The disclosed embodiments include systems and methods to assess geological data. The method includes obtaining data associated with a geological state of a geological entity. The method also includes assessing a nature of a geological age constraint of the geological entity. The method further includes generating a first probability distribution of a geological age of the geological entity based on the nature of the geological age constraint of the geological entity. The method further includes selecting a time of interest for analysis of the geological entity. The method further includes assessing a nature of the geological age constraint during the time of interest. The method further includes generating a second probability distribution for the time of interest. The method further includes determining a likelihood that the geological age constraint of the geological entity coincides with the time of interest.

The invention describes a procedure for determining the shale brittleness index from data obtained in the well by at least three well-logging tools measuring corresponding parameters. Three tools, namely sonic, density and deep resistivity, are selected. The time interval signals from the sonic tool are converted to the P-wave velocity. The product of signals obtained from the sonic and density tools (P-wave velocity×Bulk density=Acoustic impedance (AI)) responds in the same direction to a variation of the volume of water and organic matter (OM) volume of the rocks, whereas the third tool (Deep Resistivity) reacts very differently in response to a change of one or other of these same components, in a three-pole diagram, with rock matrix, OM and water as the three components onto an Acoustic Impedance vs resistivity ratio function plane. The resistivity ratio function is the square root of the ratio between the water resistivity and the measured formation resistivity. The position of the curved matrix-water line with OM=0 fraction by volume is fixed connecting the rock matrix point with that of the water point. The slope of the matrix-water curve is controlled by the tortuosity factor ‘a’ that is selected for a formation zone considering the pore structure, grain size and level of compaction. The data points to be analysed can be calibrated accordingly by iterating the resistivity of water (Rw) and occasionally the tortuosity factor (a) parameter to obtain the Rw value. In a graph where the parameters used depend, for example, on the sonic velocity in the rock, the rock bulk density and on the electric resistivity of the formations, the iso quartz/calcite-content lines are denoted as iso-brittleness line as with an increase in quartz/calcite content, both organic content and porosity decrease, resulting in an increase in brittleness. These iso-brittleness lines form a set of parallel curved lines intersecting the matrix-water reference curved line. Brittleness is derived from that graph corresponding to each pair of values of the parameters measured in the well.

An x-ray based litho-density tool for measurement of formation surrounding a borehole is provided, the tool including at least an internal length comprising a sonde section, wherein said sonde section further comprises an x-ray source; at least one radiation measuring detector; at least one source monitoring detector; a plurality of sonde-dependent electronics; and a reference detector, wherein the reference detector is used to monitor the output of the x-ray source such that the reference detector's output effects corrections to the outputs of the detectors used to measure the density of the materials surrounding the borehole in order to correct for variations in the x-ray source output. Tool logic electronics, PSUs, and one or more detectors used to measure borehole standoff such that other detector responses may be compensated for tool standoff are also provided. Shielding, through-wiring, wear-pads that improve the efficacy and tool functionality are also described and claimed.

An information processing system having a processor and a memory device coupled to the processor, wherein the memory device includes a set of instruction that, when executed by the processor, cause the processor to receive a multi-dimensional grid of acoustic or elastic impedances determined from seismic survey data associated with a subterranean formation, receive elastic property data that describes elastic property characteristics used to sort pseudo-components, and wherein the respective pseudo-components are formed of a combination of two or more lithologies. The instructions, when executed by the processor, further cause the processor to define select design variables using the impedance arrays, perform optimization operations for optimizing select design variables by applying the elastic property data as a part of a constitutive relation, and output a distribution of the pseudo-components to characterize volumetric concentrations of spatially grouped lithologies in a control volume of the subterranean formation.

