Two examples from the SPE data repository will be used to illustrate a method for forecasting production in unconventional reservoirs using initial production data (first 1-2 months of production).
Analysis of accurately measured hourly initial production data indicates a flow regime sequence of sub-radial flow (slope <0.4), followed by a 1st boundary (slope ~1) and then sub-linear flow (slope > 0.5) on Rate Normalized Pressure vs. Material Balance Time plots.
These flow regime sequences are applied in a workflow to determine the fracture half-length, permeability, and the number of fractures from initial production data.
Examples from the SPE data repository show that the parameters determined from the initial production period can be used to seed models to forecast production.
Additional examples validate the workflow’s application for evaluating completion effectiveness by correlating the total fracture half-length from the analysis with the created fracture surface area.
This presentation illustrates the significance of high frequency/high quality initial production data. The reservoir transients that indicate that sub-radial flow and a unit slope precede sub-linear flow are often masked by low resolution daily data and hourly data with measurement errors.
When only the sub-linear flow regime and second boundary are observed and analyzed, an independent (and often unavailable) estimate of permeability is required to determine the fracture half-length and permeability and number of fractures. In contrast, the identification of a sub-radial flow regime and a first boundary allow the fracture half-length and transmissibility to be determined uniquely.