In this study, we introduce the Delft Advanced Research Terra Simulator (DARTS), which employs the Operator-Based Linearization (OBL) approach to provide efficient and precise solutions for non-linear discretized equations, to simulate the polymer flooding process. This compositional simulation framework is feasible for describing complex physical phenomenon with high nonlinearity because detached functional operators have been developed to release the calculation load while maintaining a high degree of stability and accuracy. The main contributions and innovations are shown below: i. A two-phase and three-component chemical flooding mathematical model with some reasonable assumptions was developed to investigate the enhanced-oil-recovery (EOR) mechanism of polymer flooding. A finite volume discretization scheme and a fully implicit method (FIM) are implemented to approximate the conservation equations. The OBL approach is used to reduce the complexity of the simulation framework. The correctness of the model is verified by comparison with analytical model. ii. In addition to shear thinning effect, polymer viscoelasticity has also been taken into account. This mathematical model is able to handle high shear rates during field displacement as well as low to medium shear rates in laboratory experiments. iii. A new model for porosity reduction caused by polymer adsorption is formulated. The effect of polymer concentration on the effective pore volume is incorporated in numerical simulations based on Langmuir adsorption model.

In the energy transition from fossil fuels to less polluting renewable energy sources geothermal energy are considered as a promising technology. Gasses such as CO2 are often dissolved in geothermal waters. With the extraction of these fluids from the reservoir, a change in pressure will occur towards the extraction well which may cause dissolved gas to exsolve. The exsolved gas may clog the pores of the reservoir rock near the extraction well and therefore reduce the effective permeability, which can result in reduced production of geothermal waters. This project is aimed at experimentally investigating the conditions of the onset of the degassing process and what the influence of the degassing process is on the permeability. Therefore Bentheimer and Berea sandstone core flood experiments were performed, using either tap water or brine with different CO2 concentrations (0.2 1.3 mol/L) and at temperatures between 30 and 90°C. Flow rates were varied/kept constant, between 90 2 bar and between 5 and 22 bar respectively.

At 30 °C and up to 50 bar the onset of the degassing process is controlled by Henry’s law, i.e. it is governed by the solubility of gaseous CO2. The onset of the degassing process is not influenced by the pore size and initial permeability. At these conditions the effective permeability decreases by a factor 2 to 5 in the Bentheimer sandstone core and by about a factor 10 in the Berea sandstone core. This change in effective permeability is gradual in the Bentheimer sandstone while in the Berea sandstone the change is nearinstant. For rocks with small pore sizes and low initial permeability, the reduction in effective permeability is larger and the rate of permeability decrease is faster.

Experiments at temperatures between 30 and 90°C show that with increasing temperature Henry’s law becomes increasingly inaccurate to find the onset of the degassing process. The onset degassing pressure increases with temperature but are significantly lower than Henry’s law. This inaccuracy can partly be explained by the fluid in the core not reaching the right temperature or by the values used for extrapolating Henry’s law for different temperatures. In experiments performed with a 1M NaCl brine the pressure at which the degassing process starts is higher than for experiments performed with tap water. The increased salinity does not influence the change in effective permeability due to degassing. The reason for this is that the change in interfacial tension between CO2 does not change sufficiently between tap water and Brine to cause differences in the degassing process.

The results obtained from this research can be used for successful management of geothermal projects. It shows at what conditions the degassing process starts and what the effect of this process is. Once the conditions are known they can be avoided. The research also shows the degassing process and its effects can be reversed.

Chalk putty is a soil-like material that is formed when intact chalk is disturbed. Recently, it has become of special interest due to the development of offshore wind farms in the North and Baltic Seas, where in a number of sites piles are driven into chalk strata. Several pile tests reported in the literature show increased shaft capacity up to 4 months after driving. Although it is a widespread remark in the scientific publications that chalk properties improve over time, laboratory replications of this phenomenon are scarce and the results are inconclusive. The aim of this thesis is to develop a specimen preparation technique yielding representative specimens as well as feasible for commercial purposes. Thereafter, the evolution of the characteristics of chalk putty over time is assessed through laboratory tests. Triaxial with Bender Elements, Direct Simple Shear, Constant Rate of Strain and Thixotropy have been conducted on specimens aged up to 3 months. Finding that the behavior of chalk putty cannot be classified among the classic types of soils. On one hand, Constant Rate of Strain tests have shown that the response is comparable to silty soil, with a gradual transition between re-loading and virgin compression lines, leading to difficulty in the determination of the yield point. On the other hand, in shear, the critical state friction angle is in the range of dense sand. Regarding the volumetric response, there is an initial compressive response, succeeded by a constant volume phase during destructuration and eventual dilation or contraction at larger strains. Furthermore, it was determined that the material possesses thixotropic properties when mixed with de-ionized water. Finally, no increase in the shear strength or was recorded while the initial shear stiffness decreases with aging time -due to unconfined preservation of the samples. However, the ultimate dilatancy of the specimens increases over time, this may be a result of dissolved calcium carbonate during crushing and saturation which re-precipitates or re-cements around the grains.

