Method for monitoring an oil well pumping unit

Claim 1

A method of monitoring for correction the operation of an oil well pumping unit that includes a prime mover having a rotating rotor and a power transmission unit and which reciprocates a rod string including a polished rod, said string being connected to a subsurface well pump, which comprises: (a) determining prime mover rotor instantaneous speeds of revolution for revolutions turned during the period of a complete or predetermined portion of a reciprocation cycle of the said pumping unit, (b) applying all or selected instantaneous speeds of revolution from step (a) to determine the value of at least one parameter of pumping unit performance for the said period, said parameter being selected from the group consisting of prime mover power output, prime mover modified average current, prime mover power input, prime mover thermal current, prime mover power factor, power transmission unit maximum torque, and total polished rod work, and (c) comparing the parameter value determined in step (b) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship predetermined indicative of: (i) if the selected parameter is one of prime mover power output, prime mover modified average current or total polished rod work: well pump off or a rod string part; (ii) if the selected parameter is prime mover power input: an excessive prime mover power input; (iii) if the selected parameter is prime mover thermal current, to detect: an excessive current load for the prime mover; (iv) if the selected parameter is prime mover power factor: a power factor below an established level; (v) if the selected parameter is power transmission unit maximum torque: an imbalance in the pumping unit.

Claim 2

A method of monitoring for correction the operation of an oil well pumping unit that includes a prime mover having a rotating rotor and a power transmission unit and which reciprocates a rod string including a polished rod, said string being connected to a subsurface well pump, which comprises: (a) determining prime mover rotor instantaneous speeds of revolution for revolutions turned during the period of a complete or predetermined portion of a reciprocation cycle of the said pumping unit, (b) applying all or selected instantaneous speeds of revolution from step (a) to determine the value of at least one parameter of pumping unit performance for the said period, said parameter being selected from the group consisting of prime mover power output, prime mover modified average current, prime mover power input, prime mover thermal current, prime mover power factor, power transmission unit maximum torque, and total polished rod work, and (c) comparing the parameter value determined in step (b) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship predetermined indicative of: (i) if the selected parameter is one of prime mover power output, prime mover modified average current or total polished rod work: well pump off or a rod string part; (ii) if the selected parameter is prime mover power input: an excessive prime mover power input; (iii) if the selected parameter is prime mover thermal current, to detect: an excessive current load for the prime mover; (iv) if the selected parameter is prime mover power factor: a power factor below an established level; (v) if the selected parameter is power transmission unit maximum torque: an imbalance in the pumping unit.

Claim 4

A method of monitoring for correction the operation of an oil well pumping unit that includes a prime mover having a rotating rotor and a power transmission unit and which reciprocates a rod string including a polished rod, such string being connected to the plunger of a subsurface well pump, which comprises: (a) determining the value of at least one parameter of pumping unit performance for the period of a complete or predetermined portion of a reciprocation cycle of the pumping unit, said parameter for such period being a function of instantaneous speeds of revolution of the prime mover rotor during said period, and being selected from the group consisting of prime mover power output, prime mover modified average current, and total polished rod work, (b) comparing the parameter value determined in step (a) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship predetermined indicative of cause for stopping operation of said pumping unit, and (c) stopping operation of the said pumping unit when said relationship is detected.

Claim 5

A method of monitoring for correction the operation of an oil well pumping unit that includes a prime mover having a rotating rotor and a power transmission unit and which reciprocates a rod string including a polished rod, such string being connected to the plunger of a subsurface well pump, which comprises: (a) determining the value of at least one parameter of pumping unit performance for the period of a complete or predetermined portion of a reciprocation cycle of the pumping unit, said parameter for such period being a function of instantaneous speeds of revolution of the prime mover rotor during said period, and being selected from the group consisting of prime mover power output, prime mover modified average current, and total polished rod work, (b) comparing the parameter value determined in step (a) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship predetermined indicative of cause for stopping operation of said pumping unit, and (c) stopping operation of the said pumping unit when said relationship is detected.

