A pressure wave is generated within a first well extending into a subterranean formation. A pressure response associated with the pressure wave is detected from a second well extending into the formation. Information is then determined, based on the pressure response in the second well, wherein the information is associated with at least one of the formation and a fracture connected to at least one of the first well and the second well.

Monitoring and diagnosing completion during hydraulic fracturing operations provides insights into the fracture geometry, inter-well frac hits and connectivity. Conventional monitoring methods (microseismic, borehole gauges, tracers, etc.) can provide a range of information about the stimulated rock volume but may often be limited in detail or clouded by uncertainty. Utilization of DAS as a fracture monitoring tool is growing, however most of the applications have been limited to acoustic frequency bands of the DAS recorded signal. In this paper, we demonstrate some examples of using the low-frequency band of Distributed Acoustic Sensing (DAS) signal to constrain hydraulic fracture geometry. DAS data were acquired in both offset horizontal and vertical monitor wells. In horizontal wells, DAS data records formation strain perturbation due to fracture propagation. Events like fracture opening and closing, stress shadow creation and relaxation, ball seat and plug isolation can be clearly identified. In vertical wells, DAS response agrees well with co-located pressure and temperature gauges, and illuminates the vertical extent of hydraulic fractures. DAS data in the low-frequency band is a powerful attribute to monitor small strain and temperature perturbation in or near the monitor wells. With different fibered monitor well design, the far-field fracture length, height, width, and density can be accurately measured using cross-well DAS observations.

A method for correcting a fracture model of a reservoir includes receiving a seismic signal from seismic events due to a plurality of stimulated reservoir stages to provide detected seismic event information and estimating a number of undetected seismic events and a magnitude for each of the undetected seismic events to provide undetected seismic event information for each stage. The detected seismic event information and the undetected seismic event information provide corrected seismic event information for each stage. The method further includes calculating a scaling factor for each stage using a scalar property of the corresponding stage and a reference stage scalar property, applying the scaling factor for each stage to the corrected seismic event information to provide scaled seismic event information for each stage, and correcting the fracture model with the scaled seismic event information for each stage to provide a corrected fracture model.

Microseismic-event data can be corrected (e.g., to reduce or eliminate bias). For example, a first distribution of microseismic events that occurred in a first area of a subterranean formation can be determined. The first distribution can be used as a reference distribution. A second distribution of microseismic events that occurred in a second area of the subterranean formation can also be determined. The second area of the subterranean formation can be farther from an observation well than the first area. The second distribution can be corrected by including, in the second distribution, microseismic events that have characteristics tailored for reducing a difference between the second distribution and the first distribution.

A method for characterizing a subsurface fluid reservoir includes inducing a pressure wave in a first well traversing the subsurface reservoir. A pressure wave in at least a second well traversing the subsurface reservoir is detected. The detected pressure wave results from conversion of a tube wave generated by the pressure wave in the first well into guided waves. The pressure wave in the at least a second well is generated by conversion of the guided waves arriving at the at least a second well. A guided (K) wave travel time from the first well to the at least a second well is determined and a physical property of the subsurface fluid reservoir is determined from the K-wave travel time.

Methods are provided for tracking carbon dioxide (CO.sub.2) migration in a hydrocarbon-bearing reservoir located under a cap rock in a formation. In one embodiment, at least one seismic source and a plurality of receivers are located in spaced boreholes in the formation with the sources and receivers located near or at the reservoir so that direct paths from the sources to the receivers extend through the reservoir. CO.sub.2 is injected from the borehole containing the seismic sources into the reservoir, and the sources are activated multiple times over days and seismic signals are detected at the receivers. From the detected signals, time-lapse travel delay of direct arrivals of the signals are found and are used to track CO.sub.2 in the reservoir as a function of time. In another embodiment, the sources and receivers are located above the reservoir, and reflected waves are utilized to track the CO.sub.2.

A survey method includes generating a first amplitude modulation signal by amplitude-modulating a carrier wave repeating the same pattern at a predetermined cycle in each of a plurality of vibrators with a modulation signal whose cycle is 1/m times the predetermined period and is different for each of the vibrators, transmitting the seismic wave based on the first amplitude modulation signal, generating a second amplitude modulation signal in one or more receivers, the second amplitude modulation signal being identical to the first amplitude modulation signal generated by any one of the seismic vibrators, generating a reception signal in each of the one or more receivers by receiving a synthetic seismic wave in which the seismic waves generated by the seismic vibrators are synthesized, calculating a correlation value between the reception signal and the second amplitude modulation signal, and analyzing characteristics of the medium on the basis of the correlation value.

Monitoring and diagnosing completion during hydraulic fracturing operations provides insights into the fracture geometry, inter-well frac hits and connectivity. Conventional monitoring methods (microseismic, borehole gauges, tracers, etc.) can provide a range of information about the stimulated rock volume but may often be limited in detail or clouded by uncertainty. Utilization of DAS as a fracture monitoring tool is growing, however most of the applications have been limited to acoustic frequency bands of the DAS recorded signal. In this paper, we demonstrate some examples of using the low-frequency band of Distributed Acoustic Sensing (DAS) signal to constrain hydraulic fracture geometry. DAS data were acquired in both offset horizontal and vertical monitor wells. In horizontal wells, DAS data records formation strain perturbation due to fracture propagation. Events like fracture opening and closing, stress shadow creation and relaxation, ball seat and plug isolation can be clearly identified. In vertical wells, DAS response agrees well with co-located pressure and temperature gauges, and illuminates the vertical extent of hydraulic fractures. DAS data in the low-frequency band is a powerful attribute to monitor small strain and temperature perturbation in or near the monitor wells. With different fibered monitor well design, the far-field fracture length, height, width, and density can be accurately measured using cross-well DAS observations.

Some aspects of what is described here relate to seismic profiling techniques. A seismic excitation is generated at a seismic source location in a directional section of a fracture treatment injection wellbore in a subterranean region. A seismic response associated with the seismic excitation is detected at a seismic sensor location in the directional section of the fracture treatment injection wellbore. The seismic response includes a reflection from the subterranean region. A fracture treatment applied through the fracture treatment injection wellbore is analyzed based on the reflection.

Embodiments disclosed herein describe methods and processes to perform dynamic imaging of naturally occurring or artificially stimulated serpentinization processes in subsurface rock units. The methods herein use a combination of electrical, electromagnetic, magnetic, and passive seismic data measured in and around the rock units undergoing the serpentinization process. Serpentinization is a chemical reaction between iron-rich minerals such as olivine and water under suitable temperature conditions, and the process naturally or artificially generates hydrogen gas that can be collected and used as a fuel. The serpentinization degree of the rock is an indicator of the potential hydrogen generation ability of the specific rock.