BACKGROUND
Field of the Invention
The presently disclosed instrumentalities pertain to the field of oilfield pumping equipment and, particularly, pumps used in support of well stimulation work such as hydraulic fracturing operations.
Description of the Related Art
Hydraulic fracturing is a well-known well stimulation technique in which pressurized liquid is utilized to fracture rock in a subterranean reservoir. In the usual case, this liquid is primarily water that contains sand or other proppants intended to hold open fractures which form during this process. The resulting “frac fluid” may sometimes benefit from the use of thickening agents, but these fluids are increasingly water-based. Originating in the year 1947, use of fracturing technology has grown such that approximately 2.5 million hydraulic fracturing operations had been performed worldwide by 2012. The use of hydraulic fracturing is increasing. Massive hydraulic fracturing operations in shale reservoirs now routinely consume millions of pounds of sand. Hydraulic fracturing makes it possible to drill commercially viable oil and gas wells in formations that were previously understood to be commercially unviable. Other applications for hydraulic fracturing include injection wells, geothermal wells, and water wells.
SUMMARY
The instrumentalities disclosed herein overcome the problems outlined above and advance the art by improving telemetry systems for observing pumps in support of hydraulic fracturing operations.
According to one embodiment, a hydraulic pump is used in support of a hydraulic fracturing operation. The hydraulic pump may be, for example, a triplex, quintuplex or septuplex pump of the type used for oilfield pressure pumping operations, such as well stimulation by hydraulic fracturing. The pump contains a plurality of reciprocating pistons each mounted in co-axial alignment with a corresponding one of a plurality of cylinders. Each of the cylinders are in fluidic communication with a corresponding intake opening and a corresponding discharge opening. A prime mover, such as an electric motor, an internal combustion engine such as a diesel motor or a reciprocating gas engine, or a hydraulic motor, together with speed reduction components such as a transmission or pump power end, imparts motive force to a drive linkage that couples each of the plurality of reciprocating pistons with the prime mover. The drive linkage is operable for imparting rotational motion to each of the reciprocating pistons that at different times produces: (1) a first axial shifting motion such that each of the plurality of reciprocating pistons within each corresponding one of the cylinders moves in a first direction to perform an intake stroke capable of drawing fluid through the intake opening and into the corresponding one of the cylinders, and thereafter produces; (2) a second axial shifting motion such that each of the plurality of reciprocating pistons within each of the cylinders moves in a second direction opposite the first direction to perform a discharge stroke capable of expelling the fluid from the cylinder through the corresponding one of the discharge openings.
In one aspect, each of the cylinders contains a suction valve mounted proximate the corresponding intake opening for the cylinder, together with structure mounting the suction valve for movement between a closed intake position and an open intake position. The closed intake position is normally operable for sealing of the intake opening during the discharge stroke. The open intake position is normally operable for permitting passage of the fluid into the cylinder during the intake stroke. The intake valve and the structure mounting the intake valve are subject to wear such that the intake valve ceases to be normally operable for sealing of the intake opening during the discharge stroke, such occurrences can result in irreparable damage to the entire fluid end.
In one aspect, each of the cylinders contains a discharge valve mounted proximate the corresponding discharge opening for the cylinder, together with structure mounting the suction valve for movement between a closed discharge position and an open discharge position. A discharge valve is mounted proximate the corresponding discharge opening for the cylinder. The closed discharge position is normally operable for sealing of the intake opening during the intake stroke, and the open discharge position is normally operable for expelling the fluid from the cylinder during the discharge stroke. The discharge valve and the structure mounting the discharge valve are subject to wear such that the discharge valve ceases to be normally operable for sealing of the discharge opening during the discharge stroke, such occurrences can result in irreparable damage to the entire fluid end.
In one aspect, a rotational member of the drivetrain varies in rotational position over time concomitant with the first axial shifting motion and the second axial shifting motion of the reciprocating piston. The rotating member may be a drive shaft, a drive gear, a crankshaft or other linkage for driving the reciprocating piston of the pump. A rotational encoder may be provided for assessing a rotational speed of the rotating member. These structures may include, for example, an optical or electromagnetic pickup system. The rotational encoder is employed to detect variations in the rotating speed of the input shaft to the power end, which corresponds to a specific frequency under observation. The Fourier transform may be utilized as a method to analyze the frequency variations in the data obtained from the rotational encoder. This analysis helps isolate the frequency indicative of the washout condition, allowing the controller, programmed accordingly, to associate the identified washout condition with a specific cylinder within the system.
