Method and apparatus for pipe joint locator, counter and displacement calculator

The invention is a novel method and apparatus for counting pipe joints, passing through a bell nipple, going downhole and uphole by sensing, at spaced apart positions along the nipple utilizing magnetic fields, for the presence of a joint. Each sensor develops signals as the joint passes it and a logical network determines which direction the pipe joint is traveling, adds a plus count to the joint counter for joints going downhole and subtracts a minus count from the joint counter when a joint is sensed coming uphole. Another logical circuit converts the joint count to a stand count, and the negative signals from the stand count trigger an adder network to introduce a binary number to a numeric read-out display, which number is indicative of pipe displacement per stand, withdrawn from hole.

PRIOR ART 
The prior art reveals no such logical networks as are herein disclosed. The 
U.S. Pat. No. 3,646,808 to Leonard detects the amount of fluid required to 
replace the steel of the pipe removed from the drill hole, and 
automatically replaces same. U.S. Pat. No. 3,843,923 to de Vries et. al. 
uses a pair of Hall effect detectors for pipe joint location, and U.S. 
Pat. No. 3,803,797 to Abtukin et. al. checks continuity of pipe sections. 
The present invention employs three magnetic pickup units at spaced apart 
locations to develop signals indicative of pipe joints passing the 
respective pickup units. The pickup units are vertically spaced apart on 
the bell nipple to provide directional information, because if a joint 
moves downhole, through the bell nipple, it will develop a signal at 
pickup unit 1 first, then pickup unit 2 and then pickup unit 3. However, 
if the joint is coming out of the hole the pickups will be tripped in the 
reverse order. 
Pneumatic or electrical logic is utilized to add or subtract a count at the 
joint counter depending upon the direction of movement of the pipe. The 
add and subtract logic circuits are identical but inverted and hence 
provide both the add and subtract signals. 
A three position, two way valve or switch is provided to accommodate a 
number of joints per stand. The switch has three inputs for a positive 
count and three inputs for a negative count and it is set to indicate the 
number of joints per stand and influence the count accordingly. If, for 
example, there are three joints per stand, then the switch will be set to 
three and after the third joint has passed the joint locator, a count will 
be registered on the stand counter such that the stand counter registers a 
count every third joint. Also the same logic subtracts a count from the 
stand counter when three joints have been removed from the hole. 
The system also provided for a circuit for displaying mud displacement 
amounts. This tells how much mud must be pumped into the hole as drill 
pipe is withdrawn when removing pipe from the hole. 
A five position valve or switch is used to set a binary number into the 
tenths and hundredths stages of the adders, which display, (via seven bar 
encoders) the numbers indicating the mud displacement. It is a five stage 
adder capable of counting and displaying 999.99, but the principles herein 
taught are applicable to other capacity adders. 
The triggering inputs to the adder sections are the negative counts from 
the stand counter, and accordingly, the five position valve or switch is 
manually set to insert a binary number into the tenths and hundredths 
stages which represents the displacement per stand of a particular size 
and weight drill pipe. This number is inserted automatically each time a 
negative count is received. Obviously, this information could be utilized 
on a per joint basis, if desired. 
Thus, the binary number set into the adders which represents the 
displacement per stand, will be added to the total each time a stand is 
removed from the hole. The calculated displacement number is displayed on 
the face of the instrument panel, as being representative of the total 
volume of mud which should have been pumped into the hole at any given 
time. 
This number can be compared to the actual mud pumped, or can be used to 
actuate an automatic fill-up system.

