Epithermal neutron porosity measurement

Patent · Tue Nov 25 04:00:00 EST 1986

OSTI ID:7054507

Smith, Jr, H D

A method is described for determining the porosity of earth formations in the vicinity of a borehole passing therethrough, comprising the steps of: (a) emitting, in a portion of the borehole substantially adjacent the formations of interest, repetitive pulses of fast neutrons for moderation to epithermal energies by interaction with nuclei of materials in the borehole and surrounding earth formations, creating thereby repetitive bursts of populations of epithermal neutrons in the borehole and surrounding earth formations, the borehole constituting a first zone and the surrounding earth formations a second zone, (b) detecting epithermal neutrons at a longitudinally spaced distance in the borehole during at least four predetermined time intervals substantially spanning the time of the borehole moderation and the formation moderation of the fast neutrons. The detected epithermal neutrons thereby is representative of the epithermal neutron populations in both the zones, (c) generating at least four count rate signals representative of the epithermal neutron populations during the at least four time intervals, (d) combining the at least four count rate signals according to a predetermined relationship in which the signals are assumed to represent the sum of two substantially independent epithermal neutron populations, one in each zone. These populations decay exponentially with time at different rates, to obtain a measurement signal representative of the porosity of the surrounding earth formation, (e) recording the measurement signal as a function of borehole depth.

• Assignee: Halliburton Co., Duncan, OK
• Patent Number(s): US 4625110
• OSTI ID: 7054507
• 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
BARYONS
BOREHOLES
CAVITIES
DEPTH
DIMENSIONS
ELEMENTARY PARTICLES
EPITHERMAL NEUTRONS
FAST NEUTRONS
FERMIONS
GEOLOGIC DEPOSITS
HADRONS
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NEUTRON LOGGING
NEUTRONS
NUCLEI
NUCLEONS
PETROLEUM DEPOSITS
POROSITY
PULSED NEUTRON TECHNIQUES
RADIOACTIVITY LOGGING
RESOURCES
SIGNALS
SPACE DEPENDENCE
TIME MEASUREMENT
WELL LOGGING