Drilling system and method

1. A method of operating a drilling system, the method comprising:

suspending a tubular drill string from a travelling assembly into an opening on a drill floor, the travelling assembly comprising a part of a hoisting system;

operating a sensor to measure and to provide a first signal, the first signal representing an acceleration or a velocity of the tubular drill string in a direction into or a direction out of the opening;

providing a second signal, the second signal representing an operational parameter of the hoisting system, the operational parameter being indicative of a vertical speed or of a vertical acceleration of the travelling assembly;

comparing the first signal with the second signal, and

reducing an operating speed of the hoisting system if the discrepancy between the first signal and the second signal exceeds a first pre-defined threshold.

2. The method as recited in claim 1 , wherein the operational parameter is at least one of,

an acceleration or a speed of a hoisting system component which is directly or indirectly connected to the tubular drill string,

an electric power, a hydraulic power or a mechanical power supplied to the hoisting system component, or

a force acting on the hoisting system component from the tubular drill string.

3. The method as recited in claim 2 , wherein the hoisting system component is the travelling assembly, a wire forming part of the hoisting system, a winch forming part of the hoisting system, or a hoisting cylinder forming part of the hoisting system.

4. The method as recited in claim 1 , wherein the second signal is,

an operational input signal to the hoisting system, or

a measurement of the operational parameter taken at the hoisting system.

5. The method as recited in claim 1 , further comprising:

operating an automatic controller to determine a third signal, the third signal being a function of the first signal and the second signal and being indicative of a discrepancy between the first signal and the second signal.

6. The method as recited in claim 5 , further comprising:

outputting the third signal to an operator.

7. The method as recited in claim 5 , further comprising:

providing a warning signal to an operator if the discrepancy exceeds a second pre-defined threshold.

8. The method as recited in claim 5 , further comprising:

closing a set of slips to prevent the tubular drill string from travelling into the opening if the discrepancy exceeds a third pre-defined threshold.

9. The method as recited in claim 8 , wherein the step of closing the set of slips is executed automatically by the automatic controller.

10. The method as recited in claim 1 , wherein the step of reducing the operating speed of the hoisting system is executed automatically by the automatic controller on the hoisting system.

11. The method as recited in claim 1 , wherein the sensor is an optical sensor, an ultrasonic sensor, a radar, a magnetic sensor or a machine vision sensor.

12. A drilling system comprising:

a hoisting system comprising a travelling assembly, the travelling assembly being configured to suspend a tubular drill string into an opening on a drill floor;

a sensor configured to measure and to provide a first signal; and

an automatic controller which is configured to perform the method as recited in claim 1 .

13. The drilling system as recited in claim 12 , wherein the sensor is an optical sensor, an ultrasonic sensor, a radar, a magnetic sensor or a machine vision sensor.