Abstract:
A dynamic position sensing Apparatus or Method is used to underream an oil or natural gas well with a variable gauge positioning system incorporating underreamer position or diameter sensing means.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-and-part of U.S. Ser. No. 12,966,195 granted U.S. Pat. No. 8,511,404 which claims priority from U.S. Ser. No. 12,966,195 based on WO 156552A1 PCT  2009  and GB0811815.0 (27.06.2008) granted GB 2460096. 
         [0002]    This application is a continuation-and-part of copending U.S. patent application Ser. No. 12,966,195 filed Dec. 13, 2010, and entitled “DRILLING TOOL, APPARATUS AND METHOD FOR UNDERREAMING AND SIMULTANEOUSLY MONITORING AND CONTROLLING WELLBORE DIAMETER”, which is a continuation-and-part of International Application number PCT/ES09/70261, filed Jun. 27, 2009 and entitled “DRILLING TOOL AND METHOD FOR WIDENING AND SIMULTANEOUSLY MONITORING THE DIAMETER OF WELLS AND THE PROPERTIES OF THE FLUID”, and claims priority to and the benefit of GB 0811815.0, filed Jun. 27, 2008 and entitled “Expansion and Calliper Tool”, the entireties of which applications are hereby incorporated by reference as if fully set forth herein. 
     
    
     FIELD OF THE INVENTION 
       [0003]    This invention relates to a dynamic sensing underreamer capable of detecting reamer diameters or positions and the terms reamer or underreamer are used to designate an expandable tool. In one embodiment this invention relates to a tool, apparatus and method capable of enlarging and dynamically sensing positions or diameters of expandable tools, especially, expandable reamers for use in wellbores in the oil and gas industry. The expandable blocks of the tool can be configured with cutting or stabilising elements locatable in a plurality of known positions that form a variable gauge expansion tool. Dynamic position sensing means provide data on the reamer status or diameter and position sensing may be via analogue or digital means. 
         [0004]    Alternatively or additionally further embodiments of the invention allow for acoustic sensors or mechanical gauge probes to measure the underreamed wellbore diameter. Further measurements where required can be obtained such as formation properties, vibration, rpm, rotation, flow, hydraulic force, pressure, torque, temperature. 
         [0005]    Additionally or alternatively pressure or flow indicators based on the location of the block or the location of a detector may also be used to sense or indicate or infer or signal the position of the blocks. Variations in sensors or signals may be electrical, mechanical or a combination of both. It is not essential that physical sensors measure the distance in such an embodiment because the radially extended positions or underreamer diameters may be sensed by indicative means. Such types of embodiments may be considered modular as they can be configured in separate modules or housings yet sharing common features. 
         [0006]    It is to be understood that the term ‘expansion’ as used herein refers to the capacity of the tool to expand outwardly and against the interior wall of a passage, such as a borehole, especially a wellbore, or a tubular used as a casing, and then to apply pressure or a cutting action against the wall. It is not always essential that the wall itself be expanded, since the tool can be used for centralisation or stabilisation or like purposes without necessarily expanding the passage. 
         [0007]    When constructing an exploration or production well, numerous downhole operations are conducted to drill and measure the borehole so that it meets the desired dimensions specified in the well-plan. 
         [0008]    An underreamer (which covers all manner of reamers, expandable reamers, extendable reamers and the like) is used to enlarge the diameter of the borehole beyond its original drilled size. Enlargement (underreaming or reaming using expandable/extendable tools) is typically done below a restriction in the borehole, and the cutting diameter of an underreamer is always greater than that of the pass-through diameter of the restriction. Additionally, an underreamer is provided with activation and deactivation modes and mechanisms for extending and retracting cutting elements to ensure effective underreaming once it has passed below the restriction. 
         [0009]    The time-lag associated with the separated operations of underreaming and measurement leads to uncertainty and unnecessary cost. 
       BACKGROUND OF THE INVENTION 
       [0010]    Oil and gas accumulations are found at depth in different geological basins worldwide. Exploration and production of such accumulations rely on the construction of a well according to a well plan. 
         [0011]    Various well types exist and are defined according to usage such as wildcats or those used in exploration, delineation, and production and injection. Variations in well profile exist also according to vertical, slant, directional and horizontal trajectories. Each well differs according to the oil company&#39;s objectives and the challenges that a given basin presents from the surface of the earth or the ocean to reaching the hydrocarbon reservoir at a given underground depth. 
         [0012]    Engineering challenges are related to the location of the well-site such as onshore or offshore, seawater depths, formation pressures and temperature gradients, formation stresses and movements and reservoir types such as carbonate or sandstone. To overcome these challenges, a highly detailed well plan is developed which contains the well objective, coordinates, legal, geological, technical and well engineering data and calculations. 
         [0013]    The data is used to plot the well profile, and plan its execution using precise bearings, which is designed in consecutive telescopic sections—surface, intermediate and reservoir. To deliver the well objective and maintain the integrity and operating capacity of the well over its lifecycle, a given wellbore with multiple sections and diameters is drilled from surface. Although there are many variants, a simple vertical well design could include the following dimensions: a surface or top-hole diameter of 17½″ (445 mm), intermediate sections of 13⅝″ (360 mm) and 9⅝″ (245 mm) narrowing down to a bottom-hole diameter of 8½″ (216 mm) in the reservoir section. 
         [0014]    Each consecutive section is ‘cased’ with a number of metal tubes placed into the wellbore with the specified diameter according to the length of the section. Casing tubes are connected to each other after which they are cemented into the outer wall of the well. In this way, a well is constructed in staged sections, each section dependent on the completion of the previous section until the well is isolated from the formation in question along the entire distance from surface to the reservoir. 