In operation, a plurality of the aforementioned hydraulic pumps may be hydraulically coupled to operate in tandem while pumping frac fluid into a well for purposes of hydraulically stimulating the well.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a hydraulic pumping system according to the presently described instrumentalities;
FIG. 1A shows an expanded detail section of the hydraulic pumping system shown in FIG. 1;
FIG. 2 is a midsection view taken along line 2-2′ of FIG. 1;
FIG. 3 provides additional detail with respect to a valve feature of FIG. 2;
FIG. 4 is a chart showing pump displacement rates over time with respect to each of five cylinders in a hydraulic pump as the hydraulic pump develops a washout condition;
FIG. 5 shows a series of detection peaks indicating transient rotational velocities as obtained from optical targets on a rotating member of a drivetrain for the hydraulic pump;
FIG. 6 shows a washout diagnosis indicated by periodic repeating rotational velocity anomalies obtained from analyzing the data shown in FIG. 5; and
FIG. 7 is a flowchart of program logic using pump rotational velocity values to diagnose a washout condition.
DETAILED DESCRIPTION
Description of the Preferred Embodiments
There will now be shown and described, by way of non-limiting examples, various instrumentalities for overcoming the problems discussed above.
FIG. 1 shows a hydraulic pump 100 including a power end 102 and a fluid end 104. In preferred embodiments, the hydraulic pump 100 is capable of oilfield pressure pumping operations and, in particular, well stimulation operations in the nature of hydraulic fracturing. By way of example, suitable hydraulic pumps 100 may be purchased on commercial order from such companies as GD Energy Products of Aledo, Texas or Caterpillar, Inc. of Irving, Texas.
As shown in FIG. 1, however, the fluid end 104 has been modified to include a rotation sensor unit 106 according to the presently described instrumentalities. FIG. 1A presents the rotation sensor unit 106 in expanded detail. The rotation sensor unit 106 is equipped with a sensor 108 that senses a rotational passage 110 of a rotary member 112 in the drivetrain for the power end 104. The rotary member 112 may be, for example, a driveshaft, crankshaft or gear. As shown in FIGS. 1 and 1A, the rotary member 112 is a driveshaft. A plurality of sensor targets 114 are mounted on the rotary member 112 in proximity to the sensor 108, preferably at the outer diameter of the rotary member 112. The nature of the targets 114 matches the type of sensor 108 such that the rotary member 112 and the targets 114 may be paired to form, for example, a magnetic or electromagnetic field sensor system, a radiation sensor system, or an optical sensor system. When the rotary member 112 is rotating in the intended environment of use, the sensor 108 detects individual ones of the targets 114 to produce a time-dependent signal 116 that embodies instantaneous values representing the rotational passage 110. The time dependent signal 116 may embody a rotational velocity, acceleration, momentum, or kinetic energy value associated with the rotational passage 110. The number of targets 114 may vary. There should be at least one target 114 for each cylinder and, preferably more than 100 of the targets 114 in total. Most preferably there are at least about 250 of the targets 114, which are optical targets sensed by detecting backscattering or other reflection of light incident to the individual targets from a light emitting diode which may be fitted with a gradient reduction index (GRIN) lens or from laser light.
By way of example, the most common internal gearing configuration in use for power ends such as power end 102 is currently a 6.353:1 reduction. Thus, a crankshaft (not shown) internal to the power end 102 turns once for each of about 6.353 revolutions of the rotary member 112 with torque being output to driveshaft 117. In some embodiments, an internal crankshaft (not shown) may be fitted with an indexer, such as a magnetic pickoff (not shown) that identifies top dead center at the maximum extent of a discharge stroke for a piston internal to the hydraulic pump 100. An indexer of this nature may be used to identify a particular cylinder that has a washout according to the frequency based analysis described below.
