WELLBORE OPERATIONS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. non-provisional patent application Serial No. 12/416,998 filed April 2, 2009, and entitled "Methods for Determining Mechanical Specific Energy for Wellbore Operations," which is hereby incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND

Field of the Invention

[0003] The present invention is directed to monitoring and controlling wellbore operations; to monitoring and controlling wellbore drilling operations in real time; and, in one particular aspect, to accomplishing these things by determining mechanical specific energy for an operation by taking into account electrical or other energy input to one or more machines used in such operations. Background of the Technology

[0004] The prior art discloses a wide variety of systems and methods for monitoring wellbore operations and for sensing and measuring parameters related to such operations, both downhole and at the surface. The prior art also discloses a wide variety of sensors, measurement apparatuses, devices, and equipment for sensing, measuring, recording, displaying, calculating, processing, and transmitting measured values for operational parameters, including, but not limited to, weight-on-bit (WOB), rate of penetration (ROP), rotary speed, bit speed, top drive speed, downhole motor speed, and torque on a drillstring or on a bit.

[0005] Many systems and methods have been proposed and implemented for using such sensed and measured operational parameters to enhance, facilitate, and, in some cases, optimize operational performance and the performance of apparatuses, devices and equipment involved in such operations; including, but not limited to, drilling operations. In 1965 R. Teale proposed a model for analyzing and predicting drilling performance based on a calculation of "mechanical specific energy" in an article entitled "The Concept Of Specific Energy In Rock Drilling" [Int'l J. Rock Mech. Mining Sci. (1965) 2, 5773]. Teale has a mathematical definition ("Teale definition") of mechanical specific energy, which uses weight-on-bit (WOB), rig rotary speed in rpm's; torque at the bit; rate of penetration (ROP), and an area, i.e., wellbore (or bit) cross-sectional area.

[0006] In a 1992 research study, (see paper entitled "Quantifying Common Drilling Problems With Mechanical Specific Energy And A Bit-Specific Coefficient of Sliding Friction", SPE 24584, 373388), R.C. Pessier et al. developed an energy balance model for drilling under hydrostatic pressure using a comparison between full scale simulator tests and field data. As key indices of drilling performance, they employed mechanical efficiency, Teale's mechanical specific energy parameter, and a bit-specific coefficient of sliding friction for bit selection and analysis. "Mechanical specific energy" was defined as work done per unit volume of rock drilled and it was assumed that the minimum specific energy required to drill is approximately equal to the compressive strength of the rock being drilled. The mechanical efficiency of drilling was then estimated by comparing actual specific energy required to drill an interval with the minimum expected specific energy needed to drill that interval. Pessier et al. analyzed values of various parameters (actual specific energy, minimum specific energy, energy efficiency, and bit specific coefficient of sliding friction) with respect to ROP under different situations (e.g., different bits, different WOB's, different RPM's, different hydraulics, and under atmospheric and hydrostatic pressure). It was concluded that mechanical specific energy, mechanical efficiency, and bit specific coefficient of sliding friction provided good indicators of drilling performance and could enhance the interpretation of data for the following:

^■ the detection and correction of major drilling problems;

^■ analysis and optimization of drilling practices;

^■ bit selection;

^■ failure analysis;

^■ evaluation of new drilling technologies and tools;

^■ real-time monitoring and controlling of the drilling process;

^■ analysis of MWD (measurement while drilling) data; and

^■ further system developments.

[0007] In a 2002 paper, Waughman et al. reported on a system and method for optimizing the bit replacement decision ["Real Time Specific Energy Monitoring Reveals Drilling Inefficiency and Enhances the Understanding of When to Pull Worn PDC Bits", IADC/SPE 74520, 2002, 114]. The system involved measuring the mechanical energy input at the drill rig floor, calculating the drilling specific energy, checking current formation type via real- time downhole gamma ray readings, comparing the specific energy with the benchmark new bit specific energy, and then using these values to assess the bit's state. Success of the system was reported for synthetic based mud systems where bit balling does not mask bit dull condition. The process worked in water-base drilling fluids that had replaced earlier synthetic muds because both balled new bits and dull bits exhibit similar levels of inefficiency.

[0008] In general, certain prior art systems and methods use calculations of mechanical specific energy based on sensed and measured values of drilling parameters. Data is often obtained from locations at the bit. For example, torque and rotational speed (rpm's) can be measured at various locations, e.g. downhole or at the surface, and the measurement, from whichever location, is then used.

