Reservoir Condition Pore-scale Imaging of Multiple Fluid Phases Using X-ray Microtomography

The goal of this procedure is to non-invasively image multiple fluid phases in the pore space of rock at realistic conditions of temperature and pressure similar to those occurring in subsurface reservoirs and aquifers. This is accomplished by first assembling the core assembly carefully and placing this within a high pressure, high temperature core holder. The second step is to attach the core holder to the high pressure, high temperature control pumps and reactor using flexible peak tubing.

Next, the pressure and temperature in the system erase to that of the representative. Subsurface conditions and fluids are equilibrated and injected into the pore space of the rock. Ultimately, reservoir condition.

Micro CT imaging is used to show both the amount and the distribution of carbon dioxide held in place as a trapped residual phase after brine injection. This method can help answer key questions in the field of multiphase flow in porous media, such as determination of residual saturation for capillary trapping and wearability and contact angle measurements. Although this method can provide insights into super critical CO2 brine rock systems with application to carbon capture and storage, it can also be used for hydrocarbon brine rock systems for studying phenomena related to enhanced oil recovery and international resources.

Visual demonstration of this method is critical as the sample preparation and core assembly steps are difficult to learn. This is because the relationship between the core assembly, the core, the confining sleeve, and the multiple aluminum wraps is complicated. To begin this procedure, test the connections of the equipment carefully for any fluid leaks.

Next place the brine in the base of the reactor. Wrap the flexible heater around the flow cell After that, construct the metal end fittings by removing the thread from the one eighth of an inch end of a one 16th of an inch to a one eighth of an inch reducer fitting. Then cut small grooves into the face of the one eighth of an inch end of the fitting to distribute the injected carbon dioxide over the entire face of the core.

Subsequently, pass the high pressure thermocouple through the metal end parts of the microflow cell seal the thermocouple using the quarter inch ferals and nuts, so the hot junction sits adjacent to the in nut face of the core within the confining annulus of the cell L.Next, drill the desired sample into a core of 6.5 millimeters in diameter and 30 millimeters to 50 millimeters in length. R down the ends of the core flat to ensure a good connection with the metal end pieces. Then wrap this core in aluminum foil.

Subsequently place it within a fluoro polymer elastomer sleeve. After that, connect the ends of the elastomer sleeve to the metal end fittings. Add another wrap of aluminum foil to the exterior of the elastomer sleeve before placing the hot junction of the thermocouple next to the inlet face of the core, and adding a final wrap of aluminum foil.

This forms the core assembly. Now assemble the microflow cell with the core assembly sealed within it. Connect the cell to the stage within the micro CT enclosure using a clamp mounted on top of the rotational CT stage.

In this procedure, close all the valves apart from valve one, two, and three. After that, load carbon dioxide from the cylinder into pump one and the reactor. Then close valve one.

Slowly raise the temperature and pressure of the reactor to that desired for the pore fluid vigorously. Mix the pore fluid for at least 12 hours to ensure all phases are in chemical equilibrium prior to injection. Next, open valve 14, and load the confining fluid into pump three.

Then close it and open valves 12 and 13. Pressurize the confining annulus of the cell to at least 10%higher than the proposed pore fluid pressure. After that, open valve 11.

Load the brine into pump two and close it. Subsequently open valves nine, eight and six. Slowly pressurize the pore space of the rock until it is at the desired pore fluid pressure and fill the pore space of the sample with brine that has not been equilibrated with supercritical carbon dioxide.

Now, open valve four plus more than 1000 poor volumes of equilibrated brine through the core by refilling pump two at a constant flow rate in this procedure past 10 pore volumes of supercritical carbon dioxide through the core at a very low flow rate, ensuring a low capillary number of around 10 to the minus six continuously. Take 2D projections in order to accurately measure the total injected volume while supercritical carbon dioxide is displacing the brine in the pore space. Pass another 10 volumes of equated brine through the core at the same low flow rate resulting in the trapping of supercritical carbon dioxide as a residual phase in the pore space.

After that, take a few scans of the sample to image the drainage or inhibition. Use a voxel size such that the entire diameter of the core fits within the field of view. Then reconstruct the scans using tomographic reconstruction program.

Reconstruct the composite volumes by stitching together multiple overlapping sections that are required sequentially. The image shown here is a 3D rendering of the core after drainage where each non-wetting phase cluster is given a different color. These five images show a 3D rendering of the same core after five separate inhibition experiments, whereas the large range of colors indicates a poorly connected residual phase.

This is a cross section of the core after drainage. The darkest phase is super critical carbon dioxide. The intermediate phase is brine, and the lightest phase is rock grain, and this is a cross section of the core.

After inhibition, the power law scaling of the residual ganglia size distribution is shown here. Once mastered, this technique can be done in around two hours if performed properly. Remember That working with the equipment at high pressure and temperatures can be extremely hazardous, so precautions such as appropriate training and equipment certification must be taken prior to conducting experimental procedure.