| dc.description.abstract | In this thesis, a sensitivity analysis of dynamic CO2 storage capacity is made against some reservoir parameters by using the Black Oil model (BOM) in Petrel. In this context, dynamic signifies that CO2 storage capacity varies over time as a function of the interplay between fluid low, pressure evolution and changes in reservoir geological properties. Anticline geological structure was considered as a saline aquifer. Water phase was considered brine and gas phase as CO2. The parameters studied have taken care of both permeabilities, porosity, the ratio of vertical-to-horizontal permeability, injection rates. Further studies were carried out to ascertain the impact of geological shapes on dynamic CO2 storage capacity by constructing six different geological grid structures namely anticline, circular (radial), rectangular structure with no dip angle, 10 degrees dip, 25 degrees dip and 40 degrees dip rectangular structures. An optimum CO2 sequestration scheme in saline aquifers, a key strategy process to offset greenhouse gas emissions is dependent on understanding these impacts.
It was under this premise that we conducted a suite of numerical simulations that subjected the before-mentioned parameters to modifications, to evaluate the impact on CO2 storage capacity. The results also indicate higher porosity increases the storage capacity, this is an intuitive result, because more pore space can provide a larger storage capacity of CO2. Likewise, with higher permeability comes a larger storage capacity but for different reasons. The higher permeability makes the reservoirs easier to be penetrated by CO2 and then occupy more pore spaces. This effect is more evident in the pattern of plume distribution and time for the plume to reach the spill point. The vertical to horizontal permeability ratio, impacts the timing of CO2 plume migration to the spill point rather than the overall storage capacity and plume migration pattern. This highlights the important of considering reservoir, porosity, permeability and fluid properties such as density as they determine CO2 spatial distribution and trapping mechanisms. The results obtained from the evaluation of various injection rates suggested that higher injection rates will result to higher CO2 storage capacity and a quicker time for the plume to extend to the spill point.
On the evaluation of different geologic shapes on the storage capacity, the outcome suggest that dip structures can be more efficient when the spill point is located downdip. Higher dip structures did not experience spill point throughout the injection period because the plume is structurally stored updip, rectangular structure with no dip indicated a good storage potential, followed by the radial geometry. The anticline structure surprisingly indicated the list storage capacity and shortest time to spill point when compared to other structural shapes.
We finally evaluated how porosity and injection rates impact on the reservoir pressure, since we observed that porosity and injection rates have greater impact on the dynamic storage capacity. The outcomes outline that higher porosity can buffer over pressurisation because of the more space available for storage, while injection rate needs to be moderated considering other reservoir parameter to avoid inducing seismic.
Overall, the work done in this thesis reinforces that correct characterization and selection of parameters is essential for a successful CO2 storage operation at saline aquifers. This requires good quantification of things like reservoir porosity, permeability, vertical to horizontal permeability ratio, and injection rates. These parameters have a large impact on storage capacity, plume migration paths and the efficiency of seal mechanisms. The priority for future research should be developing dynamic models that simulates how porosity and permeability is changing over time due to the chemical reactions between CO2, brine and rock minerals. This will help with forecasting long-term storage capacity and stability. | |
