Patent Publication Number: US-6668936-B2

Title: Hydraulic control system for downhole tools

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit under 35 USC §119 of the filing date of international application PCT/US00/24551, filed Sep. 7, 2000, the disclosure of which is incorporated herein by this reference. 
    
    
     BACKGROUND 
     The present invention relates generally to methods and apparatus utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a hydraulic control system for downhole tools. 
     It would be desirable to be able to operate selected ones of multiple hydraulically actuated well tools installed in a well. However, it is uneconomical and practically unfeasible to run separate hydraulic control lines from the surface to each one of numerous well tool assemblies. Instead, the number of control lines extending relatively long distances should be minimized as much as possible. 
     Therefore, it would be highly advantageous to provide a hydraulic control system which reduces the number of control lines extending relatively long distances between multiple hydraulically actuated well tools and the surface. The hydraulic control system would preferably permit individual ones of the well tools to be selected for actuation as desired. The selection of well tools for actuation thereof should be convenient and reliable. 
     Furthermore, it would be desirable to provide methods of controlling operation of multiple well tools, and it would be desirable to provide well tools which may be operated utilizing such a hydraulic control system. 
     SUMMARY 
     In carrying out the principles of the present invention, in accordance with an embodiment thereof, a hydraulic control system is provided which reduces the number of control lines extending relatively long distances to multiple well tool assemblies. Well tool assemblies and methods of controlling operation of multiple well tool assemblies are also provided. 
     In one aspect of the present invention, a control module is interconnected between a flowpath extending to a remote location, such as the surface, and flowpaths extending to multiple well tool assemblies. The control module provides fluid communication between the flowpath extending to the remote location and selected ones of the flowpaths extending to the well tool assemblies, so that corresponding selected ones of the well tool assemblies may be operated by pressure in the flowpath extending to the remote location. 
     In another aspect of the present invention, the control module is operated to select from among the flowpaths extending to the well tool assemblies by pressure in another flowpath connected to the control module. Yet another flowpath may be connected to the control module to provide a pressure differential used to operate the control module. 
     Various methods may be used to cause the control module to select from among the flowpaths extending to the well tool assemblies. In one disclosed embodiment, a ratchet device or J-slot mechanism is used to control displacement of a member of the control module. In another disclosed embodiment, a member of the control module is displaced against a force exerted by a biasing device, such as a spring or a compressed fluid. 
     In yet another aspect of the present invention, various well tool assemblies are provided, which may be operated by the disclosed hydraulic control systems. A variable flow area sliding sleeve-type valve is disclosed. The valve is operated by applying a series of pressures to an actuator thereof to incrementally displace a sleeve of the valve. As the sleeve displaces, the available area for fluid flow through the valve is increased or decreased. 
     Other well tool assemblies provided are a temperature sensor and a pressure sensor. Each of the sensors is operated by pressure in a flowpath thereof displacing a piston to a position in which the flowpath is placed in fluid communication with another flowpath. In the temperature sensor, the position of the piston corresponds to a known volume of a chamber in which a fluid exposed to the temperature is disposed. In the pressure sensor, the position of the piston corresponds to a known pressure differential between the flowpath and another flowpath exposed to the piston. 
     These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a method embodying principles of the present invention; 
     FIGS. 2A-C are cross-sectional views of successive axial portions of a hydraulic control module usable in the method of FIG.  1  and embodying principles of the present invention; 
     FIG. 3 is a developed view of a J-slot portion of the hydraulic control module; 
     FIG. 4 is an end view of the hydraulic control module; 
     FIGS. 5A-5C are cross-sectional views of successive axial portions of the hydraulic control module in a configuration in which a hydraulic path has been selected for operation of a well tool; 
     FIG. 6 is a developed view of the J-slot portion of the hydraulic control module in a configuration corresponding to the configuration of the hydraulic control module of FIGS. 5A-C; 
     FIG. 7 is a schematic partially cross-sectional view of an alternate configuration of the method of FIG. 1 in which a selector module is utilized in conjunction with the hydraulic control module; 
     FIGS. 8A-C are cross-sectional views of successive axial portions of a well tool assembly embodying principles of the present invention, which may be utilized in the method of FIG. 1, and the operation of which may be controlled by the hydraulic control module of FIGS. 2A-C; 
     FIG. 9 is a schematic cross-sectional view of another hydraulic control module embodying principles of the present invention, which may be utilized in the method of FIG. 1; 
     FIG. 10 is a cross-sectional view of the hydraulic control module of FIG. 9, taken along line  10 — 10  thereof; and 
     FIG. 11 is a schematic cross-sectional view of another well tool assembly embodying principles of the present invention, which may be utilized in the method of FIG. 1, and the operation of which may be controlled by the hydraulic control module of FIG.  9 . 
