Experimental Study On Blocking Mechanism Of Sand Control Screen In Sand-shale Interbed

Sand production in oil wells is the most common problem in the oil extraction process,especially in loose sand and mudstone interbedded formations.In practical production,mechanical screens or screen gravel packing are usually used for sand control.The formation fluid carries a large number of solid particles impinging on the sand retaining layer.If the solid particles cannot be discharged smoothly,it will cause blockage of the sand retention layer,which will seriously affect the productivity of the well.The blockage of sand retention layer has become one of the most important issues that plague the normal production of sand control wells in major oil fields.The clear understanding of the mechanism of sand production in the formation,the blocking mechanism of the sand retention layer,and the sand control technology adopted are directly related to the economic development level of the porous sand and mud interbedded reservoir and the final recovery ratio.The research on the blocking mechanism of the sand retention layer in sand-shale interbed screen is very important for theory and engineer.In this paper,the blocking mechanism of sand control screen in sand-shale interbed is mainly studied by simulation experiments.At present,the existing researches on the blocking mechanism of sand control layer in oil wells mainly focus on sandstone formations,and due to the limitation of the material and size of experimental devices,there is a big difference from the actual sand production conditions.The experimental device designed in this paper can simulate the sand production characteristics of the sand-mud interbedded layer and simulate the full-scale radial flow jamming of the screen.Using this experimental device,the screen blocking simulation experiments under different influencing factors such as net/gross ratio,mud content of interlayer,shale mineral composition and well inclination were performed.It is concluded that the blocking mechanism of sand-shale interbed screens is different from that of sand screens.The experimental results show that in the sandstone formation,the screen is mainly blocked by the bridge,and the formation fluid carries sand from the formation into the sand retention layer of the screen,forming a bridge jam.In the sand-shale interbed,the screen blocking is mainly due to the adhesion of the mud in the formation,so that the formation mud sand forms a firm mud cake on the surface of the screen pipe,thereby directly blocking the screen holes outside the screen pipe.And part of the mud in the formation sand enters the inside of the sand retention layer of the screen pipe.Due to the muddy water swelling,the formed sand bridge is more solid and the plugging is more serious.