[0009] U.S. Patent 7,243,735, co-owned with the present application, discloses methods for wellbore operations with a wellbore system, the methods including:

^■ acquiring with sensor systems data corresponding to a plurality of parameters, the data indicative of values for each parameter of the plurality of parameters, each parameter corresponding to part of the wellbore system;

^■ based on said data, calculating a mechanical specific energy value for each of a plurality of mechanical specific energies each related to a mechanical specific energy for a part of the wellbore system; and

^■ monitoring the value of each of the mechanical specific energies, in one aspect, in real time.

Systems and methods are disclosed for determining localized differentiated mechanical specific energy parameters: surface mechanical specific energy; drillstring mechanical specific energy; and bit (or mill or other apparatus) mechanical specific energy. The patent also discloses a method for a wellbore operation with a wellbore system, the method including:

^■ acquiring with sensor systems data corresponding to a plurality of parameters, the data indicative of values for each parameter of the plurality of parameters, each parameter corresponding to part of the wellbore system;

^■ based on the data, calculating a mechanical specific energy value for each of a plurality of mechanical specific energies each related to a mechanical specific energy for a part of the wellbore system;

^■ monitoring the value of each of the mechanical specific energies; and ^■ wherein the wellbore operation is an operation with a rotating bit and values for the mechanical specific energies are calculated according to the equation for Teale's definition of mechanical specific energy.

[0010] In known methods for calculating mechanical specific energy, only the mechanical components are been taken into account. Certain known methods for calculating mechanical specific energy require a relatively large amount of data and, sometimes, calibration and re- calibration of weight-on-bit, bit RPM, bit torque and rate of penetration. Actual bit rotational speeds and torques can frequently be difficult to determine precisely and accurately. This can occur when using a downhole motor or turbine to rotate a bit. Certain known methods do not take into account the actual energy used on a rig to drill a wellbore.

BRIEF SUMMARY OF THE DISCLOSURE

[0011] Embodiments described herein disclose, in certain aspects, methods for determining mechanical specific energy for a wellbore operation, e.g., a drilling operation, milling, reaming, etc., which takes into account the energy (power) input to machines which are involved in the operation, e.g. for rotation of a drill bit, mill, or reamer, etc. In certain aspects, this includes energy input to a top drive, or a rotary table, and/or mud pumps. [0012] Embodiments described herein disclose, in certain embodiments, methods for determining the mechanical specific energy (in one aspect, in real time) for a wellbore operation without using values for certain measured parameters, e.g., drilling or milling or reaming parameters, but rather which use measurements of values of energy (e.g. electrical or hydraulic) input into equipment involved in an operation. Often in drilling or other operations utilizing downhole mud motors, there are no sensors, e.g. for bit torque or RPM. Further, even in some existing conventional operations without downhole motors, surface measurements, e.g. of speed and torque, can vary considerably from the values at the bit. [0013] Embodiments described herein, in certain aspects, disclose a method for determining mechanical specific energy for a wellbore operation (e.g. drilling, milling, reaming), the method including: measuring power input to machines used in a wellbore operation and producing a value for input power, and calculating mechanical specific energy for the operation based on the value for the input power. Embodiments described herein also disclose a computer-readable media having computer executable instructions for a method according to embodiments described herein, the computer-executable instructions performing a step or steps of the method. [0014] Embodiments described herein, in certain aspects, disclose a computing unit configured to read and perform the computer-executable instructions on computer-readable media.

[0015] Embodiments described herein disclose, in certain aspects, a method wherein

Mechanical Specific Energy, MSE, is calculated according to the equation as follows:

MSE = (r)(Power)/(D ² )(ROP)

in which "r" is a constant for converting units of power to units of MSE; "Power" is energy input to the machines; "D" is diameter of a bit used for the drilling; and "ROP" is rate of penetration of the bit into a formation being drilled. This calculation can be done in real time.

