Schlumberger Technology Corporation

Harry James Cook

Kjell Haugvaldstad

Jonathan Dunlop

A drill bit includes cutting elements and a displacement sensor deployed on a drill bit body. The displacement sensor includes an engagement piston disposed to translate axially in a sensor housing. The engagement piston includes an inner plunger and an opposing outer engagement element configured to engage a subterranean formation and is biased outward from the sensor housing. The displacement sensor further includes a position sensor configured to sense an axial position of the engagement piston in the sensor housing. An electronic controller is configured to determine a measured displacement from the sensed axial position of the engagement piston. The displacement sensor may enable depth of cut and rate of penetration measurements to be made while drilling.

At-bit depth of cut and rate of penetration measurements

Methods and systems are provided that calculate data representing an estimate of formation strength while drilling. The methods and systems employ a drill bit that is instrumented with a first sensor and a second sensor. A processor is configured to i) determine and store first data representing cutting forces acting on a cutting element of the drill bit while drilling based on measurements of the first sensor while drilling, ii) determine and store second data representing depth of cut of the drill bit while drilling based on measurements of the second sensor while drilling, and iii) process the first data and second data to generate and store data representing contact stress against the formation while drilling. This resultant data can be used as an estimate of formation strength. This estimate of formation strength is similar to UCS and can be used in oilfield operations/planning, such as formation characterization while drilling, or drilling efficiency analysis while drilling.

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Cambridge, United Kingdom

Harry James Cook