脉冲中子孔隙度测井密度校正研究

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。

Coupled effects of stress damage and drilling fluid on strength of hard brittle shale

During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling fluid will invade into formation along the tiny cracks induced by stress damage,and then weaken the strength of hard brittle shale.Based on this problem,a theoretical model was set up to discuss damage level of shale under uniaxial compression tests using acoustic velocity data.And specifically,considering the coupled effect of stress damage and drilling fluid,the relationship between hard brittle shale strength and elapsed time was analyzed.