Abstract: A method and apparatus for establishing the rate at which fluid is transferred between an offshore well 16 and the formations 20 surrounding the well 16 in the course of drilling the well 16 from a floating drilling rig 14. A drilling fluid handling system 31 is used to inject drilling fluid into the well 16. A marine riser 22 extending from the sea bottom 18 to the rig 14 is provided to return the drilling fluid to the rig 14. The riser 22 is provided with a slip joint 26 to accommodate wave induced heave of the rig 14. Inflow and outflow flowmeters 42,44 are provided to monitor the rates at which drilling fluid is injected into the well 16 and returned to the rig 14. The return flow rate signal is filtered to mitigate the cyclical variations resulting from extension and contraction of the slip joint 26. A signal processing system 46 is provided to maintain the time constant applied in the filtering process at an optimum level as the rate and magnitude of rig heave varies with time.

Abstract: A method and apparatus for establishing the rate at which fluid is transferred between a borehole 14 and the surrounding formations 16 in the course of moving drill string 20 upward or downward in the borehole 14. A bell nipple 40 is situated at the upper portion of the borehole 14. While tripping, drilling fluid is circulated into the borehole 14 and exits through an outflow port 44 in the bell nipple 40. The level of drilling fluid is maintained constant at the outflow port 44. Meters 52, 52', 54 are provided to measure inflow and outflow rates. Circuitry 66 is provided to establish the volume rate at which the amount of drill string 20 within the borehole 14 changes. The outputs of the meters 52, 52', 54 and rate establishing means 66 are summed to establish the compensated rate at which fluid is transferred between the formations 16 and the borehole 14. This compensated rate is compared to an alarm limit. An alarm 76 is activated if the compensated rate exceeds the alarm limit.