Two key goals for proppant selection and injection optimization are economical mitigation of proppant flowback and achieving optimum conductivity throughout fracture area from near wellbore to far field. Improvements in these areas benefit project economics through cost reduction and production uplift. This paper highlights the implementation learnings and success results of CounterProp to reduce proppant flowback and increase near wellbore conductivity in Permian shale and tight development.
CounterProp proppant injection sequence (large particle size proppant pumped first before small particle size) was introduced by Ely et al (2019) in the paper SPE-194370-MS for slickwater treatment in low permeability shale and tight reservoirs. Two internal studies were carried out to validate CounterProp design impacts. Hydraulic fracture simulation models were completed, and laboratory study was performed to improve understanding of proppant transport behavior and evaluate impact of CounterProp. The laboratory study used large-scale tortuous slot flow equipment with slickwater and different proppant sizes and sequences. The model and laboratory study results indicated that larger proppant settled near wellbore, creating a barrier to prevent smaller proppant grains moving into the wellbore, thereby mitigating proppant flowback and generating higher fracture conductivity in near wellbore area.
An iterative and phased approach for field implementation was applied to reduce the execution risk of injecting large size 40/70 mesh proppant before small size 100 mesh with slickwater. Multiple field trials have been executed since late 2019 in both the Midland Basin and Delaware Basin. The first trial was implemented in a Lower Spraberry development in Midland Basin where proppant flowback was not an issue, a production uplift was expected with higher near wellbore conductivity, and the perceived execution risk was minimal. In Lower Spraberry, a range of median uplift from 5-42% cumulative oil was measured compared to offset control pads. In Delaware Basin, proppant flowback during early production phase is an issue handled with surface sand separator equipment, and the goal for CounterProp was to reduce the time and cost of sand separator equipment on location. CounterProp was implemented in multiple Wolfcamp developments in Delaware Basin with no execution issues and resulted in decreased proppant production compared to similar developments thereby allowing release of proppant flowback management equipment from these locations approximately 70% earlier, contributing to savings and production benefit with higher pressure drawdown allowed.
This paper shares a success story from specific examples of CounterProp applications with slickwater in Permian low permeability shale and tight reservoirs. CounterProp field trials have proven as low risk solutions for unconventional development with large potential upside of cost reduction from proppant flowback mitigation and production improvement with higher near wellbore conductivity. Further, application may be broad in Permian development, with low cost, low execution risk, and high benefit to long-term production and operations.