关键词: 脉冲中子孔隙度, 随钻测井, 电缆测井, 测井响应差异, 数值模拟

Abstract:

Because the formation model and measurement condition are different，the pulsed-neutron porosity logging responseof
logging-while-drilling（LWD）is different from that of wireline（WL），so the study on the response difference can
provide theoretical basis for the logging interpretation of pulsed-neutron porosity logging while drilling. In this paper，Monte
Carlo method is employed to build different models to study the response differences under different logging environments.
The results show that the counting ratio under LWD conditions increases in three-order polynomial form with the increase of
porosity，and the WL neutron logging response displays the same changing trend，but there is a crossing point in the LWD and
WL logging response curves. The relative sensitivity to porosity in LWD is greater than that in WL，but the drilling collar in
LWD tool can reduce the counting statistics of thermal neutron，which may influence the measurement accuracy. The effect
of different logging environments on the logging response of LWD and WL decreases with the increaseof porosity. The effect
of lithology，shale content and borehole size on the logging response difference of LWD is larger than that of WL. When the
borehole is filled with fresh water，oil and brine，the effect on logging response is slight and can be ignored. While the borehole
is full of gas，the effect on logging response of LWD is smaller than WL.

Key words: pulsed-neutron porosity logging, logging while drilling, wireline logging, logging response difference, numerical
simulation