GEOTHERMAL WELLHEAD ASSEMBLY

TETE DE FORAGE GEOTHERMIQUE

English Abstract

TITLE OF THE INVENTION : IMPROVED GEOTHERMAL WELL HEAD
ASSEMBLY
INVENTOR : LEHMAN T. REED
DOCKET NO. B-2741




ABSTRACT OF THE DISCLOSURE
A geothermal well head assembly that is removably
mounted on the upper flanged end of a surface string of
casing that is submitted in the upper portion of a bore hole
that extends to the heated zone. A second string of casing
is concentrically disposed in the first casing and extends
to the heated zone, which second string of casing tends to
expand and contract longitudinally to the first string. A
rigid ring is disposed in the annulus space between the first
and second strings of casing adjacent the ground surface and
first and second resilient seals in pressure contact with the
interior surface of the first casing and exterior surface of
the second casing. Means are provided for periodically and
independently adjusting the compression on these seals from
the exterior of the assembly without shutting down the
geothermal well, which shut down is undesirable as possibly
having an adverse effect on future production from the well.



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Claims

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined
as follows:-




1. A geothermal well head assembly of the type that
that includes a first flange on upper extremity of a
first casing that is cemented in and extends down a well
bore that is in communication with a heated fluid producing zone,
said first flange having a cylindrical interior surface, a
spool that includes second and third flange; a valved
manifold that controls the flow of heated fluid from said zone
which manifold has a fourth flange on the lower end thereof;
a plurality of bolts that removably secure said second flange
to said first flange, and said fourth flange to said third
flange; a second casing that has an external diameter substan-
tially smaller than the interior diameter of said first
casing and concentrically disposed therein, said first and
second casing defining an annulus shaped space therebetween,
said second casing having an upper end adjacently disposed
to said second flange and a lower end that occupies a fixed
position relative to said heated fluid producing zone, said
first casing having a longitudinally extending recess in
the interior thereof below said cylindrical interior surface,
said recess terminating at the bottom in a first circular
body shoulder said second flange having a plurality of
circumferentially spaced first and second internally
threaded bores therein, the improvement for adjustably
effecting a seal between said first and second casing
without shutting said well down that allows the latter to
expand and contract longitudinally due to variations in the
temperature thereof, said improvement comprising:

a. a plurality of first and second resilient
sealing rings;



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Claim 1 continued ...




b. a first rigid ring disposed in said annulus
space and resting on said first body shoulder, said first
ring having a top from which first and second circular
slots extend downwardly, said first slot adjacent said
recess, and said second slot adjacent the exterior surface
of said second casing, with at least one of said first
sealing rings disposed in said first slot and at least one
of said second sealing rings in said second slot;
c. a second rigid ring slidably movable in said
annulus space above said first ring, said second ring
including a downwardly projecting portion that contacts
the upper surface of said first sealing ring;
d. a third rigid ring slidably movable in said
annulus space and with at least the major portion thereof
disposed above said second sealing ring;
e. a plurality of first and second elongate
rigid force exerting members that have upper wrench
engageable ends and lower flat force exerting ends, said
first and second members having first and second threads
thereon intermediate said upper and lower ends, said first
threads engaging said first internally threaded bores and
said first elongate members extending downwardly through
recesses in said third ring for said lower end of said first
elongate members to contact said second ring and said
second threads engaging said second internally threaded
bores to dispose said lower ends of said second elongate
members in pressure contact with said third ring , with said
first elongate members when rotated in a first direction



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Claim 1 continued ...




moving downwardly relative to said second flange to move
said second ring downwardly to compress said first resilient
ring and radially deform the same into sealing contact
with said recess and first rigid ring at a desired pressure,
and said second elongate members when rotated in a first
direction moving downwardly relative to said second flange
to move said third ring downwardly to compress said second
resilient ring and radially deform the same into sealing
contact with said first rigid ring and the exterior surface
of said second casing at a desired pressure, and the desired
sealing pressures effected by said first and second sealing
rings capable of being periodically varied by use of said
first and second elongate members without shutting in said
geothermal well.



2. A geothermal well head assembly as defined in
Claim 1 in which said second rigid ring is of inverted L-
shaped transverse cross-section and includes a first horizontal
circular leg and a second vertical circular leg that bears
against the upper surface of said first resilient sealing
ring.



3. A geothermal well head assembly as defined in
Claim 1 in which said third rigid ring is of inverted L-shaped
transverse cross-section and includes a first horizontal
circular leg that has a plurality of circumferentially
spaced recesses therein through which said first elongate
members extend downwardly, and a second circular leg that
bears against the upper surface of said second resilient
sealing ring.