         [0015]    Scarcity of oil and gas is driving oil and gas companies to explore and develop reserves in more challenging basins such as those in water-depths exceeding 6,000 ft ( 1800   m ) or below massive salt sections. These wells have highly complex directional trajectories with casing designs including 6 or more well sections. Known in the art as ‘designer’ or ‘close tolerance casing’ wells, these wells have narrow casing diameters with tight tolerances and have created a need to enlarge the wellbore to avoid very narrow reservoir sections and low production rates. 
         [0016]    Therefore, the bottom-hole assemblies that are needed to drill these wells routinely include devices to underream the well-bore below a given casing diameter or other restriction. In this way, underreaming has become an integral part of well construction and there is now an increased dependence on underreaming to meet planned wellbore diameters. 
       SUMMARY OF THE INVENTION 
       [0017]    The present invention has for a principal object to provide an improvement on the prior art in wellbore underreaming and wellbore measurement wherein the actual position of the underreamer is sensed or indicated. 
         [0018]    Measurement may involve the acquisition and communication to surface of various types of wellbore data such as azimuth, inclination and borehole diameter or rugosity, formation types, dips or bedding angles. 
         [0019]    The present invention seeks to provide certainty of operation of underreaming and eliminates the need for separate corrective underreaming runs by providing real-time data which allows the driller to respond earlier thereby saving time and money on wellbore operations. 
         [0020]    It is thus an object of the present invention to provide reaming expansion blocks integrated with position sensing which can be used to assess the functioning and diameter of the wellbore-widening operation and, if the position and diameter is found insufficient or undergauge, to automatically detect and diagnose the potential faults, and to repeat underreaming until a satisfactory result is achieved. It is a further embodiment of the invention that provides the measurement of wellbore diameter as well as other measurements such as formation characteristics. 
         [0021]    Although underreaming is the principal route to wellbore diameter enlargement, the invention may be applied to enlargement means integrated with bicentre bits, fixed wing bits, eccentric underreamers and expandable bits. 
         [0022]    The tool is principally enabled to detect reamer positions or reamer diameters. In a separate and further embodiment the tool can conduct diagnostics according to a logic circuit. In this way, the user can achieve a planned or desired underreamer activation or deactivation and at any given time check that the underreamer is functioning correctly. This reduces downtime and uncertainty. 
         [0023]    In such an embodiment of the invention the tool may be linked to a micro-processor. Additionally or alternatively the tool may be further linked to a MWD/LWD. Such types of embodiments may be considered modular as they can be configured in separate modules or housings yet sharing common features. 
         [0024]    In this way, different types of modular solutions may be provided according to the need of the wellbore underreaming operation. For example, an underreamer with positional sensing only, an underreamer with positional sensing and other measurements such as calliper or vibration or underreamer with calliper only. These solutions can be configured to provide increasing levels of problem solving according to the application. For example if a problem occurs and if the corrective steps have been taken and the underreamer position sensing indicates an undergauge position then this may solve the problem in certain applications such as swelling shales or radial shrinkage. For other applications, such as requiring tight tolerances, a further caliper measurement may indicate that the desired hole diameter is still not being delivered a signal may be sent to the rig-surface or to the location of the operating engineer so that further remedial action can be taken, according to a logic circuit. This may include extending cutter blocks in response to caliper data, checking block positions or any number of logic steps. A memory card may store sensor information that can be downloaded at surface when the tool is retrieved, or sent to the surface by telemetry. In this way, the invention is entirely flexible and configured according to the application. 
         [0025]    The invention can be configured with a modular processor which can be linked to a MWD pulser and capable of receiving data such as azimuth, inclination and borehole diameter or rugosity, formation dips or bedding angles. 
         [0026]    The tool may also have a built-in link to a mud-pulse telemetry system to allow real-time monitoring of the under-reaming operation (cutter-block position, caliper measurements, fluid properties, pressure, rotation, torque, etc). 
         [0027]    In the underreamer and positional sensor module there may or may not be a keyway to provide a channel for wiring to and from the sensors to a processor and MWD when such components are configured. The wiring can be used to transmit other data retrieved by other sensors, as well as positional data from the mechanical blocks, to the processor. The processor can process this data and sends it to the transponder to be sent to the control system at the surface. The keyway may be sealed and filled with a means to absorb vibration such as silicone gel or grease and to maintain wires in position. 
         [0028]    In the embodiment of the underreamer with positional sensors the tool itself may communicate to surface by wired or wireless means. Additionally or alternatively the processor can transmit data to the surface by means of a mud-pulser which uses a series of binary codes at a given frequency using drilling fluid as means of transmission. Other means of wireless transmission can be used, using radio frequency or electro-magnetic pulses. This allows up and downlink of the tool in order to receive and transmit data and commands. The data may be transmitted to the surface for use by the drilling operator or may be further transmitted by satellite to a remote operations centre. 
         [0029]    One embodiment of the invention provides for a wellbore underreaming tool or apparatus, which is particularly applicable in oil and natural gas wells, arranged for attachment to a rotary drill-bit and associated drill-pipe, which comprises at least one radially extendable cutter block ( 62 ), at least one positional sensor ( 76  or  64 - 66 ) to determine the wellbore diameter, to verify and control a desired underreamer diameter ( 22 ). 
         [0030]    The positional sensor may be dynamic and the tool support may be the drill string but it may also be a length of coiled tubing. 
         [0031]    The tool body is a cylindrical high grade steel housing adapted to form part of the bottom-hole assembly by means of a screw connection arranged at the end of the tool, which is coupled to the drill bit. The attachment need not be direct, but may be indirect, depending on the requirements of the different elements of each drill string and each well. The lower end of the BHA may be a drill bit, or a bull nose and/or an expandable bit and various components between the tool there may or may not be a means for directional control of the wellbore such as a rotary steerable system. 
