Experiments on the drag reduction effect of an open-hole packer with sand dredging grooves

In the process of staged fracturing in an open-hole horizontal well, an open-hole packer contacts the cuttings bed when it goes down to the open-hole horizontal section. As a result, the running friction resistance is increased gradually. And on the other hand, the cuttings accumulated in front of the packer tend to result in sand sticking and wear the packer rubber, which may lead to the deterioration of setting performance and the failure of the packer. In this regard, this paper designed and manufactured a simulation experiment device to research the effect of the cuttings on the running process of the packer into the open-hole horizontal sections. Then, based on the experimental results, the original packer was structurally improved and sand dredging grooves applied to an open-hole packer was designed. And the following experimental results were obtained. First, in the process of running into the hole, the open-hole packer is supported by the cuttings pile to contact the upper wall, resulting in a sharp increase of friction resistance and then sand sticking. And the friction resistance applied on the packer increases with the increase of running displacement and cuttings content. Second, after the packer is equipped with the structure of the sand dredging groove, cuttings flow through the sand dredging groove. As a result, the cuttings accumulation in front of the packer and the friction resistance on the packer running through the hole are reduced, and consequently the wear of packer rubber is diminished. Third, the number of sand dredging grooves in the improved packer model has a significant effect on sand dredging and friction reduction. In this experiment, the sand dredging effect is the best when the number of sand dredging grooves is up to 5. In conclusion, the research results provide a research idea and laboratory experiment basis for the further structure optimization of open-hole packers. © 2019, Natural Gas Industry Journal Agency. All right reserved.