Methods and seismic shot generation and data collection systems configured to determine a monotonically increased velocity v*(z) from a monotonically increased velocity model by requiring the monotonically increased velocity v*(z) to be nearest to a refraction velocity v(z) determined for an estimated depth z and to be characterized by a positive slope such that the refraction velocity v(z) increases with depth, and to generate a subsurface image based on the estimated depth z and the determined monotonically increased velocity v*(z).

Embodiments may be directed to marine geophysical surveying and associated methods. At least one embodiment may be directed to incorporation of a lock mechanism in a sensor streamer that interlocks the outer jacket with one or more of the spacers to prevent relative rotation between the outer jacket. An embodiment may provide a sensor streamer that includes an outer jacket, a plurality of spacers, and a locking mechanism. The outer jacket may be elongated in an axial direction and comprise an outer jacket surface and an inner jacket surface. The plurality of spacers may be positioned in the outer jacket at spaced apart locations in the axial direction, wherein each of the plurality of spacers comprises a spacer body having an outer spacer surface. The locking mechanism may interlock the outer jacket with at least one of the plurality of spacers.

Disclosed are methods, systems, and computer-readable medium to perform operations including: spectrally decomposing seismic data associated with a target subsurface area into a plurality of iso-frequency volumes; selecting a low-frequency volume and a high-frequency volume from the plurality of iso-frequency volumes; dividing the low-frequency volume by the high-frequency volume to generate a frequency ratio volume for the target subsurface area; establishing a time-depth relationship in the target subsurface area; extracting, based on the time-depth relationship and the frequency ratio volume, an iso-frequency ratio log in the target subsurface area; and using the iso-frequency ratio log to identify a subsurface gas reservoir in the target subsurface area.

Methods and seismic shot generation and data collection systems configured to determine a monotonically increased velocity v*(z) from a monotonically increased velocity model by requiring the monotonically increased velocity v*(z) to be nearest to a refraction velocity v(z) determined for an estimated depth z and to be characterized by a positive slope such that the refraction velocity v(z) increases with depth, and to generate a subsurface image based on the estimated depth z and the determined monotonically increased velocity v*(z).

The present invention discloses a microseismic monitoring system, which includes at least a microseismic sensor, a push rod set at both ends of the microseismic sensor through the first connecting mechanism for sending the microseismic sensor into a monitoring hole, a guide mechanism installed on the push rod for guiding the microseismic sensor into the monitoring hole, and a microseismic monitoring computer connecting with the microseismic sensor signal. The microseismic sensor is reusable. The first connecting mechanism can make the push rod swing relative to the microseismic sensor. The guide mechanism is a three-roller guide mechanism. The present invention can satisfy the need of monitoring different locations in monitoring holes with large depths for multiple microseismic sensors, and solve problems of effective contact coupling between the microseismic sensors and monitoring holes, which improves the accuracy of microseismic monitoring and reduces the cost of a microseismic monitoring system.

Method for reconstructing seismic data. The method includes receiving at a computing device an input seismic data set d related to plural shots emitted by one or more seismic sources; receiving at the computing device a positional data set d.sub.p relating to recording locations of the receivers that recorded the input seismic data set d; receiving at the computing device a receiver target location; calculating an adjusted receiver location based on (i) the positional data set d.sub.p and (ii) the receiver target location, wherein the adjusted receiver location substantially coincides with a receiver location from the positional data set d.sub.p; calculating reconstructed seismic data d.sub.r at the adjusted receiver location using the input seismic data set d and the positional data set d.sub.p; and correcting the seismic wave paths from the one or more seismic sources to the receivers based on the reconstructed seismic data d.sub.r.

A seismic sensor for a seismic survey includes an outer housing having a central axis, a first end, and a second end opposite the first end. The first end comprises a portion made of a clear material configured to transmit light having a frequency in the visible or infrared range of the electromagnetic spectrum. In addition, the seismic sensor includes a proof mass moveably disposed in the outer housing. The proof mass includes a power source. Further, the seismic sensor includes a sensor element disposed in the outer housing and configured to detect the movement of the outer housing relative to the proof mass. Still further, the seismic sensor includes electronic circuitry coupled to the sensor element and the power source. The seismic sensor also includes a light guide assembly having a first end adjacent the clear portion of the first end of the outer housing and a second end adjacent the electronic circuitry. The light guide assembly is configured to transmit light in an axial direction between the first end of the light guide assembly the clear section and to transmit light in a non-axial direction between the second end of the light guide assembly and the electronic circuitry.

Embodiments may be directed to marine geophysical surveying and associated methods. At least one embodiment may be directed to incorporation of a lock mechanism in a sensor streamer that interlocks the outer jacket with one or more of the spacers to prevent relative rotation between the outer jacket. An embodiment may provide a sensor streamer that includes an outer jacket, a plurality of spacers, and a locking mechanism. The outer jacket may be elongated in an axial direction and comprise an outer jacket surface and an inner jacket surface. The plurality of spacers may be positioned in the outer jacket at spaced apart locations in the axial direction, wherein each of the plurality of spacers comprises a spacer body having an outer spacer surface. The locking mechanism may interlock the outer jacket with at least one of the plurality of spacers.

An optical fiber sensing system is disclosed for sensing presence of an acoustic event such as acoustic waves or vibration along a path. The sensing system includes means for producing a plurality of pulses of coherent light. The system includes a first optical sensing fiber for receiving at least a first portion of the pulses of coherent light and adapted to be positioned along the path, the first optical sensing fiber producing first backscattered light in response to receiving said pulses of coherent light. The system includes a second optical sensing fiber for receiving at least a second portion of said pulses of coherent light pulses and adapted to be positioned along said path, the second optical sensing fiber producing second backscattered light in response to receiving said pulses of coherent light. The system includes first receiving means arranged to receive the first backscattered light for producing a first optical signal in response to a perturbation in the first backscattered light, and second receiving means arranged to receive the second backscattered light for producing a second optical signal in response to a perturbation in the second backscattered light. The system further includes means for generating a resultant signal in response to the first and/or the second optical signal wherein the resultant signal is indicative of presence of the acoustic event along the path. A method of sensing presence of an acoustic event such as acoustic waves or vibration along a path is also disclosed.

The present invention discloses a microseismic monitoring system, which includes at least a microseismic sensor, a push rod set at both ends of the microseismic sensor through the first connecting mechanism for sending the microseismic sensor into a monitoring hole, a guide mechanism installed on the push rod for guiding the microseismic sensor into the monitoring hole, and a microseismic monitoring computer connecting with the microseismic sensor signal. The microseismic sensor is reusable. The first connecting mechanism can make the push rod swing relative to the microseismic sensor. The guide mechanism is a three-roller guide mechanism. The present invention can satisfy the need of monitoring different locations in monitoring holes with large depths for multiple microseismic sensors, and solve problems of effective contact coupling between the microseismic sensors and monitoring holes, which improves the accuracy of microseismic monitoring and reduces the cost of a microseismic monitoring system.