Mounting bracket for strain sensor

The subject matter of this specification can be embodied in, among other things, a system for mounting a strain sensor on a tubular pipe, which includes a mechanical clamp. The clamp has a bottom flexing section having an arcuate portion terminating at a first terminal and at a second end, and a first and second upper flexing sections having an arcuate portions terminating at first terminal ends and at second terminal ends in a pivot pin assembly having a bore parallel to a central longitudinal axis of the clamp, the bore there through for receiving a removable connector. Sensor mounting arms are disposed outwardly on the first and second upper flexing sections, said sensor mounting arms including at least one receptacle sized to receive and retain ends of a strain gauge.

CLAIM OF PRIORITY

This application is a U.S. National Stage of International Application No. PCT/US2013/077990, filed Dec. 27, 2013.

TECHNICAL FIELD

This present disclosure relates to an apparatus for mounting sensors on pipe sections.

BACKGROUND

In connection with the recovery of hydrocarbons from the earth, wellbores are generally drilled using any of a variety of different methods and equipment. According to one common method, a drill bit is rotated against the subsurface formation to form the wellbore. The drill bit may be rotated in the wellbore through the rotation of a drill string attached to the drill bit and/or by the rotary force imparted to the drill bit by a subsurface drilling motor powered by the flow of drilling fluid down the drill string and through downhole motor.

The flow of drilling fluid can exhibit variations in pressure. These pressure variations can cause dimensional changes in solid structures such as piping that carries the drilling fluid to and from the drill string. Strain gauges are used for detection and measurement of absolute dimensional changes of solid structures, such a piping for drilling fluid, but such changes are generally very slow and difficult to observe with known equipment and measurement methods.

DETAILED DESCRIPTION

This document describes systems and techniques for mounting sensor attachments to drilling fluid (also referred to in the industry as drilling mud) piping on drilling rigs. The assemblies described in this document can be used to mount several different types of optical sensors, including temperature, pressure, and/or strain sensors. Some of these sensors can be optical sensors and gauges based on the operating principles of a Fiber-Bragg grating and/or Fabry-Pérot interferometer.

In general, optical sensor mounts clamp, attach, or are otherwise affixed to an outside surface of one or more pipes in the drilling fluid piping system. Fluid (for example, drilling fluid) flowing through the pipe exerts a pressure force outward against the pipe, which causes small changes in the diameter of the pipe that vary with the pressure of the fluid within. The optical sensor mounts mechanically transfer, and in some implementations, amplify or reduce, changes in pipe diameter to one or more sensors. The signal outputs of such sensors can then be processed to observe changes in the diameter of the pipe. The changes in diameter of the pipe diameter may be processed using known physical characteristics of pressure pipes as described, for example, in “Pressure Vessel Design Manual” by Dennis Moss. Detection of said changes can allow for downhole pressure pulse detection whereas said pressure pulses can convey the specific information or data content, examples of which are described in Halliburton patents U.S. Pat. Nos. 7,480,207B2 and 7,404,456B2.

FIG. 1is a perspective view of an example optical sensor mount100. The mount100is a generally circular mechanical clamp having an inner diameter102sized to accommodate an outer diameter of a pipe (not shown) on which the mount100is to be mounted. The mount100includes three main sections, including a bottom flexing section120, a first upper flexing section140, and a second upper flexing section160.

The bottom flexing section120is a generally semi-circular arcuate portion, having a terminal end122ain a mounting wing124a, and a terminal end122bin a mounting wing124b. The mounting wing124ais formed generally perpendicular to the terminal end122a, and the mounting wing124bis formed generally perpendicular to the terminal end122b. The mounting wing122aincludes a bore126a, and the mounting wing122bincludes a bore126b, the bores126a-126bfor receiving a removable connector (not shown) such as a bolt or other appropriate fastener.

The bottom flexing section120has a thickness128. The bottom flexing section120includes a subsection130that has a thickness132that is less than the thickness128. In some implementations, as the bottom flexing section120flexes, the relatively lesser thickness132of the subsection130may cause distortion of the bottom flexing section120to be at least partly concentrated along the subsection130.

