Analytical models available in Rate-Transient-Analysis (RTA) packages are widely used as fast tools for history matching and forecasting in unconventional resources. Recently, there has been an increasing interest in numerical simulation of unconventional reservoirs. In this presentation, both methods will be used to history-match fractured unconventional wells, followed by the application of forecast calculations. A single-phase shale oil reservoir will be used as a base case, but dry gas and gas condensate shale reservoirs will also be examined. In all cases, historical data and reference EUR’s are derived from fine-grid simulations.

The data presented will demonstrate an excellent match between the two methods for the base case, but when real-world deviations from RTA assumptions are applied, the analytical model requires key reservoir and fracture parameters to be drastically modified in order to match the historical production data. Results will also show that these history-matched models may not be predictive for future production, providing highly pessimistic EUR’s in most real-world scenarios. For the cases presented, analytical models under-predict EUR’s by 10-20% despite good history matches of two-year production. For all cases presented, an efficient simulation workflow for probabilistic forecasting of brown fields was applied. This workflow provided multiple history-matched models that were constrained by historical production data.