As shown in FIG. 1, the time-dependent signal 116 is a wireless signal that may, for example, be transmitted to a remote data van 118 equipped with wireless communications 120 to a processing center that may be on the same location. The data van 118 may have an internal computer 121 complete with a central processing unit, random access memory and data storage. The computer 121 may be programmed with instructions for accomplishing a washout diagnosis as described below in more detail. The data van 118 may be, for example, parked on a wellsite location where the hydraulic pump 100 resides to control various operational parameters of the hydraulic pump 100 and a fleet of such pumps. Alternatively, the time-dependent signal 116 does not need to be transmitted wirelessly and may be transmitted to the data van 118 by wire (not shown) or to an operator station 122 that is co-mounted with the hydraulic pump 100 on a trailer bed 123. The signal 116 may be processed as described in additional detail below to identify one or more washout conditions within the fluid end 104.
As shown in FIG. 1, a prime mover 124 may be an electric motor or, alternatively, a system of electric motors constructed and arranged to drive a planetary gearing system as described in U.S. Pat. No. 11,313,359 which is hereby incorporated by reference to the same extent as though fully replicated herein. The prime mover 124 may alternatively be a natural gas engine or a diesel engine or a hydraulic motor, and other elements of a drivetrain may be included, such as a transmission to provide additional gear reduction depending upon the nature of the prime mover 124 as is known in the art.
Broadly speaking, the rotary member 112 may be any rotatable linkage in a drivetrain that couples the prime mover 124 with the power end 102 to provide sufficient torque for pressure pumping operations. The drivetrain may vary depending upon the nature of the prime mover 124. Suitable drivetrains with various forms of the rotary member 112 are described, for example, in U.S. Pat. Nos. 11,339,769 to Buckley and U.S. Pat. No. 10,895,138 to Coli et al., both of which are hereby incorporated by reference to the same extent as though fully replicated herein It will be appreciated that the rotary member 112 may be any linkage known to the art for example an electro-hydraulic drive train as described in United States Patent Application Publication No. 2022/0251936 to Wilson, or a transmission with a range of gears suitable for use with a diesel engine as described in United States Patent Application Publication No. 2014/0196570 to Small et al, both of which are hereby incorporated by reference to the same extent as though fully replicated herein.
According to the presently disclosed instrumentalities, well stimulation operations are improved by use of the rotation sensor unit 106 and processing of the time-dependent signals 116 derived therefrom to detect and characterize washout conditions.
As shown in FIG. 1, the hydraulic pump 100 is a quintuplex pump. This name indicates a total of five reciprocating cylinders such as cylinders 128, 130, 132 fitted with crush caps 134, 136, 138 which normally seal the cylinders but may be opened for service of parts internal to the fluid end 104. The hydraulic pump 100 may, alternatively, have any number of reciprocating pistons such as a triplex, quintuplex, or septuplex pump. Each of the cylinders 128, 130, 132 are fed by an intake line 133 that is fluidically coupled with a conventional blending unit (not shown) that supplies frac fluid to the hydraulic pump 100 for pressure pumping operations as are known to the art. The cylinders 128-132 receive frac fluid from the intake line 133 and discharge the frac fluid into a shared plenum (not shown) within the fluid end 104 from which the frac fluid exits through discharge line 142 at increased pumping pressure.
FIG. 2 is a midsection view taken along line 2-2′ of FIG. 1. A reciprocating piston 200 is mounted on a piston rod 202 coaxially 203 with cylinder 128. Crankshaft 204 drives the piston rod 202 in a reciprocating motion including an intake stroke 206 that moves the piston 200 to draw frac fluid 207 from the intake line 133 into cylinder 128 and a discharge stroke 208 that expels the frac fluid 207 into a discharge plenum 210 in fluidic communication with the discharge line 142 (see FIG. 1). The cylinder 128 has an intake opening 212 fitted with an intake seat 214 and a reciprocating intake valve 216 that moves in direction 218 to facilitate entry of frac fluid from the intake line 133 into the cylinder 128 concomitant with the intake stroke 206. Structure mounting the valve over the intake opening 212 includes a guided spring assembly 220 providing bias that pushes the intake valve 216 into a position of sealing engagement with the intake valve seat 214. The intake line 133 is sometimes referred to as a pump ‘suction’ line, but in practice the frac fluid coming from a blender is usually pressurized to approximately 30 to 80 psi. The bias asserted by the guided spring assembly 220 is sufficient to overcome the pressure of frac fluid within the intake line 133, but motion of the piston 200 during the intake stroke 208 creates a relative vacuum that overcomes this bias to pull the intake valve 216 away from a position of sealing engagement with the intake valve seat 214.
