Patent Description:
A seismic data acquisition system can acquire seismic data relating to subsurface features, such as lithological formations or fluid layers that may indicate the presence of hydrocarbons, minerals or other elements. An acoustic signal can penetrate the surface of the earth. The acoustic signal can reflect or refract off of subsurface lithological formations. The reflected or refracted acoustic signals can be acquired, analyzed, and interpreted to indicate physical characteristics of, for example, the lithological formations such as the presence of hydrocarbons. Document <NPL>, discloses a system to perform seismic imaging, comprising a data processing system comprising a propagation component, gating component, and wavefield combination component.

The present disclosure is directed to a system as defined in independent claim <NUM> and a method of seismic imaging as defined in independent claim <NUM>.

The present disclosure is directed to systems and methods of seismic imaging with a temporal decomposition imaging condition. Due to the large volume of seismic data, it can be computationally challenging to process the seismic data to generate high quality images without excessive noise. Systems and methods of the present solution are directed to a data processing system with an image processor configured with a time gating condition that allows for the efficient creation of angle gathers during migration of primary or multiple reflection. The improved image processor with the time gating condition can provide for significant computational speadups. For example, the improved image processor of the present solution can utilize as little as <NUM>% of the computational recourses compared to previous approaches that map each time sample of the image separately to the angle domain.

Shot-profile migration and reverse-time migration (RTM) can refer to methods for imaging prestack seismic data to produce <NUM>-D subsurface images. Shot-profile migration and reverse-time migration operate on common-source or common-receiver data ensembles and propagates two wavefields through a subsurface model: one forward in time and the other backward in time. The forward in time wavefield can be referred to as a downgoing wavefield or "D" wavefield. The backward in time wavefield can be referred to as an upgoing wavefield or "U" wavefield. The data processing system can combine the two wavefields with an imaging condition (IC) in order to produce subsurface images and image gathers. The seismic images and gathers have many uses, including subsurface geological interpretation and iterative seismic velocity model development.

Shot-profile migration can use the "correlation" IC, which can be applied in the temporal frequency domain. RTM can use the "zero-lag of the crosscorrelation" IC, which can be the time domain equivalent of the correlation IC. These two imaging conditions are Fourier transform pairs. Kirchhoff migration can refer to an imaging technique that uses an imaging condition that selects and sums all possible arrivals that could have reflected from an image point. These arrivals can be determined by travel times consistent with the velocity model. The imaging condition can be based on the existence of reflectors in the earth at places where the onset of the downgoing wave is time coincident with an upcoming wave.

Systems and methods of the present solution can provide a data processing system with an image processor that is configured with a time gate imaging condition. For example, the correlation IC can be
<MAT>
where I is the image, ω is temporal frequency, and the * represents complex conjugation. This can be used in shot profile migration. The time-domain equivalent can be the zero lag of the crosscorrelation IC
<MAT>
where t is time. This IC can be used in RTM.

The temporal decomposition IC can be:
<MAT>
where fn(x,y,z;t) is a general function of space and time that operates on the product DU and decomposes it into n = <NUM>, <NUM>,. , N components. In is the image formed from component n. If fn has the property that
<MAT>
then
<MAT>
and the original image can, in some implementations, be approximately recovered by summing the component images.

One example of the new "time gate" IC uses fn(t) = Wn(t), where Wn is a temporal window function for time gate n. In this case
<MAT>.

The indices n = <NUM>, <NUM>,. , N specify N time gates. Define the length of each time gate to be 2T and let tn be the time at the center of time gate n. The Wn(t) are nonzero for t in the range [tn- T, tn+ T]. Wn could resemble a boxcar, gaussian, cosine-squared or trapezoidal function, for example. Wn also can overlaps its neighbors Wn-<NUM> and Wn+<NUM> so as to smooth the transition between time gated images In-<NUM>, In and In+<NUM>. The data processing system can use other forms for Wn. The correlation and zero-lag of the crosscorrelation ICs output a <NUM>-D image, but the new time gate IC outputs a <NUM>-D image, with the extra dimension being the time gate index n. Summation over time gate should produce the complete image if the weight functions are designed appropriately. Wn could also vary spatially if desired. In this case the window function would be Wn(x,y,z;t).

The time gate IC may be used as is in RTM. It may be used in shot profile migration by inverse Fourier transforming the wavefields D and U from the frequency domain to the time domain at each depth level during imaging.

<FIG> illustrates a system to perform a seismic imaging in accordance with an implementation. The system <NUM> can include a data processing system <NUM>. The data processing system <NUM> can include one or more processors, memory, logic arrays, or other components or functionality depicted in <FIG>. The data processing system <NUM> can include or execute on one or more servers. The data processing system <NUM> can include one or more servers in a server farm, or distributed computing infrastructure, such as one or more servers forming a cloud computing infrastructure. The data processing system <NUM> can include at least one logic device such as a computing device <NUM> having one or more processors 810a-n.

The data processing system <NUM> can include, interface or otherwise communicate with at least one interface <NUM>. The data processing system <NUM> can include, interface or otherwise communicate with at least one database <NUM>. The data processing system <NUM> can include, interface or otherwise communicate with at least one image processor <NUM>. The image processor <NUM> can include, interface with or otherwise communicate with at least one propagation component <NUM>. The image processor <NUM> can include, interface with or otherwise communicate with at least one an gating component <NUM>. The image processor <NUM> can include, interface with or otherwise communicate with at least one wavefield combination component <NUM>. The image processor <NUM> can include, interface with or otherwise communicate with at least one inverse image generator component <NUM>.

The interface <NUM>, image processor <NUM>, propagation component <NUM>, gating component <NUM>, wavefield combination component <NUM>, or image generator component <NUM> can each include at least one processing unit or other logic device such as programmable logic array engine, or module configured to communicate with the database repository or database <NUM>. The interface <NUM>, database <NUM>, image processor <NUM>, propagation component <NUM>, gating component <NUM>, wavefield combination component <NUM>, or image generator component <NUM> can be separate components, a single component, or part of the data processing system <NUM>. The system <NUM> and its components, such as data processing system <NUM>, can include hardware elements, such as one or more processors, logic devices, or circuits.

