Baker Hughes Corporation

Weatherford Technology Holdings, LLC

Western Atlas International, Inc.

Richard R Pemper

Xiaogang Han

Gregory J Schmid

Pingjun Guo

Brian J LeCompte

Alfred I Khisamutdinov

Darrell Dolliver

Daniel T Georgi

Randy Gold

David J Jacobi

Paul James Wilson

Darryl E Trcka

Philip Lawrence Kurkoski

W Allen Gilchrist, Jr

John Longo

Andrew Kirkwood

Natasa Mekic

Donald C McKeon

Anton Nikitin

James E Brewer

Freddy Mendez

Alexandr A Vinokurov

William Madigan

Gary A Feuerbacher

Mikhail A Fedorin

Guojing Hou

Enrique J Prati

Izhar Ahmad

Methods, tools, and systems for determining porosity in an earth formation are disclosed. Neutrons are emitted into the formation to induce inelastic scattering gamma rays and thermal capture gamma rays in the formation. The induced gamma rays are detected at a proximal gamma detector and a far gamma detector, which are spaced at different axial distances from the neutron source. A measured proximal-to-far inelastic ratio (a ratio of inelastic scattering gammas detected at the proximal and far detector) and a proximal-to-far thermal capture ratio (a ratio of thermal capture gammas detected at the proximal and far detector) are determined and used to calculate the formation porosity. Techniques are disclosed for removing borehole and casing configuration effects from the measured proximal-to-far thermal capture ratio, leaving only porosity dependence.

Borehole compensation during pulsed-neutron porosity logging

Methods, tools, and systems for determining the lithium concentration of a formation traversed by a wellbore using pulsed neutron logging are described. Since determining lithium directly using pulsed neutron logging is problematic, this disclosure provides ways of determining lithium concentration indirectly using models that relate lithium concentration with concentrations of other elements that are predicted to be associated with lithium.

Pulsed neutron logging for petrolithium

Methods and systems for determining the elemental composition of formation rock are disclosed. The systems include a pulsed-neutron geochemical logging tool that is conveyed in a borehole traversing the formation. The pulsed-neutron geochemical logging tool can collect inelastic and capture neutron spectra. The inelastic and capture spectra are processed to provide the elemental composition of formation rock after removing contributions due to elements in the borehole and in the pores of the formation.

Determination of elemental concentrations from the capture and inelastic energy spectra

Systems and methods for determining the composition of an earth formation are disclosed. One or more spectra that correspond to gamma radiation that is detected at each of multiple depths in a wellbore are generated, the contributions of each of multiple detection elements to the one or more spectra are determined, and the weight fractions of each of multiple compounds that are associated with the detection elements are calculated. The weight fraction calculations are based on a number density ratio value for the compound's associated detection element, which allows the weight fraction to be calculated directly from the contribution of the compound's associated detection element without a normalization factor.

Techniques for determining formation composition from measured nuclear spectra

A neutron logging tool has multiple detectors spaced about the circumference of the tool. The detectors are shielded from each other such that each detector detects gamma rays from the area of the borehole and formation to which it is closest. The log readings from each detector can be associated with the orientation of that detector. The orientation-specific log readings can then be aggregated to form an azimuthal log which can be used to analyze pre-fractured and/or post-fractured formations.

Neutron logging tool with multiple detectors

An instrument for performing measurements downhole includes: at least one gamma-ray detector with azimuthal sensitivity equipped for discriminating energy of incident gamma-rays. This instrument is equipped with or without a neutron or gamma-ray source. A method and computer program product providing the azimuthal sensitivity of the instrument is provided.

Gamma ray detectors having azimuthal sensitivity

A method for estimating a lithotype of an earth formation, the method includes: obtaining at least two different energy spectra of radiation received from the earth formation using the logging tool, each energy spectrum having at least one of a natural gamma-ray spectrum, a fast neutron-induced inelastic spectrum, and a thermal neutron induced capture spectrum; establishing at least one geochemically-based constraint related to elemental spectral yields to be determined; determining the elemental spectral yields from the at least two different energy spectra by decomposing the at least two different energy spectra over weighted sum of monoelemental standards wherein at least one weight is constrained by the at least one geochemically-based constraint and each weight represents a proportion of one monoelemental standard; converting the elemental spectral yields to elemental concentrations; and using a classifier to receive the elemental concentrations as input and to provide a lithotype as output.

Use of chemically and geologically consistent constraints for obtaining elemental chemistry downhole

Measurements made by a natural gamma ray tool are used to provide an elemental composition of an earth formation. Additional measurements made with a pulsed neutron tool with two or more gamma ray detectors are used to provide a mineralogical and/or elemental image of the formation. This may be used in reservoir navigation and in furthering the understanding of the geology of the prospect.

Azimuthal elemental imaging

A method for estimating resistivity of a formation includes: selecting spectra collected by pulsed neutron instrument disposed down a wellbore traversing the formation, the spectra including capture interactions and inelastic interactions; deconvolving the spectra to estimate an elemental yield; converting the elemental yield to a total concentration value; subtracting a concentration value for drilling mud and a concentration value for the formation from the total concentration value to estimate a concentration in fluid within the formation; and converting the fluid concentration value to a resistivity value. A computer program product and an instrument are provided.

Method for determining formation water resistivity from a wireline pulsed neutron device

A method for estimating information about a formation, the method including obtaining a first set of radiation data substantially influenced by the formation and non-formation materials; obtaining a second set of radiation data substantially influenced by the non-formation materials; and correcting the first set of radiation data with the second set of radiation data to provide corrected formation radiation data.

Compensated mineralogy tool and processing

A method for correcting data collected with a neutron emitting instrument, includes: obtaining characterization data for the instrument, the characterization data including inelastic background data of the instrument; and correcting the collected data according to the characterization data. A computer program product and an instrument are provided.

Inelastic background correction for a pulsed-neutron instrument

Elemental analysis of an earth formation (including Aluminum) is obtained using measurements from a gamma ray logging tool. The inelastic spectrum of Aluminum is determined from measurements made in a water tank. From the elemental analysis, an estimate of the mineralogy of the formation is made treating the problem as one of Linear Programming (maximizing an objective function subject to equality and/or inequality constraints.

Method and apparatus for determining aluminum concentration in earth formations

Elemental analysis of an earth formation is obtained using measurements from a gamma ray logging tool. From the elemental analysis, an estimate of the mineralogy of the formation is made treating the problem as one of Linear Programming (maximizing an objective function subject to equality and/or inequality constraints).

Elemental gamma ray signature instrument

An apparatus and method for detecting the location of subsurface markers in a formation proximate to a borehole. The apparatus includes marker detectors in a housing having at least two housing sections attached in an initial orientation. The distance between the detectors is measured under controlled conditions with a calibration bar. The initial attached orientation between the housing sections is identified with a calibrator, and deviations from the initial attached orientation are identified by the calibrator after the housing sections are detached and reattached. The calibrator permits well site corrections to be made to the housing sections without recalibration. Gauges permit corrections for temperature and pressure fluctuations, and the corrected distances between the housing detectors is computed. Detectors in the housing generate signals when each detector is proximate to a marker in the formation, and such signals can be processed to identify the elevation of a marker in the borehole, or the distance between markers in the borehole, to determine formation compaction or settlement. In an apparatus having two detectors separated by a spacer, flexible retainers can be positioned between each detector and the spacer to permit thermal expansion or contraction of the detectors relative to the spacer.

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Sugar Land, TX, United States of America

Richard R Pemper