U.S. patent number 3,722,591 [Application Number 05/133,373] was granted by the patent office on 1973-03-27 for method for insulating and lining a borehole in permafrost.
This patent grant is currently assigned to Continental Oil Company. Invention is credited to Orwin G. Maxson.
United States Patent |
3,722,591 |
Maxson |
March 27, 1973 |
METHOD FOR INSULATING AND LINING A BOREHOLE IN PERMAFROST
Abstract
A borehole penetrating a subterranean region is insulated and
lined by hardening in place a hardenable, flowable composition
consisting essentially of a hardenable, flowable, adhesive cement
and a divided, solid, closed-cell material wherein the closed-cell
material can comprise as much as about 80 volume percent of the
hardenable, flowable composition and wherein the hardened material
forming the liner has a hydrostatic crush strength of about
200-5,000 psi, or more. More particularly, syntactic foams are
formed in situ to line boreholes penetrating permafrost.
Inventors: |
Maxson; Orwin G. (Ponca City,
OK) |
Assignee: |
Continental Oil Company (Ponca
City, OK)
|
Family
ID: |
22458299 |
Appl.
No.: |
05/133,373 |
Filed: |
April 12, 1971 |
Current U.S.
Class: |
166/295; 166/901;
166/57 |
Current CPC
Class: |
C09K
8/42 (20130101); E21B 33/10 (20130101); Y10S
166/901 (20130101) |
Current International
Class: |
E21B
33/10 (20060101); C09K 8/42 (20060101); E21b
033/14 () |
Field of
Search: |
;166/DIG.1,292-295,303,302,57 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Novosad; Stephen J.
Claims
I claim:
1. A method for insulating and lining a borehole penetrating a
subterranean region comprising forming a liner in situ by hardening
in place a hardenable, flowable composition consisting essentially
of a hardenable, flowable, adhesive cement and a divided, solid,
closed-cell material, wherein the divided, solid, closed-cell
material comprises as much as about 80 volume percent of the
hardenable, flowable composition, and wherein the hardened material
forming the liner has a hydrostatic crush strength of at least
about 200 psig; wherein the subterranean region is a permafrost
region; wherein the liner is formed in situ by centering a well
casing of smaller diameter with the borehole, injecting the
hardenable, flowable composition consisting essentially of a
hardenable, flowable, adhesive cement and a divided, solid,
closed-cell material into the annulus between the well casing and
the interior surface of the borehole, and allowing the hardening,
flowable composition to harden in the annulus to form the
insulating layer; wherein the hardenable, flowable composition
contains about 10 to 60 volume percent of hollow microspheres whose
diameters are in the range of 1 to 1000 microns having wall
thicknesses of 0.5 to 10 percent of their diameters, and the
remainder comprises a hardenable, flowable, adhesive cement, said
hardenable, flowable, adhesive cement comprising a hydraulic
cement, an epoxy resin, a phenolformaldehyde resin, a polyurethane
resin, or a polysulfide; and wherein the hollow microspheres are
siliceous microspheres.
2. A method for insulating and lining a borehole penetrating a
subterranean region comprising forming a liner in situ by hardening
in place a hardenable, flowable composition consisting essentially
of a hardenable, flowable, adhesive cement and a divided, solid,
closed-cell material, wherein the divided, solid, closed-cell
material comprises as much as about 80 volume percent of the
hardenable, flowable composition, and wherein the hardened material
forming the liner has a hydrostatic crush strength of at least
about 200 psi; wherein the hardenable, flowable composition
contains about 10 to 60 volume percent of hollow siliceous
microspheres whose diameters are in the range of 1 to 1000 microns
having wall thicknesses of 0.5 to 10 percent of their diameters,
and the remainder comprises a hardenable, flowable, adhesive
cement, said hardenable, flowable, adhesive cement comprising a
hydraulic cement, an epoxy resin, a phenolformaldehyde resin, a
polyurethane resin, or a polysulfide.
