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Abstract In our previous work (Jin et al. 2021), an experimental effort has been made to microscopically observe the sand failure, migration within a matrix, invasion to gravel packing, and production for openhole gravel packing, while three sanding patterns (i.e., fractures, wormholes, and fluidized channels) have been identified. The first pattern is associated with an uneven strain-stress effect, while the last two patterns result from liquid seepage. To theoretically reproduce our previous experimental measurements, in this study, the experimental techniques have been further modified and improved to eliminate the associated uneven strain-stress effect by uniformly injecting water to a radial flow vessel. Experimentally, by generating slots near the gravel packing, sand failure dynamics, sand flow paths, and sand production for the clayey-silt sediments can be microscopically observed, geometrically depicted, and volumetrically quantified conditioned to different operational conditions, i.e., no hydraulic slotting, single hydraulic slotting without proppant packing, single hydraulic slotting with different lengths, and double hydraulic slottings with different intersection angles. Theoretically, a wormhole growth model has been proposed to reproduce the sand production for both hydrate-free and hydrate-bearing sandpacks by considering the sand failure criteria as well as the porosity and permeability alteration models. Good agreements between the measured and simulated data (i.e., pressure and temperature profiles, gas and water production, and produced sand volumes) have been achieved. The experimental measurements show that hydraulic slotting is an effective stimulation manner to mitigate the skin effect near a wellbore and that a predesigned hydraulic slotting after well completion would decrease the hydraulic gradient near the wellbore and thus decrease the possibility of sand failure. It is revealed that the operational conditions dictate the sand failure patterns as well as the sand production volume together with the produced grain size. Similar to the hydrate production, the sand production is also divided into three stages, i.e., before dissociation (transport of free particles or weakly consolidated particles), during hydrate dissociation (sand detachment due to the loss of hydrate cohesion and massive water production), and after hydrate dissociation (transport of fully unlocked particles). It is shown from sensitivity analysis that cumulative sand production and permeability increment are affected with the following order from strong to weak: intrinsic failure resistance, tortuosity, Kozeny coefficient, and absolute permeability, while the breakdown pressure is dominated by the absolute permeability and the pressure of the stable stage is mainly dictated by the intrinsic failure resistance, tortuosity, and Kozeny coefficient.
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