A discharge opening 222 is conversely constructed such that a guided spring assembly 224 biases a discharge valve 226 into a position of sealing engagement with a discharge valve seat 228 concomitant with movement 230 as the intake stroke 206 begins. The discharge stroke 208 pressurizes the frac fluid within cylinder 128 to unseat the discharge valve 226 from the discharge valve seat 228 with motion 232 permitting the frac fluid to flow into the discharge plenum 210 for eventual exit through the discharge line 142 (see FIG. 1). Various openings are sealed by externally threaded crush-cap assemblies including plugs 234, 236, and nuts 238, 240 which may be removed for maintenance purposes including the repair or replacement of valves 216, 226 as well as the piston 200. The crankshaft 204 may be fitted with a magnetic pickoff 241 that is indexed to a top dead center position for one of the cylinders at the fullest extent of stroke 208.
FIG. 3 provides additional detail with respect to the operation and failure modes of the discharge valve 226. At a position of sealing engagement as shown in FIG. 3, the discharge valve 226 and the discharge seat 228 form a circumferential compression seal at interface 300. One failure mode occurs when the guided spring assembly 224 breaks such that it no longer biases the discharge valve 226 towards the discharge valve seat 228 and the discharge valve 226 is misoriented to such an extent that the seal at interface 300 can no longer be formed. More commonly, however, the frac fluid contains abrasive proppant, such as sand, which removes materials forming the seal at interface 300 to form a washout 302. The absence of material forming the washout 302 can be due to removal of material from the discharge valve 226, the discharge seat 228, or both the discharge valve 226 and the discharge seat 228. In this condition, the washout 302 causes reduced pressure in the discharge plenum 210 during the discharge stroke 208 (see FIG. 2) due to backflow of the frac fluid from the discharge plenum 210. It will be understood that, while washouts occur more frequently in association with the discharge valve 226, the same type of washout failure condition may occur in association with the intake valve 216 which results in loss of pumping pressure within the cylinder 128 (see FIG. 2) due to backflow of frac fluid from the cylinder 128 into the intake line 133.
Once the washout 302 begins to form in the intended environment of use, the condition rapidly worsens due to abrasion from the proppant constituent of the frac fluid. The progression of resulting wear eventually necessitates servicing of the hydraulic pump 100 to replace the discharge valve 226 and the discharge valve seat 228, or the intake valve 216 and the intake valve seat 214 as the case may be. This is problematic when the hydraulic pump 100 is engaged in hydraulic fracturing operations that may be delayed for pump maintenance or adversely affected by poor pump performance of the hydraulic pump or render the fluid end unusable. Most often, a fleet of pumping units are deployed to pump in tandem for hydraulic fracturing operations and excess hydraulic horsepower is available to offset the loss of one or more hydraulic pumps as they undergo maintenance; however, this type of stepping up of the additional pumps is undesirable because it accelerates wear in the working pumps and adds overhead costs related to sourcing additional pumps, extra diesel, drivers, etc. Due to the abrasive nature of frac fluids, the extent of wear resulting from washout conditions tends to accelerate once the washout starts to form. Operators are constantly faced with decisions over whether to do maintenance on an underperforming pump, as well as the extent of maintenance to be performed.
FIG. 4 shows a set of pump displacement rates for each of the five cylinders in the hydraulic pump 100. As is known in the art, the pump displacement rate may be calculated using a volumetric rate determined as the diameter of the cylinder or piston times the linear velocity of the piston. This calculation provides an ideal displacement assuming 100% pumping efficiency, but in practice the pumping efficiency is less than 100% due to leakage including leakage that may be caused by a washout condition as described above. The pump displacement rates over time appear as overlapping sine waves where the displacement rates for each cylinder of the pump 100 are presented on the Y-axis and have been indexed to a dimensionless value ranging from 1 to −1. A Fourier transform may be utilized to identify or isolate frequencies outside of an expected periodic value. Commercially available software packages are available for this purpose, such as Mathematica from Wolfram Research, Inc. of Champaign, Illinois or MatDeck™ from LabDeck-Flexitek Ltd of Greenford, United Kingdom.
