U.S. patent application number 11/237074 was filed with the patent office on 2006-04-20 for process for downhole heating.
This patent application is currently assigned to Baker Hughes Incorporated. Invention is credited to Ronald G. Bland, Marvin L. Pless, John B. Trenery, David B. Young.
Application Number | 20060081374 11/237074 |
Document ID | / |
Family ID | 36143033 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060081374 |
Kind Code |
A1 |
Bland; Ronald G. ; et
al. |
April 20, 2006 |
Process for downhole heating
Abstract
Neutral electrolytes, relatively neutral electrolytes, metal
oxides, metal hydroxides and/or organic exothermic hydration
chemicals may be hydrated with water at a controlled location in a
subterranean formation to generate sufficient exothermic heat to at
least soften and possibly melt and flow bitumen at or near the
location. This controlled and localized heating would be useful in
drilling through relatively thick bitumen or "tar" beds. In one
non-limiting embodiment the exothermic hydration reaction does not
generate appreciable amounts of gas. Alternatively, the exothermic
reaction may be used to liberate hydrocarbons from gas hydrates in
an embodiment where the evolution of gas is acceptable.
Inventors: |
Bland; Ronald G.; (Houston,
TX) ; Young; David B.; (Conroe, TX) ; Pless;
Marvin L.; (Katy, TX) ; Trenery; John B.;
(Sugar Land, TX) |
Correspondence
Address: |
MADAN, MOSSMAN & SRIRAM, P.C.
2603 AUGUSTA
SUITE 700
HOUSTON
TX
77057
US
|
Assignee: |
Baker Hughes Incorporated
Houston
TX
|
Family ID: |
36143033 |
Appl. No.: |
11/237074 |
Filed: |
September 28, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60614129 |
Sep 29, 2004 |
|
|
|
Current U.S.
Class: |
166/300 ;
166/302 |
Current CPC
Class: |
E21B 43/24 20130101;
E21B 36/008 20130101 |
Class at
Publication: |
166/300 ;
166/302 |
International
Class: |
E21B 43/24 20060101
E21B043/24; E21B 36/00 20060101 E21B036/00 |
Claims
1. A method for providing localized heating in a subterranean
formation comprising: placing at a location in the subterranean
formation in any order: an exothermic hydration chemical, and an
effective amount of water in contact with the exothermic hydration
chemical to cause an exothermic reaction; and heating the
location.
2. The method of claim 1 where bitumen is present at the location,
the exothermic reaction does not generate an appreciable amount of
gas, and the heating is sufficient to at least soften the
bitumen.
3. The method of claim 2 where the exothermic hydration chemical is
selected from the group consisting of a relatively neutral
electrolyte, a metal oxide, a metal hydroxide, and an organic
compound, all capable of exothermic reaction without generating an
appreciable amount of gas.
4. The method of claim 3 where the exothermic hydration chemical is
selected from the group consisting of aluminum chloride, NaOH, KOH,
halogen salts, sulfate salts, calcium oxide, barium oxide, and
mixtures thereof.
5. The method of claim 1 where the exothermic hydration chemical is
encapsulated in a material selected from the group consisting of
wax, polymer wax, solid fatty acids, polymers, or is absorbed onto
or bound to a substrate material where the material melts or
disintegrates at the location.
6. The method of claim 1 where the exothermic hydration chemical
has a heat of hydration of at least 40 kJ/mol.
7. The method of claim 1 where gas hydrates are present at the
location, the exothermic reaction may generate an appreciable
amount of gas, and the heating is sufficient to release at least a
portion of hydrocarbons bound in the hydrates.
8. The method of claim 1 where the exothermic reaction chemical is
placed at the location in a delivery medium selected from the group
consisting of alcohols, glycols, heat transfer fluids, organic
oils, and mixtures thereof.
