热中子俘获饱和度测井示踪剂研究

Study on the use of tracer for thermal neutron capture saturation logging

20世纪 90年代末 ,在我国油田兴起使用高俘获截面的示踪剂进行热中子俘获饱和度测井技术 (中子寿命测井或中子伽马测井 )。最初使用示踪剂硼 (硼酸或硼砂 )进行测井—渗入—测井 ,随后又研制出钆络合物作为示踪剂。经理论研究和测井实践证明 ,在核物理性质方面 ,钆的热中子俘获截面远大于硼 ,能为示踪测井曲线提供明显的异常值 ,而在测井中所用的重量远轻于硼 ;在化学性质方面 ,钆示踪剂以络合物的形式存在 ,比硼有更强的稳定性和安全性。用钆络合物作为示踪剂 ,在大庆、中原和南阳油田进行了中子寿命、中子 伽马测井—渗入—测井工艺试验 ,其测井资料在油田开发应用中见到了明显的效果。

Thermal neutron saturation logging (neutron lifetime log or neutron-gamma log) run with high capture cross section tracter has been widely used in many oilfields in China,since the end of 1990's.Boron tracer (boric acid or sodium borate) was used at the initial stage of logging under the operation of log-permeation-log technique.Then gadolinium complex was discovered to be better than boron taken as tracer.Theoretical research and logging operation proved that the thermal neutron capture cross section of gadolinium is much bigger than that of boron.The gadolinium tracer can help to show the abnormality on logging curves more clearly.The weight of gadolinium used for logging operation is far lighter than that of boron.The chemical property of gadolinium is more stable and safer than that of boron,because gadolinium tracer stays as a complex compound.Logs run by neutron lifetime logging tool and neutron-gamma logging tool using gadolinium complex tracer under the operation of log-permeation-log technique have found better application to development of Daqing,Zhongyuan and Nanyang oilfields in China.