Erosion Damage of Lateral Holes in Multilayer Fracture-Packing Operation String: Experiments, Model, and Application

Summary Multilayer fracture packing is a sand control well simulation technology that can increase production in loose sandstone reservoirs. The operation pipe string is the main equipment during a multilayer fracture-packing job. The tools used in the field have problems with erosion damage, which restricts the service life of the pipe string. To investigate the effect of erosion damage on fracture-packing pipe string and lateral discharge holes, we construct an integrated experimental system, which includes an erosion simulated wellbore and a simulated operation pipe string, to study the erosion damage under different conditions, and analyze the factors of the erosion damage and their sensitivities through eight sets of experiments. On this basis, the prediction model of erosion damage and service life is constructed by numerical simulation, and the correlation is 85.5%. The results show that the erosion damage of lateral discharge holes has four processes—coating disappearance, surface wear, splash back gnawing, and form extension—and its damage includes three mechanisms, namely, tip lateral cutting mechanism, end face lateral cutting mechanism, and particle splash back frontal nibbling mechanism, which alternately cause the erosion damage of lateral discharge holes. Among the control factors, the pumping rate and proppant ratio are the key factors in controlling the rate of the erosion damage of the discharge holes, a 56% increase in the pumping rate results in a 62% increase in the erosion rate, and a 100% increase in the proppant ratio results in a 300% increase in the erosion rate, while the viscosity of the sand-carrier fluid has less influence on the erosion damage of the discharge holes due to the influence of shear dilution. According to the experimental results, a prediction model of erosion damage rate and erosion life of lateral discharge holes is constructed. The model is applied to evaluate the erosion damage of multilayer fracture packing in typical loose sandstone reservoirs in the Bohai Oilfield to verify its reasonableness and provide support for optimal design. The analysis of the results shows that a 100% increase in the pumping rate results in a 74.38% decrease in the service life, and a 100% increase in the proppant ratio results in a 37.88% decrease in the service life. Among the structural parameters of the pipe string, increasing the wall thickness or inclination angle of the inclined plane of the pipe string can significantly reduce erosion damage of lateral discharge holes and extend the service life of the pipe string. The research innovatively considers the influence of the structure of the pipe string and splash back against corrosion damage and the erosion rate and service life prediction model comprehensively considers the factors affecting the erosion effect and has a high fit with the actual situation on-site. Erosion rates and service life can be predicted quickly and easily with limited underlying data available in the field. The research provides a basis for quantitative prediction of the erosion damage of a fracture-packing operation pipe string and provides strong support for the optimal design and life enhancement of lateral discharge holes.