The data processing system <NUM> can communicate with one or more seismic data sources <NUM> or computing devices <NUM> via network <NUM>. The network <NUM> can include computer networks such as the Internet, local, wide, metro, or other area networks, intranets, satellite networks, and other communication networks such as voice or data mobile telephone networks. The network <NUM> can be used to access information resources such as seismic data, parameters, functions, thresholds, or other data that can be used to perform time gating or improve the processing of seismic data to generate images with reduced aliasing or noise that can be displayed or rendered via one or more computing devices <NUM>, such as a laptop, desktop, tablet, digital assistant device, smart phone, or portable computers. For example, via the network <NUM> a user of the computing device <NUM> can access information or data provided by the data processing system <NUM>. The computing device <NUM> can be located proximate to the data processing system <NUM>, or be located remote from the data processing system <NUM>. For example, the data processing system <NUM> or computing device <NUM> can be located on a vessel <NUM>.

The data processing system <NUM> can include an interface <NUM> (or interface component) designed, configured, constructed, or operational to receive seismic data obtained via acoustic signals generated by at least one acoustic source and reflected from at least one subsurface lithologic formation. For example, an acoustic source device <NUM> depicted in <FIG> can generate an acoustic wave or signal that reflects from at least one subsurface lithologic formation beneath the seabed <NUM>, and is sensed or detected by seismic sensor devices <NUM>. The interface <NUM> can receive the seismic data via a wired or wireless communication, such as a direct wired link or through a wireless network or low energy wireless protocol. The interface <NUM> can include a hardware interface, software interface, wired interface, or wireless interface. The interface <NUM> can facilitate translating or formatting data from one format to another format. For example, the interface <NUM> can include an application programming interface that includes definitions for communicating between various components, such as software components. The interface <NUM> can communicate with one or more components of the data processing system <NUM>, network <NUM>, or computing device <NUM>.

The data processing system can receive the seismic data as ensembles of common-source or common-receiver data. The seismic data can include ensembles or sets of common-source or common-receive data.

The data processing system <NUM> can include an image processor <NUM> with propagation component <NUM> designed, constructed or operational to forward or backward propagate the seismic data. For example, the data processing system <NUM> can propagate the seismic data forward in time through a subsurface model to generate a first wavefield (e.g., a downgoing wavefield). The data processing system <NUM> can propagate the seismic data backward in time through the subsurface model to generate a second wavefield (e.g., an upgoing wavefield).

For example, <FIG> shows an illustration <NUM> with multiple shot points (SP) <NUM> on the surface of the aqueous medium, which corresponds to a depth of <NUM> meters. The shot points <NUM> can be offset from the seismic device <NUM> by approximately <NUM> meters, <NUM> meters, and <NUM> meters. The data processing system <NUM> can select data corresponding to the shot point <NUM> at <NUM> meters for processing. A seismic data acquisition device <NUM> can be located on the seabed, for example at a depth of <NUM> meters below the surface of the aqueous medium. Upgoing waves <NUM> refer to seismic energy that can arrive at the seafloor after being reflected off of a subsurface formation (e.g., a formation located at a depth of <NUM> meters below the surface of the aqueous medium, or <NUM> meters below the seafloor). The waves can refer to seismic energy from an acoustic signal propagated from one or more acoustic sources or shot points <NUM>. A downgoing wave <NUM> can refer to seismic energy that arrives directly at the seafloor from the shot point <NUM>, or seismic energy that arrives at the seafloor after a near-total (e.g., more than <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>%) internal reflection at the air-water interface (e.g., the surface of the aqueous medium at a depth of <NUM> meters). The downgoing waves <NUM> can be projected to a point, such as point <NUM>. The point <NUM> can indicate a focal point for a projection of the downgoing waves <NUM> when there is less than total reflection at the air-water interface.

The data processing system <NUM> can receive, generate or propagate the seismic data to obtain the first wavefield and the second wavefield. For example, the data processing system <NUM> may receive seismic data that includes the upgoing wavefield, and then use this data to generate the downgoing wavefield. The data processing system can receive seismic data comprising the first wavefield, and use the first wavefield to generate the second wavefield. The data processing system <NUM> can receive seismic data that includes the second wavefield, and then generate the first wavefield.

The downgoing wavefield can be represented as a function D(x, y, z; ω), and the upgoing wavefield can be represented as function U(x, y, z; ω), where x, y and z are position coordinates, and ω is temporal frequency. The upgoing and downgoing wavefield can be represented as functions in the time-domain as follows: D(x, y, z; t), and U(x, y, z; t).

The data processing system <NUM> can include an image processor <NUM> with a gating component <NUM> designed, constructed or operational to identify, generate or apply a gate or window or time gate imaging condition. The gate, window or time gating imaging condition can refer to a gating function or any other window function. For example, the gating function can be a function fn(x,y,z;t). The gating function can be applied to the product or combination of the downgoing and upgoing wavefield functions to decompose the product into components, such as n = <NUM>, <NUM>,.

The time gate imaging condition can include a temporal window function for each of a plurality of time gates. The plurality of time gates can each have a predetermined length. The temporal window function can include at least one of a boxcar, Gaussian, cosine-squared or trapezoidal function. The time gate imaging condition can be configured to smooth across a plurality of time gates.

Other examples of the time gate can be fn(t) = Wn(t), where Wn can be a temporal window function for the time gate n where Wn(t) are nonzero for t in the range [tn-T, tn+T]. Wn can represent a temporal window function for time gate n. Other window functions may be used for Wn, including, for example, a boxcar, gaussian, cosine-squared or trapezoidal function.

In some cases, the fn can represent a Matching Pursuit operator that decomposes the product DU into n components. Matching Pursuit can obtain a sparse representation of a time series in signal processing. Matching pursuit can refer to identifying the strongest event in time series, modeling it, and then subtracting this event. The matching pursuit process can include repeating this until all that is remaining is residual noise. Thefn can be functions of time fn(t) or space and time fn(x,y,z;t). An example of spatial variation could be the operator fn changing with depth z. This can also include the Wn for time gates.

The data processing system <NUM> can generate the gating function, or retrieve the gating function or values from database <NUM>. The data processing system <NUM> can use a preselected gating function. The data processing system <NUM> can select a gating function to apply based on a policy, rule, or indication. For example, the data processing system <NUM> can use a policy that indicates which gating function to use based on the type of seismic data, amount of seismic data, desired output, or quality of the seismic data. The data processing system <NUM> can select the gating function to use based on an instruction from an end user. The data processing system <NUM> can select a gating function to use based on an amount computational resources available (e.g., type of computing device such as desktop computer or laptop computer or mobile computing device, processor utilization, or memory utilization). The data processing system <NUM> can select the gating function to use to maximize the image quality, reduce noise in the image, or reduce processor utilization or memory utilization.

