BAKER HUGHES INCORPORATED
`Exhibit 1026
`Page 1 of 9
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`Page 3 of 9
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`Page 4 of 9
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`US 6,230,231 1 B1
`
`1
`INTERNAL PRESSURE OPERATED
`CIRCULATING VALVE WITH ANNULUS
`PRESSURE OPERATED SAFETY MANDREL
`
`TECHNICAL FIELD OF THE INVENTION
`
`to an apparatus and
`This invention relates, in general,
`method used during formation testing and, in particular to,
`an internal pressure operated circulating valve that is placed
`in the operating position only if sufficient annular hydro-
`static pressure unlocks a safety mandrel.
`
`BACKGROUND OF THE INVENTION
`
`Without limiting the scope of the present invention, its
`background is described in connection with performing tests
`to determine the production capabilities of a formation
`traversed by a wellbore, as an example.
`the
`During the course of drilling an oil or gas well,
`wellbore is typically filled with a fluid known as drilling
`fluid or drilling mud. One of the purposes of this drilling
`fluid is to contain formation fluids within the formation
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`intersected by the wellbore. To contain these formation
`fluids, the drilling mud is weighted with various additives so
`that
`the hydrostatic pressure of the drilling mud at
`the
`formation depth is sufficient to maintain the formation fluid ’
`within the formation without allowing it to escape into the
`wellbore.
`
`When it is desired to test the production capabilities of the
`formation, a test string is lowered into the wellbore to the
`formation depth and the formation fluid is allowed to flow
`into the test string in a controlled testing program. Lower
`pressure is maintained in the interior of the test string as it
`is lowered into the wellbore. This is usually done by keeping
`a valve in the closed position near the lower end of the test
`string. When the testing depth is reached, a packer is set to
`seal the wellbore thus closing in the formation from the
`hydrostatic pressure of the drilling fluid in the well annulus.
`The valve at the lower end of the test string is then opened
`and the formation fluid, free from the restraining pressure of
`the drilling fluid, can flow ir1to the interior of the test string.
`The testing program typically includes periods of forma-
`tion flow and periods when the formation is closed in.
`Pressure recordings are taken throughout the program for
`later analysis to determine the production capability of the
`formation. If desired, a sample of the formation fluid may be
`caught in a suitable sample chamber.
`At the end of the testing program, a circulation valve in
`the test string is typically opened so that formation fluid in
`the test string may be circulated out. Since the hydrostatic
`pressure of the drilling fluid near the formation is generally
`much higher than the formation fluids in the test string, it is
`usually only necessary that the annulus be placed in fluid
`communication with the interior of the test string to start to
`reverse out the formation fluids from the test string. Fol-
`lowing this circulation step, the packer may be released so
`that the test string may be withdrawn from the wellbore.
`Typically, the circulating valves used in a test string may
`include a sliding sleeve that
`is opened in response to
`pressure in the annulus. It has been found, however, that
`when it is desirable to have more than one circulating valves
`in a test string to be operated at different times, each tool
`must be set to operate at a different pressure. Since 500 psi
`typically separates the pressures at which respective circu-
`lating valves will operate, extremely high pressures would
`be required to operate the later circulating valves in such a
`configuration, which may damage the well casing.
`
`2
`To overcome this problem, attempts have been made to
`utilize internal pressure operated circulating valves that
`operated in response to pressure in the test string. It has been
`found, however, that internal pressure operated circulation
`valves may be inadvertently opened as the result of an
`increase in the pressure within the test string. For example,
`when the test string is made up and lowered into the
`wellbore, it is desirable to periodically pressure test the test
`string to assure that the pipe joints have been adequately
`made up. Such testing requires closing of a valve in the
`lower part of the test string and applying pump pressure to
`the interior or the test string at the surface of the well. If the
`test string includes an interior pressure operated circulation
`valve,
`it may be inadvertently opened during such a test
`string pressure test.
