Novel Resin-Coated Sand Placement Design Guidelines for Controlling Proppant Flowback Post-Slickwater Hydraulic Fracturing Treatments

Abstract

Resin-coated sand (RCS) is an effective way for controlling post-stimulation proppant flowback. However, with the shift to slickwater treatment fluids, the “tail-in” placement approach has proved to be less efficient for complete flowback control due to the proppant settling characteristics of using low-viscosity fluids. A new RCS placement approach was developed based on the results of several flowback studies. Trial wells were completed in different US basins with successful results. Proppant flowback samples were collected during different stages of drillout and production from wells using slickwater fluid systems. Thirty-five wells, completed by thirteen different operators, within the Permian and MidCon basins were evaluated. All wells were completed using multiple proppant mesh sizes. A total of 375 flowback samples were collected during the drillout and production phases. The samples were sieved, and the results were fed into an in-house material balance model to determine the percentages of different mesh sizes in the flowback samples. The conclusions were used as guidelines for a new placement approach implemented in multiple new wells to control proppant flowback. The flowback samples ranged from predominantly lead proppant to a similar proportion of the pumped mesh sizes. Not one of the 35 wells had flowback samples containing the majority tail-in mesh size. This supports the early sand dune assumption, suggesting that the early proppant forms dunes near the wellbore and late sand settles over the existing proppant beds. The use of late RCS appears to have a minimal effect on preventing flowback of the early proppant within a stage utilizing slickwater fracturing. Therefore, RCS efficiency to control proppant flowback with the tail-in method is reduced when used in such slickwater stimulations. To seal the different proppant beds, the new approach recommends pumping multiple RCS steps within a stage. The first RCS step is recommended within the first 10–20%, the second sequence within the first 40–60% of proppant volume, and the third as a tail-in. The exact percentages and step design were based on the results of flowback samples from neighboring wells. The implementation of this approach in more than 30 wells resulted in superior flowback control compared to offset control wells. In all trials, the proppant flowback completely stopped within 1 to 7 days of starting production. In this paper, we discuss the drawbacks of the current RCS placement practice while suggesting a new practical approach supported by data. RCS tail-in showed successful flowback control with viscous fracturing fluids and hybrid systems. For slickwater systems, an optimized placement design for RCS throughout the pump schedule provided enhanced flowback control compared to RCS tail-in. Finally, we illustrate the results of field trials in which utilizing the new RCS placement approach successfully reduced flowback.