The data processing system <NUM> can include an image processor <NUM> with a wavefield combination component <NUM> designed, constructed or operational to combine the first wavefield with the second wavefield using the time gate imaging condition to produce subsurface images and image gathers. For example, the data processing system can combine the first and second wavefield based on the following equation: <MAT>
where fn(x,y,z;t) can be gating function in space and time that operates on the product DU and decomposes it into n = <NUM>, <NUM>,. , N components. The functions can be combined using a multiplication, dot product, convolution, addition, or other combination technique.

In another example, the wavefield combination component <NUM> can combine the wavefields using the gating function as follows:
<MAT>.

The data processing system <NUM> can include an image processor <NUM> with an image generator component <NUM> designed, constructed or operational to generate an image using the first and second wavefields and the time gating function as follows:
<MAT>
where fn(x,y,z;t) can be gating function in space and time that operates on the product DU and decomposes it into n = <NUM>, <NUM>,. , N components. In can be the image formed from component n. This can be referred to as the temporal decomposition or image generated from the temporal decomposition.

Another example image can be generated using fn(t) = Wn(t), where Wn is a temporal window function for time gate n, as follows:
<MAT>.

Here, the indices n = <NUM>, <NUM>,. , N specify N time gates. The length of each time gate can be 2T and tn can be the time at the center of time gate n. The Wn(t) are nonzero for t in the range [tn-T, tn+T]. Wn could resemble a boxcar, gaussian, cosine-squared or trapezoidal function, for example. Wn also can overlaps its neighbors Wn-<NUM> and Wn+<NUM> so as to smooth the transition between time gated images In-<NUM>, In and In+<NUM>. The correlation and zero-lag of the crosscorrelation ICs output a <NUM>-D image, but the new time gate IC outputs a <NUM>-D image, with the extra dimension being the time gate index n. The data processing system can perform a summation over time gate to produce the complete image based on the weight functions. Wn could also vary spatially if desired. In this case the window function would be Wn(x,y,z;t).

For example, If fn has the property that
<MAT>
then
<MAT>
and the original image can be approximately recovered by summing the component images.

The time gate IC may be used as is in RTM. It may be used in shot profile migration by inverse Fourier transforming the wavefields D and U from the frequency domain to the time domain at each depth level during imaging. The data processing system <NUM> to generate a <NUM>-dimensional image from the combination of the first wavefield with the second wavefield using the time gate imaging condition.

In the temporal frequency domain, the image can be generated as follows:
<MAT>
where I is the image, ω is temporal frequency, and the * represents complex conjugation. However, the correlation imaging condition without the time gating imaging condition may not facilitate mapping individual imaged events to the angle domain because it operates in the frequency domain.

Thus, images from the temporal decomposition IC using the time gating condition can be more efficient to generate (e.g., use significantly less computational resources) while providing more information to work with by decomposing seismic images I(x,y,z) into components In(x,y,z). In particular, the time gate IC produces n images generated from n time gate functions.

The data processing system <NUM> configured with the time gate IC method makes it possible to isolate and suppress certain types of undesirable noise events before summation over time gate to create I(x,y,z). Undesirable noises include (a) imaging artifacts and (b) "crosstalk" generated by simultaneous imaging of primary and/or multiple reflections. For example, the data processing system can generate Kirchhoff migration images using the time gating function and using the imaging travel time. These time gated images may be separately processed for noise suppression before combining to make the complete image or image gathers.

The noise isolation and suppression may be performed on individually imaged common-source or common-receiver ensembles or it may be performed on images that represent the summation of several (or all) imaged common-source or common-receiver ensembles.

The primary and different orders of the multiple wavefields will image at different times for any specific image point. Therefore, the time gate IC has the potential to decompose or separate the images obtained from the primary and multiple wavefields.

The time gate IC allows efficient application of the Poynting vector method for creating angle gathers after migration of primary and/or multiple reflections. This applies to shot profile migration and RTM. Poynting vectors are generated in time gates and output in addition to the time gated images.

The data processing system <NUM> configured with the time gate IC allows for efficient creation of angle gathers during migration of primary and/or multiple reflections. This applies to shot profile migration and RTM. The time gate method allows a significant computational speedup over previous angle gathers approaches for RTM that map each time sample of the image separately to the angle domain.

When imaging multiple reflections (with or without primaries) more than one reflection event can image reflectors in the earth model. The correlation imaging condition without the time gating imaging condition does not facilitate mapping individual imaged events to the angle domain because it operates in the frequency domain. The time gate imaging condition can isolate multiple imaged events in time so that the events may be mapped individually to the angle domain. This applies to methods that create gathers after or during migration.

The time gate IC may be useful for imaging blended seismic data. Two or more seismic shots acquired simultaneously result in blended data. Blended data acquisition reduces the time and expense of seismic field operations. A field ensemble of blended shots can have multiple shot excitation times and at multiple illuminations from most subsurface reflectors. Due to the response from each shot arriving to image points at a different times and angles, these data may be imaged directly with shot profile or RTM by using a time gate IC so as to separate the multiple images of the reflectors.

The data processing system can generate Kirchhoff migration images using the time gating function and using the imaging travel time. These time gated images may be separately processed for noise suppression before combining to make the complete image or image gathers.

<FIG> is a method of performing seismic imaging. The method <NUM> can be performed by one or more system or component depicted in <FIG> or <FIG>. For example, a data processing system or image processor can perform one or more function or process of method <NUM>. At ACT <NUM>, the data processing system receives seismic data. The seismic data can correspond to acoustic waveforms detected by an ocean bottom seismometer or other seismic data acquisition device. The seismic data can include ensembles of common-source or common-receiver data. In some embodiments, seismic data can relate to subsurface features, such as lithological formations or fluid layers that may indicate the presence of hydrocarbons, minerals or other elements. In some embodiments, seismic data can be received via acoustic signals generated by at least one acoustic source and reflected from at least one subsurface lithologic formation. In some embodiments, the receiving seismic data can include receiving seismic data from a vehicle, for example, an ROV or AUV. In some embodiments, receiving the seismic data can include receiving the seismic data via a wired or wireless communication, such as a direct wired link or through a wireless network or low energy wireless protocol.

