A B S T R A C TDuring surveys, water layers may interfere with the detection of oil layers. In order to distinguish between oil and water layers, research on the properties of well diameters and oil and water layers and their relation to acoustic logging rules is essential. Using Hudson's crack theory, we simulated oil and water layers with different well diameters or crack parameters (angle and number density). We found that when the well radius increases from 0.03 m to 0.05 m, the variation ratio of compressional wave amplitude for the oil layer is less than that for the water layer. The difference of Stoneley wave amplitude between the crack parameters (angle and number density) is greater in the case of the water layer than in the case of the oil layer. The response sensitivity of wave energy is greater for the water layer than that for the oil layer. When the well radius increases from 0.05 m to 0.14 m, the maximum excitation intensity for oil layer is greater than that for the water layer. We conclude that the propagation of an elastic wave is affected by medium composition and well diameter, and the influence has certain regularity. These results can guide further reservoir logging field exploration work.

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Summary Uranium is an important energy material and a key exploration object in the field of radioactive geophysical exploration. Through field study, it was found that fractured uranium is one of the most abundant sources of uranium, therefore it is an important target of energy geophysical exploration. However, the fractured structure increases the difficulty of uranium exploration and analysis. Therefore, in order to identify the distribution and analyse the content of fractured uranium deposits, it is necessary to study the influence of fracture parameters on the occurrence state of uranium ore and its manifestation status in neutron logging response. Considering the fracture structure from different aspects, this study simulated the uranium ore occurrence state in the pore-fracture medium environment and obtained corresponding logging response results by setting two fracture parameters (number density and angle). The study generated several findings, namely: 1. high angle and high porosity fracture type uranium strata have the greatest influence on thermal neutrons; 2. under the condition of high porosity, the neutron energy spectrum displays a dispersion peak and moves towards the high energy region. It is noteworthy that in a high number density environment, medium-low angle uranium ore has the strongest thermal neutron absorption in a low energy range. 3. energy decay rate is the highest in the high angle fracture environment; and 4. the higher the density of the fracture number, the more susceptible the counting is to the influence of the angle factor. These findings can be used to quantitatively analyse the effects of fracture parameters on uranium deposits. These results have important guiding significance to the evaluation of a fractured uranium reservoir.