Method and apparatus for measuring lithological characteristics of rocks

Claim 3

A method according to claim 1, in which vibrations are detected at at least one pair of points located on said drilling gear, said method further comprising the step of effecting algebraic summation of said generated signals.

Claim 4

A method according to claim 2, in which the vibrations detected at said pair of points are detected by means of two pickup devices arranged at points on two diametrically opposite generatrices of said measuring section.

Claim 5

A method according to claim 3, in which said generated signals are representative of longitudinal vibrations, and in which said diametrically opposite points at which said pickup devices are located are offset relatively to one another along the axis of said drilling gear by a distance which is between 2 centimeters and 9 meters.

Claim 6

A method according to claim 1, in which said selected signal is obtained by selecting signal components in said frequency band by means of a band-pass filter arrangement having a mean frequency which is controlled as a function of the instantaneous speed of rotation of said drilling gear multiplied by the number of attacking elements in at least one set.

Claim 7

A method according to claim 1, in which said measuring section is situated at the upper part of said drilling gear.

Claim 8

A method according to claim 1, in which said measuring section is situated near said tool.

Claim 9

A method according to claim 1, utilizing a tool having a number of cutter wheels, each having inner and outer rows of cutting teeth, in which said generated signals are representative of longitudinal vibrations, and said selected signal is selected in a frequency band centered on a frequency equal to said frequency of rotation of said tool multiplied by the number of said cutter wheels or The number of cutting teeth in said outer row of each of said cutter wheels.

Claim 10

A method according to claim 8, in which said signals representing longitudinal vibrations are generated by means of at least one pair of accelerometers which are offset axially and have electrical axes which are parallel to the axis of said drilling gear.

Claim 11

A method according to claim 8, in which said signals represent longitudinal stresses in said drilling gear and are generated by means of at least one pair of strain gauges disposed parallel to the axis of said drilling gear.

Claim 12

A method according to claim 1, in which said tool is a diamond tool having a plurality of diamond-bearing surfaces and in which said generated signals represent torsional vibrations, said selected signal being selected in a frequency band centered on a frequency which is equal to the frequency of rotation of said tool multiplied by the number of said diamond-bearing surfaces.

Claim 13

A method according to claim 11, in which said generated signals represent torsional accelerations which are detected by means of accelerometers having their electrical axes located in a plane perpendicular to the axis of said drilling gear.

Claim 14

A method according to claim 11, in which said generated signals represent torsional stresses which are detected by means of strain gauges located in a plane which is inclined at 45* to the axis of said drilling gear or of said measuring section.

Claim 15

In combination with drilling gear comprising a drilling tool having at least one set of elements for attacking rock within a drill hole, and means for driving said drilling tool at a selected frequency of rotation, the improved apparatus for measuring rock characteristics during drilling which comprises: vibration responsive means including at least one vibration pickup device positioned to detect vibrations by said tool, said vibration responsive means being adapted to produce at its output an electric signal representative of said vibrations, voltage-limiting means connected to the output of said vibration responsive means for eliminating from said signal voltages outside a predetermined range of values, means connected to the output of said voltage-limiting means for selecting from said signal a frequency band centered on a frequency equal to the frequency of rotation of said tool multiplied by the number of attacking elements in at least one of said sets, and means responsive to the amplitude of said signal in said frequency band for correlating said amplitude with the depth in said drill hole at which said drilling tool is operating.

Claim 16

In combination with drilling gear comprising a drilling tool having at least one set of elements for attacking rock within a drill hole, and means for driving said drilling tool at a selected frequency of rotation, the improved apparatus for measuring rock characteristics during drilling which comprises: vibration responsive means including at least one vibration pickup device positioned to detect vibrations by said tool, said vibration responsive means being adapted to produce at its output an electric signal representative of said vibrations, voltage-limiting means connected to the output of said vibration responsive means for eliminating from said signal voltages outside a predetermined range of values, means connected to the output of said voltage-limiting means for selecting from said signal a frequency band centered on a frequency equal to the frequency of rotation of said tool multiplied by the number of attacking elements in at least one of said sets, and means responsive to the amplitude of said signal in said frequency band for correlating said amplitude with the depth in said drill hole at which said drilling tool is operating.

