A new decline curve reproducing the response of a SRV-Bounded analytical model in unconventional reservoirs is presented. It reproduces the three successive flow regimes of this model: transient linear, transition and pseudosteady state. By construction, this decline curve is fully consistent with the predictions of the physical SRV-bounded model.
For consistency, the decline curve is obtained by numerically integrating a base function reproducing the succession of the expected flow regimes. Three parameters are sufficient to fully describe the curve. Despite an integration in the material balance time domain, the matching of rate and / or cumulative production data and the production forecast are directly performed in the real time domain. When available the pressure history can be used to convolve the decline curve. Once the decline curve is matched, the three decline parameters are used to infer three relationships between the physical model parameters: number of fractures, half-length, completion length and permeability.
The main characteristics of the SRV-bounded model are reviewed, followed by the calculation steps leading to the decline curve. We show how to estimate physical parameters from the parameters of the decline curve. Results from the decline curve and the SRV-bounded model are in total agreement. Application examples are shown. When pseudo-steady state is not reached by the data, the decline curve can be fitted to get the most conservative estimate.
The proposed decline curve attempts to bridge the gap between empirical decline parameters and physical models.
Decline curve analysis (DCA) using the empirical Arps' exponential and hyperbolic relations has historically been the standard approach for conventional reserves estimations and production forecasts (Arps, 1945). Traditional DCA is based on three main assumptions (Houzé et al, 2015):
Operating conditions and field development do not change during the producing life of the well
The well is producing with a constant bottomhole flowing pressure
There is a boundary-dominated flow regime and reservoir depletion was established
