The effect of CO₂ sequestration on oll well cements

Depleted oil- and gas-bearing formations represent likely locations for the disposal of CO2. Oil-and gas-bearing formations have proved capable of trapping fluids over geologic times. Because of the removal of hydrocarbons from these formations via wells, a potential avenue for leakage has been created. Cements are used in the construction (primary cement) and abandonment (plug cement) of oil and gas wells. Because wells represent a potential leakage pathway, it is important to study the effects of sequestration on the integrity of materials used to make them. Experiments are conducted to examine the effects of CO₂ sequestration conditions on cements used to construct and abandon oil and gas wells. The experimental conditions consist of two influent pH 2.4 and 3.7, and two temperatures, 23° and 50°C, are considered likely for potential sequestration formations. The results show that significant damage, including complete loss of the calcium hydroxide phase, can take place over a time span as short as seven days.