Suspension flow in porous media : investigating external and internal filtration
Creators: name: Jaffal, Hamza
Publisher: name: The University of Texas at Austin
Year: 2020
Subjects: Suspension
Porous media
Filtration
Mudcake
Rheology
Soil improvement
Grouting

description: Suspension flow through porous media pertains to many applications across different disciplines of engineering. This dissertation aims at advancing the fundamental understanding, characterization and prediction of the interactions between suspensions and porous media with a focus on geotechnical and petroleum engineering applications. A combination of analytical modeling, based on the new proposed hypotheses of the governing physics, and experimental work, to validate the proposed models and measure their input parameters, is used throughout the different chapters. First, external filtration during oil wells drilling is investigated. During overbalanced drilling in permeable formations, part of the mud fluid seeps from the wellbore to the formation, leaving an external filter-cake on the wellbore wall. To better describe the filter-cake buildup and its properties, a predictive filtration model, considering temporal development of the filter-cake under static and dynamic conditions, is developed and experimentally validated. The new model predicts the change in the external filter-cake properties across its thickness, rather than average values for the whole layer, utilizing the principles of effective stresses and consolidation. Next, a non-Newtonian fluid injection method is developed to estimate the most probable geometries of a fracture network within non-permeable formation. This information is critical when selecting the optimal grout mix to use. Currently, Lugeon (water pressure) tests are used to estimate the transmissivity of a fracture network, which is then used to estimate a representative fracture aperture for grout selection. However, this test does not provide information on the size distribution of different fractures within the same test section. A new method consisting of injecting non-Newtonian fluid is proposed and experimentally validated using injection tests through parallel fractures. The new method was found to be useful in identifying the aperture of different fractures, with better estimates of apertures of fractures controlling flow. Suspension flow through fractured permeable formations is accompanied with fluid loss into the formation and solids deposition on the walls of the fractures. The effect of this phenomenon in wellbore strengthening has been observed and documented in recent literature. However, the mechanism of fracture sealing due to filter-cake buildup within the fractures is not fully understood. To address this problem, the previously developed external filtration model is extended to account for the two-dimensional flow deposition. A new experimental setup was developed to evaluate the proposed model for external filter-cake buildup within pervious fractures and provide experimental evidence of the buildup sequence and mechanism. Finally, internal filtration during permeation grouting is experimentally investigated. Permeation grouting is the process of injecting a suspension into soil’s pores to improve its engineering properties. However, uncertainty in predicting grout propagation due to deep-bed filtration and soil heterogeneity has limited its applications in many cases. In this study, the effects of suspensions’ rheology and stability and soil heterogeneity on filtration and grout propagation are investigated using custom built 1D and 2D grouting setups. The results showed that even high w/c ratio grouts can generate uniform grouting if properly designed to limit filtration.