ANALISIS EFEK GEOMETRI PORI TERHADAP ALIRAN NONDARCY DENGAN MENGGUNAKAN SIMULASI METODE LATTICE BOLTZMANN

• Main Author: KRISTOFER WOSPAKRIK (NIM : 22215027), STEVY
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/31105
• Institution: Institut Teknologi Bandung

Non-Darcy flow usually occurs in the area in proximity to the wellbore in gas reservoirs or factures from hydraulic fraturing. This is due to high velocity flow of the fluid and resulted in more pressure loss. In this flow regime the pressure loss is not in linear relation with fluid velocity. Additional pressure loss occurs due to the inertial flow of the fluid. In oil and gas production, this creates problem whether in gas reservoir, fractured reservoir or even in the multiphase flow into the wellbore. Many studies have been developed to understand the mechanism of Non-Darcy flow and to predict the flow parameters. Analitical approach usually comes from very simple model and the empirical approach is usually very specific to certain cases. Numerical approach is another option to model the fluid flow. In recent times, Lattice Boltzmann method has gained popularity due to its robust implementation on the complex geometry such as porous media. This open an opportunity to model the fluid flow in pore scale and to predict the flow behavior using Lattice Boltzmann method. <br /> <br /> <br /> This research was set up to assess the effect of pore geometry to the Non-Darcy flow. The fluid flow was simulated by applying pressure gradient until steady state condition was achieved. The flow parameters were then calculated from the average condition over the whole rock domain. The model tested were simple geometries such as diverging-conveging tube and regular sphere packing to test the contribution of pore geometry to the Non-Darcy flow. Several aspects of pore geometries were tested: aspect ratio, pore shape, and grain arrangement. Aspect ratio is the ratio of the diameter of pore body to pore throat, pore shape defines the angularity of the pore space and the grain arrangement is related with the sphere packing arrangement of the grain. After the results achieved from the simple geometries above, the simulation continues to more complex geometry to test the capability of Lattice Boltzmann method to predict the Non-Darcy flow parameters. <br /> <br /> <br /> The complex geometries consist of synthetic rock which was created using irregular sphere packing method and 3D real rock images from micro-CT scan. The synthetic rock was used as a bridging of the simulation to more complex pore geometries in the 3D real rock images. There were two real rock micro-CT images used in this study: Bentheimer sandstone and TG sandstone. Bentheimer sandstone 3D digital image was an open data source whereas the TG sandstone digital image were scanned from sidewall core from reservoir rock of TG gas field. The image resolution for Bentheimer rock is very high (~3.5 micron) whereas for the scanned TG rock is half lower of the resolution (8 micron). Bentheimer rock has very good grain sorting with clear intergranular pores. The digital image is also high quality suggesting detail image processing coming from high resolution scanner. TG rock scan result on the other hand had some amount of noises. The filtering process before the application of the fluid simulation simulation was to some extent compromised the image. Therefore, there was potential of the filtering process to the pore imaging whether to add or reduce the pore spaces. <br /> <br /> <br /> The result of the simulation indicated that pore geometry can affect the Non-Darcy flow. Aspect ratio and grain arrangement showed the high impact to the fluid flow. Aspect ratio affects the expansion-contraction of the fluid whereas the grain arrangement affects the flow direction. Both of these geometries generate a strong Non-Darcy flow. As for the shape factor, the angularity of the pore space does not significantly affect the Non-Darcy flow. <br /> <br /> <br /> The result from the synthetic rock and real rock samples shows a strong correlation between the permeability with the Non-Darcy coeffient (beta factor). The predicted permeability and the beta factor from the simulation falls within the empirical correlation. However, simulation from TG sample resulted in more pessimistic <br /> <br /> value of the permeability and the beta factor. This may indicate the quality of the image has introduced limitation to the extent of the LBM method to predict the flow parameters.