The three pickup units labeled PU1, PU2 and PU3 are shown in FIG. 1 against 
bell nipple 101 through which pipe 102 having a joint 103 is passing. 
Each pickup unit is comprised of the components shown in FIG. 2, being a 
bar magnet 104, coil 105 and similar bar magnet 106, with the coil 
interposed between the magnets. It should be noted that the magnetic poles 
of bar magnets 104 and 106 oppose each other, i.e. South of South. This is 
similar to designs used in casing collar locators for downhole tools. 
Since the poles of the magnets oppose each other, the flux patterns from 
the two magnets intersect the coil in a perpendicular manner as shown in 
FIG. 3. The presence of a drill pipe 102 will not upset the symmetrical 
pattern of the flux, therefore the output from the coil 105 will be zero 
volts. 
As a joint 103 approaches the locator pickup unit, the increased mass of 
the joint attracts the flux from the upper magnet (as seen in FIG. 4), 
causing the flux pattern of both magnets to move upward. The movement of 
the flux perpendicular to the centerline of the coil 105 causes a voltage 
to be generated inside the coil 105. This voltage is the signal which 
indicates the presence of a pipe joint. 
As a joint moves downhole, through the bell nipple 101, it will trip pickup 
#1, then pickup #2, then pickup #3, in that order. If the joint is coming 
out of the hole, the pickups will be tripped in the reverse order. 
In FIG. 1 a block diagram is shown of the overall system wherein the three 
units actuate respectively solenoid valves 107, 108 and 109. The 
electrical signals generated in the pickup coils 105 are transferred to 
solenoid valves 107, 108 and 109, serving to open these valves in 
sequence. 
The system will be explained as employing pneumatic components, but their 
equivalents in electrical circuits can be substituted to make an all 
electric control system. 
The signals from solenoid valves 107, 108 and 109 are processed in 
add-subtract logic counters (block 110) which includes reset buttom 111. 
Block 110 includes both the joint counter and stand counter of FIG. 5. 
The input triggering signals to the adder circuits are the negative counts 
to the stand counter, which appear on lead 112 and trip the appropriate 
stages 113-117 of the adder circuitry for display of the displacement 
number on read-out panel 118. 
Five position valve switch 27 puts in the correct binary number into adder 
stages 116 and 117 in accordance with the displacement per stand for five 
different pipe sizes. This binary number is added for each negative stand 
trigger count, such that read-out panel 118 indicates the actual mud 
displacement at any given time. 
The logic diagram shown in FIG. 5 indicates the pickups actuating the three 
solenoid operated air valves, and the rest of logic is pneumatic. The 
basic logic would be the same if the system were entirely electric, 
however. 
As a joint moves downhole, it trips pickup #1 first. This causes an output 
from valve #1. Look first at the upper circuit which is the add portion. 
Valve #1 triggers flip-flop 1 and goes through OR gate 4 to insure that 
flip-flop 3 is turned off. The output of flip-flop 1 goes to AND gate 2. 
When valve #2 fires, its output goes to AND gate 2 and turns on flip-flop 
3, which sends a signal to AND gate 5. 
When valve #3 fires, its output goes to turn off flip-flop 1 and also goes 
to AND gate 5. The output from AND gate 5 is a pulse which is used to add 
one joint on the joint counter 11. The output from gate 5 also goes 
through OR gate 4 to turn flip-flop 3 off. 
Now looking at the lower position of the counter diagram as the joint goes 
downhole, this portion is the subtract circuit. 
Valve #1 fires first, turning off flip-flop 10, and also sending a signal 
to AND gate 6. Since there is no signal from flip-flop 8, there is no 
output from gate 6. When valve #2 fires, it sends a signal to AND gate 9, 
but since there is no output from flip-flop 10, gate 9 has no output, thus 
flip-flop 8 still has no output. When valve #3 fires, it turns on 
flip-flop 10, and goes through OR gate 7 to keep flip-flop 8 turned off. 
Thus, there is never a signal out of AND gate 6. The output from gate 6 is 
the signal to subtract a joint from the counter. 
Therefor, as a joint moves downhole, there is a pulse out of the add 
circuit, and no pulse out of the subtract circuit. Since the add and 
subtract circuits are identical, but inverted, when a joint comes out of 
the hole, the subtract circuit sends a pulse to joint counter 11. 
The joint counter is a count up and down counter, thus it will keep 
accurate count of the joints in the hole at all times. 
The add and subtract pulses are also fed into a binary counter consisting 
of two binary counter modules 22 and 26. 
These modules are connected by means of AND gates 23 and 25, and OR gate 
24. This allows the binary counter to count both up and down. The outputs 
of the two modules connect to AND gates 18, 19 and 20. The outputs of 
these gates represent the counts 1, 2 and 3 respectively. 
The counter will be set at zero by pressing the reset push bottom 17. Thus, 
the counter will always start at zero. 
If the drill pipe is going into the hole, there will be an add pulse into 
the binary counter each time a joint passes the joint locator. The first 
pulse will cause an output from AND gate 18. The third pulse will cause an 
output from AND gate 20. 
The outputs from these gates go to the ports of a 3 position, two way valve 
or switch 12. The switch has three inputs for a positive count, and three 
inputs for a negative count. 
This switch is set to indicate the number of joints per stand. Assume there 
are three joints per stand, then the switch will be set as shown in the 
diagram. 
After the third joint has passed the joint locator, there will be an output 
from AND gate 20. This output will go through switch 12, since it is set 
on three joints per stand, pass through AND gate 14, and register a count 
on the stand counter 15. The signal will also go through OR gate 16 and 
reset the binary counters to zero. Thus, the stand counter will register a 
count every third joint. 
The same logic subtracts a count from the stand counter when three joints 
have been removed from the hole. 
The last part of the system consists of the circuit of FIGS. 6 and 7 for 
displaying how much mud must be pumped into the hole as drill pipe is 
withdrawn when tripping the hole. 
A five position valve or switch 27 is used to set a binary number into the 
adder system. Each position will represent the displacement per stand or 
per joint of a particular size and weight drill pipe. 
By use of the OR gates, 28, 29, and 30, the proper binary number will be 
set into the adders. When the stand counter is pulsed, it will actuate the 
transfer flip-flops. This will transfer the number from the adders to the 
flip-flops. 
The output from the flip-flops go to a seven bar encoder, which encodes the 
number and displays the number on the numeric read-outs. 
The outputs from the flip-flops is also fed back into the adders, to be 
added to the original binary number set into the adder by the switch 27. 
Thus, the original number set into the adders, which represents the 
displacement per stand, will be added to the total each time a stand is 
removed from the hole. This number will be displayed numerically on the 
face of the panel, and will represent the total volume of mud which should 
have been pumped into the hole at any given time. 
This number can be compared to the actual mud pumped, or can be used to 
actuate an automatic fill up system. 
By adding additional binary adders to the circuit, and having them 
triggered by the positive stand count rather than the negative count, the 
system can be made to calculate and display the volume of mud which should 
be displaced from the hole when the drill pipe is going into the hole. 
If binary subtracters were added to the original system, and pulsed by the 
positive stand count, the system would accurately display the total mud 
required for the hole at all times, whether going in or coming out of the 
hole.