Patent Publication Number: US-11661832-B2

Title: Systems and methods to autonomously operate hydraulic fracturing units

Description:
PRIORITY CLAIM 
     This is a continuation of U.S. Non-Provisional application Ser. No. 17/942,382, filed Sep. 12, 2022, titled “SYSTEMS AND METHODS TO AUTONOMOUSLY OPERATE HYDRAULIC FRACTURING UNITS,” which is a continuation of U.S. Non-Provisional application Ser. No. 17/173,320, filed Feb. 11, 2021, titled “SYSTEMS AND METHODS TO AUTONOMOUSLY OPERATE HYDRAULIC FRACTURING UNITS,” now U.S. Pat. No. 11,473,413, issued Oct. 18, 2022, which claims priority to and the benefit of U.S. Provisional Application No. 62/705,354, filed Jun. 23, 2020, titled “SYSTEMS AND METHODS TO AUTONOMOUSLY OPERATE HYDRAULIC FRACTURING UNITS,” the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to systems and methods for operating hydraulic fracturing units and, more particularly, to systems and methods for autonomously operating hydraulic fracturing units to pump fracturing fluid into a wellhead. 
     BACKGROUND 
     Hydraulic fracturing is an oilfield operation that stimulates the production of hydrocarbons, such that the hydrocarbons may more easily or readily flow from a subsurface formation to a well. For example, a hydraulic fracturing system may be configured to fracture a formation by pumping a fracturing fluid into a well at high pressure and high flow rates. Some fracturing fluids may take the form of a slurry including water, proppants, and/or other additives, such as thickening agents and/or gels. The slurry may be forced via one or more pumps into the formation at rates faster than can be accepted by the existing pores, fractures, faults, or other spaces within the formation. As a result, pressure may build rapidly to the point where the formation may fail and may begin to fracture. By continuing to pump the fracturing fluid into the formation, existing fractures in the formation are caused to expand and extend in directions away from a well bore, thereby creating additional flow paths to the well bore. The proppants may serve to prevent the expanded fractures from closing or may reduce the extent to which the expanded fractures contract when pumping of the fracturing fluid is ceased. Once the formation is fractured, large quantities of the injected fracturing fluid may be allowed to flow out of the well, and the production stream of hydrocarbons may be obtained from the formation. 
     Prime movers may be used to supply power to hydraulic fracturing pumps for pumping the fracturing fluid into the formation. For example, a plurality of gas turbine engines and/or reciprocating-piston engines may each be mechanically connected to a corresponding hydraulic fracturing pump via a transmission and operated to drive the hydraulic fracturing pump. The prime mover, hydraulic fracturing pump, transmission, and auxiliary components associated with the prime mover, hydraulic fracturing pump, and transmission may be connected to a common platform or trailer for transportation and set-up as a hydraulic fracturing unit at the site of a fracturing operation, which may include up to a dozen or more of such hydraulic fracturing units operating together to perform the fracturing operation. 
     Partly due to the large number of components of a hydraulic fracturing system, it may be difficult to efficiently and effectively control the output of the numerous hydraulic fracturing units and related components. For example, at times during a fracturing operation, there may be an excess or deficit of power available to perform the fracturing operation. Thus, when excess power exists, efficiency may be reduced by operating more of the hydraulic fracturing units than necessary to perform the fracturing operation. Alternatively, an operator of the hydraulic fracturing system may idle one or more of the hydraulic fracturing units to save energy. However, operating the prime movers at idle for an extended period of time may result in premature wear of the prime mover requiring more frequent maintenance. If, alternatively, a deficit of available power exists, an operator may cause the prime movers to operate at maximum power (or close to maximum power), which may lead to premature wear or failure of the prime mover, resulting in maintenance or replacement, as well as undesirable down time for the fracturing operation. In addition, because the conditions associated with a fracturing operation may often change during the fracturing operation, the power necessary to continue the fracturing operation may change over time, resulting in changes in the required power output to perform the fracturing operation. In such situations, it may be difficult for an operator to continuously monitor and change the outputs of the prime movers according to the changing conditions. 
     Accordingly, Applicant has recognized a need for systems and methods that provide improved operation of hydraulic fracturing units during hydraulic fracturing operations. The present disclosure may address one or more of the above-referenced drawbacks, as well as other possible drawbacks. 
     SUMMARY 
     As referenced above, due to the complexity of a hydraulic fracturing operation and the high number of machines involved, it may be difficult to efficiently and effectively control the power output of the prime movers and related components to perform the hydraulic fracturing operation, particularly during changing conditions. In addition, manual control of the hydraulic fracturing units by an operator may result in delayed or ineffective responses to instances of excesses and deficits of available power of the prime movers occurring during the hydraulic fracturing operation. Insufficiently prompt responses to such events may lead to inefficiencies or premature equipment wear or damage, which may reduce efficiency and lead to delays in completion of a hydraulic fracturing operation. 
     The present disclosure generally is directed to systems and methods for semi- or fully-autonomously operating hydraulic fracturing units to pump fracturing fluid into a wellhead. For example, in some embodiments, the systems and methods may provide semi- or fully-autonomous operation of a plurality of hydraulic fracturing units, for example, including controlling the power output of prime movers of the hydraulic fracturing units during operation of the plurality of hydraulic fracturing units for completion of a hydraulic fracturing operation. 
     According to some embodiments, a method of operating a plurality of hydraulic fracturing units, each of the hydraulic fracturing units including a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump, may include receiving, at a power output controller, one or more operational signals indicative of operational parameters associated with pumping fracturing fluid into a wellhead according to performance of a hydraulic fracturing operation. The method also may include determining, via the power output controller based at least in part on the one or more operational signals, an amount of required fracturing power sufficient to perform the hydraulic fracturing operation. The method further may include receiving, at the power output controller, one or more characteristic signals indicative of fracturing unit characteristics associated with at least some of the plurality of hydraulic fracturing units. The method still further may include determining, via the power output controller based at least in part on the one or more characteristic signals, an available power to perform the hydraulic fracturing operation. The method also may include determining, via the power output controller, a power difference between the available power and the required power, and controlling operation of the at least some of the plurality of hydraulic fracturing units based at least in part on the power difference. 
     According some embodiments, a hydraulic fracturing control assembly to operate a plurality of hydraulic fracturing units, each of the hydraulic fracturing units including a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump, may include an input device configured to facilitate communication of one or more operational signals indicative of operational parameters associated with pumping fracturing fluid into a wellhead according to performance of a hydraulic fracturing operation. The hydraulic fracturing control assembly also may include one or more sensors configured to generate one or more sensor signals indicative of one or more of a flow rate of fracturing fluid or a pressure associated with fracturing fluid. The hydraulic fracturing control assembly further may include a power output controller in communication with one or more of the plurality of hydraulic fracturing units, the input device, or the one or more sensors. The power output controller may be configured to receive the one or more operational signals indicative of operational parameters associated with pumping fracturing fluid into a wellhead according to performance of a hydraulic fracturing operation. The power output controller also may be configured to determine, based at least in part on the one or more operational signals, an amount of required fracturing power sufficient to perform the hydraulic fracturing operation. The power output controller further may be configured to receive one or more characteristic signals indicative of fracturing unit characteristics associated with at least some of the plurality of hydraulic fracturing units. The power output controller still further may be configured to determine, based at least in part on the one or more characteristic signals, an available power to perform the hydraulic fracturing operation, and determine a power difference between the available power and the required power. The power output controller also may be configured to control operation of the at least some of the plurality of hydraulic fracturing units based at least in part on the power difference. 
     According to some embodiments, a hydraulic fracturing system may include a plurality of hydraulic fracturing units. Each of the hydraulic fracturing units may include a hydraulic fracturing pump to pump fracturing fluid into a wellhead and an internal combustion engine to drive the hydraulic fracturing pump. The hydraulic fracturing system also may include an input device configured to facilitate communication of one or more operational signals indicative of operational parameters associated with pumping fracturing fluid into a wellhead according to performance of a hydraulic fracturing operation, and one or more sensors configured to generate one or more sensor signals indicative of one or more of a flow rate of fracturing fluid or a pressure associated with fracturing fluid. The hydraulic fracturing system also may include a power output controller in communication with one or more of the plurality of hydraulic fracturing units, the input device, or the one or more sensors. The power output controller may be configured to receive the one or more operational signals indicative of operational parameters associated with pumping fracturing fluid into a wellhead according to performance of a hydraulic fracturing operation. The power output controller also may be configured to determine, based at least in part on the one or more operational signals, an amount of required fracturing power sufficient to perform the hydraulic fracturing operation. The power output controller further may be configured to receive one or more characteristic signals indicative of fracturing unit characteristics associated with at least some of the plurality of hydraulic fracturing units. The power output controller still further may be configured to determine, based at least in part on the one or more characteristic signals, an available power to perform the hydraulic fracturing operation. The power output controller also may be configured to determine a power difference between the available power and the required power, and control operation of the at least some of the plurality of hydraulic fracturing units based at least in part on the power difference. 
