Downhole pump with pressure limiter

A well testing assembly includes a pressure limiter located between a downhole pump and an inflatable packer. The pressure limiter includes a housing having first and second housing parts and having an inflation passage disposed therein for communicating a discharge of the downhole pump with the inflatable packer. A clutch is connected between the first and second housing parts. A biasing spring biases the clutch toward an engaged position. A piston is operatively associated with the clutch and communicated with the inflation passage for overcoming the biasing spring and moving the clutch to a disengaged position at a predetermined fluid pressure level within the inflation passage.

The present invention relates generally to pressure limiters for downhole 
pumps, and more particularly, but not by way of limitation, for pressure 
limiters for limiting an inflation pressure communicated from a downhole 
pump to an inflatable packer. 
The pressure limiter of the present invention is constructed for use with a 
downhole pump of the type having first and second pump parts with relative 
rotation between said first and second pump parts being required to 
operate the pump and discharge a fluid under pressure therefrom. 
Two examples of such pumps are shown in U.S. Pat. No. 3,926,254 to Evans et 
al., and assigned to the assignee of the present invention, and U.S. Pat. 
No. 3,439,740 to Conover. 
The Evans et al. patent discloses a relief valve type of pressure limiting 
device designated as a limit valve member 242 and that member is described 
in detail at column 8, lines 6-61 of the Evans et al. disclosure. 
The pressure limiter of the present invention is preferably utilized with 
an improved version of such pumps disclosed in my co-pending U.S. patent 
application No. 057,093 filed July 12, 1979, entitled "Downhole Pump and 
Testing Apparatus" and assigned to the assignee of the present invention. 
A pressure limiting device which has previously been used by the assignee 
of the present invention for over one year, with downhole pumps such as 
that of Evans et al. and of my co-pending application Ser. No. 057,093, is 
a spring loaded torque limiting device which is run above the downhole 
pump to limit the torque which can be transferred thereto by the rotating 
drill string. That device operates on a ratcheting principle wherein a 
maximum torque which can be transferred between two components thereof is 
determined by the frictional force required to slide or ratchet two parts 
thereof relative to each other, which frictional force is determined by a 
normal force dependent upon the compression of a spring member thereof. 
Other downhole pumps and packer assemblies for well testing are disclosed 
in U.S. Pat. No. 3,291,219 to Nutter, U.S. Pat. No. 3,083,774 to Peters et 
al., and U.S. Pat. No. 2,690,224 to Roberts, which disclosures are not 
believed to be as relevant as the Evans, et al. and Conover devices 
discussed in more detail above. 
The present invention provides a pressure limiter including a housing 
having first and second housing parts and having a fluid passage means 
disposed therein for communication with a discharge of a downhole pump. A 
clutch means is connected to the first and second housing parts and is 
movable between an engaged position for preventing relative rotational 
movement between the first and second housing parts and a disengaged 
position for allowing relative rotational movement between said first and 
second housing parts. 
A biasing means is operatively associated with the clutch means for biasing 
the clutch means towards its engaged position. Piston means are provided 
and are operably associated with the clutch means and are communicated 
with the fluid passageway, for overcoming the biasing means and moving the 
clutch means to its disengaged position at a predetermined fluid pressure 
level within the fluid passageway.

Referring now to FIG. 9, a well testing assembly of the present invention, 
generally designated by the numeral 10, is thereshown in place within a 
well hole 12. 
The well testing assembly 10 includes a pipe string 14, the upper end of 
which is connected to a conventional rotary drilling rig (not shown) 
located at the surface and the lower end of which is connected to a 
downhole pump 16. 
The downhole pump 16 includes an upper pump portion 18 and a lower pump 
portion 20. The upper and lower pump portions 18 and 20 are operably 
associated so that the pump 16 is operated on relative rotational movement 
between upper and lower pump portions 18 and 20. As mentioned, the 
downhole pump 16 may be constructed in a manner similar to any of U.S. 
Pat. No. 3,926,254 to Evans et al., U.S. Pat. No. 3,439,740 to Conover, 
and may co-pending U.S. patent application Ser. No. 057,093, all of which 
are incorporated herein by reference. 
