While monitoring the drilling parameters and maintaining primary control it is also necessary to prepare in anticipation of an influx and consequent loss of primary control. This involves the pre-recording of the relevant information.
1. General Pre-planning
Pre-planning is important to ensure all personnel involved are aware of the action to be taken during well control incidents.
BOP Drills shall be conduction regularly to ensure proficiency of the crew in the detection and handling the loss of primary control over a well. They should focus on the specific tasks of ensuring that:
- relevant warning signs and indications are recognised
- the well is closed in efficiently, restricting any influx volume to a minimum.
2. Personnel Competencies and Preparedness
In order to adequately prepare the wellsite personnel for possible well control situations the following actions should be taken prior to drilling into hydrocarbon bearing formations:
- All personnel to be made aware of the potential hazards that may be encountered when drilling into a charged reservoir.
- Ensure staff are aware of their stations, the role they carry out, and competence to meet the requirements in well control situations.
- BOP and stripdrills (including circulation over the choke) to be held.
- Losses and kick (detection) drills to be practised until the response times (and actions) are to the satisfaction of the Company Drilling Supervisor.
- Ensure Drillers are aware of the need for vigilance regarding kicks and / or losses.
- At the first sign of high torque (or drilling break) stop drilling and ascertain whether a depleted zone has just been encountered.
- Similarly at the first sign of mud losses stop drilling to gauge extent of losses. Keep hole full at all times. When loss rate more than capacity of rig to make new mud, stop circulating, POOH to shoe and immediately fill the annulus water. Prepare LCM pills to cure losses.
3. Routine Daily Precautions
Drilling and Tripping Precautions
During drilling and tripping, the following precautions shall be observed :
- Record slow circulating rates (SCR’s).
- Ensure pit level indicators/alarms are properly set and fully operational.
- Check for flow at each drilling break.
- Make frequent visual checks on pit levels.
- Avoid swabbing or pressure surging on pulling/running pipe.
- Ensure the hole is filled up continuously and that the hole takes the correct amount of fluid every time.
- Monitor the trip tank during trips in the hole to ensure the correct amount of mud is being displaced.
- Watch the hole carefully for signs of loss or flow while under static conditions.
- When blind rams are closed while out of hole, check for pressure before opening.
4. Well Control Data Requirements
Basic well data shall be recorded daily and be easily available. The quality of this pre-recorded data may determine the success of well control operations.
Slow Circulating Pressure/Rate Data
SCR pressure/rate data shall be recorded on the IADC tour report and on the DDR, and shall be posted at the Driller’s position.
Leak Off Test
Formation leak-off tests shall be conducted in accordance with the Company guidelines. The leak-off value shall be used to establish the maximum allowable annular shut-in pressure (MAASP) for well control procedures.
Equivalent Circulating Density (ECD)
The ECD is important when the pressure margins between pore pressure, mud weight and fracture gradient are small. The most appropriate fluid behaviour law for the type of fluid in use shall be used in the calculation.