Disclosed are an improved method and device for calibrating the depth of an optical fibre in a well. The method includes acquiring borehole seismic wave field data based on an optical fibre acoustic wave sensor; determining first arrival time information based on the borehole seismic wave field data; determining a downgoing wave first arrival amplitude based on the first arrival time information and the borehole seismic wave field data; determining an optical fibre amplitude feature point based on the downgoing wave first arrival amplitude; determining a wellhead initial position and a receiving point spacing of the optical fibre in the well based on the optical fibre amplitude feature point and logging curve feature points; and determining depth calibration information of the optical fibre in the well based on the wellhead initial position and the receiving point spacing.

The present application provides a seismic travel time tomographic inversion method based on two-point ray tracing comprising: collecting seismic data including direct wave travel time and reflected wave travel time; establishing an initial one-dimensional continuously layered model having continuously a varying intraformational velocity; representing a ray parameter p by a variable q, representing a source-receiver distance X by a function X=f(q) of the variable q, solving the function X=f(q) using a Newton iteration method; calculating a theoretical direct wave travel time and reflected wave travel time according to the ray parameter p; comparing the calculated theoretical arrival time with actual arrival time, using an optimal algorithm to adjust velocity parameters of the initial one-dimensional continuously layered model, until a difference between the theoretical direct wave travel time and reflected wave travel time and the actual direct wave travel time and reflected wave travel time complies with a predetermined error standard.

A system and method for hydraulic fracturing and monitoring microseismic events related to hydraulic fracturing are described. One method describes a method of hydraulic fracturing gas production comprising drilling and casing a gas production well with a horizontal section within a formation layer, perforating the horizontal section of the well at a known location, and monitoring the resulting seismic waves using an array of geophones. Using the seismic waves resulting from the perforation shot, subsequent microseismic events may be located using a root mean square velocity and average velocity and without the use of a depth velocity model.

A method is described for full waveform inversion using a b-spline projection that produces an earth model that can be used for seismic imaging. The method may be executed by a computer system.

A method for analyzing acoustic/elastic waves to determine subsurface structure of the earth includes receiving a plurality of observations of a seismic acoustic/elastic wave-field from a plurality of sensors; generating a plurality of Bernstein grids of differing resolutions; calculating a data misfit of the plurality of observations with respect to an initial subsurface structure model defined in terms of conic combinations of Bernstein polynomials on a lowest resolution Bernstein grid, and mapping the data misfit from the Bernstein grid onto a Lagrangian grid; updating the subsurface structure model by minimizing the data misfit between the plurality of observations and observations obtained by a simulation; increasing resolution of the Bernstein grid and recomputing the updated subsurface structure model on the increased resolution Bernstein grid; and mapping the recomputed subsurface structure model onto the Lagrangian grid.

Production capability of cased hole perforations in a cased completed well lined with a casing in an under-pressured gas producing reservoir is tested. A sonde of a dipole shear or array sonic (full waveform) acoustic well logging tool is moved in a well bore of the cased completed well in the reservoir across a depth interval of interest, which covers cased hole perforations zones in the reservoir. The well logging sonde has in it an acoustic energy source and acoustic energy receivers. Responses are logged at depth intervals of interest to the transit of Stoneley waves along the casing walls from the acoustic energy source to the acoustic energy receivers. Measures of characteristics (e.g., travel time and attenuation) of the Stoneley wave are obtained. The responses are then processed to indicate production capability of the cased hole perforations.

A method is disclosed that includes obtaining a seismic data set from a seismic survey conducted over a subterranean region of interest and discretizing the seismic data set into a plurality of sub-regions each with a local traveltime operator. The method further includes dividing the plurality of sub-regions into a first subset and a second subset and calculating the local traveltime operator for each sub-region of the first subset using a conventional method and determining the local traveltime operator for each sub-region of the second subset using a convergent POCS method based on the local traveltime operators for the sub-regions of the first subset. The method further includes determining an enhanced seismic dataset by performing non-linear beamforming using the local traveltime operator for each sub-region of the plurality of sub-regions and determining a location of a hydrocarbon reservoir in the subterranean region of interest using the enhanced seismic data set.

A technique facilitates improved data acquisition and analysis with downhole tools and systems. The downhole tools and systems utilize arrays of sensing devices which are deployed in arrangements for improved sensing of data related to environmental features and/or tool parameters of tools located downhole in a borehole. For example, the tools and sensing systems may be operated to effectively sense and store characteristics related to components of downhole tools as well as formation parameters at, for example, elevated temperatures and pressures. Similarly, chemicals and chemical properties of interest in oilfield exploration and development also may be detected, measured and stored for analysis.

Systems and methods for deghosting seismic data using migration of sparse arrays are disclosed. The methods may include obtaining input seismic data, the input seismic data including a first set of seismic data recorded by a first set of seismic receivers located at a first depth, and a second set of seismic data recorded by a second set of seismic receivers located at a second depth. The method may further include migrating the first set of seismic data to an image grid, and migrating the second set of seismic data to the image grid. Additionally, the method may further include calculating a ghost wave based on the first and second sets of migrated seismic data, and deghosting the first set of migrated seismic data by removing the ghost wave.

A method including obtaining, by a computer processor, a sonic waveform for each of a plurality of source and receiver positions along a borehole, and a sonic wave propagation velocity of a target event for the plurality of positions. Further, performing, a linear moveout correction on the sonic waveforms based on the velocity and stacking the linear moveout corrected waveforms to generate a stacked waveform at the plurality of positions. The method further includes determining an arrival-time of the target event on the stacked waveforms based on an extremum of a first objective and predicting a candidate arrival-time of the target event for the sonic waveform at the plurality positions based on the arrival-time of the target event on the stacked waveforms, and the sonic velocity. The method still further includes determining an arrival-time for the target event on the sonic waveform at the plurality positions within the borehole based on the candidate arrival-time of the target event and an extremum of a second objective function.