In order to monitor the subsoil of the earth under a target zone, seismic waves coming from an identified mobile noise source are recorded by means of at least one pair of sensors disposed on either side of the target zone, time periods are selected corresponding to the alignments of the pairs of sensors with the noise source, a seismogram of the target zone is reconstructed by interferometry based on the recorded seismic waves and on the selected time periods and an image of the subsoil of the target zone is generated using the seismogram.

The calibration of fracture models for naturally fractured reservoirs using fracture properties from X-ray micro-computed tomography (X-ray MicroCT). A core plug is obtained from a subsurface naturally fractured hydrocarbon reservoir, and a fracture property such as fracture porosity and a fracture effective permeability of the hydrocarbon reservoir are determined. A natural fracture model is generated using reservoir parameters and fluid flow paths, and fracture properties such as fracture porosity and a fracture effective permeability are determined from the natural fracture model. The fracture properties of the natural fracture model are calibrated using the fracture properties from the X-ray MicroCT analysis of the core plug.

A stimulation includes an injection of a volume of fluid into a formation. A method includes obtaining a mechanical earth model of the formation, modeling a hydraulic fracture growth pattern in the formation from a stimulation of the formation, determining an increase in pressure in the formation resulting from the stimulation, and predicting whether a seismic event will occur in the formation based on the increase in pressure.

A method can include receiving acoustic emission data for acoustic emissions originating in a formation, performing a moment tensor analysis of the data, thereby yielding acoustic emission source parameters, determining at least one acoustic emission source parameter angle having a highest number of associated acoustic emission events, and calculating an in situ stress parameter, based on the acoustic emission source parameter angle. A system can include multiple sensors that sense acoustic emissions originating in a formation, and a computer including a computer readable medium having instructions that cause a processor to perform a moment tensor analysis of the data and yield acoustic emission source parameters, determine at least one acoustic emission source parameter angle having a highest number of associated acoustic emission events, and calculate an in situ stress parameter, based on the acoustic emission source parameter angle.

Methods and systems for monitoring operation integrity during hydrocarbon production or fluid injection operations by receiving microseismic data; processing the data to obtain data panels corresponding to microseismic data measured over a time interval; determining, with a neural network analysis, whether any of the data panels includes a noise event or a non-noise event; calculating, for each data panel including a non-noise event, trigger values for data traces corresponding to sensor receivers of the microseismic monitoring system; selecting, as a triggered data panel, at least one data panel that satisfies triggering criteria; selecting, as a non-trivial data panel, at least one triggered data panel that satisfies spectral density criteria; calculating a value for each of at least two event attributes of the event; determining an event score based on the event attribute values; and classifying the event into at least one event category based on the event score.

A method for estimating a fluid pressure required to stimulate a subsurface formation includes using seismic signals detected by a plurality of seismic sensors disposed proximate the subsurface formation. Spatial positions and times of origin (hypocenters) of each of a plurality of microseismic events induced by pumping fluid into the subsurface formation are estimated. Magnitudes and directions of principal stresses are estimated from the hypocenters and from amplitude and phase of the detected seismic signals for each of the microseismic events. Shear and normal stresses of induced fractures are from the estimated principal stresses. A fluid pressure required to cause formation failure on each fracture is estimated using the estimated shear and normal stresses.

A method of characterizing a subterranean geologic formation's response to hydraulic fracturing is presented. The method includes acquiring data representing a plurality of seismic events caused by hydraulic fracturing of the subterranean geologic formation, determining, by at least one electronic processor, a plurality of seismic event moment magnitudes for respective seismic events in the plurality of seismic events, estimating, by at least one electronic processor, a first parameter representing a negative slope of a line relating seismic event frequency to seismic event magnitude for at least some of the plurality of seismic events, estimating, by at least one electronic processor, a second parameter representing an axis intercept of the line, and characterizing the subterranean geologic formation based at least in part on the first parameter and the second parameter

A system (100) for monitoring a subterranean structure comprises an array (10) with n acoustic sensors capable of detecting P-waves and/or S-waves from the subterranean structure and a central controller (120) for receiving a signal (X) from the sensors. The system further comprises a lookup table (20) comprising a pre-computed travel time curve (24) expressed as relative arrival times of a signal from a location (L.sub.m) to each of the sensors (1-n); a comparison unit for comparing the received signal (X) with the pre-computed travel time curve (24), and means for raising an alarm if the received signal (X) matches the precomputed travel time curve (24). Preferably, the alarm is raised if a computed semblance value (26, 27) exceeds a predefined threshold. The system may monitor several locations (L.sub.m) in parallel using a fraction of the computer resources and time required by prior art techniques.

A downhole monitoring system and method that includes a sensor system with a sensor array with a number of sensors and a hub. Data measured by the sensors is processed by the hub and wirelessly communicated to a smart node. The sensor system may be mounted in the annulus formed between a borehole wall and an exterior surface of a well casing. The sensors may be configured to monitor the formation for microseismic events generated during hydraulic fracturing. The fracture growth and propagation may be monitored using the data obtained by the sensors. The data may facilitate real time control of the hydraulic fracturing operation.

Methods and systems for monitoring operation integrity during hydrocarbon production or fluid injection operations by receiving microseismic data; processing the microseismic data to obtain a plurality of data panels corresponding to microseismic data measured over a predetermined time interval; calculating, for each data panel, trigger values for data traces corresponding to sensor receivers of the microseismic monitoring system; selecting, as a triggered data panel, at least one data panel that satisfies predetermined triggering criteria; selecting, as a non-trivial data panel, at least one triggered data panel that satisfies spectral density criteria; calculating a value for each of at least two event attributes of a plurality of event attributes of the event; determining an event score based on the values of the plurality of event attributes; and classifying the event into at least one event category of a plurality of event categories based on the event score.