         [0032]    In one embodiment of the invention, the expansion operation is an underreaming application, and expansion elements comprise a set of cutter blocks optimally configured with cutter inserts and nozzles. In another embodiment, the expansion elements may comprise expansion blocks, which may be of similar construction to the cutter blocks, but having outer surfaces where cutter elements may be replaced by a hardened material. Such expansion blocks may simply bear under pressure against the inside of a tubular wall, with sufficient force to deform it outwardly to a larger diameter. In yet another embodiment, the same blocks may simply bear against the underreamed wellbore in order to stabilize the tool within the wellbore without enlarging the bore. The same blocks maybe received within an additional section of the tool or a separate steel body suitably prepared to provide a means of stabilization to the expansion operation. In a further embodiment, the same blocks maybe received within an additional section of the tool or a separate steel body suitably prepared as apparatus to provide a means of stabilization for underreaming applications. 
         [0033]    In one embodiment where the wellbore expansion activity is underreaming the cutter blocks are situated within the tool body in an open chamber, the outer surface of which is composed of a plurality of high strength cutter elements such as polydiamondcrystalline inserts arranged externally. The cutter block is provided with a flow of drilling fluid via an external nozzle adjacent to the set of cutters which allows drilling fluid to flow from an internal bore connected to a source of said drilling fluid. 
         [0034]    In another embodiment, the tool comprises a module that can be coupled by means of a thread connection to the body of the tool which comprises expandable stabilizing blocks in order to stabilize the tool against the wellbore walls during underreaming and measurement and if so required, increase or expand the diameter of the metallic tube casing of the well. 
         [0035]    It is to be noted that the description herein of the expansion blocks is applicable generally, irrespective of the function of cutting, expansion or stabilization of the drill string. Thus, the cutter blocks are provided with cutting inserts or teeth to enable underreaming of the wellbore that may be replaced by hardened smooth surfaces for expansion operations of an expandable steel tubular inside the wellbore. 
         [0036]    In yet another embodiment the microprocessor control means ( 68 ) are adapted to receive, during drilling operations, information from the positional sensors of the extendable cutter block in order to control the extension and retraction of said block in order to detect and correct failures in real-time and achieve the desired wellbore diameter. 
         [0037]    The tool normally comprises a plurality of such cutter blocks, arranged symmetrically around the tool. Two cutter blocks would be on opposite sides of the tool, three blocks would be separated by 120 degrees, four blocks by ninety degrees, and six by sixty degrees. Or the blocks may simply be housed in separate housings allowing for a plurality of cutter blocks. In operation, the tool is typically rotated together with the drill string as well as being moved axially along the wellbore. 
         [0038]    The tool body is provided with an internal bore for receiving drilling fluid via a device nozzle adjacent the cutter. In each case, the nozzles provide a fluid flow that help to keep the cutters clean and prevent the build-up of clogging debris from the underreaming operation and provide a cooling and lubricating function for the cutters. In one embodiment of the present invention the tool incorporates a non-mechanical means of reamer position measurement or reamer diameters such as a pressure measurement. Suitable means for pressure measurements are pulse heads or flow restrictors such as castellations, turbines or valve plates which can reciprocate or rotate or vibrate to create a dynamic pressure signal or a plurality of pressure signals. The pulse head or flow restrictor may be connected to a mandrel or travelling lock or sleeve thereby the displacement related to the movement of the extendable blocks outward. Other restrictors may be graduated and allow for reduced turbulent flow with less chance of erosion. In either case treatments such as tungsten carbide, HVOF etc may be applied. 
         [0039]    In yet another embodiment a bending moment sensor may detect bending moments on the tool allowing for activation forces to be optimized by increasing or decreasing activation forces. The bending moment sensor may show that further activation force is required or lower force or that parameters should be changed such as the angle, rop, WOB, FLOW, directional control system blades. Optimal configurations of the invention are envisaged based on application needs. 
         [0040]    A pulse head may travel through a number of rings and thus create a number of pulses related to position. For example, 1 pulse may be deactivated, 2 pulses 1 inch extended, 3 pulses 2 inches extended and so on. Additionally or alternatively the reverse is also possible as is a further embodiment wherein the duration of the pulse may indicate positional data. For example, a long pulse indicates activation while a short pulse is deactivated or the alternate is possible. Further pulse encoding may be planned dependent on the type of frequency and duration and other pulsers that may be in the hole as is the case when directional or LWD/MWD companies are providing such measurements. 
         [0041]    The positional sensing means are generally located in the tool or cutter block or mandrel in a chamber but in an alternative configuration of the tool may be placed within the cutter block itself in the most radially extended zone among the cutting elements or linked to a nozzle opening to the wellbore. Other embodiments are for example, a pressure sensor may detect chamber pressure. Additionally or alternatively the sensing means may be located below a sealed area or within a seal area. 
         [0042]    In one embodiment, the invention provides for a method of operating an expansion tool or apparatus to underream a borehole to a desired dimension below a restriction, which comprises locating said tool or apparatus in said borehole on drill-pipe below a restriction, extending a set of cutter blocks to an expansion diameter greater than the restriction, rotating the tool and moving it axially along the borehole on the drill string or other support, sensing the block position by detection means and continuing underreaming until the desired dimension is achieved. 
         [0043]    In accordance with yet another method of the invention, the tool may be provided with expandable cutter control means responsive to dimension data received from positional sensors or caliper means. In this way, an integrated tool and apparatus which is capable of diagnosing under-performance and correcting it may be realized. The dimension data may prompt for tests and checks on the effective deployment of the expandable blocks, may trigger a repeated cycle of expansion, or activate a further set of cutters and may provide data to a surface monitor to signal an opportunity for operator intervention. 
         [0044]    The processor uses this data to correlate whether the pre-programmed wellbore diameter is actually being underreamed via block position sensing. Where the processor detects a fault or difference between the two minimum measurements it automatically troubleshoots the fault using a logical procedure. 
