Project Info

IMURF – Evaluation of Capillary Condensation in Synthesized Porous Materials with Finely-Tuned Pore Sizes

Xiaolong Yin | xyin@mines.edu
Brian Trewyn | btrewyn@mines.edu

In many unconventional natural gas reservoirs, gas is stored in a tight, nanoporous matrix with complex pore geometry and mineralogy. The amount of gas stored in the nanopores is a strong function of gas-surface interactions. Adsorption increases density of gas near mineral surfaces, and therefore it serves as a mechanism to increase gas storage. As layers of adsorbed molecules grow with increasing pressure, the density of gas may become liquid-like in the entire pore. This phenomenon, termed as capillary condensation, increases the storage capacity of gas even more. It also creates problems, however, because condensed gas as a wetting liquid can effectively block nanopores and reduce flow.

It has been gradually recognized that in a tight porous medium capillary condensation as a thermodynamic phase transition should follow the sequence of pore size distribution, from small pores to large pores, owning to the shift in the vapor-liquid equilibrium in pores of different sizes due to capillary pressure. We plan to carry out gravimetric measurements of condensation-induced mass changes to detect capillary condensation, using an oscillation-based gravimetric apparatus that we recently developed and tested. This apparatus consists of a weight holder suspended by a spring, submerged in a gas environment that can be pressurized and heated. The weight holder with porous sample is triggered to oscillate at its natural frequency. The frequency of oscillation and the damping of oscillation, detected through a solenoid, are used to calculate the weight of porous sample. This device can sense mass change to the level of 0.1% and has been successfully applied to detect condensation of propane gas in crushed Niobrara shale samples. Instead of using real rock samples, in this study we will employ mesoporous silicate nanomaterials (MSN) with well-defined pore sizes as measured by nitrogen sorption analysis and TEM, so that measured capillary condensation data can be compared to molecular simulations and serve to verify predictions of thermodynamic equilibrium model. As opposed to a natural tight rock, the exact size and surface of MSN are available to reduce the uncertainties in the model parameters associated with natural samples. We plan to test ethane, propane, and mixtures of ethane and propane.

This research endeavor requires converged expertise in the synthesis and characterization of porous materials (Trewyn) and in the using of a simple, yet novel, system to measure mass changes in high-pressure environments (Yin) to be successful. On the topic of thermodynamic fluid-solid interactions, petroleum and chemistry disciplines have natural synergies. We will use both chemistry and petroleum undergraduate students to carry out the proposed research activities to achieve the targeted understanding of behavior of gases in nanopores. We expect that this work could lead to other joint research directions / opportunities, for instance, capture of CO2 in nanoporous materials and sequestration of it in geological nanoporous medium.

We plan to enroll one chemistry undergraduate student and one petroleum engineering undergraduate student for this project. The two students will work with each other and with Trewyn and Yin’s respective research groups. Regular meetings (every two weeks) will be held to share information, converge research efforts, and provide learning environment / opportunities to the students.

For more information:
Krishnan K. Using Oscillations to Detect Capillary Condensation in MCM-41. MS thesis, Colorado School of Mines, 2019.
Larson Z, Cho Y, Yin X. Experimental technique to measure mass under high pressure conditions using oscillatory motions of a spring-mass system. Meas. Sci. Technol. 28, 065902, 2017.

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