[0016] In addition to specific objects stated herein for at least certain preferred embodiments (but not necessarily for all embodiments), other objects and purposes will be readily apparent to one of skill in this art. It is, therefore, an object of at least certain preferred embodiments described herein provide new, unique, useful, and non-obvious systems and methods of their use all of which are not anticipated by, rendered obvious by, suggested by, or even implied by any of the prior art, either alone or in any possible legal combination. [0017] Accordingly, embodiments disclosed herein include features and advantages which are believed to enable it to advance wellbore operations monitoring and control technology. Characteristics and advantages of the embodiments disclosed herein and additional features and benefits will be readily apparent to those skilled in the art upon consideration of the following description of preferred embodiments and referring to the accompanying drawings. [0018] Embodiments described herein are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures, functions, and/or results achieved. Features disclosed herein have been broadly described so that the detailed descriptions of embodiments preferred at the time of filing may be better understood, and in order that the contributions of the embodiments described herein to the arts may be better appreciated. There are, of course, additional aspects described below and which may be included in the subject matter of the claims. Those skilled in the art who have the benefit of embodiments described herein, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing embodiments described herein. [0019] What follows are some of, but not all, the objects of embodiments described herein. In addition to the specific objects stated below for at least certain embodiments, other objects and purposes will be readily apparent to one of skill in this art who has the benefit of teachings and disclosures herein. It is, therefore, an object of at least certain embodiments to provide the embodiments and aspects listed above and:

^■ New, useful, unique, efficient, non-obvious methods for accurately determining the mechanical specific energy for a wellbore operation, e.g. a drilling, milling, or reaming operation; and

^■ Such methods which employ values for electrical energy supplied to machines involved in the operation, e.g. in rotating a drill bit to drill a wellbore, a mill, or a reamer; and

^■ Such methods which do not use a variety of directly measured parameters to calculate mechanical specific energy, e.g. but not limited to, drilling parameters; and

^■ Such methods that take into account the energy supplied to mud pumps used in pumping drilling fluid for a drilling operation and/or for driving a downhole motor that rotates a drill bit.

[0020] The embodiments described herein recognize and address the problems and needs in this area and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one of skill in this art who has the benefits of the realizations, teachings, disclosures, and suggestions herein, various purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings.

[0021] It will be understood that the various embodiments described herein include one, some, or all of the disclosed, described, and/or enumerated improvements and/or technical advantages and/or elements. Certain aspects, certain embodiments, and certain preferable features are set out herein. Any combination of aspects or features shown in any aspect or embodiment can be used except where such aspects or features are mutually exclusive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: [0023] Figure 1 is a schematic view of an embodiment of a system that can employ methods in accordance with the principles described herein;

[0024] Figure 2 is a schematic view of an embodiment of a method in accordance with the principles described herein; and

[0025] Figure 3 is a graphic illustration of embodiments of methods in accordance with the principles described herein.

DETAILED DESCRIPTION

[0026] The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. Any combination of aspects and/or features described below or shown in the dependent claims can be used.

[0027] In showing and describing these embodiments, like or identical reference numerals are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. So long as they are not mutually exclusive or contradictory any aspect or feature or combination of aspects or features of any embodiment disclosed herein may be used in any other embodiment disclosed herein. [0028] In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to... ." Also, the term "couple" or "couples" is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections.

[0029] Referring now to Figure 1, an embodiment of a system 10 is schematically shown. System 10 includes a drilling rig 11 depicted schematically as a land rig, but other rigs (e.g., offshore rigs and platforms, jack-up rigs, semisubmersibles, drill ships, and the like) are within the scope of the disclosure. In conjunction with an operator interface, e.g. an interface I, a control system 14 controls operations of the rig. The rig 11 includes a derrick 13 that is supported on the ground above a rig floor 15. The rig 11 also includes lifting apparatus, a crown block 17 mounted to derrick 13 and a traveling block 19 interconnected by a cable 21 that is driven by a drawworks 23 (with an electrically powered motor or motors 23m) to control the upward and downward movement of the traveling block 19. Traveling block 19 carries a hook 25 from which is suspended a top drive system 27 which includes a variable frequency drive controller 26, a motor (or motors) 24, electrically powered, and a drive shaft 29. A power swivel may be used instead of a top drive. The top drive system 27 rotates a drillstring 31 to which the drive shaft 29 is connected in a wellbore 33. The top drive system 27 can be operated to rotate the drillstring 31 in either direction. A rotary system 60 has a motor 60m and a rotary table and kelly used to rotate the drillstring. In one aspect, the drillstring 31 is coupled to the top drive system 27 through an instrumented sub 39 which includes sensors that provide drilling parameter information.

