氘-氘和氘-氚随钻中子孔隙度测井探测特性对比

为考察在随钻中子孔隙度测井中用氘-氘(D-D)脉冲源替代氘氚(D-T)源的可行性,利用蒙特卡罗模拟方法,对比分析使用两种脉冲源时测井仪器的热中子空间分布、零源距区域、地层孔隙度灵敏度以及探测深度等探测特性.研究结果表明,D-D与D-T源相比,虽然在水平或大斜度井段对地层界面的分辨能力稍低一点,但是两者的零源距区的上限值、近源距和探测深度都大致相等,且D-D源对地层孔隙度的灵敏度更高、使用时更安全,在随钻脉冲中子孔隙度测井中可以得到更好的使用.

Comparison of D-T and D-D accelerator investigation characteristics in pulsed neutron porosity logging while drilling

In order to study the feasibility of using Deuterium-Deuterium (D-D) accelerator to replace Deuterium-Tritium (D-T) accelerator in logging-while-drilling (LWD) neutron porosity logging, the investigation characteristics for D-T and D-D accelerators in LWD neutron porosity logging were compared by Monte Carlo simulation method. The thermal neutron spatial distribution, critical detector-source spaces, formation porosity sensitivity and investigation depths of two sources were obtained. The results show that D-D source has the slightly lower resolution to formation interface in horizontal or deviated well than D-T source, but the max value of critical detector-source spaces, near source space or investigation depths of two sources were approximately equal respectively. Moreover, both the formation porosity sensitivity and safety of D-D source are significantly higher. Therefore, D-D source could be better used in LWD neutron porosity logging.