Adjustable Cutting Mill Assembly and Methods of Operation

Abstract

A system and method for adjusting or controlling at least one milling operating feature of a cutting mill assembly within a wellbore includes sensing at least one milling operating parameter with a sensor that is operably associated with the cutting mill assembly that is run into the wellbore. At least one milling operating feature of the cutting mill assembly is adjusted or controlled in response to the at least one milling operating parameter that is sensed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to downhole cutting mills and methods for operation of such cutting mills.

2. Description of the Related Art

Milling tools, or mills, are used to perform cutting tasks within a subterranean wellbore. As opposed to drill bits, which tunnel through the earth, mills are often employed to cut away discrete objects within or associated with a wellbore. For example, a cutting mill is used to cut through a plug or other obstruction which is located within the bore of a well. A casing exit mill is used to cut a window in metallic wellbore casing.

SUMMARY OF THE INVENTION

The present invention relates to cutting mill assemblies which are adjustable in at least one of several ways to alter the cutting ability or nature of the cutting mill during operation. The invention features methods for operating a cutting mill assembly wherein one or more milling operating parameters are sensed or measured and, in response, a milling operating feature associated with the cutting mill or its operation is adjusted.

Exemplary milling operating parameters which can be sensed include torque experienced by the milling bottom hole assembly, weight-on-bit, flow rate at surface, flow rate proximate the bottom hole assembly, temperature, pressure and vibration. In preferred embodiments, suitable sensors are provided within the cutting mill assembly to detect and measure these milling operating parameters and to provide generated signals indicative of each.

In described embodiments, the milling operating features which are adjusted include movement of, including the amount of protrusion of, a cutter from the cutting mill body, diameter of the cutting mill body and fluid flow through a nozzle on the cutting mill body. Other adjustable milling operating features include vibration imparted to the cutting mill bottom hole assembly and the rate of fluid flow provided to the cutting mill bottom hole assembly.

In described embodiments, a controller is provided which is capable of receiving signals representative of the sensed milling operating parameters as well as providing control commands to adjust a milling operating feature. In certain embodiments, the controller senses one or more milling parameters and adjusts one or more milling operating features autonomously.

In described embodiments, an adjustable cutting mill features a mill body with a plurality of cutters, at least one or more of which are moveable with respect to the mill body. Movement of the one or more cutters is a milling operating feature which can be adjusted in response to sensed milling parameters. The one or more cutters are adjustable by movement to cause the cutter(s) to protrude outwardly from the mill body to a greater extent or lesser extent. In described embodiments, mechanisms are provided for moving the cutters with respect to the mill body. In preferred embodiments, the cutters can be remotely adjusted with respect to the mill body. In still other embodiments, the cutter(s) are autonomously adjusted with respect to the mill body by a controller based upon sensed downhole and/or uphole milling operating parameters.

In certain embodiments, an adjustable cutting mill is provided which includes a mill body having an adjustable diameter. In particular, wedge portions of the mill body can be moved to alter the diameter of the mill body. The diameter of the mill body is a milling operating feature which can be adjusted in response to sensed milling parameters. The diameter of the mill body might be reduced in response to detection of sensed milling parameters which indicate a restriction in the wellbore and wherein reduction of the mill body diameter would permit the mill body to pass through the restriction.

In other aspects, the cutting mill assembly includes nozzles or flow ports that are adjustable in flow area. Flow area can be adjusted to allow greater flow of fluid or lesser flow of fluid. This would also affect the pressure at which fluid exits the nozzle or flow port. Nozzle flow area is also a milling operating feature which can be adjusted or controlled in response to one or more sensed milling operating parameters.

In certain embodiments, the cutting mill assembly includes an extended reach tool which imparts vibration to the tool string to improve cutting ability at desired depth of the well. In described embodiments, the extended reach tool is operably associated with the controller so that vibrational energy can be created by the extended reach tool to increase the cutting effectiveness of the milling bottom hole assembly. Vibration created by the extended reach tool is a milling operating feature which can be adjusted or controlled in response to sensed milling operating parameters.