At ACT <NUM>, the data processing system propagates the seismic data forward in time through a subsurface model to generate a first wavefield. The first wavefield can refer to a downgoing wavefield or "D" wavefield. The downgoing wavefield can be represented as a function D(x, y, z; ω) in the temporal frequency domain. The downgoing wavefield can be represented as a function D(x, y, z; t), in the time domain. In some embodiments, the seismic data can be propagated from one or more acoustic sources or shot points <NUM>. In some embodiments, the seismic data can be propagated forward in time through a subsurface model to generate a first wavefield after being propagated backward in time through a subsurface model to generate a second wavefield. In some embodiments, the seismic data can be propagated forward in time through a subsurface model to generate a first wavefield prior to being propagated backward in time through a subsurface model to generate a second wavefield.

At ACT <NUM>, the data processing system propagates the seismic data backward in time through the subsurface model to generate a second wavefield. The second wavefield can refer to an upgoing wavefield or "U" wavefield. The upgoing wavefield can be represented as a function U(x, y, z; ω) in the temporal frequency domain. The upgoing wavefield can be represented as a function U(x, y, z; t), in the time domain. In some embodiments, the seismic data can be propagated from one or more acoustic sources or shot points <NUM>. In some embodiments, the seismic data can be propagated forward in time through a subsurface model to generate a first wavefield prior to being propagated backward in time through a subsurface model to generate a second wavefield. In some embodiments, the seismic data can be propagated forward in time through a subsurface model to generate a first wavefield after being propagated backward in time through a subsurface model to generate a second wavefield.

At ACT <NUM>, the data processing system combines the first wavefield with the second wavefield using a time gate imaging condition to produce subsurface images and image gathers. The data processing system can select a time gating imaging condition based on a time gating function or temporal window. The data processing system can apply the time gating imaging condition to the product of the upgoing and downgoing wavefields. The data processing system can combine the two wavefields with an imaging condition (IC) in order to produce subsurface images and image gathers. The seismic images and gathers have many uses, including subsurface geological interpretation and iterative seismic velocity model development.

<FIG> is a diagram illustrating imaging of a primary reflection generated using the system depicted in <FIG> or the method depicted in <FIG>, in accordance with an implementation. The diagram <NUM> illustrates a surface <NUM> of the earth and a reflector <NUM> that can be below the surface <NUM> of the earth. The surface <NUM> can be an ocean bottom or seabed, or a land surface. The reflector <NUM> can be a subsurface lithologic formation, for example.

Diagram <NUM> depicts one reflector <NUM> and a seismic common-source ensemble <NUM> that used source and receivers on the Earth's surface. Time t is the wavefield recording time for propagation from source <NUM> to reflector <NUM>, where reflection occurs, and propagation back to receivers <NUM>. The initial downgoing wavefield D<NUM> at the Earth's surface (z=<NUM>) is an impulsive waveform positioned at t=<NUM> at the source location. All other receiver locations for wavefield D<NUM> are zero. The initial upgoing wavefield U<NUM> at the Earth's surface (z=<NUM>) is the recorded common-source ensemble.

Point P<NUM> (<NUM>) is at (x<NUM>,y<NUM>,z<NUM>) above the reflector <NUM>. The graph <NUM> depicts the wavefields at point P<NUM> (<NUM>). The wavefield D<NUM> is obtained by extrapolating the wavefield D<NUM> forward in time from the source location to location P<NUM>. The waveform <NUM> on D<NUM> appears at the time consistent with propagation from the source position to the location P<NUM>. The wavefield U<NUM> is obtained by extrapolating the wavefield U<NUM> backward in time to location P<NUM>. The waveform <NUM> on U<NUM> appears at the time consistent with propagation from the source position to the reflector, where reflection occurs, and then propagation back up to location P<NUM>. The image at P<NUM> may be zero since the events in U<NUM> and D<NUM> occur at different times.

Point P<NUM> (<NUM>) is at (x<NUM>,y<NUM>,z<NUM>) on the reflector <NUM>. The graph <NUM> depicts the wavefields at point P<NUM> (<NUM>). The events <NUM> and <NUM> in D<NUM> and U<NUM>, respectively, at P<NUM> are coincident in time, so the correlation IC will produce an image of the reflector at this location. The time gate IC will also produce an image, generally in only one time gate at this location.

Point P<NUM> (<NUM>) is at (x<NUM>,y<NUM>,z<NUM>) below the reflector. The graph <NUM> depicts the wavefields at point P<NUM> (<NUM>). The wavefields <NUM> and <NUM> at P<NUM> are analogous (and reversed) to those at P<NUM>. The image at P<NUM> will also be zero since the events in U<NUM> and D<NUM> occur at different times.

<FIG> is a diagram illustrating simultaneous imaging of a primary and a multiple reflection generated using the system depicted in <FIG> or the method depicted in <FIG>, in accordance with an implementation. <FIG> is different from <FIG> in that <FIG> shows that imaging multiples generally involves more complicated wavefields, especially the initial downgoing wavefield D<NUM>. The graph <NUM> depicts the wavefields at point P1 (<NUM>). At P1 (<NUM>), the downgoing wavefield events <NUM>, <NUM> and <NUM> are not coincident in time with the upgoing wavefield events <NUM> and <NUM>, so the image at P1 may be zero.

However, the Primary reflection and a Multiple reflection in the upgoing wavefield do separately image the reflector at location P<NUM>. The graph <NUM> depicts the wavefields at point P2 (<NUM>). For example, the downgoing wavefield events <NUM> and <NUM> can be coincident in time with the upgoing wavefield events <NUM> and <NUM>. Both pairs of events in D<NUM> and U<NUM> (e.g., <NUM> and <NUM>; and <NUM> and <NUM>) can be coincident at different times as illustrated in the figure. The data processing system, using the correlation IC, can sum the images from both pairs of events into a single composite image. The data processing system can use the time gate IC to separate the images of these events so they may be analyzed after seismic imaging. At P3, the downgoing wavefields can be <NUM>, <NUM> and <NUM>; and the upgoing wavefield events can be <NUM> and <NUM>. <FIG> shows that the event pair <NUM> and <NUM> can image below the reflector at P<NUM>. The graph <NUM> depicts the wavefields at point P3 (<NUM>). This can be attributed to crosstalk noise that can contaminate a seismic image. The time gate IC may image these events also.

