System and method for obtaining load measurements in a wellbore

A technique for determining conditions downhole in a well, particularly load conditions acting on a well tool, e.g. a bottom hole assembly. The loads acting on a bottom hole assembly or other well tool during a well related operation are measured. Load data is collected and may be transmitted uphole in real time for evaluation at a surface control unit. Based on the load data and other possible data related to the downhole operation, corrective actions can be taken to improve the operation.

BACKGROUND

A variety of hardware is used downhole to accomplish many types of well related operations. The hardware, e.g. well tool, often is delivered downhole as part of a tool string used to perform the desired operation. For example, well tools can be delivered downhole to perform drilling operations, treatment operations, tool actuation operations, measurement operations, fishing operations and other well related operations. During use downhole, the hardware can be subjected to a variety of loads, including compression loads, tension loads, torsion loads, shock loads, and vibration loads. If the loading becomes excessive, damage can be incurred by the downhole hardware.

Attempts have been made to detect and measure loading that occurs in a downhole environment. For example, downhole sensor packages with local data storage have been used to measure loads experienced by a downhole tool string during coiled tubing operations. The locally stored data is then retrieved for post job analysis. However, the delayed access to data limits the usefulness of the system with respect to making adjustments to reduce detrimental loading during the well related operation. There is no capability for optimizing performance through real time control. Other attempts have been made to send load data to the surface, but available systems have tended to be limited in data transfer capacity and accuracy. Other drawbacks associated with existing systems include relatively large outside diameters that restrict the usefulness of such systems in a variety of downhole operations.

SUMMARY

In general, the present invention provides a system and method for determining conditions at a well tool used in a downhole well related operation. The system and method comprise measuring loading on the well tool during a well related operation at a downhole position. Load data may be transmitted uphole for evaluation at a surface control unit. Although some applications may use locally stored data, other applications benefit from the transmission of some or all data uphole in real time. Based on the downhole operational data obtained, corrective actions can be taken to improve the operation.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The present invention generally relates to a system and method for detecting, measuring, and managing loads incurred by downhole equipment during various well related operations. The load data can be obtained in real time to facilitate a greater understanding of those loads and to enhance the ability to take corrective action. For example, the load data obtained downhole can be transmitted to a surface control unit for analysis and determination of appropriate corrective action. The data also can be used to synchronize the operational equipment downhole with the surface control unit. In some applications, responses to the load data can be automated via the surface control unit so that appropriate corrective actions are automatically taken to improve the well operation.

The system and methodology described herein can be used to detect and measure a variety of load forces to which a well tool may be subjected during a downhole operation. For example, load forces related to vibration forces, compressive forces, tensile forces, torque forces, shock forces and other types of load related forces can be detected, measured and transmitted uphole in real time. Depending on the downhole operation, other well related parameters also can be measured, and data on those parameters can be transmitted to the surface control unit. By way of example, some of these other parameters may include trajectory, reach, friction, drilling speed, motion, pressure, temperature and other parameters that can affect specific downhole operations.

Referring generally toFIG. 1, one embodiment of a system20is illustrated as deployed in a wellbore22. The system20is representative of a variety of well systems used in carrying out many types of well related operations, as explained in greater detail below. Additionally, system20is designed to detect, measure and transmit load related data from a downhole location to, for example, a surface location for analysis and use in improving the specific well operation being performed. In the application illustrated, the system is designed to transmit this load data in real time to enable immediate corrective action during the downhole operation. Additional parameter related data also can be detected, measured and transmitted in real time to facilitate the analysis.

In the example illustrated, system20comprises a well tool24that may be deployed to a desired location in wellbore22via a conveyance26, such as a coiled tubing conveyance, drill string, jointed pipe, or other conveyance. Well tool24is engaged with a load detection sub assembly28designed to detect one or more types of loading that can be incurred by well tool24. Sub assembly28sends load related data uphole to a surface control unit30, such as a computer-based control unit. The data is sent uphole via a communication line32, such as a fiber optic line. In the embodiment illustrated, load detection sub assembly28is connected to conveyance26via a connector assembly34which may be a “smart” connector assembly able to convert data from sub assembly28to a suitable format for transmission along a fiber optic communication line. Suitable electronics for transmitting data uphole in real time can be located in connector assembly34, sub assembly28, a combination of the two assemblies, or at other suitable locations along the tool string.