In described embodiments, the cutting mill assembly includes a circulation tool that includes lateral ports which can be opened to adjust fluid flow to the milling bottom hole assembly. Fluid flow to the milling bottom hole assembly is a milling operating feature which can be adjusted in response to sensed milling operating parameters.

In particular embodiments, a cutting mill assembly is provided which includes an adjustable cutting mill which is carried by a bottom hole assembly having a sensing and control unit. The sensing and control unit includes one or more sensors which are configured to detect one or more downhole milling parameters. In currently preferred embodiments, the downhole milling parameters include weight on bit (WOB), torque and temperature. Measured surface milling parameters include pump rate or fluid flow rate and surface weight of the entire cutting mill assembly.

The sensing and control unit preferably includes a controller which receives signals from the sensors which are representative of the one or more milling operating parameters and is configured to determine whether an adjustment of one or more milling operating features of the cutting mill assembly is desired. The controller is operably associated with the cutting mill assembly so that the controller can adjust one or more of these features to alter the milling operation. The controller is preferably a programmable processor with associated memory.

In a described embodiment, the bottom hole assembly of the cutting mill assembly includes a communications module which permits communication of data and commands between the downhole controller and the surface. The communication module will permit data representative of sensed milling operating parameters to be displayed to an operator at surface. An operator would be able to command the controller to control or adjust one or more milling operating features.

The invention provides methods for adjusting or controlling at least one milling operating feature of a cutting mill assembly within a wellbore. In accordance with described methods, one or more milling operating parameters are sensed and, in response, one or more milling operating features are adjusted or controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of an exemplary cutting mill assembly constructed in accordance with the present invention and disposed within a wellbore to mill away a plug.

FIG. 2 is a side view of an exemplary sensing and control module in accordance with the present invention.

FIG. 3 is a side, cross-sectional view of an exemplary milling bit having adjustable cutters.

FIG. 4 is a side, cross-sectional view of a portion of an exemplary milling bit having a nozzle with adjustable flow area.

FIG. 5 is a side view illustrating an exemplary milling bit having an adjustable diameter.

FIG. 5a is a side view of the milling bit of FIG. 5, now with the mill cutting diameter decreased.

FIG. 6 is a schematic view illustrating interconnection of a controller with a plurality of sensors for sensing milling operating parameters and a plurality of milling operating features.

FIG. 7 is a flow diagram depicting an exemplary process for adjusting cutting mill operation features in response to sensed milling operating parameters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an exemplary wellbore 10 which has been drilled into the earth 12 from surface 14. The wellbore 10 is lined with metallic casing 16, of a type known in the art. A plug 18 or other obstruction is present in the wellbore 10, and it is desired to remove the plug 18 by cutting it away.

A cutting mill assembly 20 is disposed within the wellbore 10, having been run in from the surface 14. The cutting mill assembly 20 is being used to cut away the plug 18. Generally, the cutting mill assembly 20 includes a running string 22 and a milling bottom hole assembly 24 which is carried by the running string 22. The running string 22 is typically coiled tubing. However, the running string 22 might also be composed of conventional drill pipe sections which are interconnected in end-to-end fashion, as is known in the art. A central flow bore 26 is defined within the running string 22 and permits flow of fluid, such as drilling mud through the running string 22 to the milling bottom hole assembly 24.

In preferred embodiments, the running string 22 incorporates an extended reach tool 28 and/or a circulation tool 30. The extended reach tool 28 may be an EasyReach Extended Reach Tool which is available commercially from Baker Hughes, a GE company, LLC of Houston, Tex. The extended reach tool 28 uses water hammer effect to generate traction forces which help to pull the running string 22 into the wellbore 10. The extended reach tool 28 is capable of imparting vibration to the milling bottom hole assembly 24, thereby increasing its rate of penetration and effectiveness.

