04805449 is referenced by 49 patents and cites 3 patents.

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 plurality of strain gauges, for taking the difference between hoop and axial measurements, and for providing a pressure determination representing the difference of mud pressure.

Title
Apparatus and method for measuring differential pressure while drilling
Application Number
7/126645
Publication Number
4805449
Application Date
December 1, 1987
Publication Date
February 21, 1989
Inventor
Pralay K Das
Sugar Land
TX, US
Agent
Dave Gordon
Stephen L Borst
Assignee
Anadrill
TX, US
IPC
E21B 47/06
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