Claim 6

A method of monitoring for correction the operation of an oil well pumping unit comprising a drive train including a prime mover having a rotor and a power transmission unit having a speed reducer, an energizing circuit for said prime mover, and a reciprocating rod string connected to the plunger of a subsurface well pump, which comprises (a) determining prime mover rotor instantaneous speeds of revolution for revolutions turned during a complete or predetermined portion of a reciprocation cycle of the said pumping unit, (b) applying all or selected instantaneous speeds of revolution from step (a) to obtain the value of at least one parameter or prime mover performance for the period of said cycle or said predetermined portion thereof, as the case may be, said parameter being selected from the parameters consisting of prime mover power output, modified average current, power input, thermal current, and power factor, said parameters being related to said applied instantaneous speeds of revolution according to the following equations, wherein the subscript "i" designates a prime mover rotor revolution occurring during said period with respect to which an instantaneous speed of revolution is applied (an "ith revolution"): ______________________________________ ##STR13## wherein PO = value of prime mover power output for the said period, n = the number of all ith revolutions occurring in the said period, P.sub.i = αT.sub.i (RPM.sub.i) wherein P.sub.i = the instantaneous power output value of the prime mover on an ith revolution of the prime mover rotor, α = predetermined conversion factor constant to obtain proper power units, RPM.sub.i = the value of the instantaneous speed of prime mover rotor revolution on an ith revolution, T.sub.i = the predetermined value of prime mover rotor instantaneous torque that corresponds to RPM.sub.i on an ith revolution of the prime mover rotor, ##STR14## where MAC = value of prime mover modified average current for the said period, n = the number of all ith revolutions occurring in the said period, C.sub.i = the predetermined value of prime mover instantaneous current that corresponds to RPM.sub.i (as RPM.sub.i is defined for the equation (1) hereof) and an ith revolution of the prime mover rotor, A.sub.i = 1 where RPM.sub.i on an ith revolution is less than or equal to synchronous speed of the prime mover rotor, A.sub.i = -1 where RPM.sub.i on an ith revolutions is greater than synchronous speed of the prime mover rotor; ##STR15## where PI = value of prime mover power input for the said period, n = the number of all ith revolutions occurring in the said period, P.sub.i = αT.sub.i (RPM.sub.i), where P.sub.i, α, T.sub.i and RPM.sub.i are the values defined for equation (1) hereof, and E.sub.i = the predetermined value of prime mover instantaneous efficiency that corresponds to RPM.sub.i on an ith revolution of the prime mover rotor, ##STR16## where value of prime mover thermal current for the said period, the number of all ith revolutions occurring in the said period, C.sub.i the value defined for equation (2) hereof, ##STR17## where PF is the value of prime mover power factor for the said period, v is a predetermined constant to obtain proper power factor unit, n is the number of all ith revolutions occurring in the said period, P.sub.i is as defined for equation (1), C.sub.i is as defined for equation (2), E.sub.i is as defined for equation (3) and V is value of voltage of the said energizing circuit; and ______________________________________ (c) comparing a parameter value obtained in step (b) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship predetermined indicative of: (i) if the selected parameter is one of prime mover power output, or prime mover modified average current well pump off or a rod string part; (ii) if the selected parameter is prime mover power input: an excessive prime mover power input; (iii) if the selected parameter is prime mover thermal current, to detect: an excessive current load for the prime mover; (iv) if the selected parameter is prime mover power factor: a power factor below an established level.

