Gravel Packing in Long Horizontal Well: New Insights into Dune Migration Patterns and Packing Parameter Optimization

Summary Gravel packing is a widely used sand control technique for horizontal wells in unconsolidated sandstone reservoirs. Traditional optimization methods for gravel packing parameters aim to maximize the gravel-packing rate. However, some horizontal wells with high packing rates still experience production decline after being put into operation. Improving the optimization method for gravel-packing parameters is crucial to ensuring the production capacity of horizontal wells. In this paper, we investigate the dune migration patterns during gravel-packing operations, identify key parameters affecting gravel-packing performance, and propose a new gravel-packing parameter-optimization method through gravel-packing operation and production simulation experiments. First, gravel-packing operation simulations reveal that the density difference between the sand-carrying fluid and packing gravel is a crucial factor influencing dune migration and gravel-packing density. A downward-deposited dune forms in the α-wave packing process of conventional ceramsites because of a large density difference, thereby forming premature bridges during migration and reducing the gravel-packing ratio. When reducing the density difference, α-wave packing with ultralight ceramsites forms an upward-deposited dune. This migrates from the upper side of the well toe to the lower side of the well heel, avoiding premature bridges but weakening the gravel particles’ compaction, resulting in lower packing density and reduced stability of the gravel layer and affecting the productivity of horizontal wells. Second, further production simulation experiments explored the impact of gravel-packing density on the performance of gravel-packed horizontal wells. Results show that even when the gravel-packing ratio reaches 100%, lower packing density in certain zones can lead to instability in the gravel layer, forming erosion holes due to uneven inflow, which may cause sand control failure. This instability indicates that gravel-packing density should be a key consideration in optimizing packing parameters to ensure stable and efficient horizontal well production. Finally, a new optimization approach is proposed to recognize the limitations of current gravel-packing parameter optimization methods, and its feasibility was verified using actual field data from two wells in the Sinopec Shengli Oilfield. The approach integrates three factors, wich are gravel-packing ratio, packing density, and operational safety window. A new set of indexes for gravel-packing ratio, density, and safety is introduced. Simulation experiments on horizontal well gravel packing have analyzed the effects of gravel concentration, sand-carrying fluid viscosity, pump rate, and gravel density on packing performance. The results show that significant antagonistic effects were observed among key parameters. High-viscosity fluids cannot tolerate high pump rates but can accommodate a slight increase in gravel concentration. Importantly, the use of low-density gravel is a critical factor for achieving overall optimization in horizontal gravel-packing operations. A reasonable gravel concentration (4–6%), sand-carrying fluid viscosity (3–7 mPa·s), and gravel density (1.28–1.84 g/cm3) can effectively enhance gravel-packing ratio and stability while maintaining high packing density and safety. This study provides new theoretical foundations and comprehensive guidance for optimizing gravel-packing parameters in horizontal wells and helping to improve the long-term stability and production capability of gravel-packed horizontal wells.