Schlumberger Technology Corporation

Japan National Oil Corporation

Michael Lynn Evans

Christian Stoller

Richard J Radtke

Jacques M Holenka

Robert A Adolph

Avtandil Tkabladze

John C Rasmus

Kenneth Edward Stephenson

William R Sloan

David L Best

Bradley Albert Roscoe

Benoit Couet

Charles Flaum

Jan Smits

Philip Lawrence Kurkoski

Patrick J Fisseler

Peter D Wraight

Keith A Moriarty

Darwin V Ellis

Wolfgang P Ziegler

Charles R Case

Marie-Laure Mauborgne

Paul Albats, Jr

William A Loomis

Didier Fouillou

Erik Rhein-Knudsen

W Robert Sloan

Luca Ortenzi

Sebastien Isambert

Lee Dolman

Jerome A Truax

Françoise Allioli

Ahmed Amine Mahjoub

Emmanuel Fayeulle

Avto Tkabladze

Najmud Dowla

S Zema Chowdhuri

Abhijeet Nayan

Loïc Vildé

Taesoo Kim

Nihal Ian Wijeyesekera

Ankur Prakash

A downhole tool operable for conveyance within a wellbore extending into a subterranean formation, and for obtaining one or more measurements of the subterranean formation, wherein the downhole tool comprises a sensor, a pressure housing containing the sensor and mounted on an external surface of the downhole tool, and a sliding stabilizer covering the pressure housing.

Sensor standoff

Systems, methods, and devices for determining a neutron-gamma density (NGD) measurement of a subterranean formation that is accurate in both liquid- and gas-filled formations are provided. For example, a downhole tool for obtaining such an NGD measurement may include a neutron generator, a neutron detector, two gamma-ray detectors, and data processing circuitry. The neutron generator may emit neutrons into a formation, causing a fast neutron cloud to form. The neutron detector may detect a count of neutrons representing the extent of the neutron cloud. The gamma-ray detectors may detect counts of inelastic gamma-rays caused by neutrons that inelastically scatter off the formation. Since the extent of the fast neutron cloud may vary depending on whether the formation is liquid- or gas-filled, the data processing circuitry may determine the density of the formation based at least in part on the counts of inelastic gamma-rays normalized to the count of neutrons.

Neutron-gamma density through normalized inelastic ratio

A method for determining a corrected neutron gamma density of a formation includes emitting neutrons into a formation using a neutron source to generate gamma-rays. Additionally, the method includes detecting a first count rate of gamma-rays and a gamma-ray spectrum using at least a gamma-ray detector of the downhole tool. The method also includes detecting a second count rate of neutrons using a neutron detector. The method includes using a processor to perform a gamma-ray spectroscopy analysis on the formation based on the gamma-ray spectrum and determining a correction based on results of the gamma-ray spectroscopy analysis. The method includes applying the correction to the first count rate or the second count rate and determining a neutron gamma density of the formation based on a first corrected count rate of gamma-rays or a second corrected count rate of neutrons. The method also includes outputting the determined density of the formation.

Neutron gamma density correction using elemental spectroscopy

Systems, methods, and devices for determining neutron-gamma density (NGD) measurement of a subterranean formation that is accurate in both liquid- and gas-filled formations are provided. For example, a downhole tool for obtaining such an NGD measurement may include a neutron generator, neutron detector, two gamma-ray detectors, and data processing circuitry. Neutron generator may emit neutrons into a formation, causing a fast neutron cloud to form. Neutron detector may detect a count of neutrons representing the extent of the neutron cloud. Gamma-ray detectors may detect counts of inelastic gamma-rays caused by neutrons that inelastically scatter off the formation. Since the extent of the fast neutron cloud may vary depending on whether the formation is liquid- or gas-filled, data processing circuitry may determine the density of the formation based at least in part on the counts of inelastic gamma-rays normalized to the count of neutrons.

A well-logging device may include a housing to be positioned within a larger borehole of a subterranean formation and thereby define a stand-off distance with respect to the larger borehole. The well-logging device may also include at least one radiation source carried by the housing to direct radiation into the subterranean formation, and radiation detectors carried by the housing in azimuthally spaced relation to detect radiation from the subterranean formation. The well-logging device may further include a controller to cooperate with the radiation detectors to determine at least one property of the subterranean formation corrected for the stand-off distance.

Well-logging apparatus including azimuthally spaced radiation detectors

Systems and methods identify and/or detect one or more features of a well casing by utilizing one or more downhole measurements obtainable by a downhole component. The one or more features of the well casing are identifiable and/or detectable from the one or more measurements associated with one or more properties of the one or more features of the well casing. The one or more measurements for indentifying and/or detecting a presence and/or a location of the one or more features of the well casing include sonic measurements, nuclear measurements, gamma ray measurements, photoelectric measurements, resistivity measurements and/or combinations thereof.

Identification of casing collars while drilling and post drilling using LWD and wireline measurements

A well-logging device may include a housing to be positioned within a borehole of a subterranean formation, and at least one radiation source carried by the housing to direct radiation into the subterranean formation. The well-logging device may also include noble gas-based radiation detectors carried by the housing in azimuthally spaced relation to detect radiation from the subterranean formation. A controller may determine at least one property of the subterranean formation based upon the detected radiation from the noble gas-based radiation detectors.