     Still other aspects and advantages of these exemplary embodiments and other embodiments, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Accordingly, these and other objects, along with advantages and features of the present invention herein disclosed, will become apparent through reference to the following description and the accompanying drawings. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the embodiments of the present disclosure, are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure, and together with the detailed description, serve to explain principles of the embodiments discussed herein. No attempt is made to show structural details of this disclosure in more detail than can be necessary for a fundamental understanding of the embodiments discussed herein and the various ways in which they can be practiced. According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings can be expanded or reduced to more clearly illustrate embodiments of the disclosure. 
         FIG.  1    schematically illustrates an example hydraulic fracturing system including a plurality of hydraulic fracturing units, and including a block diagram of a hydraulic fracturing control assembly according to embodiments of the disclosure. 
         FIG.  2    is a block diagram of an example hydraulic fracturing control assembly according to an embodiment of the disclosure. 
         FIG.  3    is a block diagram of an example method of operating a plurality of hydraulic fracturing units according to embodiments of the disclosure. 
         FIG.  4 A  is a block diagram of an example method of operating a plurality of hydraulic fracturing units according to embodiments of the disclosure. 
         FIG.  4 B  is a continuation of the block diagram of the example method of operating a plurality of hydraulic fracturing units shown in  FIG.  4 A , according to embodiments of the disclosure. 
         FIG.  4 C  is a continuation of the block diagram of the example method of operating a plurality of hydraulic fracturing units shown in  FIGS.  4 A and  4 B , according to embodiments of the disclosure. 
         FIG.  4 D  is a continuation of the block diagram of the example method of operating a plurality of hydraulic fracturing units shown in  FIGS.  4 A,  4 B, and  4 C , according to embodiments of the disclosure. 
         FIG.  4 E  is a continuation of the block diagram of the example method of operating a plurality of hydraulic fracturing units shown in  FIGS.  4 A,  4 B,  4 C, and  4 D , according to embodiments of the disclosure. 
         FIG.  4 F  is a continuation of the block diagram of the example method of operating a plurality of hydraulic fracturing units shown in  FIGS.  4 A,  4 B,  4 C,  4 D, and  4 E , according to embodiments of the disclosure. 
         FIG.  5    is a schematic diagram of an example power output controller configured to operate a plurality of hydraulic fracturing units according to embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The drawings include like numerals to indicate like parts throughout the several views, the following description is provided as an enabling teaching of exemplary embodiments, and those skilled in the relevant art will recognize that many changes may be made to the embodiments described. It also will be apparent that some of the desired benefits of the embodiments described can be obtained by selecting some of the features of the embodiments without utilizing other features. Accordingly, those skilled in the art will recognize that many modifications and adaptations to the embodiments described are possible and may even be desirable in certain circumstances. Thus, the following description is provided as illustrative of the principles of the embodiments and not in limitation thereof. 
     The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term “plurality” refers to two or more items or components. The terms “comprising,” “including,” “carrying,” “having,” “containing,” and “involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean “including but not limited to,” unless otherwise stated. Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. The transitional phrases “consisting of” and “consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to any claims. Use of ordinal terms such as “first,” “second,” “third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish claim elements. 
       FIG.  1    schematically illustrates a top view of an example hydraulic fracturing system  10  including a plurality of hydraulic fracturing units  12 , and including a block diagram of a hydraulic fracturing control assembly  14  according to embodiments of the disclosure. In some embodiments, one or more of the hydraulic fracturing units  12  may include a hydraulic fracturing pump  16  driven by an internal combustion engine  18 , such as a gas turbine engine or a reciprocating-piston engine and/or a non-gas turbine engine, such as a reciprocating-piston diesel engine. For example, in some embodiments, each of the hydraulic fracturing units  12  may include a directly-driven turbine (DDT) hydraulic fracturing pump  16 , in which the hydraulic fracturing pump  16  is connected to one or more GTEs that supply power to the respective hydraulic fracturing pump  16  for supplying fracturing fluid at high pressure and high flow rates to a formation. For example, the GTE may be connected to a respective hydraulic fracturing pump  16  via a transmission  20  (e.g., a reduction transmission) connected to a drive shaft, which, in turn, is connected to a driveshaft or input flange of a respective hydraulic fracturing pump  16 , which may be a reciprocating hydraulic fracturing pump. Other types of engine-to-pump coupling arrangements are contemplated. 
     In some embodiments, one or more of the GTEs may be a dual-fuel or bi-fuel GTE, for example, capable of being operated using of two or more different types of fuel, such as natural gas and diesel fuel, although other types of fuel are contemplated. For example, a dual-fuel or bi-fuel GTE may be capable of being operated using a first type of fuel, a second type of fuel, and/or a combination of the first type of fuel and the second type of fuel. For example, the fuel may include gaseous fuels, such as, for example, compressed natural gas (CNG), natural gas, field gas, pipeline gas, methane, propane, butane, and/or liquid fuels, such as, for example, diesel fuel (e.g., #2 diesel), bio-diesel fuel, bio-fuel, alcohol, gasoline, gasohol, aviation fuel, and other fuels as will be understood by those skilled in the art. Gaseous fuels may be supplied by CNG bulk vessels, a gas compressor, a liquid natural gas vaporizer, line gas, and/or well-gas produced natural gas. Other types and associated fuel supply sources are contemplated. The one or more internal combustion engines  18  may be operated to provide horsepower to drive the transmission  20  connected to one or more of the hydraulic fracturing pumps  16  to safely and successfully fracture a formation during a well stimulation project or fracturing operation. 
     In some embodiments, the fracturing fluid may include, for example, water, proppants, and/or other additives, such as thickening agents and/or gels. For example, proppants may include grains of sand, ceramic beads or spheres, shells, and/or other particulates, and may be added to the fracturing fluid, along with gelling agents to create a slurry as will be understood by those skilled in the art. The slurry may be forced via the hydraulic fracturing pumps  16  into the formation at rates faster than can be accepted by the existing pores, fractures, faults, or other spaces within the formation. As a result, pressure may build rapidly to the point where the formation fails and begins to fracture. By continuing to pump the fracturing fluid into the formation, existing fractures in the formation may be caused to expand and extend in directions away from a well bore, thereby creating additional flow paths to the well. The proppants may serve to prevent the expanded fractures from closing or may reduce the extent to which the expanded fractures contract when pumping of the fracturing fluid is ceased. Once the well is fractured, large quantities of the injected fracturing fluid may be allowed to flow out of the well, and the water and any proppants not remaining in the expanded fractures may be separated from hydrocarbons produced by the well to protect downstream equipment from damage and corrosion. In some instances, the production stream may be processed to neutralize corrosive agents in the production stream resulting from the fracturing process. 
     In the example shown in  FIG.  1   , the hydraulic fracturing system  10  may include one or more water tanks  22  for supplying water for fracturing fluid, one or more chemical additive units  24  for supplying gels or agents for adding to the fracturing fluid, and one or more proppant tanks  26  (e.g., sand tanks) for supplying proppants for the fracturing fluid. The example fracturing system  10  shown also includes a hydration unit  28  for mixing water from the water tanks  22  and gels and/or agents from the chemical additive units  24  to form a mixture, for example, gelled water. The example shown also includes a blender  30 , which receives the mixture from the hydration unit  28  and proppants via conveyers  32  from the proppant tanks  26 . The blender  30  may mix the mixture and the proppants into a slurry to serve as fracturing fluid for the hydraulic fracturing system  10 . Once combined, the slurry may be discharged through low-pressure hoses  34 , which convey the slurry into two or more low-pressure lines  36  in a frac manifold  38 . In the example shown, the low-pressure lines  36  in the frac manifold  38  feed the slurry to the hydraulic fracturing pumps  16  through low-pressure suction hoses  40 . 
     The hydraulic fracturing pumps  16 , driven by the respective internal combustion engines  18 , discharge the slurry (e.g., the fracturing fluid including the water, agents, gels, and/or proppants) at high flow rates and/or high pressures through individual high-pressure discharge lines  42  into two or more high-pressure flow lines  44 , sometimes referred to as “missiles,” on the fracturing manifold  38 . The flow from the high-pressure flow lines  44  is combined at the fracturing manifold  38 , and one or more of the high-pressure flow lines  44  provide fluid flow to a manifold assembly  46 , sometimes referred to as a “goat head.” The manifold assembly  46  delivers the slurry into a wellhead manifold  48 . The wellhead manifold  48  may be configured to selectively divert the slurry to, for example, one or more wellheads  50  via operation of one or more valves. Once the fracturing process is ceased or completed, flow returning from the fractured formation discharges into a flowback manifold, and the returned flow may be collected in one or more flowback tanks as will be understood by those skilled in the art. 
     As schematically depicted in  FIG.  1   , one or more of the components of the fracturing system  10  may be configured to be portable, so that the hydraulic fracturing system  10  may be transported to a well site, quickly assembled, operated for a relatively short period of time until completion of a fracturing operation, at least partially disassembled, and transported to another location of another well site for use. For example, the components may be carried by trailers and/or incorporated into trucks, so that they may be easily transported between well sites. 