`internal pressure operated
`It has also been found that
`circulation valves may be inadvertently opened as the result
`of an unexpected increase in pressure from a formation that
`is not properly under control. If an internal pressure operated
`circulation valve is not operated during a testing program
`and is pulled out of the hole in the unoperated position, such
`a pressure upset from the formation could open an internal
`pressure operated circulation valve and allow formation
`fluids to be release at the surface.
`
`Therefore, a need has arisen for an internal pressure
`operated circulation valve that will not inadvertently opened
`as the result of an increase in the pressure within the test
`string during a pressure test of the test string. Aneed has also
`arisen for such an internal pressure operated circulation
`valve that will not inadvertently open as a result of an
`unexpected pressure surge from the formation particularly
`when the internal pressure operated circulating valve is at or
`near the surface.
`
`SUMMARY OF THE INVENTION
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`invention disclosed herein comprises an
`The present
`internal pressure operated circulation valve that will not
`inadvertently open as the result of an increase in the pressure
`within the test string during a surface pressure test of the test
`string. Likewise, the integral pressure operated circulation
`valve of the present inception will not inadvertently opened
`as a result of an uninspected pressure surge from the
`formation.
`
`The internal pressure operated circulation valve of the
`present invention comprises a housing, a safety mandrel and
`an operating mandrel. The safety mandrel
`is slidably
`received within the housing. The safety mandrel operates
`from a first position to a send position relative to the housing
`in response to pressure being applied to the exterior of the
`housing. The operating mandrel is also slidably received
`within the housing. The operating mandrel operates from a
`noncirculating position to the circulation position in
`response to pressure being applied to the interior of the
`housing. The operating mandrel, however, will only operate
`to the circulating position when the safety mandrel has
`operated to the second position. When the operating mandrel
`is in the circulating position, fluid flow through a circulating
`port formed through a wall of the housing is permitted.
`Aportion of the safety mandrel is slidably received within
`the operating mandrel to selectively prevent the operation of
`the operating mandrel. In one embodiment, the safety man-
`drel physically preventing the movement of the operating
`mandrel in the second direction. In another embodiment, the
`safety mandrel prevents the operation of the operating
`mandrel by preventing the pressure applied to the interior of
`the housing from acting on the operating mandrel.
`
`Page 5 of 9
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`US 6,230,231 1 B1
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`3
`The internal pressure operated circulation valve of the
`present invention may include a biasing device, such as a
`coil spring, to urge the safety mandrel to its first position
`such that a predetermined pressure applied to the exterior of
`the housing is required to operate the safety mandrel to its
`second position. The internal pressure operated circulation
`valve of the present invention may also include a frangible
`restraining device, such as one or more sheer pins,
`to
`selectively prevent the movement of the operating mandrel
`such that a predetermined pressure applied to the interior of
`the housing is required to operate the operating mandrel to
`the circulating position.
`In the method of the present invention, an operating
`mandrel disposed within a housing is operated by, disposing
`a safety mandrel in the housing for initially preventing t1e
`operation of the operating mandrel, applying pressure to t1e
`exterior of the housing to operate the safety mandrel
`between a first position and a second position relative to he
`housing and applying pressure to the interior of the housing
`to operate the operating mandrel from a nocirculating posi-
`tion to a circulating position, thereby permitting fluid flow
`through a circulating port formed through a wall in tie
`housing.
`In the method, the safety mandrcl initially prcvcnts t1c
`operation of the operating mandrel by disposing a portion of
`the safety mandrel within the operating mandrel. In 016
`embodiment, this is achieved by physically preventing t1e
`movement of the operating mandrel in the second direction.
`In another embodiment, this is achieved by preventing t1e
`pressure applied to the interior of the housing from acting on
`the operating mandrel.