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in FIG. 1 is a method  10  which embodies principles of the present invention. In the following description of the method  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used only for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. 
     In the method  10 , multiple well tool assemblies  12 ,  14 ,  16 ,  18  are interconnected in a tubular string  20  positioned in a wellbore  22 . As depicted in FIG. 1, each of the tool assemblies  12 ,  14 ,  16 ,  18  is hydraulically operated and is configured for controlling fluid flow between the wellbore  22  and one of multiple formations or zones  24 ,  26 ,  28 ,  30  intersected by the wellbore. The tool assemblies  12 ,  14 ,  16 ,  18  may be, for example, valves, chokes, or some other type of flow control devices. 
     Four of the tool assemblies  12 ,  14 ,  16 ,  18  are shown in FIG. 1 for controlling fluid flow for four corresponding zones  24 ,  26 ,  28 ,  30 . However, it is to be clearly understood that any number of well tool assemblies may be utilized in a wellbore intersecting any number of zones, and well tool assemblies other than flow control devices may be utilized, without departing from the principles of the present invention. Thus, the method  10  is merely illustrative of one example of an application of the principles of the present invention. 
     Operation of selected ones of the tool assemblies  12 ,  14 ,  16 ,  18  is controlled by a hydraulic control module  32  interconnected in the tubular string  20 . One or more control lines  34 , or other type of flowpaths, extend to a remote location, such as the earth&#39;s surface, or to a remote location within the wellbore  22 , etc. The control module  32  places one or more of the control lines  34  in fluid communication with one or more lines  36 , or other types of flowpaths, extending to the tool assemblies  12 ,  14 ,  16 ,  18  when it is desired to operate selected ones of the tool assemblies, for example, to open or close one or more of the tool assemblies. 
     The control module  32  is interconnected between the lines  34  and the lines  36  and operates in response to pressure in one or more of the lines  34 . For example, pressure in one of the lines  34  may be increased to thereby provide fluid communication between another one of the lines  34  and one or more of the lines  36  to thereby operate one or more of the tool assemblies  12 ,  14 ,  16 ,  18 . As another example, a pressure differential between two of the lines  34  may be used to cause the control module  32  to provide fluid communication between another one of the lines  34  and one or more of the lines  36 . As yet another example, a series of pressure differentials may be applied to the lines  34  to select certain one or more of the lines  36  for fluid communication with certain one or more of the lines  34 , etc. Thus, it may be clearly seen that the method  10  permits the tool assemblies  12 ,  14 ,  16 ,  18  to be selected for operation thereof, and subsequently operated, by merely generating appropriate pressures on certain ones of the lines  34 . 
     Referring additionally now to FIGS. 2A-C, a hydraulic control module  38  embodying principles of the present invention is representatively illustrated. The control module  38  may be utilized for the control module  32  in the method  10 , or the control module  38  may be used in other methods, without departing from the principles of the present invention. The control module  38  is configured for interconnection in a tubular string, such as the tubular string  20  of the method  10 , in which case an internal flow passage  40  of the control module would be a part of the internal flow passage of the tubular string, but it is to be clearly understood that the control module may be differently configured, for example, as an integral portion of an actuator or other well tool, without departing from the principles of the present invention. 
     As depicted in FIGS. 2A-C, the control module  38  includes an outer housing assembly  42 , an inner sleeve member  44  and a ratchet device  46 . The sleeve  44  is axially reciprocably disposed within the housing  42 . Displacement of the sleeve  44  relative to the housing  42  is controlled in part by the ratchet device  46  in a manner described in further detail below. 
     The sleeve  44  has piston areas formed externally on opposite sides of a seal  48 . A flowpath  50  is in fluid communication with the sleeve piston area below the seal  48 , and a flowpath  52  is in fluid communication with the sleeve piston area above the seal. It will be readily appreciated by one skilled in the art that, if pressure in the flowpath  50  exceeds pressure in the flowpath  52 , the sleeve  44  will be biased upwardly by the pressure differential, and if pressure in the flowpath  52  exceeds pressure in the flowpath  50 , the sleeve  44  will be biased downwardly by the pressure differential. 