3. A method for insulating and lining a borehole penetrating a
permafrost region comprising drilling a borehole through the
permafrost region, removing extraneous material from the borehole,
flowing a hardenable, flowable composition consisting essentially
of a hardenable, flowable, adhesive cement and a divided, solid,
close-cell material into the borehole filling said borehole,
hardening the hardenable, flowable composition in the borehole, and
drilling a smaller diameter borehole through the hardened material
to complete the formation of the insulating liner in the original
borehole; wherein the divided, solid, closed-cell material
comprises as much as about 80 volume percent of the hardenable,
flowable composition; and wherein the hardened material forming the
liner has a hydrostatic crush strength of at least about 200
psi.
4. A method for insulating and lining a borehole penetrating a
permafrost region comprising forming a liner in situ by hardening
in place to form hardened matter a hardenable, flowable composition
consisting essentially of a hardenable, flowable, adhesive cement
consisting essentially of an epoxy resin plus a hardening agent
plus a divided, solid, closed-cell material; wherein the divided,
solid, closed-cell material comprises as much as about 80 volume
percent of a hardenable, flowable composition; wherein about 10 to
60 volume percent of the hardenable, flowable composition is
hollow, siliceous, microspheres having diameters in the range of 1
to 1000 microns and wall thicknesses of 1 to 5 percent of their
diameters; and wherein the hardened matter of the liner has a
hydrostatic crush strength of about 200 to 15,000 psig.
Description
BACKGROUND OF THE INVENTION
The invention relates to a method for lining boreholes penetrating
subterranean formations.
A considerable need exists for an improved method of lining
boreholes penetrating subterranean formations. Thus, substantial
benefits can be derived from a conservation of heat energy in steam
injection wells for tertiary oil recovery, hot water injection and
production wells for the Frasch sulfur recovery process, and wells
for the recovery of geothermal steam can be insulated
satisfactorily with insulating liners.
A particularly acute need for an improved method for lining
boreholes with an insulating liner occurs in the exploration for
and production of oil in Arctic regions. Major oil discoveries on
the northern slope of Alaska and other Arctic areas occur in
regions where permafrost may occur from the surface to depths of
2,500 feet or more. The permafrost is largely made up of sand,
gravel, soil, and other materials frozen in a matrix of solid ice.
When a wellbore penetrates such a permafrost region circulation of
relatively warm drilling mud in the drilling operation melts the
permafrost in the area of the wellbore. When a well is put on
production, movement of the relatively hot oil through the
permafrost region melts the permafrost in the vicinity of the
wellbore. Severe problems of enlargement of the wellbore with
subsidence of material from the permafrost region have been
encountered. This necessitates the use of extremely high strength
casing materials and massive cementing jobs around the wellbore to
maintain the integrity of the wellbore.
One method to mitigate the problem of melting of permafrost in the
region of a wellbore is to insulate the wellbore from the
surrounding permafrost region. Various expedients have been tried.
For example, casing which is sheathed with polyurethane foam has
been tried. However, beyond shallow depths this is entirely
unsatisfactory because hydrostatic pressure at lower levels of the
permafrost region crushes the cell structure of the polyurethane
foam and largely destroys its insulative properties. Attempts to
form foamed materials in the region of the wellbore employing
foaming agents as taught by Chism, U. S. Pat. No. 3,379,253, and by
others are unsuccessful because the high hydrostatic pressure at
the lower levels of the permafrost region prevents expansion of the
gaseous foaming agents or contracts the foams formed before
injection. Likewise, inclusion of foamed materials such as expanded
perlite in conventional cements is not satisfactory because the
high hydrostatic pressure crushes such materials and significantly
destroys the insulating properties of such cements. Therefore,
while such prior art methods have some utility for insulating
boreholes in the permafrost regions near the surface, they are not
at all satisfactory at greater depths where considerable
hydrostatic pressure is encountered. Thus, a clear cut need exists
for an improved method of insulating boreholes penetrating through
permafrost regions, particularly at the lower levels of such
formations where considerable hydrostatic pressure is encountered
and more particularly near the bottom of the permafrost region
which is always near its melting point.