`The method of the present inventon may require that a
`predetermined pressure he applied to the exterior of he
`housing to operate the safety mandrel to the second position
`by biasing the safety mandrel to the first position with a
`biasing dcvicc. Likewise, the method of the present inven-
`tion may require that a predetermined pressure be applied to
`the interior of the housing to operate the safety mandrel to
`circulating position by frangibly restraining the operating
`mandrel.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`For a more complete understanding of the features and
`advantages of the present invention, references now made to
`the detailed description of the invention along with the
`accompanying figures in which corresponding numerals in
`the different figures refer to corresponding parts and in
`which:
`
`FIG. 1 is a schematic illustration of an offshore oil or gas
`drilling platform operating a test string including an internal
`pressure operate circulating valve of the present invention;
`FIGS. 2A—2C are quarter sectional views of an internal
`pressure operated circulating valve of the present invention
`in its various operating positions; and
`FIGS. 3A—3C are quarter sectional views of an internal
`pressure operated circulating valve of the present invention
`in its various operating positions.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`While the making and using of various embodiments of
`the present invention is discussed in detail below, it should
`be appreciated that the present invention provides many
`applicable inventive concepts which can be embodied in a
`wide variety of specific contexts. The specific embodiment
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`discussed herein are merely illustrative of the specific ways
`to make and use the invention, and do not limit the scope of
`the invention.
`
`Referring to FIG. 1, an offshore drilling and testing
`operation is schematically illustrated and generally desig-
`natcd 10. A scmi-submcrsiblc platform 12 is centered over
`a submerged oil or gas formation 14 located below the sea
`floor 16. A well comprising a wellbore 18 is lined with a
`casing string 20 extending from the platform 12 to formation
`14. Casing string 20 includes a plurality of perforations 22
`at
`its lower end which provide communication between
`formation 14 and the interior of the wellbore 18.
`
`A wellhead installation 24 which includes blowout pre-
`ventors 26 is located on sea floor 16. Aconductor 28 extends
`
`from wcllhcad installation 24 to platform 12. Platform 12
`includes a work deck 30 that supports a derrick 32. Derrick
`32 supports a hoisting apparatus 34 for raising and lowering
`pipe strings such as formation testing string 36. A supply
`conduit 38 is provided that extends from a hydraulic pump
`40 on deck 30 of platform 12 and extends to the wellhead
`installation 24 at a point below blowout preventors 26 to
`allow the pressurizing of the well annulus 42 surrounding
`test string 36.
`During testing, a seal assembly 44 is used to isolate
`formation 14 from fluids in well annulus 42. Aperforated tail
`piece 46 is provided at the lower end of test string 36 to
`allow fluid communication between formation 14 and the
`
`interior of test string 36. The lower portion of test string 36
`also includes intermediate conduit portion 48 and torque
`transmitting pressure and volume balanced slip joint 50. An
`intermediate conduit portion 52 is provided for imparting
`setting weight to seal assembly 44. Near the lower end of test
`string 36 is located a tester valve 54 which may typically be
`an annulus pressure operated tester valve. Apressure record-
`ing device 56 is located below tester valve 54. Immediately
`above tester valve 54 is an internal pressure operated cir-
`culating valve 58 of the present invention.
`Even though FIG. 1 depicts an offshore environment, it
`should be understood by one skilled in the art
`that the
`downhole component described herein is equally well-suited
`for operation in an onshore environment.
`Referring now to FIGS. 2A—2C therein is depicted quarter
`sectional views of one embodiment of an internal pressure
`operated circulating valve of the present invention that is
`generally designated 100. Valve 100 includes a cylindrical
`outer housing 102 having an upper housing adapter 104
`which includes threads 106 for attaching valve 100 to the
`portion of test string 36 located above valve 100. At the
`lower end of housing 102 is a lower housing adapter 108
`which includes an external threaded portion 110 for con-
`nection of valve 100 to that portion of test string 36 located
`below valve 100.
`
`Slidably and sealably received within inner bore 112 of
`housing 102 is operating mandrel 114. Operating mandrel
`114 is initially frangibly retained in its noncirculating posi-
`tion by one or more shearable members such as a shear pin
`116 which is disposed through a radial bore 118 of housing
`102 and received within a radially extending bore 120 of
`operating mandrel 114. The exact number and size of the
`shearable members will be determined based upon the
`desired operating pressure for operating mandrel 114.