         [0045]    The skilled operator will readily appreciate that other procedures may be implemented by the logic circuit or control program within the tool&#39;s processors, which can be programmed to cover other scenarios. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0046]    The various embodiments of the invention are illustrated by way of non-limiting examples in the accompanying drawings, in which: 
           [0047]      FIG. 1  is a general diagrammatic view of an oil or gas well showing surface structures and the interior of the underground wellbore, with a tool in accordance with the invention as part of the final bottomhole assembly; 
           [0048]      FIG. 2  is a longitudinal section of the tool and apparatus according to one embodiment showing the expansion elements constituted by cutter blocks;  FIGS. 2   a  and  2   b  show the tool of  FIG. 2  activated and deactivated respectively and further configured with a calliper and mud pulser. 
           [0049]      FIG. 2A  and  FIG. 2B  respectively show configuration with calliper ( 58 ) and cutters ( 62 ) activated and deactivated. 
           [0050]      FIG. 3  is a cross section of the tool as seen from the drill bit, showing the diameters of the drill bit, of the pass-through casing and of the desired underreaming of the wellbore in accordance with the invention shown in the previous Figures, in the operative mode of the expanded expansion cutter blocks (activated operating mode); 
           [0051]      FIG. 4  shows a cross-section of the tool as seen from the drill bit, showing the diameters of the drill bit, of the casing and of the desired underreaming of the wellbore, according to the invention shown in earlier figures in the operative mode of the retracted expansion cutter blocks (deactivated operating mode); 
           [0052]      FIG. 5  is a general view of the well illustrating telemetry of the underreaming and drilling data recorded by the tool or apparatus; 
           [0053]      FIG. 6  corresponds to  FIG. 5  but illustrates downlink telemetry of the data with parameters sent in order to control the underreaming and drilling by the tool or apparatus; and 
           [0054]      FIG. 7  shows an embodiment of an expansion block configured with cutters; 
           [0055]      FIG. 8  is a view corresponding to  FIG. 7  showing an alternative construction with external nozzle; 
           [0056]      FIG. 9  is a longitudinal section of one embodiment of the tool or apparatus showing the expansion elements constituted by a set of cutter blocks and a further set of cutter blocks in a deactivated state. Equally the first or second set may be replaceable with an expandable bit. 
           [0057]      FIG. 10  is longitudinal section of an expandable stabilizer with a dynamic positional detector means contained therein and with cutter blocks in a further module. 
           [0058]      FIG. 11  shows a longitudinal section showing two locations for positional detector means above and below a mud pulser 
           [0059]      FIGS. 12 and 13  show a detail of a dynamic position detector with and without a pulse head of one embodiment of the tool or apparatus showing the expansion elements constituted by a set of cutter blocks and a further expandable bit replacing the second set of cutter blocks. 
           [0060]      FIGS. 14 and 15  detail a preferred embodiment with two locations for dynamic position detection contained within and partly without respectively of expandable cutter assembly. 
           [0061]      FIGS. 16 ,  17  show different configurations of a dynamic pulse head for position detection with a spring and compression/expansion chamber. 
           [0062]      FIG. 18  shows where the pulse head is connected to a mandrel which moves up or down the housing. 
           [0063]      FIG. 19  shows an embodiment wherein the blocks are connected to a single chamber 
           [0064]      FIG. 20  shows an embodiment where the dynamic position detector is placed in a fluid pathway to the annular. 
           [0065]      FIG. 21  shows yet another embodiment leading drilling fluid from a through passage ( 90 ) to an oscillating pulser. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0066]    As shown in  FIG. 1 , an exploration or production rig comprises a surface structure ( 10 ) at the wellhead, a wellbore ( 20 ), a drill string ( 30 ) in the wellbore and a bottom-hole assembly ( 40 ) at its lower end where the tool or apparatus ( 50 ) may be configured according to the present invention. 
         [0067]    The tool or apparatus ( 50 ) comprises at least one underreamer module integrated with a sensing means for reamer position detection or reamer diameter signal, and capable of connection to a drill-bit. 
         [0068]    Further embodiments can be configured as desired adding or removing modules: module housing the expandable cutter blocks and positional sensors, module housing the positional sensors, callipers, sensors and processors and the module with expandable stabilizer blocks or expandable blocks to expand a tubular within the wellbore. 
         [0069]    The signal or position is detected according to the position so that for a 12¼″-14¾″ tool it could be configurable and extended to a plurality of radial positions between 12¼″ and 14¾″. Generally such reamer positions are dependent on the pass through ID of casing and are expressed as increase in diameter relative to the bit size or reamer body size. Accordingly such expressions are generally in the order of 1″, 1.25″, 1.375″, 1.5″, 1.875″, 2.5″, 2.75″, 3″, 3.5″, 3.875″ and 4″ and so on. Other sizes are in the order of 0.5″, 0.75″ and so on. 
         [0070]    Alternatively or additionally the reamer body size or pass through dimension can be used to denote the expandable ratio or configured expandable reamer positions. Generally denoted in a such a manner these would be expressed in the order of 12.25″-14.75″, 14.75″-17″, 16.5″-19.5″, 18.125″-21″, 18.125″×22″, 16.5″×20″, 14.5″×16.5″, 12.25″×14.75″, 10.625″×12.25″, 8.5″-9.875″, 9.25″ to 10″, 11.25″ to 12.25″, and so on. 
         [0071]    The longitudinal section of the tool illustrated in  FIG. 2  comprises a steel tool body with connection ( 82 ) provided with an internal flowbore and if required a wellbore diameter measurement caliper ( 76  or  64 - 66 ) with the cutter blocks ( 62 ). The expandable cutter ( 60 ) is composed of various cutter blocks ( 62 ) placed symmetrically and radially outwards of the tool body ( 52 ) as shown in  FIG. 2  in the activated status with the blocks extended outside the tool. 
