Note: Descriptions are shown in the official language in which they were submitted.
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WIRELINE GREASE HEAD
Field of the Invention
This invention relates to grease control heads for sealing around flexible
wireline, slick-
line (solid wire) or braided wire (collectively service line) while
perforrning service operations in
a well and more particularly to the use of nonmetallic materials, such as
ceramic inserts, in the
grease head..
Backaound of the Invention
Service lines are passed through a grease head as part of wireline pressure
control
operations. A grease head from the top down may include a line wiper, a grease
and liquid
overflow housing, one or more grease couplings and one or more flow tubes.
Each flow tube
consists of an outer rigid tube or body, an internal housing for inserts with
the housing being a
rigid-cylindrical tube and one or more inserts inside the housing.
When worlcing in a well under pressure, viscous grease is injected into the
flow tube
through one or more grease couplings at a pressure greater than the existing
well pressure.
Grease fills the annular space between the inner wall of inserts and the
outside surface of the
service line forming a liquid seal that contains the well fluids while
allowing service line
movement. The combination of the inserts, service line and grease provide a
pressure barrier to
contain the well gas and liquids. The grease barrier is increased by
increasing the number of
flow tubes and grease couplings. A problem with the present grease heads is
the wear that
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occurs on the inside surface of the metal inserts, which makes it difficult
and eventually
impossible to maintain the proper pressure barrier to contain the gases and
liquids of the well.
The servicing of grease heads, which includes the replacement of the metal
inserts, is
expensive and time consuming. Additionally, worn inserts abrade braided
service lines, which
may cause a break in the outer surface and an unraveling of the braid. This
hampers or stops the
movement of the service line through the grease head and/or other components
above and below
the grease head.
Grease heads have been made with steel inserts for over 20 years. It has been
found that
the service line with a metallic surface inside the steel inserts resWts in
particles of steel being
pulled from both. As a result, the metal inserts get out of tolerance and
grease is pulled down
hole with the service line which increases the amount of grease needed for
each operation.
Additionally, when the wear becomes great enough, the grease head cannot
maintain the
necessary pressure and fluids from the well, in addition to grease, may escape
from the overflow
housing at the top of the grease head. As a consecluence, the cost of
operation increases because
of the increase in grease used. Further, the grease that escapes from the
grease head and
overflow housing gets on trucks, trailers and other devices at the well site
which may be an EPA
problem.
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Summarv of the Invention
This invention involves an improved grease head having a longer life with
extended
periods between servicing and consists of flow tubes having ceramic inserts.
The ceramic inserts
have a longer life than the typical steel inserts which results in significant
reductions in the costs
of operation.
Ceramic inserts and inserts of other non-metallic material do not have the
loss of material
experienced with metallic inserts. Consequently, there is better control over
the well bore
lo pressure. Additionally, not as much grease is required for lower a cost of
operation. The EPA
concern is significantly reduced and the well site location is kept cleaner.
Further, the grease
head with ceramic inserts perform as required for over 200 runs of service
line through the
grease head compared to the typical 20-30 runs with metallic inserts before
servicing is needed.
Moreover, with ceramic inserts, the service line may be retracted from the
well at a much higher
speed, such as between 350 feet to 400 feet per minute, as compared to 100
feet to 150 feet per
minute with steel inserts.
Objects, features and advantages of this invention will become apparent from a
consideration of the foregoing and the following description, the appended
claims and the
accompanying drawings.
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Brief Descrintion of the Drawings
Fig. 1 is an elevation view of a grease head in place for performing service
operations in
a well, according to the present invention;
Fig. 2 is an elevation view of components of the grease head, partially in
cross-section,
according to the present invention;
Fig. 3 is a cross-sectional view of the grease head taken along the section
lines 3-3 of Fig.
2, according to the present invention;
Fig. 4 is an elevation view of a housing of a flow tube, partially broken
away, according
to the present invention; and
Fig. 5 is a perspective view of a ceramic insert, according to the present
invention.
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Detailed Descrintion of Preferred Embodiment
Wells that produce gas are drilled to various depths, including common depths
of 8,000
feet to 9,000 feet and sometimes to depths of 12,000 feet or greater. A solid
casing is inserted in
the drilled hole to the depth of the hole. Thereafter, many tests are
conducted down hole and
holes are created in the casing. The instruments for the tests and the tools,
including explosives,
for creating the holes are inserted in the weli and removed from the well by a
service line that
carries the instrument or tool at its end. The service line may be a solid
wire sirnilar to piano
wire, a braided wire with internal electrical conductors or braided wire
without electrical
conductors. In each case, the outer surface of the service line is metallic
for strength and
durability.