When the lower pump portion 20 is held fixed relative to well hole 12 and 
the upper pump portion 18 is rotated by rotation of the pipe string 10, 
the pump 16 operates to produce fluid under pressure. If the lower pump 
portion 20 is not fixed relative to well hole 12, and instead is allowed 
to rotate with upper pump portion 18 when pipe string 10 is rotated, then 
the pump 16 does not operate and no pressurized fluid is produced thereby. 
Connected to the lower pump portion 20 is an intake screen assembly 22 
through which fluid from an annulus 24 between pipe string 10 and well 
hole 12 is drawn to the suction side of downhole pump 16. 
Connected to the lower end of screen assembly 22, and to the lower pump 
portion 20 through the screen assembly 22, is the pressure limiter 26 of 
the present invention, which includes a housing 28 having an upper housing 
part 30 and a lower housing part 32. 
Connected below pressure limiter 26 are a first inflatable packer 34 and a 
second inflatable packer 36, which have a perforated intake portion 38 
located therebetween adjacent a subsurface formation 39, the production of 
which is to be tested by the well testing assembly 10. 
Located below the second inflatable packer 36 is a conventional drag spring 
assembly 40 which resiliently engages the wall of well hole 12 to prevent 
rotation of those components attached thereto relative to well hole 12. 
The general manner of operation of the well testing assembly 10 is similar 
to that described in detail in U.S. Pat. No. 3,926,254 to Evans et al. and 
illustrated in the schematic FIGS. 1-5 thereof. An additional feature 
provided to this operation by the pressure limiter of the present 
invention is that upon the inflation pressure from the pump discharge to 
the inflatable packers reaching a predetermined level, the pressure 
limiter of the present invention disengages a clutch means contained 
therein to allow the upper housing part 30 to rotate relative to the lower 
housing part 32 thereby permitting the lower pump part 20 to rotate with 
the upper pump part 18 so as to prevent further increase of the inflation 
pressure by the pump means 16. 
Referring now to FIGS. 1A-1D which comprise a sectioned elevation right 
side only view of a preferred embodiment of the pressure limiter 26 of the 
present invention, the details of construction of the housing 28 and its 
upper and lower parts 30 and 32 are thereshown. 
The upper housing part 30 includes an upper adapter 42 and an upper mandrel 
44 connected at threaded engagement 46 with a seal therebetween provided 
by seals 48. 
An upper end 50 of upper mandrel 44 is also connected to a seal mandrel 52 
at threaded connection 54. 
Upper housing part 30 further includes a splined mandrel 56 comprising 
upper and lower splined mandrel portions 58 and 60, respectively, 
connected together at threaded connection 62. A seal is provided between 
upper and lower splined mandrel portions 58 and 60 by annular sealing ring 
64. 
Also included in the upper housing part 30 is a mandrel stinger 66 attached 
to the lower end of splined mandrel 56 at threaded connection 68. 
Further included in upper housing part 30 is a clutch mandrel 70 which is 
concentrically disposed about lower splined mandrel portion 60 and which 
is connected thereto by an interlocking means 72 comprising splines 74 and 
76 on lower splined mandrel portion 60 and clutch mandrel 70, 
respectively, for preventing relative rotational movement between splined 
mandrel 56 and clutch mandrel 70 while allowing relative longitudinal 
movement therebetween. 
A central flow tube 78 has its upper end closely received within an inner 
cylindrical surface 80 of seal mandrel 52 and has its lower end closely 
received within an inner cylindrical surface 82 of mandrel stinger 66. 
The lower housing part 32 of housing 28 of pressure limiter 26 includes a 
bearing retainer 84 connected to a bearing housing 86 at threaded 
connection 88. Also included is a spring case 90 attached to the lower end 
of bearing housing 86 at threaded connection 92. 
Lower housing part 32 further includes a clutch housing 94 connected to the 
lower end of spring case 90 at threaded connection 96, and a lower adapter 
98 connected to clutch housing 94 at threaded connection 100. 
A lower end of mandrel stinger 66 of upper housing part 30 is closely 
received within an inner bore 102 of lower adapter 98 of lower housing 
portion 32, and a seal therebetween is provided by seal means 104. 
The housing 28 of pressure limiter 26 has an inflation passage 106 disposed 
therethrough for communicating a discharge of downhole pump 16 with the 
inflatable packers 34 and 36. The inflation passage 106 includes an 
annular space 108 between seal mandrel 52 and upper adapter 42, a skewed 
port 110 disposed through a side wall of seal mandrel 52, an annular space 
112 between flow tube 78 and an inner bore 114 of upper housing part 30, 
ports 115 and 116 through a wall of lower splined mandrel portion 60, an 
irregular annular space 118 between upper housing part 30 and lower 
housing part 32, and a longitudinal hole 120 communicated with the lower 
end of lower adapter 98. 
