| Abstract |
Permeability is one of the key rock properties for the parameter in geothermal reservoir management. Permeability is highly dependent to other petrophysical parameters such as porosity, specific surface area, and tortuosity. Geothermal rocks generally contain crack type and granular type of pore space which can flow various kind of pore fluid, including steam in geothermal reservoirs. Pore space with high permeability indicates the ability to easily transport the fluid. This study aims to compare between two methods of estimating permeability of crack type and granular type of pore space in geothermal reservoir to later compare which type of pore that plays more important role in transporting fluids. We used Lattice Boltzmann Method and Kozeny-Carman relation to estimate the permeability. From these analyses, permeability of crack type and granular type obtained by Lattice Boltzmann are 141,490 mD and 148 mD respectively, then by Kozeny-Carman are 273,669 mD and 26,858 mD respectively. From both of the methods, it had been shown that the crack type has more important role to transporting fluid in the geothermal reservoir compared to the pore type. Kozeny-Carman relation is considered to be less accurate, because this method is usually more valid for the case of sandstone. Kozeny-Carman relation is direction independent, and is also highly influenced by the method of calculating the quantities in the equation, which are the porosity, specific surface area, the Kozeny constant (geometrical factor) and tortuosity. Lattice Boltzmann Method is considered to be more accurate then Kozeny-Carman relation, since it simulates the fluid transport through the pore space. Permeability estimated by Lattice Boltzmann method is direction dependent, thus can be used to further calculate the anisotropy permeability. Equivalent permeability which calculated using arithmetic averaging yield better results in estimating the unsegmented original sample which contains both type of pore space. |