Balanced or underbalanced drilling method and apparatus
US5865261A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 3, 1997 |
| Grant date | Feb 2, 1999 |
| Priority date | — |
| Expiry date | Mar 3, 2017 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B21/085
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A casing or tubing segment or segments are disclosed which can be used to create a parasite annulus during drilling. The cased wellbore receives a string containing valves and the drillstring operates through it. As the mud circulates, the segments of the tubing or casing provide communication at various depths from the parasite annulus (i.e., the outermost annulus) into the circulating mud, which is the innermost annulus. Each valve is adjustable to alter the amount of differential pressure required in order to open it. The valves are also in hydraulic pressure balance so that only the pressure added by the injected gas acts to open them. The valves close by a spring bias.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.