Patent Publication Number: US-9410389-B2

Title: Self-cleaning fluid jet for downhole cutting operations

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to cutting devices useful for cutting tubular and structural members, such as those in a subsea environment immersed in fluids or a downhole or subsurface applications involving structural and operational control, formation evaluation and monitoring members. The invention also relates generally to cutters used for cutting core samples and drilling in wellbore walls. 
     2. Description of the Related Art 
     Pipe cutters are used to cut tubular members. Pipe cutters typically include a circular cutting blade that is mounted upon a spindle. The spindle, in turn, is mounted upon an arm that can be moved radially out through a slot in a surrounding housing to be brought into cutting contact with a surrounding tubular member to be cut. During cutting, the blade can rotate at approximately 1000 rpm. Pipe cutters are often used downhole, being run in on a tool string to cut a casing member within a wellbore. Commercially available pipe cutters include the MPC Mechanical Pipe Cutter from Baker Hughes Incorporated of Houston, Tex. 
     In operation, the pipe cutter is disposed within a tubular member to be cut, and the cutting blade is rotated by a motor. The supporting arm is then moved so that the cutting blade is placed in cutting contact with the tubular member. The pipe cutter also rotates about it central axis, causing a circumferential cut to be made in the surrounding tubular member. 
     Cuttings or filings create a problem during cutting. They can cause damage to the cutting blade or prevent a clean cut from being made. Efficiency of a pipe cutting operation is affected by materials accumulated and packed in the cutting groove. As a cut is made deeper, the cuttings can become trapped within the cut, magnifying associated operational efficiency deterioration and wear and tear problems. 
     Piping and well structural members used today are made of progressively harder materials, and this makes pipe cutting performance more challenging. During pipe cutting operations, it has been noticed that random and unpredictable torque load fluctuations at times can lock the cutting blade into the pipe, requiring continuous cutting parameters (e.g., torque load, RPM, feed rate, electrical or hydraulic power consumption, cutting efficiency, equipment temperatures, etc.) monitoring and adjustments to reduce the operational frequency of cut interruptions. Cutting adjustments and interruptions lower operational efficiency by increasing cutting time, lower energy cut efficiency and increasing wear and tear in the cutting elements and power drive train. These variations in cutting torque load and cutting advancement rate often requires real time adjustments to the cutting controls due to the equipment&#39;s input power constraints available, strength limitations of the cutting elements such as blade or coring bit, cutting edge materials endurance and abrasion wear resistance due to the cutting action, limitations of the power drive providing rotation action such as electrical motor or hydraulic pump, thermal generation and dissipations of the equipment assembly characteristics in the operating temperature, etc. These load and cutting rate variations are amplified and aggravated by cuttings and debris accumulated in the cutting groove during the cutting operation resulting in reduced cutting energy utilization efficiency, reduced cutting productivity (i.e. cutting rate reduction or interruption), increased cutting equipment wear and tear, higher maintenance costs, frequency and effort, increased difficulty and even impediment to cutting thicker pipes with harder specialty alloys for example. 
     Sidewall coring cutters are used to cut cylindrical coring samples in the wall of a wellbore. These coring cutters are also prone to problems relating to cutting or filings as these tend to prevent a clean cut from being made and/or cause damage to the cutter. 
