SECTION 7
"SECOND KICK" CAN OCCUR WITHOUT DRILLING MORE HOLE
This section is a continuation of Problem 6. The well was killed, but because supervision was relaxed, another gas bubble was let into the bottom of the hole. The second gas kick arrives at the surface to find everyone unprepared, and unloads the hole.
Key points. When gas from a well gets to the surface before the well is shut in, very high casing pressures can be expected.
It is also not uncommon for the drillpipe pressure to be high because some of the mud has fallen out of it.
In the rules for pressure control, it was explained that if the drillpipe pressure did not seem correct, open the choke a bit and pump into the drill pipe for several minutes. Then shut the pump off and close the choke. 747g619h
If the SIDPP is less than before you pumped, the drill pipe was partly empty of mud. It must be filled before you will get correct values.
Problem 7-0
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Problem facts:
You are circulating and conditioning mud from problem 6. You have turned off the flowline sensor and pit volume sensor alarms because they keep blowing. The mud shoots up on the floor with a roar, and the flow line blows off. You shut the well in while it still is kicking. The drillpipe pressure bothers you because you just killed a kick, but you haven't drilled any more hole. What has happened?
Problem 7-1
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Before you do anything else, you decide to check on the drillpipe pressure because it doesn't seem right that you should have to increase the mud density by 1.7 ppg (0.204 SG, 13 lb/ft3). You open the choke just a little and pump for 252 strokes. They you shut the pump off and close the choke. 747g619h
What has happened?
Problem 7-2
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You got in trouble in Problem 6 for not paying attention, so you are going to try once more to see if the drillpipe pressure will go to 0. You open the choke a little and pump 18 strokes then turn the pump off and close the choke. 747g619h The casing pressure is still going up. Now what is the situation?
What should you do:
1 Start the pump and hold casing pressure constant?
2 Pump at 38 spm and 1320 psi (93 kg/cm2) (the same as before this kick occurred)?
3 Increase the mud density to 15.7 ppg (1.884 SG, 117 lb/ft3)?
4 Wait on orders?
Problem 7-3
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Now what is wrong? The casing pressure is going out of sight. Should you open the choke more?
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
Problem 7-4
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The casing pressure is still going up. Should you slow the pump?
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
Problem 7-5
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Now things are a little confusing. Everything is going down. You need to increase or decrease something. On top of that, the pits are running over and there is mud all over the location.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
Problem 7-6
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The derrickman says that the pits have stopped running over, but there is no mud coming out of the separator - just gas.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
Problem 7-7
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The derrickman says that you are out of mud in the pits. Have you lost circulation?
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
Problem 7-8
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You have mixed 300 bbl (48 m3) of mud with a density of 14.3 ppg (1.714 SG, 107 lb/ft3) and started circulating again. The derrickman says that the mud level in the pits is going down and no mud is coming out of the choke/separator line.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
Problem 7-9
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The pits are still going down and so is everything else.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
Problem 7-10
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You have been pumping long enough to get all the gas out of the hole. The mud coming from the separator line is not gas cut. What is wrong? The annulus pressure is still not O.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase pump rate?
4 Decrease pump rate?
5 Everything is OK - continue?
6 Stop the pump and close the well in?
ANSWERS
Problem 7-0: In the previous problem you were not paying attention and let another bubble in the hole - a second kick. Now you have circulated it up to the surface and it unloaded the mud in the hole.
Problem 7-1: The drill pipe is starting to fill up. Now you know that you probably don't have to increase the mud density.
Problem 7-2: Pump at 38 spm and 1320 psi (93 kg/cm2). This was the FCP from the last problem. This is the circulation pressure at 38 spm that you would have if the hole was full of mud at 14.3 ppg (1.713 SG, 107 lb/ft3).
Problem 7-3: Everything is OK - continue. You let a lot of gas in the hole when it unloaded at the surface. The casing pressure will get very high. Remember however, casing was set at 9800 ft (2987 m) so the pressure below the casing is showing very little change.
Problem 7-4: Everything is OK - continue. You have a lot of gas in the hole - about 300 bbl (48 m3). Stay with it!
Problem 7-5: Increase the pump rate - you can only solve one problem at a time. Pump rate must be constant.
Problem 7-6: Increase the choke size. No matter what happens you have to follow the basic rules - constant pump strokes and constant drillpipe pressure.
Problem 7-7: Stop the pump and close the well in. You don't have any choice. If you are out of mud you must mix more. With a large kick, the gas displaces so much mud out of the hole that the pits will run over and often there will not be enough mud left to fill the hole again.
Problem 7-8: Everything is OK - continue. You still don't have all the gas out of the hole and mud is still being pumped into the hole to replace the gas.
Problem 7-9: Increase the pump rate. Keep pump strokes and drillpipe pressure constant.
Problem 7-10: Increase the choke size. You are causing the annulus pressure by too small a choke size.
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