 9.17 8.04 7.22 6.10 5.33 4.75 0.15% CeO.sub.2 2.01
3.82 3.60 3.6564 0.15% CeO.sub.2 2.01 4.22 3.61 3.6667 0.15%
CeO.sub.2 2.04 5.16 3.64 3.6581 0.15% CeO.sub.2 2.04 2.18 3.63
3.6667 10.74 9.07 7.74 6.92 6.30 5.47 0.026 0.160 0.15% CeO.sub.2
2.02 4.35 3.64 3.6453 0.15% CeO.sub.2 2.02 3.61 3.61 3.6352 0.03%
La.sub.2O.sub.3 2.02 2.9 3.67 3.6488 9.91 8.61 7.43 6.67 6.10 5.31
0.003 0.031 0.15% La.sub.2O.sub.3 2.05 2.96 3.60 3.6638 8.77 6.83
5.91 5.45 4.82 4.38 0.15% La.sub.2O.sub.3 2.05 3.75 3.55 3.6678
0.15% La.sub.2O.sub.3 2.06 3.93 3.64 3.6588 0.15% La.sub.2O.sub.3
2.03 3.00 3.64 3.6577 10.42 7.80 6.85 6.27 5.44 4.77 0.003 0.140
0.15% La.sub.2O.sub.3 2.06 3.38 3.66 3.6547 0.15% La.sub.2O.sub.3
2.06 2.75 3.64 3.6446 Control 2.04 3.77 3.64 3.6486 Control 2.00
2.83 3.60 3.6365 Control 1.97 3.09 3.59 3.6251 8.90 7.66 6.73 6.07
5.48 4.92 N/A N/A 0.10% ZnO 2.04 3.77 3.64 3.6603 9.60 8.19 7.35
6.65 5.91 5.33 0.007 0.092 0.10% ZnO 2.01 3.82 3.60 3.6538 0.25%
ZrSiO.sub.4 2.04 4.17 3.65 3.6619 0.25% ZrSiO.sub.4 2.02 3.61 3.67
3.6587 9.40 8.08 7.38 6.54 5.74 5.24 0.21 0.36 0.25% ZrSiO.sub.4
2.02 3.81 3.64 3.6551 0.10% SrO(CO.sub.2) 2.05 2.96 3.65 3.6488
8.61 7.30 6.64 5.90 5.40 4.68 0.002 0.105 0.10% SrO(CO.sub.2) 2.02
3.41 3.61 3.6471 0.10% Nd.sub.2O.sub.3 2.01 3.82 3.63 3.6689 9.08
7.73 6.67 5.94 5.13 4.59 0.002 0.115 0.10% Nd.sub.2O.sub.3 2.02 4.0
3.65 3.6639 0.10% Pr.sub.6O.sub.11 2.04 3.17 3.65 3.6591 8.78 7.72
6.82 6.04 5.48 4.64 0.002 0.100 0.10% Pr.sub.6O.sub.11 2.03 3.59
3.64 3.6577 0.10% MnO.sub.2 2.04 2.40 3.64 3.6534 0.10% MnO.sub.2
2.03 2.19 3.64 3.6458 9.46 8.21 7.31 6.48 5.81 5.41 0.016 0.099
0.10% Red CuO.sub.2 2.03 1.99 3.64 3.6644 9.65 8.72 7.58 6.85 6.35
5.67 0.002 0.099 0.10% Red CuO.sub.2 2.04 2.38 3.64 3.6574 0.10%
Cr.sub.2O.sub.3 2.06 2.95 3.65 3.6623 9.28 7.97 7.26 6.54 5.86 5.34
0.034 0.15 0.10% Cr.sub.2O.sub.3 2.05 2.96 3.63 3.6643 0.10%
Cr.sub.2O.sub.3 2.03 3.78 3.63 3.653 Control 1.96 3.63 3.59 3.6047
9.33 8.14 7.29 6.49 5.68 5.07 N/A N/A Control 1.95 3.94 3.56 3.5946
0.10% Ni.sub.2O.sub.3 2.02 1.60 3.64 3.6522 10.26 8.64 7.57 7.04
6.05 5.48 0.002 0.096 0.10% Ni.sub.2O.sub.3 2.02 3.60 3.60 3.6487
0.10% Ni.sub.2O.sub.3 2.01 2.21 3.56 3.6440 0.10% V.sub.2O.sub.5
2.00 2.73 3.64 3.6474 0.10% V.sub.2O.sub.5 1.99 2.77 3.61 3.636
0.10% V.sub.2O.sub.5 1.99 2.42 3.60 3.6315 8.85 7.70 6.85 6.06 5.44
4.76 0.009 0.116 0.10% Co.sub.2O.sub.3 2.06 2.55 3.59 3.6548 0.10%
Co.sub.2O.sub.3 2.04 2.42 3.61 3.6436 Co.sub.3O.sub.4 0.10%
Co.sub.2O.sub.3 2.03 2.06 3.57 3.6402 9.78 8.26 7.55 6.73 6.13 5.36
0.004 0.131 0.10% Sb.sub.2O.sub.3 2.02 3 3.65 3.6503 9.11 7.67 6.95
6.26 5.69 5.10 0.002 0.087 0.10% Sb.sub.2O.sub.3 1.98 3.1 3.56
3.6325 0.10% Sb.sub.2O.sub.3 1.98 3.67 3.56 3.6325
EXAMPLE 5
[0062] The process of Example 4 was repeated, but with kaolin-based
pellets instead of bauxite-based pellets. The results were as
follows:
TABLE-US-00011 Short Term Conductivity (Darcy-ft) Bulk 2 ksi 4 ksi
6 ksi 8 ksi 10 ksi 12 ksi Measured Content of Taggant Taggant
Density Crushed Specific Gravity (13.8 (27.6 (41.4 (55.2 (69 (82.8
In Added (gm/cc) (%) Apparent Actual MPa) MPa) MPa) MPa) MPa) MPa)
Control In Taggant Proppant Control 1.53 7.90 2.75 2.7649 Control
1.56 5.70 2.79 2.7899 8.71 7.04 5.61 4.17 3.01 2.12 0.004 N/A
Control 1.55 7.83 2.80 2.7868 0.15% La.sub.2O.sub.3 1.54 8.92 2.77
2.7794 0.15% La.sub.2O.sub.3 1.57 6.96 2.78 2.7807 9.65 7.95 6.29
4.48 3.26 2.22 0.004 0.115 0.15% La.sub.2O.sub.3 1.55 7.45 2.78
2.7842 0.15% La.sub.2O.sub.3 1.55 10.23 2.79 2.7704
* * * * *