9. A method for providing localized heating in a subterranean
formation comprising: placing at a location in the subterranean
formation where bitumen is present in any order: an exothermic
hydration chemical selected from the group consisting of a
relatively neutral electrolyte, a metal oxide, a metal hydroxide,
and an organic compound, and an effective amount of water in
contact with the exothermic hydration chemical to cause an
exothermic reaction without generating an appreciable amount of
gas; and heating the location sufficiently to at least soften the
bitumen.
10. The method of claim 9 where the exothermic hydration chemical
is selected from the group consisting of aluminum chloride, NaOH,
KOH, halogen salts, sulfate salts, calcium oxide, barium oxide, and
mixtures thereof.
11. The method of claim 9 where the exothermic hydration chemical
is encapsulated in a material selected from the group consisting of
wax, polymer wax, solid fatty acids, polymers, or is absorbed onto
or bound to a substrate material, where the material melts or
disintegrates at the location.
12. The method of claim 9 where the exothermic hydration chemical
has a heat of hydration of at least 40 kJ/mol.
13. The method of claim 9 where the exothermic reaction chemical is
placed at the location in a delivery medium selected from the group
consisting of alcohols, glycols, heat transfer fluids, organic
oils, and mixtures thereof.
14. A method for providing localized heating in a subterranean
formation comprising: placing at a location in the subterranean
formation in any order: an exothermic hydration chemical selected
from the group consisting of a relatively neutral electrolyte, a
metal oxide, a metal hydroxide, and an organic compound, where the
exothermic hydration chemical has a heat of hydration of at least
40 kJ/mol, and an effective amount of water in contact with the
exothermic hydration chemical to cause an exothermic reaction
without generating an appreciable amount of gas; and heating the
location.
15. The method of claim 14 where bitumen is present at the location
and the heating is sufficient to at least soften the bitumen.
16. The method of claim 14 where the exothermic hydration chemical
is selected from the group consisting of aluminum chloride, NaOH,
KOH, halogen salts, sulfate salts, calcium oxide, barium oxide, and
mixtures thereof.
17. The method of claim 14 where the exothermic hydration chemical
is encapsulated in a material selected from the group consisting of
wax, polymer wax, solid fatty acids, polymers, or is absorbed onto
or bound to a substrate material, where the material melts or
disintegrates at the location.
18. A method for providing localized heating in a subterranean
formation comprising: placing at a location in the subterranean
formation containing gas hydrates an exothermic hydration chemical,
and reacting at least a portion of the water in the gas hydrates
with the exothermic hydration chemical to cause an exothermic
reaction to release at least a portion of hydrocarbons bound in the
hydrates.
19. The method of claim 18 where the exothermic hydration chemical
is selected from the group consisting of a relatively neutral
electrolyte, a metal oxide, a metal hydroxide, an organic compound,
a hydrogen halide and perchloric acid.
20. The method of claim 19 where the exothermic hydration chemical
is selected from the group consisting of aluminum chloride, NaOH,
KOH, halogen salts, sulfate salts, calcium oxide, barium oxide,
hydrogen halides, perchloric acid, and mixtures thereof.
21. The method of claim 18 where the exothermic hydration chemical
is encapsulated in a material selected from the group consisting of
wax, polymer wax, solid fatty acids, polymers, or is absorbed onto
or bound to a substrate material where the material melts or
disintegrates at the location.
22. The method of claim 18 where the exothermic hydration chemical
has a heat of hydration of at least 40 kJ/mol.
23. The method of claim 18 where the exothermic reaction chemical
is placed at the location in a delivery medium selected from the
group consisting of alcohols, glycols, heat transfer fluids,
organic oils, and mixtures thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. provisional
application No. 60/614,129 filed Sep. 29, 2004.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and compositions
for providing controlled downhole heating, such as in a
subterranean reservoir during a hydrocarbon recovery operation.