     As representatively illustrated in FIGS. 2A-C, the sleeve piston areas above and below the seal  48  are approximately equal, and so the sleeve  44  is displaced with equal force in either direction in response to equal differentials between pressure in the flowpath  50  and pressure in the flowpath  52 . However, the manner of displacing the sleeve  44  and its response to differentials between pressure in the flowpath  50  and pressure in the flowpath  52  may be readily changed by, for example, providing unequal piston areas, providing biasing devices, such as springs or compressed fluids, etc., as desired to produce certain forces on, or displacements of, the sleeve. These techniques are well known to those skilled in the art, and will not be described further herein. 
     Furthermore, it is to be clearly understood that it is not necessary for the sleeve  44  to be displaced by use of a pressure differential between flowpaths, or for the sleeve to be displaced by use of a pressure differential at all. For example, pressure in the flowpath  50  may be used to displace the sleeve  44  against a force exerted by a biasing device. Thus, the sleeve  44  may be displaced in any manner, without departing from the principles of the present invention. 
     The sleeve  44  has a fluid passage  54  formed internally in a sidewall thereof. The fluid passage  54  communicates with the exterior of the sleeve  44  via two openings  56 ,  58 . The fluid passage  54  remains in fluid communication with another flowpath  60  formed in the housing  42  via the opening  56  as the sleeve  44  displaces relative to the housing. However, the other opening  58  is placed in fluid communication with one of the flowpath  60  or additional flowpaths  62 ,  64 ,  66 ,  68  formed in the housing  42 , depending upon the position of the sleeve  44  relative to the housing. 
     Of the flowpaths  62 ,  64 ,  66 ,  68 , only the flowpath  68  is completely visible in FIG.  2 C. Portions of the flowpaths  62 ,  64 ,  66  are shown in FIGS. 2B &amp; C, so that it may be seen how the flowpaths  62 ,  64 ,  66 ,  68  are arranged in relation to seals  70  and the opening  58  of the sleeve  44 . A lower end view of the control module  38  is shown in FIG. 4, in which it may be seen that the flowpaths  62 ,  64 ,  66 ,  68  are actually circumferentially distributed in the housing  42 . 
     As depicted in FIGS. 2A-C, the fluid passage  54  is in fluid communication with only the flowpath  60  via the openings  56 ,  58 . If, however, the sleeve  44  is displaced downwardly somewhat, so that the opening  58  is between the two seals  70  straddling the flowpath  62 , the fluid passage  54  will be placed in fluid communication with the flowpath  62 , and will thereby provide fluid communication between the flowpaths  60  and  62 . In a similar manner, the opening  58  may be positioned between the seals  70  straddling each one of the other flowpaths  64 ,  66 ,  68  to thereby provide fluid communication between that flowpath and the flowpath  60 . Thus, by appropriately positioning the sleeve  44  relative to the housing  42 , any of the flowpaths  62 ,  64 ,  66 ,  68  may be placed in fluid communication with the flowpath  60 . 
     The sleeve  44  is displaced relative to the housing  42  by pressure differentials between the flowpaths  50 ,  52  as described above. The ratchet device  46 , however, controls the position relative to the housing  42  to which the sleeve  44  is displaced when the pressure differentials are generated in the flowpaths  50 ,  52 . In the embodiment representatively illustrated in FIGS. 2A-C, a certain number of pressure differential reversals between the flowpaths  50 ,  52  is used to alternately upwardly and downwardly displace the sleeve  44  a desired number of times, so that the sleeve is finally placed in a position in which a desired one of the flowpaths  62 ,  64 ,  66 ,  68  is in fluid communication with the flowpath  60 . 
     The ratchet device  46  is of the type well known to those skilled in the art as a J-slot mechanism. The ratchet device  46  includes a pair of balls  72 , a ball retainer  74  and continuous J-slot profiles  76  formed externally on the sleeve  44 . The ball retainer  74  secures the balls  72  in 180° opposed positions relative to the housing  42 . As the sleeve  44  displaces relative to the housing  42  due to a pressure differential in the flowpaths  50 ,  52 , the balls  72  traverse the J-slot paths  76 , thus limiting the extent of the sleeve&#39;s displacement in a manner well known to those skilled in the art. 
     A portion of the exterior of the sleeve  44  is shown “unrolled” in FIG.  3  and rotated 90°. In this view only one of the paths  76  may be completely seen, but it may also be seen that the paths are interconnected, so that, in effect, the path is duplicated each 180° about the sleeve  44 . 
