Apparatus and method for measuring differential pressure while drilling
US4805449A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 1, 1987 |
| Grant date | Feb 21, 1989 |
| Priority date | — |
| Expiry date | Dec 1, 2007 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B47/06
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
An apparatus and method for measuring differential pressure of mud internal a drill string and mud in a borehole annulus is disclosed. The apparatus typically comprises: a drill collar having a pressure balancing piston in hydraulic contact with the borehole annulus mud; a shaped cylinder in contact with the mud internal the drill string and supported by the drill collar but attached such that axial forces on the drill collar are not transferred to the shaped cylinder, wherein the shaped cylinder has relatively thicker end portions in contact with the drill collar, and a relatively thinner middle portion such that a gap is formed between the relatively thinner middle portion of the shaped cylinder and the drill collar; a fluid filling the gap and in hydraulic contact with the pressure balancing piston; a plurality of strain gauges axially and circumferentially disposed around the relatively thinner middle portion of the shaped cylinder, wherein the axially disposed strain gauges provide an indication of axial stress and the circumferentially disposed strain gauges provide an indication of hoop stress; and method for obtaining at least one axial and hoop stress measurement from the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.