BACKGROUND OF THE INVENTION
[0003] Drilling fluids used in the drilling of subterranean oil and
gas wells along with other drilling fluid applications and drilling
procedures are known. In rotary drilling there are a variety of
functions and characteristics that are expected of drilling fluids,
also known as drilling muds, or simply "muds". The drilling fluid
is expected to carry cuttings up from beneath the bit, transport
them up the annulus, and allow their separation at the surface
while at the same time the rotary bit is cooled and cleaned. A
drilling mud is also intended to reduce friction between the drill
string and the sides of the hole while maintaining the stability of
uncased sections of the borehole. The drilling fluid is formulated
to prevent unwanted influxes of formation fluids from permeable
rocks penetrated and also often to form a thin, low permeability
filter cake which temporarily seals pores, other openings and
formations penetrated by the bit. The drilling fluid may also be
used to collect and interpret information available from drill
cuttings, cores and electrical logs. It will be appreciated that
within the scope of the claimed invention herein, the term
"drilling fluid" also encompasses "drill-in fluids" and "completion
fluids".
[0004] Drilling fluids are typically classified according to their
base fluid. In water-based muds, solid particles are suspended in
water or brine. Oil can be emulsified in the water. Nonetheless,
the water is the continuous phase. Oil-based muds are the opposite
or inverse. Solid particles are suspended in oil, and water or
brine is emulsified in the oil and therefore the oil is the
continuous phase. Oil-based muds that are water-in-oil emulsions
are also called invert emulsions. Brine-based drilling fluids, of
course are a water-based mud in which the aqueous component is
brine.
[0005] It is apparent to those selecting or using a drilling fluid
for oil and/or gas exploration that an essential component of a
selected fluid is that it be properly balanced to achieve the
necessary characteristics for the specific end application. Because
drilling fluids are called upon to perform a number of tasks
simultaneously, this desirable balance is not always easy to
achieve.
[0006] Sometimes during drilling operations subterranean bitumen or
"tar" beds are encountered. These beds are commonly found during
sub-salt drilling in the Gulf of Mexico, but also at other
locations. Indeed, the bitumen occurs so frequently in the Gulf of
Mexico formations that it has been likened to a "river" of tar.
Drilling through thin bitumen beds is generally no more than a
minor nuisance, but thick beds can result in stuck pipe, stuck
casing, side-tracks, loss of hole and other problems that can cost
the well operators millions of dollars. One of the most precarious
operations is running casing after drilling through a bitumen bed
due to the movement or "flow" of the bitumen into the borehole
before casing can be picked up and run to bottom.
[0007] As the price of crude oil has risen, recovery of
hydrocarbons from oil sands, such as those found in Alberta,
Canada, and elsewhere has become more economically attractive. Oil
sands are a mixture of grit and bitumen. The deposits are generally
either minded in massive open pits, or if too deep for surface
mining, are injected with steam to coax the viscous bitumen to flow
into wells.
[0008] Another type of formation encountered during drilling
operations is in situ gas hydrates, also called clathrates. Gas
hydrates are solid inclusion compounds resembling ice. Gas hydrates
occur when water molecules form a cage-like structure around
smaller "guest molecules". The most common guest molecules are
methane, ethane, propane, isobutene, n-butane, nitrogen, carbon
dioxide and hydrogen sulfide, of which methane occurs most
abundantly in naturally-occurring hydrates. In nature, one cubic
meter of hydrate may contain up to about 164 m.sup.3 of methane.
Gas hydrates occur wherever the conditions within the sediments are
in a methane-hydrate stability region and where methane and water
are available. This stability is limited by temperature and
pressure: gas hydrates are stable at low temperatures and/or high
pressure. Because of the requirements of pressure and temperature,
and because of the requirement of relatively large amounts of
organic matter of bacterial methanogenesis, gas hydrates are
primarily restricted to two regions: high latitudes and along the
continental margins in oceans. In polar regions, the gas hydrates
are commonly linked to permafrost occurrence onshore and on the
continental shelves. In the oceans, gas hydrates are found in outer
continental margins, where the supply of organic material is high
enough to generate enough methane, and with water temperatures
close to freezing. These solid crystals, upon melting, can release
up to 170 scf of natural gas per cubic foot of hydrate. The oceanic
gas hydrate reservoir has been estimated to be about 10,000 to
11,000 GtC (Gigatons carbon). The permafrost reservoir has been
estimated at about 400 GtC, but no estimates have been made of
possible Antarctic reservoirs. Given the amount of hydrocarbons
bound in gas hydrates, many are exploring the possibility of
recovering hydrocarbons from this source.
