Schlumberger Technology Corporation

Libai Xu

Cornelis Huiszoon

Christian Stoller

Jiaxin Wang

Kevin Scott McKinny

Peter D Wraight

Robert Little

Wei Yang

Methods of elemental imaging of a formation include acquiring spectral gamma ray measurement, acquiring a total gamma ray image, deriving structure information of the formation from the total gamma ray image, and applying the structure information to the spectral gamma ray measurement to form an elemental image. In the present methods, the structure information of the formation is derived from comparing the total gamma ray logs for each azimuthal sector to a derived total gamma ray log. The derived total gamma ray log is acquired from the total gamma ray image by summing over all azimuth bins or the spectral gamma ray measurement by summing over all energy bins.

Methods of elemental imaging of formations and systems for producing the same

A method for correcting natural gamma ray measurements includes processing an acquired gamma ray spectrum in combination with elemental standard spectra and at least one standard mud activation spectrum to compute corrected natural gamma ray measurements. The gamma ray spectrum is acquired using a logging string employing a neutron source and a natural gamma ray sensor.

Method for correcting natural gamma ray logging measurements

A method for estimating a drilling fluid flow rate in a subterranean wellbore includes processing an acquired gamma ray spectrum in combination with standard elemental spectra and at least one standard oxygen activation spectrum to compute an oxygen activation yield. The oxygen activation yield is further processed to estimate a drilling fluid flow rate and or to infer a borehole diameter change or a lost circulation event. The gamma ray spectrum is acquired using a logging string employing a neutron source and a natural gamma ray sensor.

Mud activation measurement while drilling

A method for estimating a borehole independent porosity of a subterranean formation includes processing a neutron logging data point, preferably including average near and far detector neutron count rates with suitable input data to obtain the porosity estimate. The borehole independent formation porosity may be obtained without any compensation and without any reliance on the measurement or estimation of sensor standoff and/or borehole caliper.

Borehole independent neutron porosity measurement

A method for determining a bulk formation density using a neutron generator includes detected secondary gamma rays and evaluating the detected gamma rays according to pre-determined selection criteria. Selected gamma rays are then used to compute the formation density. The selection criteria may include, for example, a time delay between the detection of a neutron and an associated particle and/or a direction of propagation of the neutron.

Method for measuring subterranean formation density using a neutron generator

A well-logging tool may be positioned within a borehole of a subterranean formation. The well-logging tool may include a housing having an interior defining a dual-detector receiving chamber extending longitudinally, and having first and second portions, and a first azimuthal radiation detector carried by the first portion of the dual-detector receiving chamber. The first azimuthal radiation detector may include a first gamma-ray detector and a first photodetector associated with the first gamma-ray detector. The well-logging tool may include a second spectral radiation detector carried by the second portion of the dual-detector receiving chamber. The second spectral radiation detector may include a second gamma-ray detector and a second photodetector associated with the second gamma-ray detector.

Well-logging tool with azimuthal and spectral radiation detectors and related methods

A neutron logging tool includes a neutron source and at least one position sensitive thermal or epithermal neutron detector. The logging tool further includes an electronic controller configured to estimate the axial location of detected neutrons. Measurement of the axial neutron flux distribution enables other formation and borehole parameters such as formation porosity and sensor standoff to be computed. In logging while drilling embodiments, a borehole caliper may also be computed form the axial neutron flux distribution.

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Katy, TX, United States of America

Libai Xu