The upper flexing section140includes an arcuate portion142that is generally quarter-circular in shape, terminating at a terminal end143in a mounting wing144and a terminal end146in a mounting wing148. The mounting wing144is formed generally perpendicular to the terminal end143and includes a bore150for receiving a removable connector (not shown) such as a bolt or other appropriate fastener when the bore150is aligned with the bore126ato removably affix the upper flexing section140to the bottom flexing section120.

The mounting wing148is formed generally tangent to the terminal end146and includes a pivot pin assembly152having a bore153that is formed parallel to a central longitudinal axis103of the mount100. The bore153is formed to receive a removable connector (not shown) such as a bolt or other appropriate fastener.

A sensor mounting arm154extends generally perpendicular from the upper flexing section140. The sensor mounting arm154including at least one receptacle156sized to receive and retain an end192aof a sensor190, such as a strain gauge, an optical sensor, a Fiber-Bragg grating, a Fabry-Pérot interferometer etalon, or any other appropriate sensor.

The upper flexing section160includes an arcuate portion162that is generally quarter-circular in shape, terminating at a terminal end163in a mounting wing164and a terminal end166in a mounting wing168. The mounting wing164is formed generally perpendicular to the terminal end163and includes a bore170for receiving a removable connector (not shown) such as a bolt or other appropriate fastener when the bore170is aligned with the bore126bto removably affix the upper flexing section160to the bottom flexing section120.

The mounting wing168is formed generally tangent to the terminal end166and includes a pivot pin assembly172having a bore174that is formed parallel to the central longitudinal axis103of the mount100. The bore174is formed to receive a removable connector (not shown) such as a bolt or other appropriate fastener when aligned with the bore153.

A sensor mounting arm175extends generally perpendicular from the upper flexing section160. The sensor mounting arm175including at least one receptacle176sized to receive and retain an end192bof the sensor190.

The mount100includes a collection of adjustment rods180. The adjustment rods extend through the mount100inwardly in a radial direction toward the longitudinal axis103of the mount100through a collection of adjustment openings181. The inward end of each of the adjustment rods180terminates in a landing pad182. The adjustment rods180and the landing pads182form a collection of adjustment assemblies184formed to move the adjustment rods180and the landing pads182into adjustable contact with the pipe on which the mount100is to be mounted. In some embodiments, the adjustment assemblies184can include female threads in each of the adjustment openings, and the adjustment rods180can include at least a portion with male threads adapted to be received in the female threads. In some embodiments, compression pads can be affixed to the landing pads182. In some embodiments, the compression pads can include layers of vibration and acoustic noise absorbing material.

When assembled in a substantially unstressed or a predetermined pre-stressed or strained configuration, the sensor mounting arms154and175are oriented substantially parallel to each other. In such a substantially parallel configuration, the sensors190are stressed to substantially the same degree. For example, two sensors190in the example parallel configuration can provide substantially the same outputs, which can be used to cancel out common mode noise differential measurement configurations.

In some implementations, the mount100can be removably affixed to a pipe by placing a fastener though the bores126aand150, and by placing another fastener through the bores126band170, while omitting a fastener from the pivot pin assemblies152,172. In such an example configuration, as the pipe varies in diameter (e.g., due to variations in pressure of the fluid within the pipe), the unfastened pivot pin assemblies152,172can separate slightly, causing the sensor mounting arms154and175to move away from their substantially parallel, unstressed configuration. As the sensor mounting arms154and175diverge, the sensors190mounted at different radial positions on the sensor mounting arms154and175will experience differing amounts of stress. In some implementations, the differing amounts of stress can produce a differential signal by the sensors190that can be processed to determine the absolute or change in fluid pressure within the pipe.

Referring now toFIG. 4, a simplified version of the mount100is shown to illustrate one example effect of stress upon the mount100. In the illustrated example, the upper flexing sections140,160are removably affixed to the bottom flexing section120by a pair of bolts410and the restraining bolt (not shown here) is inserted in the bores153,174. When the mount100is clamped about a pipe (not shown) that is substantially unpressurized and therefore substantially unexpanded, the mount100can take on the configuration shown in solid lines. When the pipe is pressurized, the walls of the pipe will expand. This expansion will cause the sensor mount arms154and175to converge or otherwise move relatively closer, taking on the configuration shown in dotted lines.