`In the noncirculating position as depicted in FIG. 2A,
`opcrating mandrcl 114 prevents the flow of fluids between
`the exterior of valve 100 and the interior of valve 100
`through circulating port 122. Operating mandrel 114
`includes a plurality of spring fingers, one of which is finger
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`Page 6 of 9
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`US 6,230,231 1 B1
`
`5
`124. Spring finger 124 is terminated by head 126. In the
`noncirculating position, head 126 rests against the upper
`shoulder of annular ledge 128 of housing 102.
`Slidably and sealably received within inner bore 112 of
`housing 102 below operating mandrel 114 is safety mandrel
`134. Safety mandrel 130 includes an upper end 132 that is
`closely received within head 126 of operating mandrel 114
`to physically prevent the movement of operating mandrel
`114.
`
`Acoil compression spring 134 has its upper end engaging
`the lower shoulder of annular ledge 128 and has its lower
`end engaging annular upper end surface 136 of safety
`mandrel 130. Spring 134 biases safety mandrel 130 down-
`wardly to maintain upper end 132 against head 126 and
`prevent movement of operating mandrel 114. In this position
`of valve 100, internal pressure testing of testing string 36
`may periodically occur without moving operating mandrel
`114 or loading shearable members 116.
`Spring 134 is initially retained in a substantially uncom-
`pressed state until external pressure applied to safety man-
`drel 130 through communication port 142 of housing 102
`acts between seals 138 and 140. When the external hydro-
`static pressure reaches a sufficient level, safety mandrel 130
`travels upwardly relative to housing 102 compressing spring
`134, as best seen in FIG. 2B. A rupture disk 143 may be
`placed within communication part 142 to selectively prevent
`the external hydrostatic pressure from communicating with
`safety mandrel 130 until the external hydrostatic pressure
`reaches a suflicient level to burst rupture disk 143. Once
`safety mandrel 130 has traveled upwardly, safety mandrel
`130 no longer physically restrains the movement of operat-
`ing mandrel 114. If the external hydrostatic pressure is
`reduced below the predetermined level, valve 100 is reset
`into the position depicted in FIG. 2A due to the bias force of
`spring 134. The procedure may be repeated without moving
`operating mandrel 114.
`When valve 100 is in the position depicted in FIG. 2B,
`application of internal pressure then acts on operating man-
`drel 114 between seals 144 and 146 thus urging operating
`mandrel 114 downwardly. When sufficient pressure is
`applied, pin 116 shears thus permitting operating mandrel
`114 to move downwardly. As opcrating mandrcl 114 movcs
`downwardly, the spring fingers, such as spring finger 124,
`are no longer restrained by upper end 132 of safety mandrel
`130 and spring inwardly around annular ledge 128 of
`housing 102, as best seen in FIG. 2C.
`It should be apparent to those skilled in the art that the use
`of directional terms such as above, below, upper, lower,
`upward, downward, etc. are used in relation to the illustra-
`tive embodiments as they are depicted in the figures, the
`upward direction being towards the top of the corresponding
`figure and the downward direction being toward the bottom
`of the corresponding figure. It is to be understood that the
`downholc componcnt described herein may be operated in
`vertical, horizontal, inverted or inclined orientation without
`deviating from the principles of the present invention.
`the
`In operation, valve 100 is initially assembled at
`surface as shown in FIG. 2A. Thereafter, valve 100 is
`incorporated into a test string such as that shown in FIG. 1
`and lowered into the wellbore as shown in FIG. 1. When in
`
`this configuration, tester valve 54 of FIG. 1 may be repeat-
`edly opened and closed by application of annulus pressure in
`order to conduct prcssurc tests of test string 36 which may
`shift safety mandrel 130 but will not shift operating mandrel
`114 of valve 100. Thereafter, fluids may be pumped through
`test string 36 and into formation 14, for example, for
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`acid-treating formation 14. After testing and treatment, but
`prior to raising test string 36 out of wellbore 18,
`it
`is
`desirable to reverse circulate fluids from test string 36. Such
`is accomplished by moving the operating mandrel down-
`wardly so that circulation port 122 is in communication with
`the interior of housing 102. Thereafter, fluid is pumped
`downwardly in the annulus through port 122 and upwardly
`through test string 36 thereby reverse circulating fluids from
`test string 36.