     As shown in  FIG.  1   , some embodiments of the hydraulic fracturing system  10  may include one or more electrical power sources  52  configured to supply electrical power for operation of electrically powered components of the hydraulic fracturing system  10 . For example, one or more of the electrical power sources  52  may include an internal combustion engine  54  (e.g., a GTE or a non-GTE engine, such as a reciprocating-piston engine) provided with a source of fuel (e.g., gaseous fuel and/or liquid fuel) and configured to drive a respective electrical power generation device  56  to supply electrical power to the hydraulic fracturing system  10 . In some embodiments, one or more of the hydraulic fracturing units  12  may include electrical power generation capability, such as an auxiliary internal combustion engine and an auxiliary electrical power generation device driven by the auxiliary internal combustion engine. As shown is  FIG.  1   , some embodiments of the hydraulic fracturing system  10  may include electrical power lines  56  for supplying electrical power from the one or more electrical power sources  52  to one or more of the hydraulic fracturing units  12 . 
     Some embodiments also may include a data center  60  configured to facilitate receipt and transmission of data communications related to operation of one or more of the components of the hydraulic fracturing system  10 . Such data communications may be received and/or transmitted via hard-wired communications cables and/or wireless communications, for example, according to known communications protocols as will be understood by those skilled in the art. For example, the data center  60  may contain at least some components of the hydraulic fracturing control assembly  14 , such as a power output controller  62  configured to receive signals from components of the hydraulic fracturing system  10  and/or communicate control signals to components of the hydraulic fracturing system  10 , for example, to at least partially control operation of one or more components of the hydraulic fracturing system  10 , such as, for example, the internal combustion engines  18 , the transmissions  20 , and/or the hydraulic fracturing pumps  16  of the hydraulic fracturing units  12 , the chemical additive units  24 , the hydration units  28 , the blender  30 , the conveyers  32 , the fracturing manifold  38 , the manifold assembly  46 , the wellhead manifold  48 , and/or any associated valves, pumps, and/or other components of the hydraulic fracturing system  10 . 
       FIGS.  1  and  2    also include block diagrams of example hydraulic fracturing control assemblies  14  according to embodiments of the disclosure. Although  FIGS.  1  and  2    depict certain components as being part of the example hydraulic fracturing control assemblies  14 , one or more of such components may be separate from the hydraulic fracturing control assemblies  14 . In some embodiments, the hydraulic fracturing control assembly  14  may be configured to semi- or fully-autonomously monitor and/or control operation of one or more of the hydraulic fracturing units  12  and/or other components of the hydraulic fracturing system  10 , for example, as described herein. For example, the hydraulic fracturing control assembly  14  may be configured to operate a plurality of the hydraulic fracturing units  12 , each of which may include a hydraulic fracturing pump  16  to pump fracturing fluid into a wellhead  50  and an internal combustion engine  18  to drive the hydraulic fracturing pump  16  via the transmission  20 . 
     As shown in  FIGS.  1  and  2   , some embodiments of the hydraulic fracturing control assembly  14  may include an input device  64  configured to facilitate communication of operational parameters  66  to the power output controller  62 . In some embodiments, the input device  64  may include a computer configured to provide one or more operational parameters  66  to the power output controller  62 , for example, from a location remote from the hydraulic fracturing system  10  and/or a user input device, such as a keyboard linked to a display associated with a computing device, a touchscreen of a smartphone, a tablet, a laptop, a handheld computing device, and/or other types of input devices. In some embodiments, the operational parameters  66  may include, but are not limited to, a target flow rate, a target pressure, a maximum flow rate, a maximum available power output, and/or a minimum flow rate associated with fracturing fluid supplied to the wellhead  50 . In some examples, one or more operators associated with a hydraulic fracturing operation performed by the hydraulic fracturing system  10  may provide one more of the operational parameters  66  to the power output controller  62 , and/or one or more of the operational parameters  66  may be stored in computer memory and provided to the power output controller  62  upon initiation of at least a portion of the hydraulic fracturing operation. 
     For example, an equipment profiler (e.g., a fracturing unit profiler) may calculate, record, store, and/or access data related each of the hydraulic fracturing units  12  including fracturing unit characteristics  70 , which may include, but not limited to, fracturing unit data including, maintenance data associated with the hydraulic fracturing units  12  (e.g., maintenance schedules and/or histories associated with the hydraulic fracturing pump  16 , the internal combustion engine  18 , and/or the transmission  20 ), operation data associated with the hydraulic fracturing units  12  (e.g., historical data associated with horsepower (e.g., hydraulic horsepower), fluid pressures, fluid flow rates, etc. associated with operation of the hydraulic fracturing units  12 ), data related to the transmissions  20  (e.g., hours of operation, efficiency, and/or installation age), data related to the internal combustion engines  18  (e.g., hours of operation, maximum rated available power output (e.g., hydraulic horsepower), and/or installation age), information related to the hydraulic fracturing pumps  16  (e.g., hours of operation, plunger and/or stroke size, maximum speed, efficiency, health, and/or installation age), equipment health ratings (e.g., pump, engine, and/or transmission condition), and/or equipment alarm history (e.g., life reduction events, pump cavitation events, pump pulsation events, and/or emergency shutdown events). In some embodiments, the fracturing unit characteristics  70  may include, but are not limited to minimum flow rate, maximum flow rate, harmonization rate, pump condition, and/or the maximum available power output  71  (e.g., the maximum rated available power output (e.g., hydraulic horsepower) of the internal combustion engines  18 . 
     In the embodiments shown in  FIGS.  1  and  2   , the hydraulic fracturing control assembly  14  may also include one or more sensors  72  configured to generate one or more sensor signals  74  indicative of a flow rate of fracturing fluid supplied by a respective one of the hydraulic fracturing pump  16  of a hydraulic fracturing unit  12  and/or supplied to the wellhead  50 , a pressure associated with fracturing fluid provided by a respective hydraulic fracturing pump  16  of a hydraulic fracturing unit  12  and/or supplied to the wellhead  50 , and/or an engine speed associated with operation of a respective internal combustion engine  18  of a hydraulic fracturing unit  12 . For example, one or more sensors  72  may be connected to one or more of the hydraulic fracturing units  12  and may be configured to generate signals indicative of a fluid pressure supplied by an individual hydraulic fracturing pump  16  of a hydraulic fracturing unit  12 , a flow rate associated with fracturing fluid supplied by a hydraulic fracturing pump  16  of a hydraulic fracturing unit  12 , and/or an engine speed of an internal combustion engine  18  of a hydraulic fracturing unit  12 . In some examples, one or more of the sensors  72  may be connected to the wellhead  50  and may be configured to generate signals indicative of fluid pressure of hydraulic fracturing fluid at the wellhead  50  and/or a flow rate associated with the fracturing fluid at the wellhead  50 . Other sensors (e.g., other sensor types for providing similar or different information) at the same or other locations of the hydraulic fracturing system  10  are contemplated. 
     As shown in  FIG.  2   , in some embodiments, the hydraulic fracturing control assembly  14  also may include one or more blender sensors  76  associated with the blender  30  and configured to generate blender signals  78  indicative of an output of the blender  30 , such as, for example, a flow rate and/or a pressure associated with fracturing fluid supplied to the hydraulic fracturing units  12  by the blender  30 . Operation of one or more of the hydraulic fracturing units  12  may be controlled, for example, to prevent the hydraulic fracturing units  12  from supplying a greater flow rate of fracturing fluid to the wellhead  50  than the flow rate of fracturing fluid supplied by the blender  30 , which may disrupt the fracturing operation and/or damage components of the hydraulic fracturing units  12  (e.g., the hydraulic fracturing pumps  16 ). 
     As shown in  FIGS.  1  and  2   , some embodiments of the hydraulic fracturing control assembly  14  may include the power output controller  62 , which may be in communication with the plurality of hydraulic fracturing units  12 , the input device  64 , and/or one or more of the sensors  72  and/or  76 . For example, communications may be received and/or transmitted between the power output controller  62 , the hydraulic fracturing units  12 , and/or the sensors  72  and/or  76 , via hard-wired communications cables and/or wireless communications, for example, according to known communications protocols, as will be understood by those skilled in the art. 
     In some embodiments, the power output controller  62  may be configured to receive one or more operational parameters  66  associated with pumping fracturing fluid into the one or more wellheads  50 . For example, the operational parameters  66  may include a target flow rate, a target pressure, a maximum pressure, a maximum flow rate, a duration of fracturing operation, a volume of fracturing fluid to supply to the wellhead  50 , and/or a total work performed during the fracturing operation, etc. The power output controller  62  also may be configured to receive one or more fracturing unit characteristics  70 , for example, associated with each of the hydraulic fracturing pumps  16  and/or the internal combustion engines  18  of the respective hydraulic fracturing units  12 . As described previously herein, in some embodiments, the fracturing unit characteristics  70  may include a minimum flow rate, a maximum flow rate, a harmonization rate, a pump condition  82  (individually or collectively), an internal combustion engine condition, a maximum power output of the internal combustion engines  18  (e.g., the maximum rated power output) provided by the corresponding hydraulic fracturing pump  16  and/or internal combustion engine  18  of a respective hydraulic fracturing unit  12 . The fracturing unit characteristics  70  may be provided by an operator, for example, via the input device  64  and/or via a fracturing unit profiler, as described previously herein. 
