DEM-CFD coupling verification and analysis of a sand control medium structure with weakened particle blockage performance

This study addresses the prominent contradiction between solid phase control and production capacity release during the exploitation of natural gas hydrate in fine silty sand reservoirs. A novel mechanical sand control medium structure incorporating the filter slots/nets (referred to as the sand control component, SCC) and the cylindrical/spherical structures placed outside the SCC (referred to as the blockage control component, BCC) has been designed. Concurrently, a DEM-CFD sand-retaining numerical model is developed, and the traditional/new structural screens have been separately simulated for sand retention. Through the spatiotemporal evolution of DEM and CFD characteristic model parameters during simulation, the blockage mechanism and characteristics of fine particles are obtained. Compared to the traditional screen structure without a BCC, the existence of a BCC effectively evacuates particles within the accumulated sand body towards the wellbore, reducing the compactness and stress level within the sand body; while the pressure loss generated by fluid flow through the sand body decreases, significantly improving the porous and permeable conditions within the sand body. The degree of influence of a BCC on different DEM and CFD characteristic model parameters is further determined and ranked. A comprehensive blockage optimization index is introduced to quantify the performance of weakening sand blockage by the BCC and optimize the spatial position of the BCC. The BCC enables the design of sand control schemes to reduce the filter aperture of the SCC to a sufficiently small size to effectively control the fine silty sand production, while avoiding gradually severe blockage as production progresses.