Drilling Well Control
Drilling Well Control is the core domain of IWCF Level 3 DWC. It tests whether you can detect an influx, shut the well in correctly, and kill it using calculated pressures rather than guesswork. Level 3 expects you to work the numbers and explain the reasoning, not just recite a procedure.
Core rules and concepts
- Barriers: the hydrostatic column is primary; the BOP stack, choke manifold, kill line and IBOP are secondary. Each must be verified independently.
- Kick indicators: pit gain, flow with pumps off, rising return flow, falling pump pressure at constant rate, connection gas.
- Shut-in: stop rotary, stop pumps, close the BOP, then read SIDPP and SICP on stabilised gauges. Record both, plus pit gain and the slow circulating rate.
- Kill mud weight: KMW = OMW + SIDPP ÷ (TVD × 0.052) for psi, ppg and feet.
- Pressures: ICP = SIDPP + SCRP; FCP = SCRP × KMW ÷ OMW.
- MAASP = (maximum allowable MW − current MW) × 0.052 × casing shoe TVD, recalculated as kill mud enters the annulus.
Worked example
10.0 ppg mud, TVD 10,000 ft, SIDPP 520 psi, SICP 700 psi, SCRP 500 psi at 30 spm.
KMW = 10.0 + 520 ÷ (10,000 × 0.052) = 10.0 + 520 ÷ 520 = 11.0 ppg. FCP = 500 × 11.0 ÷ 10.0 = 550 psi. ICP = 520 + 500 = 1,020 psi.
Reasoning: 520 psi ÷ 520 psi per ppg equals 1.0 ppg of extra mud weight, so formation pressure is an 11.0 ppg equivalent. Bringing the pump to 30 spm while holding casing pressure at SIDPP drops drill-pipe pressure to ICP; from there, holding drill-pipe pressure on the schedule keeps bottomhole pressure just above formation pressure.
Traps that cost marks
- Using measured depth instead of TVD - on a deviated well this understates kill mud weight.
- Quoting SIDPP as a mud weight without converting it.
- Swapping ICP and FCP in the answer.
- Assuming MAASP is fixed; it falls as heavier kill mud fills the annulus.
- Bringing the pump to kill rate without holding casing pressure, letting a second influx in.