Patent ID: 7044237
Filing Date: 2006-05-16
Classification: E21B

Abstract:
1. System for operating a well that is being drilled 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 system comprises: a) a pressure containment device to the wellbore which keeps the wellbore closed at all times while it is being drilled; b) means for measuring at least one of mass flow, volumetric flow, mass flow rate and volumetric flow rate on the inlet and outlet streams and generating flow signals, wherein monitoring means are located on lines in and out and are operated continuously throughout a given operation; c) at least one pressure sensor to obtain pressure signals, wherein the at least one pressure monitoring sensor is located at the wellhead or at the bottomhole and is operated continuously throughout a given operation; d) a central data acquisition and control system provided with software for predicting a real time signal; e) means for injecting drilling fluid through an injection line through which said fluid is made to contact said flowmeans, and said pressure sensor, and recovering drilling fluid through a return line; f) means for collecting drill cuttings at the surface; g) means for collecting flow signals; h) means for collecting pressure signals; i) means for directing all the collected signals to the said central data acquisition and control system; the software of the central data acquisition and control system considering, at each time, a real time predicted signal; the system further comprising j) 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 k) means to send a command from the central data acquisition and control system to the pressure or flow control device designed to adjust the volumetric or mass flow rate in the return line or pressure inside the wellbore; and the central data acquisition and control unit being programmed to compare said real time predicted signal to the signal; wherein the system acts 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, wherein the software on identifying the influx or loss event, automatically sends a command to the pressure or flow control device designed to adjust the return flow rate or pressure inside the wellbore so as to restore the said signal to the predicted signal, thereby preemptively adjusting backpressure to immediately control the event without interruption of the drilling operation and wherein the system is a closed loop system, whereby monitoring means continuously provide date to the central data acquisition and control system whereby a predicted signal is continuously revised in response to any adjustment of actual signal value, adjusting ECD wherein the system further comprises a means for controlling equivalent circulating density which is defined as hydrostatic pressure plus friction losses occurring while circulating fluid converted to equivalent mud density at the bottom of the well, and continuously or intermittently drilling a gas, oil or geothermal well wherein drilling is carried out using bottom hole pressure chosen from one of the group comprising of: being a value intermediate the pore pressure and the fracture pressure of the well and able to directly determine either or both values if desired; being the exact bottom hole pressure needed, with a direct determination of the pore pressure; or being bottom hole pressure regulated to be just less than the pore pressure (known as underbalanced drilling) thus generating a controlled influx which may be momentary in order to sample the well fluid in controlled manner or may be continuous in order to produce well fluid in controlled manner.