Patent ID: 7367411

Claim:
Method for operating a well that is being drilled from a surface with a drill string to provide a wellbore having a drilling fluid circulated therethrough via inlet and outlet streams wherein the well is kept closed at all times, wherein the method comprises the use of a system comprising: a) a pressure containment device to the wellbore; b) means for measuring at least one of volumetric flow, mass flow, volumetric flow rate and mass flow rate on the inlet and outlet streams and obtaining flow or flow rate signals; c) at least one pressure sensor to obtain pressure signals; d) a central data acquisition and control system provided with software for predicting a real time signal; said method comprising the steps of a′) injecting drilling fluid through an injection line through which said fluid is made to contact at least one of said flow and flow rate means, and said pressure sensor, and recovering drilling fluid through a return line; b′) collecting drill cuttings at the surface; c′) measuring at least one of the volumetric flow and mass flow in and out of the well and collecting flow signals; d′) measuring pressure of fluid and collecting pressure signals; e′) directing all the collected signals to the said central data acquisition and control system; f′) the software of the central data acquisition and control system considering, at each time, a predicted signal; the system further comprising f) a pressure or flow control device on the outlet stream to control the flow out of the well and to keep a back pressure on the well; and wherein the central data acquisition and control unit is programmed to compare a real time predicted signal to the corresponding actual signal; the method further comprising having the actual and predicted signals compared and checked for any discrepancy; wherein the method and system act on the principle of volume or mass conservation, to determine the difference in volume or mass being injected and returned from the well; said determining compensates for factors including increase in hole volume, additional mass of rock returning as an indication of the nature of the fluid event occurring downhole; said comparison yielding any said discrepancy, said software also receiving as input any early detection parameters, wherein the input triggers a chain of investigation of probable scenarios, to ascertain that an influx or loss event has occurred; and converting said discrepancy to a value for adjusting the pressure or flow control device and restoring the predicted signal value, and in case of a discrepancy, having a signal sent by the central data acquisition and control system to adjust the pressure or flow control device and restore the predicted signal without interruption of the drilling operation, thereby preemptively adjusting backpressure to control the event.