Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention. This invention involves im-
provements in methods of injecting ~reating fluid into low-pressure
oïl well formations. More specifically, this invention discloses
improved methods for treating low-pressure wells utilizing a par-
tially pressure balanced valving system. The known method of treat-
ing low-pressure wells with injection fluids utilizes several known
treating valves which have spring loaded checkvalve structure for
allowing injecting of the fluids in precontrolled amounts into the
formations.
This known method is of the type disclosed in U.S. Patent
No. 3,713,490, in the 1964-1965 World Oil Composite Catalog, pages
3680 and 3681, and in the Burt U.S. Patent No. RE 22,483. Appa-
ratus useful in the known method of fluid injection is of the type
as disclosed in U.S. Patent Nos. 2,268,010, RE 22,483, and U.S. ~ -
3,802,507.
The above mentioned method and valving devices utilize a
coil spring biasing means on a checkvalve member to provide well
injection valve service. The basic disadvantage with these devices
and their method of operation is that the biasing means utilized
must be of sufficient strength to provide a biasing force exceed-
~25 ing the hydrostatic pressure of the column of fluid in the tubing
above the valve.
In some of the deeper wells, this results in having to
use a very heavy and stiff biasing spring to obtain proper opera-
tion of the injection valve. Because of this requirement, the
Q valve usually operates very few times successfully and becomes
weakened or bxeaks during the method of operation.
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As an alternative to the extremely heavy and
stiff spring, some valve manufacturers have tried to use
extremely small valve seat areas to reduce the force of
hydrostatic pressure on the spring. Since the resultant
downward force on the spring is determined by the pressure
above the valve member, multiplied by the cross-sectional
area of the valve flow area it is applied to, these designs
were made with small flow areas to reduce the downward
force of the column of fluid.
While these designs were partially successful
in reducing spring failure, they resulted in causing an
even greater problem and that involved plugging of the
valve flow area. Since most tubing contains some sediment,
scale, rust and other foreign matter, the injection of
treating fluids and acids down the tubing always breaks
loose a quantity of this material which accumulates at ~ -
the valve mechanism and effectively plugs it up.
The present invention resides in a method of
injecting fluids into an underground formation penetrated
by a wellbore and includes the step of predetermining
the hydrostatic pressure of a column of a fluid having
a height equal to the depth of the underground formation.
A continuously partially pressure-balanced injection valve
is provided which has a resultant differential pressure
area responsive to the hydrostatic pressure of a column
of fluid thereabove to open the valve, and having an
adjustable bia~ing means arranged to apply a closing
force to the valve. The injection valve biasing means
i8 adjusted to a force exceeding the resultant differential
pressure on the valve which would arise from the pre-
determined hydrostatic pressure. The injection valve ~ ~ -
is located in a tubing string in the underground
, ~ formation and treating fluid is placed in the tubing
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string to be injected into the formation. Any remaining
portion of the tubing string is filed with displacement
fluid, and fluid pressure is applied to the tubing string
to open the injection valve and inject the treating
fluid into the formation.
According to another aspect of the invention,
there is provided a method of injecting through a wellbore
a precisely controlled amount of fluid into an under-
ground formation having a formation pressure substantially
less than the hydrostatic pressure of a full column of ~ -
fluid in the wellbore above the formation. The method
includes the steps of locating in the wellbore a tubing
string having flow port means near the formation and
placing in the tubing string near the formation and extending
above the flow port means a valve member having a first
pressure response area open to the tubing string, in
valving relationship therein, and responsive to fluid
~ pressure in the tubing string. The tubing string is
simultaneously communicated to a second, lesser pressure
response area on the valve member opposing the first area,
and the valve member is continuously and resiliently
biased towards a closed position in the tubing string
with a hiasing force exceeding the differential pressure
force from a full column of fluid in the tubing above
the valve member acting on the difference in area be~
tween the first and second pressure response areas.
The desired injection volume of fluid is then pumped into
the full tubing with sufficient pressure to overcome the
resilient biasing force and open the valve member.
The present invention overcomes the above- ~ -
described disadvantages by providing a method wherein
fluid may be injected into a well through apparatus
utilizing only a moderate biasing force to hold the
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hydrostatic pressure of the column of fluid in thetubing. This method utilizes a partial pressure balancing
of the valving mechanism to reduce the hydrostatic force
on the biasing means and prevent plugging of the valve
flow area.
Brief Description of the Drawings. Figure 1 is
a schematic cross-sectional view of the injection valve
assembly utilized in this invention.
Figure 2 is a partial schematic cross-sectional
illustration of an alternate structure for use in the
method of this invention.
Description of the Preferred Embodiments. Refer-
ring now to Figure 1, the pressure-balanced service valve
10 is shown in cross-section having a generally tubular
elongated body 11 in which is slidably located a valve
member 12. A compression coil spring
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13 abuts valve member 12 and urges valve member 12 into sealing
engagement with valve seat 14 secured to the inner wall of housing
11. A slidable abutment base 15 is located in the bottom of hous-
ing 11 and is sealingly engaged therein by means of circular seal
16. Abutment base 15 provides a slidable base for the abutment of
spring 13. A housing cap 17 is secured at the lower end of housing
11 and closes off the bore passage therethrough. A threaded adjust-
ment member 18 is threadedly engaged in cap 17 extending upward in-
to housing 11 for abutment with base 15 to provide compression ad-
justments for spring 13.
