FIELD OF INVENTION

This invention relates to measuring systems, and more particularly to systems for measuring flow and differential pressure of a fluid stream and is particularly applicable to high pressure, downhole flow measurements in a well. BACKGROUND OF THE INVENTION

Differential pressure and flow measurement on surface flow lines is common technology and is relatively straightforward in that high temperatures and pressures are not usually encountered and in that there is no space or environmental conditions which inhibit the design considerations. In contrast to surface operations, downhole operations for flow measurements in a well bore have typically relied upon a spinner flowmeter which is disposed in a bore to measure flow velocity. A spinner flowmeter is a mechanical device which is subject to considerable error and malfunction problems because of the downhole production fluids land temperatures.

In oil well production or flow conditions, high temperatures and pressures and encountered. Gas can be in solution and change phase before or after flow measurements are made. High fluid pressures are difficult to measure as a differential pressure because the amount of static pressure also affects the measuring device and introduces error.

One solution which I have advanced is a torque measuring flowmeter which is described in U.S. Patent No. 5,463,903. This torque flowmeter utilizes a capacitance measurement of a torque force developed on a torque shaft where the torque force is developed by fluid flow acting on an impeller on the torque shaft. The capacitance measurement is a function of the fluid flow rate. This type of flowmeter can also be modified for use in a side pocket mandrel where surface read out of flow measurements can be made from a side pocket location which leaves a full opening bore for use by production and production tools. Details of this type of flowmeter configuration can be found in provisional application No. 60/003663, filed September 9, 1995. SUMMARY OF THE PRESENT INVENTION

In the present invention, a torque responsive capacitance sensor is utilized to measure the torque force developed by a differential pressure system where the differential pressures are developed as a function of fluid flow.

A suitable torque responsive capacitance sensor is illustrated in U.S. Patent No. 5,463,903 and basically consists of a torque responsive capacitance sensor system where torque applied to a torque shaft torques one capacitance base member about a torque axis

relative to a parallel capacitance base member so as to develop capacitances measurements as a function of torque.

The differential pressure system of the present invention includes a main bellows which has its interior and exterior accessed to a differential pressure to be measured. The differential pressure causes the main bellows to displace linearly along a bellows axis as a function of the differential pressure. The bellows has a main base member which is coupled by a torque converter means to the torque shaft of the capacitance sensor system. The torque converter means translates a linear movement of the main bellows along the bellows axis in response to differential pressure into a torque force about the bellows axis and transmits the torque force to the torque shaft.

The differential pressure across the rigid main base member of the main bellows can be developed in a well bore by a full opening choke located in the production bore of a side pocket mandrel with the measuring system of the present invention located in the side pocket of the side pocket mandrel. The choke develops a pressure differential between its inlet and its outlet in response to fluid flow and the pressure at the entrance (inlet) and exit (outlet) opening of the flow choke is accessed to opposite sides of the bellows. In response to fluid flow, the differential pressure developed moves the bellows with respect to a bellows axis and the linear movement of the bellows is translated by the torque converter means into a torque force on the torque shaft of the sensor where the torque force is a function of the fluid flow.

Because pressure overloads can occur, the main bellows is provided with an overload control bellows. The overload control bellows is attached to a check valve arrangement which closes in response to an overload pressure whenever an overload pressure develops a predetermined finite motion of the base member of the control bellows in either direction of the known pressure. The overload pressure is predetermined and preset.

The system can be used with a retrievable tool in a sidepocket mandrel with an inductive coupler, or with a fixed tool in a side pocket wired directly to the earth's surface, or with a retrievable self contained tool with a memory recorder in a sidepocket mandrel.

