Posts 10-17 in this series contained 8 examples of underground injection projects. Each of them encountered events that impacted project results. And while some of these events were anticipated, most were not. Building on these experiences, a series of observations can be made.
Understanding the subsurface is fundamental for SCS projects, just as it is for hydrocarbon exploration. We begin with homogeneous and isotropic models, and then refine them to approximate the state of nature. In the absence of dynamic injection data, it is challenging to capture the true heterogeneity of the reservoir and its impact on CO2 plume movement (Sleipner project), especially if natural fractures are involved (In Salah project).
This has implications for how much fluid can be stored without pressuring-up the reservoir (Snøhvit project) or exceeding the fracture gradient and breaching containment (Tordis project). The thickness of permeable reservoir (Kh) is key for achieving injectivity, which can be diminished by operational problems (Gorgon project) or halted by induced seismicity if geomechanical properties are unknown (Castor project).
Once the CO2 is injected, understanding the plume size, geometry, and migration direction becomes critical. Injected fluids may impact offset accumulations (Wilmington and Huntsman projects) and pose significant liability, especially in areas where the pore space is privately owned.
These are not easy hurdles to overcome, and a concerted effort is needed to address them. We’ll summarize some of the techniques we use to address these issues in our next posting.