MEDIUM CURVATURE DIRECTIONAL DRILLING METHOD AND SYSTEM

摘要

Medium curvature deviated wellbores having a radius of curvature in the range of 200 feet to 400 feet are drilled with downhole drilling assemblies for drilling the curved wellbore portion and for correcting or holding the horizontal wellbore portion and which are connected to the end of a drillstem made up of elongated elastically bendable drillstem members which may be cyclically compressively stressed during rotation of the drillstem. The elastically bendable drillstem members are characterized by joint forming portions at opposite ends of an elongated tubular body and which are of a diameter which minimizes the tendency for the drillstem to buckle during drilling. Spaced apart stress bearing sleeves are attached to or integrally formed with the tubular body and are of a diameter greater than the body and preferably equal to the diameter of the tool joint portions. The drillstem is made up of the elastically bendable compressive service drillstem members extending through the curved and horizontal portions of the wellbore and heavy walled drill pipe or drill collars are provided in the drillstem in the vertical hole portion to impose compressive loads on the drillstem through the curved portion of the wellbore.