Load detection sub assembly28can be designed to detect one or more of a variety of load forces, e.g. compressive loads, tensile loads, torque loads, shock loads and other loads to which well tool24is susceptible. Additionally, a variety of sensors36also can be deployed downhole to detect and measure other well related parameters. Data on the additional parameters also can be sent uphole to surface control unit30via communication line32or via other suitable communication lines, including hard wired and wireless communication lines. By way of example, sensors36may comprise accelerometers, inclinometers, gamma ray sensors, gyros, pressure sensors, casing collar locators, and temperature sensors.

In many applications, the use of one or more fiber optic communication lines32greatly facilitates the real time transfer of data from load detection sub assembly28and potentially other sensors36. Fiber optic communication lines32also can be combined with the conveyance26, e.g. coiled tubing conveyance26, and deployed, for example, along the interior of the coiled tubing or within a wall of the coiled tubing. In a specific example, the fiber optic communication line32and coiled tubing conveyance26have been combined and are commercially available from Schlumberger Corporation. In one embodiment, coiled tubing26, fiber optic communication line32and connector assembly34are combined as a fiber optic telemetry platform available from Schlumberger Corporation. The platform can be used to sense a variety of wellbore parameters, e.g. temperature, annular pressure, applied pressure, and data on those parameters is transmitted to surface control unit30via fiber optic communication line32. In this embodiment, the load detection sub assembly28can be mounted to the bottom of the measurement platform as a modular extension.

The measurement platform generally comprises coiled tubing with a fiber optic tether deployed along an interior of the coiled tubing. The fiber optic tether has one or more optical fibers located inside a protective tube which may be formed of a metallic material or other material having suitable properties. The coiled tubing and the fiber optic tether have suitable upper and lower terminations or connections that allow fluid to be introduced into the coiled tubing and directed along the interior of the coiled tubing. However, different arrangements of optical fibers can be deployed in a variety of ways along coiled tubing, production tubing or other appropriate conveyances.

In the example illustrated, system20is deployed in a generally vertical wellbore that extends downwardly from a wellhead38positioned at a surface location40. However, system20and its load detection capabilities can be utilized in a variety of wells, including horizontal wells and other types of deviated wells. The system20also can be used in many types of environments and applications, including land based applications and subsea applications. The type of well tool or tools24used in cooperation with load detection sub assembly28may vary substantially depending on downhole operation. The illustrated well tool24is representative of a variety of well tools that are run downhole to perform one or more selected, well related operations.

For example, well tool24may comprise a bottom hole assembly used in a milling operation. In this example, the bottom hole assembly comprises a bit driven by a motor that operates via pressure applied with fluid flowing through conveyance26which is in the form of a tubing. The load detection sub assembly28can be used to detect load changes indicative of bit stalling. Stalling causes the overall rate of penetration to decrease because the operator must lift off and reposition the bit to begin milling again. Stalling also reduces bit life as well as the life of the motor and the coiled tubing. The sub assembly28is able to provide torque data experienced by the bottom hole assembly24in real time, and this torque loading is useful as an indicator of imminent stalling. The information enables early corrective action to prevent stalling and thereby increase the overall rate of penetration and improve component life. In this embodiment, sensors36can be used to provide additional information. For example, sensors36may comprise a gyro to indicate orientation, a gamma ray sensor to indicate depth correlation, an inclinometer to track orientation, and an accelerometer to detect shock and/or inclination. The accelerometer can be provided as a separate sensor or as part of the load detection sub assembly28.

In another application, well tool24comprises a bottom hole assembly, and load detection sub assembly28is used to measure loads associated with setting inflatable or mechanical packers. In deviated wells, for example, the set down weight required to actuate a packer is difficult to determine with surface measurements alone. The sub assembly28can be used to monitor and output data on the set down force actually being applied downhole. Tensile loads also can be measured and output to provide an indication as to how much force can be applied during removal of the bottom hole assembly. By providing this data in real time, disconnect forces can be avoided. Similarly, by monitoring the downhole loads, it is possible to prevent an overload situation that might damage the tool.