Referring again toFIG. 1, in some implementations, a linking plate195can be removably affixed to the radially distal ends of the sensor mounting arms154and175with respect to each other, mechanically linking the sensor mounting arms154and175to each other. By linking the sensor mounting arms154and175to each other through the linking plate195, the movement of the sensor mounting arms154and175as the pipe expands and contracts can be modified. In some implementations, the linking plate195may be used as an aid to assembly of the mount100about the pipe. For example, the linking plate195may be used to temporarily affix the upper flexing sections140,160during assembly, and may be removed after the upper flexing sections140,160are affixed to the bottom flexing section120.

Referring now toFIGS. 5 and 6, simplified versions of the mount100are shown to illustrate the effects of the linking plate195on the flexure of the mount100.FIG. 5is a conceptual example configuration500of the mount100without the linking plate195and without the restraining bolt. In the example configuration500, as the pipe (not shown) expands within the mount100, the sensor mounting arms154and175move from their substantially unstressed or pre-stressed configuration, as depicted in dotted lines, relatively apart to the stressed configuration depicted in solid lines. In general, without the linking plate195in place, the radially distal ends510of the sensor arms154and175will move relatively further apart from each other than will more radially proximal portions520of the sensor arms154and175.

In some implementations, as the pressurized pipe's diameter D increases by X, the strain can be expressed as a ratio X/D. The same displacement X applied over a shorter distance L between expansion arms can lead to strain amplification because X/L>>X/D.

FIG. 6is a conceptual example configuration600of the mount100with the linking plate195affixed across the sensor mounting arms154and175and the restraining bolt not present. In the example configuration600, as the pipe (not shown) expands within the mount100, the linking plate195partly constrains movement of the radially distal ends510, causing the radially proximal portions520of the sensor mounting arms154and175to move from their substantially unstressed or pre-stressed configuration, as depicted in dotted lines, relatively apart to the stressed configuration depicted in solid lines. In general, with the linking plate195in place, the radially proximal portion520of the sensor mounting arms154and175will move relatively further apart from each other than will more radially distal ends510of the sensor arms154and175. When the linking plate195is used, the pipe diameter expansion, which can be expressed as dD=X, can result in a minimal top gap increase Xmin at ends of sensor mounting arms154and175near the linking plate whereas Xmin is close to zero with additional and relatively larger Xmax increase in distance between arms at location closer to the pipe whereas Xmax can be approximated as Xmax=˜PI*X.

Referring again toFIG. 1, in some implementations, a pivot pin (not shown) can be inserted through the bores148,168of the sensor mounting arms154and175. By placing the pivot pin in the bores148,168, as the pipe expands and contracts, the divergence of the sensor mounting arms154and175will pivot about the pivot pin. For example, as the pipe expands, the sensor mounting arms154and175can be caused to diverge from their substantially parallel, unstressed configuration and the arms will move inwardly at an angle toward each other.

In some embodiments, the pivot pin can be compressible or otherwise deformable, or can include a compressible or otherwise deformable coating about a substantially non-compressible core rod. In some implementations, the use of selected compressible or deformable components for the pivot pin can provide selectable modification of convergence or divergence of the sensor mounting arms154and175. For example, by including a compressible pivot pin in the pivot pin assemblies152,172, separation of the pivot pin assemblies152,172can be permitted in a reduced manner relative to movement that may occur with or without the use of a non-deformable pivot pin.

In some embodiments, the linking plate195can be formed to have a selected spring coefficient. For example, the stiffness of the linking plate195can be selected to selectably modify the divergence of the sensor mounting arms154and175under various stress configurations. In some embodiments, one or more sensors can be mounted on the linking plate195. For example, sensors can be configured to provide signals that indicate tensile, compressive, or bending stresses at the linking plate195. In some embodiments, one or more sensors can be mounted between inner surfaces of the sensor mounting arms154and175and/or in any other suitable section of120,140, and/or160. For example, a load cell can be mounted between the sensor mounting arms154and175to provide a signal in response to relative inward and outward movements of the sensor mounting arms154and175.

