A method for characterizing a hydraulic fracture in a subsurface formation includes inducing a pressure change in a borehole drilled through the subsurface formation. At least one of pressure and a time derivative of pressure is measured in the borehole for a selected length of time. At least one physical parameter of at least one fracture is determined using the measured pressure and/or the time derivative of pressure. A method for characterizing hydraulic fracturing rate uses microseismic event count measured through the borehole and its real-time implementation.

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 disclosure is directed to a method of utilizing an acoustic sensing cable, such as a fiber optic distributed acoustic sensing (DAS) cable, in a borehole to detect microseismic events and to generate three dimensional fracture plane parameters utilizing the detected events. Alternatively, the method can use various categorizations of microseismic data subsets to generate one or more potential fracture planes. Also disclosed is an apparatus utilizing a single acoustic sensing cable capable of detecting microseismic events and subsequently calculating fracture geometry parameters. Additionally disclosed is a system utilizing a processor to analyze collected microseismic data to generate one or more sets of fracture geometry parameters.

Disclosed are systems and methods for selecting modes and frequencies of interest in a slowness-frequency map of sonic logging information. These include measuring, by a sonic logging tool, sonic data within a borehole, determining a frequency range for a selected mode of the sonic data, determining a slowness range for the selected mode of the sonic data, applying the frequency range and the slowness range to the sonic data to select a subset of data from the sonic data, processing the selected subset of data.

Implementations described and claimed herein provide systems and methods for isolation detection. In one implementation, an acoustic signal is obtained. The acoustic signal is captured at a set of acoustic receivers deployed in a structure in a subterranean surface. A differential acoustic signal is produced from the acoustic signal captured at the set of acoustic receivers. A symmetry within a portion of the structure is determined based on a value of the differential acoustic signal. At least one isolation region is detected within the structure based on the symmetry.

Implementations described and claimed herein provide systems and methods for isolation detection. In one implementation, an axial acoustic signal is obtained. The axial acoustic signal is captured using an axial sensor deployed in a structure in a subterranean surface. The axial acoustic signal is separated into a first wave region and a second wave region by applying velocity filtering. An axial symmetry of a portion of the structure is determined based on at least one of the first wave region or the second wave region.

Apparatus and methods are described, including identifying an arrival of a first arriving S-wave emitted from a seismic source at an array (120) of sensors (129, 140) in real-time, by continuously analyzing waveforms received by the sensors (120, 140), and continuously monitoring back-azimuth and slowness data within the detected waveforms. Arrival of a first arriving P-wave emitted from the seismic source at the array (120) of sensors (129, 140) is identified, based upon the back-azimuth and slowness data. Slowness and back azimuth of the first arriving P-wave are determined, by analyzing a waveform of the P-wave, and based upon the determined slowness of the first arriving P-wave, the arrival of the first arriving S-wave at the array (120) of sensors (129, 140) is identified. Other applications are also described.

The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems, for determining first-break (FB) points. One computer-implemented method includes: selecting, by a hardware processor, potential first-break (PFB) points based on seismic data obtained by plurality of seismic receivers in a geological location; determining, by the hardware processor, a first plurality of FB lines based on the PFB points; selecting, by the hardware processor, a first FB line among the plurality of FB lines; filtering, by the hardware processor, the PFB points based on the first FB line; determining, by the hardware processor, a second plurality of FB lines based on the filtered PFB points; selecting, by the hardware processor, a second FB line among the second plurality of FB lines; and determining, by the hardware processor, FB points based on the second FB line.

Implementations described and claimed herein provide systems and methods for isolation detection. In one implementation, a radial acoustic log is obtained. The radial acoustic log is captured using a radial sensor of an acoustic logging tool deployed within a first structure. The first structure disposed within a second structure in a subterranean environment. A radial symmetry is determined using the radial acoustic log. An eccentricity of the first structure relative to the second structure is determined based on the radial symmetry.

A seismic warning system comprises: a plurality of sensors, each sensor sensitive to a physical phenomenon associated with seismic events and operative to output an electronic signal representative of the sensed physical phenomenon; a data acquisition unit communicatively coupled to receive the electronic signal from each of the plurality of sensors, the data acquisition unit comprising a processor configured to estimate characteristics of a seismic event based on the electronic signal associated with a P-wave from each of the plurality of sensors; and a local device communicatively coupled to the data acquisition unit. The plurality of sensors, the data acquisition unit and the local device are local to one another.