Thermal decay time logging method and tool

Patent · Tue Aug 07 04:00:00 EDT 1990

OSTI ID:6594392

Mahdavi, M; Sitaraman, S

This patent describes a borehole logging method for determining a characteristic representative of porosity of a formation surrounding the borehole. It comprises: irradiating the formation surrounding the borehole from a location within the borehole with a burst of neutrons, detecting at a near detector indications of the concentration of the diffused thermal neutrons following the burst of neutrons and generating near count rate signals as a function of time in response thereto, detecting at a far detector indications of the concentration of the diffused thermal neutrons following the burst of neutrons and generating far count rate signals as a function of time in response thereto, subjecting the near count rate signals to a filtering process to generate a near impulse count rate amplitude having a reduced dependency on the effects of diffusion, subjecting the far count rate signals to a filtering process to generate a far impulse count rate amplitude having a reduced dependency on the effects of diffusion; and determining the ratio of near to far count rate amplitudes as a characteristic proportional to the porosity of the formation.

• Assignee: Schlumberger Technology Corp., Houston, TX (USA)
• Patent Number(s): A; US 4947040
• Application Number: PPN: US s 7-455807
• OSTI ID: 6594392
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
COUNTING TECHNIQUES
EQUIPMENT
EXPLORATION
GEOLOGIC DEPOSITS
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NEUTRON LOGGING
NEUTRON-NEUTRON LOGGING
PETROLEUM DEPOSITS
RADIOACTIVITY LOGGING
RESOURCES
WELL LOGGING
WELL LOGGING EQUIPMENT