A shoulder 119 at the upper end of upper splined mandrel portion 58 of 
upper housing part 30 is rotatingly mounted within lower housing part 32 
by bearing blocks 121 and 123. 
A clutch means generally designated by the numeral 122 is connected to 
upper and lower housing parts 30 and 32 and is movable between an engaged 
position illustrated in FIG. 1D for preventing relative rotational 
movement between upper and lower housing parts 30 and 32, and for holding 
lower pump portion 20 fixed relative to well hole 12 so that the downhole 
pump 16 is operated upon rotation of pipe string 10, and a disengaged 
position for allowing relative rotational movement between upper and lower 
housing parts 30 and 32, and for allowing lower pump portion 20 to rotate 
with the upper pump portion 18 upon rotation of pipe string 10 to prevent 
operation of the downhole pump 16. 
The clutch means 122 includes an upper clutch part 124 attached to clutch 
mandrel 70 of upper housing part 30, and a lower clutch part 126 attached 
to lower adapter 98 of lower housing part 32 at threaded connection 128. 
Referring now to FIGS. 3-5 and FIGS. 6-8, the details of construction of 
upper and lower clutch parts 124 and 126, respectively, are thereshown. 
Upper clutch part 124 includes a lower annular surface 130 with a first 
pair of diametrically opposed longitudinally downward extending lugs 132 
and 134 disposed thereon. 
Lower clutch part 126 includes an upper annular surface 136 with a second 
pair of diametrically opposed longitudinally upward extending lugs 138 and 
140 disposed thereon. 
Referring to FIGS. 4 and 5, the lug 134 of the first pair has a flat bottom 
surface 142, a vertical right side surface 144 and a sloped left side 
surface 146. The other lug 132 of the first pair of lugs disposed on upper 
clutch part 124 is similarly constructed. 
Referring now to FIGS. 7 and 8, and particularly to FIG. 7, the lug 140 of 
the second pair of lugs has a flat top surface 148, a vertical left side 
surface 150, and a sloped right side surface 152. The other lug 138 of the 
second pair of lugs disposed on lower clutch part 126 is similarly 
constructed. 
When the first and second clutch parts 124 and 126 are engaged as shown in 
FIG. 1D, the bottom surfaces 142 of the first pair of lugs engage the 
annular surface 136 of the lower clutch part 126, and the top surfaces 148 
of the lugs 138 and 140 of the lower clutch part 126 engage the lower 
annular surface 130 of the upper clutch part 124. Upon right hand rotation 
of the drill string 10, the upper clutch part 124 is rotated clockwise as 
viewed from above and the sloped surfaces 146 of lugs 132 and 134 are 
moved into engagement with the sloped surfaces 152 of lugs 138 and 140 so 
that the continued engagement of sloped surfaces 146 with sloped surfaces 
152 prevents rotation of upper clutch part 124 relative to lower clutch 
part 126. 
The sloped surfaces 146 and 152 on the first and second pairs of lugs 
create a longitudinal force component therebetween urging the first and 
second pair of lugs, and the upper and lower clutch parts 124 and 126, 
toward a disengaged position when a torque is transmitted across said 
sloped surfaces. This feature assists in the disengagement of the lugs of 
upper and lower clutch parts 124 and 126. If the engaging surfaces of the 
lugs were vertical, the frictional force therebetween due to the torque 
being transmitted thereacross would affect the longitudinal separating 
force required to move the upper and lower clutch parts 124 and 126 apart 
to a separated disengaged position. 
The sloped surfaces 146 and 152 are preferably sloped at an angle of 
approximately 45.degree. to the longitudinal axis of pressure limiter 26. 
Referring now to FIG. 1C, a biasing means 154, which is a coil compression 
spring, is operatively associated with the clutch means 122 for biasing 
the clutch means towards its engaged position. Biasing means 154 includes 
upper and lower ends 156 and 158, respectively, both of which engage 
components of the upper housing part 30. 
