An experimental investigation on the influence of temporary plugging fibers and particles on the fracture conductivity

Abstract

After temporary plugging and fracturing, some of the difficult-to-degrade temporary plugging agents (fibers and particles) in the fractures will affect the conductivity and ultimately affect the rate of oil production. However, the influence law and mechanism of the fibers and particles on the fracture conductivity are still unclear. In order to solve this problem, based on the FCS-842 fracture conductivity test system, the influence law and mechanism of fibers and particles on the fracture conductivity were investigated. The experimental results show that the larger particles support the fracture wall when particles are contained, resulting in higher conductivity. Further studies have found that high fibers content will lead to a significant decrease in the fracture conductivity under low closure pressure. However, high particles content means high fracture conductivity. The placement position of fibers and particles also affects the fracture conductivity. When the pressure is 10 MPa, the conductivity is maximum when the fibers and particles are placed at the fracture opening. Then, when the pressure increases, the conductivity drops sharply by about 88%. When the closure pressure is ≥ 20 MPa, the conductivity is the highest when the fibers and particles are placed at the fracture tip, followed by the middle of the fracture and the smallest at the fracture opening. After analysis, at the fracture opening, the high flow velocity forms a fiber “Barrier” in the fracture, which makes the conductivity decrease rapidly. In the middle of the fracture, the “Dot-net” structure composed of fibers and particles makes the fracture conductivity decrease, but the decrease amplitude and speed are small. At the fracture tip, the lower flow rate makes the fibers and particles form “Clusters”, and the large flow channel between the clusters makes the fracture conductivity higher than the former two. When the fibers and particles are evenly laid, the fibers are easy to form clusters with the particles to block the flow channel, reducing the fracture conductivity.