Cotton Valley hydraulic fracture imaging project: Feasibility of determining fracture behavior using microseismic event locations and source parameters

Urbancic, Ted; Zinno, R.J.

doi:10.1190/1.1820653

Cited by 11 publications

(5 citation statements)

References 4 publications

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“…Patterns of S-to P-wave energy ratios (Es/Ep) were previously interpreted as an indicator of a non-shear or volumetric component of failure systematically varying along the Cotton Valley treatment lengths (Urbancic and Zinno, 1998;Rutledge and Urbancic, 1999;Mayerhofer et al, 2000). The same data, displayed as amplitude ratios in Figure 12, can instead be attributed to the radiation patterns of two similar, double-couple, shear mechanisms occurring uniformly over the treatment length.…”

Section: Discussionmentioning

confidence: 89%

Hydraulic stimulation of natural fractures as revealed by induced microearthquakes, Carthage Cotton Valley gas field, east Texas

2003

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We have produced a high-resolution microseismic image of a hydraulic fracture stimulation in the Carthage Cotton Valley gas field of east Texas. Gas is produced from multiple, low-permeability sands within an interbedded sand-shale sequence. We improved the precision of microseismic event locations 4-fold over initial locations by manually repicking the waveforms in a spatial sequence, allowing us to visually correlate waveforms of adjacent sources. The new locations show vertical containment within individual, targeted sands, suggesting little or no hydraulic communication between the discrete perforation intervals simultaneously treated within an 80-m section. Treatment lengths inferred from event locations are about 200 m greater at the shallow perforation intervals than at the deeper intervals. The highest quality locations indicate fracture zone widths as narrow as 6 m. Similarity of adjacent-source waveforms, along with systematic changes of phase amplitude ratios and polarities, indicate fairly uniform focal mechanisms (fracture plane orientation and sense of slip) over the treatment length. Composite focal mechanisms indicate both left-and right-lateral strike-slip faulting along near-vertical fractures that strike subparallel to maximum horizontal stress (S Hmax). The focal mechanisms and event locations are consistent with activation of the reservoir's prevalent natural fractures, fractures that are isolated within individual sands and trend subparallel to expected hydraulic fracture orientation (S Hmax direction). Shear activation of these fractures indicates a stronger correlation of induced seismicity with low-impedance flow paths than is normally found or assumed during injection stimulation.

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Section: Discussionmentioning

confidence: 89%

Hydraulic stimulation of natural fractures as revealed by induced microearthquakes, Carthage Cotton Valley gas field, east Texas

2003

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“…Therefore, to capture a realistic range of source frequencies, we simulate three source frequencies at 40 Hz, 150 Hz and 300 Hz. Based on Urbancic and Zinno (1998), we define the microseismic moment magnitude to be 4.4 × 10 10 dyne.cm for all source frequencies. We keep the size of the seismic moment constant in all simulations to facilitate waveform comparisons but note here that the source moment magnitude would be smaller for higher dominant frequency sources and larger for lower dominant frequency sources (e.g., see Izutani and Kanamori 2001, Fig .…”

Section: Microseismic Sourcementioning

confidence: 99%

Influence of a velocity model and source frequency on microseismic waveforms: some implications for microseismic locations

Usher

Angus

Verdon

2012

Geophysical Prospecting

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In this paper, we examine the influence of a velocity model and microseismic source frequency on microseismic waveforms and event locations. Finite‐difference waveform synthetics are generated based on the Cotton Valley hydraulic fracture experiment, where we vary the vertical heterogeneity of the velocity models as well as the microseismic source frequencies. We find that differences between plausible velocity models lead to changes in arrival times of approximately 0.0035 seconds for P‐waves and 0.0085 seconds for S‐waves. Based on the average P‐ and S‐wave velocities, the difference in the P‐ and S‐wave traveltimes is equivalent to approximately 20 m in location difference. Significant increases in the waveform coda develop with increasing model heterogeneity and increasing source frequency. The presence of signal noise as well as other sources of error (e.g., uncertainty in geophone location) will likely lead to further increase in uncertainty in location error estimates. Thus we note that location error due to incorrect velocity models cannot be ignored.

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“…In recent years, it has been suggested that passive seismic monitoring offers an opportunity to image the dimensions of hydraulic fractures by evaluating the distribution of microearthquake locations and their source characteristics (e.g., Urbancic, 1998Urbancic, , 1999 in both space and time (e.g., Maxwell et al, 2000). In this paper, we carry out a general assessment of the microseismic response for stimulations monitored over the past few years in the U.S..…”

Section: Introductionmentioning

confidence: 99%

Assessing the effectiveness of hydraulic fractures with microseismicity

Urbancic¹,

Maxwell²,

Zinno³

2003

SEG Technical Program Expanded Abstracts 2003

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Passive seismic imaging is used to map the development of hydraulic fractures in relatively non-fractured and naturally fractured reservoirs. The images obtained for multiple stimulations throughout the U.S. identified non-complex preferential fracture growth patterns with constrained permeability enhanced pathways, lithologically controlled symmetric and asymmetric hydraulic fractures, and complex fracture patterns associated with fluid-flow along pre-existing fault networks. In this paper, we examine these observations in the context of establishing effective field drainage through optimal well placement.

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Cotton Valley hydraulic fracture imaging project: Feasibility of determining fracture behavior using microseismic event locations and source parameters

Cited by 11 publications

References 4 publications

Hydraulic stimulation of natural fractures as revealed by induced microearthquakes, Carthage Cotton Valley gas field, east Texas

Hydraulic stimulation of natural fractures as revealed by induced microearthquakes, Carthage Cotton Valley gas field, east Texas

Influence of a velocity model and source frequency on microseismic waveforms: some implications for microseismic locations

Assessing the effectiveness of hydraulic fractures with microseismicity

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