PNST脉冲中子全谱测井仪在大庆油田的应用

Applications of the PNST Pulsed Neutron Spectral Tool in Daqing Oilfield

PNST脉冲中子全谱测井仪用于套后地层参数评价，一次测井就能同时完成双源距碳氧比、中子寿命、脉冲中子－中子、能谱水流等测井功能。PNST测井仪在大庆油田已应用664井次，通常以70～120m／h速度测井，比传统DDCＯ－2双源距碳氧比测井仪时效提高1倍以上，依据PNST测井资料增油降水措施有效率可达85％。PNST测井仪不仅能提供饱和度资料，而且具有套后独立评价储层的能力：通过叠合远俘获伽马计数FTMD曲线和热中子计数TCTSP曲线直观评价地层渗透性和划分储层；以地层俘获截面SGFM曲线计算地层泥质含量，以近远俘获伽马计数比RTMD曲线计算储层孔隙度；以中子寿命测井近伽马计数、远伽马计数及SGFM曲线对气层进行识别和定量解释；远氧活化指数IHM指示出水层位。PNST测井仪已全面替代了过去规模应用的DI）C02双源距碳氧比测井仪，成为大庆油田稳产的重要支撑技术。

The PNST pulsed neutron spectral tool has the ablhty to carry out nme-snareo multitask in casedhole to evaluate formation. Its task often involves dual-spaced carbon/oxygen logging, neutron lifetime logging, pulsed neutron-neutron logging and spectral water flow logging simultaneously in one pass. The tool was utilized in 664 wells in Daqing oilfield. Suggested logging speed is 70 m/h to 120 m/h, which is twice faster than that of traditional DDCO-2 dual-detector carbon/oxygen tool. With assistance from its oil saturation interpretation, 85% workover jobs of water shut-off, re-perforation or well stimulation achieved the desired results. In addition to oil saturation data, field applications also verified its stand-alone analysis behind casing： through overlapping curves of far capture gamma-ray count FTMD and thermal neutron count TCTSP, one can directly evaluate formation permeability and divide layers; the formation capture cross-section SGFM is used to calculate shale volume, and the near/far capture gamma-ray count ratio RTMD to porosity;with neutron lifetime logs, i.e. near and far gamma- ray counts, as well as SGFM, one may recognize and quantitatively interpret gas zones; and far oxygen activation index IroA is a reliable water flow indicator for water entrances. The PNST has displaced the former DDCO-2 tool, and has become an important support for maintaining stable oil production in Daqing oilfield.