<FIG> is a diagram illustrating formation of the image trace at location P2 from <FIG> generated using the system depicted in <FIG> or the method depicted in <FIG>, in accordance with an implementation. <FIG> shows how the data processing system can form the image at location P<NUM> depicted in <FIG>. Part (a) of diagram <NUM> shows the downgoing wavefields <NUM>, <NUM> and <NUM> at location P<NUM>, and the upgoing wavefields <NUM> and <NUM> at location P<NUM>. The data processing system can use these two wavefields at location P<NUM> to generate the image trace <NUM> that would be created from the correlation IC assuming that points P<NUM>, P<NUM>, and P<NUM> are horizontally aligned. The image trace <NUM> illustrates an event <NUM> at location P<NUM>. These points are labeled on the image traces at their correct depths in the figure. The second arrival in the wavefield traces has a different waveform than does the first arrival in this example. The image trace I<NUM> (<NUM>) is a function of depth and has an image <NUM> that is approximately the sum of the squares of the two aligned wavefield events (<NUM> and <NUM>; and <NUM> and <NUM>). It is a mixture of the two images.

Part (b) (<NUM>) of diagram <NUM> is the analogous display of <NUM>, but with the data processing system using the time gate IC with three time gates <NUM>, <NUM>, and <NUM>. There are three image traces I<NUM>(n) (<NUM>, <NUM> and <NUM>), one for each time gate (n=<NUM>,<NUM>,<NUM>). The first pair of events (<NUM> and <NUM> in time gate <NUM>) creates an image <NUM> that appears on I<NUM>(<NUM>) (<NUM>). The image <NUM> from the second pair of events (<NUM> and <NUM> in time gate <NUM>) appears on I<NUM>(<NUM>) (<NUM>). The data processing system retains, in each image, the wave shape and amplitude character of the pair of events used by the data processing system to create the image. This improves accuracy of subsequent AVO and amplitude analyses. This separation of images is also ideal for making angle gathers since each imaged event generally associates with different angles.

Events could straddle the time gate boundaries (e.g., a boundary between <NUM> and <NUM>) shown in the figure causing imaging artifacts. Carefully designed overlapping time windows (function Wn(t) in the Invention document) can be centered on each time gate to reduce imaging artifacts associated with time gate boundaries. Also, the number of time gates may be chosen to suit the imaging application.

Thus, by imaging each event in a separate time gate (e.g., time gates <NUM> and <NUM>), the data processing system can use the time gate IC to separate noise from real reflector images after imaging. It also allows the data processing system to map each imaged event (e.g., <NUM> or <NUM>) separately into the angle domain as the data processing system makes angle gathers either during or after seismic imaging. By handling each event separately, the data processing system configured with the time gate imaging method improved amplitude control for AVO analyses, while reducing computational resource usage.

<FIG> is an isometric schematic view of an example of a seismic operation in deep water facilitated by a first marine vessel <NUM>. <FIG> is a non-limiting illustrative example of a marine environment in which the systems and methods of the present disclosure can perform a seismic survey to collect seismic data and generate images.

By way of example, <FIG> illustrates a first vessel <NUM> positioned on a surface <NUM> of a water column <NUM> and includes a deck <NUM> which supports operational equipment. At least a portion of the deck <NUM> includes space for a plurality of sensor device racks <NUM> where seismic sensor devices (e.g., first device <NUM>) are stored. The sensor device racks <NUM> may also include data retrieval devices or sensor recharging devices.

The deck <NUM> also includes one or more cranes 25A, 25B attached thereto to facilitate transfer of at least a portion of the operational equipment, such as an ROV (e.g., second device <NUM>) or seismic sensor devices, from the deck <NUM> to the water column <NUM>. For example, a crane 25A coupled to the deck <NUM> is configured to lower and raise an ROV 35A, which transfers and positions one or more sensor devices <NUM> on a seabed <NUM>. The seabed <NUM> can include a lakebed <NUM>, ocean floor <NUM>, or earth <NUM>. The ROV 35A is coupled to the first vessel <NUM> by a tether 46A and an umbilical cable 44A that provides power, communications, and control to the ROV 35A. A tether management system (TMS) 50A is also coupled between the umbilical cable 44A and the tether 46A. The TMS 50A may be utilized as an intermediary, subsurface platform from which to operate the ROV 35A. For most ROV 35A operations at or near the seabed <NUM>, the TMS 50A can be positioned approximately <NUM> feet ( <NUM> foot = <NUM>) above seabed <NUM> and can pay out tether 46A as needed for ROV 35A to move freely above seabed <NUM> in order to position and transfer seismic sensor devices <NUM> thereon.

A crane 25B may be coupled (e.g., via a latch, anchor, nuts and bolts, screw, suction cup, magnet, or other fastener) to a stern of the first vessel <NUM>, or other locations on the first vessel <NUM>. Each of the cranes 25A, 25B may be any lifting device or launch and recovery system (LARS) adapted to operate in a marine environment. The crane 25B can be coupled to a seismic sensor transfer device <NUM> by a cable <NUM>. The transfer device <NUM> may be a drone, a skid structure, a basket, or any device capable of housing one or more sensor devices <NUM> therein. The transfer device <NUM> may be a structure configured as a magazine adapted to house and transport one or more sensor devices <NUM>. The transfer device <NUM> may include an on-board power supply, a motor or gearbox, or a propulsion system <NUM>. The transfer device <NUM> can be configured as a sensor device storage rack for transfer of sensor devices <NUM> from the first vessel <NUM> to the ROV 35A, and from the ROV 35A to the first vessel <NUM>. The transfer device <NUM> may include an on-board power supply, a motor or gearbox, or a propulsion system <NUM>. Alternatively, the transfer device <NUM> may not include any integral power devices or not require any external or internal power source. The cable <NUM> can provide power or control to the transfer device <NUM>. Alternatively, the cable <NUM> may be an umbilical, a tether, a cord, a wire, a rope, and the like, that is configured solely for support of the transfer device <NUM>.

