Drilling cost indicator

Claim 2

Apparatus for the analog computation of drilling variables associated with a rotary drill rig comprising means (a) for generating a voltage in a circuit directly proportional to R , where R is the rate of rotation of the rotary table of said rig and Alpha is an exponent relating drill bit life with rate of rotation of said bit, means (b) for generating from said voltage a second voltage varying directly as W , where W is the weight on the drill bit of said drill rig and Beta is an exponent relating drill bit life with weight on said bit, means (c) for generating from said second voltage a third voltage varying directly with the time t required to drill with said bit and said drill rig a unit distance in the ground, and an impedance (d) large compared with that of said means (c) connected in a closed circuit in series with the output of said means (c), in such a fashion that the total impedance in said circuit is substantially that of said impedance (d), whereby the current in said circuit varies as R W t.

Claim 3

Apparatus for the analog computation of drilling variables associated with a rotary drill rig comprising means (a) for generating a voltage in a circuit directly proportional to R , where R is the rate of rotation of the rotary table of said rig and Alpha is an exponent relating drill bit life with rate of rotation of said bit, means (b) for generating from said voltage a second voltage varying directly as W , where W is the weight on the drill bit of said drill rig and Beta is an exponent relating drill bit life with weight on said bit, means (c) for generating from said second voltage a third voltage varying directly with the time t required to drill with said bit and said drill rig a unit distance in the ground, and a high impedance recording voltmeter, the impedance of which is large compared to that measured across the output of means (c) in the absence of said voltmeter, said recording voltmeter including a strip record and means for printing an indication of the voltage generated by means (c) on said strip record as drilling progresses.

Claim 4

Apparatus for the analog computation of drilling variables associated with a rotary drill rig comprising means (a) for generating a voltage in a circuit directly proportional to R , where R is the rate of rotation of the rotary table of said rig and Alpha is an exponent relating drill bit life with rate of rotation of said bit, means (b) for generating from said voltage a second voltage varying directly as W , where W is the weight on the drill bit of said drill rig and Beta is an exponent relating drill bit life with weight on said bit, means (c) for generating from said second voltage a third voltage varying directly with the time t required to drill with said bit and said drill rig a unit distance in the ground, and a high impedance recording voltmeter, the impedance of which is large compared to that measured across the output of means (c) in the absence of said voltmeter, said recording voltmeter including a strip record and means for printing an indication of the voltage generated by means (c) on said strip record as drilling progresses.

Claim 5

Means for computing and recording drilling variables associated with a rotary drill rig comprising means (a) for successively generating a voltage directly proportional to R W t where R is the rate of rotation of the rotary table of said rig, Alpha is an exponent relating drill bit life with rate of rotation of said bit, W is the weight on the drill bit of said drill rig, Beta is an exponent relating drill bit life with weight on said bit, and t is the time to drill with said bit and said rig a uniform distance in the ground, for a succeSsion of such uniform distances, means (b) responsive to said means (a) for generating a second potential directly proportional to the successive sum of a plurality of said voltages from means (a), an adjustable impedance (c) large compared with that of said means (b) connected in series with the output from said means (b), and a recording current meter connected in series with said impedance (c) and the output of said means (b) to complete a series circuit, said meter being adapted to record on a moving strip record separately the value of the current in said circuit for each of a plurality of times corresponding to each said successive sum.

Claim 6

Means for computing and recording drilling variables associated with a rotary drill rig comprising means (a) for successively generating a voltage directly proportional to R W t where R is the rate of rotation of the rotary table of said rig, Alpha is an exponent relating drill bit life with rate of rotation of said bit, W is the weight on the drill bit of said drill rig, Beta is an exponent relating drill bit life with weight on said bit, and t is the time to drill with said bit and said rig a uniform distance in the ground, for a succeSsion of such uniform distances, means (b) responsive to said means (a) for generating a second potential directly proportional to the successive sum of a plurality of said voltages from means (a), an adjustable impedance (c) large compared with that of said means (b) connected in series with the output from said means (b), and a recording current meter connected in series with said impedance (c) and the output of said means (b) to complete a series circuit, said meter being adapted to record on a moving strip record separately the value of the current in said circuit for each of a plurality of times corresponding to each said successive sum.

Claim 7

Apparatus for the analog computation of drilling variables associated with a rotary drill rig comprising means (a) for generating a voltage in a circuit directly proportional to R , where R is the rate of rotation of the rotary table of said rig and Alpha is an exponent relating drill bit life with rate of rotation of said bit, means (b) for generating from said voltage at the output from said means (a) a second voltage varying directly as W , where W is the weight on the drill bit of said drill rig and Beta is an exponent relating drill bit life with weight on said bit, means (c) connected to the output from means (b) for generating from said second voltage a third voltage varying directly with the time t required to drill with said rotary drill rig a unit distance in the ground, means (d) connected to the output of means (c) for generating from said third voltage a fourth voltage varying directly as the sum of the cost of said bit and the cost to place said bit at the bottom of the well being drilled by said rig, an adjustable impedance (e) in series with the output from said means (d) and large compared with the output impedance of said means (d), a first amplifier (f) closing a circuit with the output of said means (d) and said impedance (e), for producing an output voltage directly proportional to the current in said circuit, means (g) for producing a fifth voltage directly proportional to the product of rig cost per unit time interval times the time required to drill with said bit and said drill rig said unit distance in the ground, a second amplifier (h) of substantially the same gain as that of said first amplifier (f), the input to which is connected to the output of said means (g) and the output of which is connected additively in series with that of said first amplifier (f), and a recording voltmeter connected in series with the outputs of said first amplifier (f) and said second amplifer (h), said voltmeter being adapted to record on a moving strip record the sum of the output voltage of said first amplifer (f) and said second amplifier (h) at a plurality of times corresponding to the successive driling of each of a plurality of integral multiples of said unit distance.

Claim 8

Apparatus for the analog computation of drilling variables associated with a rotary drill rig comprising means (a) for generating a voltage in a circuit directly proportional to R , where R is the rate of rotation of the rotary table of said rig and Alpha is an exponent relating drill bit life with rate of rotation of said bit, means (b) for generating from said voltage at the output from said means (a) a second voltage varying directly as W , where W is the weight on the drill bit of said drill rig and Beta is an exponent relating drill bit life with weight on said bit, means (c) connected to the output from means (b) for generating from said second voltage a third voltage varying directly with the time t required to drill with said rotary drill rig a unit distance in the ground, means (d) connected to the output of means (c) for generating from said third voltage a fourth voltage varying directly as the sum of the cost of said bit and the cost to place said bit at the bottom of the well being drilled by said rig, an adjustable impedance (e) in series with the output from said means (d) and large compared with the output impedance of said means (d), a first amplifier (f) closing a circuit with the output of said means (d) and said impedance (e), for producing an output voltage directly proportional to the current in said circuit, means (g) for producing a fifth voltage directly proportional to the product of rig cost per unit time interval times the time required to drill with said bit and said drill rig said unit distance in the ground, a second amplifier (h) of substantially the same gain as that of said first amplifier (f), the input to which is connected to the output of said means (g) and the output of which is connected additively in series with that of said first amplifier (f), and a recording voltmeter connected in series with the outputs of said first amplifier (f) and said second amplifer (h), said voltmeter being adapted to record on a moving strip record the sum of the output voltage of said first amplifer (f) and said second amplifier (h) at a plurality of times corresponding to the successive driling of each of a plurality of integral multiples of said unit distance.