`Valve 100 is opened by shifting safety mandrel 130 then
`shifting operating mandrel 114 as follows. With valve 100 in
`the configuration of FIG. 2A and suspended on test string 36
`as shown in FIG. 1, the hydrostatic pressure of the annulus
`fluids upwardly bias safety mandrel 130 via communication
`port 142. Seal 138 defines an outer diameter and seal 140 an
`inner diameter of safety mandrel 130. When the hydrostatic
`force reaches the predetermined level necessary to overcome
`the bias force of spring 134, safety mandrel 130 moves
`upwardly with upper end 132 of safety mandrel 130 no loner
`contacting head 126 of spring finger 124 of operating
`mandrel 114. Alternatively, rupture disk 143 may be placed
`within coinmunication port 142 which may be set to burst at
`a predetermined pressure.
`Aftcr safcty mandrcl 130 has moved to its upper position
`as best seen in FIG. 2B, test string 36 is pressurized thus
`permitting pressurized fluid to act on operating mandrel 114.
`Seal 144 defines an outer diameter and seal 146 defines the
`
`inner diameter of operating mandrel 114. When the pressure
`reaches the predetermined level necessary to shear the shear
`pins 116, operating mandrel 114 moves quickly down-
`wardly. In the lower position of operating mandrel 114, as
`best seen in FIG. 2C, seal 144 is below port 122 and thus
`fluid communication is permitted between the annulus and
`the interior of housing 102 thereby allowing reverse circu-
`lation.
`
`Once operating mandrel 114 has opened circulating port
`122, it remains open. When the formation fluids are circu-
`lated out of test string 36 and fully replaced by the fluids
`from the annulus, test string 36 may be pulled from the
`wellbore.
`
`Thus, it can be seen that prior to the operation of safety
`mandrcl 130, for example during a surface tcst string pres-
`sure test, there is no risk of inadvertently opening circulation
`port 122 since interior pressure will not operate operating
`mandrel 114. Before pressure in test string 36 can be so
`communicated, safety mandrel 130 must be urged upwardly
`until upper end 132 no longer interferes with the movement
`of operating mandrel 114. It should be noted that if interior
`pressure is not applied to operating mandrel 114 while safety
`mandrel 130 is in the uppermost position, spring 134 will
`return safety mandrel 130 to the position seen in FIG. 2A
`when the bias force of spring 134 becomes greater than the
`hydrostatic force acting upwardly on safety mandrel 130.
`Referring now to FIGS. 3A—3C therein is depicted quartcr
`sectional views of another embodiment of an internal pres-
`sure operated circulating valve of the present invention that
`is generally designated 200. Valve 200 includes a cylindrical
`outer housing 202 having an upper housing adapter 204
`which includes threads 206 for attaching valve 200 to the
`portion of test string 36 located above valve 200. At the
`lower end of housing 202 is a lower housing adapter 208
`which includes an external threaded portion 210 for con-
`nection of valve 200 to that portion of test string 36 located
`below Valve 200.
`
`Slidably and sealably received within inner bore 212 of
`housing 202 is operating mandrel 214. Operating mandrel
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`US 6,230,231 1 B1
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`7
`214 is initially frangibly retained in its noncirculating posi-
`tion by one or more shearable members such as shear pin
`216 which is disposed through a radial bore 218 of housing
`202 and received within a radially extending bore 220 of
`operating mandrel 214. In the noncirculating position as
`depicted in FIG. 3A, operating mandrel 214 prevents the
`flow of fluids between the exterior of valve 200 and the
`interior of valve 200 through circulating port 222. Operating
`mandrel 214 includes a communication port 225.
`Slidably and sealably received within inner bore 212 of
`housing 202 above operating mandrel 214 is safety mandrel
`230. Safety mandrel 230 includes a lower end 232 that is
`closely received within operating mandrel 214 to prevent
`internal pressure from entering communication port 225
`thereby preventing the movement of operating mandrel 214.