     SUMMARY OF THE INVENTION 
     The invention provides systems and methods for cleaning or removing cuttings from a cut in a workpiece as cutting is being performed. In a described embodiment, a downhole pipe cutter includes devices and methods that create one or more fluid jets proximate a cut that aids in cleaning cuttings and debris from the cut as it is being made. This invention is applicable to mechanical cutting devices operating from inside or outside of tubulars or pipes immersed in environments that include fluids and where the surrounding immersion fluid is used in the jet cleaning action. The cleaning fluid flow is directed to and around the cutting edge. Cutting equipment solutions benefitting from this invention are utilized in the oilfield, utilities installations, chemical transportation, storage and environmental protection operations. Environmental protection operations are often triggered by regulatory compliance requirement. Specific situations addressed by this invention involve subsea installations or environments immersed in fluids or downhole (subsurface) cutting applications involving cutting of structural and operational monitoring and control members involving material recovery (re-use, re-manufacturing or re-processing equipment parts) or modification of permanent or temporary downhole subsurface installations. Operational monitoring and control members can involve mechanical inkages, electrical monitoring and control and power lines or hydraulic power and control lines used for remote or automated control cutting sequences The cutting operations can be part of a pipe recovery operation, reservoir&#39;s well production completion modification and reservoir&#39;s well production recovery adjustments and optimization, temporary or permanent downhole reservoir production installations, production packer&#39;s recovery, removal of equipment for salvage and recycling for future installation or re-use deployments, or well abandonment operations required by regulatory legislation. Optionally, the cutting operations can be part of multiple sequence steps involving the removal (with or without recovery recycling) and replacement of structural, monitoring or control members associated with reservoir&#39;s well production completion modification and reservoir&#39;s well production recovery adjustments and optimization. Recovery and recycling of subsea and downhole members can involve pipes, valves, flow control, or packers used for reservoir producing zone isolation along the wellbore. The figures shown teach jet creation for a rotating flat circular cutter, but the invention is also applicable to a rotating cutter with cylindrical geometry as used for formation core sample cutting where the jet forming features described herein are placed in the backside of the cylindrical cutting blade and the active cutting edge is in the leading edge of the cylindrical cutter. Cylindrical rotating cutters for collecting formation core samples can be deployed against the borehole wall or along the borehole longitudinal axis along the drilling bit path. 
     In a first particular embodiment, a pipe cutter is provided with a fluid housing that is mounted proximate the cutting blade. In a current embodiment, the housing has a generally circular configuration with a diameter that is smaller than the diameter of the cutting blade. The exemplary fluid housing defines a central chamber having a central fluid inlet and a radial fluid jet outlet. In a described embodiment, the fluid housing includes a raised cupola. 
     In a described embodiment, an impeller blade assembly is secured to or rotates with the cutting blade and rotates within the central chamber of the fluid housing. In a described embodiment, the impeller blade assembly is a multiple stage blade assembly in that there is a set of blades located adjacent another set of blades. The use of at least two stages improves fluid flow through the fluid housing. An upper, reduced-diameter stage draws fluid into the central chamber in an axial direction. A lower, enlarged-diameter stage flows fluid radially outwardly toward the fluid jet outlet. Also in a described embodiment, the impeller blade assembly has curved blades. 
     In operation, rotation of the cutting blade during a cutting operation also rotates the impeller blade assembly. A cleaning fluid jet is created and directed toward and around the active cut area being made as fluid entering the fluid chamber from the fluid inlet is flowed outwardly through the fluid outlet. The fluid jet is also created by the impeller blade assembly as rotation increases the flow rate of fluid exiting the chamber through the fluid outlet. 
     In a second particular embodiment, a fluid collector and compressor assembly is attached to or rotates with the cutting blade. In a described embodiment, the fluid collector and compressor assembly includes one or more fluid collector/compressors that use the rotational motion of the cutting blade to accumulate fluid within their fluid chambers and provide fluid jets directed toward the area of the cut. 
     In a particular embodiment, there are four such collector/compressors in the form of four lobes that collect fluid into a fluid chamber and expel fluid in the direction of the cut. Each collector/compressor lobe preferably has a fluid inlet and a fluid outlet. In specific embodiments, the fluid inlets have larger flow areas than the fluid outlets, thereby allowing fluid velocity to be increased by passing through the collector/compressor. In a described embodiment, the fluid inlet is an opening that is open along a line that is normal to the radius of the cutting blade. The fluid outlet is directed radially outwardly and toward the cut being made. Additional embodiments include collector/compressor lobes on an opposite axial side of the blade that direct fluid away from the cut being made so that fluid will flow through the cut being made to help remove cuttings. 