The circulation tool 30 is a tool which enables mid-running string circulation from the flow bore 26 into the annulus 32, which is defined radially between the cutting mill assembly 22 and the casing 16. The circulation tool 30 generally includes a generally cylindrical housing 34 which defines a central flow passage 36 within. A plurality of lateral flow ports 38 are formed within the housing 34 permitting fluid flow between the annulus 32 and the flow passage 36. An interior sleeve 40 is retained with in the housing 34 and can be axially shifted within the body 34 selectively block or unblock the ports 38. The lateral flow ports 38 of the circulation tool 30 can therefore be opened, to reduce fluid flow to the milling bottom hole assembly 24 through the running string 22, or closed, to increase fluid flow to the milling bottom hole assembly 24 through the running string 22. The circulating tool 30 is preferably provided with a suitable solenoid valve (not shown) which is connected with a flow channel and will enable sleeve 40 to be shifted via fluid pressure so that the solenoid valve, under control of a controller, will open or close the flow ports 38.

A surface weight scale, of a type known in the art, is shown schematically at 42 in FIG. 1. Typically, the surface weight scale 42 is incorporated into the suspension and drawworks for the cutting mill assembly 20 and will measure the entire weight of the cutting mill assembly 20 when it is suspended within the wellbore 10. The measured weight is referred to as the weight measured at surface or the “surface weight.” The weight scale 42 generates an electronic signal which is indicative of the measured surface weight.

Now also referring to FIG. 3 as well as FIG. 1, the milling bottom hole assembly 24 includes a milling bit 44 having a mill body 46 and a plurality of hardened cutters 48 which are mounted thereupon. The mill body 46 also includes a plurality of nozzles 50 through which fluid, which is pumped from the surface 14 through the running string 22 will exit the mill body 46 during milling. The milling bit 44 is rotated by motor 52 during operation. The motor 52 may be a hydraulically-driven motor of a type known in the art. A fluid pump 54 is located at surface 14 and is operably associated with the running string 22 to flow drilling fluid through the running string 22. A flow meter 56 is operably associated with the fluid pump 54 in order to measure the pump rate or fluid flow rate of drilling fluid entering the running string 22.

It is noted that the milling tool which is being described is a cutting mill that is used to cut away a plug or obstruction within a wellbore. It should be understood, however, that other forms of milling tools can be used as well. For example, the milling tool could be a casing exit mill which is used to cut an opening within the wellbore casing 16.

The milling bottom hole assembly 24 also includes a sensing and control module 58, which is illustrated in greater detail in FIG. 2. The sensing and control module 58 includes at least one sensor 60 which is operable to detect at least one downhole milling operating parameter. In the depicted embodiment, there are multiple sensors 60 which are positioned on the outer surface 62 of the module housing 64 of the sensing and control module 58. Exemplary downhole milling operating parameters which are sensed include weight on bit (WOB), torque, pressure, temperature, vibration and flow rate of fluid received from the running string 22 proximate the milling bottom hole assembly 24. The sensing and control module 58 also includes a controller 66 which receives signals from the sensor(s) 60 which are indicative of the sensed downhole milling operating parameter(s). In addition, and as illustrated in FIG. 6, the controller 66 preferably receives signals indicative of fluid flow into the running string 22 from flow meter 56 at surface 14 as well as the cutting mill assembly 20 weight from weight scale 42 also at surface 14. Thus, the controller 66 receives signals representative of the downhole sensed milling operating parameters (from sensors 60) as well as uphole milling parameters (from flow meter 56 and scale 42).

The controller 66 may be in the form of one or more printed circuit boards which contain a programmable processor, data storage and the necessary computer programming to receive signals from the sensors 60 which are indicative of sensed downhole milling operating parameters and calculate desired adjustments for adjustable milling operating features. Data connections 68 transmit signals from the sensors 60 to the controller 66. As shown in FIG. 2, the sensing and control module 58 includes a central axial fluid flow path 70 which allows fluid pumped from surface 14 to be flowed to the milling bit 44.

The controller 66 is also operably interconnected with certain adjustable milling operating features of the cutting mill assembly 20 in order to control those milling operating features. Control line 72 extends from the controller 66 to the milling bit 44. The control line 72 carries actuation commands from the controller 66 to adjust the extension of mill bit cutters 48 or flow rate through nozzles 50, as will be described.

