Abstract: The present invention relates to a collapsible drill bit for use in formation drilling and a method of formation drilling. The drill bit includes a main body having a first cutting diameter and includes a front end with a cutting face supporting one or more cutting elements and a rear end configured to operatively connect to a drill string. The drill bit also includes a retractable portion between the front end and the rear end, the retractable portion including at least one cutting face supporting one or more cutting elements, the retractable portion configured to move between an expanded position in which the retractable portion has a second cutting diameter and a collapsed position in which the retractable portion has a diameter less than or equal to the first cutting diameter. Wherein the retractable portion is caused to move into the collapsed position upon an application of a sufficient force.

Abstract: In one embodiment, the present invention provides a reverse circulation drilling apparatus which comprises a concentric dual wall drill pipe, having a first threaded end, a second threaded end, an outer pipe and an inner pipe captured in a concentric arrangement within the outer pipe and defining an annulus therebetween. The inner pipe defines an inside passage, which is not in fluid communication with the annulus. A first means for directing an outer flow of fluid through the annulus is provide. A second means for directing an inner flow of fluid through the inside passage is also provided. The first means and the second means prevent fluid communication between the outer flow and the inner flow. The first threaded end and the second threaded end are each suitable to connect the reverse circulation drilling apparatus to another reverse circulation drilling apparatus.