Beyond the dots in the box: Microseismicity-constrained fracture models for reservoir simulation

Abstract

Monitoring of induced microseismic events usually results in locations for these events and a geometrical interpretation of these 'dots in the box'. In this study we show how additional information obtained from observed microseismic events, namely the source mechanisms, were used to generate a discrete fracture network. Using the wide aperture of a surface star-like array (FracStar®) allows inversion for both shear and non-shear source mechanisms. Both volumetric and shear-only source mechanism inversion was carried out on microseismic events from the treatment of a shale gas reservoir in the continental US. During the same hydraulic fracture stimulation treatment, both dip-slip and reverse faulting sources were active in this reservoir. The source mechanisms revealed fracture orientations more accurately than could be inferred from microseismic event locations alone. The activity associated with different mechanisms is interpreted as indicating reactivation of existing fractures in the rock, as well as suggesting generation of new fractures. Failure analysis using source mechanisms on individual events allows an integrated understanding of the complex fracture interactions taking place in the reservoir, and also provides a more complete understanding of the stress conditions in the reservoir during the treatment. Fracture orientations, locations, and failure mechanisms are translated into discrete fracture network (DFN) models that can be used to verify the extent and character of the fractures created or reactivated during the fracture treatment, and may ultimately be used to generate fracture flow properties for reservoir simulation.

A Marchenko equation for acoustic inverse source problems

“…3,4 By retrieving the original wavefields throughout the subsurface, these sources can be localized and monitored, based on which the underlying source mechanisms can be revealed. 5 The ISP is also relevant in underwater acoustics 6 and ultrasonic non-destructive testing. 7 Although the methodology that is being discussed in this paper can be applied to any ISP, we pay special attention to Photo-Acoustic (PA) imaging, an emerging biomedical modality.…”

Fast GPU-Based Seismogram Simulation From Microseismic Events in Marine Environments Using Heterogeneous Velocity Models

“…This helps physical modelling of cascaded growth of faults in the subsurface. These events are also plotted as a function of both their strength and the origin time in Figure 19 where the event sizes are proportional to their amplitudes and the colors represent differences in the respective origin times [51].…”

A review of stimulated reservoir volume characterization for multiple fractured horizontal well in unconventional reservoirs

“…This is more accurate when multiple orientations of existing fracture were reactivated. The orientations of fracture failure planes can be characterized by interpreting the source mechanism (Eisner et al, 2010). The studies of different researchers indicate a correlation between the SRV that emits seismic signal while stimulation and the ultimate recovery factor of the well (Fisher et al, 2004;Mayerhofer et al, 2006).…”

“…To develop the DFN, fracture planes are located at microseismic events, and the aperture and are of the fractures are evaluated based on the magnitude of the events (Kanamori, 1977). The fracture orientation can be determined by analyzing source attributes characterization (Williams-Stroud and Eisner, 2010). The DFN modeled from analyzing focal mechanism also need to be calibrated with production data to reduce the degree of uncertainty.…”