Experimental study on the formation mechanism of mud films in hydrate reservoirs under water-seepage coupling

Abstract

ABSTRACT In the exploitation of mud hydrate reservoirs, mud films are formed in unconsolidated mud reservoirs under the action of soil particle migration, which changes the permeability and sand retention effect. This can affect the failure mode and gas productivity of the reservoir. A self-developed experimental test system was used to investigate the mud film formation process and failure characteristics in mud reservoirs under gravel packing sand retention conditions at tangential flow rates of 0.424, 0.849, 1.273, 1.697, and 2.122 × 10−3 cm/s. The results indicated that (1) the flow velocity affects the mud film formation rate and (2) the flow velocity notably influences seepage flow. When the flow velocity is higher than 1.697 × 10−3 cm/s, the mud film and sand control layer suddenly fail, and the flow process changes from seepage to fissure flow. (3) Mud film formation results from soil particle migration, and mud films can control sand retention. (4) The mechanism of mud film formation is that water flow can lead to reservoir compression deformation under pressure. Water flow can result in seepage dominating in the reservoir. The above analysis results could provide a reference for groundwater injection and hydrate exploitation.