Wettability alteration of sedimentary rocks in presence of organic matter

Date of Award

2024

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Engineering

First Supervisor

Stefan Iglauer

Abstract

Sedimentary rocks have a great value for our society. Fossil fuels, stored in them, significantly boosted humanity development and currently are irreplaceable energy source. Moreover, geological reservoirs are useful even when they are depleted. Modern ideas of geostorage using depleted reservoir are in the current research trend, as society is trying to move from conventional to alternative sources of energy, as well as decarbonize already existing ones. Using reservoirs to store Hydrogen (H2) and Carbon Dioxide (CO2) is considered very promising for improving global climate picture.

In all these scenarios, fluid flow in porous media plays one of the main roles and defines most of the processes taking place inside the reservoir. In itself, fluid flow is partially determined by the properties of pore surface. Thus studying surface properties is a key element in understanding and predicting the behavior of the total system. But despite the importance, there is still relatively low understanding of reservoir rock surface behavior in the presence of organic matter or gases like H2 and CO2. For instance, the influence of wettability, which is defined by the attraction of a liquid phase to solid surface, is often neglected during simulation and production of hydrocarbons. One of the reasons being that common analytical methods for studying geological samples are outdated and lack sufficient accuracy.

Another reason is that surface properties of a reservoir tend to change with time, specifically in the presence of organic matter. Hydrocarbons from crude oil can form an organic film, covering the surface of pores and altering their wettability. While there is a theoretical explanation of the process, the nature and composition of this film has not been studied yet. It has been shown that mixed-wet scenario is extremely common for oil and gas reservoirs, in contrast to initial suggestions that water-wet reservoirs are dominant. Therefore there is an urgent need for more advanced analytical methods.

In this study we discuss the application of atomic force (AFM) and scanning electron microscopies (SEM), as well as second ion mass spectrometry (SIMS) methods to provide more accurate analysis of rock surface properties. We consider methodological aspects of AFM adhesion force measurements regarding sample preparation. We study quartz glass beads aged in different crude oils to imitate wettability alteration. We experimentally confirm theoretical assumption about formation of liquid organic film via layer-by-layer composition analysis using time-of-flight SIMS (ToF-SIMS). We investigate the influence of the origin, and hence composition of crude oil on the formed organic film and properties of modified surface. This research advances current application of above mentioned methods for studying geological samples and thus contributes to improving the research of sedimentary rocks wetting properties.

DOI

10.25958/yf63-7y54

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