Method and apparatus for measuring the bubble point of oil in an underground formation
AssigneeSchlumberger Technology Corporation
InventorsBernard J. P. Glotin, Jacques P. Exbraynt
Life of this patent
Estimating the term…
Abstract
The invention relates to measuring the bubble point of oil down a well drilled into an underground formation. The pressure is measured by an apparatus lowered down the well. The apparatus comprises a chamber (2) in which a small quantity of oil is confined in a volume which is variable by a needle (3) having portions of different diameters (3a, 3b) capable of being inserted to a greater or lesser extent into the chamber (2) under drive from a motor (7). Values of pressure inside the chamber and of chamber volume are respectively measured by a manometer (11) and by a displacement sensor (12) connected to the needle (3) and are transmitted to the surface.
Claims9
A method of measuring the bubble point of oil in an underground formation into which a well has been drilled, the method comprising the steps of:
- lowering a tool down the well, said tool including a chamber whose volume is variable on command;
- opening the chamber so that it fills with oil;
- closing the chamber and causing its volume to vary while measuring the pressure P inside the chamber for each value of volume V imposed thereon, said variation of the volume being initially a reduction so as to make the pressure in the chamber greater than the ambient pressure of the well, and said reduction being followed by gradual increases;
- establishing the curve P=f(V) from the measurement points obtained in this way;
- and
- deducing the bubble point from said curve.
Apparatus for measuring the bubble point of oil in an underground formation into which a well has been drilled, said apparatus being constituted by a tool designed to be lowered down the well and comprising:
- a rigid-walled chamber having at least one orifice through said wall;
- a needle insertable through at least said one orifice to vary the volume of said chamber;
- drive means for driving said needle in longitudinal translation;
- a manometer for measuring the pressure P inside said chamber;
- and
- a displacement sensor coupled to said needle;
- said chamber being capable of being opened for filling with oil and said manometer and said displacement sensor delivering signals enabling the bubble point of said oil to be determined.
Dependencies are inferred from the claim text.