[0009] It would be desirable if compositions and methods could be
devised to provide localized heating to soften the bitumen to help
facilitate movement of the casing or liner through the bitumen to
the bottom. It would also be desirable if compositions and methods
could be devised to provide controlled localized heating to melt
in-situ gas hydrates in order to produce the large quantities of
natural gas they contain. Further, it would be helpful to
facilitate controlled localized heating of oil sands to improve
recovery of hydrocarbons from that source.
SUMMARY OF THE INVENTION
[0010] Accordingly, it is an object of the present invention to
provide a method for heating a location or region downhole in a
subterranean location in a controlled manner.
[0011] It is another object of the present invention to provide a
method and composition for heating a location or region downhole in
a subterranean location containing bitumen or tar in a controlled
manner that does not generate appreciable amounts of gas.
[0012] Further, it is an object of the invention to provide methods
and compositions to assist in the recovery of hydrocarbons from gas
hydrates whether or not appreciable amounts of gas are created.
[0013] In carrying out these and other objects of the invention,
there is provided, in one non-limiting form, a method for providing
localized heating in a subterranean formation that involves placing
at a location in the subterranean formation in any order: an
exothermic hydration chemical and an amount of water in contact
with the exothermic hydration chemical effective to cause an
exothermic reaction thereby heating the location and a suitable
medium for transporting the heat source to the desired
location.
[0014] In another non-limiting embodiment there is created a method
for providing localized heating in a subterranean formation that
involves placing at a location in the subterranean formation where
bitumen is present in any order: an exothermic hydration chemical
and an effective amount of water in contact with the exothermic
hydration chemical to cause an exothermic reaction without
generating an appreciable amount of gas; and heating the location
sufficiently to at least soften the bitumen.
[0015] Alternatively, there is facilitated a method for providing
localized heating in a subterranean formation that involves placing
at a location in the subterranean formation containing gas hydrates
an exothermic hydration chemical, and reacting at least a portion
of the water in the gas hydrates with the exothermic hydration
chemical to cause an exothermic reaction to release at least a
portion of hydrocarbons bound in the hydrates. In this embodiment
an appreciable amount of gas may or may not be released and water
may or may not be added to the formation.
DETAILED DESCRIPTION OF THE INVENTION
[0016] A method has been discovered to generate localized heat
remotely downhole using heat of hydration as a heat source. It has
been estimated in one non-limiting embodiment, if the bitumen in
the "river of tar" beneath the Gulf of Mexico is heated to about
220 to about 230.degree. F. (about 104 to about 110.degree. C.),
the material would be 10 times less viscous. Most exothermic
oxidation/combustion reactions require temperatures that would
compromise mud/spot stability, if not tubular integrity, would tend
to be difficult to initiate and would be problematic to formulate
as a liquid or mud for downhole use. Initiating the reaction at the
surface would tend to expend and dissipate most of the heat before
placement in the target or the mud for downhole use. Hydration of
acidic electrolytes (such as aluminum chloride, AlCl.sub.3) or
acids would be expected to be corrosive and at high temperatures
could compromise the integrity of the tubular goods, tools and
other equipment in many circumstances. For instance, hydration of
aluminum chloride would produce a product environment of about pH
0.8, as contrasted with using NaOH, which would generally yield a
product environment of about pH 14. Oil field chemistries are
generally and preferably alkaline at least in part to avoid or
minimize corrosion concerns.
