Master of Science in Petroleum Engineering (MSPE)
Water injection is widely used for sweeping hydrocarbons in waterflooding operations, and also for maintaining reservoir pressure or disposing waste water. Injection at a high rate is required to maintain the economy of waterflooding projects; however, loss of injectivity is a quite common problem in unconsolidated sand formations like deep water Gulf of Mexico. Well intervention operations, hurricanes, and other issues require frequent shut-downs during the life of offshore wells; in order to minimize deteriorating effect of these shutdowns on wellbore injectivity more accurate modeling of the injection process is needed. Injection of water into a saturated, granular, porous medium can lead to internal erosion and consequently formation of preferential flow paths within the medium due to channelization. Channelization in porous medium might occur when local fluid-induced stresses become locally larger than a critical threshold; then grains are dislodged and carried away, hence porosity and permeability of the medium will be altered along the induced flow paths. Vice versa, flow back during shut-down might carry particles back to the well and cause sand accumulation and consequently loss of injectivity. In most cases, to maintain injection rate operators increase injection pressure and pumping power. The increased injection pressure results in stress changes and further channelization in the formation. Experimental lab studies have confirmed the presence of dependent and independent flow patterns (Huang, 2011, Golvin, 2011). Considering the above-mentioned scenarios, long-held assumptions like Darcy flow or homogeneity and symmetry of flow paths are no longer acceptable for fluid flow at most of the injectors. There is a need for models to describe flow patterns and predict probable issues for water injection at the reservoir scale. A finite volume model is developed based on multiphase volume fraction concept that decomposes porosity to mobile and immobile porosity where these phases change spatially and evolve over time and lead to development of erosional channels in radial injection patterns depending on injection rates, viscosity, and magnitude of in-situ stresses and rock properties. This model will account for both particle releasing and the suspension deposition. Sensitivity studies on the effect of failure criteria for unconsolidated sand, flow rates, cohesion and permeability shows qualitative agreement with experimental observations.
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Ameen, Sayamik, "Dynamic Modeling of Channel Formation During Fluid Injection Into Unconsolidated Sands" (2013). LSU Master's Theses. 2092.