Choke Line Friction pressure (CLF) has directly affect on the bottom hole pressure while performing well kill operation in a deepwater operation. You may be able to circulate the kick out of the well without breaking the shoe down with the current mud weight however; the well can be fractured when the kill weight mud reaches the surface due to excessive CLF.
How Kill Weight Mud and CLF Will Break the Shoe
When the kill mud is circulated from the bit to surface as per the second circulation of driller’s method, drill pipe pressure is held constant and the choke is gradually opened. Once the choke is in the fully open position, the back pressure due to choking back the well is gone but the CLF is still there. With the heavier weight, the CLF with KWM will be more than the CLF with the original mud. If the hydrostatic pressure is more than the fracture pressure, the formation will be broken down. Let’s take a look at the following calculation to get clearer picture of this topic. Continue reading
Choke line friction pressure will increase bottom hole pressure while circulating to kill the well therefore it must be compensated in order to maintain the bottom hole pressure relatively constant. This section will describe how to compensate the choke line friction while bring pump up to speed.
Choke Line Friction is one of critical figures that personnel on the rig need to know and this numbers can be determined.
The procedures for the choke line friction determination are as follows;
Choke line friction (CLF) is the frictional pressure which is generated while circulating mud through choke or kill line. For surface stack, the choke line friction is negligible because the choke line is short therefore the friction pressure is so small. However, the choke line friction in deepwater operation has a big effect bottom hole pressure. Killing the well without considering the CLF will add excessive pressure and it increases the chance of fracturing formation at casing shoe or anywhere in the well.