Likewise, valve member 12 has a widened base 19 to pro-
vide an abutment surface for the upward end of coil spring 13.
Valve member 12 comprises upper generally spherical seating end
12a, an elongated generally cylindrical valve body 12b, and the
aforementioned spring abutment face 19 at the lower end thereof.
Housing 11 has an inwardly projecting shoulder 20 forming an annu-
lar partition in housing 11 through which member 12 passes, with
section 12b being in close proximity to the inner bore 21 in parti-
tion 20. One or more circular seals 22 are provided in grooves 23
in inner bore 21 which circular seals sealingly contact elongated
valve body 12b. ;~
The inner bore passage 24 of the tubing string i8 di-
vided by the annular sealing shoulder 14 and sealing partition 20
into a valve flow chamber 25 and a pressure-balance chamber 26.
Flow of fluids down the tubing string 27 may progress through bore
24 and chamber 25 into the formation and flow by means of a bypass
channel 28 into chamber 26. Fluids in chamber 26 are restricted
therein by the various seal members 16 and 22 so that no fluid may
escape therefrom.
Likewise, fluid flow between chambers 25 and 26 is also
prohibited. The flow of fluids through bypass channel 28 from
bore pas~age 24 to pressure chamber 26 results in a pressure force
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upward on member 12 which is directly proportional to the area
swept by circular seals 22, said area being designated in Figure 1
by the dimension A2 and being circular in shape or corresponding
in shape to the cross-sectional configuration of section 12b of
valve member 12.
Likewise, a downward pressure occurs across the area
atop valve member 12a, which pressure is equivalent to the area of
the opening in valve seating shoulder 14, said area being desig-
nated at A . The total resultant pressure acting on valve member
12 is thus related to the difference in areas Al and A2. This is
respresented by the relation F = P(Al - A2).
Thus, it can be seen that by varying the areas Al and
A2 the resultant differential pressure on valve member 12 may be
made as large or as small a proportion of the downward p~essure in
the tubing as required or desirable. In a deepwell requiring a
high hydrostatic pressure in the tubing because of the height of
the fluid column therein, the difference Al - A2 would advanta- --
geously be made small because of the high pressure involved. In a ~ -
shallower well, the difference Al - A2 would preferably be made
larger. Thus, the biasing force upward provided by spring 13 to
maintain member 12 seated in valve seat 14 prior to the injection
operation need only be an amount greater than the resultant dif-
ferential pressure acting downward on valve member 12. As an al-
ternative to altering the pressure differential area Al - A2 for
different depts of use, it is clear that a single value of Al - A2
for generally mid-range depths may be selected and a fine tuning
of the valve for each individual well depth may be obtained by the
adjustment of threaded abutment screw 18 upward or downward as the
case may be.
For the deeper wells, screw 18 is threaded upward to fur-
ther compress biasing spring 13 and provide a greater biasing force
against the greater hydro~tatic head of the fluid column in the tub-
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ing. In the shallower wells, screw 18 should be threaded downward
to relieve a portion of the biasing force of spring 13 upward
against valve member 12 due to the lesser hydrostatic head of the
shorter column of fluid in the tubing.
In typical operation, when it is desirable to place a
treating fluid on the face of a formation with this invention, the
characteristics of the formation including the formation pressure
and formation depth are utilized to calculate the hydrostatic head
of the fluid that will exist with a full column of fluid in the
tubing. From these calculations, the downward resulting differen-
tial pressure on valve member 12 is calculated using the formula
P x (Al - A2) and the amount of spring biasing force re~uired to
overcome this is introduced by the adjustment of spring 18 against
spring base 15 thereby compressing spring 13 to the calculated ex-
tent. This establishes a biasing force against valve member 12
calculated to be greater than the resulting downward pressure on ~-
member 12 when the valve is in place opposite the formation with a
column of fluid thereabove.
The valve is then placed at the lower end of the tubing
string below a standard packer such as that disclosed in U.S. Pat-
ent No. 3,548,936 to Kilgore et al, dated December 22, 1970 and U.S.
Patent No. 3,701,382 to Williams, dated October 31, 1972. A bypass
valve in the packer is opened and the string is run in the hole
with the well fluid being allowed to flow through the bypass valve
in the packer and into the tubing string to offset buoyancy of the
string. After the string is located properly, with the injection
valve 10 in close proximity to the formation face, the packer is
set by means such as wireline set, mechanical manipulation of the
tubing, or hydraulic set, a~d the annulus below the packer near the
formation is isolated from the rest of the annulus above the for-
mation.
