**1. Introduction**

Since last decade, there has been a growing concern of the negative impacts of global climate change. In the last century, scientists believe that carbon dioxide (CO2) emission is has been the main component responsible for approximately three-quarters of global greenhouse gas emission. A roadmap developed to combat climate change has outlined 10 scalable solutions clustered into categories of social transformative, governance improvement, market and regulation-based solutions, technological innovation and transformation, and lastly natural and ecosystem management. While some proposed mitigation techniques focus on reduction of CO2 emission, Carbon Capture, Utilization and Storage (CCUS) technology can aim at achieving lower CO2 amount in the atmosphere by capturing and storing the anthropogenic gas in a geological storage. Geological storage of CO2 in depleted oil and gas reservoirs, deep saline reservoirs, unmineable coal seams or injected into active oil and gas reservoirs for Enhanced Oil Recovery (EOR) are currently a wellaccepted method of storing CO2. For economic reasons, CO2 is being injected at the highest possible rates through limited number of wells. This could trigger injectivityrelated issues due to complex interactions between CO2, brine and rock initiated in the aquifer. This makes CO2 injectivity not only a technical challenge but also an economic consideration.

This chapter presents a comprehensive discussion on how the various mechanisms contributed by the fluid-rock interactions during CO2 sequestration affect CO2 injectivity. The chapter begins by laying out the theoretical dimensions of CO2 sequestration. This is followed by a brief overview of different CO2 injectivity impairment mechanisms, focusing on the two main themes: salt precipitation and fines migration. The experimental findings from previous researchers have also been discussed and some findings remarks made. The insights gained from this study may be valuable to the rapidly expanding field of carbon sequestration.
