Riser pipe inserts
US4086971A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 15, 1976 |
| Grant date | May 2, 1978 |
| Priority date | — |
| Expiry date | Sep 15, 1996 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B17/01
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
The riser pipe, e.g., 21 inches in diameter, extends from the ship to an anchored wellhead assembly on the ocean floor. A drill bit and drill string are guided down through the inside of the riser pipe and the anchored wellhead assembly to perform drilling operations in the ocean floor. Various strings of casing for lining the borehole wall, which is thus drilled, are run down through the interior of the riser pipe. The first string of casing run is of relatively large diameter, e.g., 20 inches in diameter followed by 133/8 or 103/4 strings. Intermediate strings are typically 95/8 or 75/8, depending on the previous string diameters. As heavier drilling muds are used, the riser tension needed to prevent buckling is increased. To reduce the tension required, we place a sleeve of low density in the annulus between the drill string and the riser pipe interior wall, leaving a much smaller annulus between the drill pipe and the insert, thus displacing the heavier mud with a lighter weight insert.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.