     One of the balls  72  is also visible in FIG.  3 . The ball  72  is positioned in one of four lower portions  78  of the path  76 . Note that, when the ball  72  is positioned in one of the lower portions  78 , the sleeve  44  is positioned relative to the housing  42  as depicted in FIGS. 2A-C, and none of the flowpaths  62 ,  64 ,  66 ,  68  is in fluid communication with the flowpath  60 . This position of the sleeve  44  is obtained by displacing the sleeve  44  upwardly relative to the housing  42  by generating a pressure in the flowpath  50  greater than a pressure in the flowpath  52 . 
     Each of upper portions  80 ,  82 ,  84 ,  86  of the path  76  corresponds to a position of the sleeve  44  relative to the housing  42  in which a respective one of the flowpaths  62 ,  64 ,  66 ,  68  is placed in fluid communication with the flowpath  60 . Thus, if the ball  72  is in the portion  80  of the path  76 , the flowpath  62  is placed in fluid communication with the flowpath  60 . If the ball  72  is in the portion  82  of the path  76 , the flowpath  64  is placed in fluid communication with the flowpath  60 . If the ball  72  is in the portion  84  of the path  76 , the flowpath  66  is placed in fluid communication with the flowpath  60 . If the ball  72  is in the portion  86  of the path  76 , the flowpath  68  is placed in fluid communication with the flowpath  60 . 
     The ball  72  is received in one of the portions  80 ,  82 ,  84 ,  86  by downwardly displacing the sleeve  44  relative to the housing  42 . As described above, the sleeve  44  is downwardly displaced relative to the housing  42  by generating a pressure in the flowpath  52  greater than a pressure in the flowpath  50 . The extent to which the sleeve  44  displaces downwardly is limited by the particular portion  80 ,  82 ,  84 ,  86  of the path  76  in which the ball  72  is received when the sleeve displaces downwardly. The particular portion  80 ,  82 ,  84 ,  86  in which the ball  72  is received depends upon which of the lower portions  78  of the path  76  the ball is received in prior to the downward displacement of the sleeve. 
     The ball  72  circulates about the path  76 , and is successively received in alternating ones of the upper portions  80 ,  82 ,  84 ,  86  and lower portions  78  as the pressure differentials between the flowpaths  50 ,  52  continue to be reversed. Therefore, it will be readily appreciated by one skilled in the art that any one of the flowpaths  62 ,  64 ,  66 ,  68  may be placed in fluid communication with the flowpath  60  by applying a certain number of pressure differential reversals to the flowpaths  50 ,  52 , the last pressure differential downwardly displacing the sleeve  44  so that the ball  72  is received in a respective one of the portions  80 ,  82 ,  84 ,  86 . Fluid communication between the flowpath  60  and all of the flowpaths  62 ,  64 ,  66 ,  68  may be prevented by upwardly displacing the sleeve, so that the ball  72  is received in any one of the portions  78  of the path  76 . 
     Referring additionally now to FIGS. 5A-C, the control module  38  is depicted in a configuration in which the sleeve  44  has been displaced downwardly relative to the housing  42  to a position in which the flowpath  60  has been placed in fluid communication with the flowpath  68 . In FIG. 6, it may be seen that the ball  72  is now received in the upper portion  86  of the path  76 , corresponding to the selection of the flowpath  68  for fluid communication with the flowpath  60 . 
     Of course, other methods of placing the flowpath  60  in fluid communication with the flowpaths  62 ,  64 ,  66 ,  68  may be utilized, without departing from the principles of the present invention. In addition, more than one of the flowpaths  62 ,  64 ,  66 ,  68  could be simultaneously placed in fluid communication with the flowpath  60 , or multiple flowpaths could be placed in fluid communication with respective ones of other multiple flowpaths. More or less numbers of flowpaths could be provided. Other means of positioning the sleeve  44  relative to the housing  42  could be provided. Thus, it is to be clearly understood that the principles of the present invention are not limited to the specific embodiment depicted in FIGS. 2A-C. 