     In operation, fluid within the surrounding tubular is collected and flowed toward a cut being made by the collector/compressors. Rotation of the cutting blade together with the collector and compressor assembly will cause fluid to be flowed through the fluid inlets and into the fluid chambers of the collector/compressors. The fluid will then be flowed radially outwardly in the direction of the cut under the impetus of centrifugal force. 
     Embodiments of the present invention are also described wherein fluid jet generators are incorporated into sidewall coring cutting devices having generally cylindrical cutting blades. In one embodiment, a core cutting blade is provided with a plurality of collector/compressors in the form of lobes that collect fluid into a fluid chamber and expel fluid in the direction of the cut. In the described embodiment, there are lobes located in both the radial interior of the core cutting blade and the radial exterior of the core cutting blade. In an alternative embodiment, curved or angled fins are used to propagate fluid jets in the direction of the cut. In another alternative embodiment, an independent jet forming component is retained within the radial interior of the coring cutter. In a described embodiment, the independent jet forming component includes a central axial shaft with a plurality of radially outwardly-extending spokes, each of the spokes carrying a jet forming mechanism, such as a lobe or fin of the types described previously. In a described embodiment, the jet forming component is rotated independently of the core cutting blade to generate fluid jets that are directed toward the cut being made. In other embodiments, additional fluid jet generating components are used to create fluid jets that flow fluid away from a cut being made so that fluid will flow through the cut being made and help remove cuttings. 
     Cutting operational methods involve automated cutting control sequences and continuous adjustments. This invention enables an improved cutting operation outlined in the following steps: Positioning the downhole tool in a wellbore extending into the subterranean formation, checking the equipment operational status and environmental conditions before and during cutting operation, commencing cutting operations by rotating a cutting element of the downhole tool and extending the rotating cutting element towards the cutting target and apply force for cutting action with a forced cleaning fluid flow, sensing at least a parameter associated with the cutting operations, and adjusting the cutting operation based on the sensed parameters. Downhole cutting adjustments could be made concurrently with adjustments made in the surface power sources in a well defined cutting protocol sequence algorithm. Surface power source level could be increased as cutting loads increase due to the cutting process and adjustments or conversely reduce surface power source level as cutting loads decrease with associated cutting adjustments. The forced fluid cleaning flow improves the cutting operational efficiency and productivity. The cutting elements and equipment field service operational durability is improved by the forced fluid cleaning flow resulting in less wear and tear of the cutting elements, cleaner cutting groove, less intense cutting operational adjustments, less frequent, more stable, operationally more robust and easier to implement. 
     The directed cleaning fluid flow results in a cleaner cutting groove during the cutting operations enabling the following cutting advantages: The random and unpredictable torque load fluctuations that at times can lock the cutting blade or cutting element into the pipe are reduced, continuous cutting parameters (e.g. torque load, RPM, feed rate, electrical or hydraulic power consumption, cutting efficiency, equipment temperatures, etc.) monitoring lead to less adjustments allowing improved operational frequency and less cut interruptions, reduced cutting adjustments and interruptions improve operational efficiency by shortening cutting time, increasing energy cut efficiency and lowering wear and tear of the cutting elements and power drive train. 
     These reduced load variations in both cutting torque load and cutting advancement rate due to cleaner grooves often requires less real time adjustments to the cutting controls driven by the following considerations: equipment&#39;s input power constraints available, strength limitations of the cutting elements such as blade or coring bit, cutting edge materials endurance and abrasion wear resistance due to the cutting action, limitations of the power drive providing cutting rotation action such as electrical motor or hydraulic pump, thermal generation and dissipations of the equipment assembly characteristics in the operating temperature, etc. . . . These load and cutting rate variations are reduced by the cleaning and removal of cuttings and debris accumulated in the cutting groove during the cutting operation resulting in the improvement of the cutting energy utilization efficiency, increased cutting productivity (Le, cutting rate reduction or interruption), reduction in cutting equipment wear and tear, lower maintenance costs, frequency and effort, reduced difficulty for cutting thicker pipes with harder specialty alloys for example. In dry wells a forced cleaning fluid jet can be dispensed from a tool&#39;s internal fluid container supply. 
