The invention is an apparatus for measuring pressure, which comprises a pressure communicating device (3) for location at a point (4) at which pressure is to be measured, a primary tube (1) containing a fluid for linking the pressure communicating device (3) to a control point (9) where the pressure information is required, a sealing device for sealing the primary tube (1) so as to form a closed system when the pressure communicating device (3) is closed, a pressure control device (6) for changing the pressure of the fluid within the primary tube (1), a volume measuring device (8) for measuring changes in the volume of the fluid within the primary tube (1) as the pressure of the fluid is varied, a pressure measuring device (7) for measuring the pressure of the fluid at some point within the fluid, and device remote from the control point (9), and a transmitter device for transmitting pressure information from the pressure measuring device to the control point (9).

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Patent
   RE38052
Priority
May 01 1992
Filed
Dec 09 1998
Issued
Apr 01 2003
Expiry
Apr 30 2013
Inventors
Kluth, Erh…
Assg.orig
Sensor Dyn…
Assg.curr
Sensor Dyn…
Entity
Large
Referenced by
4
References
17
Maint.:
all paid
DETAILED DESCRIPTION…
0. 27. A method for sensing at least one physical parameter existing at one or more points which are at a remote location, comprising:
providing at least one sensor, the at least one sensor being in physical sensing communication with a cable, the at least one sensor being capable of sensing at least one physical parameter;
passing at least portions of the cable along a primary tube;
flowing fluid along the primary tube and cable to move the at least one sensor to at least one of the points; and
sensing sensor information from the at least one sensor.
1. Apparatus for measuring pressure, which apparatus comprises pressure communicating means for location at a point at which pressure is to be measured, a primary tube containing a fluid for linking the pressure communicating means to a control point where the pressure information is required, sealing means for sealing the primary tube so as to form a closed system when the pressure communicating means is closed, pressure control means for changing the pressure of the fluid within the primary tube, volume measuring means for measuring changes in the volume of the fluid within the primary tube as the pressure of the fluid is varied, pressure measuring means for measuring the pressure of the fluid at some point within the fluid and remote from the control point, and transmitter means for transmitting pressure information from the pressure measuring means to the control point.
2. Apparatus according to claim 1 in which the primary tube is narrow bore hydraulic tubing whose change in dimension with pressure is either small or well-known.
3. Apparatus according to claim 1 in which the fluid in the primary tube is a hydraulic oil.
4. Apparatus according to claim 1 in which the pressure control means is such as to permit the pressure to be changed from one value to another under an external control.
5. Apparatus according to claim 4 in which the pressure control means is an arrangement in which a force acts on a piston inside a cylinder containing the primary tube fluid.
6. Apparatus according to claim 1 in which the pressure measuring means is a pressure transducer.
7. Apparatus according to claim 1 in which the pressure control means, the volume measuring means and an additional pressure measuring means are all located together at the control point.
8. Apparatus according to claim 1 and including temperature measuring means for measuring the temperature along the length of the primary tube.
9. Apparatus according to claim 8 in which the temperature measuring means is an optical fiber distributed temperature sensor, either outside or inside the primary tube.
10. Apparatus according to claim 1 in which the pressure measuring means is a pressure sensing means which is of such a dimension and structure that it is placeable inside the primary tube.
11. Apparatus according to claim 10 and including locating means for locating the pressure sensing means at a desired point within the primary tube.
12. Apparatus according to claim 1 10 and including means for removing the pressure sensing means.
13. Apparatus according to claim 10 and including a secondary tube which connects the furthest point at which the pressure sensing means may be located in the primary tube to the control point, so that a return path for the fluid in the primary tube is provided.
14. Apparatus according to claim 13 in which the pressure sensing means is located by means of controlling the flow of fluid through the primary and secondary tubes.
