In this study, we first determined the mineralogy of shale-oil core samples from the Eagle Ford field and then investigated the swelling properties and Cation Ex-change Capacity (CEC) of the core samples in the laboratory. Experiments have been conducted with the samples partially submerged in distilled water, potassi-um-chloride (KCl) brine and Oil-Based Mud (OBM). Several experiments have been performed using strain gages to measure lateral, axial, and diagonal swelling in both submerged and non-submerged areas. To simulate actual well conditions a High Pressure, High Temperature (HPHT) core holder was used to apply different axial and radial confining stress-es, equivalent formation pore pressure, and drilling fluid wellbore pressure. The experiments were conducted under elevated temperatures to better mimic real drilling operations. Saturated shale oil core samples from the Eagle Ford field were tested under various temperatures including reservoir temperature. I also performed Unconfined Compressive Strength (UCS) tests were performed to in-vestigate the effect of temperature on the compressive strength of the core sam-ples. The experimental setup was modified to accommodate