| 摘要 |
The present invention provides a drilling system for directional drilling of boreholes. The system contains a drill string having a drill bit driven by a positive displacement mud motor. Sensors placed at selected locations in the drill string continually measure various downhole operating parameters, including the differential pressure across the mud motor, rotational speed of the mud motor, torque, temperature, pressure differential between the fluid passing through the mud motor and the annulas between the drill string and the borehole, and temperature of the circulating fluid. A downhole control circuit having a microprocessor and nonvolatile memory processes signals from these sensors and transmits the processed data uphole to a surface control unit via a suitable telemetry system. The surface control unit is programmed to operate the drilling system or aid an operator to control the drilling operations in any number of modes in response to the information provided by the various sensors. The system also provides means for monitoring the wear condition of the mud motor and to estimate the remaining life of the mud motor during the drilling operations. The drill string also preferably contains formation evaluation and testing devices, such as a resistivity device for determining the formation resistivity, gamma ray device for determining the gamma ray intensity of the formation, an inclinometer for determining the inclination of the drill string near the drill bit and a device for determining the drill string azimuth. The present invention provides method for controlling the drilling operations that contains the steps of: (a) placing a drill string at the borehole bottom, (b) passing a pressurized fluid through the mud motor rotate the drill bit, (c) measuring differential pressure across the mud motor; and (d) controlling the drilling of the boreholes as a function of the differential pressure.
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