15. Apparatus according to claim 14 in which the means of controlling the flow of fluid through the primary and secondary tubes is a pump with a capability of reversible flow.
16. Apparatus according to claim 1 in which the transmitter means are optical fibers.
17. Apparatus according to claim 1 in which the pressure sensing means is a passive optical fiber sensor.
18. Apparatus according to claim 1 in which the pressure sensing means is a polarimetric interferometer optical fiber pressure and temperature sensor.
19. Apparatus according to claim 1 and including additional pressure communicating means connected at different points along the primary tube, and means of distinguishing which pressure communicating means is in which state when the pressure is changed.
20. Apparatus according to claim 15 in which the pressure measuring means is a plurality of pressure sensing means, and in which the pressure communicating means is a plurality of pressure communicating means, and in which at least one of the pressure sensing means is located at each pressure communicating means so that it is not necessary to take into account the position of the pressure communicating means by computing a correction.
21. Apparatus according to claim 1 and including additional pressure communicating means.
22. Apparatus according to claim 1 in which the pressure communicating means is switched between the ACTIVE state and the ON/OFF state by separate means than the pressure in the primary tube.
23. Apparatus according to claim 22 in which the pressure communicating means is switched between the ACTIVE state and the ON/OFF state using a slide or rotary valve, a separate hydraulic or electric line, and hydraulic or electric control means.
24. Apparatus according to claim 22 in which there is no mechanical interface between the fluid in the primary tube and the point at which pressure is to be measured, when the pressure communicating means is in the ACTIVE state.
25. Apparatus according to claim 24 and including reservoir means for supplying fluid that may be lost through the pressure communicating means.
26. Apparatus according to claim 1 and including a reference pressure sensor for calibrating the apparatus.
0. 28. A method according to claim 27 and further defined by communicating sensor information along at least one optical fiber forming at least part of the cable.
0. 29. A method according to claim 27 and further defined by flowing fluid along a secondary tube in fluid communication with the primary tube to remove the at least one sensor from the primary tube.
0. 30. A method according to claim 29 and further defined by flowing fluid through the primary tube in a first direction to move the at least one sensor to at least one of the points, and flowing fluid through the primary tube in a second direction opposite the first direction to remove the at least one sensor from the primary tube.
0. 31. A method according to claim 27 and further defined by providing the sensor information to a control point via the cable.
0. 32. A method according to claim 27, and wherein at least one sensor is a pressure sensor, and wherein the method is further defined by providing a pressure communicating means to communicate pressure from at least one of the points to the pressure sensor.
0. 33. A method according to claim 27 and further defined by measuring temperature along the primary tube.
0. 34. A method according to claim 33, and wherein the temperature is measured along the primary tube using an optical fiber temperature sensor.
DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a primary tube 1 is connected at one end to a chamber 2 and at the other end to a pressure communicating means 3 which is situated in region 4 whose pressure is to be measured. The primary tube 1, chamber 2, and communicating means 3, constitute a single connected volume and is filled with hydraulic oil 5, or some other virtually incompressible fluid, or one whose compressibility is well-known. The pressure in the chamber 2 is controlled by pressure control means 6, and is measured by pressure measuring means 7. The volume of the hydraulic oil 5 is measured by volume measuring means 8. Computing and controlling means 9 is used to change the pressure in the chamber 2 with the pressure control means 6 until a change in volume, caused by the pressure communicating means 3 changing state, is detected by the volume measuring means 8. Computing and controlling means 9 is then used to compute the pressure in region 4 from the pressure in chamber 2 obtained from the pressure measuring means 7, and the known height difference between the pressure communicating means 3 and chamber 2, and the known density of the hydraulic oil 5.