On FIG. 4 the pump displacement rates for each cylinder are labeled with “Cyl 1, Cyl 2, etc. . . . (See cylinders 128, 130, 132 of FIG. 1). The dimensionless values from 0 to 1 on the Y-axis are determined by dividing the actual discharge rate by the maximum discharge rate, which is associated with the midpoint of the discharge stroke 208 (see FIG. 2). The values from 0 to −1 are determined by dividing the actual intake rate by the maximum intake rate, which is associated with the midpoint of the intake stroke 206. The time domain on the X axis has been indexed to a dimensionless value ranging from 0 to 1 by dividing the elapsed time by the time required for a full completion of the intake stroke 206 and the discharge stroke 208. It will be appreciated that the indexed displacement rates for each cylinder are sinusoidal and that each stroke produces cylinder-specific maxima at points 400, 402, 404, 406, and 408 and cylinder-specific minima at points 400′, 402′, 404′, 406′ and 408′ that are observable by the sensor 108. The maxima 400-408 are associated with peak pressure at the highest linear velocity of the piston during the discharge stroke 208. The minima 400′-408′ are associated with maximum suction at the highest linear velocity of the piston during the intake stroke 206.
The maximum pump displacement rates 400-408 are separated by time intervals A, B, C, D and E. The minimal pump displacement rates 400′-408′ are separated by intervals A′, B′, C′, D′ and E′. It will be appreciated, for example, that point 400 is at the maximal value for cylinder 2 (Cyl 2). Ideally, the intervals A-E are equal in magnitude. This does not happen in practice because each of the cylinders 1-5 have different pumping efficiencies, so the intervals A-E are slightly different in magnitude. A higher pumping efficiency is associated with higher pressure and more resistance which, for example, decelerates the speed of the reciprocating piston 200 in cylinder 128 and, consequently, increases the observed one of time intervals A-E. A lower pumping efficiency is associated with less resistance, which accelerates the speed of the reciprocating piston 200 in cylinder 128—decreasing the observed time interval. Thus, it will be appreciated that washout conditions, such as washout 302 shown in FIG. 3, are observable by a relative shortening of a particular one of intervals A-E or A′-E′ as the pump 100 is performing one of the intake stroke 206 and the discharge stroke 208. A washout condition in cylinder 5 (Cyl 5), for example, may be observable as a shortening of intervals B, C or D′, but it will be appreciated that it is the discharge stroke that dominates the pumping time analysis because it is the discharge stroke that imparts pressure to the frac fluid, and the discharge stroke of the cylinders 1-5 is represented by values 0 to 1 on the Y-axis of FIG. 4.
It is possible to use a time or dimensionless time analysis characterizing the intervals A-E for purposes of washout analysis as described below. By way of example, if there are 248 targets, these may be synchronized with the magnetic pickoff 241 as described above, for example, to identify top dead center of cylinder 1 (Cyl 1) at point 414 coinciding with maximum displacement rate 400. Because point 400 is 90° from point 414 on the sinusoidal function of cylinder 2 (Cyl 2) comprising 25% of a full rotation, point 400 is separated by 62 targets from point 414 (248 targets*90°/360°). In this manner, point 400 is associated by a difference of 62 targets from the timing target at point 414. Because there are five cylinders, the respective sine waves are offset from one another by one-fifth of a rotation or 72° amounting to 49.6 targets (248 targets/360°*72°). Thus, each of points 400, 402, 404, 406, 408 are separated from one another by 49.6 targets. Furthermore, each of the points 400-408 are ideally located exactly 62 targets behind the top dead center positions of their respective pistons indicated as points 414, 416, 418, 420.
It will be appreciated that the interval E′, in addition to spanning the minimal displacements of cylinders 2 and 3 also spans the maximum displacement of cylinder 5 to include peak 404, which in the case of a washout may be shifted to position 404′. The maximum displacement of cylinder 5 also controls the pressure pumping profile, which expands much the same amount of horsepower even if cylinder 5 is moving less fluid due to the washout. This causes the interval E′ to shorten due to the expenditure of the same horsepower to move less fluid.
