Abstract: The accurate determination of formation hydrocarbon or water saturation is a useful step in the petrophysical evaluation of petroleum reservoirs. This disclosure presents a new method for estimating hydrocarbon saturation directly from a porosity log and a total organic carbon (TOC) log. The method is enabled by the recent development of a geochemical spectroscopy logging tool that combines inelastic and capture gamma ray measurements to provide a robust and accurate TOC log. The method differs from the prior approach of using carbon-to-oxygen ratios that is most often applied in cased hole evaluation. The main advantages of this method are that it does not use knowledge of formation water resistivity, it does not rely on a resistivity model, it does not use an extensive calibration database, and it is largely independent of clay or other lithology effects.

Abstract: A method for predicting at least one property of a geological formation may include generating mapping function values relating a plurality of reference elemental compositions to corresponding reference properties thereof based upon at least one non-linear mapping function. The method may further include determining a sample elemental composition of at least one sample associated with the geological formation and performing, using a processor, an interpolation to map the sample elemental composition to at least one sample property based upon the mapping function values and the at least one non-linear function.

Abstract: A method of analyzing physical properties of a sample includes obtaining the sample and obtaining an electromagnetic spectrum of the sample using terahertz spectroscopy. A sample complex permittivity is computed from the electromagnetic spectrum of the sample. The method further includes estimating the constituents and the constituent fractions and computing an estimated effective complex permittivity based upon a model and the constituent fractions. The method further includes comparing the computed sample complex permittivity with the estimated effective complex permittivity in order to determine the physical properties the sample.

Abstract: The subject disclosure relates to the evaluation of lithology, mineralogy and organic content of earth materials. More particularly, the subject disclosure relates to evaluating lithology, mineralogy and organic content of earth materials using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).

Abstract: Systems and methods are described for analyzing hydrocarbon bearing earth samples to determine information indicating the maturation, or changes in composition of kerogen from original deposition over geologic time as the kerogen is subjected to heat and pressure. A DRIFTS spectrometry signal is corrected and normalized and then plotted against TOC data to obtain an index indicating thermal maturity.

Abstract: The accurate determination of formation hydrocarbon or water saturation is a useful step in the petrophysical evaluation of petroleum reservoirs. This disclosure presents a new method for estimating hydrocarbon saturation directly from a porosity log and a total organic carbon (TOC) log. The method is enabled by the recent development of a geochemical spectroscopy logging tool that combines inelastic and capture gamma ray measurements to provide a robust and accurate TOC log. The method differs from the prior approach of using carbon-to-oxygen ratios that is most often applied in cased hole evaluation. The main advantages of this method are that it does not use knowledge of formation water resistivity, it does not rely on a resistivity model, it does not use an extensive calibration database, and it is largely independent of clay or other lithology effects.

Abstract: A method of analyzing physical properties of a sample includes obtaining the sample and obtaining an electromagnetic spectrum of the sample using terahertz spectroscopy. A sample complex permittivity is computed from the electromagnetic spectrum of the sample. The method further includes estimating the constituents and the constituent fractions and computing an estimated effective complex permittivity based upon a model and the constituent fractions. The method further includes comparing the computed sample complex permittivity with the estimated effective complex permittivity in order to determine the physical properties the sample.

Abstract: A method for predicting at least one property of a geological formation may include generating mapping function values relating a plurality of reference elemental compositions to corresponding reference properties thereof based upon at least one non-linear mapping function. The method may further include determining a sample elemental composition of at least one sample associated with the geological formation and performing, using a processor, an interpolation to map the sample elemental composition to at least one sample property based upon the mapping function values and the at least one non-linear function.

Abstract: The subject disclosure relates to the evaluation of lithology, mineralogy and organic content of earth materials. More particularly, the subject disclosure relates to evaluating lithology, mineralogy and organic content of earth materials using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).

Abstract: Formation strontium concentrations are measured utilizing a borehole tool. A log may be provided as a function of depth or distance. The strontium measurements can be correlated chronostratigraphically to provide a depth to absolute time correlation. Measures of strontium made in the borehole can be correlated to information obtained via seismic exploration of the formation traversed by the borehole. Measures of strontium in multiple boreholes of a single formation can be correlated.

Abstract: Formation strontium concentrations are measured utilizing a borehole tool. A log may be provided as a function of depth or distance. The strontium measurements can be correlated chronostratigraphically to provide a depth to absolute time correlation. Measures of strontium made in the borehole can be correlated to information obtained via seismic exploration of the formation traversed by the borehole. Measures of strontium in multiple boreholes of a single formation can be correlated.