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Description

This invention relates to an improved geothermal
well head assembly.
In recent years, due to the uncertainty of petro-
leum and natural gas as a source of energy, the production
of power from geothermal wells has taken on increased
importance. A troublesome problem in the production of
` geo-thermal energy, is maintaining a seal at the well head
between the ambient atmosphere and the interior of the valve
manifold through which the heated fluid Erom the geothermal
zone flows.
The difficulty in so maintaining the seal is due
to the substantial longitudinal expansion and contraction
that takes place in the casing or tubing string through
which heated fluid flows relative to the stationary well
head assembly. In the past it has been common practice to
employ multiple groups of resilient rings to effect the seal
to allow for such expansion and contraction, with the groups
of rings having the same force exerted thereon to radially
expand the same. Such a mode of sealing has been found
unsatisfactory in that there is no correlation between the
forces exerted on the two groups of resilient rings, and as
a result an excessive force may be exerted on one group and
an insufficient force on the other group.
The present invention seeks to furnish a geother-

mal well head assembly that allows longitudinal expansionand contraction of the string of casing that extend to the
producing zone relative to the surface string of casing by
the use of compressed first and second resilient seals, and
the seals having first and second manually operated means
operatively associated therewith that may be periodically
used to independently adjust the compression


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on the seals wi~hout shutting down the well.
The shutting down of a geothermal well by pumping
heavy mud downwardly in the bore hole thereof is highly
undesirable as the future productivity of the ~11 may be
impaired, and in some instances ruined,


The geothermal well head assembly of which the
present invention forms a part includes the first flange
which is located on the upper extremity of a first casing
that is cemented in and extends down,a well bore to communicate
with a heated fluid producing zone. The assembly also includes
a spool that has second and third flange~ on the ends thereof.
A valved manifold is provided that has the fourth flange on
the lower end thereof. A number of bolts removably secure
the second flange to the first flange and the fourth flange
to the third flange. A second casing is provided that has
an upper end that is so disposed that the upper end extends
above the first flange. The second casing has an external
diameter that is substantially smaller than the internal
diameter of the first casing in which it is disposed, and
the two casings defining an annulus space therebetween. The
second casing has a lcwer end thereof in communication with
the heated fluid producing zone.
The geothermal well head assembly of the present
invention allows the second casing to expand and contract
longitudinally due to variations in the temperature thereof,
and this expansion and contraction t~king place while a
primary and secondary seal is maintained, with these
seals preventing undesired communication between the


ambient atmosphere and the interior of the well head assembly.
The well head assembly is characterized by the
first flange having an interior cylindrical surface of the
same diameter as a cylindrical recess in the upper portion
of the first string of casing that is situated directly
therebelow, which recess terminates at the bottom thereof
in a first circular body shoulder. The second flange has a
number of equally spaced internally threaded first bores and
also a number of equally spaced second threaded bores therein.
A first rigid ring is disposed in the annulus space
and rests on the body shoulder. The first ring has a first
and a second circular slot that extends downwardly therein,
and in which first and second groups of resilient sealing
rings are disposed. The first group of sealing rings when
compressed expands radially into pressure sealing contact
with the surface of the recess in the first casing. The
~econd group of sealing rings when compressed deform radially
to pressure contact the exterior surface of the second casing
and maintain a seal therewith as the second casing expands
and contracts longitudinally due to variations in the temperature
thereof.
: A second ring of transverse inverted L-shaped
cross-section is slidably mounted in the annulus space and
has the lower portion in contact with the uppermost one of
the first sealing rings. A third ring of transverse
inverted L~shaped cross-section is disposed in the annulus
space and has the lower portion in contact with the uppermost
one of the second sealing ring.
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First and second externally thr~aded force
.. exerting members are in engagement with the first and
- second ~apped bores in the second flange, and with the
lower ends of the first and second members in contact
with the upper surfaces of the second and third rings.
By rotating the first and second force exerting
members the second and third rings may be moved downwardly
independently of one another to compress ~he first and
second resilient rings and expand the same radially to
effect seals with the interior surface of the first casing
and exterior surface of the second casing. The first and
second seals may accordingly be periodically adjusted as
to the compressive force thereon without shutting down the
geothermal well, and thus eliminating the possibility
that the future productivity of the well will be impaired
or ruined as may occur when prior art geothermal well head
assemblies are used.



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The invention is illustrated merely by example
in the drawings, in which:
Figure l is a side elevational view of a geo-


thermal well head assembly that includes the present inven-
tion;

Figure 2 is a combined top plan view and trans-
verse cross sectional view of the assembly taken on the
line 2-2 of Figure l;
Figure 3 is a longitudinal cross-sectional view
of a portion of the assembly taken on the line 3-3 of Figure

2; and
Figure 4 is a combined top plan view and transverse
cross-sectional view of the assembly taken on the line 4-4

of Figure 3.
In Figure 1 a well head assembly A is s-hown that

includes the present invention. The assembly A includes a
` first flange lO that is mounted on the upper end of a first
string of casing 12 that extends downwardly in a geothermal

well bore 14 and is enveloped in cement 16 within the bore
hole. The bore hole extends to a geothermal zone B from

which heated fluid is produced. A second flange 18 is
secured to the lower end of a spool C, with the upper end of
the spool having a third flange 20 affixed thereto. A valve


