Proppant Flowback Management Using Fibers

Proppant flowback is a serious problem in hydraulic fracturing that not only reduces gas production, but also requires extensive and expensive cleanup operations and causes damage to the electrical submersible pumps (ESPs) and other well equipment. It can even cause well failures.

Proppant flowback occurs when the fluid in a fracture flows back towards the wellbore, washing away the injected proppants from the fracture surface. Proppant flowback can occur in cased hole completions as well as open hole completions. While a number of solutions have been proposed to prevent proppant flowback, there are still many challenges related to this issue. Proppant flowback can be caused by various factors, including cyclic loading and long-run operation periods of the well, which can significantly deteriorate the strength of the proppant pack.

One of the most important factors that contribute to proppant flowback is the high fracturing fluid viscosity, which results in a low conductivity in the fracture. It is therefore important to improve the conductivity of the proppant pack during fracturing. Among the different techniques, lowering the pressure of the fracturing fluid and increasing the conductivity of the proppant can help reduce the rate of flowback and prevent the erosion of the fracture.For more information click here

Another factor that can cause proppant flowback is the sand particle size and the ratio of the injected sand particles to the fracture size. The higher the percentage of injected sand, the larger the particle size and the lower the ratio, which can increase the risk of proppant flowback. In this case, it is important to choose the right type of sand for each application and to carefully control the fracture geometry.

To overcome these issues, new methods of proppant flowback management are being explored. One such method involves the use of fibers to strengthen the proppant pack and resist fluid erosion.

The fibers are injected into the fracture in the form of a slurry that consists of both proppants and fibers. The fibers delay the settling of the proppants and create gaps that serve as good channels for the fluid to flow during flowback. In a laboratory sand control experiment, it was found that the addition of fibers to the slurry increased the resistance of the proppant pack to fluid erosion.

Using the relationship between sand bank height variation and time, it was possible to find that there are two stages in the proppant flowback process: a strong fluid erosion stage that is reflected by the sharp undulation pattern of the sand bank and the rapid decrease of the sand bank height, and a slow fluid erosion stage that is reflected by the change of the relationship curve between the sand bank height and the time. The inflection point that appears later with full-fiber injection is much lower than that with other fiber injection modes, indicating that the addition of fibers greatly increases the strength of the proppant pack and its ability to resist fluid erosion during flowback.

The only characterization parameter currently available to describe the movement state of proppants during the flowback process is critical velocity, which is too simple and single-dimensional to reflect the detailed sand movement state and rule. This paper proposes a physical simulation method that can realize observation and fine description of the proppant flowback state and movement rule, which can provide a more accurate understanding of the behavior of proppants during the proppant flowback process.