Study on Sand Production Evolution Mechanism of High Muddy Silt and Fine Sand Hydrate Reservoir Exploitation in Sea Area

According to the grading curve and Water content allocation of the hydrate reservoir, the particle size distribution and water condition of the formation sand are simulated, and the gas drive pressure difference condition is set. Under the condition of gravel packing and sand control, the one-dimensional unidirectional flow of high argillaceous and fine sand under gas drive is analyzed, and the parameters such as displacement pressure difference, flow rate, sand proportion and permeability are measured. The three phase percolation law of gas, water and solid particles from the initial stage to the end of the test was systematically analyzed. The results show that the evolution process of sand production is divided into four stages: initial particle-free migration, slow particle migration, rapid particle migration and particle structure stability. The time of specific process is controlled by pressure difference and gas-water flow conditions. Because of the high mud content, the slow migration phase of the particles will migrate and consolidate on the outer wall of the sand retention structure to form a mud layer (permeability is 0.1–5 Milli Darcy). The mud layer has a certain stable structure and strength, which has a significant influence on the water flow conditions and has no obvious influence on the gas percolation. The test results reveal three mechanisms for the exploitation of natural gas hydrate reservoirs, namely the sanding evolution process, the gravel filling sand blocking and the mud layer sand resistance with certain permeability and strength.