As shown in Fig. 1, a service line I passes through a grease head 2 that
lubricates the
line. Grease fills the annular space between the outer surface of the service
line and an inner
surface of the grease head to create a pressure barrier to contain the fluids
in the well. The
grease head 2 includes at least one flow tube 4 and at least one grease
coupling 6. The number
of flow tubes 4 and grease couplings 6 depends on the desired operating
pressure of the grease
head, which must be greater than the pressure of the well. The grease head 2
is attached to and
extends vertically above a well head 7. The well head 7 extends from a casing
8 which is placed
in the hole drilled in the earth. A tool section 10, which has a length to
accommodate the
instruments and tools (representatively shown by rectangle 11), is located
between the grease
head 2 and the well head 7. An overflow housing 12 is at the top of the grease
head 2 with a line
wiper 14 being above the overflow housing.
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Grease is inserted into the grease head 2 through one or more fittings 15
which are
screwed into a threaded hole (Fig. 2) in the side of a grease coupling 6.
Grease is typically
inserted into only one of the grease couplings 6, when there are a plurality
of couplings. Details
of the grease head 2 are shown in Figs. 2-4. The upper grease coupling 6 of
Fig. 2 has the grease
fitting 15 inserted into a threaded hole 16 in the side of the coupling 6.
The flow tube 4 includes a cylindrical outer body 19 that is threaded at both
ends with
threads 20 and is attached to the grease couplings 6 at each end by threads 21
in the ends of the
grease couplings 6. The outer body is a rigid metal cylinder with external
threads 20 at each end.
Inside the outer body 19 is a rigid cylindrical housing 24. Housing 24 has
tapers 25 at each end
for easy insertion into a recess 27 that has been formed in each end of the
grease couplings 6.
When the outer body 19 of the flow tube 4 is screwed onto a grease coupling 6
at each end with
the housing 24 in place, the housing is held in place.
Ceramic inserts 30 are shown in elevation view in Fig. 2 and in a perspective
view in Fig.
5. In one particular grease head the housing 24 has a length of 13 1/2 inches.
This length may be
greater or less than 13 1/~ inches. Although there may be a single ceramic
insert 30 in the housing
24, better results are obtained by employing a plurality of ceramic inserts
30. In one typical
grease head, the ceramic inserts 30 have a length of 1.005 inches with an
outside diameter 31 of
0.450 inches and an inside diameter 32 of 0.291 inches. The inner diameter 32
is based upon the
outer diameter of the service line that passes through the ceramic insert 30.
The annular spacing
between the outside surface of the service line and the inner surface of the
insert 30 is preferably
between .003 inches and .008 inches to provide the desired grease barrier. The
outer diameter of
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a service line varies in use compared to the outer diameter of a service line
newly installed on a
reel or drum. The annular spacing is designed to be 0.005 inches between the
I.D. of the ceramic
insert and the O.D. of the service line in use
The annular spacing between the ceramic insert 30 and the inner diameter of
the housing
24 is between .005inches and .010 inches so that the insert will easily slip
into the housing 24.
The outer diameter 31 of the ceramic inserts 30 may be a standard size for a
number of different
sizes of service lines, with the inner diameter being determined by the outer
diameter of the
service line.
In the assembly of the flow tube 4, a threaded nut 34 is placed into one end
of the
housing 24 and then the ceramic inserts 30 are slipped into the housing 24.
With a 13 1/2 inch
long housing 24, 13 ceramic inserts, having a length of 1.005inches, are
placed in the housing.
After insertion of the ceramic inserts, a second threaded cap 34, shown in
Fig. 4, is threaded into
the housing 24 to secure the inserts in place. The threaded nut 34 may have
grooves in the top
surface to accommodate a tool or may be a solid nut that has a hex-shaped
opening for the tool to
insert and tighten the nut in place. Once the nut 34 is in place, the center
of the nut 34 is drilled
out to permit the service line 1 to pass through the nut and through the
ceramic inserts 30.
Although the description above contains specificity, this should not be
construed as
lirnitin.g the scope of the invention but merely as providing illustrations of
one of the preferred
embodiments of the invention. This invention is not limited to the specific
embodiments, but
rather the scope of the invention is to be determined as claimed.
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