This thesis develops a geological ensemble-reduction workflow for efficient uncertainty quantification (UQ) in Carbon Capture and Storage (CCS). Using early-time full-physics (FP) injection-rate data and distance-based clustering, representative models are selected to preserve ensemble percentile bounds (P10–P50-P90) within ≤5% relative RMSE. Applied to two 108-member ensembles, injection-rate uncertainty distributions were accurately reconstructed using only 6 and 9 representative models (∼7–10% of the total simulation cost). Early FP rates (≤10 days) proved strongly predictive of long-term behavior and key geological controls. Distance-based generalized sensitivity analysis (dGSA) effectively identified influential parameters governing reservoir response variability at only ~1.3% of the full simulation cost. The approach provides a transparent, low-cost framework for CCS reservoir UQ, enabling robust risk and performance assessment with order-of-magnitude computational savings.

This thesis explores whether vertical stratigraphic cross flow from the A zone to the C1 zone of the Upper Slochteren Member can occur without wellbore crossflow, and under what conditions such recharge is plausible. The study focuses on the B-well in the L-field, Dutch offshore North Sea, where production resumed after a shut-in period, and pressure behavior suggested possible recharge. Four different basecase models were constructed using Rapid Reservoir Modeling (RRM), each representing a different degree of vertical connectivity across the B zone. These models were then transferred to Computer Modeling Group (CMG) software, where dynamic multiphase simulations were performed to assess gas flow between the zones of the Upper Slochteren Member.
The results show that stratigraphic recharge from A to C1 is possible, but highly sensitive to the inter- nal architecture of the B zone. Increased vertical connectivity across the B zone consistently show earlier pressure communication and higher gas fluxes into the C1 zone. Sensitivity analyses were conducted on porosity, vertical permeability, and gas relative permeability to test their influence on flow behavior. These parameters affected not only the rate of gas migration, but also the degree of pressure redistribution across the model, which influences the gas rates even further. Capillary pressure and water saturation were also found to control gas mobility, particularly in low-permeability or heterolithic intervals. The findings do not fully support the hypothesis that stratigraphic recharge explains the observed pressure response in the reservoir, but suggest it may account for part of it. Additionally, the results emphasize the importance of considering vertical heterogeneity and capillary forces when evaluating near-wellbore connectivity.

Revealing an optimal geothermal development strategy attempt with long-term sustainability (upcoming 100 years) based on a real 3D model derived from seismic data is considered one of the main contributions of this research study. The heat extraction and thermal recharge of the reservoir must be in balance to extend the productive lifetime of the Koekoekspolder field system. Based on the best results obtained among different unconventional thermal development approaches, the best locations for the new production wells or extra geothermal doublets as well as the timing, injection temperatures, and rate at which the doublets operate are determined. The best strategy to develop the Koekoekspolder field can be achieved by several steps such as understanding the reservoir properties such as the sedimentary facies, porosity, and permeability distribution by analyzing the literature studies and the static model that simulates the Slochteren formation using Petrel software based on the seismic and log data available followed by a dynamic model that mimics the flow of the hot aquifer inside the reservoir using Eclipse 300 software. Both static and dynamic models must be calibrated by the accessible production data to decrease inaccuracy. The thermal boundaries that are taken into consideration for the koekoekspolder field are not mere confining layers. The workflow of this research study ensures a high degree of realism in terms of the input data and output information of the thermal model of the Koekoekspolder field. The best locations for the new production wells or extra geothermal doublets are determined based on the best simulation results obtained from this research study which fulfill the future energy demand increment. The procedures used in this research study give clear guidance on how the Koekoekspolder field or any other geothermal field can be sustainably developed using a robust history-matched model that has reliable predictions. The low-enthalpy deep geothermal system of the koekoekspolder field is optimized and developed using different types and scenarios of operational strategies for doublets which allow adequate periods for operational thermal recharge. This study takes into consideration different thermal parameters that are not common to achieve enhanced predictions. Moreover, it illustrates the importance and benefits of considering reservoir boundary conditions. Finding suitable sustainable geothermal field development for the Koekoekspolder field can be achieved by new well-studied techniques that can ensure adequate thermal recharge periods. The results of this research study show that the energy demand can be fulfilled with low investment costs to increase the profit of the field owner. Long-term (around 1 century) sustainable development of geothermal fields such as Koekoekspolder and the new technology in this research study can partially contribute to achieving the geothermal master plan objectives in the Netherlands as well as enhancing low and high-enthalpy geothermal field development worldwide.