Monte Carlo Method In Nuclear Well Logging Applications

Nuclear logging technology has been used widely in prospecting for oil and natural gas at home and abroad. Many oil fields are on the ground of high-containing water and high-extracting, uneven stratum oil-water distributing, separated residual oil and high water saturation. Since the data curve from these logging methods is excessive, the understanding and evaluation of flooded layer has a great influence on oil field upper development, extraction efficiency and benefit.We discuss the application of PND logging in the flooded layer evaluation and analyze the relationship between water saturation and CATO which is important to evaluate the degree of water saturation. And it is found that practical data which is plentiful can't display the relationship between CATO and water saturation. So Monte Carlo numerical simulation program is used to simulate the stratum with different water saturation, and we obtain corresponding CATO and make the relationship chart which is compared with the practical logging data.We also analyze the practical PNN logging curve and find that some unfamiliar stratum can be explain through PNN logging. And MCNP program is used to simulate the thermal neutron time spectrums on the conditions of very low salinity, porosity and oil sheet. Then we obtain the corresponding formation macroscopic absorption cross section. Finally the simulation result is compared with practical logging data, and the result is good.The simulation results show that PND and PNN can reflect the situation of flooded layer in many conditions.