A computer-implemented method, and system implementing the method, are disclosed for computing a final model of elastic properties, using nonlinear direct prestack seismic inversion for Poisson impedance. User inputs and earth-model data is obtained over points of incidence of a survey region, at various angles of incidence. Various models are then computed that serve for lithology identification and fluid discrimination and take part in preliminary seismic exploration and reservoir characterization. Therefore, further refinement of these models is required due to changes in burial depths, compaction and overburden pressure, as they provide limitations for reservoirs on porous media. The further refinement using nonlinear direct prestack seismic model is performed on a system computer, which produces a final model of elastic properties. This model can then be applied for lithology prediction and fluid detection to identify potential targets of oil and gas exploration and estimating spots in unconventional shale gas applications.

Methods, systems, and computer program products for characterizing materials in a wellbore having multiple casing strings uses well completion data and instantaneous frequency, instantaneous phase, and/or amplitude attributes, including waveform amplitude or instantaneous amplitude, of an acoustic waveform to determine material densities, acoustic velocities and acoustic travel distances for the materials between the various stages of casings.

An acoustic logging method that may comprise acquiring waveforms for multiple acoustic wave modes as a function of tool position in a borehole; deriving position-dependent mode dispersion curves from the waveforms; accessing a computed library of dispersion curves for a vertical shear slowness (s) and a Thomsen gamma () of a given acoustic wave mode as a function of frequency; interpolating dispersion curves in the computed library to an assumed known compressional wave slowness, a borehole radius, a formation density, a mud density, and a mud slowness; computing an adaptive weight; and inverting dispersion curve modes jointly for a shear wave anisotropy, a vertical shear wave slowness, an inverted mud slowness, and an inverted mud density as a function of depth. An acoustic logging system may comprise a logging tool, a conveyance attached to the logging tool, at least one sensor, and at least one processor.

Mapping is performed of chemostratigraphic signatures of hydrocarbon reservoirs in three dimensions. Up-scaled chemostratigraphic data from well cuttings and well cores are tied with high-resolution elastic wireline data at well locations in the reservoir. The wireline data is used to determine suitable seismic attributes for mapping the desired chemostratigraphic property, and are obtained by performing pre- and/or post-stack inversions. A multi-attribute template, derived from the well data, is developed to characterize the reservoir in terms of its chemostratigraphic properties. The seismic data is then inverted to map the chemostratigraphic signatures of reservoir in three dimensions.

Processes and systems described herein are directed to performing marine surveys with marine vibrators that emit orthogonal coded pseudo-random sweeps. In one aspect, coded pseudo-random signals are generated based on coded pseudo-random sequences. The coded pseudo-random sequences are used to activate the marine vibrators in a body of water above a subterranean formation. The activated marine vibrators generate orthogonal coded pseudo-random sweeps. A wavefield emitted from the subterranean formation in response to the orthogonal coded pseudo-random sweeps is detected at receivers located in a body of water. Seismic signals generated by the receivers may be cross-correlated with a signature of one of the orthogonal coded pseudo-random sweeps to obtain seismic data with incoherent residual noise.

Described embodiments generally relate to a method of determining parameters of VTI anisotropy of a subsurface shale formation. The method comprises receiving wireline log data relating to the subsurface formation, the data comprising density and a clay content indicator; identifying at least one layer of shale in the subsurface formation based on the wireline log data; calculating porosity, clay fraction and silt fraction based on the wireline log data; calculating an orientation distribution function (ODF) of clay platelets within the at least one layer of shale based on the clay fraction and porosity data; estimating at least three independent anisotropy parameters based on the ODF, porosity and silt fraction, the at least three anisotropic parameters comprising a shear wave anisotropy parameter; comparing the estimated shear wave anisotropy parameter with a measured shear wave anisotropy parameter determined based on the sonic log data; upon determining that the estimated shear wave anisotropy parameter is different from the measured shear wave anisotropy parameter by more than a threshold amount, determining parameters of best fit to minimise the difference between the estimated shear wave anisotropy parameter and the measured shear wave anisotropy parameter; adjusting the estimated anisotropy parameters based on the parameters of best fit; and outputting the adjusted anisotropy parameters.