Schlumberger Technology Corporation

David Rose

Christian Stoller

Tong Zhou

Sicco Beekman

Jeffrey Miles

Kenneth Edward Stephenson

Richard J Radtke

Avtandil Tkabladze

James Leslie Thornton

Libo Yang

Onur Ozen

Adil Busaidy

Reza Taherian

Dean M Homan

James A Grau

Matthieu Simon

John J Simonetti

Paul Wanjau

Donna Simonetti

Ashish Datey

ZhanGuo Shi

Pascal Millot

Gustavo Dip

Heri Tanjung

Yevgeniy Karpekin

Richard Radtke

Laurent Mosse

Systems and method presented herein enable the estimation of porosity using neutron-induced gamma ray spectroscopy. For example, the systems and methods presented herein include receiving, via a control and data acquisition system, data relating to energy spectra of gamma rays captured by one or more gamma ray detectors of a neutron-induced gamma ray spectroscopy logging tool. The method also includes deriving, via the control and data acquisition system, one or more spectral yields relating to one or more elemental components from the data relating to the energy spectra of the gamma rays. The method further includes estimating, via the control and data acquisition system, a measurement of porosity based on the one or more spectral yields relating to the one or more elemental components.

Porosity measurements from nuclear spectroscopy

A method for determining the gas pressure may include generating, via a downhole tool, neutron radiation in a cased wellbore of a geological formation and measuring a response to the neutron radiation. The method may also include determining, via a processor, at least one of a sigma, a neutron porosity, or a fast-neutron cross-section of the formation. Additionally, an equation of state of the gas may be estimated, and a gas pressure of the gas may be determined by solving a relationship, based at least in part on the equation of state, between the gas pressure and the at least one of the sigma, the neutron porosity, or the fast-neutron cross-section.

Gas pressure measurement within cased wellbore systems and methods

A presence of cement may be identified based on a downhole tool that may emit neutrons into a wellbore having at least one cement casing. The neutrons may interact with the particular material via inelastic scattering, inelastic neutron reactions, capture of neutrons and/or neutron activation through one of these reactions and cause a material to emit an energy spectrum of gamma rays, and wherein the downhole tool is configured to detect an energy spectrum of the gamma rays that is specific to at least one of a plurality of elements and associated a region within the wellbore. An amount of elements, such as calcium and silicon, may be determined from the gamma ray spectra that may indicate a present of cement within the wellbore.

Systems and methods for determining the presence of cement behind at least one casing using spectroscopy measurement

Elemental concentrations in subterranean formations may be determined using neutron spectroscopy. For example, neutrons may be emitted by a downhole tool into the formation and produce gamma rays via inelastic scattering of fast neutrons or capture of slow neutrons. The borehole surrounding a downhole tool may introduce artifacts in the neutron spectroscopy measurement. Embodiments of the present disclosure are directed to techniques that reduce artifacts signals in downhole tools that include one or multiple detectors based at least in part on the inelastic and capture measurements.

Compensated spectroscopy measurements

The present disclosure describes a downhole tool including an electrically operated radiation generator that selectively output radiation to a surrounding environment based at least in part on supply of electrical power; and a control system that determines likelihood of exposing living beings in the surrounding environment to output radiation by determining whether one or more check conditions is met; determine that each of the one or more check conditions is met before instructing the electrically operated radiation generator to output radiation; and instruct the electrically operated radiation generator to cease output of radiation when at least one of the one or more check conditions is no longer met.

Control of electrically operated radiation generators

Systems, methods, and devices for inelastic gamma-ray logging are provided. In one embodiment, such a method includes emitting neutrons into a subterranean formation from a downhole tool to produce inelastic gamma-rays, detecting a portion of the inelastic gamma-rays that scatter back to the downhole tool to obtain an inelastic gamma-ray signal, and determining a property of the subterranean formation based at least in part on the inelastic gamma-ray signal. The inelastic gamma-ray signal may be substantially free of epithermal and thermal neutron capture background.

Optimization of neutron-gamma tools for inelastic gamma-ray logging

A method for determining a fractional volume of at least one component of a formation includes entering into a computer a number of detected radiation events resulting from imparting neutrons into the formation at an energy level of at least 1 million electron volts (MeV). The detected radiation events correspond to at least one of an energy level of the imparted neutrons and thermal or epithermal energy neutrons. A measurement of at least one additional petrophysical parameter of the formation is made. The at least one additional petrophysical parameter measurement and at least one of a fast neutron cross-section and a thermal neutron cross-section determined from the detected radiation events are used in the computer to determine the fractional volume of the at least one component of the formation. In another embodiment, the fast neutron cross-section and the thermal neutron cross-section may be used on combination to determine the fractional volume.

Method for using neutron interaction cross section to interpret neutron measurements

A method for evaluating wellbore conduit condition includes using measurements of at least one of (i) inelastic gamma rays made during emission a burst of neutrons into the conduit from within the conduit at at least one spaced apart location from a position of the emission and (ii) epithermal neutrons or capture gamma rays therefrom detected at at least two spaced apart locations from the position of the emission within a selected time after the emission. The at least one of the measurements of inelastic gamma rays and epithermal neutron or capture gamma ray counts are characterized to estimate an amount of loss of iron in the conduit.

Casing inspection using pulsed neutron measurements

Optimization of neutron-gamma tools for inelastic-gamma ray logging

A method for well logging includes emitting a plurality of bursts of high energy neutrons into a wellbore and formations surrounding the wellbore. During and for a selected duration after at least one of the plurality of bursts, gamma rays are detected at at least one location spaced apart from the emitting and characterizing an energy of the detected gamma rays. After the last burst, gamma rays are detected and energy spectrum and rates of detection with respect to time thereof are determined. The foregoing is repeated for a selected number of times. After the selected number of times background gamma rays are measured. At least one of the numbers of detected gamma rays during a selected time interval and an energy spectrum of the detected gamma rays during the selected time interval is used to determine selected formation properties.

Pulsed neutron well logging method for determining multiple formation parameters

A tool having a neutron source, a gamma ray detector, and a photomultiplier tube is provided. The gamma ray detector and the photomultiplier tube are at least partially surrounded by a layer of boron. The tool is used to make measurements, and the number of prompt gamma rays emitted by the boron is determined from the measurements. The number of neutrons detected may be inferred using the determined number of prompt gamma rays. The tool may also have a layer of neutron absorbing material different from boron or a layer of heavy metal at least partially surrounding the boron. The tool may be a logging tool used to delineate a porous formation and to determine its porosity. The tool may have a plurality of gamma ray detector/photomultiplier tube pairs and those pairs may be used to determine a formation hydrogen index and/or a borehole hydrogen index.

Neutron detection using a shielded gamma detector

A method for pulsed neutron well logging of a subsurface formation, includes irradiating the formation with a plurality of bursts of neutrons of a group of selected durations; detecting gamma rays resulting from interaction of the neutrons during a group of selected time gates which contains at least some early and late gamma ray counts. The gamma rays are detected at at least two axially spaced apart locations from a position of the irradiating. A weighted sum of the numbers of gamma rays detected in each of the time gates is calculated. A ratio of the weighted sum of detected gamma rays at a first axial spacing to the weighted sum at a second axial spacing is determined. The ratio is used to determine a hydrogen index of the subsurface formation.

Growing community of inventors

Sugar Land, TX, United States of America

David Rose