Apparatus for high speed image capture during measurement of capillary pressure in a porous sample
A measurement device including a centrifuge for holding porous media samples configured to test samples under centrifugal motion during rotation. A fluid capture device adjacent each media sample receives fluid from the sample due to centrifugal motion. A measurement system measures an amount of fluid from the media samples by taking an image of a fluid meniscus in the fluid capture device. A position sensor determines a position of the fluid capture device and triggers a camera to take the image of the fluid meniscus when the fluid meniscus is in a field of view of the camera. To prevent a false image from appearing in the captured image, a shield blocks light from reaching the camera when the meniscus is not in the field of view. The image of the fluid meniscus is processed to determine a fluid volume correlated to capillary pressure of the media sample.
1 . A capillary pressure measurement device, comprising:
a centrifuge comprising a rotating apparatus adapted to hold a plurality of porous media samples and configured to test the porous media samples under centrifugal motion during rotation of the rotating apparatus;
a fluid capture device disposed adjacent to each of the porous media samples during rotation for receiving fluid displaced from the respective porous media samples due to centrifugal motion applied to the respective porous media samples by rotation of the rotating apparatus;
a measurement system that measures an amount of fluid displaced from each of the porous media samples, the measurement system including a light source that illuminates respective fluid capture devices, a camera that takes an image of a fluid meniscus in the respective fluid capture devices, and a position sensor that determines a position of the respective fluid capture devices and triggers the camera to take the image of each fluid meniscus when the fluid meniscus is in a field of view of the camera, wherein each fluid meniscus represents a fluid volume that is correlated to capillary pressure of a corresponding porous media sample; and
a shield configured to block light from the light source from reaching the camera other than when the meniscus is in the field of view of the camera, the shield comprising a slot adjacent to each fluid capture device adapted to expose the camera to the light source when the meniscus is in the field of view of the camera.
2 . The capillary pressure measurement device of claim 1 , wherein the rotating apparatus comprises at least two arms and the shield is attached to the rotating apparatus to rotate with the arms, and wherein the shield comprises slots adjacent to each arm of the rotating apparatus that allow light to pass through and illuminate the fluid meniscus when the fluid meniscus is in the field of view of the camera.
3 . The capillary pressure measurement device of claim 1 , wherein the position sensor detects when the respective fluid capture devices and the slot adjacent the respective fluid capture devices pass over or under the position sensor and triggers the camera to immediately capture the image of the corresponding fluid meniscus.
4 . The capillary pressure measurement device of claim 1 , wherein the position sensor detects an indicia of the rotating apparatus and triggers the camera to capture the image of the fluid meniscus of each fluid capture device at a time thereafter that is a function of a speed of rotation of the rotating apparatus and a distance of the indicia from the fluid meniscus.
5 . The capillary pressure measurement device of claim 1 , wherein at least one fluid capture device includes one or more solid spacers to reduce a volume of the at least one fluid capture device for different porous media sample configurations.
6 . The capillary pressure measurement device of claim 1 , further comprising an image processing device that processes images captured by the camera to determine the fluid volume in the respective fluid capture devices.
7 . The capillary pressure measurement device of claim 6 , wherein the image processing device further calculates capillary pressures of the respective porous media samples as a function of the determined fluid volumes and outputs the respective calculated capillary pressures to a display.
8 . A capillary pressure measurement method, comprising: placing a plurality of porous media samples in a rotating apparatus of a centrifuge, wherein the rotating apparatus is configured to test the respective porous media samples under centrifugal motion during rotation of the rotating apparatus; receiving, in a fluid capture device disposed adjacent to each of the porous media samples during rotation, fluid displaced from each porous media sample due to centrifugal motion applied to the respective porous media samples by rotation of the rotating apparatus;
determining a position of the respective fluid capture devices using a position sensor;
triggering a camera to take an image of a fluid meniscus in the respective fluid capture devices when each fluid meniscus is in a field of view of the camera;
providing light from a light source through slots in a shield adjacent to each fluid capture device to expose the camera to the light source when the meniscus is in the field of view of the camera;
blocking light from the light source that illuminates the respective fluid capture devices from reaching the camera using the shield other than when the meniscus is in the field of view of the camera;
and determining an amount of fluid displaced from each of the porous media samples from the images of each respective fluid meniscus, wherein each respective fluid meniscus represents a fluid volume that is correlated to capillary pressure of the respective porous media samples.
9 . The capillary pressure measurement method of claim 8 , wherein the rotating apparatus comprises at least two arms, further comprising rotating the shield with the arms whereby slots of the shield adjacent to each arm of the rotating apparatus allow light to pass through and illuminate the fluid meniscus when the fluid meniscus is in the field of view of the camera.
10 . The capillary pressure measurement method of claim 8 , wherein determining the position of the respective fluid capture devices comprises the position sensor detecting when the respective fluid capture devices and the slots in the shield adjacent to each fluid capture device pass over or under the position sensor and triggering the camera comprises triggering the camera to immediately capture the image of each fluid meniscus when the respective fluid capture devices and the slots in the shield adjacent to each fluid capture devices pass over or under the position sensor.
11 . The capillary pressure measurement method of claim 8 , wherein determining the position of the respective fluid capture devices comprises the position sensor detecting an indicia of the rotating apparatus and triggering the camera comprises triggering the camera to capture the image of each fluid meniscus at a time after detecting the indicia that is a function of a speed of rotation of the rotating apparatus and a distance of the indicia from the respective fluid meniscus.
12 . The capillary pressure measurement method of claim 8 , wherein determining the amount of fluid displaced from the respective porous media samples from the images of the fluid meniscus comprises processing images captured by the camera to determine the fluid volume in the respective fluid capture devices.
13 . The capillary pressure measurement method of claim 8 , wherein placing the porous media samples in the rotating apparatus comprises simultaneously placing porous media samples of variable sizes and configurations in the rotating apparatus.
14 . The capillary pressure measurement method of claim 13 , wherein simultaneously placing the porous media samples of variable sizes and configurations in the rotating apparatus comprises reducing a volume of a corresponding fluid capture device by adding one or more solid spacers to the corresponding fluid capture device for different porous media sample configurations.
15 . The capillary pressure measurement method of claim 8 , further comprising calculating capillary pressures of each of the porous media samples as a function of determined respective fluid volumes and outputting the respective calculated capillary pressures to a display.