`Acoil compression spring 234 has its upper end engaging
`the lower shoulder 237 of housing 202 and has its lower end
`engaging annular upper end surface 236 of safety mandrel
`230. Spring 234 biases safety mandrel 230 downwardly to
`maintain lower end 232 within operating mandrel 214 and
`prevent movement of operating mandrel 214. In this position
`of valve 200, internal pressure testing of testing string 36
`may periodically occur without moving operating mandrel
`214 or loading shearable member 216.
`Spring 234 is initially retained in a substantially uncom-
`pressed state until external hydrostatic pressure acting
`between seals 238 and 240 through communication port 242
`of housing 202 reaches a predetermined level. When the
`external hydrostatic pressure reaches a suflicient
`level,
`safety mandrel 230 travels upwardly relative to housing 202
`compressing spring 234, as best seen in FIG. 3B. A rupture
`disk 243 may be placed within communication port 242 to
`selectively prevent the external hydrostatic pressure from
`communicating to safety mandrel 230 until the external
`hydrostatic pressure reaches a suflicient level to burst rup-
`ture disk 243. Once safety mandrel 230 has traveled
`upwardly, seal 241 no loner prevents internal pressure from
`entering communication port 225. If the external hydrostatic
`pressure is reduced below the predetermined level, however,
`valve 200 will reset into the position depicted in FIG. 3A due
`to the bias force of spring 234. This procedure may be
`repeated without moving operating mandrel 214.
`When valve 200 is in the position depicted in FIG. 3B,
`application of internal pressure acts on operating mandrel
`214 between seals 244 and 246 thus urging operating
`mandrel 214 downwardly. When sufficient pressure is
`applied, pins 216 shear thus permitting operating mandrel
`214 to move downwardly, as best seen in FIG. 3C.
`the
`In operation, valve 200 is initially assembled at
`surface as shown in FIG. 3A. Thereafter, valve 200 is
`incorporated into test string 36 as shown in FIG. 1 and
`lowered into wellbore 18. After testing and treatment, but
`prior to raising test string 36 out of wellbore 18,
`it is
`desirable to reverse circulate fluids from test string 36 which
`may shift safety mandrel 230 but will not shift operating
`mandrel 114 at valve 200. Such is accomplished by moving
`operating mandrel 214 downwardly so that circulation port
`222 is in communication with the interior of housing 202.
`Thereafter, fluid is pumped downwardly in the annulus
`through port 222 and upwardly through test string 36
`thereby circulating well fluids from test string 36.
`Valve 200 is opened by shifting safety mandrel 230 then
`shifting operating mandrel 214 as follows. With valve 200 in
`the configuration of FIG. 3A and suspended on test string 36
`as shown in FIG. 1, the hydrostatic pressure of the annulus
`fluids upwardly bias safety mandrel 230 via communication
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`port 242. Seal 238 defines an outer diameter and seal 240 an
`inner diameter of safety mandrel 230. When the hydrostatic
`force reaches the predetermined level necessary to overcome
`the bias force of spring 234, safety mandrel 230 moves
`upwardly with lower end 232 and seal 241 of safety mandrel
`230 no longer contacting operating mandrel 214. A rupture
`disk 243 may additionally be placed within communication
`port 242 that is set to burst at a predetermined pressure.
`After safety mandrel 230 has moved to its upper position
`as best seen in FIG. 3B, test string 36 is pressurized thus
`permitting pressurized fluid to travel through communica-
`tion port 225 and act on operating mandrel 214. Seal 244
`defines an outer diameter and seal 246 defines the inner
`diameter of operating mandrel 214. When the pressure
`reaches the predetermined level necessary to shear the shear
`pins 216, operating mandrel 214 moves quickly down-
`wardly.
`In the lower position of operating mandrel 214 as best
`seen in FIG. 3C, seal 244 is below port 222 and thus fluid
`communication is permitted between the annulus and the
`interior of housing 202 thereby allowing reverse circulation.