     In some embodiments, the power output controller  62  may be configured to determine whether the hydraulic fracturing units  12  have a capacity sufficient to achieve the operational parameters  66 . For example, the power output controller  62  may be configured to make such determinations based at least in part on one or more of the fracturing unit characteristics  70 , which the power output controller  62  may use to calculate (e.g., via summation) the collective capacity of the hydraulic fracturing units  12  to supply a sufficient flow rate and/or a sufficient pressure to achieve the operational parameters  66  at the wellhead  50 . For example, the power output controller  62  may be configured to determine an available power to perform the hydraulic fracturing operation (e.g., hydraulic horsepower) and/or a total pump flow rate by combining at least one of the fracturing unit characteristics  70  for each of the plurality of hydraulic fracturing pumps  16  and/or internal combustion engines  18 , and comparing the available power to a required fracturing power sufficient to perform the hydraulic fracturing operation. In some embodiments, determining the available power may include adding the maximum available power output of each of the internal combustion engines  18 . 
     In some embodiments, the power output controller  62  may be configured to receive one or more operational signals indicative of operational parameters  66  associated with pumping fracturing fluid into a wellhead  50  according to performance of a hydraulic fracturing operation. The power output controller  62  also may be configured to determine, based at least in part on the one or more operational signals, an amount of required fracturing power sufficient to perform the hydraulic fracturing operation. The power output controller  62  further may be configured to receive one or more characteristic signals indicative of the fracturing unit characteristics  70  associated with at least some of the plurality of hydraulic fracturing units  12 . The power output controller  62  still further may be configured to determine, based at least in part on the one or more characteristic signals, an available power to perform the hydraulic fracturing operation. The power output controller  62  also may be configured to determine a power difference between the available power and the required power, and control operation of the at least some of the hydraulic fracturing units  12  (e.g., including the internal combustion engines  18 ) based at least in part on the power difference. 
     In some embodiments, the power output controller  62  may be configured to cause one or more of the at least some hydraulic fracturing units  12  to idle during the fracturing operation, for example, when the power difference is indicative of excess power available to perform the hydraulic fracturing operation. For example, the power output controller  62  may be configured to generate one or more power output control signals  84  to control operation of the hydraulic fracturing units  12 , including the internal combustion engines  18 . In some embodiments, the power output controller  62  may be configured to idle at least a first one of the hydraulic fracturing units  12  (e.g., the associated internal combustion engine  18 ) while operating at least a second one of the hydraulic fracturing units  12 , wait a period of time, and idle at least a second one of the hydraulic fracturing units while operating the first one of the hydraulic fracturing units  12 . For example, the power output controller  62  may be configured to cause alternating between idling and operation of the hydraulic fracturing units  12  to reduce idling time for any one of the hydraulic fracturing units. This may reduce or prevent wear and/or damage to the internal combustion engines  18  of the associated hydraulic fracturing units  12  due to extended idling periods. 
     In some embodiments, the power output controller  62  may be configured to receive one or more wellhead signals  74  indicative of a fracturing fluid pressure at the wellhead  50  and/or a fracturing fluid flow rate at the wellhead  50 , and control idling and operation of the at least some hydraulic fracturing units based at least in part on the one or more wellhead signals  74 . In this example manner, the power output controller  62  may be able to dynamically adjust (e.g., semi- or fully-autonomously) the power outputs of the respective hydraulic fracturing units  12  in response to changing conditions associated with pumping fracturing fluid into the wellhead  50 . This may result in relatively more responsive and/or more efficient operation of the hydraulic fracturing system  10  as compared to manual operation by one or more operators, which in turn, may reduce machine wear and/or machine damage. 
     In some embodiments, when the power difference is indicative of a power deficit to perform the hydraulic fracturing operation, the power output controller  62  may be configured to increase a power output of one or more of the hydraulic fracturing units  12 , which in some embodiments may include respective gas turbine engines (e.g., the associated internal combustion engine  18 ) to supply power to a respective hydraulic fracturing pump  14  of a respective hydraulic fracturing unit  12 . For example, the power output controller  62  may be configured to increase the power output of the hydraulic fracturing units  12  including a gas turbine engine by increasing the power output from a first power output ranging from about 80% to about 95% of maximum rated power output (e.g., about 90% of the maximum rated power output) to a second power output ranging from about 90% to about 110% of the maximum rated power output (e.g., about 105% or 108% of the maximum rated power output). 
     For example, in some embodiments, the power output controller  62  may be configured to increase the power output of the hydraulic fracturing units  12  including a gas turbine engine  18  by increasing the power output from a first power output ranging from about 80% to about 95% of maximum rated power output to a maximum continuous power (MCP) or a maximum intermittent power (MIP) available from the GTE-powered fracturing units  12 . In some embodiments, the MCP may range from about 95% to about 105% (e.g., about 100%) of the maximum rated power for a respective GTE-powered hydraulic fracturing unit  12 , and the MIP may range from about 100% to about 110% (e.g., about 105% or 108%) of the maximum rated power for a respective GTE-powered hydraulic fracturing unit  12 . 
     In some embodiments, for hydraulic fracturing units  12  including a non-GTE, such as a reciprocating-piston diesel engine, when the power difference is indicative of a power deficit to perform the hydraulic fracturing operation, the power output controller  62  may be configured to increase a power output of one or more of the hydraulic fracturing units  12  (e.g., the associated diesel engine) to supply power to a respective hydraulic fracturing pump  14  of a respective hydraulic fracturing unit  12 . For example, the power output controller  62  may be configured to increase the power output of the hydraulic fracturing units  12  including a diesel engine by increasing the power output from a first power output ranging from about 60% to about 90% of maximum rated power output (e.g., about 80% of the maximum rated power output) to a second power output ranging from about 70% to about 100% of the maximum rated power output (e.g., about 90% of the maximum rated power output). 
     In some embodiments, when the power difference is indicative of a power deficit to perform the hydraulic fracturing operation, the power output controller  62  may be configured to store operation data  86  associated with operation of hydraulic fracturing units  12  operated at an increased power output. Such operation data  86  may be communicated to one or more output devices  88 , for example, as previously described herein. In some examples, the operation data  86  may be communicated to a fracturing unit profiler for storage. The fracturing unit profiler, in some examples, may use at least a portion of the operation data  86  to update a fracturing unit profile for one or more of the hydraulic fracturing units  12 , which may be used as fracturing unit characteristics  70  for the purpose of future fracturing operations. 
     In some examples, the power output controller  62  may calculate the required hydraulic power required to complete the fracturing operation (e.g., one or more fracturing stage) and may receive fracturing unit data  68  from a fracturing unit profiler for each hydraulic fracturing unit  12 , for example, to determine the available power output. The fracturing unit profiler associated with each fracturing unit  12  may be configured to take into account any detrimental conditions the hydraulic fracturing unit  12  has experienced, such as cavitation or high pulsation events, and reduce the available power output of that hydraulic fracturing unit  12 . The reduced available power output may be used by the power output controller  62  when determining a total power output available from all the hydraulic fracturing units  12  of the hydraulic fracturing system  10 . The power output controller  62  may be configured to cause utilization of hydraulic fracturing units  12  including non-GTE-engines (e.g., reciprocating piston-diesel engines) at 80% of maximum power output (e.g., maximum rated power output), and hydraulic fracturing units including a GTE at 90% of maximum power output (e.g., maximum rated power output). The power output controller  62  may be configured to subtracts the total available power output by the required power output, and determine if it there is a power deficit or excess available power. If an excess of power is available, the power output controller  62  may be configured to cause some hydraulic fracturing units  12  to go to idle and only utilize hydraulic fracturing units  12  sufficient to achieve the previously mentioned power output percentages. Because, in some examples, operating the internal combustion engines  18  at idle for a prolonged period of time may not be advisable and may be detrimental to the health of the internal combustion engines  18 , the power output controller  62  may be configured to cause the internal combustion engines  18  to be idled for an operator-configurable time period before completely shutting down. 
     If there is a deficit of available power, the power output controller  62  may be configured to facilitate the provision of choices for selection by an operator for addressing the power output deficit, for example, via the input device  64 . For example, for hydraulic fracturing units  12  including a GTE, the GTE may be operated at maximum continuous power (e.g., 100% of the total power maximum power output) or at maximum intermittent power (MIP, e.g., ranging from about 105% to about 110% of the total maximum power output). If the increase the available power output is insufficient and other non-GTE-powered (e.g., diesel engine-powered) hydraulic fracturing units  12  are operating in combination with the GTE-powered hydraulic fracturing units  12 , the power output controller  62  may be configured to utilize additional non-GTE-powered hydraulic fracturing units  12  to achieve the required power output. 
