Kick_Prevention

Kick Prevention n

Primary Well Control.

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Tripping Practices.

Kick Prevention At the end of this section you should be able to: n

Describe primary well control and practices to prevent a kick.

Kick Prevention Maintenance of primary well control is the foundation of kick prevention, which is ensured by the use of a drilling or completion fluid of sufficient density to overbalance the highest exposed formation pressure.

Primary Well Control: The hydrostatic pressure acting against a formation primarily comes from the weight of the drilling fluid used. A drilling fluid density that will maintain a minimum overbalance of 200 psi, or 50 psi with the marine riser removed (operations with subsea BOPs) is recommended. It is of the utmost importance to ensure that primary well control is maintained at all times. This involves the following: – – – – –

Drilling fluids of adequate density are used. Well is kept full of adequate density fluid at all times. Determining a maximum tripping speed based on swab / surge calculations. Active volumes are continuously monitored, especially during tripping. Changes in density, volumes and flow rate of drilling fluids from the wellbore are immediately detected and appropriate action taken.

Kick Prevention Tripping Practices: Statistics show that the majority of kicks are taken while pulling the drill string from the wellbore. This is a problem that can be avoided if the crew is well trained and if proper procedures are followed. During tripping, the potential exists for a significant reduction in bottomhole pressure due to the following effects: – – –

Swabbing during trips. Not adequately filling the hole during a trip. Insufficient drilling fluid density (remove of ECD).

The following guidelines are the preparations for a trip: – – – – – –

Check hole conditions. Flow checks. Slugs. Mud bucket. Trip tank Trip sheet.

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Filling drill pipe. Proper hole file. Tripping speed. Breaking circulation. Trip interruptions. Save valve.

Kick Prevention Check Hole Conditions. Before starting tripping out of the hole with drill pipe, the drilling fluid shall be in good condition: no indication of lost circulation, no indication of influx of formation fluids present prior to pulling pipe, the drilling fluid density in and out will not differ more than 0.2 ppg. n Flow checks. A flow check is the observation of the well without circulation. Flow checks are made to determine if the well is, or is not flowing. A flow check will not prevent a kick, it will indicate whether the well is stable or not. n Slugs. When possible, and after a flow check has confirmed that the well is static, a slug will be prepared and displaced in the drill string prior to POOH n Mud Bucket. Should be readied if a slug cannot be pumped or if pipe must be pulled wet. Design should be arranged so that returns from the mud bucket drain to the trip tank. n

Kick Prevention Trip Tank. A trip tank is a low-volume, (100 barrels or less), calibrated tank that can be isolated from the remainder of the surface drilling fluid system and must be used to keep track of fluid volumes while both tripping in and tripping out of the hole, making sure that the borehole is kept full at all times. n Trip Sheet. In conjunction with the trip tank, a trip sheet must always be used while tripping in and out of the hole. n Filling Drill Pipe. With a solid float in the string, drill pipe will need to be manually filled at surface at a maximum of every 10 to 15 stands while RIH. With the BHA in open hole, reciprocating is recommended while filling the pipe to avoid sticking problems. n Proper Hole Fill. If the hole is not taking the proper amount of fluid, it is important to stop tripping and flow check. The pipe should be returned to bottom, another flow check performed and a minimum of one bottom’s up should be circulated. n

Kick Prevention Tripping Speed (Swabbing / Surging). Pipe shall not be pulled faster than the speed that would cause excessive swabbing. Similarly, pipe shall not be run in the hole faster that the speed that will generate surge pressures that can cause formation breakdown leading to losses. Swab and surge calculations should be performed for each trip in and out of the hole. n Breaking Circulation. To reduce possibilities of high surge pressures, break circulation whenever necessary (prior to and after entering open hole). n Trip Interruptions. Any time a trip is interrupted, the installation of a Full Opening Safety Valve is required. n Safety Valve. Suitable safety valves with appropriate connections of crossover subs to fit all drill pipe and BHA connections must be on the rig floor, in the 'open' position ready for use with proper fittings and handling devices.

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