    
    
     
       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 an external isometric view of an exemplary pipe cutter which incorporates an exemplary fluid jet forming arrangement in accordance with the present invention. 
         FIG. 2  is a cross-sectional cutaway view of the pipe cutter shown in  FIG. 1 . 
         FIG. 3  is an external isometric view of components of the fluid jet generator used in the pipe cutter shown in  FIGS. 1 and 2 . 
         FIG. 4  is a side, cross-sectional view of the fluid jet generator shown in  FIG. 3 . 
         FIG. 5  is a top view of interior portions of the fluid jet generator shown in  FIGS. 3 and 4 . 
         FIG. 6  is an external isometric view of an exemplary cutting blade which incorporates an alternative fluid jet generator in accordance with the present invention. 
         FIG. 7  is a side, cross-sectional view taken along lines  7 - 7  in  FIG. 6 . 
         FIG. 8  is a top view of the fluid jet generator and cutting blade of  FIGS. 6 and 7 . 
         FIG. 9  is a side view of an exemplary side wall coring tool being used to cut a core sample in a borehole all. 
         FIG. 10  is an external side view of an exemplary core cutting blade which incorporates a fluid jet generator in accordance with the present invention. 
         FIG. 11  is a cross-sectional view taken along lines  11 - 11  in  FIG. 10 . 
         FIG. 12  is an external side view of an exemplary core cutting blade which incorporates an alternative fluid jet generator in accordance with the present invention. 
         FIG. 13  is a cross-sectional view taken along lines  13 - 13  in  FIG. 12 . 
         FIG. 14  is a side, cross-sectional view of a further exemplary core cutting blade which incorporates a further alternative fluid jet generator in accordance with the present invention. 
         FIG. 15  is a cross-sectional view taken along lines  15 - 15  in  FIG. 14 . 
         FIG. 16  is a side view of a further exemplary core cutting blade which incorporates a further alternative fluid jet generator in accordance with the present invention. 
         FIG. 17  is a cross-sectional view taken along lines  17 - 17  in  FIG. 16 . 
         FIG. 18  is a cross-sectional view of the core cutting blade and fluid jet generator of  FIGS. 16 and 17  now being used to cut a core sample in a wellbore side wall. 
         FIG. 19  is a side, cross-sectional view of a further exemplary core cutting blade which incorporates a further alternative fluid jet generator in accordance with the present invention. 
         FIG. 20  is a cross-sectional view taken along lines  20 - 20  in  FIG. 19 . 
         FIG. 21  is a side view of an exemplary flat circular cutter which incorporates a further alternative fluid jet generator in accordance with the present invention. 
         FIG. 22  is a cross-sectional view taken along lines  22 - 22  in  FIG. 21 . 
         FIG. 23  is an operational cutting adjustment flow chart involving forced cut cleaning fluid flow. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  depicts an exemplary pipe cutter  10  which is used to cut tubular members. The pipe cutter  10  generally includes a tubular cutter housing  12  having a tapered nose portion  14 . The housing  12  is shaped and sized to be disposed within a tubular member that is to be cut. As can be seen with reference to  FIG. 2 , a cavity  16  is defined within the housing  12 . The cavity  16  is shaped and sized to retain within a support arm  18  which carries a rotary spindle  20  as well as a flat, circular cutting blade  22 . A circular cutting blade  22  is mounted upon the spindle  20  and can be rotated by a motor (not shown) contained within the pipe cutter  10  in a manner known in the art. The support arm  18  is articulable so that the cutting blade  22  can be moved into or out of the cavity  16  during a cutting operation. 