     Because, in some examples, operating the hydraulic fracturing units  12  (e.g., the internal combustion engines  18 ) at elevated power output levels may increase maintenance cycles, which may be recorded in the associated hydraulic fracturing unit profiler and/or the power output controller  62 , during the hydraulic fracturing operation, the power output controller  62  may be configured to substantially continuously (or intermittently) provide a preferred power output utilization of the internal combustion engines  18  and may be configured to initiate operation of hydraulic fracturing units  12 , for example, to (1) reduce the power loading on the internal combustion engines  18  if an increase in fracturing fluid flow rate is required and/or (2) idle at least some of the internal combustion engines  18  if a reduction in fracturing fluid flow rate is experienced. In some examples, this operational strategy may increase the likelihood that the hydraulic fracturing units  12  are operated at a shared load and/or that a particular one or more of the hydraulic fracturing units  12  is not being over-utilized, which may result in premature maintenance and/or wear. It may not be desirable for operation hours for each of the hydraulic fracturing units  12  to be the same as one another, which might result in a substantially-simultaneous or concurrent fleet-wide maintenance being advisable, which would necessitate shut-down of the entire fleet for maintenance. In some embodiments, the power output controller  62  may be configured to stagger idling cycles associated with the hydraulic fracturing units  12  to reduce the likelihood or prevent maintenance being required substantially simultaneously. 
       FIGS.  3 ,  4 A,  4 B,  4 C,  4 D,  4 E, and  4 F  are block diagrams of example methods  300  and  400  of operating a plurality of hydraulic fracturing units according to embodiments of the disclosure, illustrated as a collection of blocks in a logical flow graph, which represent a sequence of operations. In the context of software, the blocks represent computer-executable instructions stored on one or more computer-readable storage media that, when executed by one or more processors, perform the recited operations. Generally, computer-executable instructions include routines, programs, objects, components, data structures, and the like that perform particular functions or implement particular data types. The order in which the operations are described is not intended to be construed as a limitation, and any number of the described blocks can be combined in any order and/or in parallel to implement the methods. 
       FIG.  3    depicts a flow diagram of an embodiment of a method  300  of operating a plurality of hydraulic fracturing units, according to an embodiment of the disclosure. For example, the example method  300  may be configured to control operation of one or more hydraulic fracturing units depending, for example, on an amount of available power from operation of the hydraulic fracturing units and an amount of required fracturing power sufficient to perform a hydraulic fracturing operation, for example, as previously described herein. 
     The example method  300 , at  302 , may include receiving one or more operational signals indicative of operational parameters associated with pumping fracturing fluid into a wellhead according to performance of a hydraulic fracturing operation. For example, an operator of the hydraulic fracturing system may use an input device to provide operational parameters associated with the fracturing operation. A power output controller may receive the operational parameters as a basis for controlling operation of the hydraulic fracturing units. 
     At  304 , the example method  300  further may include determining, via the power output controller based at least in part on the one or more operational signals, an amount of required fracturing power sufficient to perform the hydraulic fracturing operation. For example, the power output controller may be configured to calculate the total power output available based at least in part on fracturing unit characteristics received from a fracturing unit profiler, for example, as previously described herein. 
     At  306 , the example method  300  also may include receiving, at the power output controller, one or more characteristic signals indicative of fracturing unit characteristics associated with at least some of the plurality of hydraulic fracturing units, for example, as discussed herein. 
     At  308 , the example method  300  may also include determining, for example, via the power output controller, based at least in part on the one or more characteristic signals, an available power to perform the hydraulic fracturing operation, for example, as described previously herein. 
     The example method  300 , at  310 , also may include determining, for example, via the power output controller, a power difference between the available power and the required power, for example, as previously described herein. 
     At  312 , the example method  300  also may include determining, for example, via the power output controller, whether there is excess power available or a power deficit based on the power difference, for example, as described herein. 
     If, at  312 , it is determined that excess power is available, the example method  300 , at  314  may include causing one or more of the hydraulic fracturing units to idle during the fracturing operation, for example, as described herein. 
     At  316 , the example, method  300  may include alternating between idling and operation of the hydraulic fracturing units to reduce idling time for any one of the hydraulic fracturing units, for example, as previously described herein. Depending on, for example, changing conditions associated with the fracturing operation, this may be continued substantially until completion of the fracturing operation. For example, this may include receiving, for example, at the power output controller, one or more wellhead signals indicative of a fracturing fluid pressure at the wellhead and/or a fracturing fluid flow rate at the wellhead, and controlling idling and operation of the hydraulic fracturing units based at least in part on the one or more wellhead signals. 
     If at  312 , it is determined that a power deficit exists, the example method  300 , at  318 , may include receiving, for example, at the power output controller, one or more wellhead signals indicative of a fracturing fluid pressure at the wellhead and/or a fracturing fluid flow rate at the wellhead. 
     At  320 , the example method  300  may include increasing a power output of one or more of the hydraulic fracturing units, for example, as described previously herein. 
       FIGS.  4 A,  4 B,  4 C,  4 D,  4 E, and  4 F  depict a flow diagram of an embodiment of a method  400  of operating a plurality of hydraulic fracturing units, according to an embodiment of the disclosure. For example, the example method  400  may be configured to control operation of one or more hydraulic fracturing units depending, for example, on an amount of available power from operation of the hydraulic fracturing units and an amount of required fracturing power sufficient to perform a hydraulic fracturing operation, for example, as previously described herein. 
     The example method  400 , at  402 , may include receiving one or more operator mode signals indicative of an autonomous or a semi-autonomous operation mode associated with pumping fracturing fluid into a wellhead according to performance of a hydraulic fracturing operation. For example, an operator of the hydraulic fracturing system may use an input device to provide operator mode signals identifying the mode of operation of the hydraulic fracturing system as being either autonomous or semi-autonomous, for example, so that an operator of the hydraulic fracturing system does not need to manually adjust power outputs and/or fluid outputs of the hydraulic fracturing system on a regular basis during the fracturing operation. In some embodiments of the method  400 , a power output controller may receive the operator mode signals and, based at least in part on the operator mode signals, cause one or more of the hydraulic fracturing units to autonomously or semi-autonomously control the power output (e.g., the hydraulic horsepower output) and/or fluid output associated with one or more of the hydraulic fracturing units, for example, in response to the conditions of the fracturing operation dynamically changing, for example, as described herein. 
     At  404 , the example method  400  may include receiving one or more operational signals indicative of operational parameters associated with the fracturing operation. For example, an operator of the hydraulic fracturing system may use an input device to provide operational parameters associated with the fracturing operation. The power output controller may receive the operational parameters and use one or more of the operational parameters as a basis for controlling operation of the hydraulic fracturing units, for example, as previously described herein. In some embodiments, the operational signals may include the one or more operator mode signals mentioned above. 
     The example method  400 , at  406 , may include determining an amount of total fracturing power required (e.g., the total hydraulic horsepower required) to perform the hydraulic fracturing stage based at least in part on the operational parameters. For example, the power output controller may receive the operational parameters and calculate a total power required to complete the fracturing operation, for example, as described previously herein. 
     At  408 , the example method  400  may include receiving characteristic signals indicative of characteristics associated with one or more (e.g., each) of a plurality of hydraulic fracturing units. For example, one or more equipment profilers (e.g., pump profilers) associated with one or more of the hydraulic fracturing units may communicate information relating to performance capabilities and/or limitations of the one or more hydraulic fracturing units. For example, an equipment profiler (e.g., a pump profiler) associated with each of the hydraulic fracturing units may communicate information to the power output controller indicative of the power output and/or pumping capabilities of the respective hydraulic fracturing unit, for example, as described previously herein. 
     At  410 , the example method  400  may include determining the power output (e.g., the hydraulic horsepower) available for each of the hydraulic fracturing units based at least in part on the characteristic signals. For example, the power output controller, based at least in part on information included in the characteristic signals (e.g., the characteristics associated with the respective hydraulic fracturing unit), may be configured to calculate the power output and/or pumping capability of the respective hydraulic fracturing unit, for example, as described previously herein. 
     The example method  400 , at  412 , may include determining the total power output (e.g., the hydraulic horsepower output) available for all the hydraulic fracturing units based at least in part on the characteristic signals. For example, the power output controller may be configured to calculate the total power output available for all the operational hydraulic fracturing units by adding or summing the respective power output capabilities of each of the operational hydraulic fracturing units of the hydraulic fracturing system, for example, as previously described herein. In some embodiments, the total power output available may be determined based at least in part on the pump pressure provided during a previous job (e.g., an immediately previous job) multiplied by the maximum rate provided during the previous job. In some embodiments, the power output controller may be configured to calculate the total power output available by multiplying each of the respective rated maximum power outputs of each of the non-GTE-powered hydraulic fracturing units (e.g., the diesel-powered hydraulic fracturing units) by a non-GTE power factor (e.g., ranging from about 70% to about 90% (e.g., about 80%)) and summing each of the non-GTE power outputs to determine a total non-GTE-powered fracturing unit power output, and multiplying each of the respective rated maximum power outputs of each of the GTE-powered hydraulic fracturing units by a GTE power factor (e.g., ranging from about 85% to about 95% (e.g., about 90%)) and summing each of the GTE power outputs to determine a total GTE-powered fracturing unit power output. Thereafter, the power output controller may be configured to determine the total power output available for the hydraulic fracturing system by adding the total non-GTE power output to the total GTE power output. 
