Managing well leakage risks at a geologic carbon storage site with many wells

Sealing of fractures in a representative CO2 reservoir caprock by migration of fines

“…As previously discussed, faults, fractures in caprock, and leaking wells have been identified as potential leakage pathways for the safe and secure storage of CO 2 injected in reservoirs because they could serve as conduits for CO 2 and/or brine to migrate from the storage reservoir into overlying aquifers. However, the probability of leakage from well designed and properly regulated carbon storage reservoirs is expected to be quite low 2,31–34 . Although the overall risk of failure through these scenarios is considered to be low, quantitative assessment of these risks is generally not available because historic data for these failure scenarios is not available 13 .…”

Squeeze cementing of micro-annuli: A visco-plastic invasion flow

“…Microannuli and their role in well leakage has become of interest recently not only for GHG emission concerns, but also as part of the design process for potential leakage of CO 2 in carbon capture and storage (CCS) operations. Thus, from the CCS direction there are a number of simple models that assign an effective permeability to a well, to represent the microannulus leakage [3][4][5]. In well decommissioning on the other hand, the microannulus is generally assigned a thickness and interpreted as a uniform narrow gap.…”

A quantitative risk assessment approach for developing contingency plans at a geologic carbon storage site

“…15 While momentum is growing for CCS in the United States and internationally, public and technical concerns about risks associated with GCS-potential unwanted fluid migration and induced seismicity-remain. [16][17][18][19][20][21] CO 2 that escapes the target reservoir through a leakage pathway (e.g., a legacy well or fault) can degrade water quality if it migrates into a freshwater aquifer, become a hazard if emitted in significant quantities at the surface, and reduce the value of the project if the gas enters the atmosphere. [22][23][24][25][26] Pressure buildup in response to CO 2 injection can also push brine upward through leakage pathways, potentially degrading the quality of freshwater resources.…”

“…[7][8][9] Integrated system modeling approaches link sophisticated models of each process at the site (such as storage reservoir dynamics, leakage pathway behavior, and groundwater aquifer impact from leakage) to provide credible forecasts of system behavior that can be used to make key decisions during the development and operation of a GCS site. [52][53][54][55][56] These modeling approaches have been used to evaluate leakage risks, 19,23,[57][58][59][60][61][62][63] inform and optimize both leakage monitoring networks and the duration of postinjection site care, 23,[64][65][66][67][68] assess the long-term probability of successful CO 2 containment, 69 and determine the AoR for a project. 57,70,71 System-based risk assessment modeling can also aid in the development of contingency plans for a GCS operation by quantitatively predicting the impact of various response actions considered on leakage risks amidst uncertainty, but such modeling has not yet been applied in this context.…”