Abstract: A backpropagation enabled model is trained for estimating time-lapse property changes of a subsurface volume. Synthetic models of the subsurface volume are generated, with pre-determined property changes before and after a time lapse. These models are used to compute baseline-monitor pairs of synthetic seismic traces before and after the time lapse, wherein the baseline synthetic traces are computed from the synthetic model before the time lapse and the monitor synthetic traces are computed from the synthetic model after the time lapse. A ground truth 4D attribute characterizing the time-lapse property changes in the synthetic models is defined, and a backpropagation enabled model is trained by feeding the baseline-monitor pairs of synthetic seismic traces and the corresponding ground truth 4D attribute. The thus obtained trained backpropagation enabled model can be used to estimate time-lapse property changes of the actual subsurface Earth volume from actual baseline-monitor pairs of seismic traces.

Abstract: A method for generating an image of a subsurface feature, comprises providing seismic data containing information about the feature, comprising i) a first dataset comprising a first up-going wave-field and a first down-going wave-field, ii) a second dataset comprising a second up-going wave-field and a second down-going wave-field, wherein the second dataset is collected at a time that is later than the first dataset by a time interval, creating an up-going 4D difference dataset U by subtracting one of the first and second up-going wave-fields from the other and creating a down-going 4D difference dataset D by subtracting one of the first and second down-going wave-fields from the other, creating a weighting function W that is a function of the similarity of the difference datasets, and creating an image of the feature by generating a 4D similarity stack, where the 4D similarity stack is defined as (U+D)*W/2.

Abstract: A method for identifying clock timing discrepancies in at least one clock of interest that is associated with a marine seismic receiver, comprises collecting from at least one marine receiver other than the receiver of interest a first data set corresponding to a selected time period, said first data set being selected to include ocean wave signals; collecting from the receiver of interest a second data set corresponding to the selected time period, said second data set being selected to include ocean wave signals; applying a mathematical prediction technique to the ocean wave signals in the first data set so as to generate a predicted response for a receiver co-located with the receiver of interest; comparing the predicted response to the second data set so as to generate a correlation data set; and using the correlation data set to determine a corrected parameter for the receiver of interest.

Abstract: A method for identifying clock timing discrepancies in a plurality of clocks that are each associated with a seismic receiver, comprises the steps of collecting from at least a pair of receivers a data set corresponding to a selected time period, cross-correlating the data sets between at least one pair of receivers so as to produce cross-correlated data for positive, zero, and negative time lags, comparing the cross-correlated data for the positive and negative time lags to measure a timing asymmetry about the zero-lag time, and, for a receiver pair for which there is a non-zero timing asymmetry, using the asymmetry to identify a timing discrepancy between the clocks associated with that receiver pair. The each data set can be filtered so as to obtain data in a selected frequency range, which may avoid an active shot frequency. The data may be collected in the absence of active seismic shots.

Abstract: A method for generating an image of a subsurface feature, comprises providing seismic data containing information about the feature, comprising i) a first dataset comprising a first up-going wave-field and a first down-going wave-field, ii) a second dataset comprising a second up-going wave-field and a second down-going wave-field, wherein the second dataset is collected at a time that is later than the first dataset by a time interval, creating an up-going 4D difference dataset U by subtracting one of the first and second up-going wave-fields from the other and creating a down-going 4D difference dataset D by subtracting one of the first and second down-going wave-fields from the other, creating a weighting function W that is a function of the similarity of the difference datasets, and creating an image of the feature by generating a 4D similarity stack, where the 4D similarity stack is defined as (U+D)*W/2.

Abstract: A method for identifying clock timing discrepancies in at least one clock of interest that is associated with a marine seismic receiver, comprises collecting from at least one marine receiver other than the receiver of interest a first data set corresponding to a selected time period, said first data set being selected to include ocean wave signals; collecting from the receiver of interest a second data set corresponding to the selected time period, said second data set being selected to include ocean wave signals; applying a mathematical prediction technique to the ocean wave signals in the first data set so as to generate a predicted response for a receiver co-located with the receiver of interest; comparing the predicted response to the second data set so as to generate a correlation data set; and using the correlation data set to determine a corrected parameter for the receiver of interest.

Abstract: A method for identifying clock timing discrepancies in a plurality of clocks that are each associated with a seismic receiver, comprises the steps of collecting from at least a pair of receivers a data set corresponding to a selected time period, cross-correlating the data sets between at least one pair of receivers so as to produce cross-correlated data for positive, zero, and negative time lags, comparing the cross-correlated data for the positive and negative time lags to measure a timing asymmetry about the zero-lag time, and, for a receiver pair for which there is a non-zero timing asymmetry, using the asymmetry to identify a timing discrepancy between the clocks associated with that receiver pair. The each data set can be filtered so as to obtain data in a selected frequency range, which may avoid an active shot frequency. The data may be collected in the absence of active seismic shots.

Abstract: A method of monitoring a subsurface formation (2) including a region of interest (1), below a surface region, which method comprises the steps of exciting seismic interface waves (14), in the surface region over an area of the earth's surface at a first and a second moment in time; detecting seismic interface waves signals for a plurality of locations in the area; determining, from the detected seismic interface wave signals, an areal distribution of a parameter related to seismic interface wave velocity change between the first and second moments in time; and inferring, from the areal distribution, an indication of a volume change of the region of interest between the first and second moments in time.

Abstract: A method for monitoring the movement of fluid through a subsurface formation of interest, comprising: a) providing a set of signals obtained by transmitting seismic waves through the formation of interest and receiving signals emanating from the multi-layered system in response to the seismic waves with one or more receivers located a distance from the seismic source(s), b) identifying one or more critically refracted waves among the signals so as to generate a first data set of refracted signals, c) repeating steps a) and b) after a period of time so as to generate a second data set of refracted signals, d) comparing the second data set to the first data set so as to generate a time-lapse data set, e) imaging the time-lapse data set using travel time tomography; and f) inferring information about the movement of fluid based on the image generated in step e).

Abstract: A method of detecting a lateral boundary of a compacting or expanding region in a subsurface formation, which method comprises determining non-vertical deformation of the earth' s surface above the subsurface formation over a period of time; identifying at least on contraction area and at least one adjacent dilatation area of the earth' s surface from the non-vertical deformation over the period of time; and using the contraction area and the adjacent dilatation area as an indication of a lateral boundary of the compacting or expanding region; and a method for producing hydrocarbons.

Abstract: A method of monitoring a subsurface formation underneath a sea bed, the method comprising determining non-vertical deformation of the sea floor over a period of time and inferring a parameter related to a volume change in the subsurface formation from the non-vertical deformation of the sea. Determining the non-vertical deformation of the sea floor comprises selecting a plurality of locations on the sea floor and determining a change in distance between at least one pair of the locations over the period of time.

Abstract: A method of investigating a reservoir region in a subsurface formation by a time-lapse seismic survey. The subsurface formation comprises a further formation region adjacent to the reservoir region. Data are obtained from a time-lapse seismic survey and includes seismic data of the subsurface formation at a first point in time and a later point in time. The seismic data is processed to obtain a seismic representation of change in a predetermined seismic parameter in the further formation region, whereby the seismic parameter is dependent on stress. The seismic representation of change in the seismic parameter in the further formation region is interpreted for an indication of changes of stress distribution in the further formation region, and a property of the reservoir region is derived using the indication of change of stress distribution in the further formation region.