Trapped Pressure in the SIDPP
Trapped pump pressure can significantly impact the accuracy of shut-in pressure readings during kick handling. Here’s a breakdown of the key points related to trapped pressure:-
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Cause of Trapped Pressure:
Trapped pressure typically occurs when
the driller does not shut down the pumps before closing the Blowout Preventer (BOP). This results in pressure being trapped in the system, leading to abnormally high shut-in pressures.
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Impact on SIDPP and SICP:
The trapped pressure causes both the Shut-In Drilling Pipe Pressure (SIDPP) and Shut-In Casing Pressure (SICP) to read higher than expected. The increase in pressure is equal to the trapped pressure, skewing the kick data. -
Detecting Trapped Pressure:
- Bleed-Off Method: You can check for trapped pressure by slowly bleeding off less than 1 barrel of fluid through the manual choke. This should reveal a permanent drop in the SIDPP, indicating the presence of trapped pressure.
- Equal SIDPP and SICP: If the supervisor traps pump pressure after circulating out the influx, the SIDPP and SICP will be equal. Both pressures will be higher than the original SIDPP, which is caused by the trapped pressure. The trapped pressure should be bled off before proceeding with further operations.
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Post-Kill Scenario:
After successfully killing the well, if the supervisor traps pressure, the shut-in pressures (SIDPP and SICP) will match the trapped pressure. This is normal and doesn’t indicate a second influx of gas or fluid. However, you must confirm the well is dead before opening the BOP, and the trapped pressure should be carefully bled off. -
Other Sources of Trapped Pressure:
Bumping the Bit Float: When determining the SIDPP, bumping the bit float can also cause trapped pressure.- Unexpected Injection: Any unexpected injection into the well during operations could result in trapped pressure.