The ROV 35A can include a seismic sensor device storage compartment <NUM> that is configured to store one or more seismic sensor devices <NUM> (e.g., first devices <NUM>) therein for a deployment or retrieval operation. The storage compartment <NUM> may include a magazine, a rack, or a container configured to store the seismic sensor devices. The storage compartment <NUM> may also include a conveyor, such as a movable platform having the seismic sensor devices thereon, such as a carousel or linear platform configured to support and move the seismic sensor devices <NUM> therein. The seismic sensor devices <NUM> can be deployed on the seabed <NUM> and retrieved therefrom by operation of the movable platform. The ROV 35A may be positioned at a predetermined location above or on the seabed <NUM> and seismic sensor devices <NUM> are rolled, conveyed, or otherwise moved out of the storage compartment <NUM> at the predetermined location. The seismic sensor devices <NUM> can be deployed and retrieved from the storage compartment <NUM> by a robotic device <NUM>, such as a robotic arm, an end effector or a manipulator, disposed on the ROV 35A.

The seismic sensor device <NUM> may be referred to as seismic data acquisition unit <NUM> or node <NUM> or first device <NUM>. The seismic data acquisition unit <NUM> can record seismic data. The seismic data acquisition unit <NUM> may include one or more of at least one geophone, at least one hydrophone, at least one power source (e.g., a battery, external solar panel), at least one clock, at least one tilt meter, at least one environmental sensor, at least one seismic data recorder, at least global positioning system sensor, at least one wireless or wired transmitter, at least one wireless or wired receiver, at least one wireless or wired transceiver, or at least one processor. The seismic sensor device <NUM> may be a self-contained unit such that all electronic connections are within the unit, or one or more components can be external to the seismic sensor device <NUM>. During recording, the seismic sensor device <NUM> may operate in a self-contained manner such that the node does not require external communication or control. The seismic sensor device <NUM> may include several geophones and hydrophones configured to detect acoustic waves that are reflected by subsurface lithological formation or hydrocarbon deposits. The seismic sensor device <NUM> may further include one or more geophones that are configured to vibrate the seismic sensor device <NUM> or a portion of the seismic sensor device <NUM> in order to detect a degree of coupling between a surface of the seismic sensor device <NUM> and a ground surface. One or more component of the seismic sensor device <NUM> may attach to a gimbaled platform having multiple degrees of freedom. For example, the clock may be attached to the gimbaled platform to minimize the effects of gravity on the clock.

For example, in a deployment operation, a first plurality of seismic sensor devices, comprising one or more sensor devices <NUM>, may be loaded into the storage compartment <NUM> while on the first vessel <NUM> in a pre-loading operation. The ROV 35A, having the storage compartment coupled thereto, is then lowered to a subsurface position in the water column <NUM>. The ROV 35A utilizes commands from personnel on the first vessel <NUM> to operate along a course to transfer the first plurality of seismic sensor devices <NUM> from the storage compartment <NUM> and deploy the individual sensor devices <NUM> at selected locations on the seabed <NUM>. Once the storage compartment <NUM> is depleted of the first plurality of seismic sensor devices <NUM>, the transfer device <NUM> is used to ferry a second plurality of seismic sensor devices <NUM> as a payload from first vessel <NUM> to the ROV 35A.

The transfer system <NUM> may be preloaded with a second plurality of seismic sensor devices <NUM> while on or adjacent the first vessel <NUM>. When a suitable number of seismic sensor devices <NUM> are loaded onto the transfer device <NUM>, the transfer device <NUM> may be lowered by crane 25B to a selected depth in the water column <NUM>. The ROV 35A and transfer device <NUM> are mated at a subsurface location to allow transfer of the second plurality of seismic sensor devices <NUM> from the transfer device <NUM> to the storage compartment <NUM>. When the transfer device <NUM> and ROV 35A are mated, the second plurality of seismic sensor devices <NUM> contained in the transfer device <NUM> are transferred to the storage compartment <NUM> of the ROV 35A. Once the storage compartment <NUM> is reloaded, the ROV 35A and transfer device <NUM> are detached or unmated and seismic sensor device placement by ROV 35A may resume. Reloading of the storage compartment <NUM> can be provided while the first vessel <NUM> is in motion. If the transfer device <NUM> is empty after transfer of the second plurality of seismic sensor devices <NUM>, the transfer device <NUM> may be raised by the crane 25B to the vessel <NUM> where a reloading operation replenishes the transfer device <NUM> with a third plurality of seismic sensor devices <NUM>. The transfer device <NUM> may then be lowered to a selected depth when the storage compartment <NUM> is reloaded. This process may repeat as until a desired number of seismic sensor devices <NUM> have been deployed.

Using the transfer device <NUM> to reload the ROV 35A at a subsurface location reduces the time required to place the seismic sensor devices <NUM> on the seabed <NUM>, or "planting" time, as the ROV 35A is not raised and lowered to the surface <NUM> for seismic sensor device reloading. The ROV 35A can synchronize a clock of the node <NUM> at the time of planting. Further, mechanical stresses placed on equipment utilized to lift and lower the ROV 35A are minimized as the ROV 35A may be operated below the surface <NUM> for longer periods. The reduced lifting and lowering of the ROV 35A may be particularly advantageous in foul weather or rough sea conditions. Thus, the lifetime of equipment may be enhanced as the ROV 35A and related equipment are not raised above surface <NUM>, which may cause the ROV 35A and related equipment to be damaged, or pose a risk of injury to the vessel personnel.

Likewise, in a retrieval operation, the ROV 35A can utilize commands from personnel on the first vessel <NUM> to retrieve each seismic sensor device <NUM> that was previously placed on seabed <NUM>, or collect data from the seismic sensor device <NUM> without retrieving the device <NUM>. The ROV 35A can adjust the clock of the device <NUM> while collecting the seismic data. The retrieved seismic sensor devices <NUM> are placed into the storage compartment <NUM> of the ROV 35A. In some implementations, the ROV 35A may be sequentially positioned adjacent each seismic sensor device <NUM> on the seabed <NUM> and the seismic sensor devices <NUM> are rolled, conveyed, or otherwise moved from the seabed <NUM> to the storage compartment <NUM>. The seismic sensor devices <NUM> can be retrieved from the seabed <NUM> by a robotic device <NUM> disposed on the ROV 35A.