Abstract: A modification to the Coates-Timur relationship to produce a more coherent relationship applicable to carbonate formations is disclosed. In this method, permeability may be determined using porosity and the ratio of bound fluid volume to (1—bound fluid volume). This method also allows for improved estimation of irreducible water saturation of a carbonate formation using the ratio of kc and (e?f+kc). Likewise, the bound fluid volume of a carbonate formation may be determined using the ratio of ?kc and (e?f+kc). In these relationships, e, x, and f are constants according to the following relationships e=xc, f=bc+1, x is between 1 and 100 mD (preferably 10 mD).

Abstract: A method of using nuclear spectroscopy measurements acquired while drilling a subsurface formation including: measuring indicators of a plurality of absolute or relative formation elemental concentrations; processing the measurements to determine a petrophysical parameter associated with the subsurface formation while drilling, and using the petrophysical parameter to determine a drilling parameter. The petrophysical parameter may include, for instance, the permeability of the subsurface formation and the drilling parameter may include, for instance, a change in the orientation of a directional drilling assembly or the point at which to stop drilling. The invention further involves an apparatus adapted to carry out the inventive method.

Abstract: A method of estimating a petrophysical property of a subsurface area that includes deriving an acoustic calibration relationship correlating acoustic propagation characteristics of a first subsurface area with a petrophysical property of the first subsurface area determined using nuclear spectroscopy measurements; processing acoustic data acquired from a second subsurface area to determine acoustic propagation characteristics associated with a plurality of regions within the second subsurface area; and estimating the petrophysical property of the regions within the second subsurface area using the calibration relationship and the acoustic propagation characteristics associated with the second subsurface area.

Abstract: A method of estimating a petrophysical property of a subsurface area that includes deriving an acoustic calibration relationship correlating acoustic propagation characteristics of a first subsurface area with a petrophysical property of the first subsurface area determined using nuclear spectroscopy measurements; processing acoustic data acquired from a second subsurface area to determine acoustic propagation characteristics associated with a plurality of regions within the second subsurface area; and estimating the petrophysical property of the regions within the second subsurface area using the calibration relationship and the acoustic propagation characteristics associated with the second subsurface area.

Abstract: A method of using nuclear spectroscopy measurements acquired while drilling a subsurface formation including: measuring indicators of a plurality of absolute or relative formation elemental concentrations; processing the measurements to determine a petrophysical parameter associated with the subsurface formation while drilling, and using the petrophysical parameter to determine a drilling parameter. The petrophysical parameter may include, for instance, the permeability of the subsurface formation and the drilling parameter may include, for instance, a change in the orientation of a directional drilling assembly or the point at which to stop drilling. The invention further involves an apparatus adapted to carry out the inventive method.

Abstract: A subsurface formation petrophysical evaluation method including: determining formation porosity and permeability using a quantitative indication of formation composition; estimating water-filled formation resistivity using the formation porosity; associating differences between measured formation resistivity and estimated water saturated formation resistivity with the presence of subsurface hydrocarbons; and estimating irreducible formation water saturation using the formation porosity and the formation permeability. The invention further involves an apparatus adapted to carry out the inventive method.

Abstract: A subsurface formation petrophysical evaluation method including: determining formation porosity and permeability using a quantitative indication of formation composition; estimating water-filled formation resistivity using the formation porosity; associating differences between measured formation resistivity and estimated water saturated formation resistivity with the presence of subsurface hydrocarbons; and estimating irreducible formation water saturation using the formation porosity and the formation permeability. The invention further involves an apparatus adapted to carry out the inventive method.

Abstract: A permeability estimator is constructed from the lambda parameter, .LAMBDA., which is the size of dynamically connected pores. For simple pore geometries at high permeabilities, .LAMBDA. should theoretically be proportional to the pore volume-to-surface area ratio. Further, at high permeabilities, the permeability is proportional to .LAMBDA..sup.2 /F where F is the formation factor. Core data are used to establish the proportionality constant. At permeabilities less than about 100 md, the estimated permeability is seen to overestimate the actual permeability by a factor related to the estimate. Thus, a corrected second estimate can be readily made and is shown to match measured permeabilities on a diverse set of sands and shaly sands with a correlation coefficient of 0.89 for log k. The estimate can also be made using NMR relaxation time data with a correlation coefficient of 0.92 for the same data set.

Abstract: There is provided a method of accurately estimating the permeability of sedimentary rock formations from well logging data. The method involves a short relaxation time strategy with the identification of the key k-Lambda parameter S/V.sub.p, which is the surface-to-pore ratio. The inverse of T.sub.2 is related to this ratio by the surface relaxivity, .rho.2. The k-Lambda estimator is given by: ##EQU1## where: .DELTA.V.sub.1 represents the volume elements of the T.sub.2 distribution and the sum over i=1 to n represents some set of early to later volume elements; and V.sub.p is the total pore volume.