By these instrumentalities, a washout condition in cylinder 5 (shown as “Cyl 5” in FIG. 4) is dynamically observable over time in at least three ways. First, a washout in cylinder 5 may be detected as a shifting of peak displacement rate 404 for cylinder 5. This detection opportunity arises because when the hydraulic pump 100 is pumping at a fixed rate it exerts an approximately constant amount of torque. When cylinder 5 develops a washout condition, the hydraulic resistance from pumping on the discharge stroke is reduced, especially at the peak pressure associated with point 404. The washout is, therefore, evident as a relative shifting of the peak displacement rate 404, which is associated with the discharge stroke of cylinder 5, to a different position shown in FIG. 4 as position 404″. This shifting between peak displacement rate 404-404″ happens because the time interval between points 410 and 412 is shortened due to the reduced pressure attributable to the washout condition in cylinder 5. Thus, if the driveshaft 117 of hydraulic pump 100 is indexed to a timing mark denoting position 414, it is possible to associate the washout with cylinder 5 indicated by peak 404″ by counting forward along the 0-value axis in increments of 72° to associate the curve for cylinder 5 with the washout. In practice, however, all cylinders of the fluid end 104 will be serviced in the event where even one washout condition is detected so as a practical matter it is not strictly necessary to use indexing for identification of the cylinder with a washout. Even so, it is useful from a maintenance standpoint to pay closer attention to a particular cylinder that the foregoing analysis has identified as having a washout condition.
Because there are five cylinders, the points 410 and 412 are separated by 36 degrees of rotation and exist at the intersections between the pump displacement rate curve for cylinder 5 and the adjacent curves for cylinders 1 (point 410) and cylinder 4 (point 412). It follows that another method of detecting the washout in cylinder 5 is to observe the shortening of interval 410-412 itself, as opposed to the shifting of peak 404 to position 404″. Yet another method of detecting the washout in cylinder 5 is to observe the shortening of intervals B, C and E, as opposed to the shifting of peak 404 to position 404″. Any combination of these methods may be used, such that one technique confirms another.
Thus, it is possible to diagnose washout conditions by the use of numerical methods to assess variances from ideal rotational rates in the rotational velocity 110 (see FIG. 1A) among the five cylinders of the hydraulic pump 100.
FIG. 4, while useful in understanding the mechanics of pump timing variations indicative of a washout condition, does not show more precisely the nature of the time-dependent signal 116 emanating from the rotation sensor unit 106. As shown in FIG. 5, the time-dependent signal 116 has the interval B (see also FIG. 4) where the interval B has been shortened by the shifting of peak 404 to position 404″ due to a washout condition. The X-axis of FIG. 5 is a dimensionless time value calculated as the time to fully complete the intake strokes 206, 208 (See FIG. 2) corresponding to a full period of the sine curves for any one of cylinders 1-5 as presented on FIG. 4. The Y-axis is scaled to present a value ranging from 0 to 1 where 1 is the maximum amplitude of a sensed signal from the rotation sensor unit 106. The individual peaks such as peaks 500, 502, 504, 506, 508, 510, 512 demonstrate a sensed passage of a corresponding one of the targets 114 when performing rotational passage 110. Ideally, the peaks 500-512 are spaced equally apart. This is shown by way of example as distance 514 separating peaks 502 and 504 or as distance 516 separating peaks 506 and 508.
As a washout condition develops, however, the peaks are no longer spaced equidistantly apart. This is shown in FIG. 5 where a washout condition is affecting the reciprocating piston velocity in one cylinder, which may be a shortening of interval B due to a washout in Cyl 5 as shown in FIG. 4. Thus, all other adjacent peaks outside of interval B can be ignored because they are evenly spaced by equal amounts 514, 516. Within interval B, however, there is less fluid resistance when pumping so the adjacent peaks are separated by shortened intervals, such as interval 517, having a magnitude less than that of intervals 514, 516. Because the shortened peaks within interval B, such as peaks 510, 512, are immediately adjacent one another, they are presumed to be associated with a single washout condition. These peaks may be optionally averaged to present a rotational velocity anomaly 518 centered at time 520. The remainder of peaks in the time-dependent signal 116 may be ignored because they fall within a range of normalcy. Normalcy may be established by a comparative thresholding calculation that compares by subtracting the separations 514, 516 against a standard value and selects only peaks associated with differences that exceed a delimiting amount. The standard value may be, for example, calculated according to Equation (1) below:
SV=R/G/T, where (1)
- SV is the standard value, R is a rotational velocity of the rotary member 112, G is the gear reduction ratio between the rotary member 112 and the crankshaft of the power end 102, and T is the number of targets 114.