Similarly the load detection sub assembly28can be used to monitor and output load data when shifting sliding sleeves downhole. The sub assembly28provides information on set down weight or overpull applied to the sliding sleeve. Additionally, if the shifting tool does not disengage from the sleeve, precise load information can be provided in real time regarding the force applied to break the shear screws as necessary for disengagement. In a fishing operation, the sub assembly28can provide similar load data related to forces applied to dislodge the “fish”. Force load data can make the fishing operation faster, safer and more efficient.

In other applications, well tool24comprises a vibration tool that generates vibration downhole to reduce friction forces associated with moving the coiled tubing farther downhole. The performance of the vibration tool24can be monitored by sub assembly28and sensors36in real time to enable optimization of the operational parameters and thus enhance execution of the operation.

The well tool24also may comprise a tractor, and load detection sub assembly28can be used to measure loads incurred during tractoring operations. For example, it can be important to know whether the tractor is on or off and to also know the amount of force applied by the tractor while pulling the string. The sub assembly28is able to provide loading information in real time so that an operator has a more accurate understanding of the downhole operation of the tractor. The real time observation of loads also can prevent tool string failure and damage. Load data also can be used in combination with a variety of surface measurements and systems that enable optimal synchronization of tractor operation with coiled tubing unit surface controls to avoid overloads and to minimize failures.

In other applications, well tool24comprises a drilling tool, and sub assembly28can be used to provide load data similar to that described above with respect to the milling operation. For example, real time tracking of weight on the bit and torque applied to the drilling tool can be used to prevent stalls and to maximize rate of penetration.

The load detection sub assembly28also can be used in a variety of other operations. For example, the sub assembly can be used during perforating jobs to monitor loads induced as result of the perforating operation. In this application, the sub assembly28can be used to provide data indicative of how and whether the perforating guns have been activated. An integrated accelerometer also could be used to monitor shock, and a variety of other sensors can be used to provide data on various aspects of the perforating operation. The sub assembly28also can detect drag on the bottom hole assembly24and the coiled tubing string that results from excessive overloads of fill being lifted. Similarly, sub assembly28can be used to identify lock up situations, such as those that result from an obstruction rather than an inability to transmit loads to the bottom hole assembly.

Accordingly, the load detection sub assembly28provides a better understanding, in real time, of how the well tool24is being affected downhole by loading that results from a variety of forces, torques, vibrations and movements. This is particularly important in adverse scenarios when transmission of downhole loads is affected by well geometry, completions, fluids, and other downhole characteristics. The various measurements enable better operational analysis and improve the ability to take appropriate corrective action.

The sensors36and load detection sub assembly28also can be used in conjunction with a variety of other surface measurement and control systems. For example, systems are available that provide indications of coiled tubing weight or that prevent unplanned overloading situations. These additional systems can be operated by surface control unit30or in conjunction with surface control unit30. In many applications, surface control unit30can be programmed to automatically take certain corrective actions based on preset parameters when specific data is provided by load detection sub assembly28, sensors36, and/or other cooperating measurement and control systems.

Depending on the type of well tool24and the type of operation in which well tool24is utilized, the shape, size and configuration of load detection sub assembly28can vary. However, one example of load detection sub assembly28is illustrated inFIG. 2. In this embodiment, sub assembly28comprises an upper housing42, a load cell44, and a load cell housing46. Upper housing42comprises a connector end48opposite load cell44to enable connection of sub assembly28to connector assembly34via, for example, threaded engagement or another suitable engagement mechanism. At an opposite end, sub assembly28comprises a connector50that may be any of a variety of connectors depending on the well tool24to which it is connected for a specific well related operation.

Referring generally toFIGS. 3 and 4, cross-sectional views are provided of the sub assembly embodiment illustrated inFIG. 2. As illustrated, sub assembly28comprises a tubular member52extending from load cell44and partially defining a flow passage54formed through sub assembly28to accommodate fluid flow through sub assembly28. Additionally, sub assembly28comprises electronics56that may be mounted on a circuit board58for processing signals received from load cell44. Circuit board58may be mounted between tubular member52and upper housing42, as illustrated. Signals are transmitted from electronics assembly56to a communication line connector60which is designed for engagement with a corresponding connector in connector assembly34, thus enabling transmission of signals to the surface.

