Hydraulic fracturing operations in unconventional reservoirs are typically monitored using geophones located either at the surface or in the adjacent wellbores. A new approach to record hydraulic stimulations uses fiber-optic distributed acoustic sensing (DAS). A fiber-optic cable was installed in a treatment well in the Meramec formation to monitor the hydraulic fracture stimulation of an unconventional reservoir. A variety of physical effects, such as temperature, strain, and microseismicity are measured and correlated with the treatment program during hydraulic fracturing of the well containing the fiber and also an adjacent well. The analysis of this DAS data set demonstrates that current fiber-optic technology provides enough sensitivity to detect a considerable number of microseismic events and that these events can be integrated with temperature and strain measurements for comprehensive hydraulic fracture monitoring.

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Hydraulic fracturing operations in unconventional reservoirs are monitored using distributed fiber-optic sensing through which physical effects such as temperature, strain, and microseismic activity can be measured. When combined with treatment curves and other reservoir information, these measurements give engineers more data to understand the effectiveness of a treatment program and make future reservoir management decisions. Distributed fiber-optic data are acquired within a borehole that is actively being fractured and is subsequently used as an observation well for treatments of a neighboring well. The large-aperture and finely sampled data acquisition provides a variety of measurements at different resolution scales as changes are induced in the reservoir. Distributed acoustic sensing microseismic events are observed with magnitudes above −2. The spatial distribution of events, up to 500 m from the observation well, allows us to estimate diffusivity and fracturing trends for nearby treatment wells. Microseismic events acquired using a standard three-component borehole tool provide insight into the type of events that can be observed only on one system or simultaneously on both systems. We correlate very low frequency (well below 1 Hz) strain-front behavior with the onset of microseismic events, as they are triggered by pore pressure and fracturing progress throughout the reservoir.

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