Referring once again to FIG. 3, an exemplary milling bit 44 is shown which has adjustable milling operating features. The depicted milling bit 44 is preferably an end mill or junk mill which is used to remove obstructions within a wellbore 10. Except where otherwise described, the milling bit 44 may be constructed and operate in the same manner as the Metal Muncher™ junk mill which is available commercially from Baker Hughes, a GE company, LLC of Houston, Tex. The bit body 46 of milling bit 44 includes a threaded connection 74 for attaching the milling bit 44 to neighboring components in the cutting mill bottom hole assembly 24. A central axial flow bore 76 extends through the bit body 46. The bit body 46 presents a lower cutting face 78 upon which cutters 48 are mounted. At least one of the cutters 48 are adjustable such that they can be extended or retracted from a recess 80 in the cutting face 78. In FIG. 3, only a single cutter 48 is illustrated as being adjustable in this manner. It should be understood, however, that multiple cutters 48 or even all of the cutters 48 may be adjustable. Fluid nozzle 50 is in fluid communication with the flow bore 76 so that fluid flowed through the flow bore 76 can exit through the cutting face 78 during operation.

The milling bit 44 includes an actuator, generally indicated at 82, for extending or retracting cutter 48 from recess 80. The actuator 82 includes a motorized fluid pump 84 which is operably interconnected with the control line 72 so that the pump 84 can be actuated by the controller 66. The actuator 82 also includes a piston chamber 86 which is in fluid communication with the pump 84. Piston 88 resides within the piston chamber 86 and is moveable within the chamber 86. Rod 90 secures the piston 88 to cutter 48. The actuator 82 can move the cutter 48 between a retracted position, wherein the cutter 48 is fully contained within the recess 80 and an alternate, extended position indicated at 48a. When the controller 66 commands the pump 84 to flow fluid to the chamber 86, the piston 88 is moved to the alternate, extended position 48a. When the controller 66 commands the pump 84 to flow fluid out of the chamber 86, the cutter 48 is returned to the retracted position within the recess 80. Other techniques and mechanisms for extending and retracting cutters are described in U.S. Pat. Publication No. 2015/0053551 which is owned by the applicant and is herein incorporated by reference in its entirety.

FIG. 4 schematically depicts a portion of a milling bit 44 is which fluid passageway 88 within bit body 46 transmits fluid from the central axial flow bore 76 to nozzle 50. The fluid passageway 88 includes a valve seat 90. Poppet valve member 92 is located within the fluid passageway 88 and is shaped and sized to contact the valve seat 90 to close off or substantially limit fluid flow through the fluid passageway 88 toward the nozzle 50. A linear actuator 92 controls the axial position of the poppet valve member 92 within the fluid passageway 88. By moving the poppet valve member 92 closer to the valve seat 90, the flow of fluid to the nozzle 50 is restricted as flow area is reduced. The reduction in flow area will impact the velocity at which fluid exits the nozzle 50. Conversely, by moving the poppet valve member 92 further away from the valve seat 90, the flow of fluid to the nozzle 50 is increased as flow area is increased. The linear actuator 92 is operably interconnected with the control line 72 so that the controller 66 can control the position of the poppet valve member 92.

FIGS. 5 and 5A depict an exemplary mill bit 44′ which features an adjustable mill bit body 46′. For ease and clarity of description, the adjustable features of mill bit 44′ are being described separately from those of mill bit 44. However, those of skill in the art will recognize that the adjustable features of mill bit 44′ may be combined with the adjustable features of mill bit 44 in a single bit. The mill bit body 46′ presents a lower cutting face 78 which has cutters formed thereupon as described previously. The mill bit body 46′ also has lateral cutting portions 94 having hardened cutters 96 disposed therein. The lateral cutting portions 94 are adjustable by movement of a mechanical linkage 98 which extends through the mill body 46′ from a control interface 100 to each lateral cutting portion 94. A motor/pump 102 and sliding sleeve 104 interact with the interface 100 to cause movement of the linkage 98 to move the lateral cutting portions 94 between radially expanded (FIG. 5) and radially contracted (FIG. 5A) positions. The motor/pump 102 is operably interconnected with the controller 66 via control line 72. The interface 100 and linkage 98 function to convert the axial motion of the sliding sleeve 104 to radial angular motion for the cutting portions 94. As a result, the controller 66 will be able to provide commands to the motor/pump 102 which will result in the lateral cutting portions 94 being either radially expanded or radially contracted. Movement of the lateral cutting portions 94 to a radially expanded position will provide an increased diameter for the mill bit 44′. Conversely, movement of the lateral cutting portions 94 to the radially contracted position will provide a decreased diameter for the mill bit 44′. It should be understood by those of skill in the art that the ability to changes the diameter of the mill body 46′ is a milling operating feature which can be adjusted or controlled in response to sensed milling operating parameters. Among the sensed milling operating parameters which might result in adjustment of the diameter of the mill body 46′ is a sensed restriction in wellbore 10 wherein a reduction in the diameter of the mill body 46′ would allow the mill body 46′ to pass through the restriction.

