Schlumberger Technology Corporation

David L Best

Michael Lynn Evans

Philip Lawrence Kurkoski

Jacques M Holenka

William R Sloan

Brian Oliver Clark

A system for measuring the size of a borehole penetrating an earth formation is disclosed. The system uses a neutron source and a least one neutron detector. The neutron detector responds primarily to the composite hydrogen content of material within the borehole and formation upon irradiation by the neutron source. A partition response function is used to delineate the portion of the detector response resulting from borehole and from the formation. Since the detector response from the borehole can be isolated using the partition function and the hydrogen content of the borehole fluid is generally known, the size of the borehole can be determined from borehole response portion of the composite detector response if combined with a neutron porosity measurement of the formation. The neutron porosity measurement can be obtained independently, or by combining the neutron detector response with the response of a second neutron detector at a different axial spacing from the neutron source. The system is applicable in both logging-while-drilling and wireline logging operations.

Borehole caliper derived from neutron porosity measurements

A method and apparatus for measuring formation characteristics as a function of angular distance segments about the borehole is disclosed. The measurement apparatus includes a logging while drilling tool which turns in the borehole while drilling. Such characteristics as bulk density, photoelectric effect (PEF), neutron porosity and ultrasonic standoff are all measured as a function of such angular distance segments where one of such segments is defined to include that portion of a 'down' or earth's gravity vector which is in a radial cross sectional plane of the tool. The measurement is accomplished with either a generally cylindrical tool which generally touches a down or bottom portion of the borehole while the tool rotates in an inclined borehole or with a tool centered by stabilizer blades in the borehole.

Logging while drilling method and apparatus for measuring standoff as a

Logging while drilling method and apparatus for measuring formation

A method is proposed for determining the distance from an investigating device to the surface of a medium capable of supporting wave propagation. According to the method, a propagatory wave is generated at a given location along the surface of said medium and spaced laterally therefrom. The propagatory wave is caused to enter the medium and to propagate in the medium. The phase of the propagating signal is detected at a pair of locations respectively spaced longitudinally along the surface of the medium by different distances from the transmitting location. An indication of the lateral spacing between the detecting means and the medium is determined in response to the phase information detected at the pair of locations.

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Houston, TX, United States of America

David L Best