Following the 2015 Paris Agreement, many countries are switching from fossil fuel to a more renewable energy supply. However, the CO$_2$ concentration in the atmosphere keeps increasing which makes difficult to accelerate the transition to a net-zero emission. In 2020, a new record of CO$_2$ concentration at 412.5 ppm was achieved, the highest concentration seen in the last 800,000 years. For this reason, several technologies have been in the focus to help reducing the amount of CO$_2$ in the atmosphere as well as keeping it from increasing.

One effective technique in the mitigation of these emissions is called Carbon Capture and Storage (CCS). It is not a new technology, in fact, it has been used in the Oil \& Gas industry since the early 1970s for the purpose of Enhanced Oil Recovery (EOR). In very general terms, when CO$_2$ is mixed with petroleum in the subsurface, its viscosity decreases making it easier to extract more oil. In addition, some of the CO$_2$ gets trapped in the rock which introduced the idea to use the mechanism to reduce CO$_2$ concentrations in the atmosphere.

However, this technique is not absent of risks and it is one of the main drawbacks experienced with activities that involved the subsurface, the surrounding uncertainties are too great sometimes. Some of the risks that could be encountered when producing, injecting or drilling a well in the subsurface are: under or over pressurization, leakage, uplift or subsidence, induced seismicity, and fault reactivation. In order to reduce the mentioned risks, geomechanical studies help with the understanding of the rock behavior and their response to applied stresses.

In this thesis, UCS and Triaxial laboratory experiments were carried out to test the geomechanical behavior of different rocks coming from Norway, Denmark and Germany. For the triaxial tests, five different cycles at different and increasing $P_c$ were performed. Doing so, some main insights were obtained: the modulus of elasticity increases with depth and confining pressure more significantly with $P_c$ lower than 30 MPa, and plateauing at higher $P_c$; the Young's modulus decreases with increasing porosity and increases with increasing cohesion; the P and S waves velocities change when the yield point is surpassed; with low porosity and high cohesion the acoustic velocities are not dependent on the $P_c$, and vice versa; the SYM and DYM follow similar trends; and the elastic modulus is negatively dependent on the Poisson's ratio.

The information and data obtained from this geomechanical study will be of use to model predictions involving CCS projects to avoid reaching the risks factors mentioned. An example of the lack of knowledge and understanding about rock behavior could be the induced seismicity caused by the extraction of gas from the Groningen gas field. These seismic events acted as a turning point, sparking a necessary shift in perspective and paving the way for a more informed and balanced perception of activities involving the use of the subsurface.