     If the control module  38  is used for the control module  32  in the method  10 , then the flowpaths  50 ,  52 ,  60  would be connected to respective ones of the lines  34 , and the flowpaths  62 ,  64 ,  66 ,  68  would be connected to respective ones of the lines  36 . Manipulation of pressure differentials on the ones of the lines  34  connected to the flowpaths  50 ,  52  would cause the one of the lines  34  connected to the flowpath  60  to be placed in fluid communication with a particular one of the lines  36  connected to a respective one of the flowpaths  62 ,  64 ,  66 ,  68  to thereby permit operation of a selected one of the well tool assemblies  12 ,  14 ,  16 ,  18  to which that particular one of the lines  36  is connected. Of course, different numbers of well tool assemblies, and different types of well tool assemblies, may be controlled with the control module  38 , or a differently configured control module, without departing from the principles of the present invention. 
     Referring additionally now to FIG. 7, an alternate embodiment of the method  10  embodying principles of the present invention is representatively illustrated. Only a portion of the well schematically shown in FIG. 1 is shown in FIG.  7 . Specifically, only a portion of the tubular string  20  in the wellbore  22  is illustrated in FIG.  7 . 
     In the method  10  as depicted in FIG. 7, the control module  38  of FIGS. 2A-C is used for the control module  32  and, in addition, a selector module  88  is interconnected between the control module  38  and one of the lines  34 . As depicted in FIG. 7, a line or other flowpath  90  extending to a remote location is connected to the selector module  88  and two lines or other flowpaths  92 ,  94  extend from the selector module to the control module  38 . 
     The selector module  88  is of the type well known to those skilled in the art which provides fluid communication between an input port and one of multiple output ports. Which one of the multiple output ports is placed in fluid communication with the input port depends upon the pressure at the input port. For the selector module  88 , the line  90  is placed in fluid communication with the line  92  when pressure in the line  90  is less than a predetermined pressure, and the line  90  is placed in fluid communication with the line  94  when pressure in the line is greater than a predetermined pressure. A suitable selector module for use as the selector module  88  in the method  10  as depicted in FIG. 7 is the Mini-Hydraulic Module available from Petroleum Engineering Services, Inc. of Spring, Tex., U.S.A. 
     By varying pressure in the line  90  connected to the selector module  88 , fluid communication may be established between the line  90  and a selected one of the lines  92 ,  94 . The other one of the lines  92 ,  94  is vented to the internal flow passage of the tubular string  20 . Thus, with the lines  92 ,  94  connected to respective ones of the flowpaths  50 ,  52  of the control module  38 , pressure differentials in the flowpaths  50 ,  52  may be reversed as desired to provide fluid communication between another line or other flowpath  96  connected to the flowpath  60  of the control module and a selected one of lines or other flowpaths  98  connected to respective ones of the flowpaths  62 ,  64 ,  66 ,  68  of the control module. 
     Referring additionally now to FIGS. 8A-C, a well tool assembly  100  embodying principles of the present invention is representatively illustrated. The tool assembly  100  may be utilized for any of the tool assemblies  12 ,  14 ,  16 ,  18  in the method  10 . Of course, the tool assembly  100  may also be used in other methods, without departing from the principles of the present invention. 
     The tool assembly  100  includes an actuator  102 , a housing assembly  104  and a closure sleeve  106 . In basic terms, the actuator  102  displaces the sleeve  106  relative to the housing  104  to thereby regulate fluid flow through a series of openings  108  formed through a sidewall of the housing. As depicted in FIGS. 8A-C, the sleeve  106  is displaced downwardly relative to the housing  104  to block fluid flow through successive ones of the openings  108  by engaging a seal  112  carried on the sleeve with successive ones of a series of seal surfaces  110  formed internally on the housing  104  between the openings. 
     The actuator  102  displaces the sleeve  106  downwardly in an incremental fashion in response to an application of pressure to an input port or other flowpath  114 . Each application of appropriate pressure to the port  114  produces a corresponding incremental downward displacement of the sleeve  106 . 
     When pressure is applied to the port  114 , an annular piston  116  of the actuator  102  is displaced downward into contact with a colletted annular slip member  118 . Continued downward displacement of the piston  116  and slip  118  compresses a spring stack or other biasing device  120 . Thus, for the slip  118  to be displaced downwardly by the piston  116 , the pressure applied to the port  114  must be sufficiently great to cause compression of the spring stack  120 . 
     Contact between cooperatively shaped inclined surfaces  122 ,  124  formed on the piston  116  and slip  118 , respectively, cause the slip to grip the sleeve  106 . Thus, when the slip  118  is displaced downwardly by the piston  116 , the sleeve  106  is displaced downwardly with the slip. Downward displacement of the piston  116  is limited by an internal shoulder  126  of the actuator  102 , and so the downward displacement of the sleeve  106  in response to each application of pressure to the port  114  is limited to the distance which may be traversed by the piston until it contacts the shoulder. 
