Patent Number: 6,612,383

Title: Method and apparatus for milling well casing and drilling formation

Abstract: A dual function drag bit is used in a method for both milling well casing or liner and subsequently drilling rock formation without the sequential removal of a milling assembly and replacement with a drilling assembly. The method employs a cutting tool that is capable of both milling steel pipe casing in a well bore and subsequently drilling rock formation outside the well bore after passing through the casing. In one embodiment an insert embedded into the surface of the cutting tool comprises at least an outer layer, such as cemented tungsten carbide, capable of milling steel casing, and at least a second layer, such as polycrystalline diamond, capable of drilling formation, the two layers being bonded together and to a carbide substrate. In another embodiment, inserts with a polycrystalline diamond cutting face for drilling rock formation are in parallel with cemented tungsten carbide cutters for milling steel casing.

Inventors: Desai; Praful C. (Kingwood, TX), Dewey; Charles H. (Houston, TX)

Assignee: Smith International, Inc.

International Classification: E21B 29/00 (20060101); E21B 29/06 (20060101); E21B 10/46 (20060101); E21B 10/56 (20060101); E21B 10/54 (20060101); E21B 029/06 ()

Expiration Date: 09/02/2020