[0017] The process in one non-limiting embodiment uses a binary
design where in one non-limiting embodiment the "fuel" is placed
first as a slurry or suspension or fluid combined with an
"initiator", e.g. water that produces heat precisely at the point
or location of interest. Although the binary components may be
placed at the location in any order, in most embodiments it is
expected that the "initiator" (e.g. water) would be placed last in
sequence.
[0018] Heat of hydration is defined as the heat evolved (or
absorbed) when a hydrate of a compound is formed. In one
non-limiting embodiment, the exothermic hydration chemical has a
heat of hydration of at least 40 kJ/mol, and alternatively has a
heat of hydration of at least 80 kJ/mol. In general, the exothermic
hydration chemical should be a material that when combined with the
initiator generates sufficient heat to soften, melt or flow the
bitumen, but without generating an appreciable amount of gas. Many
exothermic reactions give large amounts of heat, but produce
relatively large amounts of gas--a thermite reaction, for example.
However, such an exothermic reaction downhole could cause a blowout
of the well and is extremely undesirable. At worst, such a reaction
would be like setting off a bomb downhole. Herein the term "an
appreciable amount of gas" is defined as an amount that would
interfere with normal hydrocarbon recovery operations and does not
include incidental or non-problematic amounts. It should be
understood that avoiding the generation of an appreciable amount of
gas does not mean that water vapor may not be evolved. It is
acceptable in all embodiments herein for water vapor to be evolved
or generated in the process of remote heating a location or
formation.
[0019] With respect to the case where the method herein is used to
deliver heat to a remote location having tar or bitumen, such as
oil sands or subterranean bitumen layers, it may be understood that
these environments are generally non-aqueous, that is, they do not
contain appreciable amounts of water. The water is delivered as
part of the method to be a co-reactant with the exothermic
hydration chemical.
[0020] In the alternative embodiment of the invention where the
exothermic hydration chemical is used to generate heat in a
subterranean gas hydrate formation (e.g. in a permafrost region on
land or sub-ocean), the generation of appreciable amounts of gas is
acceptable--and in fact is desirable since it is expected to be the
primary way in which hydrocarbons (e.g. methane) is released.
Further, this embodiment uses a unitary design; it is contemplated
that in most cases only the exothermic hydration chemical would be
delivered or pumped to the gas hydrate formation or region since
the hydrates themselves would provide the source of most of the
water. Alternatively, additional water may be added as necessary or
desired. As expected, a goal of recovering hydrocarbons from gas
hydrates is to either deliver heat (increase temperature) or reduce
pressure, or both. In many cases it is expected that the
temperature of the gas hydrates need only be raised 2 or 3.degree.
C. for the gas hydrate to decompose and the guest molecules
released.
[0021] There are further a smaller group of exothermic reactions
that would not produce an appreciable amount of gas, but that would
involve reactants--either the "fuel" or "initiator" that would be
too exotic or expensive to use in the quantities necessary for
heating a location in a subterranean reservoir. Thus, although such
systems could be used, it would be desirable if both the "fuel" and
the "initiator" were relatively inexpensive and readily available.
Since water is a highly accessible and cheap material, it is one
non-limiting choice for initiator that may be used. Additionally,
water has a very high specific heat and thus will retain the heat
well for a period of time for the purpose of softening and/or
melting the bitumen or heating in situ gas hydrate formations.
[0022] Factors to be considered in selecting the binary reactants
include, but are not necessarily limited to the expected amount of
heat output (for instance measured in kJ/mol), the cost, the
acidity of the resulting products, the solubility of the "fuel" or
exothermic hydration chemical, HS&E profile (Health, Safety
& Environmental) and the like. In one non-limiting embodiment a
suitable "fuel" or exothermic hydration chemical to react with
water in a hydration reaction includes, but is not necessarily
limited to, a relatively neutral electrolyte, a metal oxide, a
metal hydroxide, and an organic compound. Examples of relatively
neutral electrolytes include, but are not necessarily limited to,
halogen salts such as calcium chloride, magnesium chloride, lithium
chloride, and lithium bromide and mixtures thereof and the like.