Claim 17

The combination according to claim 14, comprising at least two vibration pickup devices and means for effecting the algebraic summation of signals delivered by the respective pickup devices so as to supply a single signal to said voltage-limiting means.

Claim 18

The combination according to claim 13, in which said pickup devices are constituted by two accelerometers for picking up longitudinal accelerations, disposed on two opposed generatrices of a connector situated at the lower part of said drilling gear near said tool, said accelerometers being arranged on shoulders perpendicular to the axis of said connector and being rigidly attached to said shoulders.

Claim 19

The combination according to claim 42, in which said pickup devices are constituted by two accelerometers for picking up torsional vibrations, disposed diametrically opposite one another on two generatrices of a connector which is inserted in the drilling gear near said drilling tool, said accelerometers being disposed on shoulders parallel to the axis of said connector and the electrical axes of said accelerometers being parallel and diametrically opposite each other.

Claim 20

The combination according to claim 15, in which said pickup devices are constituted by strain gauges for picking up longitudinal vibrations, disposed on a connector located at the lower part of said drilling gear near said tool, said gaUges being disposed at two diametrically opposite points on the longitudinal surface of said connector and the axes of said gauges being parallel to the axis of said measuring section.

Claim 21

The combination according to claim 15, in which said pickup devices are constituted by strain gauges for picking up torsional vibrations, disposed on a connector located at the lower part of said drilling gear near said tool, said gauges being disposed at two diametrically opposite points on the longitudinal surface of said connector, which lie in a common plane inclined at 45* to the axis of said connector.

Claim 22

The combination according to claim 15, in which said vibration-responsive means is situated at the upper part of said drilling gear.

Claim 23

The combination according to claim 20, in which said driving means comprises rod means and said drilling gear includes a drilling head and a sleeve interposed between said head and said rod means, and said pickup devices are accelerometers for detecting longitudinal vibrations, disposed on two opposite generatrices of said sleeve, on shoulders which are perpendicular to the axis of said sleeve, and offset along said axis, said accelerometers being rigidly connected to said shoulders.

Claim 24

The combination according to claim 20, in which said drive means comprises rod means and said pickup devices comprise two accelerometers responsive to torsional vibrations, disposed on two diametrically opposite generatrices of the lower part of said rod means, said accelerometers being rigidly mounted in a common plane, on shoulders which are parallel to the axis of said rod means and are situated in an axial plane.

Claim 25

The combination according to claim 20, in which said drive means comprises rod means and said drilling gear includes a drilling head and a sleeve interposed between said head and said rod means, and said pickup devices comprise strain gauges responsive to longitudinal vibrations, disposed on two diametrically opposite generatrices of said sleeve at two points slightly offset axially of said sleeve.

Claim 26

The combination according to claim 20, in which said drive means comprises rod means and said pickup devices comprise strain gauges responsive to torsional vibrations, said gauges being disposed at two diametrically opposite points at the lower part of the longitudinal surface of said rod means, in a common plane which is inclined at 45* to the axis of said drilling gear.

Claim 27

The combination according to claim 14, in which said vibration responsive, voltage limiting and frequency band-selecting means are situated at the lower part of said drilling gear, and which comprises means for transmitting to the surface the amplitude of said selected signal.

Claim 28

The combination according to claim 25, in which said means for transmitting the amplitude of said selected signal to the surface comprises rod means through which said drilling tool is driven, together with magnetostrictive means for transmitting along said rod a signal responsive to the amplitude of said selected signal, and a magnetostrictive receiver above the ground for detecting the signal transmitted along said rod and transmitting it to said correlating means.

Claim 29

The combination according to claim 48, in which said means for transmitting the amplitude of said selected signal comprise conduit means for the passage of a stream of mud, a valve controlling the pressure of said stream of mud in said conduit means, and means for operating said valve in dependence upon said selected signal, whereby the pressure of said stream of mud is modulated in accordance with the amplitude of said selected signal.