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This study assesses the potential of supercritical CO2 injection for the recovery of heavy oil in the Niger Delta Z-field, characterized by high viscosity crude with an API gravity of 18.6 API. Given the challenges posed by the viscosity of the reservoir fluid, conventional primary and secondary production schemes were deemed impractical. As a solution, hot supercritical CO2, was chosen as an enhanced oil recovery (EOR) method due to its miscibility properties with oil and the environmental benefit of reducing atmospheric CO2 concentrations. In the EOR process, supercritical CO2 with a viscosity of 0.095 cP was injected at a pressure of 3500 psia and a temperature of 200°F, above the Minimum Miscibility Pressure (MMP) to ensure miscibility with the reservoir fluids and mobilization of residual oil. The CO2 was heated at the surface and injected as hot CO2 to achieve viscosity reduction by heating up the reservoir fluid. The injected CO2, meeting the reservoir oil at miscible conditions, reduces the interfacial tension between the oil and the injected CO2, leading to oil phase swelling. The study employed a compositional simulator for the simulation of CO2 flooding, comparing two cases: natural depletion and supercritical (hot) CO2 injection. The simulation results after 5000 days of recovery indicate a recovery efficiency of 3.3% for the natural depletion case. In contrast, the supercritical CO2 EOR case demonstrates a remarkable recovery efficiency of 73%. Additionally, the analysis of gas recovery shows no significant difference between the two cases. These results show that natural depletion is not feasible for heavy oil recovery due to the low energy (dissolved gas) present in the oil at reservoir conditions and the inhibiting high viscous forces of the reservoir fluid that impede flow to the surface. In contrast, the deployment of hot CO2 injection emerges as a highly promising and substantial prospect for the recovery of heavy oil in the Z-field. The study suggests that this process should be considered for application in the recovery of other non-conventional heavy oil fields in the Niger Delta, particularly those that are not extractable through primary and secondary drive mechanisms. The success of hot CO2 injection, with its ability to reduce viscosity, achieve miscibility, and enhance recovery efficiency, positions it as a viable and environmentally beneficial EOR strategy for heavy oil reservoirs. [ABSTRACT FROM AUTHOR]

This study focuses on the modelling wellbore compartmentalization techniques for downhole flow control in both homogeneous and heterogeneous oil reservoirs. The objective was to achieve fluid inflow equalization to address variable productivity effects (VPE) in heterogeneous multilayered reservoirs and to ensure flow uniformity across horizontal intervals in homogeneous reservoirs, mitigating the heel-to-toe effect (THE) caused by frictional pressure drop in horizontal well completions. The compartmentalization along the wellbore was achieved using swellable packers, ensuring each well compartment had uniform productivity before equalization. Inflow equalization across compartments was accomplished using inflow control devices (ICDs). Analytical models for ICDs were developed based on fundamental fluid flow equations, including Darcy's and Bernoulli's equations. Simulation of the developed model was conducted using MATLAB 2014Rb. Three simulation cases were explored: Case 1 studied variable pressure effects in homogeneous reservoirs where pressure and permeability influenced inflow inequality; Case 2 examined variable pressure effects considering pressure, permeability, and skin as factors for inflow variation; Case 3 simulated inflow equalization in horizontal homogeneous reservoirs to counteract the heel-to-toe effects. The results demonstrated successful equalization in all cases: Case 1 achieved a target well production rate of 7500 stb/d; Case 2 resulted in a total target well inflow rate of 6250 stb/d; Case 3 achieved a composite well inflow rate of 15000 stb/d. Implementation of variable ICDs in the horizontal well segment prevented early water/gas breakthrough due to THE, enhancing well longevity and recovery efficiency, thereby improving total well recovery. [ABSTRACT FROM AUTHOR]

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