Integrity of wellbores and near wellbore processes are crucial issues in geological carbon storage (GCS) projects as they both define the confinement and injectivity of CO₂. For the proper confinement of CO₂, any flow of CO₂ along the wellbore trajectory must be prevented using engineered barriers. The effect of cyclic stimuli on wellbore integrity, especially in the context of GCS projects, has been given less attention. In this study, the effect of pressure- and temperature-cycling on two types of wellbore composites (i.e., casing-cement and cement-caprock) have been investigated experimentally in small- and large-scale laboratory setups. The experiments have been carried out by measuring the effective permeability of the composites under pressure and thermal cyclic conditions. Furthermore, the permeability of individual samples (API class G and HMR+ cement and caprock) was measured and compared to the permeability of the composites. The results indicate that the permeability of API class G cement when exposed to CO₂ is in the order of 10⁻²⁰ m² (10⁻⁵ mD) as a result of the chemical reaction between the cement and CO₂. In addition, the tightness of the composite cement–rock has been confirmed, while the permeability of the composite casing–cement falls within the acceptable range for tight cement and the CO₂ flow was identified to occur through or close to the interface casing–cement. Results from thermal cycling within the range −9 to 14 °C revealed no significant effect on the integrity of the bond casing–cement. In contrast, pressure cycling experiments showed that the effective pressure has a larger influence on the permeability. The potential creation of micro-cracks under pressure variations may require some time for complete closing. In conclusion, the pressure and temperature cycling from this study did not violate the integrity of the casing–cement composite sample as the permeability remained low and within the acceptable range for wellbore cement.

This article summarizes the state-of-the-art knowledge gained from field observations and laboratory studies regarding foam as a liquid controlling agent in porous media. Being the least explored property of foam, its effect and potential have often been overlooked or simply ignored. The aim with this review is therefore to demonstrate the abilities that foam could have to block, reduce, delay, suppress, or divert water flow in porous media. As a liquid controlling agent in porous media, foam has potential for industrial processes that involve fluid injections or fluid withdrawals in porous geological formations, such as improved/enhanced oil recovery (IOR/EOR), matrix-stimulation treatments, underground storage of CO₂, hydrogen, compressed-air or natural gas withdrawal, geothermal energy, and contaminated soil-groundwater remediation processes with unwanted aquifer impacts. Improving the water utilization factor and water management in these applications might result in tremendous energic, economic, and environmental incentives that are worth pursuing. Specific focus in this review is given to the post-foam water injection, which determines the ultimate stability and water-blocking capabilities of the foam treatment. Main parameters and mechanisms that can influence foam stability against water injection/intrusion after generation and placement are assessed and discussed. Unresolved issues are highlighted, which give recommendations for further research and field-scale operations.

An increasing number of oil and gas companies reach their economic limit after years of production, exhausting the support of natural-pressure drive mechanisms in the reservoir and the benefits of water or gas injection