     The pipe cutter  10  is provided with a fluid jet generator, generally indicated at  24 , that is used to create a fluid jet that will aid in removing cuttings and debris from a cut  26  that is being made in a surrounding tubular pipe  28 . The fluid jet generator  24  includes a fluid housing  30  that is generally dome-shaped and preferably provides a generally circular cross-section. The fluid housing  30  defines an interior fluid chamber  32  (see  FIG. 4 ). A fluid inlet  34  is disposed through the housing  30  to permit fluid within the surrounding pipe  28  to flow into the fluid chamber  32 . A screen  36  is preferably provided within the fluid inlet  34  in order to prevent debris within the pipe  28  from entering the fluid chamber  32 . A fluid outlet  38  is provided along a radial side of the fluid housing  30 . Preferably, the fluid outlet  38  is disposed through a radial projection or arm  40  that extends radially outwardly from the outer circumference  42  of the fluid housing  30 . In a particular embodiment, the fluid housing  30  presents a substantially planar top plate  44  with a central raised cupola  46 . 
     An impeller blade assembly, generally indicated at  48 , is located within the fluid chamber  32 . The impeller blade assembly  48  is visible in  FIGS. 4 and 5 . The impeller blade assembly  48  is affixed to or rotates with the cutting blade  22 . In the depicted embodiment, the cutting blade  22  and the impeller blade assembly  48  rotate in a counter-clockwise direction. In one embodiment, the impeller blade assembly  48  includes a plurality of long blades  50  and shorter blades  52  that extend radially outwardly from a central hub  54 . The blades  50 ,  52  are preferably curved along their lengths back from rotation. The blades  50 ,  52  are preferably also canted, as illustrated by  FIG. 4 . The inventors have found that canting the blades  50 ,  52  helps to bring fluid from the incoming axial direction to the radial output direction. In the depicted embodiment, both the long blades  50  and the shorter blades  52  are canted. In an alternative embodiment, the shorter blades  52  are not canted while the long blades  50  are canted. Alternatively, the shorter blades  52  might be canted but not curved while the long blades  50  are curved, but not canted. In the depicted embodiment, there are four long blades  50  and four shorter blades  52 . However, there may be more or fewer than four of each type of blade  50  or  52 . 
     In a particular embodiment, the impeller blade assembly  48  has two stages: an upper stage  56  and a lower stage  58 . The upper stage  56  includes the shorter blades  52  and is located within the cupola  46  of the fluid housing  30 . The lower stage  58  includes the long blades  50  and is located below the cupola  46 . 
     In operation, a fluid jet  59  ( FIG. 2 ) is created as the cutting blade  22  is rotated during cutting. Rotation of the cutting blade  22  rotates the impeller blade assembly  48  within the fluid housing  30 . Rotation of the impeller blade assembly  48  draws fluid into the fluid chamber  32  through the fluid inlet  34  and flows fluid out through the fluid outlet  38 . Rotation of the impeller blade assembly  48  imparts velocity to the fluid jet  59 , allowing it to be effective in removing cuttings and debris from the cut  26 . 
       FIGS. 6-8  depict an alternative embodiment for a fluid jet generator  60  that is incorporated onto a cutting blade used in a pipe cutter. The exemplary fluid jet generator  60  includes four fluid collector/compressor lobes  62 . However, there may be more or fewer than four such lobes, if desired. In the depicted embodiment, the lobes  62  are arranged around a center ring  64 . Each of the lobes  62  defines a central fluid chamber  66 . Each of the lobes  62  is provided with a fluid inlet  68  and a fluid outlet  70  that permit fluid to enter into and exit from the fluid chamber  66 . It is noted that the fluid outlets  70  are oriented such that fluid exiting the fluid chamber  66  will be directed generally radially outwardly from the center of the fluid jet generator  60  (see  FIG. 8 ). The fluid inlets  68  are preferably oriented in a direction normal to the radial direction. It is noted that the lobes  62  of the fluid jet generator  60  are preferably affixed to or mounted upon the cutting blade  22 . Alternatively, the lobes  62  are not affixed to the blade  22  but will be rotated as the blade  22  is rotated. 
