Abstract: A method is disclosed for producing hydrocarbon fluids through a well having a well casing string with a casing section which is surrounded by an annular space which comprises a sensor assembly for measuring electromagnetic and/or other physical properties of solid and fluid materials within the annular space, in an underground formation surrounding the annular space and/or within the interior of the section of the casing string, wherein the sensor assembly is mounted on a body of swellable material, such as a swellable rubber or other elastomeric material, which is secured to the outer surface of said casing section and presses the sensor assembly against the inner surface of the surrounding underground formation after the casing string has been lowered into the wellbore.

Abstract: A method of drilling a stable borehole in a formation containing a stress field having a direction of maximal stress, whereby the borehole is drilled with an elongated non-circular cross sectional contour along an axis of elongation and whereby a directional component of the axis of elongation is kept oriented substantially parallel to the direction of maximal stress.

Abstract: A method is provided for the reduction of inflow of rock particles from an earth formation into a wellbore for the production of hydrocarbon fluid. The method comprises creating a zone of reduced compressive stiffness around the wellbore by removing rock material from the wall of the wellbore.