Research Of Data Processing Method For Oil Saturation Using Pulsed Neutron Full Spectra Logging

The pulsed neutron full spectrum saturation logging is a well logging technology including three work model of bispectrum mode, neutron lifetime mode and oxygen activation mode that can record gamma ray energy spectrum and time spectrum by means of a special pulse and measurement timing design, then to get the information of formation C/O, neutron lifetime and water fluid which are used for formation oil saturation evaluation. According to the three word-model timing design of pulsed neutron full spectrum logging, different data processing methods of different models were studied, and the best method was chosen by the comparison of treatment effect. For C/O data, the studies of energy spectrum drift correction, calculation of clean inelastic gamma spectrum and examination of abnormal data are accomplished. The standard spectrum for correlation contrast was obtained from numerical simulation, and the best way of peak search is combination of correlation contrast and step by step contrast. The response spectrum of BGO detector under the condition of different energy were simulated by using Monte-Carlo method, the boundaries of energy windows were refreshed, and a new group of curves including new formation information was presented. The method of spectrum correlation contrast was used for examination of abnormal data. For the great background of gamma time spectrum under the neutron lifetime mode, different filtering methods were compared. The formation neutron lifetime was directly display in time chromatogram, and the cross section was calculated by the method of double exponential decay fitting. The treatment effect of different peak function on data of oxygen activation mode were compared, and a new function was chosen out for real data processing, obtained a better treatment effect. The relationships between different formation factors and the ratio of carbon/ oxygen and formation cross section and the crossplot of C/O andΣwere simulated by using Monte-Carlo method. Lithology, porosity, shale content and the condition of borehole all have influence on the calculation of C/O andΣ, among them, the influence of porosity to C/O and salinity of formation water toΣis the biggest. These influence can be reduced by the technology of using crossplot of C/O andΣto calculate formation saturation, increasing the scope of application.