Claim 7

A method of monitoring for correction the operation of an oil well pumping unit comprising a drive train including a prime mover having a rotor and a power transmission unit having a speed reducer, an energizing circuit for said prime mover, and a reciprocating rod string connected to the plunger of a subsurface well pump, which comprises (a) determining prime mover rotor instantaneous speeds of revolution for revolutions turned during a complete or predetermined portion of a reciprocation cycle of the said pumping unit, (b) applying all or selected instantaneous speeds of revolution from step (a) to obtain the value of at least one parameter or prime mover performance for the period of said cycle or said predetermined portion thereof, as the case may be, said parameter being selected from the parameters consisting of prime mover power output, modified average current, power input, thermal current, and power factor, said parameters being related to said applied instantaneous speeds of revolution according to the following equations, wherein the subscript "i" designates a prime mover rotor revolution occurring during said period with respect to which an instantaneous speed of revolution is applied (an "ith revolution"): ______________________________________ ##STR13## wherein PO = value of prime mover power output for the said period, n = the number of all ith revolutions occurring in the said period, P.sub.i = αT.sub.i (RPM.sub.i) wherein P.sub.i = the instantaneous power output value of the prime mover on an ith revolution of the prime mover rotor, α = predetermined conversion factor constant to obtain proper power units, RPM.sub.i = the value of the instantaneous speed of prime mover rotor revolution on an ith revolution, T.sub.i = the predetermined value of prime mover rotor instantaneous torque that corresponds to RPM.sub.i on an ith revolution of the prime mover rotor, ##STR14## where MAC = value of prime mover modified average current for the said period, n = the number of all ith revolutions occurring in the said period, C.sub.i = the predetermined value of prime mover instantaneous current that corresponds to RPM.sub.i (as RPM.sub.i is defined for the equation (1) hereof) and an ith revolution of the prime mover rotor, A.sub.i = 1 where RPM.sub.i on an ith revolution is less than or equal to synchronous speed of the prime mover rotor, A.sub.i = -1 where RPM.sub.i on an ith revolutions is greater than synchronous speed of the prime mover rotor; ##STR15## where PI = value of prime mover power input for the said period, n = the number of all ith revolutions occurring in the said period, P.sub.i = αT.sub.i (RPM.sub.i), where P.sub.i, α, T.sub.i and RPM.sub.i are the values defined for equation (1) hereof, and E.sub.i = the predetermined value of prime mover instantaneous efficiency that corresponds to RPM.sub.i on an ith revolution of the prime mover rotor, ##STR16## where value of prime mover thermal current for the said period, the number of all ith revolutions occurring in the said period, C.sub.i the value defined for equation (2) hereof, ##STR17## where PF is the value of prime mover power factor for the said period, v is a predetermined constant to obtain proper power factor unit, n is the number of all ith revolutions occurring in the said period, P.sub.i is as defined for equation (1), C.sub.i is as defined for equation (2), E.sub.i is as defined for equation (3) and V is value of voltage of the said energizing circuit; and ______________________________________ (c) comparing a parameter value obtained in step (b) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship predetermined indicative of: (i) if the selected parameter is one of prime mover power output, or prime mover modified average current well pump off or a rod string part; (ii) if the selected parameter is prime mover power input: an excessive prime mover power input; (iii) if the selected parameter is prime mover thermal current, to detect: an excessive current load for the prime mover; (iv) if the selected parameter is prime mover power factor: a power factor below an established level.

Claim 10

A method of monitoring for correction the operation of an oil well pumping unit comprising a drive train including a prime mover having a rotor and a power transmission unit having a speed reducer, an energizing circuit for said prime mover, and a reciprocating rod string connected to the plunger of a subsurface well pump, which comprises: (a) determining prime mover rotor instantaneous speeds of revolution for revolutions turned during the period of a complete or predetermined portion of a reciprocation cycle of said pumping unit; (b) applying all or selected RPM i 's from step (a) and accessing at least one set of predetermined values selected from a group of value sets for prime mover T i , C i , E i , P i , P i /E i and P i /E i C i , where the subscript "i" denotes a revolution of the prime mover rotor (an "ith revolution") and where T i means the value of prime mover rotor instantaneous torque that corresponds to RPM i on an ith revolution, RPM i means the value of instantaneous speed of prime mover rotor revolution on an ith revolution, C i means the value of prime mover instantaneous current that corresponds to RPM i on an ith revolution, E i means the value of prime mover instantaneous efficiency that corresponds to RPM i on an ith revolution, and P i means the value of instantaneous power output of the prime mover on an ith revolution and equals αT i (RPM i ) where α is a predetermined constant to obtain proper units, computing the value of at least one parameter of prime mover performance for the said period, said parameter being selected from the group consisting of prime mover PO, MAC, PI, TC and PF, where (1) PO means prime mover power output for the said period, the value of which is given by the equation ##EQU1## in which i and P i have the meanings stated hereinabove in this claim and "n" means the number of prime mover rotor revolutions with respect to which RPM i 's are applied, (2) MAC means prime mover modified average current for the said period, the value of which is given by the equation ##EQU2## in which i, n and C i have the meanings stated hereinabove in this claim, A i is 1 where RPM i on the ith revolution is less than or equal to synchronous speed of the prime mover rotor, and A i is -1 where RPM i on the ith revolution is greater than synchronous speed of the prime mover rotor, (3) PI means prime mover power input for the said period, the value of which is given by the equation ##EQU3## in which i, n, P i and E i have the meanings stated hereinabove in this claim, (4) TC means prime mover thermal current for the said period, the value of which is given by the equation ##EQU4## in which i, n and C i have the meanings stated hereinabove in this claim, (5) PF means prime mover power factor for the said period, the value of which is given by the equation ##EQU5## in which i, n, P i , E i and C i have the meanings stated hereinabove in this claim, v is a predetermined constant to obtain proper power factor units, and V means voltage of said energizing circuit; and (c) comparing a parameter value computed in step (b) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship predetermined indicative of: (i) if the selected parameter is one of prime mover power output, or prime mover modified average current well pump off or a rod string part; (ii) if the selected parameter is prime mover power input: an excessive prime mover power input; (iii) if the selected parameter is prime mover thermal current, to detect: an excessive current load for the prime mover; (iv) if the selected parameter is prime mover power factor: a power factor below an established level.

