Friction calculation and packing effect analysis for gravel packing in deepwater horizontal wells

Gravel packing is one of the most commonly used well-completion methods for controlling sand production in deepwater horizontal gas wells. Both the gravel-packing mechanisms and the technical difficulties of gravel packing in a horizontal well are discussed in this paper. Subsequently, packing simulations were conducted based on geological data from a well in the LS gas field in the northern South China Sea. The factors influencing the gravel-packing process were quantitatively analyzed. The influences of the pump rate, carrying fluid leak-off ratio, and density of gravel on the sand-dune ratio of the alpha-wave, height of the sand dune, packing length of the alpha-wave, and packing pressure were analyzed. The results show that the pipe string injection friction is the largest at the slurry injection stage and the alpha-wave packing stage. In the beta-wave packing stage, the downhole horizontal flow friction becomes the main pressure loss. The friction increased when the beta-wave packing reached the heel of the horizontal wells. As a result, the packing pressure can easily exceed the formation fracture pressure. Furthermore, the lower the pump rate, the higher the sand-dune ratio, which would cause premature screen-out and blockage. Therefore, optimizing the pump rate is essential to ensure that the sand-dune ratio meets the designed requirements. Under a certain leak-off rate, the lower the gravel density, the longer the packing length of the alpha-wave. For a long horizontal well, the step-down method can be used to control the packing pressure during the beta-wave packing stage. The results provide technical support for field gravel packing.