     Of course, the sleeve  106  may be displaced incrementally downward a desired total distance by alternately applying pressure to the port  114  and releasing the pressure from the port a sufficient number of times. The spring stack  120  will displace the piston  116  and slip  118  upward when the pressure at the port  114  is relieved, so that they are again in position to displace the sleeve  106  downwardly when the next application of pressure is made to the port  114 . 
     By displacing the sleeve  106  downwardly a desired distance from its position as depicted in FIGS. 8A-C, it will be readily appreciated that a selected number of the openings  108  may be blocked to fluid flow therethrough. In this manner, a flow area through the housing  104  sidewall maybe adjusted as desired, for example to regulate a rate of production from a zone, to regulate a rate of fluid injection into a zone, etc. 
     After the sleeve  106  has been displaced downwardly as described above, it may be upwardly displaced back to its position as shown in FIGS. 8A-C by applying pressure to another input port  128 . Since the slip  118  does not grip the sleeve  106  unless pressure is applied to the port  114 , the sleeve is free to displace upwardly when pressure is applied to the other port  128 . Pressure at the port  128  causes upward displacement of the sleeve  106  due to a piston area formed on the sleeve below a seal  130  carried on the sleeve. In this manner, the sleeve  106  may be “reset” to its position in which all of the openings  108  are open to flow therethrough, and then, if desired, the sleeve may again be incrementally displaced downwardly by applying a series of pressures to the port  114 . 
     If the tool assembly  100  is used in the method  10  as depicted in FIG. 1, then the port  114  would be connected to one of the lines  36  and the port  128  would be connected to another one of the lines  36 . For example, if the control module  38  is used for the control module  32  in the method  10 , then one of the flowpaths  62 ,  64 ,  66 ,  68  would be connected to the port  114  and another one of the flowpaths  62 ,  64 ,  66 ,  68  would be connected to the port  128 , so that pressure applied to the flowpath  60  could be used to either incrementally displace the sleeve  106  downwardly, or to displace the sleeve upwardly, as desired. 
     Referring additionally now to FIG. 9, another hydraulic control module  132  embodying principles of the present invention is schematically and representatively illustrated. The control module  132  may be used for the control module  32  in the method  10 , or it may be used in other methods, without departing from the principles of the present invention. 
     The control module  132  includes a housing assembly  134 , an annular piston member  136  and a biasing device or spring  138 . The piston  136  is displaced downwardly relative to the housing  134  against a biasing force exerted by the spring  138  to thereby place openings  140  formed radially through the piston in fluid communication with a selected one of four flowpaths  142 ,  144 ,  146 ,  148  formed in the housing. Of course, a greater or lesser number of flowpaths may be provided, without departing from the principles of the present invention. 
     Only two of the flowpaths  142 ,  146  are visible in FIG.  9 . However, in FIG. 10 it may be seen that the flowpaths  142 ,  144 ,  146 ,  148  are circumferentially distributed in the housing  134 . Each of the flowpaths  142 ,  144 ,  146 ,  148  is in fluid communication with the exterior of the piston  136 , but seals  150  straddling each of the flowpaths ensure that only one of the flowpaths may be placed in fluid communication with the openings  140  at a time. Of course, multiple flowpaths could be simultaneously placed in fluid communication with the openings  140 , if desired. 
     As depicted in FIG. 9, with the piston  136  in its uppermost position relative to the housing  134 , the openings  140  are in fluid communication with the flowpath  142 . In this position of the piston  136 , the openings  140  permit fluid communication between the flowpath  142  and another flowpath  152  formed in the housing  134 . The flowpath  152  is in fluid communication with the openings  140  via a recess  154  internally formed on the piston  136 . 
     The flowpath  152  remains in fluid communication with the opening  140  via the recess  154  when the piston  136  is displaced downwardly relative to the housing  134 . Thus, each of the flowpaths  142 ,  144 ,  146 ,  148  may be selectively placed in fluid communication with the flowpath  152  by displacing the piston  136  to a particular position relative to the housing  134 . 