The value R may be measured from the prime mover 124 or, more preferably, by calculating for a full rotation of the crankshaft a standard deviation of the peak separation values such as separation values 514, 516, 517, excluding values outside the standard deviation, and averaging the values that remain.
The delimiting amount may be an absolute value or a percentage value of either time or dimensionless time that field experience indicates is associated with a washout condition. This could be, for example, 3%, 5%, 7%, 9%, or 11% of SV depending upon conditions encountered in the field.
It is also possible to use a moving average of time intervals spanning a length of E′ or less to compare minima in a manner that diagnoses a washout condition as a periodically repeating minimal value exceeding a threshold amount below the average of all periodic minima.
FIG. 6 shows the rotational velocity anomaly 518 as a first observed instance at τ1 as indicated on the X-axis where in the case of a single washout time values τ2, τ3, τ4, are ideally spaced apart by equal increments according to the periodicity of peak displacement 402 as shown in FIG. 4. The time values τ1 to τ4 correspond to the periodicity of anomaly 518 at the central time 520. If this periodicity is not detected then the anomaly 520 is transient and is not associated with a washout as there are other factors that may cause transient anomalies, such as an improperly seated valve or debris in the flow stream within the fluid end 104 (see FIG. 1). It will be appreciated that strokes 206, 208 have been fully completed when the count of all such peaks matches the number of targets 114, and this corresponds to a full rotation of the driveshaft 117. The rotational velocity anomaly 518 repeats itself at rotations 200, 300 and 400, which demonstrates a periodicity confirming a washout condition. A different anomaly 600 constitutes noise in the data set that does not repeat and has no periodicity. The anomaly 600 is, consequently, rejected as not being associated with a washout condition. Noise such as this may be caused by transient operating conditions, which may be, for example, acceleration of the prime mover 124 or a bubble of air in one of the cylinders 128, 130, 132.
It will be appreciated that the foregoing method of analysis according to FIGS. 5 and 6 is capable of detecting a washout in any cylinder but, because there is no requirement for indexing to a position of the crankshaft, the analysis does not identify the particular cylinder where the washout exists. Practically speaking, there is not necessarily a need to use an indexer because once the pump is brought in for service all of the pistons and valves in the pump will be serviced or replaced regardless of the cylinder where the washout resides.
FIG. 7 is a flowchart depicting program logic 700 that may be utilized to provide the washout detection as discussed above. The program logic may reside, for example, in the computer 121 (see FIG. 1), the operator station 122, or at a local data center accessed by wireless communications 120 through the data van 118. Once a washout condition is detected, an alarm may be transmitted over the internet to a central place of monitoring. The data van 118 is preferably configured to simultaneously monitor a fleet of pumping units that may contain, for example, from 15 to 25 pumping units pumping in tandem on a single wellsite location. The program logic 700 operates on the edge via a microcontroller that calculates and monitors 702 rotational velocity data embodied in the time dependent signal 116 while a hydraulic fracturing operation is underway. The program logic performs an analysis to detect a velocity anomaly using numerical methods as described above or frequency analysis, and loops back to continue monitoring 702 if no velocity anomaly is detected 704.
If a velocity anomaly is detected 704 the program logic further performs a study to ascertain if the anomaly is periodic 706. This may be an analysis that determines, for example, whether the anomaly is present in at least a threshold delimiting number of crankshaft rotations, such as 40, 80 or 120 or more consecutive rotations of the crankshaft 204. If not, the program logic 700 loops back to step 702.
If periodicity is found to exist 706, the program logic 700 produces an alert 708 signaling a need to schedule maintenance 710. Ideally, the hydraulic pump will not be immediately withdrawn from service and may continue pumping until the pumping unit may be replaced or the current hydraulic fracturing operation is completed. At the appropriate time pursuant to schedule 712 the hydraulic pump 100 is transported to a service facility where maintenance is performed 714.
Those of ordinary skill in the art will understand that the foregoing discussion teaches by way of example and not by limitation. Accordingly, what is shown and described may be subjected to insubstantial change without departing from the scope and spirit of invention. The inventors hereby state their intention to rely upon the Doctrine of Equivalents, if needed, in protecting their full rights in the invention.
Patent Application
20250129696