     In operation, rotation of the cutting blade  22  will generate fluid jets that are directed toward the cut  26  being made in the surrounding pipe  28 . As the cutting blade  22  is rotated, fluid within the pipe  28  will be collected by the lobes  62 . Fluid will flow into the fluid inlets  68  under the impetus of blade rotation and be compressed within the chamber  66 . The fluid will exit the chambers  66  via the fluid outlets  70 . The restricted flow area provided by the fluid outlets  70  increases the velocity of fluid passing through the outlets  70 . Fluid jets  72  (see  FIG. 4 ) are thereby formed and directed radially outwardly so that they aid in removing cuttings and debris from the area proximate the cut  26  during cutting. 
     It can be seen that the invention also provides methods for cutting a tubular member. According to an exemplary method of cutting, the pipe cutter  10 , being equipped with either the fluid generator  24  or  60 , is disposed within a tubular member  28  to be cut. The cutting blade  22  is then rotated to cut the tubular member  30 . A fluid jet is created by the fluid jet generator  24  or  60  and directed toward the cut  26 , thereby helping to remove cuttings from the cut. Preferably, incompressible fluids or liquids are used with the fluid jet generators  24 ,  60  of the present invention. Typical wellbore fluids include water, brines, and drilling muds. 
       FIG. 9  illustrates an exemplary sidewall coring tool  80  that has been disposed within a wellbore  82  by a wireline running arrangement  84 . Stabilizers  86  help secure the coring tool  80  within the wellbore  82 . A rotary coring cutter  88  extends radially outwardly from the coring tool  80  and is being rotated to cut a cylindrical core sample  90  in the wall of the wellbore  82  in a manner that is known in the art. 
     The rotary coring cutter  88  is shown only generally in  FIG. 9 . However, the coring cutter  88  incorporates a fluid jet generator in accordance with the present invention which directs fluid jets toward the circular cut  92  being made in the wall of the wellbore  82 . The fluid jet generator may be of several different constructions in accordance with the present invention. 
       FIGS. 10 and 11  illustrate a first embodiment for a fluid jet generator that is used in conjunction with coring cutter  88   a . The coring cutter  88   a  is a generally cylindrical side all  94  with a closed axial end wall  96 . A rotary shaft  98  is affixed to the closed axial end wall  96  and is used to rotate the cutter  88   a . At the opposite axial end of the sidewall  94  from the closed axial end  96  is a toothed cutting edge  100 . The sidewall  94  and axial end wall  96  define an interior chamber  102  that within which a cut core sample will reside as cutting occurs. The fluid jet generator in this instance is in the form of one or more collector/compressor lobes  104  that are located within the interior chamber  102  of the cutter  88   a . In addition, collector/compressor lobes  106  are disposed upon the outer radial surface of the sidewall  94 . In a manner similar to the lobes  62  described earlier, each of the lobes  104 ,  106  defines an interior chamber and has a fluid inlet  108  and a fluid outlet  110 . The fluid outlets  110  have a smaller flow area than the fluid inlets  108  which provides an increase in fluid velocity. The fluid outlets  110  are directed toward the cutting edge  100  so that the resulting fluid jets are propagated in the direction of the cut being made as the cutter  88   a  is rotated. It is noted that, while there are lobes  104  and  106  shown disposed on both the interior and the exterior of the sidewall  94 , there may, if desired, only be lobes on either the interior or exterior. Also, although four such lobes  104  and  106  are depicted, there may be more or fewer than four of each or of either. 