Well-logging apparatus including azimuthally-spaced, noble gas-based detectors

An apparatus can measure characteristics of a formation surrounding a borehole. The apparatus includes a tool body having a neutron measurement section and a density measurement section. The neutron measurement section includes a neutron source and a neutron detector arrangement spaced in an axial direction from the neutron source. The density measurement section includes a gamma ray source and a gamma ray detector arrangement spaced in an axial direction from the gamma ray source. The neutron measurement section and the density measurement section are positioned in the tool body so that the sections overlap in the axial direction and are azimuthally spaced apart in the tool body. The tool body also includes shielding to block a direct signal path from the neutron source to the gamma ray detector arrangement and to block a direct signal path from the gamma ray source to the neutron detector arrangement.

Apparatus and methods for measuring formation characteristics

Downhole drilling fluid measurements are made as a function of time or as a function of depth. A change in the downhole drilling fluid measurements is correlated to a feature of a formation penetrated by a drill bit or to a feature of fluids in the formation. The downhole drilling fluid measurements may include density, photoelectric factor, hydrogen index, salinity, thermal neutron capture cross section (Sigma), resistivity, slowness, slowing down time, sound velocity, and elemental composition. The feature may include fluid balance, hole-cleaning, a kick, a shallow water flow, a formation fluid property, formation fluid typing, geosteering, geostopping, or an environmental correction. A downhole system has a measurement-while-drilling tool or a logging-while-drilling tool and a processor capable of obtaining the downhole drilling fluid measurements and correlating the change in the downhole drilling fluid measurements.

Applications based on fluid properties measured downhole

A method of determining the density of an underground formation surrounding a borehole from measurement of gamma rays arising from irradiation of the formation by a nuclear source in a tool body located in the borehole, and measurement of gamma-ray flux in the tool body at two different detector spacings from the source, the method comprising determining a substantially straight-line relationship between gamma-ray flux measurements at each different spacing with respect to the density of the formation for a tool body with no standoff; determining a relationship defining the deviation with respect to tool standoff of the density determined from the measured gamma-ray flux measurements at the two different detector spacings from the density calculated from the straight line relationships; and for a given pair of gamma-ray flux measurements at the different detector spacings, determining the intersection of the relationship defining the deviation with the straight line relationship so as to indicate the density of the formation surrounding the bore-hole; wherein the source is a neutron source and the gamma rays measured in the too! body are neutron-induced gamma rays resulting from neutron irradiation of the formation.

Method of determining density of underground formations using neutron-gamma ray measurements

Systems, methods, and devices are provided to determine an accurate neutron-gamma density (NGD) measurement for a broad range of formations, including low-hydrogen-index or low-porosity formations and formations with heavy elements. For example, such an NGD measurement may be obtained by emitting neutrons into a formation such that some of the neutrons inelastically scatter off elements of the formation and generate inelastic gamma rays. The neutrons and inelastic gamma rays that return to the downhole tool may be detected. Some characteristics of certain formations are believed to affect the fast neutron transport of the formations. Thus, if a formation has one or more of such characteristics, a correction may be applied to the count rate of neutrons, the count rate of inelastic gamma rays, or the neutron transport correction function, upon which the neutron-gamma density (NGD) may be determined.

Correction for low porosity effects on neutron gamma density

A method and apparatus for obtaining neutron images of a rock formation are provided. The neutron images can be obtained from a tool in a logging-while-drilling system but which need not rotate to obtain neutron data from a plurality of azimuthal orientations.

Non-rotating logging-while-drilling neutron imaging tool

A downhole tool and method for determining a parameter of a formation as a function of radial distance from the borehole into the formation. The tool comprising a nuclear source for irradiating the formation and a plurality of sensors each independently measuring a density of the formation at a different radial depth into the formation. A processor combines the density measurements for determining the parameter of the formation as a function of radial distance.

Method and apparatus for determining formation and fluid properties

An apparatus can measure characteristics of a formation surrounding a borehole. The apparatus includes a tool body having a neutron measurement section. The neutron measurement section includes a neutron source and a neutron detector arrangement spaced in an axial direction from the neutron source The apparatus also includes a density measurement section having a gamma ray source and a gamma ray detector arrangement spaced in an axial direction from the gamma ray source. The neutron measurement section and the density measurement section are positioned in the tool body so that the sections overlap in the axial direction and are azimuthally spaced apart in the tool body. The tool body also includes shielding to block a direct signal path from the neutron source to the gamma ray detector arrangement and to block a direct signal path from the gamma ray source to the neutron detector arrangement.

A nuclear measurement tool for determining properties of a formation penetrated by a borehole fluid. The tool comprising: a nuclear source for irradiating the formation and a a plurality of nuclear sensors each operating with a different depth of investigation into the formation. The tool further comprising processing means for receiving the data from the nuclear sensors and based thereon determining the properties of the formation by taking into account the penetration of the borehole fluid.

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Missouri City, TX, United States of America

Michael Lynn Evans