Various technologies have traditionally been used to monitor and describe hydraulic fractures from different perspectives. This work demonstrates the value of data integration for hydraulic fracture characterization when multiple data resources are available. The Hydraulic Fracturing Test Site 2 (HFTS 2) is a hydraulic fracturing research project in the Delaware Basin with multiple surveillance techniques including fiber optics sensing, microseismic, pressure/temperature gauges, etc. We integrated the multidisciplinary data from the HFTS-2 to characterize hydraulic fractures. The integrated data revealed interesting fracture propagation features including layering, vertical propagation affected by pore pressure gradient, and different microseismic activities due to difference in-situ conditions. These findings can be insightful for understanding hydraulic fracture propagation. The comparison among multiple surveillance data also helps us to evaluate the roles of various surveillance technologies and provides us experience to make informative decisions depending on different monitoring objectives.
Successful hydraulic stimulation is essential for unconventional resource development. However, the characterization of hydraulic fractures is extremely challenging. Multiple surveillance technologies, such as microseismic (Maxwell, 2014; Grechka and Heigl, 2017), fiber optics (Jin and Roy, 2017), pressure (Spicer and Coenen, 2018), and temperature (Sierra, et al., 2008), have been developed to monitor fracture growth with varying degrees of success.
As a widely used hydraulic fracturing surveillance technology, traditional microseismic monitoring uses surface, shallow buried, or down hole geophones to detect and record small earthquakes associated with hydraulic stimulation (Maxwell, 2014). The extent and occurrence of microseismic events are used to characterize the growth of hydraulic fractures. The microseismic source parameters provide information on the fracture mechanism and stress states around hydraulic fractures. However, the challenges are the not-well-understood mechanism of microseismic occurrence and the potentially location uncertainties of microseismic events (Zhang, et al., 2017).
Fiber optics strain sensing have been used for hydraulic fracturing monitoring from different perspectives. Distributed Acoustic Sensing (DAS) can be used for microseismic data acquisition (Karrenbach, et al., 2017). It provides wide spatial coverage and high spatial sampling rate with adequate signal-to-noise ratio. This facilitates the identification various seismic phases, which can be used to improve microseismic event location and fracture characterization (Lellouch, et al., 2020). However, DAS measures the strain only along the axial direction. This makes the microseismic event location using DAS signal from a single well ambiguous and moment tensor inversion very challenging.