[0030] The drillstring 31 may be any typical drillstring and, in one aspect, includes a plurality of interconnected sections of drill pipe 35 a bottom hole assembly (BHA) 37, which can include stabilizers, drill collars, and/or an apparatus or device, in one aspect, a suite of measurement while drilling (MWD) instruments including a steering tool 51 to provide bit face angle information. Optionally a bent sub 41 is used with a downhole or mud motor 42 and a rotatable member 56 which, in one aspect, is a bit, connected to the BHA 37. The face angle of the bit 56 can be controlled in azimuth and pitch during drilling. Optionally, the rotatable member 56 is replaced with a mill, reamer, or reaming bit.

[0031] Drilling fluid is delivered to the drillstring 31 by mud pumps 43 which have an electrically-powered motor or motors 43m through a mud hose 45. The drillstring 31 is rotated within bore hole 33 by the top drive system 27, the rotary system 60, the mud motor 42, or combinations thereof. During sliding drilling, the drillstring 31 is held in place by top drive system 27 while the bit 56 is rotated by the mud motor 42, which is supplied with drilling fluid by the mud pumps 43. The driller can operate the top drive system 27 to change the face angle of the bit 56. The cuttings produced as the bit drills into the earth are carried out of bore hole 33 by drilling mud supplied by the mud pumps 43. Optionally, machines are hydraulically powered instead of electrically powered.

[0032] A rig power system 70 is the overall power system powered as shown by three individual engine generator sets 72a, 72b, 72c (sometimes called prime movers) or may be supplied energy from an alternative source as, for example, a utility distribution on a land rig or a feed from a large power generation unit for a very large offshore fixed installation. Regardless of the primary power source, individual power control is provided to equipment on the drilling rig needing such, e.g. each of the items 23, 27, 43 and/or 60, optionally, has its own single board computer 23 c, 27c, 43 c and 60c, respectively. The single board computers 23c, 27c, 43c and 60c each have programmable media programmed so that each separate computer can control its particular tool or system. The computer is programmed to perform desired calculations. Each single board computer can control its respective tool or system. Optionally, a main control system 14 can control all rig functions and is in communication with each single board computer. In one aspect this is classified as auxiliary loads 65 which are supplied power from a transformer 71, e.g. such things as lighting, centrifugal pumps, and hotel loads. In addition to these are drilling task specific loads, as, for example, the drawworks 23 whose motor is powered by a converter 73b. Other loads are the top drive 27 or the rotary table 60 whose motors 27m and 60m, respectively, are powered by a converter 73 a. Additionally mud pumping loads consist of from one to three or more mud pumps 43 each with at least one motor 43m, powered by a converter 73c.

[0033] In one aspect, power being used by either of the rotators (either the rotary table 60 or the top drive 27 and/or by the mud pumps) is monitored instantaneously. Power monitor devices 27p, 6Op, and 43p measure the power being consumed by the top drive 27, the rotary table 60, or the mud pumps 43, respectively. The system 14 may include a display D for displaying calculated mechanical specific energy, MSE, in real time.

[0034] Referring now to Figure 2, a method for determining mechanical specific energy, MSE, expressed as energy input to a system per volume of rock drilled (or of item milled or of wellbore reamed) in accordance with the principles described herein is shown. Electrical energy input into drilling equipment is measured ("MEASUREMENT ENERGY INPUTS"), e.g., for the motors of a rotary, top drive, mud pumps and/or a drawworks. The equipment, in one aspect, includes electric motor(s) and the mud pumps. According to the embodiments described herein, measured energy inputs can include energy in either electrical or hydraulic form, e.g. for hydraulically driven machines, e.g. hydraulically powered top drives, the fluid volume and pressure.

[0035] The energy input to the motors is determined based on the electrical power sensed and measured by power monitor devices 43p, 27p, and 6Op. Voltages and the amperages can be measured using, e.g. cabling or electrical bus bars to the electric motors, either AC or DC. [0036] In some embodiments, the top drive or rotary table might be hydraulically powered, in which the power would be determined from the conventional means of multiplying flow rate and volume with appropriate scaling. [0037] Energy input is expressed in typical energy units, e.g. in kilowatts. The rate of penetration ("MEASUREMENT ROP") is measured by any suitable known method and apparatus, e.g. by encoder or other means and expressed in feet per hour. The bit diameter ("BIT DIAMETER VALUE") is expressed in inches. A computer or similar apparatus ("CALCULATOR") receives the various measurements, processes them and calculates the mechanical specific energy ("MSE").

