Gas lift valve and mandrel combination with improvement of the screening for said valve

An improved conventional type of gas lift valve and mandrel combination. It has a large area screen which encloses the valve and prevents it from having the inlet port and/or its integral small area screen, become plugged.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention concerns gas lift operations, in general, and more 
specifically it deals with an improved structure for use in combination 
with a conventional gas lift valve and mandrel unit. It provides better 
protection against plugging of the gas lift valve port. 
2. Description of the Prior Art 
A conventional type of gas lift valve structure employs a mandrel with gas 
lift valve mounted thereon. The mandrel is a coupling member that is 
fastened into a tubing string at some desired location. The structure is 
such that the gas lift valve has a relatively small sized diameter, and is 
consequently only provided with a relatively small sized port for 
accomodating the gas flow when the valve opens. Since the gas which flows 
through such port is considerable in quantity and is under relatively high 
pressure, the tendency has been found great for the port to become 
plugged. Furthermore, even though the conventional arrangement has 
included a screen element adjacent to the valve port, it has failed to 
overcome the tendency to plug since the gas flow rate has remained very 
high and thus has tended to attract and cause to stick any foreign matter 
that would plug the screen and inactivate the valve. 
Furthermore, while there have been some previous structures in connection 
with wells which dealt with the flow of fluids down hole, these have 
involved rather complex structures such that the resulting units are quite 
complex and therefore would be expensive. 
Consequently, it is an object of this invention to provide an improved 
combination of elements that relates to a conventional gas lift valve 
which is used in combination with a mandrel for mounting the valve in 
place in a tubing string. 
SUMMARY OF THE INVENTION 
Briefly, the invention concerns an improvement that relates to a 
combination with well tubing which has a gas lift valve mandrel coupled 
therewith. The combination also has a gas lift valve mounted on said 
mandrel, and the said valve has a relatively small port for admitting gas 
from the outside into the interior of said tubing during gas lift 
operations. The improvement comprises means for screening said port to 
eliminate plugging thereof, which means comprises a relatively large area 
screen covering the ingress to said port and spaced a substantial distance 
from said port. 
Again briefly, the invention concerns an improvement that relates to a 
combination with a gas lift valve mandrel adapted for being coupled with 
well tubing. The said mandrel has an integral lug protruding therefrom for 
mounting a cylindrical gas lift valve by supporting it from one end 
thereof, with its axis parallel to the axis of said mandrel. The said 
valve has a relatively small port for admitting gas from the outside to 
the interior of said mandrel, and said valve includes an integral screen 
located adjacent to said port. The improvement comprises a relatively 
large area screen being semi-cylindrical in shape and enclosing said 
valve. The said large area screen has one edge sealed against the surface 
of said lug and the other edges sealed against the surface of said 
mandrel, all whereby the plugging of said port is prevented by maintaining 
a low velocity of gas flow through said large area screen.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Gas lift operations are often employed in connection with petroleum 
production and they are usually applicable in areas where sand problems, 
highly deviated or deep wells, or overwater locations prevent efficient 
use of sucker rod or submersible pumps. The down-hole equipment for 
carrying out gas lifting operations is relatively simple. It amounts to a 
string of small ported valves used to inject pressurized gas from the 
casing side of vertical tubing into such vertical tubing so as to reduce 
the density of the fluid sufficiently for flow to occur under the 
available reservior pressure. 
Experience has shown that there is usually some debris in the vertical 
tubing/casing annulus of a well. This debris tends to consist of particles 
of packer rubber that is naturally associated with the well operation. In 
addition, there are also non-associated trash particles that inadvertently 
are trapped in the annulus of a well. Such debris often becomes entrained 
by lift-gas and so is sucked into the port of one or more of the gas lift 
valves. Consequently, it clogs such valves making them inoperable. Also, 
experience has shown that in about one-quarter of the situations where 
inproper operation of a gas lift system has been found, the problem was 
directly related to debris clogged valve ports. Correction of the problem 
results in additional reworking expense on the hole, and also a loss of 
production therefrom. 
