Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Interface
Reexamination Certificate
1999-08-31
2001-08-14
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Interface
C073S061440, C073S064560
Reexamination Certificate
active
06272906
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phase separator intended to separate and to measure the volume of the various phases of a mixture of fluids.
2. Description of the Prior Art
Knowledge that can be acquired of various petrophysical parameters of rocks during drainage or imbibition phases can for example be used to select the fluid having the highest ability to displace the petroleum hydrocarbons they contain and therefore to improve the efficiency of enhanced oil recovery processes in a reservoir. It is well-known to determine for example the saturation and the wettability of rocks with respect to fluids such as the water (generally in form of brine), the oil and possibly a gas phase that can be contained therein. Rock drainage operations are therefore carried out, i.e. displacement of the fluids in order to decrease the water saturation, followed by imbibition phases conversely intended to increase its water saturation (Sw). The capillary pressure can thus be measured at a point of a porous sample in the presence of water and oil in a continuous phase, which is defined as the difference Pc at equilibrium between pressure P(oil) and the pressure P(water) of the water. Devices allowing measurement of petrophysical parameters of rocks are described for example in French Patents 2,603,040, 2,708,742 or 2,724,460 filed by the Assignee.
BACKGROUND—OF THE INVENTION
French Patent 2,728,346 filed by the Assignee describes a separator which separates and measures the volumes of constituents of a mixture of a first liquid and of a second liquid, comprising a vessel initially filled with the first liquid and placed on an electronic balance. The mixture is collected in the vessel, the first liquid in excess flowing out. Progressive accumulation of the second fluid in the separator causes variation in the total mass. A programmed processor permanently calculates the saturation values of the sample with respect to the first and second fluid, from the measured mass variations of the separator (9).
U.S. Pat. No. 5,698,791 filed by the Assignee describes a separator used with a multiphase mixture, suited to measure, after decantation in a vessel, the volumes of the various constituents of a multiphase mixture contained in a vessel, essentially by comparing, by means of two relative or differential pressure detectors, the pressures generated by three columns of fluid of equal height, one being entirely filled with at least one of the fluids (a liquid phase for example, topped by a gas phase), the second with at least two of the fluids (two liquid phases for example, topped by the same gas phase), and a third one containing a gas.
It is well-known to detect the position of the interface between an electricity-conducting fluid and another fluid by measuring the capacitance variations of a capacitor comprising generally a central metal rod coated with a fine insulating layer, arranged in line with a vessel containing the mixture. The variation in the inter-electrode capacity between the sheathed rod and the conducting fluid, resulting from the level variation, is measured.
In practice, the accuracy of this type of electric measurement is affected for several reasons: a) the surface area of the electrodes is small because the rod is thin, b) it is difficult to cover a metal rod with a uniform and thin insulating layer, and c) the materials used to form this thin insulating sheath are generally microporous, so that in the case of a liquid-gas separator, the dielectric constant can vary notably according to whether the sheath is more or less saturated with the liquid.
SUMMARY OF THE INVENTION
The device according to the invention separates the phases of a multiphase mixture and measures (by means of interface monitoring) the respective volumes of the phases by electric type measurements in a very wide pressure and temperature variation range, while avoiding notably the aforementioned drawbacks.
The separator according to the invention is generally suitable for measuring the volume of the constituents of mixtures of fluids in all sorts of vessels intended for storage of liquid and/or multiphase products or substances: tanks and vessels used for storage or transport of hydrocarbons, columns, enclosures or other vessels used in chemical engineering, etc. It is more particularly advantageous for measuring volumes in enclosures where high temperatures and pressures are maintained. This is notably the case within the scope of continuous study of physical characteristics of porous material samples and notably of geologic samples taken from formations containing or likely to contain hydrocarbons, where the pressure and temperature conditions prevailing in the underground zones are reproduced in the laboratory.
The separation and measuring device according to the invention comprises at least one unit for separating an electrically-conductive first fluid (e.g. a liquid such as water) and a second fluid whose specific mass is different from that of the first fluid (e.g. oil or a gas), and for capacitive measurement of the position of the interface between the two phases.
The invention comprises an elongate tubular vessel for the fluids, whose outer wall is made of a conducting material and whose inner wall is made of a dielectric material, this vessel being arranged vertically in operation, a conducting element in contact with the conducting first fluid, a capacitance measuring unit electrically connected respectively to the outer wall of the vessel and to the conducting first fluid, that is suited to measure the capacitance, variations between the outer wall and the first conducting fluid on either side of inner wall (
2
), resulting from the variation in the interface level between the first fluid and the second fluid, and fluid supply device connected to the vessel.
According to a first embodiment, the outer wall of the vessel is that of a metal tube and the inner wall is that of a tube of constant thickness placed inside the metal tube.
According to a second embodiment, the outer wall of the vessel is that of a metal tube and the inner wall is that of an insulating coating covering the inner face of the metal tube.
The conducting element in contact with the conducting fluid is for example a wall of a baseplate on which the tubular vessel rests.
According to an embodiment of the invention, the separation and measuring device comprises in combination a second unit for separating a non-conducting liquid phase and a gas phase, and for measuring the position of the interface between these two phases, comprising a second elongate tubular vessel made of a conducting material for the two phases, this second vessel being arranged vertically in operation, an elongate electrode placed substantially in line with the second vessel and electrically insulated therefrom, and electric conductors connecting respectively the second vessel and the electrode to the measuring device.
The second separation unit can be superposed on the first separation unit, either by means of a connecting piece suited to electrically insulate the first and the second tubular vessel, the supply device being connected to the two separation units, or by means of a connecting piece suited to electrically insulate the first and the second tubular vessel and to communicate the inner volumes of the two vessels, the supply device delivering a mixture comprising a conducting first liquid, a second liquid of lower specific mass and a gas, and being connected to the connecting piece.
The device according to the invention is particularly well-suited for precise measurement in enclosures where high temperatures and pressures prevail.
The invention comprises a particularly sensitive and accurate liquid separation unit, the surface area of the electrodes being the relatively large surface of an insulating tube (or coating) on the periphery of the vessel containing the liquids. Making such an insulating tube (or coating) is also easier because, the surface area of the electrodes being relatively large, a gr
Fernandes Gérard
Fleury Marc
Samouillet Aurélie
Antonelli Terry Stout & Kraus LLP
Institut Francais du Pe'trole
Wiggins David J.
Williams Hezron
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