     The piston  136  is displaced downwardly relative to the housing  134  by applying pressure to another flowpath  156  formed in the housing. Pressure in the flowpath  156  biases the piston  136  downward against the upwardly biasing force of the spring  138  and an upwardly biasing force on the piston due to pressure external to the housing  134 , communicated to the piston via an opening  158  formed through a sidewall of the housing. As is well known to those skilled in the art, the biasing force exerted by the spring  138  will increase as the piston  136  is displaced downwardly. Therefore, by applying a certain pressure to the flowpath  156 , a known downward displacement of the piston  136  may be achieved, corresponding to a known upwardly biasing force exerted by the spring  138  and by the known pressure external to the housing  134 . 
     It is to be clearly understood that other types of biasing devices may be used in the control module  132  in place of the spring  138 . For example, a compressed fluid, such as Nitrogen, could be used to exert an upwardly biasing force on the piston  136 . Thus, the principles of the present invention are not limited to the specific embodiment of the control module  132  described herein. 
     If the control module  132  is used for the control module  32  in the method  10 , one of the lines  34  would be connected to the flowpath  152  and another one of the lines  34  would be connected to the flowpath  156 . The flowpaths  142 ,  144 ,  146 ,  148  would be connected to respective ones of the lines  36 . In this manner, a predetermined pressure applied to one of the lines  34  connected to the flowpath  156  would cause the other one of the lines  34  connected to the flowpath  152  to be placed in fluid communication with a selected one of the lines  36  connected to a corresponding one of the flowpaths  142 ,  144 ,  146 ,  148  for operation of one of the well tools  12 ,  14 ,  16 ,  18  connected thereto. 
     Referring additionally now to FIG. 11, a well tool assembly  160  embodying principles of the present invention is schematically and representatively illustrated. The tool assembly  160  is of a type the operation of which may be controlled utilizing either of the control modules  38 ,  132  described herein. Specifically, the tool assembly  160  includes a housing assembly  166  containing a hydraulically actuated temperature sensor  162  and a hydraulically actuated pressure sensor  164 . 
     The temperature sensor  162  includes a piston  168  and a chamber  170 . The chamber  170  contains a gas, such as Nitrogen, or another fluid which responds rheologically to changes in temperature. The fluid in the chamber  170  is exposed to the temperature in a well when the tool assembly  160  is interconnected in a tubular string, such as the tubular string  20  in the method  10 , or is otherwise positioned in the well. 
     When the fluid is introduced into the chamber  170  before the tool assembly  160  is positioned in the well, the temperature, pressure and volume of the fluid are known. When the fluid is subsequently exposed to the temperature in the well, its pressure will typically increase, due to the typically higher temperatures experienced in downhole environments. This change in pressure due to change in temperature for a given fluid is also known. In addition, if the volume of the fluid is changed while the fluid is exposed to the well temperature, it is also known that a certain change in pressure of the fluid will result. 
     The temperature sensor  162  further includes flowpaths  172  and  174  formed in the housing  166 . The piston  168  initially prevents fluid communication between the flowpaths  172 ,  174 . However, after the tool assembly  160  is positioned in the well and the fluid in the chamber  170  has been exposed to the well temperature, pressure is applied to the flowpath  172  and the pressure is gradually increased. Eventually, the downwardly biasing force due to the pressure in the flowpath  172  will overcome the upwardly biasing force due to the pressure of the fluid in the chamber  170  and the piston  168  will displace downward a sufficient distance, so that fluid communication is permitted between the flowpaths  172 ,  174 . 
     As depicted in FIG. 11, the flowpath  174  is in fluid communication with the interior of the housing  166 . When the piston  168  is displaced downwardly and permits fluid communication between the flowpaths  172 ,  174 , the pressure in the flowpath  172  will suddenly decrease, due to the pressure in the flowpath  172  being vented to the interior of the housing  166 . This sudden decrease in the pressure in the flowpath  172  gives an indication that the piston  168  has displaced downward to a known position (that position which permits fluid communication between the flowpaths  172 ,  174 ) at which point the volume of the chamber  170  is also known. 
     Therefore, the pressure in the flowpath  172  which results in the piston  168  being displaced to produce a known volume of the chamber will correspond to a particular temperature of the fluid in the chamber  170 . By recording the maximum pressure in the flowpath  172  which may be achieved, and which causes the piston  168  to permit fluid communication between the flowpaths  172 ,  174 , a person skilled in the art may readily determine the corresponding temperature of the fluid in the chamber  170 . 