Other examples of relatively neutral electrolytes include sulfate
salts such as magnesium sulfate, calcium sulfate, and the like.
"Relatively neutral" refers to an electrolyte that is not strictly
neutral, but which is sufficiently neutral for the purposes of the
process described herein. An example of a non-neutral electrolyte
that could be considered is aluminum chloride, which could be
useful under certain specialized situations. Examples of metal
oxides include, but are not necessarily limited to, calcium oxide,
strontium oxide, barium oxide, and mixtures thereof and the like.
Examples of metal hydroxides include, but are not necessarily
limited to, sodium hydroxide (NaOH), potassium hydroxide (KOH),
lithium hydroxide (LiOH), cesium hydroxide (CsOH) and mixtures
thereof and the like. Examples of suitable organic compounds
include, but are not necessarily limited to, peroxides, epoxides
and monomers whose polymerization would generate heat such as
acrylates, methacrylates and mixtures thereof and the like.
[0023] Other reactants that can be used to generate localized
heating but might be limited in their uses due to appreciable
amounts of gas produced are acid compounds such as hydrogen
bromide, hydrogen chloride, hydrogen iodide, and percholoric acid.
Reactions other than exothermic hydration reactions could be used
to provide localized heating in certain situations. These reactions
are typically not desirable for the bitumen-heating embodiment of
the invention due to the by-products produced.
[0024] Slurry placement of the "fuel" or exothermic hydration
chemical is anticipated where the "fuel" would settle out in the
zone of interest to concentrate the fuel as much as possible in the
desired location. There may be instances where a stable slurry may
be desirable or preferred in a method of delivery and/or placement
at the desired location. By "stable" is meant that the slurry does
not separate or settle upon standing for periods of time. In the
case of the stable slurry, it would be pumped downhole to a
location or against a structure and pack off like a packed bed. The
more densely packed the bed, the more heat generated, and the more
effective the process. The slurry must consist of an organic base
fluid and preferably one that has a low specific heat. The fluid
should also a high thermal conductivity in order to transfer the
generated heat effectively. Examples of fluid mediums include, but
are not necessarily limited to, alcohols, glycols, alcohol/glycol
blends, specifically designed heat transfer fluids, such as
Dowtherm.RTM. fluids (available from Dow Chemical Company) and
Therminol.RTM. fluids (available from Solutia Inc.), esters either
natural such as vegetable oils and/or animal oils or synthetic
esters such as 2-ethylhexyl esters of fatty acids and hydrocarbon
oils either distillates or synthetic.
[0025] Alternatively, placement could involve encapsulating the
fuel or exothermic hydration chemical, such as with a wax; a
polymer wax or other polymer or material that melts or
disintegrates or dissociates at the location. Of course, the
encapsulating material or carrier should not prematurely react with
the exothermic hydration chemical or fuel. Specific examples of
suitable polymeric materials include, but are not necessarily
limited to, hydrocarbon waxes such as paraffin waxes and
microcrystalline waxes, vegetable or animal waxes, solid relatively
weak acids such as tallow or hydrogenated tallow fatty acid,
polybutylene, polymethacrylates, polyethylene glycol (PEG),
methoxylated PEG, polyethylene oxide (PEO), polyethylene waxes,
polypropylene glycol (PPG), and the like. In one non-limiting
embodiment of the invention, suitable encapsulating material
includes ionomeric waxes, including, but not necessarily limited
to, PEG (e.g. CARBOWAX available from Union Carbide Corporation,
Danbury, Conn.), alkoxy terminated PEG (e.g. methoxylated PEG or
mPEG), PEO, and polypropylene oxide (PPO). The encapsulation may be
extended to PEG/PPG, PEG/PEO, and mPEG/PEG blends of different
molecular weights. Polymerization of these polymer shells is well
known in the art. Other extended release forms include, but are not
necessarily limited to, pelletization with binder compounds,
absorbed or some other method of layering on a small particle or
porous substrate, and/or a combination thereof. Specifically, the