FIG. 6 is a schematic diagram which illustrates an exemplary operable interconnection between the controller 66 and sensors 60 which detect several milling operating parameters as well as between the controller 66 and a number of milling operating features which are controlled or adjusted in response to the detected milling operating parameters. Controller 66 is operably interconnected with sensors 60 which detect downhole milling operating parameters. In addition, the controller 66 is operably interconnected with the weight scale 42 and the flow meter 56 which detect uphole milling operating parameters and provide signals indicative of the detected parameters to the controller 66.

The controller 66 is also operably interconnected with various features within the cutting mill assembly 20 which enable it to adjust or control milling operating features. In particular embodiments, the controller 66 is operably interconnected with fluid pump 84 via control line 72 for control of extension of cutters 48. Preferably, the controller 66 is also operably interconnected via the control line 72 with linear actuator 92 in order to control or adjust flow through nozzle 50. Preferably also, the controller 66 is operably associated with the motor/pump 102 in order to control or adjust the diameter of the mill bit body 46′.

As FIG. 6 depicts, the controller 66 is preferably also operably associated with the extended reach tool 28 in order to energize the tool 28 for vibration of the cutting mill assembly 22. Energizing the extended reach tool 28 creates vibrational energy which is imparted to the milling bottom hole assembly 24 to increase its cutting effectiveness. The controller 66 is preferably also operably associated with the circulating tool 30. The controller 66 can control the circulating tool 30 by shifting the sleeve 40 within its housing 34 in order to open or close the lateral flow ports 38. By doing so, the controller 66 can rapidly adjust the flow of fluid which is provided to the milling bottom hole assembly 24.

In some embodiments, the controller 66 will determine what, if any, adjustments of the milling operating features need to be made. In other embodiments, decisions about adjustment of milling operating features are made at surface 14 by human operators. Communications module 110 (FIG. 1) is interconnected with the controller 66 by data linkage 112. The communications module 110 transmits data to a display 114 at surface 14 via communication line 116 which is preferably a two-way telemetry arrangement. The display 114 displays data indicative of the at least one milling operating parameter sensed by the sensors 60, weight scale 42 and flow meter 56. An operator at surface 14 can then evaluate the data and transmit one or more commands to the controller 66 via communications line 116 and data linkage 112. In response, the controller 66 will control the one or more adjustable features of the milling bit 44. Additionally, the communication line 116 transmits signals representative of measured pump rate or fluid flow rate from the flow meter 56 to the controller 66 via data linkage 112. The surface weight scale 42 is also operably interconnected with the communications line 116 so that signals representative of the surface weight can be provided to the controller 66 via the communication line 116 and data linkage 112.

In operation, the cutting mill assembly 20 is run into the wellbore 10 until the milling bottom hole assembly 24 is proximate the plug 18 to be removed. Drilling fluid is flowed down through the cutting mill assembly 20 and out through the nozzles 50 of the milling bit 44. The milling bit 44 is rotated to mill away the plug 18. During milling, the sensors 60 detect downhole milling operating parameters, including torque, weight-on-bit, pressure, temperature, vibration and flow rate of fluid received proximate the milling bottom hole assembly 24. Signals indicative of the sensed milling operating parameters are transmitted from the sensors 60 to the controller 66. Other sensed milling parameters, such as pump flow rate and surface weight are transmitted to the controller 66 from weight scale 42 and flow meter 56 at the surface 14. The controller 66 then controls the adjustable milling operating features to respond to the sensed milling operating parameters.