OBJECTS OF THE INVENTION
An object of the instant invention is to provide a method for
insulating and lining a borehole penetrating a subterranean region
whereby a liner is formed in situ by hardening in place a
hardenable, flowable composition consisting essentially of a
hardenable, flowable, adhesive cement and a divided, solid,
closed-cell material.
These and other objects and advantages will appear from the
following description of the embodiments of the invention, and the
most novel features will be particularly pointed out hereinafter in
connection with the appended claims.
SUMMARY OF THE INVENTION
In one aspect, this invention discloses a method for insulating and
lining a borehole penetrating a subterranean region wherein a liner
is formed in situ by hardening in place a hardenable, flowable
composition consisting essentially of a hardenable, flowable,
adhesive cement and a divided, solid, closed-cell material.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A liner for a borehole penetrating a subterranean region is formed
in situ by hardening in place a hardenable, flowable composition
consisting essentially of a hardenable, flowable, adhesive cement
and a divided, solid, closed-cell material, the closed-cell
material comprising as much as about 80 volume percent of the
hardenable, flowable composition and the hardened material forming
the liner having a hydrostatic crush strength of at least about 200
psi, and more particularly of about 200- 15,000 psi, or more.
According to one presently preferred embodiment, a wellbore is
drilled through the subterranean region to be lined, such as a
permafrost region. This wellbore should be somewhat larger than the
wellbore desired for the final well. Residual materials are removed
from the wellbore or are displaced by a composition consisting
essentially of a hardenable, flowable, adhesive cement and a
divided, solid, closed-cell material. The composition is admixed
and flowed into the wellbore to entirely fill the wellbore
throughout the region to be lined. The material is then allowed to
harden. A wellbore of smaller diameter is then drilled through the
center of the hardened material leaving a liner formed in situ
lining the original borehole.
Alternatively, according to another presently preferred embodiment,
a wellbore is drilled through a subterranean region to be lined,
such as a permafrost region. A second liner such as a steel pipe is
hung so that it extends substantially through the region to be
lined. The hardenable, flowable composition of the instant
invention consisting essentially of a hardenable, flowable,
adhesive cement and a divided, solid, closed-cell material is then
injected between the second liner and the inner surface of the
borehole. Upon hardening, an insulating lining is formed in situ
which bonds the steel liner to the formation.
In general, the insulating liner of this invention can be formed in
situ by injecting into place a hardenable, flowable composition
consisting essentially of a hardenable, flowable, adhesive cement,
and a divided, solid closed-cell material by any method known to
the art for injecting a conventional fluid hydraulic cement into
place. Such techniques are disclosed in U. S. Pat. No. 3,379,253
and in various literature distributed by oil well cementing
companies. Such techniques are well known to the art.
The hardenable, flowable, adhesive cement of this invention can
include any substantially fluid material which can be injected into
the borehole with conventional oil well cementing equipment and
which will harden upon standing to a solid material having
sufficient cohesive strength and adhesive strength to the divided,
solid, closed-cell material to form a material having sufficient
mechanical strength to substitute for conventional wellbore lining
cements. Examples of suitable hardenable, flowable, adhesive
cements include: hydraulic cements, epoxy resin, phenolformaldehyde
resin, polyurethane, and polysulfide resin. When a liner is formed
in a permafrost region, a hardenable, flowable, adhesive cement
should be employed which is flowable but yet hardenable at the
temperatures encountered.
The hydraulic cement is admixed with a conventional amount of
water, and includes any of the conventional hydraulic cements
employed in oil well cementing. In addition, suitable additives can
be incorporated including retarders, accelerators, low water loss
additives, lost circulation additives, friction reducers, and the
like.
When the terms epoxy resin, phenolformaldehyde resin, polyurethane,
or polysulfide are employed in the instant application to describe
examples of a hardenable, flowable, adhesive cement, it is to be
understood that these terms are used in conformity with a wide
general useage among those skilled in the art. Actually, these
terms, as they are employed here, refer to the precursor mixtures
for the various resins which harden to form the actual solid
adhesive cement by chemical reaction. These materials and their
mode of action are well known to those skilled in the art.
