High-load big bore lock

Details High-load big bore lock High-load big bore lock

2000-08-30

2003-02-11

Bagnell, David (Department: 3672)

Wells

Processes

Placing or shifting well part

C166S217000, C175S423000

Reexamination Certificate

active

06516889

ABSTRACT:

FIELD OF THE INVENTION
The field of this invention relates to lock mechanism for downhole use, and more specifically, to locks used in wireline applications.
BACKGROUND OF THE INVENTION
Wireline locks have been in use in the oil field for many years. These generally involve outward displacement of dogs into a receiving groove to hang on to a downhole tool. A typical prior art lock is shown in
FIGS. 1 and 2
.
FIG. 2
is a section view through the dog
10
.
FIG. 2
illustrates that the fishing neck
12
has a ramp surface
14
which in the view of
FIG. 1
cams the dogs
10
outwardly into a mating recess for engagement of the downhole tool (not shown). The position in
FIG. 1
is retained by a split ring
16
. Arrows
18
in
FIG. 2
represent the radial forces brought to bear on fishing neck
12
by the dogs
10
. Each of the dogs
10
have circumferential contact along the outer surface
20
of the fishing neck
12
thus making the direction of the force imparted from the dogs
10
to the fishing neck
12
occur principally along the normal axis as revealed by arrows
18
. Normally, the collapse load placed on the fishing neck
12
represented by arrows
18
is insufficient to collapse the fishing neck
12
. Generally speaking, pressure of axial loads on the wireline lock illustrated in
FIGS. 1 and 2
load the locking dogs
10
with the result of such dogs
10
are pushed inward. The collapse or bending load applied to the fishing neck
12
is illustrated by arrows
18
.
One problem occurs when locks of the prior art as illustrated in
FIGS. 1 and 2
are required to sustain high loads by pressure from slam closures at very high flow rates when the lock is used in conjunction with wireline safety valve. The slam closures result in abrupt pressure build up which heighten the magnitude of the bending and collapse force represented by arrows
18
. The slam closure phenomenon when combined with very large bore requirements through the lock which in turn results in a very thin cross section for the fishing neck
12
in the area of the dogs
10
which must resist such collapse force, presents a design challenge addressed by this invention.
U.S. Pat. Nos. 4,711,326; 4,762,177; 4,311,196; and 5,174,397 represent prior art known to the Applicants in the area of guidance systems for slips.
Accordingly, one of the objects of the present invention is to be able to accommodate slam closures and other downhole events which greatly heighten the applied stresses to the lock while at the same time avoiding having to lose bore size in order to provide a sufficiently thick wall to avoid collapse of the fishing neck
12
. As a result, modifications have been made to the prior art design shown in
FIGS. 1 and 2
which constitutes the present invention. The present invention objectives are to allow high loads to be transmitted from the dogs to the fishing neck in question on large sizes under high load situations without fear of collapse of the fishing neck. Those skilled in the art will appreciate the manner in which the invention solves the problem and its advantages by a review of a description of the preferred embodiment below.
SUMMARY OF THE INVENTION
A high load wireline lock features a plurality of dogs supported by a fishing neck. Radial loads, transmitted through the dogs when the lock is engaged, are in turn directed into the fishing neck in the manner so as to distribute the load into the wall of the fishing neck. The contact between the dogs and the fishing neck is along sloping surface which minimize the radial forces against the fishing neck and in turn applies forces in a near tangential direction through the wall of the fishing neck thus greatly increasing the load capacity of the wireline lock.


REFERENCES:
patent: 2698056 (1954-12-01), Marshall et al.
patent: 3677346 (1972-07-01), Tamplen
patent: 4311196 (1982-01-01), Beall et al.
patent: 4497371 (1985-02-01), Lindsey, Jr.
patent: 4554972 (1985-11-01), Merritt
patent: 4732212 (1988-03-01), Fraser, III
patent: 2158125 (1985-03-01), None

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