Experimental study on sand control gravel particle gradation optimization in mud hydrate reservoir

Sand production significantly influences the safety and stability of gas hydrate exploitation in reservoirs with high mud content. Gravel packing is an effective method for sand control. The median grain size ratio (D50/d50) values and fine particle content of gravel pack are important factors in sand control during natural gas hydrate exploitation. This paper focuses on the sand blocking effect and permeability characteristics of different grades of gravel. The sand retention test was carried out on four samples with different ratios. The optimal D50/d50value and fine particle content for gas hydrate production were obtained. A laser particle size analyzer and geotechnical test found the reservoir and gravel layer pore structure change. The results show that the optimal GSR was 24.5, and the optimal fine particle content was about 38%. The permeability decline of the gravel layer occurs in the early stage of production, and the fine particles in the gravel will slow down the degree of seepage damage. For gravel with the same particle size range and different median particle sizes, it has little effect on sand control accuracy but mainly on permeability. The research in this paper can provide a reference for selecting sand control gravel for natural gas exploitation in marine areas