[0038] For a typical top drive motor, mud pump motor, or rotary motor, the product of the voltage and amperage from their respective generators is proportional to the developed horsepower. The product of the voltage times the amperage is a number of kilowatts. Similarly, the product of the applied voltage times the amperage for the motors of the mud pumps is a number of kilowatts. The mud pumps provide the motive fluid for a downhole mud motor with respect to which the applied voltage is proportional to the resulting bit rotational speed in rpm's, and the change in amperage of the mud pump motors is proportional to the applied torque of the bit into the formation, and this is proportional to the torque of the rotating bit. Once the energy inputs and other values are determined, the calculator calculates MSE.

[0039] Drilling conventionally with a bit having a diameter D, with a surface rotator, i.e. a rotary table (rt) or top drive (td) (either one or the other only, henceforth referred to as "rt/td") and with no downhole motor imparting rotation to the bit, and with direct measurement of the top drive or rotary table power measured in KW, the formula for MSE is:

MSE _conventional = (3,380.7 * KW _rt/td ) / (D ² * ROP)

[0040] In another situation, drilling is done with a downhole mud motor and "sliding", that is, the downhole mud motor is imparting all of the rotational torque to the bit and the rt/td is not spinning (i.e., no rotation of the rotary table or top drive). With direct measurement of the mud pump KW, both on-bottom and off-bottom, a Δp _umpK w is calculated as follows:

ΔpumpKW ⁼ KW _0n bottom " KW _o ff bottom

"KW _{off bottom} " is the KW expended by the drilling fluid in rotating the downhole mud motor with the bit not touching, or engaged with, the bottom of the formation. "KW _0n bottom" is the KW expended by the drilling fluid in rotating the downhole mud motor with the bit engaged with the formation. Further, using the calculated Δp _ump κw, the MSE is calculated as follows: MSE _conventional on = (3,380.7 * Δ _Pump κw ) / (D ² * ROP)

[0041] In another situation, drilling is done with both a downhole mud motor and a surface rotator (rt/td) simultaneously. Then, with direct measurement of both rotational and incremental hydraulic power used by the downhole mud motor, the formula for MSE is:

MSE _combined = (3,380.7 * (KW _rWd + Δ _PumpK w)) / (D ² * ROP)

[0042] In yet another situation the hydraulic power imparted to the formation by the mud pumps acting with the bit jets is taken into account. However an "MSE TOTAL" or "figure of merit" corresponding to an intrinsic definition of MSE can be of value and is determined from the measured KWs as follows:

MSE _Total = (3,380.7 * (KW _rt/td + KW _{0n bottom} )) / (D ² * ROP)

[0043] This MSEj _ota i takes into account the power imparted to the formation by the action of the mud pumps pumping mud through the jets. Thus, using voltage and amperage measurements, MSE is determined for a drilling operation. In certain aspects, using the same measurements of electrical energy inputs for the mud pump motors, MSE is determined for a downhole-motor drilling operation. When two or three of these drilling modes are employed together, a combined MSE taking into account energy input for each mode is determined. All of these determinations can be done without taking into account and without the need for measuring the speed of a rotary table, the speed of a top drive shaft, and the actual torque applied to a bit. The last of these methods according to embodiments described herein also takes into account the energy input associated with energy expended through the downhole motor's fluid jets. Certain known methods do not take into account the hydraulic horsepower of mud flow across a drill bit's jets, however, since certain methods described herein are cognizant of the energy supplied to the mud pumps, this energy expended in the drilling operation can, according to embodiments described herein, be considered. [0044] Figure 3 presents a summary of the methods in accordance with the principles described herein for the various situations described above. Optionally, the methods described may be used for a milling operation, a reaming operation, or for similar operations. [0045] Select embodiments described herein provide methods for determining mechanical specific energy for a wellbore operation, the method including measuring power input to machines used in the operation, e.g., a wellbore drilling operation and producing a value for input power, and calculating mechanical specific energy for the operation based on the value for the input power. Such methods may have one or some (in any possible combination) of the following: wherein the wellbore operation is a drilling operation; wherein the power input is electrical power and the value for input power is a value for electrical power; wherein the power input is hydraulic power and the value for input power is a value for hydraulic power; wherein the machines include a rotator for rotating tubulars used in the wellbore operation; wherein the rotator is at least one of rotary table system, top drive system, and mud motor system; wherein measuring the power input includes measuring power for a mud pump system and power for at least one rotator for rotating tubulars used in the wellbore operation; wherein the at least one rotator is all rotators used for rotating tubulars used in the wellbore operation; wherein the wellbore operation is a wellbore drilling operation using only either a rotary table system or a top drive system and Mechanical Specific Energy, MSE, is calculated according to the equation,

