Computing thermal neutron decay time environmental effects using Monte Carlo techniques

Journal Article · Sat Feb 01 00:00:00 EST 1986 · SPE (Society of Petroleum Engineers) Format. Eval.; (United States)

DOI:https://doi.org/10.2118/10293-PA· OSTI ID:5513712

Preeg, W E; Scott, H D

Time-dependent, three-dimensional (3D), coupled-neutron/gamma-ray Monte Carlo calculations were made for both thermal neutron decay time (TDT-K and TDT-M) logging systems. Calculations were made for different borehole sizes, casing sizes, and different formation and borehole macroscopic capture cross sections (..sigma..). Good agreement was obtained between our calculations and laboratory TDT measurements. Monte Carlo calculations were made to separate the contributions to the detector count rates resulting from gamma rays produced in various regions, such as the borehole fluid, casing, cement, and those produced in the formation. The decay rates resulting from these various components show how the measured ..sigma.. may differ from the intrinsic formation ..sigma.. and lead to a better understanding of the relationship between the near- and far-detector measurements. The calculations also provide information on the bed-thickness response of the TDT.

• Research Organization: Schlumberger Well Services
• OSTI ID: 5513712
• Journal Information: SPE (Society of Petroleum Engineers) Format. Eval.; (United States), Vol. 1:1
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
47 OTHER INSTRUMENTATION
NEUTRON-GAMMA LOGGING
COMPUTER CALCULATIONS
WELL LOGGING EQUIPMENT
PETROLEUM DEPOSITS
BOREHOLES
CAPTURE
CEMENTS
CROSS SECTIONS
DECAY
ENVIRONMENTAL EFFECTS
GAMMA DETECTION
MONTE CARLO METHOD
RADIATION DETECTORS
SIZE
THERMAL NEUTRONS
THICKNESS
TIME DEPENDENCE
WELL CASINGS
BARYONS
BUILDING MATERIALS
CAVITIES
DETECTION
DIMENSIONS
ELEMENTARY PARTICLES
EQUIPMENT
FERMIONS
GEOLOGIC DEPOSITS
HADRONS
MATERIALS
MEASURING INSTRUMENTS
MINERAL RESOURCES
NEUTRON LOGGING
NEUTRONS
NUCLEONS
RADIATION DETECTION
RADIOACTIVITY LOGGING
RESOURCES
WELL LOGGING
020200* - Petroleum- Reserves
Geology
& Exploration
440400 - Well Logging Instrumentation