APPARATUS AND METHOD FOR DRILLING A BRANCH BOREHOLE FROM AN OIL WELL

摘要

A wireline drill train is used to drill an elongated, small diameter, latera l branch borehole from near the base of a main well. The drill train, includes a drill module, a first self-propelled thrust module coupled to the drill module, and a second self- propelled thrust module pivotally coupled to the first self-propelled thrust module. Each thrust module includes at least two extendible thrusters. Each extendible thruster include s a six-bar mechanism and a traction tread. The drill train further includes a first articulated linkage linking the first self-propelled thrust module to the drill module, and a second articulated linkage linking the second thrust module to the first thrust module. The second articulated linkage includes a thrust-transmission bar and three retractable stiffener bars. The method for drilling the curved transition region of the lateral branch borehole include s executing a series of alternating pivotal drilling steps and forward drilling steps to create a step-cut region of branch borehole having very small radius of curvature.