Device and method of determining rate of penetration and rate of rotation

1. A method of determining a rate of penetration and/or rate of rotation of a drilling assembly or logging tool while drilling or logging a wellbore, the method comprising the steps of:

at a first time instant, acquiring and storing a first logging data frame using a first array of sensors, and

at a second time instant, acquiring and storing a second logging data frame using a second array of sensors,

wherein the second logging data frame overlaps at least partially the first logging data frame, and

wherein the method further comprises the steps of:

comparing the first and second logging data frames,

determining a relative change in depth and/or azimuth between the first and second logging data frames,

calculating the rate of penetration and/or rate of rotation based on the relative change in depth and/or azimuth determined and a difference between the first and second time instants,

wherein the logging data relate to at least one property of a zone surrounding the wellbore.

2. A method according to claim 1 , wherein the first and second sensor arrays are the same sensor array.

3. A method according to claim 1 , wherein the method further comprises the steps of:

correlating the rate of penetration and/or rate of rotation calculated to a time correspondent measurement of a depth and/or azimuth of the drilling assembly or logging tool made by a measuring device at the earth's surface, and

correcting the measurement of the depth and/or azimuth of the drilling assembly or logging tool made by the measuring device at the earth's surface.

4. A method according to claim 1 , wherein the method further comprises the steps of:

calculating an actual depth and/or azimuth of the drilling assembly or logging tool based on the relative change in depth and/or azimuth determined, and

correcting a time correspondent measurement of a depth and/or azimuth of the drilling assembly or logging tool made by a measuring device at the earth's surface using the actual depth and/or azimuth calculated.

5. A method according to claim 1 , wherein the step of comparing the first and second logging data frames includes determining an overlapping area between the first and second logging data frames.

6. A method according to claim 5 , wherein the step of determining the overlapping area includes evaluating the coherence of the first and second logging data frames by applying a correlation method on both logging data frames.

7. A method according to claim 5 , wherein the step of determining the overlapping area includes evaluating the similarity of the first and second logging data frames by applying a semblance method on both logging data frames.

8. A method according to claim 1 , wherein the logging data comprise mechanical, electromagnetic, nuclear, acoustic, or ultrasonic measurements.

9. A method according to claim 1 , wherein the first and second logging data frames comprise 1D images or 2D images.

10. The method according to claim 1 , wherein the method is carried out by a non-transitory computer readable medium containing computer instructions stored therein for causing a computer processor to perform a program for a rate of penetration and/or rate of rotation determining device arranged to be deployed into a wellbore, the program comprising a set of instructions that, when loaded into a program memory of the rate of penetration and/or rate of rotation determining device, causes the rate of penetration and/or rate of rotation determining device to carry out the steps of the method of determining a rate of penetration and/or rate of rotation of a drilling assembly or logging tool while drilling or logging the wellbore.

11. A device for determining a rate of penetration and/or rate of rotation of a drilling assembly or logging tool while drilling or logging a wellbore, the device being coupled to at least a sensor array for measuring logging data related to at least one property of a zone surrounding the wellbore, and comprising a memory buffer and at least one processing module, wherein the processing module of the rate of penetration and/or rate of rotation determining device is arranged to:

at respective first and second time instant, acquire and store into the memory buffer a first logging data frame using a first array of sensors and a second logging data frame using a second array of sensors, the logging data relating to at least one property of a zone surrounding the wellbore, the second logging data frame overlapping at least partially the first logging data frame,

compare the first and second logging data frames,

determine a relative change in depth and/or azimuth between the first and second logging data frames, and

calculate the rate of penetration and/or rate of rotation based on the relative change in depth and/or azimuth determined and a difference between the first and second time instants.

12. A device according to claim 11 , wherein the first and second sensor arrays are the same sensor array.

13. A device according to claim 11 , wherein the first and second sensor arrays comprise a 1D sensor array or a 2D sensor array.

14. A device according to claim 11 , wherein the processing module of the rate of penetration and/or rate of rotation determining device is further arranged to:

correlate the rate of penetration and/or rate of rotation calculated to a time correspondent measurement of a depth and/or azimuth of the drilling assembly or logging tool made by a measuring device at the earth's surface, and

correct the measurement of the depth and/or azimuth of the drilling assembly or logging tool made by the measuring device at the earth's surface.

15. A device according to claim 11 , wherein the processing module of the rate of penetration and/or rate of rotation determining device is further arranged to:

calculate an actual depth and/or azimuth of the drilling assembly or logging tool based on the relative change in depth and/or azimuth determined, and

correct a time correspondent measurement of a depth and/or azimuth of the drilling assembly or logging tool made by a measuring device at the earth's surface using the actual depth and/or azimuth calculated.

16. A device according to claim 11 , wherein the device is part of one of a drilling assembly and a logging tool.