The system is particularly applicable for high pressure, high temperature environments where space is at a premium.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in cross-section of a system of the present invention in a well bore;

FIG. 2 is a view in cross-section of a side pocket mandrel useful with the present invention;

FIG. 3 is a view in cross-section of a tool embodying the present invention in an operative relationship to a conduit having a differential pressure section; FIG. 4 is an enlarged view of a detail of the present invention;

FIG. 5 is a view taken along line 5-5 of FIG. 4;

FIG. 6 is a side view of a torque converter for the present invention;

FIG. 7 is a plan view of a component for another form of a torque converter prior to construction; FIG. 8 is a plan view of the component of FIG. 7 after being configured;

FIG. 9 is a side view of components as shown in FIG. 8 in an assembled form;

FIG. 10-11 are diagrammatic illustrations of the function of the torque converter;

FIGS. 12-14 are views of some various configurations; and

FIG. 15 is a view in cross section of a retreivable choke device. DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, in one environment for the present invention, a well bore 20 traverses earth formations 21. A liner 22 is cemented in place in the well bore 20 and fluids are produced for the bore of liner 22 through perforations 23. The fluids are typically under pressure and at a temperature greater than ambient surface temperatures. The produced fluids can contain hydrocarbons, gas and water in various concentrations. In some instances, the gases are dissolved in solution and transform to a gaseous state before reaching the surface.

Production of the fluids is usually through a production string of pipe or tubing 24 which is attached to a production packer 25. In one aspect of the present invention, a side pocket mandrel 26 is located just above the production zone and a differential pressure system is installed in the side pocket mandrel 26. The data measurements of the differential pressure system are transmitted to a conventional surface readout means via a conductor means 27.

Referring next to FIG. 2, a suitable side pocket mandrel 26 is illustrated. The side pocket mandrel 26 has an offset pocket bore 32 which is parallel to a bore 34. The offset pocket bore 32 is sized to receive a side pocket tool 35 (see FIG. 3) in which the present invention can be incorporated. At the lower end of the offset pocket bore 32 is an upstanding inductive coupler probe member 36 which is adapted to be received in a coupler

bore member 38 of the side pocket tool 35 (See Fig. 3). The probe member 36 is coupled to conventional data recording means (not shown) at the earth's surface by the conductor means 27. A more detailed description of this type of mandrel can be found in provisional application No. 60/003663 filed September 9, 1995. As shown in Fig. 3 and Fig. 4, the side pocket tool 35 includes a torque capacitance sensor means 42 which has parallel base members with capacitance plates. A torque axis 44 extends longitudinally through the tool 35 and through one of the base members. A torque shaft 46 extends along the torque axis 44 and is attached to the one base member so that when torque is applied to the torque shaft 46, a torque rotative displacement of the attached base member occurs relative to the other base member with a corresponding change in capacitance. Thus, the torque force is used as a measuring medium. It should be appreciated that the displacement is in micro inches and well within the elastic parameters of the various materials used so that a repeatable and highly accurate displacement can be repeatedly made. Reference may be made to U.S. Patent 5,463,903 for further details of the capacitance sensor means.

In the present invention, a differential pressure developed by a fluid flow is sensed and is utilized to produce a linear force which is converted by a torque converter means into a torque force on the torque shaft 46. The flow rate is determined as a function of the differential pressure in a standard flow rate equation. The differential pressure is obtained in a conduit by use of a choke or venturi means formed by a length of reduced diameter bore 52 in a larger diameter conduit bore 50. As shown in Fig. 3, the bore 50 of a conduit has a reduced diameter portion 52 which develops a differential pressure ΔP between an inlet pressure Pj and outlet pressure P ₂ of a fluid flowing through the conduit. The conduit can be incorporated in a side pocket mandrel as shown in Fig. 2 and the reduced diameter bore 52 can be full opening for through passage of well tools.

The differential pressure sensor includes a housing 60 which can be tubular and contains a first main bellows 62 connected to a fixed base member 64 and to a movable main base member 66. The fixed base member 64 has a centrally located access opening 68 which admits fluids to the interior of the first main bellows 62. Thus, if the pressures

Pi and P ₂ are applied across the bellows main base member 66, the main base member 66 will respond with a linear axial movement with respect to a central axis 67 where the movement is proportional to the differential pressure.