     As depicted in FIG. 11, areas of the piston  168  exposed to pressure in the flowpath  172  and in the chamber  170  are approximately equal, and the piston is balanced with respect to pressure in the flowpath  174 . However, it will be readily appreciated that that the areas of the piston  168  exposed to each of the flowpaths  172 ,  174  and the chamber  170  may be varied as desired to produce different relationships between pressures in the flowpaths and chamber when fluid communication is permitted between the flowpaths. 
     The pressure sensor  164  includes a piston  176  and a biasing device or spring  178 . In its position as depicted in FIG. 11, the piston  176  prevents fluid communication between two flowpaths  180 ,  182  formed in the housing  166 . The spring  178  biases the piston  176  upward toward the position depicted in FIG.  11 . 
     Pressure applied to the flowpath  180  will bias the piston  176  downward against the upwardly biasing force exerted by the spring  178 . Pressure in the flowpath  182  also biases the piston  176  upward. As illustrated in FIG. 11, the flowpath  182  is in fluid communication with the interior of the housing  166 , but it could alternatively be in fluid communication with the exterior of the housing, or it could be in fluid communication with any other region, the pressure of which is to be measured using the pressure sensor  164 . 
     The pressure in the flowpath  180  is gradually increased, and eventually the downwardly biasing force on the piston  176  resulting therefrom overcomes the upwardly biasing forces due to the spring  178  and the pressure in the flowpath  182 . At this point the piston  176  begins to displace downwardly. Further increase in the pressure in the flowpath  180  will cause a seal  184  carried on the piston  176  to enter a recess  186  internally formed on the housing  166 , thereby permitting fluid communication between the flowpaths  180 ,  182 . 
     The point at which fluid communication between the flowpaths  180 ,  182  is permitted will be indicated by a drop in the pressure in the flowpath  180 , if the pressure in the flowpath  182  is less than the pressure in the flowpath  180 , thereby venting the pressure in the flowpath  180 . The spring rate of the spring  178 , the initial compression (preload) of the spring and the additional compression of the spring  178  needed to permit the piston  176  to displace downwardly a sufficient distance for the seal  184  to enter the recess  186  are known. Therefore, the maximum pressure achieved in the flowpath  180  to cause the piston  176  to permit fluid communication between the flowpaths  180 ,  182  corresponds to a certain pressure in the flowpath  182 . By recording the maximum pressure achieved in the flowpath  180 , a person skilled in the art may readily determine the pressure of the pressure source in communication with the flowpath  182 . 
     As an example of a use of the tool assembly  160 , it may be interconnected to the control module  132  and positioned in a well in the method  10 . In that case, one of the lines  34  would be connected to the flowpath  152 , another one of the lines  34  would be connected to the flowpath  156 , one of the lines  36  would be connected between the flowpath  142  and the flowpath  172 , and another of the lines  36  would be connected between the flowpath  144  and the flowpath  180 . If it were desired to sense the temperature of the well proximate the tool assembly  160 , pressure in the flowpath  156  would be adjusted as needed to place the flowpath  152  in fluid communication with the flowpath  142 , and then pressure in the flowpath  152 , and thus the flowpaths  142  and  172 , would be gradually increased until fluid communication is permitted between the flowpaths  172 ,  174 . This pressure corresponds to a certain temperature of the fluid in the chamber  170 . If it were desired to sense the pressure in the well (for example, the pressure in the interior of the tubular string  20 , with the pressure sensor  164  configured as depicted in FIG.  11 ), pressure in the flowpath  156  would be adjusted as needed to place the flowpath  152  in fluid communication with the flowpath  144 , and then pressure in the flowpath  152 , and thus in the flowpaths  144  and  180 , would be gradually increased until fluid communication is permitted between the flowpaths  180 ,  182 . This pressure corresponds to a certain pressure in the flowpath  182 . 
     Note that these operations of sensing temperature and sensing pressure utilizing the tool assembly  160  may be repeated as often as desired by merely applying pressure to either of the flowpaths  172 ,  180 , and recording the pressure at which fluid communication is permitted between the flowpaths  172 ,  174  or between the flowpaths  180 ,  182 . 
     Although the temperature sensor  162  and pressure sensor  164  have been depicted in FIG. 11 as being combined in the tool  160  configured for interconnection in a tubular string, it is to be clearly understood that the sensors may be separately utilized, and that the sensors may each be used as components in other hydraulic circuits. For example, the sensors  162 ,  164  may be used as hydraulic circuit components in a manner similar to that in which other components, such as check valves, etc., are utilized in various hydraulic circuits. 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.