Image analysis – Applications – Seismic or geological sample measuring
Reexamination Certificate
1997-11-17
2001-05-01
Au, Amelia (Department: 2623)
Image analysis
Applications
Seismic or geological sample measuring
C216S056000, C216S059000, C216S065000
Reexamination Certificate
active
06226390
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for modeling the pore-size distribution of a porous sample of variable porosity allowing achievement of laboratory studies on the behavior of the medium modeled in relation to fluids.
2. Description of the Prior Art
A porous medium is made up of a solid structure (or matrix) comprising cavities or pores connected with each other by channels or which are isolated from each other. The pores can be empty or saturated with one or more fluids. There can be for example porous rocks such as sandstones or limestones containing fluids in the pores, notably hydrocarbons. These reservoir rocks can be defined with precision from specific physical quantities such as the porosity, the permeability, i.e. the aptitude for allowing circulation of fluids which they are saturated with, the wettability, the geometry and the connectivity of the pores, etc.
The porous rocks that are found in oil-bearing reservoirs notably have a heterogeneous structure with alternation of zones exhibiting a greater or lesser porosity and permeability. Heterogeneities appear in the form of strata or nodules on the reservoir scale. On the microscopic scale, the porous media exhibit a fractal structure which is translated into a continuous pore-size distribution.
U.S Pat. No. 4,882,763 describes a process for constructing a model representative of a porous medium consisting mainly in etching onto glass a network of pores whose configuration reproduces that of the pores of a porous rock. Transposition is achieved by forming a digitized image of the network of pores by projection of light through a thin section of rock, that is reproduced on the glass substrate by means of a photolithographic process with chemical attack.
The minimum diameter of the channels realizable with a photolithographic process with chemical attack is of the order of 0.15 mm, which limits the variety of channel sizes available. Furthermore, the depth of the channels is not very regular over the total width thereof and it is limited in practice to 0.2 mm. In practice, the width of the channels thus realized is greater than their depth. Consequently, when liquid is injected into the network, the capillary pressure is imposed by the thickness of the channels and not by the width thereof, as it would be desirable for the physical model to be really representative.
SUMMARY OF THE INVENTION
The process according to the invention has applications for modeling porous rocks taken from hydrocarbon reservoirs. Such a physical model allows laboratory observation of the hydrodynamic behavior of oil in the pores and determination of the most suitable method for displacing oil when it is trapped therein. A reservoir engineer can thus choose the best reservoir drive method.
The invention models the pore-size distribution of a porous sample of variable porosity by means of intersecting channels forming a network whose intersections constitute pores, the size of these channels representing physical properties of the medium and being selected from one or more discrete channel size distributions. The method models the porous medium on several different parting surfaces comprising each a network of channels, and the various networks of channels are interconnected so as to form a 3D geometric model.
At least two separated channel size distributions can for example be selected, one corresponding to micropores and being assigned to modeling of zones of lower porosity, the second being assigned to modeling of zones of higher porosity.
According to an embodiment, the geometric model modeling the sample in depth is translated into a physical model comprising several networks of channels communicating with each other, this physical model being made for example by means of a controlled laser from a predesigned 3D geometric model in order to form, on several different layers of a material reacting to the action of the laser light, networks of channels having the porosity of the sample on a parting surface and to form connections between the networks of the various layers.
Channels whose depth can be greater than their width are for example formed, which allows a greater or lesser flow rate to be obtained.
The invention also relates to a system for modeling the pore-size distribution of a porous sample of variable porosity, which is characterized in that it comprises modeling the porosity of the porous medium by means of several networks of intersecting channels whose nodes form pores, the size of these channels representing physical properties of the medium and being selected from at least one discrete channel size distribution, and an etching set for forming a 3D physical model by formation of the network on various layers of a substrate and by formation of communication channels between the networks.
The modeling may be preformed by a computer programmed to manage files representative of the networks of channels to be formed and to produce CAD files for controlling selected etching that may be a controlled laser.
REFERENCES:
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patent: 4821164 (1989-04-01), Swanson
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patent: 5146086 (1992-09-01), De et al.
patent: 5354414 (1994-10-01), Feygin
patent: 5698772 (1997-12-01), Deruyter et al.
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Deruyter Christian
Garnier Dominique
Le Romancer Jean-François
Antonelli Terry Stout & Kraus LLP
Au Amelia
Dastouri Mehrdad
Institute Francais du Petrole
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