       FIGS. 12 and 13  depict an alternative embodiment for a fluid jet generator that is used in conjunction with coring cutter  88   b . The coring cutter  88   b  is constructed and operates in the same manner as the coring cutter  88   a  except where indicated otherwise. In place of the collector/compressor lobes  104  and  106 , curved fins  112  are affixed to both the interior and exterior of the sidewall  94 . As the coring cutter  88   b  is rotated, fluid will approach each fin  112  in the angular direction indicated by arrow  114 . The fin  112  will redirect the fluid in an axial direction, as indicated by arrow  116 . As is apparent from  FIG. 12 , the resulting fluid jet is propagated in the direction of the cut being made by the cutting edge  100 . 
       FIGS. 14 and 15  illustrate a further alternative embodiment for a fluid jet generator that is used in conjunction with a coring cutter  88   c  to form cut  92  in the sidewall of the wellbore  82 . The coring cutter  88   c  differs from the cutters  88   a  and  88   b  in that there is an opening  118  disposed through the axial end wall  94 . In this embodiment, the coring cutter  88   c  is rotated independently from the jet forming component  120  by means of rotational ring  122 . In other embodiments, the jet forming component  120  and the coring cutter  88   c  are interconnected and rotated together. The exemplary jet forming component  120  includes a central shaft  124  that is disposed through the opening  118  and is rotated by a motor (not shown). Radial spokes  126  extend outwardly from the distal end of the shaft  124 . A jet forming mechanism  128  is located at the distal end of each spoke  126 . Each of the jet forming mechanisms  128  is designed to create and direct a fluid jet toward the cut  92  as the shaft  124  of the jet forming component  120  is rotated. In the depicted embodiment, each jet forming mechanism  128  comprises a tube having a fluid inlet  130  that is oriented in the angular direction and a fluid outlet  132  that is oriented axially in the direction of the cut  92 . As the jet forming component  120  is rotated in the direction indicated by arrows  134  in  FIG. 15 , fluid will enter the fluid inlet  130  of each jet forming mechanism  128  and be directed axially through the fluid outlet in the direction of the cut  92 . As illustrated in  FIG. 14 , the jet forming mechanisms  128  of the component  120  are preferably placed into contact with the wellbore  82  during cutting to maximize the cleaning ability of the jet forming component  120 . 
       FIGS. 16-18  illustrate a further embodiment for a fluid jet generator that is used in conjunction with a coring cutter  88 d to form cut  92  in the sidewall of the wellbore  82 . The coring cutter  88 d differs from the cutters  88 a and  88 b in that there are openings  134  disposed through the axial end wall  96  surrounding shaft  98 . In the depicted embodiment, there are curved fins  136  disposed upon the radial interior of sidewall  94 . The fins  136  are constructed and operate in the same manner as the fins  112  described earlier and function to direct fluid toward the cut  92 , as  FIG. 18  depicts. In addition, there are fins  138  disposed on the outer radial surface of the sidewall  94  of the cutter  88 d. The curved fins  138  are oriented to direct fluid in the axial direction opposite from the fins  136  (i.e., away from cut  92 .  FIG. 18  illustrates that, during cutting, fluid flows through the openings  134  and into the interior chamber  102 . The fins  136  will propagate fluid jets toward the cut  92  while the fins  138  will flow fluid away from the cut  92 . 
     In operation during cutting, fluid is flowed toward the cut  92  by the fins  136  as the fins  138  flow fluid away, resulting in a circulation of fluid through the cut  92 , as illustrated by arrows  140 . It is noted that the fins  136  and  138  might also be interchanged, so that fins on the radial exterior of the sidewall  94  flow fluid toward the cut  92  while fins on the interior of the radial sidewall  94  flow fluid away from the cut  92 . 
       FIGS. 19-20  depict a further embodiment for a fluid jet generator that is used in conjunction with a coring cutter  88   e . In most respects, the fluid jet generator for this embodiment is constructed and operates in the same manner as the fluid jet generator depicted in  FIGS. 14-15  and described above. However, a fluid impeller  142  is affixed to the shaft  124  above the jet forming mechanisms  128 . In the depicted embodiment, the impeller  142  includes two blades designed to flow fluid in the direction of the cut  92  as the shaft  124  is rotated. Although only two blades are shown, those of skill in the art will understand that there may be more or fewer than two. The impeller  142  will increase fluid flow into and through the cut  92  during cutting. 
