Geological storage is an effective approach capable of reducing greenhouse gases
emissions at significant scales by storing the CO2 underground. Subsurface reservoirs
with sealing caprocks can provide long-term containment for the injected CO2. However,
the leakage is a major concern in most storage sites. The presence of abandoned
wells penetrating the reservoir caprock may cause leakage flow paths for CO2 to the
overburden. To access the leakage in the subsurface, an analytical model for the
time-varying leaky well is needed. In this thesis, we propose a new semi-analytical
approach based on pressure-transient analysis to model the behavior of leakage and
corresponding pressure distribution in multiple wells multiple layers system. Current
solutions either take approximations on essential operations or requires numerical
inversion for the solution in the Laplace domain. In this work, we employ the superposition
in time and space to solve the diffusivity equation in 2D radial flow to
approximate the transient pressure in the reservoirs. We use numerical simulations to
verify the proposed time-dependent semi-analytical solution. The results show good
agreement in both pressure and leakage rates. Sensitivity analysis is conducted to
assess different CO2 leakage scenarios to the overburden. The equivalent injection
rate is also proposed to release the single-phase assumption so that the solution can
recover identical results as two-phase numerical simulation in the far-field.
| Date of Award | Jul 2021 |
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| Original language | English (US) |
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| Awarding Institution | - Physical Sciences and Engineering
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| Supervisor | Hussein Hoteit (Supervisor) |
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