Drilling Engineering & Well Control
Drilling Kill Mud Weight, ICP & FCP Well-Control Formula
Calculate True-Vertical-Depth Hydrostatic Mud Pressure 0.052 * MW * TVD, Required Kill Mud Weight KMW = MW_orig + SIDPP / (0.052 * TVD), Initial Circulating Pressure (ICP), and Final Circulating Pressure (FCP).
Size oilfield kick-control Kill Sheets with TVD—never Measured Depth!
When a drilling rig shuts in its Blowout Preventer (BOP) on an unexpected formation gas/fluid kick and records Shut-In Drill-Pipe Pressure SIDPP (psi), IWCF / IADC Well-Control Kill Sheets use the exact oilfield hydrostatic conversion factor 0.052 psi/(ppg*ft): (1) Original Mud Hydrostatic Pressure is P_hyd = 0.052 * MW_orig * TVD_ft (using True Vertical Depth TVD_ft—NEVER deviated Measured Depth MD_ft, which would under-weight Kill Mud and risk a secondary kick!); (2) Required Kill Mud Weight (ppg) to balance Formation Pore Pressure P_hyd + SIDPP is KMW = MW_orig + SIDPP / (0.052 * TVD_ft) (conventionally rounded up by 0.1 ppg in field execution, or exact balance for pressure-schedule endpoints); (3) Initial Circulating Pressure at Slow Circulating Rate Pressure SCRP is ICP = SCRP + SIDPP; and (4) Final Circulating Pressure once heavy Kill Mud fills the drillstring to the bit is FCP = SCRP * (KMW / MW_orig)!
Verify on True_Vertical_Depth TVD_ft = 10,000 ft (B2), Original_Mud_Weight MW_orig = 10.0 ppg (B3), Shut_In_Drill_Pipe_Pressure SIDPP = 520 psi (B4), and Slow_Pump_Rate_Pressure SCRP = 600 psi (B5): Original Hydrostatic Pressure is 0.052 * 10.0 * 10,000 = 5,200.00 psi (E2, so Formation Pore Pressure = 5,720 psi); Exact Kill Mud Weight is 10.0 + 520 / 520 = 11.00 ppg (E3); Initial Circulating Pressure is 600 + 520 = 1,120.00 psi (E4); and Final Circulating Pressure scales linearly with mud density to 600 * (11.00 / 10.00) = 660.00 psi (E5)!
| Wait-and-Weight Kill Sheet Metric (TVD=10,000 ft, MW=10.0 ppg, SIDPP=520 psi, SCRP=600 psi) | Formula | Verified Output |
|---|---|---|
| Original Hydrostatic Pressure (psi) | 0.052 * MW_orig * TVD_ft | 5,200.00 psi |
| Exact Kill Mud Weight KMW (ppg) | MW_orig + SIDPP / (0.052 * TVD_ft) | 11.00 ppg |
| Initial Circulating Pressure ICP | SCRP + SIDPP | 1,120.00 psi |
| Final Circulating Pressure FCP | SCRP * (KMW / MW_orig) | 660.00 psi |
Kill Mud Weight (KMW) & Final Circulating Pressure (FCP) Formula
Validate TVD_ft > 0, MW_orig >= 7.0 ppg (oil/water base minimum), SIDPP >= 0, and SCRP > 0!
=LET(tv_d, B2, mw_0, B3, si_d, B4, sc_r, B5, IF(OR(tv_d <= 0, mw_0 < 7, si_d < 0, sc_r <= 0), "Invalid Kill Sheet Input", LET(km_w, mw_0 + si_d / (0.052 * tv_d), ROUND(sc_r * (km_w / mw_0), 2))))Balanced Wellbore Sanity Check (SIDPP = 0)
Set SIDPP = 0 in cell B4: KMW equals MW_orig (10.00 ppg) and ICP equals FCP equals SCRP (600.00 psi)!
=IF(ISTEXT(E5), E5, ROUND(B3 + B4 / (0.052 * B2), 2))Try the example
Use the original values or change them to test your understanding.