     At  414 , the example method  400  may include determining whether the total power output available is greater than or equal to the total fracturing power required. For example, the power output controller may be configured to subtract the total fracturing power required from the total power output available and determine whether the result is greater than or equal to zero. If not, example method may go to  440  (see  FIG.  4 C ). 
     If at  414 , it is determined that the total power output available is greater than or equal to the total fracturing power required, at  416 , the example method  400  may include determining the excess power available (if any). 
     At  418 , the example method  400  may include identifying hydraulic fracturing units that may be idled, for example, while the remaining operational hydraulic fracturing units have the capacity to provide the total fracturing power required. For example, if at  416 , it is determined that excess power is available, based at least in part on the characteristic signals received from the equipment profilers, the power output controller may be configured to identify the hydraulic fracturing units that may be idled while still having a sufficient amount of fracturing power available from the remaining (non-idled) hydraulic fracturing units to provide the total fracturing power required to successfully complete the fracturing operation (e.g., a fracturing stage). 
     At  420  ( FIG.  4 B ), the example method  400  may include determining whether the hydraulic fracturing units that can be idled are non-gas turbine engine (non-GTE)-powered (e.g., reciprocating-piston diesel-powered) or GTE-powered fracturing units. For example, the power output controller may be configured to determine whether the total fracturing power required can be provided solely by GTE-powered hydraulic fracturing units. In some embodiments, using only GTE-powered hydraulic fracturing may result in more efficient completion of the fracturing stage relative to the use of non-GTE-powered fracturing units, such as diesel-powered fracturing units. 
     If, at  420 , it is determined that GTE-powered fracturing units will be idled, at  422 , the example method  400  may include generating warning signal indicative that one or more GTE-powered hydraulic fracturing unit(s) are being idled. For example, the power output controller may be configured to generate such a warning signal, which may be communicated to an operator, for example, via a communication device, such as a visual display configured communicate the warning to the operator. The warning may be visual, audible, vibrational, haptic, or a combination thereof. 
     If, at  420 , it is determined that only non-GTE-powered hydraulic fracturing units will be idled, at  424 , the example method may include causing unneeded non-GTE-powered hydraulic fracturing units to idle. In some embodiments, for non-GTE-powered fracturing units being idled, the method may also include idling one or more of the fracturing units for a period of time and thereafter shutting down the non-GTE engines of those one or more idled fracturing units. 
     At  426 , the method may further include generating a warning signal indicative of the idling of the one or more non-GTE-powered hydraulic fracturing units being idled. For example, the power output controller may be configured to communicate such a warning signal to a communication device, for example, as described above. 
     At  428 , the example method  400  may include determining whether all the GTE-powered hydraulic fracturing units are needed to meet the total power required for successfully completing the hydraulic fracturing operation (e.g., the fracturing stage). For example, the power output controller may be configured to determine the total power output available from all the GTE-powered fracturing units not idled and determining whether that is greater than or equal to the total power required. 
     If, at  428 , it is determined that all the GTE-powered hydraulic fracturing units are needed to meet the total power required, at  430 , the example method  400  may include causing the power output of the operating GTE-powered hydraulic fracturing units to be substantially evenly distributed to meet the total power required. For example, the power output controller may be configured to communicate control signals to the GTE-powered hydraulic fracturing units to cause the appropriate power output (e.g., hydraulic horsepower output) by the respective GTE-powered hydraulic fracturing units. 
     At  432 , the example method  400  may include monitoring pressure output and/or power output of operating GTE-powered hydraulic fracturing units during the hydraulic fracturing operation and, in some examples, dynamically adjusting the power output of the GTE-powered hydraulic fracturing units autonomously or semi-autonomously as fracturing conditions change. 
     At  434 , the example method  400  may include causing unneeded GTE-powered hydraulic fracturing units to idle. For example, the power output controller may be configured to communicate control signals to the GTE-powered hydraulic fracturing units to cause the appropriate respective GTE-powered hydraulic fracturing units to idle. Also, if, at  428 , it is determined that not all the GTE-powered hydraulic fracturing units are needed to meet the total power required, the example method  400  may advance to  434 , and the example method  400  may include causing unneeded GTE-powered hydraulic fracturing units to idle. In some embodiments, the power output controller may be configured to cause one or more of the idled hydraulic fracturing units to shut down, for example, after a period of time. In some embodiments, the power output controller may be configured to cause all, or a subset, of the hydraulic fracturing units to alternate between operation and idling, for example, while continuing to perform the fracturing operation. 
     At  436  ( FIG.  4 C ), the example method  400  may include generating a warning signal indicative of idled GTE-powered hydraulic fracturing units being idled. For example, the power output controller may be configured to communicate such a warning signal to a communication device, for example, as described above. 
     At  438 , the example method  400  may include increasing the power output of one or more of the operating (un-idled) GTE-powered hydraulic fracturing units to meet the total fracturing power required. For example, the power output controller may be configured to communicate control signals to the un-idled GTE-powered hydraulic fracturing units to cause one or more of the GTE-powered hydraulic fracturing units to increase, if necessary, to collectively provide sufficient power to meet the total fracturing power required. Thereafter, the example method  400 , in some embodiments, may advance to  484  (see  FIG.  4 F ) and may include monitoring the pressure output and/or the power output of the operating hydraulic fracturing units, and, at  486 , causing the operating hydraulic fracturing units to substantially maintain pressure output and/or power output to meet the total power fracturing power required until the end of the fracturing stage, an automatic emergency shutdown occurs, or shut down by an operator occurs. 
     If, at  414  (see  FIG.  4 A ), it is determined that the total power output available is less than the total fracturing power required, at  440 , the example method  400  may include determining the amount of additional power needed to meet the total fracturing power required. For example, the power output controller may be configured to calculate the difference between the total power output available and the total fracturing power required to arrive at the additional power needed to meet the total fracturing power required. 
     At  442 , the example method  400  may include determining whether the maximum continuous power (MCP) or the maximum intermittent power (MIP) available from the GTE-powered fracturing units is sufficient to meet the total fracturing power required. In some embodiments, the MCP may range from about 95% to about 105% (e.g., about 100%) of the maximum rated power for a respective GTE-powered hydraulic fracturing unit, and the MIP may range from about 100% to about 110% (e.g., about 105% or 108%) of the maximum rated power for a respective GTE-powered hydraulic fracturing unit. In some embodiments, the power output controller may be configured to determine the MCP and/or the MIP for each of the respective GTE-powered hydraulic fracturing units, for example, based at least in part in the characteristic signals for each of the respective hydraulic fracturing units, and calculate the total MCP output and/or the total MIP output available for all the GTE-powered hydraulic fracturing units and determine whether the total available MCP and/or MIP is greater than or equal to the total fracturing power required. 
     If, at  442 , it is determined that the MCP or MIP available from the GTE-powered fracturing units is not sufficient to meet the total fracturing power required, the example method  400  may include advancing to  454  ( FIG.  4 D ), and may include determining whether more power is needed to meet the total fracturing power required. If not, the example method may further include advancing to  484  (see  FIG.  4 F ) and monitoring the pressure output and/or the power output of the operating hydraulic fracturing units. Thereafter, at  486 , the example method  400  may further include causing the operating hydraulic fracturing units to substantially maintain pressure output and/or power output to meet the total power fracturing power required until the end of the fracturing stage, an automatic emergency shutdown occurs, or shut down by an operator occurs. 
     If, at  442 , it is determined that the MCP or MIP available from the GTE-powered fracturing units is sufficient to meet the total fracturing power required, the example method  400 , at  444 , may include generating one or more MCP or MIP signals indicative that available MCP or MIP of the GTE-powered hydraulic fracturing units is sufficient to meet the total fracturing power required. For example, the power output controller may be configured to communicate an MCP or MIP signal to a communication device, for example, as described above, for advising an operator that the MCP or MIP available from the GTE-powered fracturing units is sufficient to meet the total fracturing power required. 
     At  446 , the example method  400  may include generating a query requesting whether an operator wants to operate the GTE-powered fracturing units at MCP or MIP. For example, the power output controller may be configured to communicate a prompt or query to a communication device, for example, as described above, for requesting whether an operator wants to operate the GTE-powered fracturing units at MCP or MIP to meet the total fracturing power required. 
