Comprehensive experimental study on the sand retention media of pre-filled sand control screens

Sand production is a serious problem in exploring heavy oil wells and can cause sand well abandonment under severe conditions. Various sand control tools (e.g. slotted liner (SL) screens, wire-wrapped screens (WWSs), pre-packed screens, and premium screens) are recently developed. However, each sand control method has its drawbacks and limitations. Pre-packing gravel screens have not been improved compared with other screens to date. This study aims to optimize and improve pre-packing gravel screens. The influences of gravel size and packing densities and thickness on the production capacity and the amount of sand produced are studied. Experimental results show that the maximum packing densities of the gravel layer range from 59 to 68%. Moreover, the increase in the packing densities of the gravel layer increases the sand control effect but reduces productivity. No sand intrusion within the gravel layer and sand production occur when the packing densities of the gravel layer reach 62%. By contrast, if the packing densities of the gravel layer drops to 58%, then sand control failure occurs. The amount of sand produced increases as the thickness of the gravel layer decreases. The amount of sand produced significantly increases when the thickness of the gravel layer reaches 15 mm. The median size of gravel packed in the base pipe and outer protective screen should be 8-10 times the size of formation sand.