【摘要】 由于测井环境恶劣等原因，部分老井裸眼井资料缺失，套后孔隙度测井成为技术补充的重要手段。基于套管井中脉冲中子全谱测井伽马时间谱信息，建立井眼和地层近、远探测器伽马计数比组合确定孔隙度的方法。利用蒙特卡罗方法建立计算模型，模拟不同孔隙度、岩性、井眼流体和地层流体等条件下俘获伽马分布，分析近、远探测器俘获伽马计数比与地层孔隙度的响应规律，发现在高孔隙度条件下孔隙度灵敏度降低，且孔隙度灵敏度与时间分布有关。因此，基于俘获伽马时间衰减特征，组合井眼和地层俘获伽马计数比来确定孔隙度。结果表明：利用组合俘获伽马计数比确定地层孔隙度灵敏度更高，虽仍受泥质和井眼尺寸影响，但受井眼和地层水矿化度影响较小。利用该方法处理实测井资料，计算结果与补偿中子孔隙度测井值吻合较好，该方法可为在套管井中确定孔隙度提供技术支撑。更多还原

【Abstract】 Due to poor logging conditions and other factors, open-hole logging data is missing in some old wells, making cased-hole porosity logging an important technical complementary means. This paper establishes a method for determining porosity based on the gamma time spectrum information of pulsed neutron full-spectrum logging in cased wells by combining the gamma count ratios of the near and far detector gamma count ratios of the borehole zone and the formation zone. Using Monte Carlo method to establish a computational model to simulate the capture gamma distribution under different conditions of porosity, lithology, borehole fluid and formation fluid, etc., and to analyze the response characteristics of the capture gamma count ratio of the near and far detectors with respect to the porosity of the formation, and recognized that porosity sensitivity decreases under high-porosity conditions and that porosity sensitivity is time-distribution dependent, porosity is determined by combining the ratio of captured gamma counts in the borehole zone and the formation zone based on the captured gamma time decay characteristics. The results show that the determination of formation porosity using combined capture gamma count ratios is more sensitive, still influenced by mud quality and borehole size, but less so by borehole and formation water mineralization. Using this method to process the actual measured well logging data, the calculated results are in good agreement with the measured values of compensated neutron porosity, and the method provides technical support for determining porosity in cased wells.更多还原