The effect of ionic strength of brine (high and low salinity solutions) on rock dissolution and resulted pore structure alterations.

Activity: Examination


1st PhD year report
The increasing in concentration of greenhouse gases (GHG) is accepted as the main cause of global warming and carbon capture and sequestration (CCS) is critical for addressing this challenge. The structure of deep aquifers are known to have the highest potential for storing captured CO2 in place. However, the injection of CO2 in geological formation disturbs the equilibrium among the resident phases and makes uncertainties for secure fate of injected CO2. Although the functionality of some parameters e.g. temperature, partial pressure of CO2, rock mineralogy, wettability and pH are well understood on the rock-fluid interaction, there is not sufficient amount of information available in the literature for investigating the effect of salinity and ion type/valency of formation water. Therefore, the aim of this PhD is to evaluate the effect of ionic strength of brine (high and low salinity solutions) on rock dissolution and resulted pore structure alterations, and to shed lights on possible mechanisms behind these phenomena. In addition, depending on the distance from injected well to the region of interest, resident phases may experience different orders of fluctuation which play an important role in determining the interaction among rock-fluid. In this regard, my experiments are designed for both static (hydrothermal batch) and dynamic (core flood) tests for assessing to what extend the experimental setups can be effective on determining prevailing mechanisms on rock-fluid interplay. This appraisal is conducted by utilizing a non-destructive method, which is micro Computed Tomography (micro CT) imaging while providing the opportunity to study the alteration of pore structure and porosity in submicron scale. Furthermore, Powder X-Ray Diffraction (PXRD) will be conducted to analyse minerals dissolution/precipitation and Environmental Scanning Electron Microscopy (ESEM) in conjugate with Energy Dispersive Spectroscopy (EDS) will be used to obtain information on morphology and elemental distribution on rock surface, respectively. Two different kinds of rock samples which are representative of subsurface formation were selected and prepared for experiments. Initial analysing methods were conducted to characterise the rocks’ properties (e.g. mineralogy, porosity and micro scale pore structure) using various software e.g. Qualx and VGStudio MAX for analysing raw data from Powder X-Ray Diffraction (PXRD) and micro Computed Tomography (micro CT) scanner, respectively.
This is the first study to illustrate the effect of brine in presence of different ionic strengths and dissolved chloride salts of a variety of alkali and earth alkaline cations on reservoir rock dissolution and pore structure changes under realistic conditions. It also opens a door to a better understanding of the key CO2-brine induced rock dissolution drivers.
PeriodMay 2019
Examination held at
Degree of RecognitionInternational