Effect of soil grain size on the oil migration in the capillary fringe zone
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Date
2019-06
Authors
Lee Zheng Xian
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Abstract
Widespread demand for petroleum had lead potential problems associated with
underground storage tanks and oil pipelines. Over time, these pipelines and tanks can
have corroded and developed leakages. LNAPL had the complex parameter to allow the
LNAPL to move through the porous media under saturation condition, which is
depressing the capillary fringe zone. Therefore, the capillary height or the depth to reach
the capillary height is very important to be define as the depth is representing the location
of the remediation work to be carry out. The main objective of this research is to
determine the depression of the capillary fringe when encountered with diesel in different
grain size of sand samples. The One-Dimensional Column Test had been carried out with
the Image Analysis in order to determine the capillary fringe zone in the column
apparatus. With the different colours’ toning, blue water and red diesel, the captured
image is then processed by the MATLAB code to scale the toning. The darkest blue and
red represented 100% saturation of water and diesel. By determine the highest level of
100% saturation of water, the capillary height can be figured out. In this research, the
result showed that the smallest D10 value had the highest capillary height due to its largest
adhesive force among sand particles. Besides that, the diesel poured into the sand
samples and the depression of capillary fringe zone had been determined. The results
showed the diesel can depress more capillary fringe zone in the smaller grain size of sand
samples. This can be explained as capillary force is an equilibrium force of adhesive
force and gravitational force based on Young-Laplace theory. The capillary force acting
same direction as the gravitational force had pushed the diesel downward more easier in
smaller grain size sand samples as they had the bigger capillary pressure to form the
diesel plume in order to penetrate downward through the sand samples.