What is Primary Well Control?

Primary Well Control is hydrostatic pressure provided by drilling fluid more than formation pressure but less than fracture gradient while drilling. If hydrostatic pressure is less than reservoir pressure, reservoir fluid may influx into wellbore. This situation is called “Loss Primary Well Control”.

Not only is hydrostatic pressure more than formation pressure, but also hydrostatic pressure must not exceed fracture gradient. If mud in hole is too heavy, it will cause a broken wellbore, you will face with loss circulation problem (may be partially lost or total lost circulation). When fluid is losing into formation, mud level in well bore will be decreased that will result in reducing hydrostatic pressure. For the worst case scenario, you will lose the primary well control and wellbore influx or kick will enter into wellbore.

Typically, slightly overbalance of hydrostatic pressure over reservoir pressure is normally desired. You must keep in mind about the basic of maintaining primary well control that you must maintain hole with drilling fluid that will be heavy enough to overbalance formation pressure but not fracture formations.

Reference book: Well Control Books

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4 Responses to What is Primary Well Control?

  1. Pingback: What is Secondary Well Control?‎

  2. Ehis Oribhabor says:

    Like to know if there is a training or course available wireline operations from your end.
    Thanks
    Ehis

  3. Gokul sharma says:

    Well control is most important of drilling session whatever we use the instrument which is used for drilling but starting of any problem our first focus must be primary well controll

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