     The example method, at  448 , may include receiving an MCP or MIP accept signal indicative that operator wants to operate GTE-powered fracturing units at MCP or MIP, for example, to meet the total fracturing power required. For example, the power output controller may be configured to receive a response to the query at  446  from an operator via a communications link. 
     At  450 , if the MCP or MIP accept signal is received, the example method  400  may include identifying the GTE-powered fracturing units operating at MCP or MIP required to meet the total fracturing power required. For example, the power output controller may be configured to determine the GTE-powered hydraulic fracturing units required to be operated at MCP or MIP to meet the total fracturing power required. In some embodiments, all the operating GTE-powered fracturing units may be operated at MCP, some of the operating GTE-powered fracturing units may be operated at MCP, all the operating GTE-powered fracturing units may be operated at MIP, some of the operating GTE-powered fracturing units may be operated at MIP, or some of the operating GTE-powered fracturing units may be operated at MCP while the other operating GTE-powered fracturing units may be operated at MIP. 
     At  452 , the example method may include causing the GTE-powered hydraulic fracturing units identified at  450  to operate at MCP and/or MIP. For example, the power output controller may be configured to communicate control signals to the identified GTE-powered hydraulic fracturing units such that they operate at MCP and/or MIP. Thereafter, the example method  400  may include advancing to  484  ( FIG.  4 F ), and the pressure output and/or the power output of the GTE-powered hydraulic fracturing units may be monitored, including those operating at MCP and/or MIP. Thereafter, at  486 , the example method  400  may further include causing the operating hydraulic fracturing units to substantially maintain pressure output and/or power output to meet the total power fracturing power required until the end of the fracturing stage, automatic emergency shutdown, or shut down by operator. 
     At  454 , the example method  400  may include determining whether more power is needed (e.g., beyond the GTE-powered hydraulic fracturing units operating at MCP and/or MIP and the non-GTE-powered operating at the rated maximum power discounted by the first non-GTE power factor (e.g., at about 80% of maximum rated power)) to meet the total fracturing power required. For example, if all the GTE-powered hydraulic fracturing units are operating at MCP or MIP and all the non-GTE-powered hydraulic fracturing units are operating at rated maximum power discounted by the first non-GTE power factor, and this is still insufficient to meet the total fracturing power required, the method  400 , at  454 , may include determining whether more power is needed to meet the total fracturing power required. 
     If, at  454 , it is determined that no additional power is need to meet the total fracturing power required, the example method  400  may advance to  484  ( FIG.  4 F ), and the pressure output and/or the power output of the GTE-powered hydraulic fracturing units operating at MCP and/or MIP may be monitored. Thereafter, at  486 , the example method  400  may further include causing the operating hydraulic fracturing units to substantially maintain pressure output and/or power output to meet the total power fracturing power required until the end of the fracturing stage, an automatic emergency shutdown occurs, or shut down by an operator occurs. 
     If, at  454 , or at  442 , it is determined that the MCP and/or MIP available from the GTE-powered fracturing units is not sufficient to meet the total fracturing power required, the example method  400  may advance to  456 , and may include generating a warning signal indicative that non-GTE-powered fracturing units are required to operate at a higher power output (e.g., higher than maximum rated output discounted by the first non-GTE power factor) to meet the total fracturing power required. Since the GTE-powered hydraulic fracturing units operating at MCP and/or MIP, combined with the non-GTE-powered hydraulic fracturing units operating at maximum rated power discounted by the first non-GTE power factor, are not able to meet the total fracturing power required, the power output controller may determine that additional power is required to meet the total fracturing power required, and thus, an option may be operating the non-GTE-powered hydraulic fracturing units a power output higher than the maximum rated power discounted by the first non-GTE power factor. Thus, the power output controller, in some embodiments, may be configured to communicate a warning signal to a communication device, for example, as described above, indicative that non-GTE-powered fracturing units are required to operate at a higher power output to meet the total fracturing power required. 
     At  458 , the example method  400  may include generating a query requesting whether an operator wants to operate non-GTE-powered fracturing units at a first higher power output, such as, for example, a power output ranging from about 80% to about 90% of the maximum rated power output. For example, the power output controller may be configured to communicate a prompt or query to a communication device, for example, as described above, for requesting whether an operator wants to operate the non-GTE-powered hydraulic fracturing units at the first higher power output to meet the total fracturing power required. 
     The example method, at  460 , may include receiving a first power increase signal indicative that the operator wants to operate non-GTE-powered hydraulic fracturing units at the first higher power output. For example, the power output controller may be configured to receive a response to the query at  456  from an operator via a communications link. If no first power increase signal is received, the example method  400  may include advancing to  484  ( FIG.  4 F ), and the pressure output and/or the power output of the GTE-powered and non-GTE-powered hydraulic fracturing units may be monitored. Thereafter, at  486 , the example method  400  may further include causing the operating hydraulic fracturing units to substantially maintain the available pressure output and/or power output until the end of the fracturing stage, an automatic emergency shutdown occurs, or shut down by an operator occurs. 
     At  462 , if at  460  the first power increase signal is received, the example method  400  may include causing the non-GTE-powered fracturing units to operate at the first higher power output. For example, the power output controller may be configured to communicate control signals to the non-GTE-powered hydraulic fracturing units to cause one or more of the non-GTE-powered hydraulic fracturing units to increase power output to the first increased power output level. 
     The example method  400 , at  464 , may include determining whether the non-GTE-powered fracturing units are operating at the first higher power output. If not, the example method  400  may return to  462  to cause the non-GTE-powered hydraulic fracturing units to operate at the first higher power output and/or or communicate a signal to the operator indicative of the failure of the non-GTE-powered hydraulic fracturing units to operate at the first higher output. 
     If, at  464 , it is determined that the non-GTE-powered fracturing units are operating at the first higher power output, at  466 , the example method  400  may include generating a first fracturing unit life reduction event signal indicative of a reduction of the service life of the non-GTE-powered fracturing units operating at the first higher output. Because operating the non-GTE-powered hydraulic fracturing units at the first higher output may increase the wear rate of the affected hydraulic fracturing units, the power output controller may generate one or more first fracturing unit life reduction event signals, which may be communicated and/or stored in the equipment profiler(s) associated with each of the affected hydraulic fracturing units. This may be taken into account in the future when determining unit health metrics and/or service intervals for one or more components of the affected units. 
     At  468  ( FIG.  4 E ), the example method  400  may include determining whether more power is needed to meet the total fracturing power required. If it is determined that no additional power is needed to meet the total fracturing power required, the example method  400  may advance to  484  ( FIG.  4 F ), and the pressure output and/or the power output of the GTE-powered hydraulic fracturing units operating at MCP and/or MIP and the non-GTE-powered hydraulic fracturing units operating at the first higher output may be monitored. Thereafter, at  486 , the example method  400  may further include causing the operating hydraulic fracturing units to substantially maintain pressure output and/or power output to meet the total power fracturing power required until the end of the fracturing stage, an automatic emergency shutdown occurs, or shut down by an operator occurs. 
     If at  468 , it is determined that additional power is needed to meet the total fracturing power required, the example method  400 , at  470 , may include generating a query requesting whether an operator wants to operate non-GTE-powered fracturing units at a second higher power output, such as, for example, ranging from about 85% to about 95% (e.g., at about 90%) of the maximum rated power output. For example, the power output controller may be configured to communicate a prompt or query to a communication device, for example, as described above, for requesting whether an operator wants to operate the non-GTE-powered hydraulic fracturing units at the second higher power output to meet the total fracturing power required. 
     The example method, at  472 , may include receiving a second power increase signal indicative that the operator wants to operate non-GTE-powered hydraulic fracturing units at the second higher power output. For example, the power output controller may be configured to receive a response to the query at  470  from an operator via a communications link. If no second power level signal is received, the example method  400  may include advancing to  484  ( FIG.  4 F ), and the pressure output and/or the power output of the GTE-powered and non-GTE-powered hydraulic fracturing units may be monitored. Thereafter, at  486 , the example method  400  may further include causing the operating hydraulic fracturing units to substantially maintain the available pressure output and/or power output until end of the fracturing stage, an automatic emergency shutdown occurs, or shut down by the operator occurs. 
     At  474 , if at  472  the second power increase signal is received, the example method  400  may include causing the non-GTE-powered fracturing units to operate at the second higher power output. For example, the power output controller may be configured to communicate control signals to the non-GTE-powered hydraulic fracturing units to cause one or more of the non-GTE-powered hydraulic fracturing units to increase power output to the second increased power output level. 
     The example method  400 , at  476 , may include determining whether the non-GTE-powered fracturing units are operating at the second higher power output. If not, the example method  400  may return to  474  to cause the non-GTE-powered hydraulic fracturing units to operate at the second higher power output and/or or communicate a signal to the operator indicative of the failure of the non-GTE-powered hydraulic fracturing units to operate at the second higher output. 
