In the field of oil and gas field exploration and development, the Compensated Neutron Logging Tool (CNLT) is an important logging device used to obtain formation porosity information. Based on specific nuclear physics principles, it can effectively overcome interference from factors such as borehole conditions, providing key data support for geological analysis and reservoir evaluation.
The working principle of the Compensated Neutron Logging Tool is based on the interaction between neutrons and formation materials. The neutron source equipped in the tool emits high-energy fast neutrons. After these fast neutrons enter the formation, they undergo frequent elastic collisions with atomic nuclei in the formation medium. Since the mass of hydrogen nuclei is close to that of neutrons, fast neutrons lose the most energy when colliding with hydrogen nuclei. Therefore, the hydrogen content in the formation has a significant impact on the moderation process of fast neutrons. After moderation, fast neutrons become thermal neutrons. During diffusion, thermal neutrons are absorbed by formation materials, and some are captured by the tool's detectors.
The thermal neutron count rate recorded by the detector is closely related to formation porosity. Generally speaking, the higher the formation porosity, the more formation water or hydrocarbons (rich in hydrogen) it contains, the more efficient the moderation of fast neutrons into thermal neutrons, and the more thermal neutrons received by the detector. By converting the thermal neutron count rate into formation porosity, the analysis of reservoir characteristics can be realized.
In terms of structure, the Compensated Neutron Logging Tool mainly consists of a neutron source, a long-source-distance detector, a short-source-distance detector, and an electronic circuit system. The neutron source provides stable fast neutron output; the two detectors with different source distances receive thermal neutron signals from different ranges. Through ratio processing of these two signals, the influence of borehole conditions such as borehole size and mud density on measurement results can be effectively compensated-this is the origin of the term "compensated". The electronic circuit system is responsible for signal amplification, processing, and transmission, ensuring the accuracy and stability of measurement data.
The Compensated Neutron Logging Tool has many advantages. It has high sensitivity in measuring formation porosity, making it particularly suitable for evaluating low-porosity reservoirs; its compensation mechanism minimizes the impact of borehole environment on measurement results, ensuring data reliability; in addition, the tool is easy to operate and can be used in conjunction with other logging methods (such as density logging and acoustic logging). Through comprehensive analysis of multiple parameters, the accuracy of reservoir evaluation is further improved.
In practical applications, the Compensated Neutron Logging Tool plays an important role in multiple links of oil and gas exploration. It can help geologists determine the effective porosity of reservoirs, providing basic parameters for calculating oil and gas reserves; through comparative analysis with other logging curves, it can identify gas zones (gas zones usually cause abnormally low values in neutron logging porosity); meanwhile, the tool can also provide strong basis for judging formation lithology and delineating reservoir boundaries.
In conclusion, relying on its unique working principle and excellent performance, the Compensated Neutron Logging Tool has become an indispensable tool in oil and gas field exploration and development, providing solid technical support for the efficient exploration and rational development of oil and gas resources. For more details about the tool or related services, please contact sales@celestep.com.
