Imaging Seismic Deformation Induced by Hydraulic Fracture Complexity

Maxwell, Shawn; Waltman, Charles; Warpinski, N.R.; Mayerhofer, Michael; Boroumand, Neda

doi:10.2523/102801-ms

Cited by 23 publications

(12 citation statements)

References 8 publications

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“…Urbancic and Maxwell (2002) looked at the apparent stress drop of events to differentiate between shear and non-shear components of deformation, which they suggest could allow for mapping of the most permeable pathways in the reservoir. Trying to incorporate fracture density into SRV analysis, Maxwell et al (2006) combined total seismic moment with SRV to generate a combined stimulation metric in a Barnett shale well. This combined metric was found to correlate well with production in cases where production did not correlate well with SRV alone.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Fracturing, Microseismic Magnitudes, and Stress Evolution in the Barnett Shale, Texas, USA

2011

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We present new techniques to analyze the effectiveness of hydraulic fracturing for stimulating production in shale gas reservoirs. The case study we have analyzed involves five parallel horizontal wells in the Barnett shale with 51 frac stages. To investigate the numbers, sizes and types of microearthquakes initiated during each frac stage, we created Gutenberg-Richter-type magnitude distribution plots to see if the size of events follows the characteristic scaling relationship found in natural earthquakes. We found that slickwater fracturing does generate a log-linear distribution of microearthquakes, but that it creates proportionally more small events than natural earthquake sources. Finding considerable variability in the generation of microearthquakes, we have used the magnitude analysis as a proxy for the "robustness" of the stimulation of a given stage. We have found that the conventionally fractured well and the two alternately fractured wells ("zipperfracs") were more effective than the simultaneously fractured wells ("simulfracs") in generating microearthquakes.We also found that the later stages of fracturing a given well were more successful in generating microearthquakes than the early stages. This increase in microearthquake activity in the latter frac stages corresponded with an increase in the instantaneous shut-in pressure (ISIP). The net ISIP increase was most pronounced in the simulfrac wells and least pronounced in the zipperfrac wells. We have attempted to model this increase as a cumulative "stress shadow" using an elastic crack-opening model. However, even the maximum reasonable propped fracture aperture causes a stress increase that is less than what was measured in the wells. Since the fracturing of the simulfrac wells took only half the time of the fracturing of the zipperfrac wells, we believe that poroelastic effects associated with time-dependent leak-off is controlling the rate of ISIP escalation and the increase in microseismic creation. We are incorporating poroelasticity in the model to fully integrate stress evolution and permeable volume creation.

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Section: Introductionmentioning

confidence: 99%

Hydraulic Fracturing, Microseismic Magnitudes, and Stress Evolution in the Barnett Shale, Texas, USA

2011

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“…Fig. 2 shows a plot of the magnitude of the microseismic events (Maxwell et al, 2006) versus distance to the monitoring array. The microseismic events recorded during the Well C fracture treatments are larger in magnitude than those recorded while treating the other two wells (up to about magnitude -0.4), and the anomalously large magnitude suggests a possible interaction with pre-existing faults.…”

Section: Case Studymentioning

confidence: 99%

“…6). Seismic moment is a robust measure of the source strength of the microseismicity (Maxwell et al, 2006).The logarithm of seismic moment is used to compute the moment magnitude displays in Fig. 2.…”

Section: Fault Activationmentioning

confidence: 99%

Understanding Hydraulic Fracture Variability through Integrating Microseismicity and Seismic Reservoir Characterization

Maxwell

Pope

Cipolla

et al. 2011

North American Unconventional Gas Conference and Exhibition

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Microseismic measurements were integrated with seismic reservoir characterization and injection data to investigate variability in the hydraulic fracture response between three horizontal wells in the Montney shale in NE British Columbia, Canada. When wells were close enough, hydraulic fractures were found to interact with pre-existing faults, which acted as a barrier to fracture growth, and resulted in relatively large-magnitude microseismicity. The increased level of microseismic deformation and corresponding fault-related source characteristics correlated with the presence of a pre-existing fault identified by edge detection/ant tracking algorithms applied to seismic reflection data. In cases where the wells were far from pre-existing faults simple, planar hydraulic fractures were observed, although there was a tendency to grow towards regions of low Poisson's ratio based on amplitude versus offset inversion of the seismic reflection data. The tendency for the hydraulic fractures to be asymmetric and grow preferentially towards the low Poisson's ratio region is attributed to material property changes and associated lower stresses in these regions. Integrating microseismic interpretations and fracture treatment data with enhanced reservoir characterization has been used to rethink well placement and completion designs, resulting in improved well performance.

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“…It is in this case that microseismic can be used directly to determine permeability. In the petroleum industry however, methods to determine permeability directly from microseismic are formative in nature 19 , but have been developed in more detail in the geothermal industry 20 .…”

Section: Seismic Based Reservoir Characterization (Sbrc)mentioning

confidence: 99%

Shear Dilation Diagnostics: A New Approach for Evaluating Tight Gas Stimulation Treatments

Chipperfield¹,

Wong²,

Warner³

et al. 2007

Proceedings of SPE Hydraulic Fracturing Technology Conference

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMany tight gas reservoirs require fracture stimulation to achieve commercial outcomes. These reservoirs can often be characterized geologically and geomechanically by high deviatoric stresses and hard, naturally fractured rock. Stimulation treatments in such reservoirs may create complex fracture networks from a combination of shear and tensile failures. Water fracs can be used where shear failure is anticipated to dominate. However, in these environments few practical modeling tools exist to determine [1] the level of permeability enhancement, [2] the degree of permeability retainment during drawdown and [3] the Stimulated Rock Volume (SRV). This paper seeks to provide the engineer with a suite of tools capable of achieving these goals. This paper presents a dual porosity, pressure dependent permeability reservoir simulation model that was devised to honor shear failure mechanisms [also called shear dilation] using basic geological characterization. The assumptions of this model and the pragmatic selection of first order effects are discussed. Using the results of this simulation model, three families of diagnostic tools are presented.The first category is that of Treatment Diagnostics (TD) which include bottomhole pressure evaluation, injectivity and fall-off analysis. The second approach is called Seismic Based Reservoir Characterization (SBRC), which uses the microseismic to determine the SRV as well as provide estimates of the initial and stimulated fracture network properties. The third category is Post Treatment Diagnostics (PTD), which incorporates the evaluation of pressure drawdown characteristics.Finally, this paper compares these individual approaches and provides a workflow to evaluate data on future wells.

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Imaging Seismic Deformation Induced by Hydraulic Fracture Complexity

Cited by 23 publications

References 8 publications

Hydraulic Fracturing, Microseismic Magnitudes, and Stress Evolution in the Barnett Shale, Texas, USA

Hydraulic Fracturing, Microseismic Magnitudes, and Stress Evolution in the Barnett Shale, Texas, USA

Understanding Hydraulic Fracture Variability through Integrating Microseismicity and Seismic Reservoir Characterization

Shear Dilation Diagnostics: A New Approach for Evaluating Tight Gas Stimulation Treatments

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