     If, at  476 , it is determined that the non-GTE-powered fracturing units are operating at the second higher power output, at  478 , the example method  400  may include generating a second fracturing unit life reduction event signal indicative of a reduction of the service life of the non-GTE-powered fracturing units operating at the second higher output. Because operating the non-GTE-powered hydraulic fracturing units at the second higher output may increase the wear rate of the affected hydraulic fracturing units, the power output controller may generate one or more second fracturing unit life reduction event signals, which may be communicated and/or stored in the equipment profiler(s) associated with each of the affected hydraulic fracturing units. This may be taken into account in the future when determining unit health metrics and/or service intervals for one or more components of the affected units. 
     At  480  ( FIG.  4 F ), the example method  400  may include determining whether more power is needed to meet the total fracturing power required. For example, the power output controller may be configured to determine whether, with the GTE-powered hydraulic fracturing units operating at MCP and/or MIP and the non-GTE-powered hydraulic fracturing units operating at the second higher output, the hydraulic fracturing units are still providing insufficient power output. 
     If so, at  482 , the example method  400  may include generating a warning signal indicative that a second higher power output provided by the non-GTE-powered hydraulic fracturing units is unable to meet the total fracturing power required, and at  484 , the example method  400  may include monitoring the pressure output and/or power output of the hydraulic fracturing units. If, at  480 , it is determined that no additional power is needed to meet the total fracturing power required, the example method  400  may advance to  484  (e.g., without generating the warning signal of  482 ), and the example method  400  may include monitoring the pressure output and/or power output of the hydraulic fracturing units. 
     At  486 , the example method  400  may include causing the hydraulic fracturing units to substantially maintain pressure output and/or power output to meet the total power fracturing power required until the end of the fracturing stage, an automatic emergency shutdown occurs, or shut down by an operator occurs. For example, the power output controller may be configured to communicate control signals to the non-GTE-powered and GTE-powered hydraulic fracturing units to cause the hydraulic fracturing units to substantially maintain pressure output and/or power output to meet the total power fracturing power required until the end of the fracturing stage, automatic emergency shutdown occurs, or shut down by operator occurs. 
     It should be appreciated that subject matter presented herein may be implemented as a computer process, a computer-controlled apparatus, a computing system, or an article of manufacture, such as a computer-readable storage medium. While the subject matter described herein is presented in the general context of program modules that execute on one or more computing devices, those skilled in the art will recognize that other implementations may be performed in combination with other types of program modules. Generally, program modules include routines, programs, components, data structures, and other types of structures that perform particular tasks or implement particular abstract data types. 
     Those skilled in the art will also appreciate that aspects of the subject matter described herein may be practiced on or in conjunction with other computer system configurations beyond those described herein, including multiprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers, handheld computers, mobile telephone devices, tablet computing devices, special-purposed hardware devices, network appliances, and the like. 
       FIG.  5    illustrates an example power output controller  62  configured for implementing certain systems and methods for controlling operation of a plurality of hydraulic fracturing units that may each include a non-GTE-engine or a GTE (e.g., a dual- or bi-fuel GTE configured to operate using two different types of fuel) according to embodiments of the disclosure, for example, as described herein. The power output controller  62  may include one or more processor(s)  500  configured to execute certain operational aspects associated with implementing certain systems and methods described herein. The processor(s)  500  may communicate with a memory  502 . The processor(s)  500  may be implemented and operated using appropriate hardware, software, firmware, or combinations thereof. Software or firmware implementations may include computer-executable or machine-executable instructions written in any suitable programming language to perform the various functions described. In some examples, instructions associated with a function block language may be stored in the memory  502  and executed by the processor(s)  500 . 
     The memory  502  may be used to store program instructions that are loadable and executable by the processor(s)  500 , as well as to store data generated during the execution of these programs. Depending on the configuration and type of the power output controller  62 , the memory  502  may be volatile (such as random access memory (RAM)) and/or non-volatile (such as read-only memory (ROM), flash memory, etc.). In some examples, the memory devices may include additional removable storage  504  and/or non-removable storage  506  including, but not limited to, magnetic storage, optical disks, and/or tape storage. The disk drives and their associated computer-readable media may provide non-volatile storage of computer-readable instructions, data structures, program modules, and other data for the devices. In some implementations, the memory  502  may include multiple different types of memory, such as static random access memory (SRAM), dynamic random access memory (DRAM), or ROM. 
     The memory  502 , the removable storage  504 , and the non-removable storage  506  are all examples of computer-readable storage media. For example, computer-readable storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. Additional types of computer storage media that may be present may include, but are not limited to, programmable random access memory (PRAM), SRAM, DRAM, RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile discs (DVD) or other optical storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium which may be used to store the desired information and which may be accessed by the devices. Combinations of any of the above should also be included within the scope of computer-readable media. 
     The power output controller  62  may also include one or more communication connection(s)  508  that may facilitate a control device (not shown) to communicate with devices or equipment capable of communicating with the power output controller  62 . The power output controller  62  may also include a computer system (not shown). Connections may also be established via various data communication channels or ports, such as USB or COM ports to receive cables connecting the power output controller  62  to various other devices on a network. In some examples, the power output controller  62  may include Ethernet drivers that enable the power output controller  62  to communicate with other devices on the network. According to various examples, communication connections  508  may be established via a wired and/or wireless connection on the network. 
     The power output controller  62  may also include one or more input devices  510 , such as a keyboard, mouse, pen, voice input device, gesture input device, and/or touch input device. The one or more input device(s)  510  may correspond to the one or more input devices  64  described herein with respect to  FIGS.  1  and  2   . It may further include one or more output devices  512 , such as a display, printer, and/or speakers. In some examples, computer-readable communication media may include computer-readable instructions, program modules, or other data transmitted within a data signal, such as a carrier wave or other transmission. As used herein, however, computer-readable storage media may not include computer-readable communication media. 
     Turning to the contents of the memory  502 , the memory  502  may include, but is not limited to, an operating system (OS)  514  and one or more application programs or services for implementing the features and embodiments disclosed herein. Such applications or services may include remote terminal units  516  for executing certain systems and methods for controlling operation of the hydraulic fracturing units  12  (e.g., semi- or full-autonomously controlling operation of the hydraulic fracturing units  12 ), for example, upon receipt of one or more control signals generated by the power output controller  62 . In some embodiments, each of the hydraulic fracturing units  12  may include a remote terminal unit  516 . The remote terminal units  516  may reside in the memory  502  or may be independent of the power output controller  62 . In some examples, the remote terminal unit  516  may be implemented by software that may be provided in configurable control block language and may be stored in non-volatile memory. When executed by the processor(s)  500 , the remote terminal unit  516  may implement the various functionalities and features associated with the power output controller  62  described herein. 
     As desired, embodiments of the disclosure may include a power output controller  62  with more or fewer components than are illustrated in  FIG.  5   . Additionally, certain components of the example power output controller  62  shown in  FIG.  5    may be combined in various embodiments of the disclosure. The power output controller  62  of  FIG.  5    is provided by way of example only. 
     References are made to block diagrams of systems, methods, apparatuses, and computer program products according to example embodiments. It will be understood that at least some of the blocks of the block diagrams, and combinations of blocks in the block diagrams, may be implemented at least partially by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, special purpose hardware-based computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functionality of at least some of the blocks of the block diagrams, or combinations of blocks in the block diagrams discussed. 
     These computer program instructions may also be stored in a non-transitory computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide task, acts, actions, or operations for implementing the functions specified in the block or blocks. 
     One or more components of the systems and one or more elements of the methods described herein may be implemented through an application program running on an operating system of a computer. They may also be practiced with other computer system configurations, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, mini-computers, mainframe computers, and the like. 
     Application programs that are components of the systems and methods described herein may include routines, programs, components, data structures, etc. that may implement certain abstract data types and perform certain tasks or actions. In a distributed computing environment, the application program (in whole or in part) may be located in local memory or in other storage. In addition, or alternatively, the application program (in whole or in part) may be located in remote memory or in storage to allow for circumstances where tasks can be performed by remote processing devices linked through a communications network. 
     This is a continuation of U.S. Non-Provisional application Ser. No. 17/942,382, filed Sep. 12, 2022, titled “SYSTEMS AND METHODS TO AUTONOMOUSLY OPERATE HYDRAULIC FRACTURING UNITS,” which is a continuation of U.S. Non-Provisional application Ser. No. 17/173,320, filed Feb. 11, 2021, titled “SYSTEMS AND METHODS TO AUTONOMOUSLY OPERATE HYDRAULIC FRACTURING UNITS,” now U.S. Pat. No. 11,473,413, issued Oct. 18, 2022, which claims priority to and the benefit of U.S. Provisional Application No. 62/705,354, filed Jun. 23, 2020, titled “SYSTEMS AND METHODS TO AUTONOMOUSLY OPERATE HYDRAULIC FRACTURING UNITS,” the disclosures of which are incorporated herein by reference in their entireties. 
     Although only a few exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the embodiments of the present disclosure. Accordingly, all such modifications are intended to be included within the scope of the embodiments of the present disclosure as defined in the following claims.