脉冲中子孔隙度测井密度校正研究

Study on Density Correction of Pulsed Neutron Porosity Logging

在井下地层中子孔隙度测井中,不同中子源测量得到的孔隙度存在显著差异,这已成为脉冲中子源取代同位素中子源进行中子孔隙度测量面临的重大挑战。基于中子孔隙度测量原理,分析了不同中子源对孔隙度测量的差异,给出脉冲中子孔隙度测量的密度校正方法。在石油工业计量站的标准刻度井群中对2种中子源仪器进行刻度,分析地层孔隙度与仪器的响应关系。将2种仪器测量得到的现场井试验数据进行对比,对校正方法的适用性进行验证。结果表明:脉冲中子源孔隙度对地层孔隙度灵敏度要低于同位素中子源孔隙度;脉冲中子孔隙度经过密度校正后,泥岩效应的影响显著降低,与同位素中子源孔隙度有较好的一致性。

There is a significant difference between the porosity of pulsed neutron and that of isotopic neutron sources in downhole porosity logging,which has become one of the challenges faced by pulsed neutron source to replace traditional isotopic neutron source.This paper analyzes the difference of porosity measurement by different neutron sources based on the principle of neutron porosity measurement,and proposes the corresponding density correction method.The calibration of the two neutron source tools in the calibration well group in the petroleum industry measuring station is carried out to obtain the relationship between the instrument response and the formation porosity.The field test data measured by the two tools are compared to verify the applicability of the calibration method.The experimental results show that the porosity sensitivity of pulsed neutron source porosity tool is lower than that of isotopic neutron source tool.The shale effect of pulsed neutron porosity is obvious,and the effect of shale effect is significantly reduced after density correction,which is in good agreement with the isotope neutron source porosity.