Method and apparatus for gamma ray well logging

Patent · Tue Dec 09 04:00:00 EST 1986

OSTI ID:6988079

Minette, D C

A method is described of investigating a subsurface earth formation traversed by a borehole comprising: introducing first photons into the formation; detecting second photons emanating from the formation; generating electrical signals in the borehole for all the detected photons, each electrical signal representing the energy of a respective different photon in the second plurality of photons. The energy is substantially within the range of 60 to 660 KeV comprising the second photons emanating from the formation into the borehole; delivering all of the electrical signals to the surface; establishing preselected energy ranges, each range corresponding to a different amplitude range of the electrical signals; deriving count rates. Each count rate is for a different one of the energy ranges and each count rate corresponding to the number of the electrical signal occurring per unit of time within the corresponding amplitude range; deriving a first function f(SH,rho) of SH and rho from a model of subsurface formations; deriving a first soft-to-hard ratio from the count rates; and determining a first photoelectric cross-section from the soft-to-hard ratio and the first function, where f is the function; where S and H are count rates of low and high energy gamma rays in the formation, respectively; and rho is the density of the formation.

• Assignee: Dresser Industries, Inc., Dallas, TX
• Patent Number(s): US 4628202
• OSTI ID: 6988079
• 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
440400 -- Well Logging Instrumentation
47 OTHER INSTRUMENTATION
AMPLITUDES
BOREHOLES
CAVITIES
COUNTING RATES
ELECTRON EMISSION
ELEMENTARY PARTICLES
EMISSION
ENERGY RANGE
EQUIPMENT
GAMMA LOGGING
GEOLOGIC DEPOSITS
KEV RANGE
KEV RANGE 10-100
KEV RANGE 100-1000
MASSLESS PARTICLES
MINERAL RESOURCES
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
PHOTOELECTRIC EMISSION
PHOTONS
RADIOACTIVITY LOGGING
RESOURCES
SIGNALS
TIME DEPENDENCE
WELL LOGGING
WELL LOGGING EQUIPMENT