Abstract: A method and apparatus for running a whipstock into a well bore attached to a combination mill and drill bit, releasing the mill/bit from the whipstock, milling a window in the casing, and drilling a lateral well bore, all in one trip. The mill/bit is provided with a primary cutting structure better suited for milling through the casing, and a secondary cutting structure, better suited for drilling through the earth formation. The secondary cutting structure is initially smaller in diameter than the primary cutting structure. The whipstock can be attached to the mill/bit with a shear bolt supported by a boss on the whipstock, with the boss designed to arrest axial motion of the mill/bit after shearing of the bolt.

Abstract: An anti-whirl underreamer comprising a body configured for connection to a drillstring, at least two arms carried by the body which are extendable between a retracted position and a projected position, a movable piston and biased spring assembly for moving the arms, a plurality of cutting elements carried by one of the arms for cutting an axially extending cylindrical sidewall of the borehole within a subterranean formation and for applying a resultant radial force to the body as it rotates, and a low friction bearing region carried by another arm for transmitting the resultant radial force from the body to the sidewall of the borehole during rotation of the underreamer within the borehole. The cutting elements are positioned so that the resultant radial force developed is of sufficient magnitude and direction to substantially maintain the low friction bearing region in contact with the sidewall of the borehole as the underreamer is rotated within the borehole.

Abstract: A method for modeling and building drill bits. An array of spatial coordinates representative of selected surface points on a drill bit body and on cutters mounted thereon is created. The array is used to calculate the position of each cutting surface relative to the longitudinal axis of the bit body. A vertical reference plane which contains the longitudinal axis of the bit body is established. Coordinates defining each cutter surface are rotated about the longitudinal axis of the bit body and projected onto the reference plane thereby defining a projected cutting surface profile. In manufacturing a drill bit, a preselected number of cutters are mounted on the bit body. A model of the geometry of the bit body is generated as above described. Thereafter, the imbalance force which would occur in the bit body under defined drilling parameters is calculated.