Objectives/Scope

During the initial flowback after fracturing unconventional wells, oil, gas, and water rates, as well as pressure data, are usually available on an hourly basis. Therefore, even though flowback may only take a few weeks, there are hundreds of available data points. We can utilize the data to predict early well performance for economics evaluation and further stretch to obtain an indication of long-term EUR. This paper outlines the innovative approach taken to predict short-term cumulative oil production and long-term oil EUR using hourly flowback data based on both physics and empirical correlations.

Methods/Procedures/Process

Unconventional wells produce in the linear flow regime in early time. During this period, the production depends on pressure, fracture surface area, and reservoir and fluid properties, which could be lumped into one term and obtained from the linear slope of the RTA superposition time plot. Most wells exhibit a linear flow signature during the flowback period and thus the linear slope can be obtained. Hundreds of Permian wells with hourly flowback data were utilized to obtain the slope. The values of a combined term of the inverse of this slope and initial pressure for these wells were plotted against their corresponding one-year cumulative oil production and EUR. From this analysis, correlations for both one-year cumulative oil production and EUR have been established.

Observations/Results/Conclusion

Using these correlations based on historical wells, the one-year cumulative oil production and oil EUR of a new well can be estimated with just a few weeks of flowback data. We named the EUR from this RTA linear flow-based correlation LinearFlow-EUR.
We validated this innovative method based on hourly flowback data in new wells in different benches in both Midland Basin and Delaware Basin. We also validated the method with dynamic reservoir simulation. The correlations can generally predict one-year cumulative oil production and oil EUR within reasonable ranges, even though the correlations are only based on linear flow regime while the pseudo-steady state depletion is not considered.

Applications/Significance/Novelty

This new method provides an early performance indication for new wells, new benches, or new areas. The application of the method could speed up completion trials and appraisal processes tremendously and optimize field development plans.