MSE _conventional = (3,380.7 * KW _rt/td ) / (D ² * ROP) in which "KW" is input power measured in kilowatts; "D" is the diameter of the drill bit used; and "ROP" is rate of penetration of the drill bit through the formation; wherein the wellbore operation is a drilling operation using a downhole mud motor to rotate a drill bit to drill a wellbore and Mechanical Specific Energy, MSE, is calculated according to the equation,

ΔpumpKW ⁼ KW _0n bottom " KW _o ff bottom

MSE _conventional on = (3,380.7 * Δ _PumpK w ) / (D ² * ROP) in which "KW" is input power measured in kilowatts; "D" is the diameter of the drill bit used; and "ROP" is rate of penetration of the drill bit through the formation, and "Δp _ump κw" is the difference between kilowatts input to a mud pump system used in the wellbore drilling operation with the bit on-bottom ("KW on bottom"), and off-bottom of the wellbore ("KW off bottom); wherein the wellbore operation is a drilling operation using a rotator for rotating tubulars and a downhole mud motor to rotate a drill bit, and Mechanical Specific Energy, MSE, is calculated according to the equation,

MSE _combine d = (3,380.7 * (KW _rt/td + Δ _PumpK w)) / (D ² * ROP) in which "KW" is input power measured in kilowatts; "D" is the diameter of the drill bit used; and "ROP" is rate of penetration of the drill bit through the formation, and "Δp _ump κw" is the difference between kilowatts input to a mud pump system used in the wellbore drilling operation with the bit on-bottom ("KW _0n bottom") _* and off-bottom of the wellbore ("KWoff bottom); wherein the wellbore operation is a drilling operation and the wellbore is being drilled with a downhole mud motor using an hydraulically powered mud pump system which inputs power to a formation being drilled via mud pumped through a drill bit being used to drill the wellbore, and Mechanical Specific Energy, MSE, is calculated according to the equation:

MSE _Total = (3,380.7 * (KW _rt/td + KW _{0n bottom} )) / (D ² * ROP) in which "KW" is input power measured in kilowatts; "D" is the diameter of the drill bit used; and "ROP" is rate of penetration of the drill bit through the formation, and "KW _0n bottom" is power input to the downhole mud motor; supply power to the machines with a rig power system; wherein the wellbore operation is a drilling operation and Mechanical Specific Energy, MSE, is calculated according to the equation:

MSE = (r)(Power)/(D ² )(ROP) in which "r" is a constant for converting units of power to units of MSE, Power is energy input to the machines used in the operation, "D" is diameter of a bit used for the drilling; and

ROP is rate of penetration of the bit into a formation being drilled; wherein said calculating is done in real time; controlling the measuring and the calculating with a control system; and/or displaying calculated MSE in real time.

[0046] At least some embodiments described herein therefore provide a computer-readable media having computer executable instructions for a method in accordance with the principles described herein, the computer-executable instructions performing a step or steps of the method.

[0047] At least some embodiments described herein therefore provide a computing unit configured to read and perform the computer-executable instructions on computer-readable media according to embodiments described herein.

[0048] At least some embodiments described herein therefore provide a method wherein the wellbore operation is a wellbore drilling operation and Mechanical Specific Energy, MSE, is calculated according to the equation:

MSE = (r)(Power)/(D ² )(ROP) in which "r" is a constant for converting units of power to units of MSE; Power is energy input to machines for a wellbore operation; "D" is diameter of a bit used for the drilling; operation (e.g. drilling); and ROP is rate of penetration of the bit into a formation being drilled (or of a mill into an item being milled or of a wellbore being reamed). [0049] In conclusion, therefore, it is seen that embodiments disclosed herein and covered by the appended claims are well adapted to carry out the objectives and obtain the ends set forth. While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.