Drilling assembly and method of drilling for unstable and depleted formations
US5957225A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 31, 1997 |
| Grant date | Sep 28, 1999 |
| Priority date | — |
| Expiry date | Jul 31, 2017 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B10/64
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
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 th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.