Claim 14

A method of monitoring for operational correction an oil well pumping unit which comprises a surface drive train including a prime mover having a rotor and a power transmission unit having a speed reducer and a counterbalance, surface structure for changing rotating motion of the prime mover and power transmission unit into reciprocating motion, a subsurface reciprocating well pump, and a rod string for transmitting the surface reciprocation motion and power to the subsurface well pump, comprising the steps of: (a) determining the time for and the instantaneous speed of each prime mover revolution occurring during a downstroke of a reciprocation cycle of the said pumping unit; (b) determining the time for and the instantaneous speed of each prime mover rotor revolution occurring during an upstroke of a reciprocation cycle of the said pumping unit; (c) applying all times for and instantaneous speeds of revolution determined in steps (a) and (b), computing the power transmission unit torque for each prime mover rotor revolution (an "ith revolution"), according to the equation ______________________________________ ##STR18## in which ______________________________________ PTT.sub.i = the value of power transmission unit torque during an ith revolu- tion of the prime mover rotor, RPM.sub.i = the value of the instantaneous speed of prime mover rotor revolu- tion on an ith revolution, RPM.sub.i-1 = the value of the instantaneous speed of prime mover rotor revolu- tion on the prime mover rotor revolution next preceding an ith revolution, .increment.t.sub.i = the time required to execute an ith revolution, T.sub.i = the predetermined value of prime mover rotor instantaneous torque that corresponds to RPM.sub.i on an ith revolution, k = conversion factor constant to obtain proper torque units, I = moment of inertia constant of the said drive train starting at the said prime mover rotor and ending at the said speed reducer of the power transmission unit, ______________________________________ for i=1,2 . . . n revolutions of the prime mover rotor during the said upstroke and for i=1,2 . . . n revolutions of the prime mover rotor occurring during the said downstroke, where n signifies number of prime mover rotor revolutions in respectively said upstroke and said downstroke; (d) determining the maximum PTT i value computed in step (c) for prime mover rotor revolutions occurring during the said upstroke (the "upstroke PTTmax") and determining the maximum PTT i value computed in step (c) for prime mover rotor revolutions occurring during the said downstroke (the "downstroke PTTmax"); (e) comparing said upstroke PTTmax and said downstroke PTTmax to detect whether said upstroke PTTmax and said downstroke PTTmax are unequal; and (f) if upstroke PTTmax exceeds downstroke PTTmax in the step (e) comparison, increasing said counterbalance; (g) if downstroke PTTmax exceeds upstroke PTTmax in the step (e) comparison, decreasing said counterbalance.