The manufacturers of gas lift valves have attempted to deal with the 
problem of plugging. But, the relatively small area of screens that have 
been devised to cover the ports of the gas lift valves, have not changed 
the situation for the better. This has been because they (i.e. the 
screens) have also been subject to being plugged by debris in an 
equivalent manner as the ports. However, the applicants invention has 
conceived of a different approach, and thus has provided a structure that 
will substantially eliminate the plugging problem for gas lift valves of a 
conventional type. 
Referring to the figures of the drawings, it is pointed out that the 
invention involves a conventional type of gas lift valve, as mounted on a 
mandrel that is coupled into the tubing in a well. Such tubing is located 
inside of casing for the well so that there is an annulus which contains 
the gas under pressure that is employed in a gas lift operation. 
It will be understood that most gas lift operations will involve a 
substantial plurality of gas lift valves spaced vertically along a tubing 
string in the well. However, the concept of this invention is clearly 
illustrated in connection with a single gas lift valve and mandrel 
combination. 
With specific reference to the figures of the drawings, there is 
illustrated a casing 11 that surrounds a tubing string 12 which extends 
down inside of the casing 11 forming an annulus 15 therebetween. These 
elements are, of course, conventional. Also, in connection with a gas lift 
procedure, there is a gas lift mandrel 16 that is coupled into the well 
string 12. It will be understood from the foregoing that there may be a 
number of these mandrels spaced along the tubing string down hole at 
desired locations there along. Each such mandrel 16 has a gas lift valve 
17 mounted thereon. 
It may be noted again that the mandrel 16 and accompanying gas lift valve 
17 are conventional equipment that may take somewhat different form from 
that illustrated, in different instances. However, this invention is 
particularly applicable to a type of mandrel that is illustrated. It has 
the gas lift valve 17 mounted outside of the mandrel 16 and with its axis 
lying substantially parallel to the axis of the mandrel. 
As indicated in the drawings, the mandrel 16 has an integral lug 20 that 
protudes therefrom, and that has structure, e.g. a threaded hole in a flat 
surface 19, for supporting the gas lift valve 17. The internal arrangement 
(not shown) is such that the gas flow from the annulus 15 may go in 
through the valve 17 when it opens and enter the inside of the mandrel 16. 
Consequently, it goes to the inside of the tubing string 12. The interior 
passages for accomplishing this gas flow are not specifically illustrated 
since they are conventional and not relevant to the invention. 
It may be noted that it is also conventional for the gas lift valve 17 to 
have a small integrally mounted screen 21 that covers the inlet port (not 
shown) of the valve 17. It will be understood that this screen 21 is is of 
necessity quite close to the port structure of the valve 17. Consequently, 
the velocity of gas flow through the screen 21 is substantially the same 
as the velocity through the port structure, which is quite substantial as 
was indicated above. 
There is a semi-cylindrical screen 24 that encloses the valve 17. A lower 
edge 25 as viewed in FIG. 1, of the screen 24, is sealed against the 
surface of the lug 20. It may noted that the semi-cylindrical shape of the 
screen 24 is formed by its conforming with the surface of the lug 20. 
However, remaining edges 28 and 29, as well as an edge 30 (that is not in 
sight in FIG. 1) will also be fastened down and sealed to the surface of 
the mandrel 16. 
It will be appreciated that the sealing of the edges 25, 28, 29 and 30 may 
be carried out in any feasible manner, e.g. by employing flanges. Of 
course, they may be fastened down with machine screws (not shown) or the 
like. It will also be appreciated that a top surface 33, of the screen 24, 
may be formed in any feasible manner, such as by shaping the screen as it 
is mounted. 
It will be noted that the exposed area of the large screen 24 is very 
substantial. Consequently, and by reason of its displacement some distance 
away from the gas lift valve 17, the velocity of flow of the gas through 
the screen 24 will be quite low. Therefore there will be substantially no 
force tending to clog the passages through the screen, as any debris comes 
in contact or might tend to collect thereon. 
While a particular embodiment of the invention has been described above in 
considerable detail in accordance with the applicable statutes, this is 
not to be taken as in any way limiting the invention but merely as being 
descriptive thereof.