FIG. 7 illustrates an exemplary control process 120 which might be conducted by the controller 66 or by an operator at surface 14 in order to adjust milling operating features in response to sensed milling operating parameters. It is noted that the depicted control process is exemplary only and no limitation to the particular described steps is intended. Rather, the steps of the control process will vary depending upon the specific programming of the controller 66 and the capabilities of the individual devices which are being controlled by the controller 66. In step 122, the sensors 36 measure milling operating parameters, which may include torque, vibration, temperature, pressure and weight-on-bit. In addition, the controller 66 preferably also measures surface milling operating parameters of surface weight and fluid flow rate are measured by the surface weight scale 42 and the flow meter 56, respectively. In step 124, the sensors 60 detect excessive torque as a milling operating parameter. In step 126, the controller 66, in response to the detection of excessive torque, then compares each of the milling parameters of downhole fluid flow rate, weight-on-bit and vibration against predetermined limits. The controller 66 (or individual at surface 14) then determines which milling operating feature to adjust based upon the comparisons. If the measured downhole flow rate is excessive, but weight-on-bit is acceptable (branch 128), the circulation tool 30 is actuated to reduce flow rate to the milling bottom hole assembly 24 (step 130). As a result, milling torque is reduced but hole cleaning is maintained (see 132). If measured downhole flow rate is acceptable but weight-on-bit is excessive (branch 134), the controller 66 (or individual at surface 14) then compares measured surface weight to downhole weight-on-bit (step 136). If surface weight is acceptable, the controller 66 (or individual at surface 14) determines (step 138) that a weight transfer issue is the cause of the excessive weight-on-bit. In response, the controller 66 will control the extended reach tool 28 to adjust weight-on-bit (step 140). If, during step 136, the controller 66 or individual at surface 14 determines that surface weight is too great (branch 142), then surface weight is reduced in step 144. Surface weight adjustment is normally made by an operator at surface 14 by adjustment of a coiled tubing injector.

If the controller 66 (or individual at surface 14) determines that the flow rate and the weight-on-bit are acceptable (branch 146), the decision is made to adjust mill aggressiveness (step 148). The controller 66/individual at surface 14 then determines whether the interaction between the mill bit 44 and the plug 18 is excessive or not (step 150). If yes, one or more of the cutters 48 on the lower cutting face 78 of the mill bit 46 are retracted to in step 152 in order to reduce frictional cutting contact between the mill bit 46 and the plug 18. Conversely, if the interaction between the mill bit 46 and plug 18 is too low, one or more cutters 48 are extended from the lower cutting face 78 of the mill bit 46 to compensate.

The controller 66 (or individual at surface 14) can also determine whether interaction between the mill body 46′ and the surrounding wellbore 10 is too great, which would indicate a need to reduce the diameter of the milling bit 46′. One technique for determining whether interaction between the mill body 46′ and surrounding wellbore 10 is too great is to move the tool string up and down in the wellbore 10 and monitor weight transfer. In step 154, it is determined that contact between the mill body 46′ and the surrounding wellbore 10 is excessive. In response, the controller (or individual at surface 14) controls the milling bit 44′ to retract the lateral cutting portions 94 (step 156).

In accordance with the exemplary control process 120, the controller 66 or individual at surface 14 can determine whether it is necessary to adjust flow rate through the nozzles 50 of the milling bit 44. In step 158, it is determined that there is excessive debris around the milling bit 44. Ultrasonic imaging technology could be used to detect the amount of debris. In response, the flow area through nozzle(s) 50 is adjusted to increase flow through the nozzle 50 (step 160). These actions should result in good torque response.

Claims

1. A cutting mill assembly for performing a cutting operation within a wellbore, the cutting mill assembly comprising: a milling bottom hole assembly to be disposed into the wellbore by a running string;a running string;a sensor to detect at least one milling operating parameter;a controller which is operably interconnected with the sensor to receive a signal representative of the milling operating parameter;the cutting mill assembly having at least one milling operating feature which can be adjusted; andthe controller further being configured to adjust or control the at least one milling operating feature in response to the at least one milling operating parameter.