         [0072]    In one embodiment the tool may incorporate an acoustic caliper comprising an acoustic transmitter and receiver which can be housed within the body of the tool in sealed recesses ( 64  and  66  or  76 ). Tool performance is verified using the micro-processor ( 68 ) that compares data recorded by the acoustic receiver ( 66  or  76 ) with the programmed wellbore diameter, thus detecting possible undergauge hole diameters. The tool is automated according to logic control sequences stored in each processor ( 68 ) to deliver a desired wellbore diameter and in order to ensure the underreamer is functioning correctly. Once verification and corrective steps have been taken, and if the caliper for measuring the underreamed wellbore diameter ( 66  or  76 ) indicates that the required hole diameter is still not being delivered, a signal is sent via the mud-pulser ( 56 ) to the rig-surface ( 10 ) to allow control commands to be sent by the operator either locally or by remote control. These control commands adopt the relevant operative and corrective measures such as modification of the pump flow rate of mud or drilling fluid, activation of cutter blocks in response to caliper data, replacement of the bottom-hole assembly etc. The memory card associated with the processor ( 68 ) stores data from the calipers, fluid properties measurement sensors. The said data is transmitted in real time in order to be used in the underreaming and drilling operations ( 56 ) or physically downloaded by removing said card when the tool is retrieved from the well. 
         [0073]      FIGS. 2   a  and  2   b  activated and deactivated respectively show how the tool is provided with a built-in link to the telemetry system ( 56 ) which also serves to monitor performance of the under-reaming operation, position of expansion blocks ( 62 ) and data recorded by the caliper for measuring the underreamed wellbore diameter ( 66  or  76 ). One or more acoustic sensors ( 64  or  76 ) are placed within the tool body ( 52 ) in order to emit a number of sound waves during a given time period which are reflected back by the wellbore wall and picked up by the receiver sensors ( 66  or  76 ). In a further embodiment the processor ( 68 ) calculates the distance using transit time and calibrates transit time with data from further fluid properties sensors to establish the speed of return of the acoustic waves and wellbore diameter. The processor compares the measured wellbore diameter to the programmed desired diameter. If the two measurements match given user-defined tolerances the tool continues to operate to the total depth of the wellbore section to be underreamed. Where the measurements do not match the processor automatically activates a series of logic steps to troubleshoot the fault. 
         [0074]    As further shown in  FIG. 2 , a keyway ( 78 ) provides a channel for wiring of the acoustic pulsers or transmitters ( 64  or  76 ) and the acoustic sensor/receivers ( 66  or  76 ) to the processor ( 68 ), and also to the transponder ( 72 ). The wiring can be used to transmit as much or as little data required by the configuration of the tool. For example, this may include acoustic data retrieved by wellbore calipers and fluid properties sensors as well as positional data from the cutter and stabilizer blocks to the processors and transponders. The keyway may be sealed and filled with a means to absorb vibration such as silicone gel. 
         [0075]      FIG. 2  shows a processor ( 68 ) which provides data for transmission to surface ( 10 ) via the mud-pulser ( 56 )  FIGS. 2   a  and  2   b  which transmits the data to surface using a series of binary codes at a given frequency using the drilling mud itself as means of transmission. Other means of wireless data transfer may be used such as systems using radio frequency or electro-magnetic pulses. 
         [0076]      FIG. 2  also shows an alternative location for the caliper for measuring the underreamed diameter which may be a caliper ( 76 ) arranged in an encapsulated recess connected to wiring in keyway ( 74 ) connected to the processor which may also be connected to the acoustic (transmitter/receiver) calipers ( 66 - 64 ) and a new keyway connection ( 78 ) which may be connected to an alternate processor ( 68 ) for the expandable block ( 62  or  63 ).  FIG. 1  also shows an internal flow bore or axial through passage ( 90 ) in the tool to allow mud to flow through the whole bottom-hole assembly ( 40 ). The encapsulated recesses ( 64 ,  66  and  76 ) may also be used to house other types of sensors such as a vibration sensor to detect stick-slip conditions. 
         [0077]      FIG. 3  shows an uphole front view of the bit illustrating the generally designated expandable cutters ( 60 ) in the activated mode, i.e. with cutter blocks ( 62 ) expanded outwardly of the tool body and supported against the underreamed wellbore wall ( 22 ) which arises from the wellbore ( 20 ) which has not been underreamed.  FIG. 3  shows the arrangement of the drill bit teeth in which there are ten curved rows of cutters ( 44 ), with cutter teeth in each one. A central drilling fluid outlet ( 46 ) indicates where drilling fluid passes through the internal flowbore ( 90 ) in the tool body ( 52 ). The direction of rotation of the bottom-hole assembly and of the drill bit is shown ( 124 ). 
         [0078]      FIG. 4  illustrates the same front view as  FIG. 3  with the expandable cutters ( 60 ) in a deactivated condition, i.e. with cutter blocks ( 62 ) retracted within the inner chambers of the tool body without exceeding the wellbore diameter that has not been underreamed ( 20 ). 
         [0079]    In a further embodiment of the invention, each expandable block is provided with lines, strips, contacts or sensors to detect the actual position of the blocks. The signal is measured according to the position so that for a 12¾″-14¾″ tool it could be extended to a plurality of radial positions between 12¾″ and 14¾″. Each radial position is capable of being determined and sensed. In this way, it can be seen whether the block has actually been extended and determine its extension length and position. This block positional data is sent to the processor where it is stored, compared and correlated with the caliper data or data from vibration, rpm, pressure, hydraulic force, torque, flow sensors to deliver a desired wellbore diameter and also troubleshoot causes of failures. It is not necessary for the block positional sensor to be on the block. In an alternate embodiment the sensor may be on the housing. In yet a further embodiment the sensor may be on another tool or may be at surface applicable as the purpose is to establish the relative position of the block to the tool. Additionally or alternatively, pressure or flow may be used to lock the radial position and equally pressure or flow signals may be used to sense or indicate the block position. Additionally or alternatively it is not always necessary that a sensor physically measures each radial position as the groove location serves the same purpose. 
