Flowback of hydraulically fractured shale wells is one of the key steps to delivering optimum early return rates and long-term economic gain of the field. This study presents a method to history match flowback of a well in the oilrich Permian basin using a transient multiphase flow simulator. It aims to provide insights into wellbore conditions during flowback from two aspects: bottomhole pressure profile and solid particle distribution in the horizontal wellbore over time. History matching of flowback was achieved and showed good agreement with the measurements. The simulation results indicated that bottomhole pressure observed with proppant sand included in the model can be utilized in the secure operating envelope to protect fractured well performance from poststimulation operation. In addition, proppant transport and distribution were revealed; as proppant density and diameter decrease, there is less proppant settling in the wellbore during the flowback process. The up and down movement of the proppant bed height in the wellbore corresponds with the wellbore schematic. The work in this paper improves the understanding of proppant behavior in the wellbore during flowback operations. The data and simulation results demonstrate the importance of including multiphase flow simulation combined with solid particle transport model to examine and ensure the flowback operation quality.
"Proppant flowback," "proppant back production," and "proppant production" are all terms used to describe the problem of proppant being produced out of a hydraulically created fracture during treatment cleanup or reservoir production (Parker et al. 1999). This occurrence creates several problems. Reports from operators conclude that mitigation for proppant flowback could reach up to USD 280,000 per well (Melisaris 2016). If the choke valve at the surface is opened aggressively, a huge pressure drop is created, which could mobilize the proppant in the fracture tunnels. Lu et al. (2018) conducted study on downhole pressure fluctuation impact on the fracture integrity and the results suggested high risk of losing fracture connection and creating sanding during the severe bottomhole pressure oscillating period. Overtime, if a cavity develops near the wellbore and as fluid pressure decreases during production, this leads to fracture width decreasing and conductivity being reduced near the wellbore. After the proppants are removed from the fracture, proppant cannot contribute to fracture conductivity or reservoir production. Proppant removed from the fracture can also cause mechanical problems with downhole equipment (Vreeburg et al. 1994). At the same time, if the choke opening is too conservative, the well is not optimized to the well's true potential of producing. As such, it is critical to understand the effect of choke opening on sand production at the surface and how proppants are transported along the wellbore during the flowback period.