To access the pressure P _j and P ₂ to the main bellows 62, the differential pressure housing 60 is provided with access ports 70, 72. The access ports 70, 72 are isolated by sealing means 74, 74a, 74b, which are disposed between the housing 60 and the bore 32 of the side pocket. Ports 76, 78 in the wall of the mandrel housing place the pressures Pi and P ₂ in the bore 50 of the housing in fluid communication with the access ports 70, 72. It will be appreciated that in some applications, if desired, conduits or pipes can be used to connect the ports 76 and 72 and the ports 76 and 70 or other variations can be employed to couple a differential pressure to the bellows 62.

The movable main base member 66 has a central opening 78 which is connected to an interior or second control bellows 80 and to a interior base member 82. The interior base member 82 has an axially extending port 68 connected to a check valve spool 84. The check valve spool 84 has valve heads attached to a central post so that a valve head is located on either side of the fixed base member 64. The valve heads are constructed and arranged to cooperate with complimentary formed valve seats to close off the interior of the bellows 62 in the event of an excessive overpressure event.The differential pressure to the exterior of the bellows 62 is limited by the travel of the bellows 80, 62 and an overpressure will not destroy the bellows.

The linear motion ofthe main bellows 62 is translated into a torque force by a torque converter means 86. The torque converter means 86, as shown in Fig. 10 translates a linear motion 88 into a rotative torque force 89 about the axis of the torque shaft 46.

Referring now to Figs. 4-6 the torque converter 86 includes a central disc shaped diaphragm member 90 supported between annular rings 92, 94. The diaphragm member 90 should have sufficient structural strength and rigidity in a transverse plane to impart a torque force to an attached torque shaft 46 yet have flexibility in the transverse plane to permit axial movement of the rings 92, 94 relative to the torque shaft 46. The rings 92, 94 have peripheral locations at 120 degree angular spacings from one another with recesses. The recesses respectively receive the central portions (see 100b, 98b) of wire members 96, 98, 100. The wire members 96, 98, 100 are respectively formed in a plane with a 45 degree angle with respect to a center section (see 100b) and the end sections (see 100c, lOOd). As illustrated in Fig. 5, there is a plane 102-102 which intersects the axis of the wire 102 and the plane is tangential or at right angles to a plane 104-104 which intersects the longitudinal axis of the torque shaft 46 and the longitudinal axis of the end sections (100c, lOOd). As a result of this configuration, movement of the bellows main base

member 66 toward the fixed member 106 on the tool causes the rigid wires to develop a torque force on the diaphragm 90. This illustrated schematically in Fig. 10, where a wire 100 is shown in a three dimensional view. The wire 100 has an upper end portion 100c which is axially aligned with a lower end portion lOOd. The radii 101 of the end portions 100c and lOOd from the central axis of the shaft 46 are equal and the wire 100 is disposed in a plane perpendicular to the radius (See Fig. 11). The central section 100b of the wire 100 attaches to the diaphragm 90 at a radius 105 which is greater than the radius 101. If a differential pressure moves the main base member 66 toward the fixed base member 106 the section of wire 100c between the bellows main base member 66 and the torque diaphragm 90 and the section of wire lOOf between the torque diaphragm 90 and the fixed base member 106 act to develop a torque force on the torque diaphragm 90 in a counterclockwise direction causing the torque shaft 46 to angularly torque through a displacement angle 115. The torque displacement of the torque shaft 46 is measured by the torque sensor means and is functionally related to the differential pressure which develops the torque displacement.