Sub assembly28comprises a chassis64that is disposed within upper housing42in a manner that does not obstruct flow passage54. Tubular member52may be formed as an integral part of chassis64. Also, chassis64is rigidly connected to or integrated with load cell44, as illustrated inFIG. 3. A pressure balancing seal structure68is installed at the lower or downhole end of load cell housing46and a seal is formed between seal structure68and the load cell housing46via a seal element69. Seal structure68extends up into an interior of chassis64and forms a seal with chassis64via a seal element70, as illustrated. In the embodiment illustrated, seal structure68is formed as a pressure compensating piston.

Sub assembly connections, such as the connection of the upper housing42with load cell44can be formed with split connectors71which allow the connection of components without requiring relative rotation of the electrical connections. With respect to electrical connections, wiring may be routed from connector assembly34and connector end48down along the outside diameter of chassis64. By way of example, the wiring may be terminated on the uphole side of circuit board58. From the downhole end of circuit board58, the wiring is further routed along or through chassis64and integrated load cell44. The wiring is brought to the outside diameter of the load cell44via one or more ports72, illustrated best inFIG. 4. Routing the wiring to the radially outward side of load cell44/chassis64allows the wiring to be appropriately connected to the load cell. For example, the wiring may be connected to load measurement sensors, e.g. strain gauges or other load measurement sensors, of the load cell44.

The wiring route and the arrangement of components in load detection sub assembly28enable the detection and monitoring of loads without having the load measurements skewed by extraneous elements. For example, the load measurements are isolated from the effects of radial and hoop forces caused by the pressure of fluid pumped along flow passage54and from similar effects due to pressure that is external to the tool. The load measurements also are isolated from axial forces induced by hydrostatic pressure in the wellbore. Accordingly, more accurate measurements of load forces, e.g. compressive and tensile load forces, are made possible, as illustrated inFIGS. 5 and 6.

Referring toFIG. 5, a compressive load path74is illustrated. The compressive load path74results from placement of sub assembly28under compressive loading and illustrates the components of sub assembly28that carry the load forces to load cell44. From the downhole end of the sub assembly28, the loading force is exerted through load cell housing46and transferred to chassis64and the load cell44via a threaded region76. The compressive load force travels through load cell44and chassis64.

InFIG. 6, a tensile load path80is illustrated. The tensile load path80results from placement of sub assembly28under tensile loading and illustrates the components of sub assembly28that carry the tensile load forces to load cell44. From the downhole end of the sub assembly28, the tensile loading force is carried through load cell housing46and transferred to chassis64and load cell44via threaded region76. The tensile load force travels up through load cell44and is transferred to the shouldered split ring connector71. Split ring connector71transfers the tensile loading to upper housing42and upward through the tool string.

Under torque loading, the torque loads can be transferred between upper housing42and load cell44via one or more torque keys82, as illustrated inFIG. 7. The torque keys82are engaged between load cell44and upper housing42such that any twisting loads acting on conveyance26are transmitted to load cell44via upper housing42and torque keys82.

The arrangement of components in system20and load detection sub assembly28facilitates the provision of accurate and immediate information that can be used to avoid failures and to optimize the downhole operation. For example, real time data can be communicated to surface control unit30via, for example, fiber optic telemetry. The fiber optic telemetry and arrangement of sub assembly28enable transmission of data while the downhole operation is underway, including while fluids are pumped through flow passage54. The design not only enables mechanical pressure compensation and radial temperature compensation but also eliminates the effect of “make-up force” on the strain gauge area of the load cell44.

By way of further explanation, the sub assembly28is designed to compensate both for the radial and hoop forces that are caused by the pressure of fluid as it is pumped along flow passage54, as well as for similar effects caused by pressure external to the tool. Additionally, the sub assembly28is designed to compensate for axial forces induced by hydrostatic pressure in wellbore22. Compensation for these extraneous pressure/forces is achieved in part by the design of load cell44which has a load sensor mounting area84for receiving one or more load measurement sensors86, e.g. strain gauges, optical load sensors, or other load sensors, as illustrated inFIG. 8.