`Thus,
`it can be seen that prior to operating of safety
`mandrel 230 there is no risk of inadvertently opening
`circulation port 222 since interior pressure will not operate
`operating mandrel 214. Before pressure in test string 36 can
`be so communicated, safety mandrel 230 must be urged
`upwardly until seal 241 is above communication port 225 of
`operating mandrel 214.
`Once operating mandrel 214 has opened circulating port
`222, it remains open. When the formation fluids are circu-
`lated out of test string 36 and fully replaced by the fluids
`from the annulus, test string 36 may be pulled from wellbore
`18.
`While this invention has been described with a reference
`
`to illustrative embodiments, this description is not intended
`to be construed in a limiting sense. Various modifications
`and combinations of the illustrative embodiments as well as
`
`other embodiments of the invention, will be apparent to
`persons skilled in the art upon reference to the description.
`It is therefore, intended that the appended claims encompass
`any such modifications or embodiments.
`What is claimed is:
`
`1. A downhole tool comprising:
`a housing;
`a safety mandrel slidably received within the housing, the
`safety mandrel operating in a first direction between a
`first position and a second position relative to the
`housing in response to pressure being applied to the
`exterior of the housing; and
`an operating mandrel slidably received within the
`housing, the operating mandrel operating in a second
`direction from a first position to a second position
`relative to the housing in response to pressure being
`applied to the interior of the housing when the safety
`mandrel is in the second position of the safety mandrel
`relative to the housing.
`2. The downhole tool as recited in claim 1 wherein a
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`60
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`65
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`portion of the safety mandrel is slidably received within the
`operating mandrel when the safety mandrel is in the first
`position of the safety mandrel it selectively prevent the
`operation of the operating mandrel.
`3. The downhole tool as recited in claim 2 wherein the
`safety mandrel prevents the operation of the operating
`mandrel by physically preventing the movement of the
`operating mandrel in the second direction.
`4. The downhole tool as recited in claim 2 wherein the
`safety mandrel prevents the operation of the operating
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`Page 8 of9
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`US 6,230,231 1 B1
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`10
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`15
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`9
`mandrel by preventing the pressure applied to the interior of
`the housing from acting on the operating mandrel.
`5. The downhole tool as recited in claim 1 further com-
`prising a biasing device urging the safety mandrel in the
`second direction such that a predetermined pressure applied
`to the exterior of the housing is required to operate the safety
`mandrel to the second position.
`6. The downhole tool as recited in claim 1 further com-
`prising a frangible restraining device selectively preventing
`movement of the operating mandrel such that a predeter-
`mined pressure applied to the interior of the housing is
`required to operate the operating mandrel to the second
`position.
`7. The downhole tool as recited in claim 1 wherein the
`operating mandrel permits fluid flow through a circulating
`port formed through a wall in the housing when the oper-
`ating mandrel operates to the second position.
`8. A circulating valve comprising:
`a housing having a circulating port formed therethrough;
`a safety mandrel slidably received within the housing, the
`safety mandrel reversibly moveable from a first posi-
`tion to a second position in response to a predetermined
`level of external pressure being applied to the exterior
`of the housing and reversibly moveable from the sec-
`ond position to the first position when the pressure
`being applied to the exterior of the housing is decreased ,
`below the predetermined level; and
`an operating mandrel slidably received within the
`housing, the operating mandrel having a noncirculating
`position wherein fluid flow through the circulating port
`is prevented and a circulating position wherein fluid
`flow through the circulating port
`is permitted,
`the
`operating mandrel operating from the noncirculating
`position to the circulating position in response to a
`predetermined level of internal pressure being applied
`to the interior of the housing while the predetermined
`level of external pressure maintains the safety mandrel
`in the second position.
`9. The circulating valve as recited in claim 8 wherein a
`portion of the safety mandrel is slidably received within the
`operating mandrel when the safety mandrel is in the first
`position of the safety mandrel to selectively prevent the
`movement of the operating mandrel from the noncirculating
`position to the circulating position.
`10. The circulating valve as recited in claim 9 wherein the
`safety mandrel prevents the movement of the operating
`mandrel from the noncirculating position to the circulating
`position by preventing the pressure applied to the interior of
`the housing from acting on the operating mandrel