2. The cutting mill assembly of claim 1 wherein the at least one milling operating feature is from the group consisting of: extension of a cutter from a bit body of the milling bit, flow area of a nozzle in the bit body, milling body diameter, fluid flow to the milling bottom hole assembly through the running string and vibration imparted to the milling bottom hole assembly.

3. The cutting mill assembly of claim 1 wherein the at least one milling operating parameter includes torque, weight on bit, surface weight, temperature, pressure, vibration or fluid flow received proximate the milling bit bottom hole assembly.

4. The cutting mill assembly of claim 1 wherein the controller is located within the milling bottom hole assembly.

5. The cutting mill assembly of claim 1 wherein the controller is operably interconnected with a display at a surface location which displays data indicative of the at least one milling operating parameter sensed by the sensor; and wherein an operator at a surface location can command the controller to adjust a milling operating feature of the cutting mill assembly in response to the at least one milling operating parameter.

6. The cutting mill assembly of claim 1 wherein the controller autonomously adjusts a milling operating feature of the cutting mill assembly in response to the at least one milling operating parameter.

7. The cutting mill assembly of claim 2 wherein the milling operating feature of vibration imparted to the milling bottom hole assembly is adjusted or controlled by actuating an extended reach tool which is incorporated into the cutting mill assembly in order to create vibrational energy.

8. The cutting mill assembly of claim 2 wherein the milling operating feature of fluid flow to the milling bottom hole assembly through the running string is adjusted or controlled by actuating a circulation tool which is incorporated into the cutting mill assembly.

9. The cutting mill assembly of claim 2 wherein the milling operating feature of milling body diameter is adjusted or controlled by extending or retracting lateral cutting portions of a mill body.

10. A cutting mill assembly for performing a cutting operation within a wellbore, the cutting mill assembly comprising: a milling bottom hole assembly to be disposed into the wellbore by a running string;a running string;a sensor to detect at least one milling operating parameter;a controller which is incorporated into the milling bottom hole assembly and is operably interconnected with the sensor to receive a signal representative of the milling operating parameter;the cutting mill assembly having at least one milling operating feature which can be adjusted; andthe controller further being configured to adjust or control the at least one milling operating feature in response to the at least one milling operating parameter.

11. The cutting mill assembly of claim 10 wherein the at least one milling operating feature is from the group consisting of: extension of a cutter from a bit body of the milling bit, flow area of a nozzle in the bit body, milling body diameter, fluid flow to the milling bottom hole assembly through the running string and vibration imparted to the milling bottom hole assembly.

12. The cutting mill assembly of claim 10 wherein the at least one milling operating parameter includes torque, weight on bit, surface weight, temperature, pressure, vibration or fluid flow received proximate the milling bit bottom hole assembly.

13. The cutting mill assembly of claim 10 wherein the controller autonomously adjusts a milling operating feature of the cutting mill assembly in response to the at least one milling operating parameter.

14. The cutting mill assembly of claim 1 wherein the controller is operably interconnected with a display at a surface location which displays data indicative of the at least one milling operating parameter sensed by the sensor; and wherein an operator at a surface location can command the controller to adjust a milling operating feature of the cutting mill assembly in response to the at least one milling operating parameter.

15. A method of adjusting or controlling at least one milling operating feature of a cutting mill assembly within a wellbore, the method comprising the steps of: sensing at least one milling operating parameter with a sensor that is operably associated with the cutting mill assembly that is run into the wellbore; andadjusting or controlling the at least one milling operating feature of the cutting mill assembly in response to the at least one milling operating parameter that is sensed.

16. The method of claim 15 wherein the at least one milling operating feature is from the group consisting of: extension of a cutter from a bit body of the milling bit, flow area of a nozzle in the bit body, milling body diameter, fluid flow to the milling bottom hole assembly through the running string and vibration imparted to the milling bottom hole assembly.

17. The method of claim 15 wherein the step of sensing at least one milling operating parameter comprises sensing milling operating parameters of torque, weight on bit, surface weight, temperature, pressure, vibration or fluid flow received proximate the milling bit bottom hole assembly.