While the present example is shown and described as including four sets of the adjustment assemblies184, various implementations can include any appropriate number of the adjustment assemblies184mounted through corresponding ones of the adjustment openings181. For example, one of the adjustment assemblies184can be mounted on the upper flexing section140, and another one of the adjustment assemblies184can be mounted in the adjustment opening181located in the bottom flexing section120approximately 180 degrees away. In another example, one of the adjustment assemblies184can be mounted in each of the upper flexing sections140,160, and a third one of the adjustment assemblies184can be mounted in the adjustment opening181located in the central section of the subsection130.

FIGS. 2 and 3are exploded and perspective views of another example optical sensor mount200. In general, the mount200is removably or permanently affixed to a pipe201to mechanically transmit variations in the diameter of the pipe201to a collection of sensors202, such as a strain gauges, optical sensors, Fiber-Bragg gratings, Fabry-Pérot interferometers, or any other appropriate sensors.

The mount200includes a pair of mounting blocks210each having a proximal surface212and a distal surface214. The proximal surfaces212are positionable adjacent to an outer surface203of a wall204of the pipe201, and spaced about 180 degrees apart from each other.

The mount200includes a pair of sensor mounting arms220. One of the sensor mounting arms220is removably affixed to each of the distal surfaces214by a collection of fasteners222, such as bolts, screws, or other appropriate connectors. The sensor mounting arms220each includes a receptacle224configured to receive and retain an end232of a stem rod230. The ends232are further retained by fasteners231, such as nuts, retaining pins, or other appropriate connectors. In some embodiments, the ends232and the fasteners231can form a tension adjustment mechanism for the stem rod230. For example, the adjustment mechanism can include male threads on at least one of the ends232of the stem rod230, and the fasteners231can include female threads adapted to engage the male threads of the stem rod230. In such examples, the fasteners231can be threaded along the ends232to adjust the tension along the stem rod230.

The stem rod230includes at least one longitudinal receptacle234in an outer surface of the stem rod230. Each of the longitudinal receptacles234is formed to receive and retain one of the sensors202. The stem rod230has a first cross sectional area236at a central portion of one of the longitudinal receptacles234, and a second cross sectional area238at a central portion of another one of the longitudinal receptacles234. As discussed later herein, the cross sectional areas may be the same or different.

In some implementations, a magnet240is located in a receptacle242formed in each of the proximal surface212of the mounting blocks210. The magnets240include a first surface244positionable adjacent to the outer surface203of the wall204of the pipe201, and a surface246positionable adjacent to the mounting blocks210. In some embodiments, the mount200can be mounted to the pipe201by the magnets240. In some embodiments, the mount200can be mounted to the pipe201by welding, gluing, or otherwise adhering the mounting blocks210to the pipe201.

The mount200is assembled in a predetermined strain condition in which the sensor mounting arms200are generally parallel to each other and the stem rod230is mounted generally perpendicular to a longitudinal axis of each of the sensor mounting arms220. The pressure of fluid flowing through the pipe201exerts pressure on the wall204, causing variations in the diameter of the outer surface203. As the diameter changes, the distance between the mounting blocks210changes as well. Since the mounting blocks210are connected to each other though the sensor mounting arms220and across the stem rod230, as the pipe201expands and contracts the stem rod230is caused to expand or contract and/or flex. The sensors202, mounted in the receptacles234, are caused to expand or contract and/or flex along with the stem rod230and provide signals that vary as a function of the flexure and the compressive or tensile stress in the rod.

In some embodiments, the first cross sectional area236can have a different cross sectional area than the second cross sectional area238. In such embodiments, the first cross sectional area236will expand or contract or flex at a different rate than the second cross sectional area238relative to the expansion and contraction of the pipe201, and the differing rates of expansion or contraction and flexure can produce differing amounts of stress among the sensors202. In some implementations, the differing amounts of stress in the sensors can produce a differential signal that can be processed to determine the absolute or changes in fluid pressure within the pipe. In some implementations, the thicknesses of the stem rod230, the first cross sectional area236, and the second cross sectional area238can be formed to selectively determine the amount compression, tension or flexure that occurs along the stem rod230, and/or between the sensors202.

Although a few implementations have been described in detail above, other modifications are possible. For example, logic flows do not require the particular order described, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.