Fluid measuring devices play an important role in the casing design of a well, because the maximum anticipated influx volume is one of the parameters used to calculate maximum safe drilling and casing setting depths.
The following measuring devices are available:
- trip tank, trip tank chart recorder, or trip sheet;
- pit level indicator/chart recorder with alarm, mud volume totalisers;
- flowline sensors or differential flow meters with alarms where practicable;
- pump stroke counters;
- an active mud tank (suction tank) with a partition which isolates a section with dimensions such that a small mud gain or loss is readily identified, e.g. a 1 m3 (6 bbl) volume change is indicated by a level change of 10 cm (4").
Under certain conditions it may be desirable to assign a crew member to the sole task of properly measuring and monitoring the mud volume.
Mud logging units also enhance the accuracy of measuring and monitoring mud flow and volumes, though steps must be taken to ensure that personnel manning such units are fully briefed and are familiar with primary control techniques.
The fluid measuring system should be able to detect a maximum influx volume of 1 m3 (6 bbl) and alarms should be set and kick drills exercised to ensure that this volume will not be exceeded