; manifold D is provided as may best be seen




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: in FIG. l that has a fourth flange 2~ on the lower end
thereof, with the flanges 22 and 20 being held together
by bolts 24, and the first and second flanges 10 and 18
likewise being secured to one another by bolts 24. A
second casing 26 is concentxically disposed within the
first casing, with the second casing extending downwardly
to the geothermal zone B and having the lower end at a
fixed position relative to this zone. As the second
casing 26 is alternately heated and cooled by variations
in the flow of geothermal fluid therethrough, this second
casing expands and contracts longitudinally relative to
the first casing 12. The first flange 10 has a cylindrical
interior surface that is the same diameter as a recess
28 that extends-downwardly a short dis~ance in the upper
portion of the first casing, with the recess terminating
- at the lower end thereof in a first body shoulder 30.
The interior s~rface of the first casing 12 and the exterior
surface of the second casing 26 are separated by an annulu~
space 29. A first rigid ring E is provided that is
mounted in the annulus space 29, and the first ring resting
on the body shoulder 30 as may best be seen in FIG. 3.
The first ring E has a top 32, bottom 34, and
first and second circular slots 36 and 38 that extend
downwardly from the top thereof, as may best be seen in
FIG. 3, with the first and second slots having second and
third body shoulders 40 and 42 at the bottom thereof.
: A number of first resilient packing rings 44
. are ~tacked one above the other in the first slot 36
as shown in FIG. 3, and a number of second resilient sealing

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rings 46 are disposed within the second slot 38 and
situated one above the other. A first ring-shaped
force transmitting member 48 is disposed in the annulus-
- space 29, and is of inverted L-shaped transverse cross-
section, and includes a horizontal leg 48a, vertical
leg 48b, with the leg 48b terminating in a flat lower
surface 48c that rests on the uppermost one of the first
sealing rings 44.
A second force transmitting member 50 is
provided and situated in the annulus shaped space 29,
with the second member being of transverse inverted
L-shaped cross-section. The second force transmitting
member 50 includes a horizontal leg 50a, a vertical leg
50b, and the vertical leg terminating in a flat lower
surface 50c that rests on the uppermost one of the second
resilient rings 46 as mayi)be seen in FIG. 3. The second
flange 18 has a number of equally spaced first threaded
bores 52 extending downwardly therein that are axially
aligned with first counterbores 54 that are also
internally threaded and extend upwardly in the flange, with
the bores and counterbores at the junction defining
second circular body shoulders 56. The second flange 18
also has a number of second bores 58 extending downwardly
therein that are axially aligned with second upwardly
ext~nding counterbores, with the second bores and counter-
bores at their junction defining second circular body shoulders
62. A number of first externally threaded cylindrical bushings
64 are disposed in the first bores 52 and second bushings 66



in the second bores 58 as may best be seen in FIG. 3.
A number of force elongate force exerting members 68
are provided that have wrench engageable upper end portions
68a, flat lower ends 68b, and threads 68c formed thereon
intermediate the upper and lower ends. The threads 68c
engage the first counterbores 54. Also, a number of elongate
second force exerting members 70 are provided that have wrench
engageable upper ends 70a, flat lower ends 70b, and threads
70c formed on the members intermediate the upper and lower
ends, with the second counterbores 60. The first force
exerting member 68 as may be seen in FIGS. 3 and 4 extend
downwardly through recesses 72 defined in the longitudinal
leg 50a of the second force transmitting member 50. The
- first and second flanges 10 and 18 have opposed recesses
74 defined therein in which a sealing ring 76 is dispo~ed
as shown in FIG. 3. The upper end of the second casing 26
extends above the upper surface of the first flange 10 as
will be evident in FIG. 3.
The use and operation of the well assembly A as
shown in FIG. 3 is extremely simple. When the well head
assembly A is in an operative condition, as shown in FIG. 3,
the second casing 26 has the upper end thereof disposed
; above the first flange 10. The first and second sealing
rings 44 and 46 as may be seen in FIG. 3 effect a seal
between the interior surface of the first casing 12 and
~ the rigid ring E, as well as between the ring E and the
; exterior surface of the second casing 26. When it is
desired to increase the compression on the first sealing



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rings 44, this is accomplished by compressing the rings
downwardly to radially expand the same into pressure
contact with the interior of the first casing 12 and the
portion of the rigid ring E adjacent the first slot 36.
This compression is achieved by rotating the first force
exerting members 68 in a direction that they move downwardly
relative to the second flange 18 and in so doing move the
first force exerting ring 48 downwardly for the lower ends
thereof to pressure contact the uppermost one of the first
resilient ring 44.
When it is desired to adjust the compression on
the second resilient rings 46 to radially expand the same
into greater slidable pressure sealing contact with the
second casing 26, and independent of the compressive force
on the first sealing rings 44, the second force exerting
members 70 are rotated in a direction to cause them to move
downwardly relative to the second flange 18. As the force
exerting members 70 move downwardly, the second force
exerting ring is likewise moved downwardly to further
compress the second sealing ring 46. From the above
description it will be seen that the first and second
sealing rings 44 and 46 may have the compression thereon
periodically adjusted without shutting down the geothermal
well, with potentially unfavorable results.
The use and operation of the invention has been
described previously in detail and need not be repeated.




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