STRESS AT BOREHOLE DURING CARBON INJECTION

This study aims to analyze the character of temperature of CO2 along borehole in regards with different injection rate. It is to identify whether injection rate plays a role in determining the temperature changes along borehole. Secondly, the effect of temperature on breakdown pressure is studied. The temperature difference between CO2 and surrounding will induce an amount of thermal stress along the borehole. The temperature difference of surrounding and CO2 also plays an important role in the enthalpy of CO2 along wellbore, hence, it will affect the pressure of CO2 along wellbore. Finally, this study is concluded with a suggestion for safe range of injection rate.
Unlike a producing well, CO2 injection well has more constraint. The injection pressure must not exceed the fracture pressure formation along wellbore to ensure the integrity of the wellbore. Temperature difference of CO2 and surrounding might induced a lower breakdown pressure along the wellbore.
The scope of this study is stress along the wellbore. The wellbore is the connection of CO2 from surface to the subsurface storage. Hence, the integrity of the wellbore is the one of the keys to ensure a safe injection program.
For this report, the methodologies are purely theoretical. Mathematical equations of CO2 characteristic along wellbore is adapted from Luo and Bryant (2010). Next is the breakdown pressure identification. In order to identify pressure of CO2 along wellbore, Span and Wagner (1994) Equation of State was used.
The result of this report helps to identify a safe environment and condition for CO2 injection.