It may then be desirable to circulate out the well fluid
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existing in the isolated area of the annulus to prevent contamina-
tion of the formation by this fluid. This may be accomplished by
opening a bypass valve in the packer and pumping the treating fluid
into the tubing thereby displacing the well fluid up through the
bypass valve into the annulus above the packer. The pumping of
fluid through valve 10 during this displacement is accomplished by
pressuring the tubing a sufficient amount to overcome the result-
ant biasing force upward on spring 13 on member 12, thereby forc-
ing member 12 downward through partition 20, opening the bore
through seat 14 and communicating ports 30 in the wall of housing
11 with flow area Al. -
After displacement of the well fluid has occurred and it
is calculated the treating fluid has reached valve 10 and into the
isolated area of the annulus, the bypass valve in the packer is
closed by manipulation of the string or by other known means and
injection of the treating fluid into the formation is accomplished
by either continuing the fluid pressure on the tubing or else by
increasing the pressure on the tubing to provide a faster injection
rate. After the calculated desirable amount of treating fluid has
been injected into the formation, it is usually desirable to allow
the fluid to set in the formation an extended period of time to
maximize the desirable effect gained from the treating fluid. This
may be done by releasing pressure on the tubing which thus removes ~ -
a major portion of the resulting downward differential pressure on
valve member 12. The remaining differential pressure on 12 is in-
sufficient to maintain spring 13 compressed and thereby spring 12
moves back upward to set in seat 14 closing off flow from the for- -
mation bac~ through the tubing string.
After the treating fluid has been held in the formation
the desired period of time, the fluid may be removed from the for-
mation either by means of a shear sleeve or other type of circulat-
ing valve between the packer and the injection valve 10 or else
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the bypass valve through the packer may be opened to allow the
fluid to move back up the annulus. After the fluid has been re-
moved from the formation, the string may be pulled from the casing
and the treating valve removed from the tubing string to be reused
in other wells an indefinite number of times. Thus, it can be
seen that by using a pressure relief bypass channel 28, the hy-
drostatic pressure in the tubing string may be communicated with
the lower side of the valve member as well as the upper side and,
by proper selection of the pressure areas on valve member, a desir-
able differential area A - A may be established requiring only a
relatively resilient low force biasing spring 13 to overcome the
downward pressure on member 25 arising from the hydrostatic head.
By utilizing a hydrostatic balancing chamber 26 isolated from the
flow chamber 25 yet in communication with member 12, a partial
pressure-balancing of member 12 may be achieved in order to offset
a large portion of the downward hydrostatic pressure existing
under the column of fluid in the tubing without allowing any of
the fluid to leak out of the pressure-balancing area and into the -
flow area.
Referring now to Figure 2, a partial cross-sectional
area of flow member 10 is shown wherein a modification of flow
ports 30 is disclosed. In the embodiment of Figure 1, a number of
ports 30 through the wall of housing 11 may be varied from one to
as many as will fit the periphery of the housing around chamber 25.
Preferably, the flow areas through ports 30 are made as large as
structurely feasible to provide as low resistance flow as possible.
In the second embodiment in Figure 2, a modification of
the flow ports 30 is provided to obtain additional action from the
treating fluid in the formation area. -In this embodiment, the
number and location of flow port means through the wall of hous-
ing 30 are more critical than the location and configuration of
ports in Figure 1. In this embodiment, a number of spraying noz-
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zels 31 are secured in the port openings 30 by means such as weld-
ing or threading. The spray nozzels are directed at the formation
face and into the annular area around valve 10 so that during the
injection of the treating fluid, the fluid is sprayed into the
formation face and around the tool to provide a washing jet action
to further increase the desirable effects of the treating fluid on
the formation. For instance, in some of the wells to be treated,
one of the problems attempted to be overcome involves the build-up
of paraffin in the formation flow area and in the perforations in
the casing. The build-up of paraffin can greatly reduce and even
stop the flow of hydrocarbons from the formation into the borehole.
Some paraffin build-ups are extremely hard to dissolve and the
treating fluids must be strong and must be left in place a great
period of time to be effective against such build-ups.
In these circumstances, use of the embodiment in Figure
2 i8 particularly advantageous in that the agitation of the treat-
ing fluid against the formation face serves to increase many-fold
the action of the fluid on the paraffin deposits. Operation of
the tool of Figure 2 is substantially identical to that of the
embodiment of Figure 1.
The jetting system of Figure 2 iS also useful for allow-
ing a washing action on the formation after the injection treatment
has been accomplished. A washing fluid may be injected behind the
treating fluid and sprayed through jets 31 against the formation to
remove sediment, deposits, and residue from the injection treatment.
Although certain preferred embodiments of the present invention
have been herein described in order to provide an understanding of
the general principles of the invention, it will be appreciated
that various changes and innovations can be affected in the de- -
scribed valve structure without departure from these principles.
For example, whereas a method utilizing a vertically upward acting
valve member is disclosed, it is clear that the method also encom-
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passes the use of said structure in an inverted configuration fromthat shown with a biasing means pushing the valve member downward
and the resulting partial differential pressure on the valve member
resulting in an upward force from the hydrostatic fluid pressure.
Thus, all modifications and changes of this type are deemed to be
embraced by the spirit and scope of the invention except as the
same may be necessarily limited by the appended claims or reasonable
equivalence thereof.
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