Schlumberger Technology Corporation

Michael M Herron

Susan L Herron

James A Grau

Ridvan Akkurt

Mary Ellen Loan

Kenneth Edward Stephenson

Robert Freedman

Andrew Emil Pomerantz

Bradley Albert Roscoe

Ronald E G Van Hal

Andrew Speck

Jeffrey S Schweitzer

Paul Ryan Craddock

Michael G Supp

Richard Douglas Averitt

John Paul Horkowitz

Vivek Anand

A Ballard Andrews

Robert Allen Badry

Christian Straley

Abigail Matteson

Dale May

Logan Chieffo

Alyssa Charsky

The disclosure relates to a method for analyzing earth samples of a geological formation, comprising:

Method and system for analyzing an earth sample of a geological formation

Oil-based mud cuttings are cleaned of drilling fluid and mud additives. After sorting and rinsing the cuttings with diesel, the cuttings are put in a syringe, which is repeatedly filled and emptied of diesel. The cuttings are then washed in the syringe with pentane. The cuttings are then crushed and exposed to a solvent a second time. Instead of placing the cuttings in the syringe, alternatively, the cuttings remain on a sieve and the syringe is used to spray the cuttings with diesel, followed by pentane.

Oil-based mud drill cutting cleaning for infrared spectroscopy

A method for determining mineralogy of a formation includes determining a model of arenites in the formation by performing a first type of linear regression on a plurality of elemental dry weights of the formation based upon a sum of elemental dry weights of calcium and magnesium being at least a given value, or performing a second type of linear regression on the elemental dry weights based upon the sum of the elemental dry weights of elemental calcium and magnesium being less than the given value. A model of arkoses in the formation is determined by performing a third type of linear regression on the elemental dry weights. A partitioning function is then determined. The mineralogy of the formation is then determined by applying the partitioning function to the model of arenites and the model of arkoses, and adding the model of arenites and the model of arkoses together.

Determining mineralogy of an earth formation using linear regressions

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. Here, the principles of the method and the main challenges are described, and calculations that explore uncertainties in the saturation estimates arising from uncertainties in the log inputs are presented. The statistical uncertainty in the estimate of hydrocarbon saturation is as good as 10 saturation units (s.u.) in conventional reservoirs with porosities of 15 porosity units (p.u.) or greater. The method has been applied to the determination of hydrocarbon saturation in a variety of formations, including bitumen-filled dolomite, heavy oil sand, and shaly-sands with both open hole and cased hole wells. The method works equally well in formations drilled and logged with either oil- and water-based mud. The saturation estimates have been benchmarked against a combination of conventional and new logging approaches (e.g., resistivity, magnetic resonance and dielectric logs) and core measurements, with generally excellent agreement among independent determinations. Hydrocarbon saturations can be determined accurately using the method in a number of formation types where conventional methods and models for estimating fluid saturation commonly fail, such as freshwater and unknown water salinity in formations under enhanced oil recovery. The case studies included herein demonstrate that a TOC log derived from geochemical spectroscopy logs can be used to obtain reliable estimates of hydrocarbon saturation in a wide range of environmental conditions and formations.

Hydrocarbon saturation from total organic carbon logs derived from inelastic and capture nuclear spectroscopy

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.

Predicting mineralogy properties from elemental compositions

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.

System and method of determining rock properties using terahertz-band dielectric measurements

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).

Diffuse reflectance infrared fourier transform spectroscopy for characterization of earth materials

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.

Methods and apparatus for exploring geological formations utilizing strontium measurements

Methods and apparatus are provided for determining the content of a first element in a formation which cannot otherwise be determined via a capture spectrum measurement. The methods and apparatus utilize the inelastic spectrum measurement of the first element and the inelastic and capture spectrum measurements of at least a second element. The methods and apparatus have particular application to determining the carbon content of a formation although they are not limited thereto. The inelastic and capture spectrum measurements of silicon are useful in making such determinations, although other chemical elements may be used as the second element.

Methods and apparatus using both nuclear capture and inelastic spectroscopy in deriving elemental concentrations

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&#x2014;bound fluid volume). This method also allows for improved estimation of irreducible water saturation of a carbonate formation using the ratio of kand (e&#x3c6;+k). Likewise, the bound fluid volume of a carbonate formation may be determined using the ratio of &#x3c6;kand (e&#x3c6;+k). In these relationships, e, x, and f are constants according to the following relationships e=x, f=bc+1, x is between 1 and 100 mD (preferably 10 mD).

Carbonate permeability

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.

Method of using nuclear spectroscopy measurements acquired while drilling

Petrophysical property estimation using an acoustic calibration relationship

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. Other aspects of the invention involve making a plurality of different measurements of a subsurface formation, including measuring indicators of a plurality of absolute or relative formation elemental concentrations; processing the measurements to determine a plurality of parameters associated with the subsurface formation, and determining either net pay intervals or drilling parameters using these formation parameters and either interval acceptance criteria or desired wellbore criteria, respectively.

Real time petrophysical evaluation system

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. The estimate can also be made from mineralogy data where each mineral is assumed to have a fairly constant specific surface area.

Method of determining the permeability of sedimentary strata

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.

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Ridgefield, CT, United States of America

Michael M Herron