Laboratory evaluations of fiber-based treatment for in-depth profile control

Inspired by the successful implementation in acid fracturing, a fiber-loaded suspension system was designed to investigate inlet injectivity, in-depth mobility and overall plugging effect in unconsolidated high permeability sandpacks. In this paper, a series of experiments were conducted to screen suitable fiber suspension, including additives selection and dynamic plugging tests. Results showed that the formulation of 0.02 wt% citric acid+0.1 wt% YC regulator+0.1 wt% sodium tetraborate+0.12 wt% HPG displayed satisfactory dispersity. Sandpacks equipped with three pressure gauges to detect pressure changes were used for physical experiments. Four parameters (fiber length, fiber concentration, injection rate and permeability) that influenced the plugging efficiency were under discussion. The results revealed that relatively slow injection helped stabilize inlet pressure below upper limit. Three pressures increased in sequence during the subsequent water flooding, indicating that fibers moved forward with permeability reduction in sandpacks. The pressure dropped down but maintained at a high level after the operation finished. By comparison, 0.3 wt% 1000 μm-long fiber injected at the rate of 1 mL/min was found to achieve the best performance under the permeability of 4000-7000mD. And the more serious the heterogeneity was, the more significant the diversion ability of the high permeability layer was. Noticeably, the fluctuations were observed in pressure curves, which was further interpreted by the dynamic plugging mechanism of fiber in four transport processes: “migration-capture-redirection-recapture”. With unique slender shape, fibers were flexible enough to bridge and create a compact three-dimensional network structure along the flow direction. Due to high plugging strength and strong penetrability, the new fiber suspension system proves its potential to be an environmentally-friendly candidate in the selection of in-depth diverting agents. The evaluation and mechanism analysis may provide guidance for the operation design of profile control.