Shell Oil Comapny

Robijn Feenstra

Anthony W Kamp

Bruce H Walker

The invention relates to a downhole motor having a housing of which the resistance against bending in a predetermined longitudinal plane is smaller than in any other longitudinal plane. Directional drilling of boreholes is carried out by rotating the drill string simultaneously with the rotation of the drill bit driven by the downhole motor over periods preceded and followed by selected periods during which the drill string is not rotated simultaneously with the rotation of the drill bit driven by the downhole motor.

Downhole motor and method for directional drilling of boreholes

The invention relates to a method and means for controlling the course of a bore hole during drilling thereof. The means comprises a down-hole motor and two eccentric stabilizers mounted on the housing of the down-hole motor near the ends thereof. Controlling the course of a bore hole that is being drilled with the down-hole motor driving the drill bit is done by successively not rotating the drill string and rotating the drill string.

Method and means for controlling the course of a bore hole

A jet rotary drill bit confirming a first strainer element allowing the passage of mud carrying small-sized particles, but preventing relatively coarse particles from passing to the jet nozzles. The first strainer element is self-cleaning and the relatively coarse particles are passed on to a second strainer on which they remain trapped.

Rotary bit with jet nozzles

To allow the bit to drill in formations that behave plastically, while also protecting the bit against overloading when entering a relatively soft formation, ridge-shaped elements are provided having the ridges within the rotation alloy symmetric surface defined by the scraping edges of the scraping means (natural or artificial diamonds). The flanks of the elements are positioned at an acute angle to the said surface.

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Rijswijk, Netherlands

Robijn Feenstra