Considerable information on such adhesive cement systems can be
found in Skeist, Handbook of Adhesives, Reinhold Publishing Corp.,
(1962). In essence, any of such hardenable, flowable, adhesive
cements which meet the criteria defined above can be employed
according to this invention.
The divided, solid, closed-cell materials of the instant invention
include those materials which have a particular size diameter in
the range of 1 micron to 10 cm, which have over 20 volume percent
void space, which have the void space present as closed-cells, and
which have a hydrostatic crush strength of at least about 200 psi,
and preferably of about 200 to 15,000 psi, or more.
Presently preferred are hollow microspheres having diameters in the
range of about 1 to 1,000 microns which have wall thicknesses of
0.5 to 10 percent of their diameters. The walls of such
microspheres can be comprised of an organic polymer such as
polyurethane or a ceramic material such as glass. Specific examples
of suitable materials include certain fly ash floater products.
Even more presently particularly preferred are hollow siliceous
microspheres having diameters in the range of 10 to 100 microns and
wall thicknesses of 1 to 5 percent of their diameters.
The hardenable, flowable compositions of this invention can be
prepared by admixing the hardenable, flowable, adhesive cements and
the divided, solid, closed-cell materials of this invention by any
means conventionally known for the admixing of particulate solids
and liquids.
The divided, solid, closed-cell material comprise as much as 80
volume percent of the hardenable, flowable composition, and often
comprises 10 to 80 volume percent of the hardenable, flowable
composition.
The materials sued to prepare the hardenable, flowable compositions
of this invention are readily available from commercial
sources.
EXAMPLES
Example 1
A 22 inch diameter wellbore is drilled through a permafrost region
which is 2,480 feet thick and into the strata below for a distance
of an additional 50 feet. The wellbore is then cleaned of
extraneous material. A hardenable, flowable composition containing
80 volume percent of a product which is comprised of hollow
siliceous spheres having a diameter range of 1 to 1,000 microns and
a wall thickness of 0.5 to 10 microns, 15 volume percent Portland
cement, 5 volume percent of water and air is admixed on the surface
and injected into the borehole penetrating the permafrost region
and portion of the stratum below. The material is allowed to harden
for 24 hours. Upon substantial hardening of the hardenable
material, a wellbore having a diameter of 18 inches is drilled
through the center of the hardened material filling the original
borehole. An insulative liner is thus formed in situ which has good
mechanical strength and excellent insulating properties due to the
voids in the closed-cell material which remain open even under the
high hydrostatic pressure found at the bottom of the borehole.
Example 2
A wellbore having a diameter of 22 inches is drilled through a
permafrost region having a depth of 2,400 feet to a total hole
depth of 2,500 feet. A steel casing having an outside diameter of
18 inches is hung so that it extends nearly to the bottom of the
borehole. A hardenable, flowable composition containing 38 volume
percent of epoxy resin precursors and 62 percent by volume of
hollow siliceous microspheres is admixed on the surface and
injected into the annulus between the steel pipe and the outside of
the borehole. The epoxy resin precursors include 95 volume percent
of EPON 8- 28 (a trademark) epoxy resin (which is a reaction
product between bis-phenol A and epichlorohydrin), and 5 percent of
DETA (diethylene triamine). This hardenable, flowable composition
is allowed to harden for 24 hours. The syntactic foam which is thus
formed in the annulus between the steel casing and the borehole is
a liner which has excellent mechanical strength and excellent
insulating properties due to the high closed-cell void content of
the resulting syntactic foam. The high hydrostatic crush strength
of the microsphere material and the resulting syntactic foam
insures that excellent thermal properties are present in the
insulating liner thus formed, even at lower depths.
Example 3
The run of Example 2 is repeated, except that 1, 3, 6-hexane
trithiol is substituted for about 80 mole percent of the diethylene
triamine. Cure is affected more rapidly at the relatively low
downhole temperature to produce a liner of improved strength.
* * * * *