Fracture network engineering for hydraulic fracturing

Abstract

Recent developments in both SRM and EMA technologies are described using case studies of the techniques applied to hydrofracture stimulations. We identify and discuss some future developmental challenges these technologies face, including their further integration and validation so as to provide more efficient and robust application of the FNE approach.

The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

“…In the geothermal domain, such projects constitute expensive experiments and thus are relatively few in number, whereas, in the oil and gas domain, where hydro-fracture operations are frequent and routine, the data tend to be proprietary. Nevertheless, some notable datasets have been acquired for deep brine injection projects (Ake et al, 2005;Block et al, 2015), deep scientific drilling projects such as the German KTB project (Zoback and Harjes, 1997;Emmermann and Lauterjung, 1997;Jost et al, 1998;Baisch and Harjes, 2003), and hydraulic fracturing for oil and gas production enhancement (Warpinski, 2009;Das and Zoback, 2011;Dusseault et al, 2011;Pettitt et al, 2011;Vermylen and Zoback, 2011;Boroumand and Eaton, 2012;Bao and Eaton, 2016) and during the stimulation of deep geothermal boreholes (Parker, 1989;Jupe et al, 1992;Cornet and Scotti, 1993;Tezuka and Niitsuma, 2000;Asanuma et al, 2005;Evans et al, 2005a;Häring et al, 2008;Brown et al, 2012;Baisch et al, 2015). Welldocumented hydraulic stimulation datasets generally include microseismic observations as well as injection pressures and flow rates and, occasionally, tilt monitoring (Evans, 1983;Warpinski and Teufel, 1997).…”

“…Man-made earthquakes are not a new phenomenon (Healy et al, 1968;McGarr, 1976;Pine et al, 1987;Nicholson and Wesson, 1951;Gupta, 1992). However, the occurrence of several well-reported felt events near major population centers has served to focus attention on the problem (Giardini, 2009;Ellsworth, 2013;Davies et al, 2013;Huw et al, 2014;Bao and Eaton, 2016).…”

“…Pearson (1981) and Phillips et al (1997) analyzed microseismicity generated during the stimulation of the 2930 m deep "large Phase 1" and the 3460 m deep Phase 2 reservoirs, respectively, at the Fenton Hill EGS site, New Mexico. Batchelor et al (1983) summarize microseismicity observed during the stimulation injections into the Phase 2a and 2b reservoirs at Rosemanowes in Cornwall, UK.…”

“…Managing induced seismic hazard also requires considering the design of reservoir attributes such as size, system impedance and heat exchanger properties that control system longevity (e.g., Gischig et al, 2014). Currently, few case studies consider both seismicity and the related changes that occurred in the reservoir (e.g., Evans et al, 2005a), and relatively few studies even report both permeability changes or well injectivity (e.g., Häring et al, 2008;Evans et al, 2005b;Kaieda et al, 2005;Petty et al, 2013). More work is needed to quantitatively link the spatial, temporal or magnitude distribution of seismicity with the thermo-hydraulicmechanical properties of the rock mass under stimulation conditions.…”

“…(1) Upscaling results to the field scale is affected by large uncertainties (Gale, 1993). Although there is evidence that the roughness of fresh fracture surfaces obeys well-defined scaling over many orders of magnitude (Power and Tullis, 1991;Schmittbuhl et al, 1995), complications arise in upscaling the aperture distribution and hence permeability of two semi-mated rough surfaces due to the effects of damage and wear of the asperities during shearing and gouge formation (Amitrano and Schmittbuhl, 2002;Vogler et al, 2016). (2) Laboratory tests are typically performed on single fractures in relatively homogeneous materials and uniform stress conditions, which makes upscaling to structures with multiple fractures such as fracture zones challenging.…”