Driller’s method is one of several methods to kill the well. The main idea of driller method is to kill the well with constant bottom hole pressure. The Driller’s Method of well control requires two complete and separate circulations of drilling fluid in the well.
The first circulation removes influx with original mud weight. When starting to bring pumps up to speed, casing pressure must be held constant until kill rate is reached. Then drillpipe pressure is held constant to maintain constant bottomhole pressure which is normally equal to, or slightly greater than pore pressure. Drillpipe pressure will be held constant until influx is removed from annulus. If the wellbore influx is gas, it will expand when it comes close to surface therefore you will see an increase in pit volume and casing pressure.
After the kick is totally removed from the well, when the well is shut-in, drillpipe and casing pressure will be the same value. If not, it means that there is influx still left in the wellbore or trapped pressure.
Before going to the second circulation, we need to know kill mud weight which can be calculated from initial shut-in drillpipe pressure. The calculation part will be discussed as in next section.
Second circulation kills well with kill mud. When the required kill mud weight is mixed, it is the time to start the second circulation of driller method. We start with bringing pumps to kill rate by holding casing pressure constant. While circulating with the kill mud, casing pressure must be held constant until kill mud reaches the bit. After that, we need to hold drill pipe pressure constant then continue circulating with constant drill pipe pressure until kill mud weight reaches at surface. Then shut down pumping operation and observe drillpipe and casing pressure. If the well is successfully killed, both drillpipe and casing pressure will be zero. If not, there is some influx still in the well.