FIG. 2 illustrates an example of a suitable pressure communicating means 3 connected to primary tube 1. A membrane 10 is clamped between two blocks 11 so as to form two isolated volumes 12, on either side of the membrane, where one volume is exposed to the pressure in the region to be measured 4, and the other volume is exposed to the pressure in the primary tube 1. The inner surfaces 13 of the blocks 11 are such that, once the pressure on one side of the membrane 10 exceeds that on the other side by some threshold value, the membrane 10 will be constrained by the surface 13 so that there is little further change in volume as the pressure difference increases. The change in volume as the membrane 10 moves from one surface 13 to the other is sufficient to be detected by the volume measuring means 8 shown in FIG. 1.

FIG. 3 shows a preferred embodiment of the apparatus in which the temperature of the hydraulic oil 5 is measured along the length of the primary tube 1 between the pressure communicating means 3 and the chamber 2 (not shown in this Figure) using the sensing optical fiber 14 of a distributed temperature sensing measurement system. Computing and controlling means 9 (not shown in this Figure) is further used to derive the pressure difference between the pressure communicating means 3 and chamber 2 (not shown in this figure) from the known density of the hydraulic oil 5 as a function of temperature.

FIG. 4 shows a preferred embodiment in which pressure sensing means 15 is placed inside the primary tube 1 close to the pressure communicating means 3. The pressure sensing means 15 may be additional to, or replace, the pressure measuring means 7 shown in FIG. 1. The measured pressure information is transmitted from the pressure sensing means 15 to the computing and controlling means 9 (not shown in this figure) by a metal or optical fiber cable 16.

The pressure sensing means 15 may be operated in two different modes. In the first mode, when the pressure communicating means 3 is in the ACTIVE state, pressure sensing means 15 is measuring the pressure of an external region 4, and, in the second mode, when the pressure communicating means 3 is in the ON or OFF state, pressure sensing means 15 is measuring the pressure determined by the pressure at the control point plus the hydrostatic pressure of the column of fluid 5 in the primary tube 1 independently of the pressure in region 4. This permits the checking, conditioning and determination of a variety of performance parameters of the pressure sensing means 15, such as sensitivity and repeatability, without the need to remove the pressure sensing means 15 from primary tube 1, which is particularly advantageous.

In many uses of the present invention, it will be desirable to provide additional means of inserting and retrieving the pressure sensing means 15 shown in FIG. 4. Such means are provided in a preferred embodiment as shown in FIG. 5. The pressure sensing means 15 is attached to a piston 17 which is of a size and shape to create a significant obstruction to flow of the hydraulic oil 5 past the piston 17 so that piston 17 moves with the flow. A secondary tube 18 is provided which connects the end of the primary tube 1 to the chamber 2. A reversible pump 19 is used to cause a flow in either direction around the circuit made up of chamber 2, the primary tube 1, and secondary tube 18. The piston 17 will be carried by the flow and hence will insert or retrieve the pressure sensing means 15 according to the direction of the flow as determined by the pump 19.

FIG. 6 illustrates part of another preferred embodiment of the present invention, in which more than one pressure communicating means 3 is provided so that the pressure at several different regions 4 may be measured according to the present invention. The volume changes within the different pressure communicating means 3, as they change from their OFF states to their ON states, may be the same as, or different, from each other. In addition, a single pressure sensing means 15, or one adjacent to each pressure communicating means, may be provided.

In another embodiment, several pressure communicating means 3, each with different characteristics, are provided adjacent to each other such that they all measure the same region 4.

FIG. 7 illustrates another preferred embodiment of the present invention in which the pressure communicating means 3 is switched between the ACTIVE state and the ON/OFF state by a slide or rotary valve 20, a separate hydraulic or electric line 21 and hydraulic or electric control means 22. In this embodiment, there is no mechanical interface, such as the membrane 10 shown in FIG. 2, between the fluid 5 in the primary tube 1 and the fluid in the region 4 to be measured, when pressure communicating means 3 is in the ACTIVE state. Thus it would not be necessary to take into account the properties of the mechanical interface, such as the membrane 10 shown in FIG. 2.

In the embodiment shown in FIG. 7, it is desirable to prevent fluid from region 4 entering primary tube 1, and it may also be desirable to flow fluid 5 through pressure communicating means 3 into region 4. Accordingly, reservoir means 23 may be provided in order to supply the volume of fluid 5 needed to compensate for the flow through pressure communicating means 3.

If desired, the pressure control means 6 may be an arrangement in which a force acts on a piston 24 inside a cylinder 25 containing the primary tube fluid 5, see FIG. 6.

INVENTORS:

Kluth, Erhard Lothar Edgar

THIS PATENT IS REFERENCED BY THESE PATENTS:
Patent Priority Assignee Title
10329855, Dec 06 2013 Schlumberger Technology Corporation Control line assembly and fabrication technique
6758271, Aug 15 2002 SENOR HIGHWAY LIMITED System and technique to improve a well stimulation process
7607477, Sep 06 2006 Baker Hughes Incorporated Optical wet connect
9291789, Dec 17 2013 Halliburton Energy Services, Inc Pumping of optical waveguides into conduits
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ASSIGNMENT RECORDS    Assignment records on the USPTO
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Dec 09 1998Sensor Dynamics, Limited(assignment on the face of the patent)
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Jun 23 2003STOL: Pat Hldr no Longer Claims Small Ent Stat
May 04 2004M1552: Payment of Maintenance Fee, 8th Year, Large Entity.
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