Referring now to Figs. 7 - 9, an alternate torque converter means is illustrated. As shown in Fig. 7, a sheet of metal can be stamped to have a generally disc shaped configuration 115 with tangential tab portions 116 - 118. Each tab portion has notches 116a, 117a, 118a which define a narrow connecting section 116b, 117b, 118b between an end section 116c 117c 118c and a body section 116d, 117d, 118d. The tab portions are disposed at 120 degree angles relative to a central axis 120. The body sections 116d, 117d, 118d are arrayed at a 45 degree angle with respect to the central body 122 and with respect to a plane on which the end sections 116c, 117c 118c lie. As shown in Fig. 9, two disk members are arranged in a back to back relationship where a plane through end sections 124c, 125, 126c of tab portions 124, 125, 126 is parallel to a plane through the end sections

117c, 118c, 116c.

The end sections 116c, 117c, 118c are attached to a fixed body member while the end sections 124c, 125c, 126c are attached to a main bellows diaphragm. A torque shaft 127 extending along the axis 120 is attached to a torque sensor means. The configuration produces a torque force about the axis in response to linear movement of a bellows main base member with respect to the axis 120.

Referring now to Fig. 12, a side pocket mandrel 130 is illustrated with a side pocket tool 132 having an induction coupler 134 to communicate data from a torque sensor means

136. The torque sensor means 136 measures differential pressure developed by a flow choke 138 in the production bore of the side pocket mandrel. The tool 132 can be inserted and retrieved with a wire line tool in a customary manner.

As shown in Fig. 13, a side pocket mandrel 140 can have a side pocket tool 142 having a battery powered memory system 144 for recording data as a function of time from a torque sensor means 146. The torque sensor means 146 measures differential pressure developed by a flow choke 148 in the production base of the side pocket mandrel. The tool

142 can be inserted and retrieved with a wire line tool in a customary manner.

As shown in Fig. 14, a side pocket mandrel 150 can have a side pocket tool 152 where a torque sensor measure 154 is coupled by a hard wired conductor 156 to the earth's surface. The torque sensor means 152 measures differential pressure developed in a flow choke 156 in the production bore of the side pocket mandrel. In this arrangement, the tool and side pocket are jointly inserted and received from a well bore with the production string of pipe or tubing. Referring again to Fig. 10, the angle φ between a horizontal plane and the wire portion lOOe is at 45°. Torque displacement of the wire portion lOOe is at a one to one ratio with respect to the linear bellows displacement. The length of a bellows can be increased and the angle φ decreased. For example with φ at 10°, the torque forces are increased almost five times as much with the bellows moving at about a 5 to 1 ratio. This can be singly expressed as

T _f = B _f tanψ where T _f is torque force,

B _f is bellows force, and φ is the angle of a wire portion to the horizontal plane. In respect to the description, from time to time, only a single wire member or wire portion has been referred to. It will be appreciated that the arrangement is symmetrical with three wire or displacement members equidistantly disposed about a torque axis. In terms of construction, the material utilized should be consistent with the environment of use. As an example, the materials can be inconel or stainless steel or other high strength materials with good elastic characteristics. The radius 105 (see Fig. 5) for the wire members at the base 106 can be 0.4 inches; the wire member 96, 98, 100 can have an

overall length of 1.026 inches with a 0.80 spacing between end portions 100c, lOOd. The wire members can have a diameter of 0.035 inches. The torque displacement is in microinches and is maintained well within the elastic characteristics of the material so that creep and distortion do not occur and repeatability in terms of position is maintained. A retrievable choke device is illustrated in FIG. 15. The device includes a tubular member 160 with an upper member 161 with a fishing neck 162, a central venturi or choke orifice section 164 and a lower section 166. There are first openings 168 at the throat of the venturi and second openings 170 at the base of the venturi which couple to the first and second openings of the pressure tool. O-ring grooves 172, 174 & 176 receive o-rings for sealing the openings 168 & 170 with respect to the receiving bore for the choke device.

Outwardly biased collet fingers are arranged to cooperate with a latching groove in the receiving bore to releasable retain the device in the receiving bore. The collet fingers are released by shearing shear pins 180 and permitting the collet fingers to retract relative to the latching groove. It will be apparent to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is disclosed in the drawings and specifications but only as indicated in the appended claims.