The Research Of High Resolution Neutron Logging Based On Monte Carlo Method

This paper is based on Monte Carlo method that often be used in nuclear logging. MCNP is a software for Monte Carlo simulation. Formation models can be built with MCNP special code. From a large number of particles simulation for different situations and logging response, it is found out the response relationship between vertical resolution and spacing; different short and long spacing how influence detector counting rate/ratio and porosity sensitivity; and different results from different shielding material. It is confirmed that linear relation is existed between spacing and vertical resolution in neutron logging. Compensated neutron logging tool(CNL) has two detectors and porosity is computed by counting ratio. Its vertical resolution mainly decided by long spacing and is almost equal to long spacing.Optimally designing of high resolution CNL detector structure was mainly considered rates, resolution, and porosity sensitivity. It’s sure that the long spacing is should as small as possible, and short spacing should away from the long. The type and size of detectors and spacing should be designed with engineering practice.Meantime correction algorithm also be considered contained influence as caliper, mud cake, hole clearance, mining effect, lithology correction and mud salinity correction. Resolution matching technique is attempted in data processing. Through field experimentation verification, the tool’s repeatability and consistency is well, compared with traditional CNL which resolution is only 0.6m, vertical resolution get great improvement.