Claim 15

A method of monitoring for operational correction an oil well pumping unit which comprises a surface drive train including a prime mover having a rotor and a power transmission unit having a speed reducer and a counterbalance, surface structure for changing rotating motion of the prime mover and power transmission unit into reciprocating motion, a subsurface reciprocating well pump, and a rod string for transmitting the surface reciprocation motion and power to the subsurface well pump, comprising the steps of: (a) determining the time for and the instantaneous speed of each prime mover revolution occurring during a downstroke of a reciprocation cycle of the said pumping unit; (b) determining the time for and the instantaneous speed of each prime mover rotor revolution occurring during an upstroke of a reciprocation cycle of the said pumping unit; (c) applying all times for and instantaneous speeds of revolution determined in steps (a) and (b), computing the power transmission unit torque for each prime mover rotor revolution (an "ith revolution"), according to the equation ______________________________________ ##STR18## in which ______________________________________ PTT.sub.i = the value of power transmission unit torque during an ith revolu- tion of the prime mover rotor, RPM.sub.i = the value of the instantaneous speed of prime mover rotor revolu- tion on an ith revolution, RPM.sub.i-1 = the value of the instantaneous speed of prime mover rotor revolu- tion on the prime mover rotor revolution next preceding an ith revolution, .increment.t.sub.i = the time required to execute an ith revolution, T.sub.i = the predetermined value of prime mover rotor instantaneous torque that corresponds to RPM.sub.i on an ith revolution, k = conversion factor constant to obtain proper torque units, I = moment of inertia constant of the said drive train starting at the said prime mover rotor and ending at the said speed reducer of the power transmission unit, ______________________________________ for i=1,2 . . . n revolutions of the prime mover rotor during the said upstroke and for i=1,2 . . . n revolutions of the prime mover rotor occurring during the said downstroke, where n signifies number of prime mover rotor revolutions in respectively said upstroke and said downstroke; (d) determining the maximum PTT i value computed in step (c) for prime mover rotor revolutions occurring during the said upstroke (the "upstroke PTTmax") and determining the maximum PTT i value computed in step (c) for prime mover rotor revolutions occurring during the said downstroke (the "downstroke PTTmax"); (e) comparing said upstroke PTTmax and said downstroke PTTmax to detect whether said upstroke PTTmax and said downstroke PTTmax are unequal; and (f) if upstroke PTTmax exceeds downstroke PTTmax in the step (e) comparison, increasing said counterbalance; (g) if downstroke PTTmax exceeds upstroke PTTmax in the step (e) comparison, decreasing said counterbalance.

Claim 16

A method of determining instantaneous polished rod loads for use in monitoring, for operational correction, an oil well pumping unit which comprises a surface drive train including a prime mover having a rotor and a power transmission unit having a speed reducer, a crankshaft and a counterbalance; surface structure for changing rotating motion of the prime mover and power transmission unit into reciprocating motion, a subsurface reciprocating well pump, and a rod string including a surface polished rod for transmitting the surface reciprocating motion and power to the subsurface well pump, comprising the steps of (a) determining the time for and instantaneous speed of each prime mover rotor rotation occurring during the period of a complete or predetermined portion of a reciprocation of the said pumping unit, (b) determining the instantaneous position displacement of said polished rod corresponding to selected revolutions of the prime mover rotor occurring during said period, and (c) applying all times for and instantaneous speeds of revolution determined in step (a), computing the instantaneous polished rod load during each prime mover rotor revolution (an "ith revolution") occurring during said period, according to the equation ______________________________________ ##STR19## where ______________________________________ PRL.sub.i = value of instantaneous polished rod load on an ith revolution of the prime mover rotor, n = the number of all ith revolutions occurring in the said period T.sub.i = the predetermined value of the instantaneous motor torque that corresponds to RPM.sub.i on ith revolution m = predetermined value for counterbalance effect ⊖.sub.i = angle of pumping unit crankshaft corresponding to the ith revolution of the prime mover rotor β = predetermined phase angle for counterbalance TF.sub.i = predetermined value of instantaneous torque factor that corresponds to the ith revolution of the prime mover rotor RIT.sub.i = rotary inertia torque affect on prime mover rotor during its ith revolution as given by ##STR20## where I.sub.r = predetermined moment of inertia of rotary elements in said drive train RPM.sub.i = the value of the instantaneous speed of prime mover rotor revolution on an ith revolution, RPM.sub.i-1 = the value of the instantaneous speed of prime mover rotor revolution on the prime mover revolution next preceding an ith revolution, .increment.t.sub.i = the time required to execute an ith revolution AIT.sub.i = articulating inertia affect on motor during its ith revolution as given by ##STR21## where TF.sub.i = as defined hereinabove in this claim I.sub.a = moment of inertia of said surface structure for changing rotating motion into reciprocating motion n = as defined hereinabove in this claim A = predetermined dimension of pumping unit .increment.t.sub.i = as defined hereinabove in this claim PRP.sub.i = position of said polished rod corresponding to ith revolution of prime mover rotor PRP.sub.i+1 = position of polished rod corresponding to revolution of the prime mover rotor immediately following the ith revolution. PRP.sub.i-1 = position of polished rod corresponding to revolution of the prime mover rotor immediately preceding the ith revolution, and S = predetermined constant for structural imbalance of the pumping unit. ______________________________________

