Msc Thesis Presentation 20-06-2018
Time: 12:45 – 13:30, June 20
Bas van Dongen,
Title: Economic status and potential of deep, direct use geothermal systems in the Netherlands
Description: For this thesis a techno-economic model is developed to research the status and potential of multiple deep, direct use geothermal systems in the Netherlands. High initial investment costs accompanied by moderate cash flows create a challenge for Dutch geothermal projects to be economically feasible. This model is a tool to research the financial obstacles of a project starting from the exploration phase until well abandonment and illustrate the economic effects of government subsidies (SDE +) and project design decisions. Uncertainty in any aspect regarding technical and financial aspects are implemented in the model in the form of probability distributions. Multiple scenarios are inserted as discrete variables of equal probability. The model will be used on different case studies: 1) a geothermal field with a single doublet, 2) a geothermal field with multiple wells 3) a case of geothermal heat production from abandoned oil/gas wells without new drillings 4) A deep geothermal scenario where a cogeneration of electricity and heat production is considered. For these different scenarios, the Net Present Value (NPV) and the Levelized Cost Of Heat (LCOH) are determined together with a sensitivity analyses of the models inputs. With this method a complete overview is developed of the economic feasibility of each particular project including a visualization of the effectiveness of the Dutch subsidy scheme and the main financial obstacles. From these results suggestions can be made about project design and in revising the SDE+ grant for future geothermal projects.
Title: Surfactant-polymer chemical EOR and subsequent oil bank formation
Description: The focus of this project is evaluating the oil bank formation and displacement during a chemical flood. Core flood experiments are performed on Fontaine Blue sandstone cores, which are very clean sandstone cores with permeabilities ranging from 30 mD to 140 mD. Each experiment starts with a tracer injection to have an estimate of the pore volume of a core. Next step is to saturate the core with dodecane or iodododecane oil, which is supported by the presence of a very water-wet porous plate that inhibits the flow of oil. After the oil filling a water flood is performed, initially at a typical field rate of 1 foot/day for one pore volume, but after that at much higher injection rates to approach residual oil saturation as closely as possible. Following the water flood is a chemical flood consisting of half a pore volume of a surfactant-polymer mixture and one pore volume of a polymer solution; the chemical flood is followed by one pore volume of brine. In this flood the surfactant is the component driving the incremental oil by lowering the oil interfacial tension, while the polymer provides a more efficient sweep due to it’s higher viscosity. Generally, optimal displacement with mobility ratios smaller than 1 is tried to be obtained by injecting a polymer solution with higher viscosity than the surfactant-polymer slug, which in its turn has a higher viscosity than the oil.
For some experiments, the oil displacement is monitored using CT-scans, which show the effectiveness by which the oil is displaced. In these scans one can clearly distinguish the oil phase from any aqueous phase due to the differences in density and chemical composition.
After a completed experiment relative permeability curves are generated using two closely related methods. The first one is the Buckley-Leverett method wherein oil production is calculated and matched with the experiment’s oil production by using fitting Corey exponents. The second method is the Johnson-Bossler-Naumann (JBN) solution where an experiment’s injection, production and pressure data are used as an input.
Title: Parameterization of element balance formulation for reactive compositional flow and transport
Description: We present a novel nonlinear formulation for modeling reactive-compositional transport in the presence of complex phase behavior related to dissolution and precipitation in multi-phase systems. This formulation is based on the consistent element balance reduction of the molar (overall composition) formulation. To predict a complex phase behavior in such systems, we include the chemical equilibrium constraints to the multiphase multicomponent negative flash  calculations and solve the thermodynamic and chemical phase equilibrium simultaneously. In this solution, the phase equilibrium is represented by the partition coefficients whereas the chemical equilibrium reaction is represented by the activity coefficients model. This provides a generic treatment of chemical and thermodynamic equilibrium within an EOS SSI loop by modification of the multiphase flash to accommodate chemical equilibrium. Using the Equilibrium Rate Annihilation matrix  allows us to reduce the governing unknowns to the primary set only while the coupling between chemical and thermodynamic equilibrium is captured by a simultaneous solution of modified multiphase flash equations. An input in this thermodynamic computation is an element composition of the mixture when an output contains fractions of components in each phase, including solids. This element balance molar formulation along with the modified formulation for multiphase flash has been tested in a simple transport model with dissolution and precipitation reactions. The same approach will be later used to model a system involving kinetic reactions. The simulation of more general practical models is performed using the recently developed Operator-Based Linearization (OBL)  technique. In the modified version of the OBL, the nonlinear element based governing equations are formulated in terms of space and state-dependent parameters constrained by the solution of the extended multiphase flash based on molar element compositions. This approach helps us to add equilibrium reaction capabilities to the computationally efficient OBL technique.