fuel or exothermic hydration chemical may be encapsulated to permit
slow or timed release thereof. In non-limiting examples, the
coating material may slowly dissolve or be removed by any
conventional mechanism, or the coating could have very small holes
or perforations therein for the exothermic hydration chemicals
within to diffuse through slowly. For instance, polymer
encapsulation coatings such as used in fertilizer technology
available from Scotts Company, specifically POLY-S.RTM. product
coating technology, or polymer encapsulation coating technology
from Fritz Industries could possibly be adapted to the methods
herein. The sources could also be absorbed onto zeolites, such as
Zeolite A, Zeolite 13X, Zeolite DB-2 (available from PQ
Corporation, Valley Forge, Pa.) or Zeolites Na-SKS5, Na-SKS6,
Na-SKS7, Na-SKS9, Na-SKS10, and Na-SKS13, (available from Hoechst
Aktiengesellschaft, now an affiliate of Aventis S.A.), and other
porous solid substrates such as MICROSPONGE.TM. (available from
Advanced Polymer Systems, Redwood, Calif.) and cationic exchange
materials such as bentonite clay or microscopic particles such as
carbon nanotubes or buckminster fullerenes. Further, the component
sources may be both absorbed into and onto porous substrates and
then encapsulated or coated, as described above.
[0026] Melting would occur at the location temperature, and
disintegration or dissociation may occur due to a change in
temperature, pressure, chemical environment, a combination of these
or other forces. An encapsulated exothermic hydration chemical
could be suspended in an aqueous carrier at the surface and pumped
downhole for placement, such as in the previously mentioned
slurries. The wax or other coating would be chosen to melt at the
temperature of the target zone or just before exposing the fuel
and/or chemical to the water in the carrier at that time. In the
non-limiting case where the encapsulating or shell material is
melted or the disintegration is temperature triggered, as heat is
generated when the exothermic hydration chemical is reacted, more
of the shell or capsules would melt, further accelerating the
process. Alternatively, the capsule shell could be designed to be
dissolved in the initiator (e.g. water). In the context of the
compositions and methods herein, encapsulation includes, but is not
necessarily limited to, microencapsulation.
[0027] In summary, one non-limiting example of the invention would
be drilling out the bitumen inside of a stuck liner, spotting a
caustic soda/"oil" or hydrocarbon slurry inside the liner opposite
or adjacent to the bitumen zone, allowing the caustic soda
beads/powder to settle, and slowly pumping an aqueous fluid to
hydrate the caustic soda to generate localized heating.
[0028] The invention will be further illustrated with respect to
the following Examples which are not intended to limit the
invention, but rather simply to additionally illuminate it.
EXAMPLE 1
[0029] Use of 40 wt % NaOH in oil does not generate heat, but when
contacted with a water-based mud would give 186,000 Btu/bbl.
EXAMPLE 2
[0030] The use of 42 wt % CaCl.sub.2 in oil does not generate heat,
but when contacted with water would give 44,000 Btu/bbl.
EXAMPLE 3
[0031] The use of 70 wt % AlCl.sub.3 when contacted with water,
gives 296,000 Btu/bbl as well.
[0032] In the foregoing specification, the process has been
described with reference to specific embodiments thereof, and has
been suggested as effective in providing components downhole for
controlled release of heat in space and time, such as to soften,
melt or flow bitumen and possibly for other purposes. However, it
will be evident that various modifications and changes can be made
thereto without departing from the broader spirit or scope of the
invention as set forth in the appended claims. Accordingly, the
specification is to be regarded in an illustrative rather than a
restrictive sense. For example, specific combinations of exothermic
hydration chemicals, initiators and proportions as well as various
encapsulation or suspending techniques, thereof falling within the
claimed parameters, but not specifically identified or tried in a
particular composition or example to deliver heat locally and
controllably, are anticipated to be within the scope of this
invention. For instance the compositions and methods described
herein may be used to help recover hydrocarbons from oil sands.
* * * * *