       FIGS. 21-22  illustrate an exemplary flat circular cutting blade  144  which incorporates a further embodiment for a fluid jet generator in accordance with the present invention. The blade  144  is constructed and operates in the same manner as the cutting blade  22  described earlier. One axial side of the cutting blade  144  is visible in  FIG. 21 . The opposite axial side of the blade  144  (which is not visible in  FIG. 21 ) may have the same components and construction as the blade  22  shown in  FIG. 8 , such that the lobes  62  will direct fluid jets radially outwardly along the blade  22 . Fluid collector/compressor lobes  146  are disposed upon the side of the cutting blade  144  which is visible in  FIG. 21 . The lobes  146  each have a fluid inlet  148  and a fluid outlet  150 . The fluid outlets  150  are oriented to flow fluid entering each lobe  146  radially inwardly along the blade  144 . 
     In operation, as depicted in  FIG. 22 , the lobes  62  generates fluid jets  152  toward a cut  154  being made in a work piece. At the same time, lobes  146  generate fluid jets  156  in a direction away from the cut  154 . As a result, fluid will flow through the cut  154 , as indicated by arrow  158 , to assist in the removal of cutting from the cut  154 . 
     Operation of rotary cutting tools having cutting blades in conjunction with associated fluid jet generators can be automated. The steps of automated cutting processes can be carried out using automated programmable controllers of a type known in the art. The controller is preferably pre-programmed with a desired cutting protocol for successful cutting of a workpiece.  FIG. 23  is a flow chart illustrating an exemplary cutting operation  160 . According to the first step  162  of the operation, the cutting equipment is positioned into a downhole environment and the equipment status and environmental conditions are checked. Thereafter, cutting starts in step  164  by rotating a cutting element and extending the rotating cutting element toward the target work piece. In step  166 , a fluid jet is formed and directed according to methods described previously. In step  168 , the cutting operation is monitored. This may be accomplished, depending upon the particular arrangement, by direct observation or indirect observation using cameras of a type known in the art or by the use of one or more sensors that sense at least one parameter associated with the cutting operation. Exemplary sensed parameters include pressure or cutting load, temperature, and blade position or angle. A user may select the desired observation frequency in accordance with this step. Adjustments can be made to the cutting operation (step  170 ) based upon either the observation or sensed parameter(s). For example, the surface power source level could be increased as cutting load increases due to cutting adjustments. Conversely, surface power source level could be reduced as cutting load decreases due to cutting adjustments. Details relating to the control and adjustment of electrical power supplied to downhole devices are described in U.S. Pat. No. 7,987,901 entitled “Electrical Control for a Downhole System” issued to Krueger et al. U.S. Pat. No. 7,987,901 is owned by the assignee of the present application and is incorporated herein in its entirety by reference. 
     Thereafter, a decision is made in step  172  either to complete the cutting operation or to abort the cutting operation. If a decision is made to abort the cutting operation (“Y”), the cutting operation is ended (“End”  174 ). If a decision is made to complete cutting (“N”), the operation  160  continues in an iterative or cyclical fashion with step  168  and carrying through to step  172 , in accordance with a predetermined cycle frequency. If desired, the operation may have a step  174  wherein an aborted cutting operation is restarted with step  162 . 
     It can be seen that the invention provides rotary cutting tools, including pipe cutter  10  and rotary coring cutter  88  having rotary cutters with self-cleaning fluid jets to clean cuts that are made in work pieces during cutting. Exemplary cutters are in the form of flat, circular cutting blades as well as coring cutters that have a generally cylindrical sidewall defining an interior chamber, a cutting edge at one axial end of the sidewall and an axial end wall opposite the cutting edge. The work pieces can be in the form of a tubular member or a wellbore sidewall. 
     Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.