Schlumberger Technology Corporation

Anthony K Booer

David C Hoyle

Albert H Wignall

Jeffrey B Aron

Bertrand P Peltier

Emmanuel Detournay

A tool for measuring the mechanical properties of a formation through which a borehole has been drilled, comprising a tool body capable of being lowered into a borehole, the tool body having pads mounted on movable arms, each pad carrying a PDC type cutter which is urged against wall of the borehole so as to cut into the formation; transducers are provided for determining the depth of cut made by the cutter and for determining the resistance of the rock to cutting. The tool is connected to a wireline, enabling the cutter to be moved through the formation and the data from the transducers to be returned to the surface for analysing the depth of cut and resistance to cutting to determine the mechanical properties of the rock.

Formation evaluation tool

The invention relates to a method of monitoring the drilling of a borehole through an earth formation with a rotating drill bit fixed at the lower end of a drillstring. At least one physical quantity associated with the vibrations resulting from the interaction of the rotating drill bit with the earth formation is detected and an oscillatory signal is generated in response thereto. Filter coefficients a.sub.k of an auto-regressive filter model are determined by fitting the filter output signal with the oscillatory signal. The reflection coefficients of the vibrations propagating along the drill string and being reflected by a mis-match of impedance of two successive elements of the system earth formation/drillstring are derived from the filter coefficients. Finally, the hardness of the formation being drilled, the contact of the drillstring with the borehole and the vibration level of the vibration along the drillstring are determined from the reflection coefficients.

Method of monitoring the drilling of a borehole

A monopole transmitter for a sonic well tool includes an axial tube, a piezoceramic cylinder surrounding the axial tube, an endcap disposed at each end of and firmly contacting the cylinder, and an apparatus for holding the endcaps firmly against the axial tube. The endcaps firmly contact the axial tube without simultaneously contacting an upper bulkhead. The apparatus may include spring washers disposed between the bulkhead and at least one endcap, or it may include a spring disposed between a nodal mount and each endcap. A nodal mounting tube may be disposed around the axial tube, a ring being disposed at each end of the nodal mounting tube, each ring being disposed outside of the cylinder, the apparatus including a spring disposed between each ring and an endcap outside of the cylinder for biasing the endcaps in tension against a ring thereby holding each endcap firmly in contact against the axial tube.

Growing community of inventors

Cambridge, United Kingdom

Anthony K Booer