Schlumberger Technology Corporation

Hugh D Scott

Donald C McKeon

Nihal I Wijeyesekera

Jean-Remy Olesen

James F Carroll

The present invention provides for method and an apparatus for determining the porosity of a geological formation surrounding a cased well. The method further comprises of generating neutron pulses that release neutrons into an area adjacent the well, from a neutron source. Neutrons are sensed and a plurality of neutron detector count rates is acquired using at least two neutron source to neutron detector spacings. A timing measurement is acquired at one of the spacings to measure a first depth of investigation. A ratio of the neutron detector count rates is acquired to measure a second depth of investigation. An apparent porosity is calculated using the timing measurements and the ratios of neutron count rates. The effect of a well casing on the calculated apparent porosity is determined in response to at least one of the ratio of neutron detector count rates and the timing measurement. A cement annulus is computed based on the ratios of neutron count rates and the timing measurement. A formation porosity is calculated by performing a correction to the apparent porosity for the casing and the cement annulus.

Method and apparatus for measuring well characteristics and formation

A nuclear spectroscopy method and apparatus for obtaining qualitative and quantitative information related to water flow, comprising the steps of:

Nuclear oxygen activation method and apparatus for detecting and

In order to properly treat the tubing of an oil producing borehole, and prevent hazard to personnel at the oil production site, the contamination of tubing by the formation of scale or radioactive deposits on the inner wall thereof is determined by measurement of the low-level radiation emitted by the scale and calculation of the radiation level which would be detected in the vicinity of the outer wall of the tubing in the absence of contributions by the radioactivity of surrounding earth formations. This is accomplished by a logging tool and method which includes a sonde which includes a detector and is lowered in the tubing to detect and count the gamma rays emitted by the scale or radioactive deposits at different depths in the borehole tubing. Data processing determines the radioactivity level within the tubing from the measured gamma rays, and calculates from that level the level of radioactivity which would have been detected outside and in the vicinity of the tubing by applying a first tubing thickness attenuation factor. In a preferred embodiment, data processing corrects for the natural background radioactivity level by subtracting a reference natural radio activity level, itself corrected for tubing thickness by applying a second tubing thickness attenuation factor.

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Katy, TX, United States of America

Hugh D Scott