Once the storage compartment <NUM> is full or contains a pre-determined number of seismic sensor devices <NUM>, the transfer device <NUM> is lowered to a position below the surface <NUM> and mated with the ROV 35A. The transfer device <NUM> may be lowered by crane 25B to a selected depth in the water column <NUM>, and the ROV 35A and transfer device <NUM> are mated at a subsurface location. Once mated, the retrieved seismic sensor devices <NUM> contained in the storage compartment <NUM> are transferred to the transfer device <NUM>. Once the storage compartment <NUM> is depleted of retrieved sensor devices, the ROV 35A and transfer device <NUM> are detached and sensor device retrieval by ROV 35A may resume. Thus, the transfer device <NUM> is used to ferry the retrieved seismic sensor devices <NUM> as a payload to the first vessel <NUM>, allowing the ROV 35A to continue collection of the seismic sensor devices <NUM> from the seabed <NUM>. In this manner, sensor device retrieval time is significantly reduced as the ROV 35A is not raised and lowered for sensor device unloading. Further, safety issues and mechanical stresses placed on equipment related to the ROV 35A are minimized as the ROV 35A may be subsurface for longer periods.

For example, the first vessel <NUM> can travel in a first direction <NUM>, such as in the +X direction, which may be a compass heading or other linear or predetermined direction. The first direction <NUM> may also account for or include drift caused by wave action, current(s) or wind speed and direction. The plurality of seismic sensor devices <NUM> can be placed on the seabed <NUM> in selected locations, such as a plurality of rows Rn in the X direction (R1 and R2 are shown) or columns Cn in the Y direction (C1-Cn are shown), wherein n equals an integer. The rows Rn and columns Cn can define a grid or array, wherein each row Rn (e.g., R1 - R2) comprises a receiver line in the width of a sensor array (X direction) or each column Cn comprises a receiver line in a length of the sensor array (Y direction). The distance between adjacent sensor devices <NUM> in the rows is shown as distance LR and the distance between adjacent sensor devices <NUM> in the columns is shown as distance LC. While a substantially square pattern is shown, other patterns may be formed on the seabed <NUM>. Other patterns include non-linear receiver lines or non-square patterns. The pattern(s) may be pre-determined or result from other factors, such as topography of the seabed <NUM>. The distances LR and LC can be substantially equal and may include dimensions between about <NUM> meters to about <NUM> meters, or greater. The distance between adjacent seismic sensor devices <NUM> may be predetermined or result from topography of the seabed <NUM> as described above.

The first vessel <NUM> is operated at a speed, such as an allowable or safe speed for operation of the first vessel <NUM> and any equipment being towed by the first vessel <NUM>. The speed may take into account any weather conditions, such as wind speed and wave action, as well as currents in the water column <NUM>. The speed of the vessel may also be determined by any operations equipment that is suspended by, attached to, or otherwise being towed by the first vessel <NUM>. For example, the speed can be limited by the drag coefficients of components of the ROV 35A, such as the TMS 50A and umbilical cable 44A, as well as any weather conditions or currents in the water column <NUM>. As the components of the ROV 35A are subject to drag that is dependent on the depth of the components in the water column <NUM>, the first vessel speed may operate in a range of less than about <NUM> knot (<NUM>/h).

In examples where two receiver lines (rows R1 and R2) are being laid, the first vessel includes a first speed of between about <NUM> knots and about <NUM> knots. In some implementations, the first speed includes an average speed of between about <NUM> knots, which includes intermittent speeds of less than <NUM> knots and speeds greater than about <NUM> knot, depending on weather conditions, such as wave action, wind speeds, or currents in the water column <NUM>.

During a seismic survey, one receiver line, such as row R1 may be deployed. When the single receiver line is completed a second vessel <NUM> can be used to provide a source signal. In some cases, the first vessel or other device can provide the source signal. The second vessel <NUM> is provided with a source device or acoustic source device <NUM>, which may be a device capable of producing acoustical signals or vibrational signals suitable for obtaining the survey data. The source signal propagates to the seabed <NUM> and a portion of the signal is reflected back to the seismic sensor devices <NUM>. The second vessel <NUM> may be required to make multiple passes, for example at least four passes, per a single receiver line (row R1 in this example). During the time the second vessel <NUM> is making the passes, the first vessel <NUM> continues deployment of a second receiver line. However, the time involved in making the passes by the second vessel <NUM> is much shorter than the deployment time of the second receiver line. This causes a lag time in the seismic survey as the second vessel <NUM> sits idle while the first vessel <NUM> is completing the second receiver line.

The first vessel <NUM> can use one ROV 35A to lay sensor devices to form a first set of two receiver lines (rows R1 and R2) in any number of columns, which may produce a length of each receiver line of up to and including several miles (<NUM> mile =<NUM>).

The two receiver lines (rows R1 and R2) can be substantially (e.g., within +/-<NUM> degrees) parallel. When a single directional pass of the first vessel <NUM> is completed and the first set (rows R1, R2) of seismic sensor devices <NUM> are laid to a predetermined length, the second vessel <NUM>, provided with the source device <NUM>, is utilized to provide the source signal. The second vessel <NUM> can make eight or more passes along the two receiver lines to complete the seismic survey of the two rows R1 and R2.

While the second vessel <NUM> is shooting along the two rows R1 and R2, the first vessel <NUM> may turn <NUM> degrees and travel in the X direction in order to lay seismic sensor devices <NUM> in another two rows adjacent the rows R1 and R2, thereby forming a second set of two receiver lines. The second vessel <NUM> may then make another series of passes along the second set of receiver lines while the first vessel <NUM> turns <NUM> degrees to travel in the +X direction to lay another set of receiver lines. The process may repeat until a specified area of the seabed <NUM> has been surveyed. Thus, the idle time of the second vessel <NUM> is minimized as the deployment time for laying receiver lines is cut approximately in half by deploying two rows in one pass of the vessel <NUM>.

Although only two rows R1 and R2 are shown, the sensor device <NUM> layout is not limited to this configuration as the ROV 35A may be adapted to layout more than two rows of sensor devices in a single directional tow. For example, the ROV 35A may be controlled to lay out between three and six rows of sensor devices <NUM>, or an even greater number of rows in a single directional tow. The width of a "one pass" run of the first vessel <NUM> to layout the width of the sensor array can be limited by the length of the tether 46A or the spacing (distance LR) between sensor devices <NUM>.

