The exploitation of unconventional reservoirs requires hydraulic fracturing treatments, aimed at enhancing reservoir rock permeability through the re-activation of existing natural micro-fractures and the generation of new fractures in the near-wellbore area. Microseismic Monitoring (MSM), which consists of acoustic recording of the induced fracturing events, has nowadays become a common approach for real-time tracking of the fracture network evolution.
The present work is based on the analysis of microseismic and production data coming from three multi-fractured wells drilled in a shale gas reservoir. Information derived from MSM is integrated with the Advanced Production Analysis (APA) results, to assess if the MSM interpretations are able to provide preliminary indications about the production behavior of the fractured wells before start-up. The spatial localization of microseismic events and their moment magnitude are derived from the interpretation of the seismic signals recorded by geophones during hydraulic fracturing. Data analysis, based on the cross-plot of the event moment magnitude versus the distance between the event and the nearest geophone, allows the determination of the spatial range bias, i.e. the effect for which the level of the recorded magnitudes depends on the distance from the geophones. A novel methodology was developed to correct the spatial range bias by combing a Gaussian function and the Gutenberg-Richter law for fitting the Frequency Magnitude Distribution. After the correction, microseismic data from different wells and frac stages can be directly compared and used for the evaluation of the Stimulation Efficiency (SE) and the Stimulated Reservoir Volume (SRV).
APA is used to analyze production data from the three selected wells in order to characterize both the fractured system and the reservoir.
Even if the results obtained from MSM and APA techniques are often at different scales and not quantitatively comparable, it is still possible to obtain useful information from their integration. APA confirms, indeed, the interference between wells production due to the overlap of different SRV, as initially estimated from MSM interpretation. Thus, the results of the developed methodology allow to improve well placement, stimulation operation design and field development strategies.