Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Patent
1998-07-21
2000-02-29
McElheny, Jr., Donald E.
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
G06F 1700
Patent
active
060321024
ABSTRACT:
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.
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Scott Hugh D.
Wijeyesekera Nihal I.
Jeffery Brigitte L.
McElheny Jr. Donald E.
Ryberg John J.
Schlumberger Technology Corporation
Segura Victor H.
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