Microfluidic technique for detection of multi-contact miscibility

A microfluidic system for determining miscibility of a solvent in a sample reservoir fluid, the system comprising:

• a microfluidic apparatus for determining miscibility of a solvent in a reservoir fluid, the apparatus comprising:
• a substrate defining a microchannel extending along a length from an inlet to an outlet, the microchannel having an elongated main channel extending from the inlet to the outlet and having a series of cavities extending outward from the main channel, the cavities spaced from one another along the length of the microchannel, the cavities being in fluid communication with the main elongated channel, wherein the microchannel is configured to receive and fill with a reservoir fluid and the cavities are configured to retain the reservoir fluid when reservoir fluid in the main channel is displaced by the solvent, thereby permitting solvent flowing in the main channel from the inlet to the outlet to serially contact the retained reservoir fluid in each cavity;
• a first fluid introduction device to introduce a sample fluid into the microchannel through the inlet;
• a second fluid introduction device configured to introduce a solvent into the microchannel through the inlet after the sample fluid is introduced into the microchannel;
• a pressure controller configured to control an inlet pressure of solvent flowing through the microchannel at the inlet of the microchannel;
• at least one pressure sensor coupled to the microchannel and configured to measure at least one of an inlet pressure and outlet pressure of solvent flowing in the microchannel;
• an image capture device configured to capture a series of images of at least a portion of the microchannel as a front of the solvent moves through the microchannel from the inlet to the outlet of the microchannel;
• and
• an image processing device configured to process a plurality of the series of images and, based on a comparison of the processed images, determine whether a miscibility condition has been reached.