More specifically, the lower end 158 of coil compression spring 154 engages 
an annular radially inward extending upward facing shoulder 160 of clutch 
mandrel 70, and upper end 156 of coil compression spring 154 engages an 
annular radially outward extending downward facing shoulder 162 of lower 
splined mandrel portion 60. The lower splined mandrel portion 160 may 
generally be referred to as an inner mandrel relative to the clutch 
mandrel 70 since lower splined mandrel portion 60 is received within the 
clutch mandrel 70. 
Clutch mandrel 70 includes an upper inner cylindrical surface 164 within 
which is closely received an outer cylindrical surface 166 of lower 
splined mandrel portion 60. Sealing means 168 are disposed between 
surfaces 164 and 166. 
Clutch mandrel 70 further includes a lower outer cylindrical surface 170 
closely received within an inner cylindrical surface 172 of clutch housing 
94 of lower housing part 32. Sealing means 174 are disposed between 
surfaces 170 and 172. 
The diameter of outer cylindrical surface 170 of clutch mandrel 70 is 
greater than the diameter of inner cylindrical surface 164 of clutch 
mandrel 70 so that an annular differential area piston means 176 is 
defined on clutch mandrel 70. The piston means 176 is communicated with 
inflation passage 106 and is operably associated with the clutch means 122 
through the clutch mandrel 70 for overcoming the downward biasing force 
exerted upon clutch mandrel 70 by coil compression spring 154, and for 
moving the clutch means 122 to its disengaged position at a predetermined 
fluid pressure level, preferably about 1500 p.s.i., within inflation 
passage 106. The pressure within inflation passage 106 acting upward 
against the annular differential area of piston means 176 urges the clutch 
mandrel 70 upward against the downward force exerted by coil compression 
spring 154. 
The differential area of piston means 176 has an inner diameter defined by 
the diameter of inner cylindrical surface 164 of clutch mandrel 70 and an 
outer diameter defined by the diameter of outer cylindrical surface 170 of 
clutch mandrel 70. 
It will be appreciated by those skilled in the art that there is a slight 
clearance between inner cylindrical surface 164 and the outer cylindrical 
surface 166 of lower splined mandrel portion 60 received therein, and a 
similar slight clearance between outer cylindrical surface 170 of clutch 
mandrel 70 and inner cylindrical surface 172 of clutch housing 94. These 
clearances are sealed by the resilient O-ring sealing means 168 and 174, 
respectively. The actual inner and outer diameters defining the annular 
differential area of piston means 176 are exactly defined by the diameter 
at which the respective sealing means 168 and 174 engage outer cylindrical 
surface 166 and outer cylindrical surface 170. It will be understood by 
those skilled in the art that the sealing means may be disposed in grooves 
in either of two closely engaging cylindrical surfaces and the slight 
clearance therebetween does not substantially affect the area of annular 
surface 176. Thus, when it is said that the inner diameter of annular 
differential area piston means 176 is defined by the diameter of inner 
cylindrical surface 164 at the upper end of clutch mandrel 70, it is 
understood that the actual inner diameter of the effective annular 
differential area piston means 176 is defined by the diameter of the 
surface slidingly and sealingly engaged by seals 168 which diameter may 
vary by the clearance between surfaces 164 and 166 depending upon whether 
the seals are disposed in grooves in surface 164 or in surface 166. 
The components of the pressure limiter 26 are so arranged and constructed 
that when the fluid discharge pressure, from downhole pump 16, within the 
inflation passage 106 is below a predetermined level, the coil spring 
biasing means 154 urges the upper clutch part 124 downward into engagement 
with the lower clutch part 126 to prevent relative rotational movement 
between the upper and lower housing parts 30 and 32. When said fluid 
discharge pressure is above said predetermined level, the upward force of 
said pressure within the inflation passage 106 acting against the annular 
differential area of piston means 176 moves the clutch mandrel 70 upward 
overcoming the biasing force of spring 154 and moves the lugs 132 and 134 
of upper clutch part 124 upward out of engagement with the lugs 138 and 
140 of lower clutch part 126 to thereby allow relative rotational movement 
between the upper and lower housing parts 30 and 32. 
Referring now to FIGS. 2A-2D, an alternative embodiment of the pressure 
limiter of the present invention is thereshown and generally designated by 
the numeral 26A. Components of the pressure limiter 26A of FIGS. 2A-2D 
which are substantially identical to corresponding components of the 
pressure limiter 26 of FIGS. 1A-1D are designated by the identical 
numerals. Similar components which have been modified are designated by 
the original numeral with the addition of the suffix "A". 