         [0080]    As noted above, the invention provides a method of real-time drilling operation and control, which uses an extendable tool to underream the borehole to the desired dimension passing through a restriction, activating the tool, extending the extendable cutter block to a diameter greater than that of the restriction, and locating the extendable block in a predetermined position, rotating the tool and moving it axially along the borehole, enabling the simultaneous measurement and calibration of the borehole diameter by the caliper for measuring the underreamed wellbore diameter. Microprocessors connected to a control area act in response to data received from the caliper for measuring the underreamed wellbore diameter, the fluid properties or the parameters such as pressure, torque, flow with the objective of achieving the desired wellbore diameter and eliminate causes of errors or failures and minimizing drilling time by not tripping in with another caliper or performing further underreaming corrective runs. 
         [0081]      FIGS. 5 and 6  illustrate how the underreaming tool may utilize means for communicating data from the tool such as dynamic positions, calliper for measuring the underreamed wellbore diameter, the calibration fluid properties sensors, the block positional sensors or the vibration sensors and control signals between the tool and a surface interface which may, among other functions, control the advance and trajectory of drilling during the underreaming operation. 
         [0082]    As shown in  FIGS. 5 and 6 , the wellhead surface structure ( 10 ) includes a control and communications system ( 12 ) having an interface for telemetry with downhole instrumentation including a data processor or data logger ( 14 ) and a controller ( 15 ) which decodes binary codes from the mud pulser and may be linked directly to the user&#39;s drilling terminal ( 16 ). The decoded data may be yet further transmitted by satellite ( 17 ) beyond the wellhead to a remote operations centre ( 18 ) where another user of the drilling software may access the data and the control by means of a telecommunication link ( 19 ). 
         [0083]    The tool may be provided with a mud pulser as a standalone tool or the mud pulser and associated measurements may be provided by a third party as would be the case when a measurement while drilling or logging while drilling suite of tools is located in the BHA. The hard wiring and processor may be configured to make use of these measurements or they be sent to surface where a user may make further use of them. 
         [0084]    The apparatus may be directly or indirectly connected to other components in the drilling or bottom hole assembly. 
         [0085]      FIGS. 7 and 8  show variations in block and according to these embodiments of the invention, each block is provided with lines, strips, contacts or sensors that permit the processor to detect the actual position of the blocks. The signals can be configured so that they are strongest when the block is fully extended or strongest when the block is fully retracted or a signal may simply correspond to a radial position. In this way, it can be seen whether the block has actually been extended and determine its extension length and position. This data is sent to the processor where it is stored and processed. 
         [0086]    Additionally or alternatively to digital or electronic sensing the positional signal may be generated via analogue mechanisms. Therefore, sensing means can be any suitable type of sensor or detector or indicator such as contacts, electrical sensors, strips, resistive wipers, rheostats, circuit breakers, proximity sensors, distance sensors, volumetric sensors, volumetric measurements, valves, induction loops, spirals, coils, wireless and wired. Others maybe grooves, lines, piston valves, channels, strips, mechanical, pressure or force related. Further a combination of both mechanical and electrical sensing mechanisms can be used to detect the position of the block. 
         [0087]    The sensing means may also serve a number of functions so a strip may also form part of a seal or serve as a seal so isolating the block or housing from pressure. Or a pressure sensor may be used to detect the position of the cutter block. Further the signal may be defined as a direct or inferred or indicative position. The signal or a lack of a signal may also be provided to show a status such as a series of pressure signals according to a series of variable cutter positions. 
         [0088]    The positional data plus the vibration data provides novel data which determines vibration as per the underreamer status i.e. activated/deactivated or in an intermediate or variable gauge position. 
         [0089]    The underreamer status is generally performed by a position sensing means which can be a position sensor. Additionally or alternatively such sensors can be on the block or housing ( 96 ,  94 ) to determine the actual position of blocks ( 63 , 62 ) and send corresponding signals back to the surface or processor ( 68 ). Suitable sensor means include any type of known of sensor or detector for position, respectively on the cutter block and housing or alternately on solely located on the cutter block or the housing itself. Additionally or alternatively the block sensing means may be on another tool or located at surface. Additionally or alternatively pressure or flow indicators based on the location of the block in the predetermined groove or location may also be used to sense or detect or indicate or infer the position of the blocks. Variations in sensors or signals may be electrical, mechanical or a combination of both. It is not essential that physical sensors measure the distance in this embodiment because the radial positions may be pre-determined by grooves and unlike the prior art which is only extended or retracted in the present invention there may be a plurality of known positions according to grooves. The term groove is used broadly and generally but serves to describe a locatable position for the cutter block. Other terms may be channels, positions, locators etc. The importance of the locatable position is to provide a variable gauge underreamer capable of being positioned in at least three positions such as open, closed and intermediate. Additionally or alternatively a further embodiment would be activated or extended, retracted or deactivated and an intermediate position in between the former two. 
         [0090]    In another embodiment the block position sensing is not performed on the block or housing but can be performed on another tool or performed at surface. 
         [0091]    As shown in  FIG. 9  the illustrated example is of an embodiment of the tool sharing common features which is at least two sets of expandable blocks and an underreamer that uses a microprocessor ( 68 ) and electronic means to determine and control block position. 
         [0092]    In one embodiment the position sensing function is performed by a sensor on the block or housing. The position of the underreamer is designated by sensing means in a general and broad way and can clearly use any type of position detectors, position indicators, position signals, position measurements. Such position sensing means can be analogue or digital, inferred, observed, or direct with the importance being a comparative data set relating to the underreamer status. Therefore, it is not essential that the position sensing means is contained within the underreamer as it may be contained within other downhole tools and additionally or alternatively at the surface. 
