Precautions During Tripping
Since most blow-outs actually occur during trips, extra care must be taken during tripping. Before tripping out of the hole the following precautions are recommended:
(i) Circulate bottoms up to ensure that no influx has entered the wellbore
(ii) Make a flowcheck
(iii) Displace a heavy slug of mud down the drillstring. this is to prevent the string being pulled wet (i. e. mud still in the pipe when the connections are broken). the loss of this mud complicates the calculation of drillstring displacement.
It is important to check that an influx is not taking place and that the well is dead before pulling out of the hole since the well control operations become more complicated if a kick occurs during a trip. When the bit is off bottom it is not possible to circulate mud all the way to the bottom of the well. If this happens the pipe must be run back to bottom with the BoP’s closed. this procedure is known as stripping-in and will be discussed later.
As the pipe is tripped out of the hole the volume of mud added to the well, from the trip tank, should be monitored closely. to check for swabbing it is recommended that the drillbit is only pulled back to the previous casing shoe and then run back to bottom before pulling out of hole completely. this is known as a short trip. Early detection of swabbing or incomplete filling of the hole is very important.
%
Drilling ahead
|
H. C. show in circulating mud |
|
Volume increase in pits |
|
Drilling break |
|
Flowrate increase |
Raise Kelly above rotary
Stop pump
|
NO |
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Well flowing? |
|
Drill ahead |
|
Close Hydril |
YES
Flow check as necessary
Note Pdp and Pann Note Pit Gain Calc. Nature of Influx Calc. New Mud Weight to balance Form. Pressure
Kill well
Drill ahead
Figure 7 Operational Procedure following detection of a kick
Exercise 2 Response to a kick
Whilst drilling the 8 1/2" hole of the well the mud pit level indicators suggest that the well is flowing.
a. What action should the driller take?
b. What action should the driller take if he was pulling out of hole at the time that the kick was recognised?
c. What other indicators of a kick would the driller check for?
When considering the above, also consider the sequence of operations and the possible misinterpretations of the indicators.