A primary distinction between the pressure limiters 26A and 26 is shown in 
FIG. 2C where it can be seen that the lower end 158A of the coil 
compression spring 154A engages an upward facing shoulder 160A of clutch 
mandrel 70A while the upper end 156A of spring 154A engages a downward 
facing annular shoulder 200 of bearing housing 86A of lower housing part 
32A. 
The lower end 158A previously designated of spring 154A is actually a 
bottom surface of a spacer ring 202 which is placed between a lower coil 
204 of spring 154A and the shoulder 160A of clutch mandrel 70 to vary the 
initial compression of coil spring 154A. 
Thus, it is seen that the lower and upper ends 158A and 156A of the coil 
compression spring 154A engage the upper and lower housing parts 30A and 
32A, respectively. 
While this arrangement provides the same general manner of operation of the 
pressure limiter 26 of FIGS. 1A-1D, it is generally not as desirable 
because of the relative rotation between the surfaces, i.e. the shoulders 
160A and 200, engaging the ends of the coil compression spring 154A. The 
embodiment of FIGS. 1A-1D eliminates this problem by having both ends of 
its coil compression spring 154 engaging a single one, i.e. the upper 
housing part 30, of the upper and lower housing parts 30 and 32 thereof. 
The clutch mandrel 70A includes upper and lower outer cylindrical surfaces 
206 and 170A, respectively, closely received within first and second inner 
cylindrical surfaces 208 and 172 of lower housing part 32A. 
Seals 210 are provided between surfaces 206 and 208. Seals 174 are provided 
between surfaces 170A and 172. The annular differential surface of piston 
means 176A is therefore defined between an inner diameter defined by the 
diameter of upper outer cylindrical surface 206A of clutch mandrel 70A and 
an outer diameter defined by the diameter of lower outer cylindrical 
surface 170A of clutch mandrel 70A. 
The general manner of operation of either of the pressure limiters 26 or 
26A of the present invention, in combination with other components of the 
well testing assembly 10 as shown in FIG. 9, may therefore be generally 
described as follows. 
The well testing assembly 10 is assembled in the manner shown and described 
with relation to FIG. 9, and is then lowered into place within the well 
hole 10 until the intake assembly 38 is located adjacent a subsurface 
formation 39, the production characteristics of which are to be tested. 
The clutch assembly 122 is initially maintained in its engaged position as 
shown in FIG. 1D, due to the biasing from spring 154. This locks the lower 
pump portion 20 and all the components located therebelow relative to the 
well hole 12 so that upon rotation of the pipe string 10, the lower pump 
portion 20 is held in place and the upper pump portion 18 rotates relative 
thereto, thereby operating the pump 16 to produce pressurized fluid at the 
discharge thereof. This fluid is communicated through the inflation 
passage 106 to the inflatable packers 34 and 36 to inflate the same. 
After the packers are inflated and the annulus 24 is sealed, the fluid 
pressure within the packers and within the inflation passage 106 
communicating with the discharge of pump 16 rapidly increases with further 
operation of the pump 16. When this inflation pressure reaches the 
predetermined level, the upward force of this inflation pressure acting 
against the differential area piston means 176 moves the clutch mandrel 70 
and the upper clutch part 124 upward relative to the lower clutch part 126 
thereby disengaging the clutch means 122 so that the upper housing part 30 
may rotate relative to the lower housing part 32. Since the lower pump 
part 20 and screen 22 are connected to the upper housing part 30 of 
pressure limiter 26, this also allows the lower pump part 20 to rotate 
with the upper pump part 18 as the pipe string 10 continues to be rotated. 
Since there is no further relative rotational movement between the upper 
and lower pump parts 18 and 20 the pump 16 ceases to operate and the 
discharge pressure within inflation passage 106 does not further increase. 
Thus, it is seen that the downhole pump with pressure limiter of the 
present invention is readily adapted to achieve the ends and advantages 
mentioned as well as those inherent therein. While certain preferred 
embodiments of the invention have been illustrated for the purpose of this 
disclosure, numerous changes in the arrangement and construction of parts 
may be made by those skilled in the art which changes are included within 
the scope and spirit of this invention as defined by the appended claims.