         [0093]    The tool or apparatus may be configured with any number of modules integrated by means of screw connections ( 65 ) and ( 82 ). The body of all parts of the tool or apparatus ( 52 ) is a cylindrical high grade steel housing adapted to form part of the bottom-hole assembly (BHA) ( 40 ) via internal screw connections to ensure the through flow of drilling fluid ( 90 ). The connection may be direct or indirect depending on the needs of the different drilling components of each BHA and each well. At the leading downhole end of the BHA there may be a drill-bit or a stabilizer and between this point and the tool there may be a wellbore directional control system. 
         [0094]    As shown in  FIG. 10 , dynamic position sensor means comprising a pulse head ( 950 ) and a spring ( 960 ) provide for pressure signals detected at surface or downhole.  FIG. 10  also shows the stabilizing blocks ( 63 ) are constructed identically to the cutter blocks ( 62 ), except that in place of cutter elements ( 60 ) there is a surface which is hard faced ( 61 ) or coated with a hard abrasion-resistant material. 
         [0095]    The hard faced surfaces of the stabilizer expansion blocks act to stabilize the drill string and eliminate some of the problems associated with the loss of directional control above the underreamer when the diameter in said zone is equal to that of the underreamer or greater than the pilot hole. Likewise, the tool can be used to expand or enlarge the diameter of metal tubes by deformation of the latter in the wellbore. In this case, the tool body facilitates the operation of expanding or enlarging the diameter of the expandable casing and is connected to the downhole assembly by means of a screw connection in said body. 
         [0096]    The stabilizer module may be directly or indirectly connected to the underreamer and hard-wired accordingly ( 74   a ) to send data from the processor ( 68 ) to the transponder ( 72 ) through the mud-pulser ( 56 ) to surface. 
         [0097]    It is to be noted that the following description of the cutter means is equally applicable to the structure and function of the stabilizer and expansion means in the uphole section ( 61 ) of the tool, with due allowance for the absence of cutter elements ( 92 ). 
         [0098]    A set of cutters comprises at least one cutter block ( 62 ) carrying a plurality of cutter elements ( 92 ) directed outwardly of the tool body ( 52 ). The cutter block is received within the tool body in a cutter block chamber ( 94 ) having an open mouth, and the cutter is extendable from the chamber through the chamber mouth with the cutter elements projecting from the tool body, and retractable back into the chamber. A seal ( 104 ) is provided around the cutter block at the mouth of the receiving chamber ( 94 ). 
         [0099]    As noted above, in one embodiment the tool is provided with means for extending and retracting the cutter block from and into the cutter block chamber, such means may comprise a power mechanism ( 84 ) in the tool body in engagement with driven teeth ( 86 ) on the cutter block. Motor means ( 80 ) are provided for extending and retracting the cutter block, and microprocessor control means for the motor means are both mounted within the tool body. The microprocessor control means is suitably adapted to receive bore dimension information from the caliper means ( 66 ) and to control the cutter block extension in response thereto. A mechanical lock is provided by means of a locking collet finger ( 96 ), which can be located into one of a plurality of retaining lip grooves ( 98 ) by travelling lock ( 100 ), which is located by sealing collar ( 102 ). The tool may be activated by means of electronic signal sent by mud-pulse and decoded or by other means using fiber-optics or wireless transmission. 
         [0100]    Hydraulic locking means may be provided to resist retraction of the extended cutter block ( 62 ) into the cutter block chamber ( 94 ) when the extension of the cutter block is opposed by external pressure. This may comprise a port (not shown) open to a source of drilling fluid (passage  90 ) onto the travelling lock ( 100 ) immediately behind the cutter block. 
         [0101]    The tool normally comprises a plurality of such cutter blocks ( 62 ), arranged symmetrically around the tool. Two cutter blocks are on opposite sides of the tool, three blocks are separated by 120 degrees, four by 90 degrees, and six by 60 degrees. Additionally, a plurality of such cutter blocks are arranged at longitudinally separated positions so as to provide for a plurality of cutter block housings further detailed in  FIG. 11 . In operation, the underreaming tool ( 50 ) is typically rotated on the drill string as well as being moved axially along the wellbore. 
         [0102]    In accordance with an embodiment of the invention, shown in  FIG. 9 , the cutter block is provided with an internal flowbore ( 110 ) leading drilling fluid from a through passage ( 90 ) to an external nozzle ( 112 ) among the cutter elements ( 92 ). The source of drilling fluid may be the rig pumps via the drill-string ( 30 ) to the passage ( 90 ) for the flow of drilling fluid from the drill string to the drill bit. In another embodiment, as shown in  FIG. 10 , the tool body may be provided with an internal flowbore ( 114 ) leading drilling fluid from passage ( 90 ) to an external nozzle ( 116 ) adjacent the set of cutters. In each embodiment, the nozzle provides an optimized fluid flow that can help to keep the cutters clean and prevent the build-up of clogging debris from the underreaming operation, remove such material altogether from the underreaming zone, and provide a cooling and lubricating function for the cutters. 
         [0103]    In yet another embodiment  FIG. 10  shows an additional or alternate component a translatable mandrel or axial sleeve with position sensing ( 910 ) which may also have a profile or groove to engage expandable blocks ( 62 ) to act as a seal or lock or simply to engage expandable blocks and move them radially or laterally outward and also shows additional or alternate component  115  which can be an expandable bit configured with or without reaming capability to reduce downtime and uncertainty. 
         [0104]    In yet another embodiment of  FIG. 10  corresponding to certain components of  FIGS. 8 and 9 , sealing collar  102  may be used to house further sensors or the sensors  96   a ,  98   a  may be used to detect the position of the mandrel. 
