Wait and Weight Method:

The ‘Wait and Weight method,’ also known as the ‘Engineer’s method,’ aims to control a well in one circulation. It involves displacing the kill-weight mud into the drill string to remove the wellbore influx. This method requires meticulous calculations and pressure monitoring to achieve safe and effective well control.

The process involves several essential steps:

1. Well Shut-in: The well is shut in to stop the flow of formation fluid into it as soon as a kick is detected. Soft Shut-in or Hard Shut-in methods can be adopted depending on company policies.

2. Pressure Stabilization and Data Recording: After allowing some time for them to stabilize, the shut-in drill pipe (SIDP) pressure, Shut-In Casing Pressure (SICP), and pit gain are recorded.

3. Well Control Calculations: Based on stabilized pressures and well configuration details, various crucial calculations are made, including the bottom hole pressure, MAASP, kill mud weight requirement to balance the formation pressure, pump strokes requirement, etc. A drill pipe pressure schedule is prepared, ensuring the bottom hole pressure is kept above the formation pressure through the well-killing process.

4. Mud Weight Adjustment: Based on the calculations, the system's mud weight is increased to the necessary kill mud weight.

5. Pump start-up to circulate kill mud: The pump is started gradually with five strokes per minute to reach the required kill rate. The choke valve is manipulated to ensure that the bottom hole pressure remains constant during this step, keeping the casing pressure constant.

6. Pumping kill mud: Kill-weight mud is pumped through the drill pipe at the kill rate. The drill pipe pressure schedule is followed until the kill weight mud reaches the bit by manipulating the choke valve.

7. Constant Drill Pipe Pressure: Once the kill weight mud reaches the bit, the drill pipe pressure is maintained constant for the rest of the cycle. Maintaining the planned pressure schedule ensures that the bottom hole pressure remains equal to or slightly higher than the formation pressure, thus avoiding a secondary kick situation.

8. Gas Expansion: In the case of a gas kick, a controlled gas expansion occurs in the annulus. Due to gas expansion, casing pressure and pit volume should increase. It is important to hold the drill pipe pressure and pump rate at the predetermined level to maintain the bottom hole pressure above the formation pressure.

9. Mud weight verification: After completing the circulation cycle, verify that the outcoming mud weight is the same as the kill mud weight.

10. Shutdown and Flow Check: Once the circulation is completed, pumps are shut down to flow check and confirm that the well is stable.

11. Mud Conditioning: If necessary, mud circulation and conditioning are carried out until satisfactory mud properties are attained.