Gravel packing: How does it work?

Abstract

Oil and gas wells undergo completion operations before being able to produce. In the case where the surrounding reservoir is poorly consolidated, a popular method is open hole gravel packing. This proceeds by pumping a sand suspension along the annular region between the borehole wall and a cylindrical screen, sized to allow hydraulic conductivity but to prevent the passage of sand. Kilometers of sand can be successfully placed in horizontal wells, in what is called α–β packing. Although widely used, there is no clear and concise explanation of how these operations work, i.e., How does a steady (and apparently stable) traveling α-wave emerge? We develop such a model and explanation here. We explain how bed height is selected via coupling between the inner and outer annuli and from the combined hydraulic relations of inner and outer annuli. We investigate the effects of important parameters such as the slurry flow rate, mean solid concentration, washpipe diameter, and leak-off rate on gravel packing flows, to give a fluid mechanics framework within which this process can be easily understood.