For many decades, conventional gravitational separators have been the backbone of the fluid separation in the oil and gas industry. The stricter environment regulation for purification of the recycled water, together with a tighter profitable margin of the produced oil, requires more efficient and faster separators. Inline swirl separator uses centrifugal acceleration up to hundreds of gravitational accelerations to perform separation in a much faster time. However, its efficiency is still lower than the industry expectations. There are essential geometric parameters such as swirl intensity and the collector tube, and vital operating conditions such as flow-rate at the entrance and mass flow-rate at each exit that impact the dynamics behavior of swirl flow in the pipe. The dynamic behavior of the swirl flow determines the efficiency of the apparatus. Thus, the main objective is to understand the dynamics of the single-phase swirl flow in the pipe and determine an inline swirl separator that presents sufficient efficiency. The first part of the study focuses on a better understanding of the dynamic behavior of the swirl flow in a pipe. The second part utilizes the results from the first stage to determine an inline swirl separator that presents sufficient efficiency. The performed numerical study suggests that the dynamic behavior of swirl flows in a pipe is determined by the intensity of the swirl flow, which is quantified by the swirl number. The swirl intensity shapes the axial velocity profile at the core of the vortex. When the swirl number increases beyond a critical number, a columnar vortex appears, with a reverse flow along with the center of the entire tube. The swirl intensity decays along the wall of the pipe; the swirl intensity and the decay of it form the shape of the axial velocity profile. In case the disturbance of the flow results in a stagnation point at the vortex axis, it may develop a vortex breakdown. The vortex breakdown in high Reynolds numbers ( Reb > 100,000) is a function of the swirl number, and the instability at the vortex core increases by increasing the swirl intensity. Furthermore, the results show that the stability of the vortex is a function of the Reynolds number. Considerable reduction of the Reynolds number kicks in the effect of viscous forces, which stabilize the vortex core. Reynolds and swirl numbers determine the dynamic of the low Reynolds number but turbulent, swirl flow. Therefore, the industry needs to rely on Reynolds Averaged Navier-Stokes (RANS) simulations; Direct Numerical Simulation predictions obtained at much lower Reynolds numbers may not predict the occurrence of the vortex breakdown inside the pipe. These findings show that there are essential design considerations, which determine the efficiency of the swirl separator. Thus, a combination of the geometry parameters and the swirl flow characteristics should be considered to avoid the reverse flow zone and vortex breakdown inside the inline separator. One of the vital elements of the inline swirl separator is the collector tube. The study shows that the collector tube at the neutral flow split, with no bias of the mass flow-rate at each outlet, changes the velocity to the extent that he reverse flow zone for Sw=0.5 is eliminated. Pressure actuators can control the flow; therefore, controlling the flow split at both outlets. The numerical results show that an additional percentage of flow split enhances efficiency by eliminating the reverse flow zone for the higher swirl numbers. Additionally, the study reveals the counter effect of the extreme flow splits, which hinders the efficiency of the inline swirl separator. These optimal settings for the geometry of this research were found at swirl number 1.6 and flow split of 50%.

This study discusses the potential of the in-depth water diversion (IDD) process to enhance oil recovery from subsurface reservoirs and investigates IDD strategies through an ensemble optimization approach. Pilot studies in the North Sea performed in recent years have shown that Sodium Silicate can be applied as blocking agent, diverting water to unswept zones of the reservoir. On the other hand, numerical simulation studies have tried to simulate the IDD behaviour with methods based on weak coupling of a reservoir flow simulator and an external chemical module. This study presents a fully implicit coupled chemical-compositional-flow implementation to simulate the permeability reduction through silicate gels, since IDD is essentially a coupled flow-chemical process. In addition, this study discusses the impact of resolution in space and time on the simulation performance for 2D subsurface petroleum reservoir models. Sensitivity of the oil recovery, and IDD characteristics such as moles of silicate, to design parameters of the IDD process is discussed as well. Since adjoint gradients are not typically available for the parameters describing in-depth divergence and the uncertainties are expected to be large, the optimization study uses an ensemble-based methodology to find optimal IDD reservoir management strategies. In addition to discussing IDD strategies in a deterministic setting, the design of optimal IDD strategies under geological uncertainty is investigated. This study will demonstrate that the in-depth divergence process can be used to extend the reservoir field production life time when timing, size of the Sodium Silicate batch and concentration is optimized. Finally this study discusses the issue of computational costs associated with modeling high resolution required for accurate simulation of this coupled process.