Amoco Corporation

Bp Amoco Corporation

Lawrence Allen Sinor

Tommy M Warren

James F Brett

A method and liner assembly for drilling into unstable or depleted formations is provided that maintains control of the wellbore against caving such as where unconsolidated formations are penetrated and/or minimizes fluid losses such as to underpressured formations where differential pressures exist. The method and liner assembly herein includes the provision of a liner having a portion thereof that is drillable so that after setting of the liner, drilling can continue deeper into the unstable formations with minimal damage to the bit used to drill out the liner drillable portion. In one form, the liner has a shoe that includes cutter mounting blades, each having a set of cutters thereon. Relief slots are formed in the blades between cutters so that as the shoe and its blades are being drilled, the drill bit will cut through the slots, releasing the shoe cutters for transport up to the surface by the drilling fluid thereby minimizing damaging contact of the bit with the shoe cutters. Preferably, the shoe has a bi-center and anti-whirl design. In another form, the liner has preassembled therewith a whipstock and a pre-formed window of drillable material adjacent the whipstock, so that after drilling into the unstable formation with the liner assembly and setting it therein, subsequent drilling beyond the liner occurs by running a drill bit downhole and drilling until it engages the whipstock that guides it to the window for drilling therethrough.

Drilling assembly and method of drilling for unstable and depleted

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.

Anti-whirl underreamer

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. The imbalance force and model are used to calculate the position of an additional cutter or cutters which when mounted on the bit in the calculated position would reduce the imbalance force. A cutter or cutters is then mounted in the position or positions so calculated.

Growing community of inventors

Tulsa, OK, United States of America

Lawrence Allen Sinor