Measurement of Relative Permeabilities at Low Saturation using a Multi-step Drainage Process
Date
2014-01-30
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Abstract
The gravity drainage mechanism is important for both maximization of storage capacity of gas and depletion of oil from oil reservoirs. A sensitivity analysis based on numerical simulation of CO2 storage confirms that the liquid(s) relative permeabilities at low liquid saturations and the end points are important for both reservoir simulation and volumetric modeling of these processes.
This thesis employs the multi-step drainage process to determine the wetting phase permeabilities close to the end points. In this process, the wetting phase production history was modeled with fully-coupled capillary pressure, by numerical, analytical and pore-scale modelling methods. These models leads to corresponding relative permeability calculation methods, including numerical modeling with automatic history matching, direct estimation using analytical modelling, and an interactive tube-bundle model correlating the pore structure and the relative permeabilities.
The first step was to program a simulator in order to mimic the multi-step drainage process. A group of equations were employed to model the one dimensional multi-step drainage process according to Darcy's Law and the mass conservation equations. The equations were solved numerically using PcSim, a program coded using the C++. This program was used as a benchmark to all other models developed in this thesis. Using the program, automatic history matching was introduced as a conventional method to determine the relative permeabilities from the multi-step drainage process. Guo Tao genetic algorithm (GTGA) was successfully applied to history match the two-phase flow in a porous medium. The results indicate the application of the GTGA is faster and more reliable than the conventional genetic algorithm. It was also found that at low wetting phase saturation, the permeabilities of the wetting phase dominate the production history. Following that, an analytical method was developed to directly estimate the relative permeabilities of the wetting phase. The newly developed analytical method simplifies the calculation of the relative permeabilities close to the end points to a level as easy as calculation of absolute permeability using Darcy's Equation. In addition, an interactive tube-bundle model conceptually validated the findings and models developed in this thesis. Further development of this model could potentially be used to history match the experimental data. Finally, experiments carried out with both sandpacks and core samples indicate that these methods can be applied to measure the relative permeabilities close to the end points using a multi-step drainage process for gas/water, oil/water and gas/oil/water systems.
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Engineering--Petroleum
Citation
Wang, S. (2014). Measurement of Relative Permeabilities at Low Saturation using a Multi-step Drainage Process (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26848