Schlumberger Technology Corporation

Schlumberger Technology Center

Services Petroliers Schlumberger

Schlumberger Holdings Limited

Prad Research and Development Limited

Kenneth Edward Stephenson

Bradley Albert Roscoe

John Barry Fitzgerald

Christian Stoller

Wolfgang P Ziegler

Peter D Wraight

James A Grau

Matthieu Simon

Anthony Robert Holmes Goodwin

Avtandil Tkabladze

Robert L Kleinberg

Lalitha Venkataramanan

Michael Lynn Evans

Gary Martin Oddie

Jani Petteri Reijonen

Douglas D Griffin, Ii

Markus Berheide

Zilu Zhou

Gerald Henry Meeten

David Rose

Frederic Gicquel

Irina Molodetsky

Sarah Elizabeth Pelham

Andrew Bazarko

Terizhandur S Ramakrishnan

Bhavani Raghuraman

Keith A Moriarty

Benoit Couet

Joel Lee Groves

Michael M Herron

Roger Griffiths

Jeffrey S Schweitzer

Susan L Herron

John J Simonetti

Philippe Salamitou

Jacques M Holenka

Jose Navarro

Paul Albats, Jr

William A Loomis

William R Sloan

Roman Korkin

Donna Simonetti

Jerome A Truax

S Zema Chowdhuri

John William James Ferguson

John W J Ferguson

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

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

Methods and related systems are described for gamma-ray detection. A gamma-ray detector is made depending on its properties and how those properties are affected by the data analysis. Desirable properties for a downhole detector include; high temperature operation, reliable/robust packaging, good resolution, high countrate capability, high density, high Z, low radioactive background, low neutron cross-section, high light output, single decay time, efficiency, linearity, size availability, etc. Since no single detector has the optimum of all these properties, a downhole tool design preferably picks the best combination of these in existing detectors, which will optimize the performance of the measurement in the required environment and live with the remaining non-optimum properties. A preferable detector choice is one where the required measurement precision (logging speed) is obtained for all of the required inelastic elements and/or minimization of unwanted background signals that complicate the data analysis.

Gamma-ray detectors for downhole applications

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

A radiation detector package includes a support apparatus at least part of which is constructed from a naturally occurring radioactive material. A scintillator is associated with the support apparatus. The support may include a detector housing carrying a photodetector and the scintillator, and the detector housing may be constructed from the naturally occurring radioactive material.

Scintillation detector package having radioactive support apparatus

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 radiation generator is provided that includes a target, a cathode to emit electrons in a downstream direction toward the target, a first conductive member downstream of the cathode, and a second conductive member downstream of the cathode. The first and second conductive members have a potential difference with the cathode such that a resultant electric field accelerates the electrons toward the target. A diagnostic current in the second conductive member and a target current in the target may be measured, and an electrical property of the first conductive member may be adjusted based upon the diagnostic current and the target current.

Radiation generator adjusting beam focusing based upon a diagnostic electrode

The present disclosure is intended to overcome the problem of hydrogen contamination of the density signal. The approach is to compute the neutron capture portion of the total gamma ray counts and subtract it from the total counts resulting in a pure inelastic gamma ray measurement.

Identification of neutron capture from a pulsed neutron logging tool

Logging-while-drilling tools incorporating an electronic radiation generator, such as an electronic X-ray generator, and a method for using the same are provided. One example of such a logging-while-drilling tool may include a circumferential drill collar, a chassis disposed radially interior to the drill collar, and an electronic X-ray generator and an X-ray detector disposed within the chassis. The electronic X-ray generator may emit X-rays out of the logging-while-drilling tool into a subterranean formation. The X-ray detector may detect X-rays that return to the logging-while-drilling tool after scattering in the subterranean formation, which may be used to determine a density and/or a lithology of the subterranean formation.

Logging-while-drilling tool incorporating electronic radiation generator and method for using same

A scintillator detector package includes a housing, with a scintillator in the housing. There is a radioactive reflective material between at least a portion of the scintillator and the housing. The radioactive reflective material may be a naturally occurring material, such as LuO, and may be in powdered form. A photodetector may be optically coupled to the scintillator package, and gain stabilization circuitry may perform gain stabilization based upon detecting scintillations of the scintillator caused by radiation emitted by the radioactive reflective material striking the scintillator.

Scintillation detector package having radioactive reflective material therein

A neutron generator includes a sealed envelope providing a low pressure environment for a gas. One end of the envelope defines an ion source chamber. A target electrode is disposed at the other end of the envelope. An extracting electrode is spaced apart from the target electrode by an accelerating gap. The extracting electrode bounds the ion source chamber. A dispenser cathode electrode and grid electrode are disposed in the ion source chamber for inducing ionization in the ion source chamber. The dispenser cathode electrode, the grid electrode and the extracting electrode operate at a positive high voltage potential and the target electrode operates at or near ground potential. This configuration provides an electric field gradient that accelerates ions towards the target electrode to induce collisions of ions with target material, thereby causing fusion reactions that generate neutrons. High voltage power supply circuit means supplies a positive high voltage signal to the electrodes of the ion source. The positive high voltage signal has a low voltage signal component floating on a positive high voltage signal component. For the dispensing cathode electrode, the low voltage signal component can be a DC or AC signal suitable for emitting electrons from the dispensing cathode electrode. For the grid electrode, the low voltage signal component can be a positive pulsed-mode signal (preferably with magnitude in the range between 100 to 300 volts). High voltage insulation surrounds and electrically insulates the high voltage power supply circuit means. Other ion source electrode configurations, such as cold cathode (Penning) ion source and RF-driven ion source, can also be used.

Neutron generator

A radiation detector may include a housing, and a scintillator body carried within the housing and including a proximal portion defining a proximal end, a distal portion defining a distal end, and a medial portion between the proximal portion and the distal portion. The scintillator body may have a constant diameter along the proximal portion, and a decreasing diameter along the distal portion from the medial portion to the distal end. The radiation detector may further include a photodetector coupled to the distal end of the scintillator body.

Scintillator with tapered geometry for radiation detectors

A radiation generator may include a generator housing, a target electrode carried by the generator housing, a charged particle source carried by the generator housing to direct charged particles at the target electrode based upon an accelerating potential, and a suppressor electrode carried by the generator housing having an opening therein to permit passage of charged particles to the target electrode. A target extender electrode may be between the suppressor electrode and the target electrode and have an opening therein to permit passage of charged particles to the target. At least one voltage source may be coupled to the target electrode, the suppressor electrode, and the target extender electrode to cause the target electrode to have a voltage greater than a voltage of the suppressor electrode and to cause the target extender electrode to have a voltage greater than the voltage of the suppressor electrode.

Target extender in radiation generator

A radiation generator includes an insulator, with an ion source carried within the insulator and configured to generate ions and indirectly generate undesirable particles. An extractor electrode is carried within the insulator downstream of the ion source and has a first potential. An intermediate electrode is carried within the insulator downstream of the extractor electrode at a ground potential and is shaped to capture the undesirable conductive particles. In addition, a suppressor electrode is carried within the insulator downstream of the intermediate electrode and has a second potential opposite in sign to the first potential. A target is carried within the insulator downstream of the suppressor electrode. The extractor electrode and the suppressor electrode have a voltage therebetween such that an electric field generated in the insulator accelerates the ions generated by the ion source toward the target.

Radiation generator having bi-polar electrodes

Growing community of inventors

Plainsboro, NJ, United States of America

Kenneth Edward Stephenson