scholarly journals In situ measurement of velocity-stress sensitivity using crosswell continuous active-source seismic monitoring

Geophysics ◽  
2017 ◽  
Vol 82 (5) ◽  
pp. D319-D326 ◽  
Author(s):  
Pierpaolo Marchesini ◽  
Jonathan B. Ajo-Franklin ◽  
Thomas M. Daley
Keyword(s):  
Seismic Velocity ◽  
Fluid Pressure ◽  
Seismic Monitoring ◽  
Stress Sensitivity ◽  
Pore Fluid ◽  
Field Scale ◽  
Pore Fluid Pressure ◽  
Active Source ◽  
Injection Zone

The ability to characterize time-varying reservoir properties, such as the state of stress, has fundamental implications in subsurface engineering, relevant to geologic sequestration of [Formula: see text]. Stress variation, here in the form of changes in pore fluid pressure, is one factor known to affect seismic velocity. Induced variations in velocity have been used in seismic studies to determine and monitor changes in the stress state. Previous studies conducted to determine velocity-stress sensitivity at reservoir conditions rely primarily on laboratory measurements of core samples or theoretical relationships. We have developed a novel field-scale experiment designed to study the in situ relationship between pore-fluid pressure and seismic velocity using a crosswell continuous active-source seismic monitoring (CASSM) system. At the Cranfield, Mississippi, [Formula: see text] sequestration field site, we actively monitored seismic response for five days with a temporal resolution of 5 min; the target was a 26 m thick injection zone at approximately 3.2 km depth in a fluvial sandstone formation (lower Tuscaloosa Formation). The variation of pore fluid pressure was obtained during discrete events of fluid withdrawal from one of the two wells and monitored with downhole pressure sensors. The results indicate a correlation between decreasing CASSM time delay (i.e., velocity change for a raypath in the reservoir) and periods of reduced fluid pore pressure. The correlation is interpreted as the velocity-stress sensitivity measured in the reservoir. This observation is consistent with published laboratory studies documenting a velocity ([Formula: see text]) increase with an effective stress increase. A traveltime change ([Formula: see text]) of 0.036 ms is measured as the consequence of a change in pressure of approximately 2.55 MPa ([Formula: see text]). For [Formula: see text] total traveltime, the velocity-stress sensitivity is [Formula: see text]. The overall results suggest that CASSM measurements represent a valid technique for in situ determination of velocity-stress sensitivity in field-scale monitoring studies.

scholarly journals Monitoring transient changes within overpressured regions of subduction zones using ambient seismic noise

2016 ◽  
Vol 2 (1) ◽  
pp. e1501289 ◽  
Author(s):  
Esteban J. Chaves ◽  
Susan Y. Schwartz
Keyword(s):  
Seismic Noise ◽  
Subduction Zones ◽  
Seismic Velocity ◽  
Fluid Pressure ◽  
Pore Fluid ◽  
Ambient Seismic Noise ◽  
Pore Fluid Pressure ◽  
Near Surface ◽  
Velocity Reduction ◽  
Pressurized Fluids

In subduction zones, elevated pore fluid pressure, generally linked to metamorphic dehydration reactions, has a profound influence on the mechanical behavior of the plate interface and forearc crust through its control on effective stress. We use seismic noise–based monitoring to characterize seismic velocity variations following the 2012 Nicoya Peninsula, Costa Rica earthquake [Mw(moment magnitude) 7.6] that we attribute to the presence of pressurized pore fluids. Our study reveals a strong velocity reduction (~0.6%) in a region where previous work identified high forearc pore fluid pressure. The depth of this velocity reduction is constrained to be below 5 km and therefore not the result of near-surface damage due to strong ground motions; rather, we posit that it is caused by fracturing of the fluid-pressurized weakened crust due to dynamic stresses. Although pressurized fluids have been implicated in causing coseismic velocity reductions beneath the Japanese volcanic arc, this is the first report of a similar phenomenon in a subduction zone setting. It demonstrates the potential to identify pressurized fluids in subduction zones using temporal variations of seismic velocity inferred from ambient seismic noise correlations.

scholarly journals Strain Hardening in Salt—Results of the SALMON Experiment

1990 ◽  
Vol 112 (2) ◽  
pp. 145-148 ◽  
Author(s):  
L. A. Glenn
Keyword(s):  
Yield Strength ◽  
Strain Hardening ◽  
Nuclear Explosion ◽  
Fluid Pressure ◽  
Salt Dome ◽  
Pore Fluid ◽  
Laboratory Scale ◽  
Experimental Results ◽  
Pore Fluid Pressure

SALMON was a nuclear explosion in the Tatum salt dome, near Hattiesburg, Mississippi, that took place on October 22, 1964. Computational attempts to simulate the experimental results had been largely unsuccessful. Recent calculations suggest that the reason is that the salt yield strength is extremely sensitive to strain hardening. The hardening effect had not been observed in laboratory-scale measurements, which were not made at small enough strain levels and may not have been representative of in-situ pore-fluid pressure.

scholarly journals Correction to: Stress and pore fluid pressure control of seismicity rate changes following the 2016 Kumamoto earthquake, Japan

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Kodai Nakagomi ◽  
Toshiko Terakawa ◽  
Satoshi Matsumoto ◽  
Shinichiro Horikawa
Keyword(s):  
Fluid Pressure ◽  
Pressure Control ◽  
Pore Fluid ◽  
2016 Kumamoto Earthquake ◽  
Pore Fluid Pressure ◽  
Seismicity Rate ◽  
Kumamoto Earthquake ◽  
The 2016 Kumamoto Earthquake ◽  
Seismicity Rate Changes

An amendment to this paper has been published and can be accessed via the original article.

scholarly journals Fracture-induced pore fluid pressure weakening and dehydration of serpentinite

2019 ◽  
Vol 767 ◽  
pp. 228168 ◽  
Author(s):  
Melodie E French ◽  
Greg Hirth ◽  
Keishi Okazaki
Keyword(s):  
Fluid Pressure ◽  
Pore Fluid ◽  
Pore Fluid Pressure

scholarly journals Control of pore fluid pressure diffusion on fault failure mode: Insights from the 2009 L'Aquila seismic sequence

2012 ◽  
Vol 117 (B5) ◽  
pp. n/a-n/a ◽  
Author(s):  
Luca Malagnini ◽  
Francesco Pio Lucente ◽  
Pasquale De Gori ◽  
Aybige Akinci ◽  
Irene Munafo'
Keyword(s):  
Failure Mode ◽  
Fluid Pressure ◽  
Pore Fluid ◽  
Seismic Sequence ◽  
Pore Fluid Pressure ◽  
Pressure Diffusion

Connections between subducted sediment, pore-fluid pressure, and earthquake behavior along the Alaska megathrust

Geology ◽  
2018 ◽  
Vol 46 (4) ◽  
pp. 299-302 ◽  
Author(s):  
Jiyao Li ◽  
Donna J. Shillington ◽  
Demian M. Saffer ◽  
Anne Bécel ◽  
Mladen R. Nedimović ◽  
...  
Keyword(s):  
Fluid Pressure ◽  
Pore Fluid ◽  
Pore Fluid Pressure ◽  
Subducted Sediment
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