Schlumberger Technology Corporation

Michel Valdois

Raymond J Besson

Pierre Maitre

Jean-Jacques Boy

Luc Petitjean

A pressure sensor of the present invention can perform pressure measurements under very severe mechanical and thermal conditions. It comprises a cell carrying a strain-measuring circuit. The cell is placed inside a body and is put into contact with the pressure to be measured. The cell has a hermetically sealed internal chamber inside which pressure is set to a predetermined reference value. The outside surface of the cell is subjected to the pressure to be measured. The cell is constituted by two half-shells joined together according to a join plane. The cell is preferably made of sapphire, with the crystal axis of the sapphire being perpendicular to the join plane so as to obtain isotropic stresses. A strain-gauge circuit is deposited on a plane surface of one of the half-shells, parallel to the join plane. The sensor is particularly suitable for testing oil deposits.

Pressure sensor useable in oil wells

In a piezoelectric transducer (10) an external element (12) of tubular form receives a pressure, notably a pressure to be measured, on its external face (16). It is cut in a quartz crystal in one piece with a plate (25) capable of vibrating under the action of an electric stress and extending in a plane parallel to the longitudinal direction of the tubular element inside the latter. Each of the longitudinal edges of the plate is connected by a transverse connecting element (30, 31) to the internal face (14) of the tubular element so as to transmit forces (F1 and F2) resulting from the application of the external pressure to the plate (25) in a direction substantially parallel to its plane and perpendicular to the axis of the tubular element (12).

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Cachan, France

Michel Valdois