A retrofit valve shutoff device is provided that comprises a coupling key for coupling with an actuator of a shutoff valve on a fluid supply line, an inertial measurement unit for generating one or more signals in response to arrival of seismic waves, a motor for rotating the coupling key and the actuator of the shutoff valve, and a processing unit for receiving the one or more signals from the inertial measurement unit, analyzing the received signals to determine whether to close the shutoff valve, and sending a signal to the motor to rotate the coupling key and the actuator of the shutoff valve to close the shutoff valve based on the analysis of the received signals.

A method of analyzing measured microseismic events obtained from monitoring induced hydraulic fracturing of underground geological formations, the method involving (a) postulate a geomechanical model for the region bounding the microseismic events, the model including the parameters vertical stress, reservoir pore pressure, minimum horizontal stress and the orthogonal horizontal stress, (b) select a microseismic event and (c) for the selected microseismic event assume an associated slippage plane with a postulated orientation, (d) apply the geomechanical model to the postulated orientation to determine the resulting shear stress and normal stress applied to the postulated orientation, (e) repeat steps (c) and (d) to produce a number of postulated slippage planes each with their own shear stress and normal stress attributable to them, (f) select the fracture plane having the highest ratio of shear stress to normal stress as being the fracture plane most likely to be representative of a real slippage plane consistent with the geomechanical model, (g) repeat steps (b) to (f) to analyze a number of microseismic events to generate a slippage plane most likely to be representative of a real slippage plane for each microseismic event is provided.

A method for wavefield separation of sonic data is provided. The method comprises estimating direct phases of waveforms of sonic data observed with two or more sensors by using cross-correlation of waveform traces at adjacent sensor locations, removing the direct phases from the observed waveforms, and extracting event signals from the waveforms after removing the direct phases.

A system and method and non-transitory computer readable medium method for filtering signals representative of microseismic events with an infinite impulse response (IIR) Wiener filter which precludes the need for statistics or prior knowledge of the signal of interest. The second-order statistics of the noise and the noisy data are extracted from the recorded data only. The criteria used to optimize the filter impulse response is the minimization of the mean square error. The IIR Wiener filter was tested on synthetic and field data sets and found to be effective in denoising microseismic data with low SNR (2 dB).

The invention discloses a method for exploring passive source seismic frequency resonance, which includes the following steps: Step 1: collecting, with a detector, a response signal of underground medium to form seismic time series data; Step 2, transforming the data collected in step 1 into frequency domain data, via Fourier transformation; Step 3, performing frequency domain superposition on the data at a same detection point processed through step 2, to form frequency domain amplitude superposition data; Step 4, converting, through a correction with a standard well parameter, frequency domain data processed through step 3 into depth data; Step 5, processing the data obtained in step 4 to obtain imaging data Image.sub.(d), where the imaging data Image.sub.(d) is apparent wave impedance ratio or apparent wave impedance changing as depth. The method can perform spatial and attribute imaging of the underground medium by using the seismic wave resonance principle.

A method of detecting an event by: obtaining a first sample data set; determining a frequency domain feature(s) of the first sample data set over a first time period; determining a first threshold for the a frequency domain feature(s) using the first sample data set: determining that the frequency domain feature(s) matches the first threshold; determining the presence of an event during the first time period based on determining that the frequency domain feature(s) matches the first threshold; obtaining a second sample data set; determining a frequency domain feature(s) of the second sample data set over a second time period; determining a second threshold for the frequency domain feature(s) using the second sample data set; determining that the frequency domain feature(s) matches the second threshold; and determining the presence of the event during the second time period based on determining that the frequency domain feature(s) matches the second threshold.

A method of identifying inflow locations along a wellbore includes obtaining an acoustic signal from a sensor within the wellbore, determining a plurality of frequency domain features from the acoustic signal, and identifying, using a plurality of fluid flow models, a presence of at least one of a gas phase inflow, an aqueous phase inflow, or a hydrocarbon liquid phase inflow at one or more fluid flow locations. The acoustic signal includes acoustic samples across a portion of a depth of the wellbore, and the plurality of frequency domain features are obtained across a plurality of depth intervals within the portion of the depth of the wellbore. Each fluid flow model of the plurality of fluid inflow models uses one or more frequency domain features of the plurality of the frequency domain features, and at least two of the plurality of fluid flow models are different.

A method of identifying events includes obtaining an acoustic signal from a sensor, determining one or more frequency domain features from the acoustic signal, providing the one or more frequency domain features as inputs to a plurality of event detection models, and determining the presence of one or more events using the plurality of event detection models. The one or more frequency domain features are obtained across a frequency range of the acoustic signal, and at least two of the plurality of event detection models are different.

A system (400) for processing microseismic data comprises an array (330) of seismic sensors (331, 332) at known locations, means (331, 332; 410) for enhancing SNR in a seismic signal output from a seismic sensor, means (331, 332; 410) for detecting a microseismic event in the seismic signal and inverting means (410) for adapting a rock physical model (255) to microseismic data that are acquired at least partially from the seismic signal representing a microseismic event. The rock physical model comprises a set of spatial volume elements mapping a set of physical volume elements (320) within a volume (300) to be monitored, wherein each spatial volume element comprises attributes for the position and extension of the physical volume element (320), a velocity and an attenuation. Data of various kinds, e.g. pore geometry, and from numerous sources, e.g. laboratory measurements, can be incorporated in the rock physical model (255).

A computer-implemented method for seismic event localization includes: generating, with at least one processor, a vectorized snapshot matrix representing wave propagation data at a series of snapshots in time for a subterranean formation; computing a reduced orthonormal column basis matrix based on the vectorized snapshot matrix; constructing a reduced order wave propagation model based on the reduced orthonormal column basis matrix; receiving seismic data collected from a plurality of receivers at the subterranean formation; generating a time-domain coefficient matrix based on back propagation of the received seismic data and the reduced order wave propagation model; reconstructing time-reversed wavefield data based on the time-domain coefficient vector; and generating signals for outputting wavefield or seismic event location information based on the time-reversed wavefield data.