<FIG> depicts a block diagram of an architecture for a computing system employed to implement various elements of the system depicted in <FIG>, to perform the method depicted in <FIG>, or generate the images depicted in <FIG>. <FIG> is a block diagram of a data processing system including a computer system <NUM> in accordance with an embodiment. The computer system can include or execute a coherency filter component. The data processing system, computer system or computing device <NUM> can be used to implement one or more component configured to filter, translate, transform, generate, analyze, or otherwise process the data or signals depicted in <FIG>. The computing system <NUM> includes a bus <NUM> or other communication component for communicating information and a processor 810a-n or processing circuit coupled to the bus <NUM> for processing information. The computing system <NUM> can also include one or more processors <NUM> or processing circuits coupled to the bus for processing information. The computing system <NUM> also includes main memory <NUM>, such as a random access memory (RAM) or other dynamic storage device, coupled to the bus <NUM> for storing information, and instructions to be executed by the processor <NUM>. Main memory <NUM> can also be used for storing seismic data, time gating function data, temporal windows, images, reports, executable code, temporary variables, or other intermediate information during execution of instructions by the processor <NUM>. The computing system <NUM> may further include a read only memory (ROM) <NUM> or other static storage device coupled to the bus <NUM> for storing static information and instructions for the processor <NUM>. A storage device <NUM>, such as a solid state device, magnetic disk or optical disk, is coupled to the bus <NUM> for persistently storing information and instructions.

The computing system <NUM> may be coupled via the bus <NUM> to a display <NUM> or display device, such as a liquid crystal display, or active matrix display, for displaying information to a user. An input device <NUM>, such as a keyboard including alphanumeric and other keys, may be coupled to the bus <NUM> for communicating information and command selections to the processor <NUM>. The input device <NUM> can include a touch screen display <NUM>. The input device <NUM> can also include a cursor control, such as a mouse, a trackball, or cursor direction keys, for communicating direction information and command selections to the processor <NUM> and for controlling cursor movement on the display <NUM>.

In some embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to effect illustrative implementations. Thus, embodiments are not limited to any specific combination of hardware circuitry and software.

Although an example computing system has been described in <FIG>, embodiments of the subject matter and the functional operations described in this specification can be implemented in other types of digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them.

The subject matter described in this specification can be implemented as one or more computer programs, e.g., one or more circuits of computer program instructions, encoded on one or more computer storage media for execution by, or to control the operation of, data processing apparatus. Alternatively or in addition, the program instructions can be encoded on an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or be included in, one or more separate components or media (e.g., multiple CDs, disks, or other storage devices).

The operations described in this specification can be performed by a data processing apparatus on data stored on one or more computer-readable storage devices or received from other sources. The term "data processing apparatus" or "computing device" encompasses various apparatuses, devices, and machines for processing data, including by way of example a programmable processor, a computer, a system on a chip, or multiple ones, or combinations of the foregoing.

A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a circuit, component, subroutine, object, or other unit suitable for use in a computing environment. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more circuits, subprograms, or portions of code).

Processors suitable for the execution of a computer program include, by way of example, microprocessors, and any one or more processors of a digital computer. A processor can receive instructions and data from a read only memory or a random access memory or both. The elements of a computer are a processor for performing actions in accordance with instructions and one or more memory devices for storing instructions and data. A computer can include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. A computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a personal digital assistant (PDA), a Global Positioning System (GPS) receiver, or a portable storage device (e.g., a universal serial bus (USB) flash drive), to name just a few. Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks.

To provide for interaction with a user, implementations of the subject matter described in this specification can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer.

The implementations described herein can be implemented in any of numerous ways including, for example, using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers.

Such computers may be interconnected by one or more networks in any suitable form, including a local area network or a wide area network, such as an enterprise network, and intelligent network (IN) or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol and may include wireless networks, wired networks or fiber optic networks.

A computer employed to implement at least a portion of the functionality described herein may comprise a memory, one or more processing units (also referred to herein simply as "processors"), one or more communication interfaces, one or more display units, and one or more user input devices. The memory may comprise any computer-readable media, and may store computer instructions (also referred to herein as "processor-executable instructions") for implementing the various functionalities described herein. The processing unit(s) may be used to execute the instructions. The communication interface(s) may be coupled to a wired or wireless network, bus, or other communication means and may therefore allow the computer to transmit communications to or receive communications from other devices. The display unit(s) may be provided, for example, to allow a user to view various information in connection with execution of the instructions. The user input device(s) may be provided, for example, to allow the user to make manual adjustments, make selections, enter data or various other information, or interact in any of a variety of manners with the processor during execution of the instructions.

The various methods or processes outlined herein may be coded as software that is executable on one or more processors that employ any one of a variety of operating systems or platforms. Additionally, such software may be written using any of a number of suitable programming languages or programming or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on a framework or virtual machine.

In this respect, various inventive concepts may be embodied as a computer readable storage medium (or multiple computer readable storage media) (e.g., a computer memory, one or more floppy discs, compact discs, optical discs, magnetic tapes, flash memories, circuit configurations in Field Programmable Gate Arrays or other semiconductor devices, or other non-transitory medium or tangible computer storage medium) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments of the solution discussed above. The computer readable medium or media can be transportable, such that the program or programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the present solution as discussed above.

The terms "program" or "software" are used herein to refer to any type of computer code or set of computer-executable instructions that can be employed to program a computer or other processor to implement various aspects of embodiments as discussed above. One or more computer programs that when executed perform methods of the present solution need not reside on a single computer or processor, but may be distributed in a modular fashion amongst a number of different computers or processors to implement various aspects of the present solution.

Program modules can include routines, programs, objects, components, data structures, or other components that perform particular tasks or implement particular abstract data types. The functionality of the program modules can be combined or distributed as desired in various embodiments.

References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms. References to at least one of a conjunctive list of terms may be construed as an inclusive OR to indicate any of a single, more than one, and all of the described terms. A reference to "at least one of 'A' and 'B'" can include only 'A', only 'B', as well as both 'A' and 'B'. Elements other than 'A' and 'B' can also be included.

Claim 1:
A system to perform seismic imaging, comprising:
a data processing system (<NUM>) comprising a propagation component (<NUM>), gating component (<NUM>), and wavefield combination component (<NUM>), the data processing system (<NUM>) to:
receive seismic data from one or more seismic data sources (<NUM>) comprising data ensembles of common-source or common-receiver data;
propagate the received seismic data forward in time through a subsurface model to generate a first wavefield;
propagate the received seismic data backward in time through the subsurface model to generate a second wavefield;
characterised by combining the first wavefield with the second wavefield using a time gate imaging condition;
generate a <NUM>-dimensional image from the combination of the first wavefield with the second wavefield using the time gate imaging condition;
the time gate imaging condition to isolate multiple imaged events in time so that the events are mapped individually to the angle domain such that the data processing system (<NUM>) separates noise from real reflector images.