         [0105]      FIG. 11  shows a further embodiment of the tool wherein a dynamic positional indicator is placed additionally or alternatively in a separate module to the set of cutters shown at the downhole end and a further set of stabilizers are shown at the uphole end, both sets suitably housed in modules. Such an embodiment comprises more than one set of expandable cutter blocks ( 62  and  62 ) integrated within independent modules that are screwed to each other in order to reduce drilling downtime. 
         [0106]      FIGS. 12 and 13  show a detail of a dynamic position detector with and without a pulse head of one embodiment of the tool or apparatus showing the expansion elements constituted by a set of cutter blocks and a further expandable bit replacing the second set of cutter blocks. The signal or position is detected according to the position so that for a 14¾″-17½″ tool it could be configurable and extended to radial positions between 12¼″ and 14¾″. Generally such reamer positions are dependent on the pass through ID of casing and are expressed as increase in diameter relative to the bit size or reamer body size. Accordingly such expressions are generally in the order of 1″, 1.25″, 1.375″, 1.5″, 1.875″, 2.5″, 2.75″, 3″, 3.5″, 3.875″ and 4″ and so on. Other sizes are in the order of 0.5″, 0.75″ and so on. 
         [0107]      FIGS. 14 and 15  detail a preferred embodiment with two locations for dynamic position detection contained within and partly without respectively of expandable cutter assembly. 
         [0108]      FIGS. 16 ,  17  show different configurations of a dynamic pulse head ( 950 ) for position detection with a spring ( 960 ) and compression/expansion chamber ( 980 ) with valve or pressure sensor ( 990 ). Additionally or alternatively, pressure or flow may be used to move the pulse head and thus create a series of clear and detectable pressure or flow signals corresponding to radial positions which are used to sense or indicate the block position. 
         [0109]    In yet another embodiment a bending moment sensor may detect bending moments on the tool allowing for activation forces to be optimized by increasing or decreasing activation forces. The bending moment sensor may show that further activation force is required or lower force or that parameters should be changed such as the angle, rop, WOB, FLOW, directional control system blades. Optimal configurations of the invention are envisaged based on application needs. 
         [0110]    A pulse head may travel through a number of rings and thus create a number of pulses related to position. For example, 1 pulse may be deactivated, 2 pulses 1 inch extended, 3 pulses 2 inches extended and so on. 
         [0111]    Additionally or alternatively the reverse is also possible as is a further embodiment wherein the duration of the pulse may indicate positional data. For example, a long pulse indicates activation while a short pulse is deactivated or the alternate is possible. Further pulse encoding may be planned dependent on the type of frequency and duration and other pulsers that may be in the hole as is the case when directional or LWD/MWD companies are providing such measurements. 
         [0112]    A series of pulses configurable by the user may be advantageous in detection and can be configurable to avoid interference with other signals in the mud column. Additionally or alternatively the interference may be electronic in which case means are provided to avoid such interference. Such means can be based on shielding, noise cancellation, circuitry configuration or component selection, frequency modulation, amplitude modulation, carrier waves, electro magnetic, sonic, etc. 
         [0113]      FIG. 18  shows where the pulse head is connected to a mandrel which moves up or down the housing ( 975 ) which may if required be further contained within the body of the tool. In yet another embodiment of  FIG. 18 , the mandrel may have a profile to engage with the expandable block, or a profile to engage with body or may simply engage with the expandable block. 
         [0114]      FIG. 19  shows an embodiment wherein the blocks are connected to a chamber and dynamic position indicator ( 910 ) and further additional or alternate position sensing means located as ( 98 ) and ( 96 ) in relation to ( 910 ). The positional sensing means are generally located in the tool or cutter block or mandrel in a chamber but in an alternative configuration of the tool may be placed within the cutter block itself in the most radially extended zone among the cutting elements or linked to a nozzle opening to the wellbore. Other embodiments are for example, a pressure sensor may detect chamber pressure. Additionally or alternatively the sensing means may be located below a sealed area or within a seal area. 
         [0115]    As shown in  FIG. 20  and yet another embodiment leading drilling fluid from a through passage ( 90 ) to an external flow path ( 970 ) wherein a pulse head ( 950 ) may be driven by a solenoid or motor powered. The source of drilling fluid may be the rig pumps via the drill-string ( 30 ) to the passage ( 90 ) for the flow of drilling fluid from the drill string to the drill bit. 
         [0116]    As shown in  FIG. 21  and yet another embodiment leading drilling fluid from a through passage ( 90 ) to an oscillating pulser ( 990 ) wherein one or more discs ( 991 ) may be driven by fluid flow, a solenoid or motor powered to dynamically create pressure pulses to detect, monitor or indicate radial or longitudinal positional status. The discs may be open, close, partially open or closed and configured to operate at the desired flow, rpm or oscillation with the objective of providing positional indication. The source of drilling fluid may be the rig pumps via the drill-string ( 30 ) to the passage ( 90 ) for the flow of drilling fluid from the drill string to the drill bit. 
         [0117]    Those skilled in the art will appreciate that the examples of the invention given by the specific illustrated and described embodiments show a novel underreaming tool and apparatus integrated with a caliper and accompanied by a method for underreaming verification and measuring underreamed wellbore diameter measurements using calibrated downhole fluid property measurements for accurate wellbore diameter measurements. A further embodiment includes a sensor for measuring the position of extendable blocks. While a further embodiment incorporates a vibration measurement sensor. Consequently, numerous variations are possible to achieve the purpose of the invention which is to improve drilling efficiency and provide certainty whenever a desired underreamed wellbore diameter is required. These embodiments are not intended to be limiting with respect to the scope of the invention. Substitutions, alterations and modifications not limited to the variations suggested herein may be made to the disclosed embodiments while remaining within the purpose and scope of the invention.