Identifying Fault Activation in Unconventional Reservoirs in Real Time Using Microseismic Monitoring

Abstract

Identification of fault related microseismicity in hydraulic fracture treatments is crucial to understanding how treatments are stimulating a reservoir. Evaluating b values in combination with event source mechanism provides a reliable and intuitive method for separating fault related microseismic events from standard fracture related events. Typically this analysis is conducted after a treatment is complete and serves as a diagnostic tool to provide possible explanations for reduced production or designing future treatments on nearby wells to avoid an identified fault feature. Being able to identify such features in real time allows the operator to not only identify faults but to stop treatment and avoid these features all together saving time and materials that would otherwise be pumped into an area that doesn't contribute to the overall stimulation of the reservoir, and could reduce production on the well. When evaluating b-values in real time, a technique that can identify faulting early in the initiation of fault stimulation is crucial for preserving the most resources during treatment.

The Environmental Costs and Benefits of Fracking

“…This increased pressure allows the elastic energy stored in rock to be released more easily, much like removing weight from a box makes it easier to slide along the floor (103,104). Injecting fracturing fluids or wastewater underground can intersect a fault zone directly (105) or transmit a pulse in fluid pressure that reduces the effective stress on a fault. Felt seismicity attributed to hydraulic fracturing has been documented in only a handful of cases, none of the earthquakes greater than magnitude (M w ) 4.0 (104).…”

A Validation Assessment of Microseismic Monitoring

“…For typical earthquakes associated with tectonism (not volcanism), the b-value is typically near unity. It has been proposed (e.g., Cipolla et al 20011b;, Kratz et al 2012) that the b-values from hydraulic fractures might be much greater than unity (typically near 2) and that this behavior is likely a result of difference in stress drop or other features of the hydraulic fracture compared to an earthquake.…”

“…For surface applications, faults have been identified by a combination of factors ranging from magnitudes, orientations, b-values, and focal planes (Kratz et al 2012(Kratz et al , 2015Snelling et al 2013).…”

A Case for Microseismic Surface Arrays in Texas?

“…Microseismic monitoring of hydraulic fracture jobs has proven to be a useful tool for the oil and gas industry. Not only has it allowed for improved treatment designs in real-time, but it can also be used to help guide the optimization of well placements, spacing and completions (Fisher et al, 2002;Maxwell, S.C. et al, 2002;Fisher et al, 2004;Cipolla et al, 2005;Mayerhofer et al, 2005;Warpinski et al,2005;Duncan and Lakings, 2006;Waters et al, 2006;Daniels et al, 2007;Vulgamore et al, 2007;Barker, 2009;Waters et al, 2009;Urbancic et al, 2011;Wessels et al, 2011;Baig, 2012;Kratz et al, 2012). It provides additional constraints for the calibration of fracture and reservoir modeling, such as fault interactions, geomechanics and attributes, and stimulation interactions.…”

“…This measurement can be viewed as a "beach-ball", a three-dimensional visualization that represents the different types of rock slippage, dipslip, strike-slip, and volume changes, depending on the orientation of the beach-ball in three-dimensional space (Sykes, 1967;Dziewonski and Woodhouse, 1983;Walter and Brune, 1993 9DYU\þXN ). The events' corresponding fault/fracture plane orientations can then be calculated and used to classify the fracture network (Brune, 1970;Walter and Brune, 1993;Rutledge et al, 2004;Baig and Urbancic, 2010;Downie et al, 2010;Warpinski and Du, 2010;Cipolla et al, 2011;Wessels et al, 2011;Williams-Stroud et al, 2012;Kratz et al, 2012).…”