Abstract: Disclosed is a method for characterizing the evolution of a subsurface volume over time. The method comprises providing a first and second surveys of the reservoir with a first and second sets of seismic traces, performing an inversion to obtain estimates of changes having occurred between said first time and said second time in terms of at least one model parameter; wherein the subsurface volume is divided into regions according to a high order discrete classification attributed in accordance with the region's geologic characteristics, and said inversion is constrained per region of subsurface volume. The regions of subsurface volume may be geological layers.

Abstract: Disclosed is a method for characterizing the evolution of a reservoir by determining a seismic wavelet which links observed seismic data to a sequence of reflectivities. The method comprises obtaining seismic data (200) representing seismic changes which have occurred between a first time and a second time, said seismic data comprising a plurality of seismic traces; and performing an optimization operation simultaneously (230) on the seismic traces so as to optimize for said seismic wavelet. The optimization operation may be performed without using known reflectivity data as an input.

Abstract: Disclosed is a method of modelling a subsurface volume, and a corresponding computer program and apparatus. The method comprises defining a regular planar grid of regularly arranged locations in the two dimensions substantially parallel to the surface, and calculating a plurality of one dimensional arrays, each one dimensional array extending from a different one of the regularly arranged locations, in the direction from surface to subsurface. Each of the one dimensional arrays comprises a plurality of one dimensional cells, wherein the cells are delineated according to actual geological features of the subsurface volume.

Abstract: Disclosed is a method for characterizing the evolution of a sub-surface volume. The method comprises providing a first and second surveys of the reservoir with a first and second sets of seismic traces, constructing an analytic filter operable to shift one or more seismic traces in dependence of a model parameter; and performing an inversion to obtain estimates of the model parameter such that the analytic filter aligns said first survey and said second survey. The analytic filter may be a plane wave destruction filter, and be such that the model parameter is a function of the analytic filter and is not a function of one or more of said second set of seismic traces.

Abstract: Disclosed is a method a seismic inversion for petrophysical properties of a subsurface volume comprising the steps of: obtaining petrophysical data relating to valid geological and/or dynamical scenarios, converting this data into valid combinations of elastic parameters; projecting the valid combinations of elastic parameters onto a spherical plot; and determining a penalty term from the distances between each cell of the spherical plot and the nearest valid combination of elastic parameters within the subsurface volume. Valid geological and/or dynamical scenarios comprise those which are petrophysically possible. The penalty term is then used to constrain an inversion minimizing a cost function associated with seismic mismatch between two or more seismic surveys.

Abstract: Disclosed is a method of characterising a subsurface volume. The method comprises: extracting a geobody from seismic data arranged within a discretised volume comprising a plurality of cells, the geobody comprising a subset of the plurality of cells, each cell of the subset having one or more properties indicative of a particular fluid phase. The extraction of the geobody comprises: determining a propagation probability value for each cell indicative of the probability that a front will propagate through the cell; beginning from a source within the discretised volume, using the propagation probability value to calculate a travel-time for each cell, the travel time describing the time the front takes to travel from the source point to the cell; and using the traveltimes to extract the geobody from the seismic data.

Abstract: Disclosed is a method for characterising the evolution of a sub-surface volume. The method comprises providing a first and second surveys of the reservoir with a first and second sets of seismic traces, constructing an analytic filter operable to shift one or more seismic traces in dependence of a model parameter; and performing an inversion to obtain estimates of the model parameter such that the analytic filter aligns said first survey and said second survey. The analytic filter may be a plane wave destruction filter, and be such that the model parameter is a function of the analytic filter and is not a function of one or more of said second set of seismic traces.

Abstract: Disclosed is a method for characterising the evolution of a subsurface volume over time. The method comprises providing a first and second surveys of the reservoir with a first and second sets of seismic traces, performing an inversion to obtain estimates of changes having occurred between said first time and said second time in terms of at least one model parameter; wherein the subsurface volume is divided into regions according to a high order discrete classification attributed in accordance with the region's geologic characteristics, and said inversion is constrained per region of subsurface volume. The regions of subsurface volume may be geological layers.

Abstract: Disclosed is a method for characterising the evolution of a reservoir by determining a seismic wavelet which links observed seismic data to a sequence of reflectivities. The method comprises obtaining seismic data (200) representing seismic changes which have occurred between a first time and a second time, said seismic data comprising a plurality of seismic traces; and performing an optimisation operation simultaneously (230) on the seismic traces so as to optimise for said seismic wavelet. The optimisation operation may be performed without using known reflectivity data as an input.

Abstract: Disclosed is a method a seismic inversion for petrophysical properties of a subsurface volume comprising the steps of: obtaining petrophysical data relating to valid geological and/or dynamical scenarios, converting this data into valid combinations of elastic parameters; projecting the valid combinations of elastic parameters onto a spherical plot; and determining a penalty term from the distances between each cell of the spherical plot and the nearest valid combination of elastic parameters within the subsurface volume. Valid geological and/or dynamical scenarios comprise those which are petrophysically possible. The penalty term is then used to constrain an inversion minimising a cost function associated with seismic mismatch between two or more seismic surveys.

Abstract: Disclosed is a method of modelling a subsurface volume, and a corresponding computer program and apparatus. The method comprises defining a regular planar grid of regularly arranged locations in the two dimensions substantially parallel to the surface, and calculating a plurality of one dimensional arrays, each one dimensional array extending from a different one of the regularly arranged locations, in the direction from surface to subsurface. Each of the one dimensional arrays comprises a plurality of one dimensional cells, wherein the cells are delineated according to actual geological features of the subsurface volume.

Abstract: Disclosed is a process for characterising the evolution of a reservoir that comprises non-horizontal layers, by analyzing the changes of at least the seismic amplitudes of seismic reflections. The process comprises the steps of providing a base survey of the reservoir with a set of seismic traces at a first time and providing a monitor survey of the reservoir, taken at a second time, with a set of seismic traces associated to the same positions as in the base survey. The sets of seismic traces from the base and monitor surveys are then inverted to obtain an estimate of the changes having occurred in the time interval between base and monitor surveys, the inversion being performed using seismic traces for which allowance is made for the actual propagation paths through the non-horizontal layers of the reservoir.