Claim 24

A method of determining instantaneous polished rod loads for use in monitoring, for operational correction, an oil well pumping unit which comprises a surface drive train including a prime mover havng a rotor and a power transmission unit having a speed reducer, and a cylinder and piston air pressure counterbalance; surface structure including a walking beam for changing rotating motion of the prime mover and power transmission unit into reciprocating motion, a subsurface reciprocating well pump, and a rod string including a surface polished rod for transmitting the surface reciprocating motion and power to the subsurface well pump, comprising the steps of (a) determining the time for and instantaneous speed of each prime mover rotor rotation occurring during the period, of a complete or predetermined portion of a reciprocation of said pumping unit, (b) determining the instantaneous position displacement of said polished rod corresponding to selected revolutions of the prime mover rotor occurring during the said period, and (c) applying all or selected times for and instantaneous speeds of revolution determined in step (a), computing the instantaneous polished rod load during each prime mover rotor revolution (an "ith revolution") occurring during said period, according to the equation ______________________________________ ##STR22## where PRL.sub.i = value of instantaneous polished rod load on an ith revolution of the prime mover rotor, n = the number of all ith revolutions occurring in the said period T.sub.i = the predetermined value of the instantaneous motor torque that corresponds to RPM.sub.i on ith revolution TF.sub.i = predetermined value of instantaneous torque factor that corresponds to the ith revolution of the prime mover rotor S = air pressure required to offset pumping unit structural unbalance M = predetermined constant relating area of said piston to dimensions of said walking beam PR.sub.i = counterbalancing air pressure corresponding to the ith revolution of the prime mover rotor RIT.sub.i = rotary inertia torque affect on prime mover rotor during its ith revolution as given by ##STR23## where I.sub.r = predetermined moment of inertia of rotary elements in said drive train RPM.sub.i = the value of the instantaneous speed of prime mover rotor revolution on an ith revolution, RPM.sub.i-1 = the value of the instantaneous speed of prime mover rotor revolution on the prime mover revolution next preceding an ith revolution, Δt.sub.i = the time required to execute an ith revolution AIT.sub.i = articulating inertia affect on motor during its ith revolution as given by ##STR24## where TF.sub.i = as defined hereinabove in this claim I.sub.a = moment of inertia of said surface structure for changing rotating motion into reciprocating motion n = as defined hereinabove in this claim A = predetermined dimension of pumping unit Δt.sub.i = as defined hereinabove in this claim PRP.sub.i = position of said polished rod corresponding to ith revolution of prime mover rotor PRP.sub.i+1 = position of polished rod corresponding to revolution of the prime mover rotor immediately following the ith revolution PRP.sub.1-1 = position of polished rod corresponding to revolution of the prime mover rotor immediately preceding the ith revolution. ______________________________________

Claim 29

A method of monitoring for correction the operation of an oil well pumping unit that includes a prime mover having a rotating rotor and a power transmission unit and which reciprocates a rod string including a polished rod, said string being connected to a subsurface well pump, which comprises: (a) determining prime mover rotor instantaneous speeds of revolution for revolutions turned during the period of a complete or predetermined portion of a reciprocation cycle of the said pumping unit, (b) applying all or selected instantaneous speeds of revolution from step (a) to determine the value of at least one parameter of pumping unit performance for the said period selected from the group consisting of prime mover power output, prime mover modified average current, and total polished rod work, (c) comparing the parameter value determined in step (b) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship indicative of cause for stopping operation of the said pumping unit, and (d) stopping operation of said pumping unit when said relationship is detected.

Claim 30

A method of monitoring for correction the operation of an oil well pumping unit that includes a prime mover having a rotating rotor and a power transmission unit and which reciprocates a rod string including a polished rod, said string being connected to a subsurface well pump, which comprises: (a) determining prime mover rotor instantaneous speeds of revolution for revolutions turned during the period of a complete or predetermined portion of a reciprocation cycle of the said pumping unit, (b) applying all or selected instantaneous speeds of revolution from step (a) to determine the value of at least one parameter of pumping unit performance for the said period selected from the group consisting of prime mover power output, prime mover modified average current, and total polished rod work, (c) comparing the parameter value determined in step (b) to a previously established value for the same selected parameter, to detect whether there exists between such values a relationship indicative of cause for stopping operation of the said pumping unit, and (d) stopping operation of said pumping unit when said relationship is detected.