The portion of the outside diameter of load cell44where the load measurement sensor86is mounted in and surrounded by a sealed atmospheric chamber88. Chamber88is sealed by a seal element90cooperating with seal elements69and70. Additionally, the chassis64which forms tubular member52and flow passage54is sealed downhole relative to the load sensor mounting area84by pressure balancing piston/seal structure68. Extra radial clearance can be added between the outside diameter of chassis64and the inside diameter of the load sensor mounting area84of load cell44to ensure contact does not occur due to pressure induced or thermally induced expansion of chassis64. Thus, the inside diameter of load cell44is only affected by atmospheric pressure in the chamber88.

Furthermore, the sealed area against which hydrostatic pressure can act extends from the outside diameter of pressure balancing seal structure68, in the region where it seals against the inside diameter of load cell housing46via seal element69, to the outside diameter of seal structure68, where it seals against the inside diameter of load cell44/chassis64via seal element70, as illustrated inFIG. 8. In the axial direction, seal structure68enables the compression caused by the hydrostatic pressure to bypass load sensor mounting area84. This effect is due to the outermost sealing diameter being the same on either side of the atmospheric chamber88. As a result, force is transferred to seal structure68which acts as a compensating piston. With respect to radial temperature differences, the atmospheric conditions surrounding load sensor mounting area84along both the outside and inside of load cell44negate any radial temperature differences in the section of load cell44containing strain gauges86.

With certain types of bottom hole assemblies, such as bottom hole assemblies that shoulder internally, the sub assembly chassis can be subjected to substantial compressive make-up forces during interactions downhole. However, when sub assembly28is “made-up” at its upper end, chassis64shoulders internally which causes compressive forces in the load cell44from the split connector ring71along its length in the uphole direction and in the chassis64from its connection with the load cell44along its length in the uphole direction. The load sensor mounting area84is not subjected to these make-up forces. Additionally, when the downhole end of sub assembly28is “made-up”, compression is only experienced by load cell44from the threaded region76of load cell housing46to the location where the load cell housing46shoulders against the load cell, as illustrated inFIG. 8. Accordingly, the load sensor mounting area84is not affected by the make-up forces.

InFIG. 9, an alternate embodiment of sub assembly28is illustrated. In this embodiment, the load detection sub assembly28comprises a passage92for receiving a downhole tool bus94, e.g. wires or cable, to provide communication and/or power to a desired device located below the sub assembly28. Many of the components in this embodiment are the same as those described above with reference toFIGS. 1-8, however passage92extends from an upper connector block96to a lower connector block98. The tool bus, e.g. wires, is connected between circuit board58and connector block96. From connector block96, the wires are passed through the passage92that extends through load cell44until reaching lower connector block98. To avoid rotating connections, a split ring connector100can be mounted proximate a lower end of the sub assembly28.

Tension and torsion are transmitted via a plurality of loading keys102, as illustrated inFIG. 10. The loading keys102are installed in corresponding slots104formed in a portion of load cell44. When the alternate sub assembly28is exposed to compressive loads, the loads are transferred directly from load cell44to chassis64, as described above. However, under tensile loading, the loads are transferred to upper housing42via loading keys102, and chassis64is bypassed. The loading keys are designed to fit snugly into slots104and corresponding slots of upper housing42. As a result, torsion loads also are transferred from the load cell44to upper housing42while bypassing chassis64. In this alternate embodiment, chassis64seals internally against load cell44downhole of the load sensors/strain gauges. This arrangement provides the same radial pressure and temperature compensation as described with respect to the previous embodiment. The effects of make-up forces on the load sensor mounting area84also are avoided in the same way as described with respect to the previous embodiment.

As described above, system20can be constructed in a variety of configurations for use in many environments and applications. The load detection sub assembly can be constructed to isolate a load sensor from extraneous loading internal to the sub assembly, external to the sub assembly, exerted axially, resulting from regular tool make-up, resulting from temperature and pressure effects and/or other extraneous loads. Additionally, the size and arrangement of the load detection sub assembly can be adjusted for environmental and operational factors. The types of load sensors and sensors incorporated into the load detection sub assembly, as well as the additional sensors utilized in conjunction with the sub assembly, can vary substantially depending on the desired operations and the desired parameters to be monitored. The electronics can be substituted with optical systems that rely an optical sensors. Additionally, the surface control unit30may combine a variety of systems and may be programmed in many different ways to facilitate monitoring, analysis, and the taking of corrective actions either automatically or with the assistance of an operator.

Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.