Determination Method of Variable T2 Cutoff Value in NMR Logging of Low Permeability Reservoir in Daqing Oilfield X7 Area
T2 cutoff value is a key parameter for calculating bound fluid porosity, mobile fluid porosity and permeability in NMR logging. On the basis of existing core mercury injection data and NMR logging data, a method for continuously calculating T2 cutoff value of NMR logging in low porosity and permeability reservoir is proposed. Firstly, T2 spectrum of nuclear magnetic logging at the corresponding depth of the core is replaced by T2 spectrum of the nuclear magnetic experiment. The permeability contribution in the mercury injection data of the core is used to determine the mercury input saturation corresponding to the bound water, and the remaining mercury saturation at this time is the bound water saturation. The combined with T2 spectrum, the T2 cutoff value of the core is obtained by interpolation algorithm. Finally the distribution of T2 cutoff values in the T2 spectrum of multiple cores is analyzed, and a method for continuously calculating the variable T2 cutoff values is established according to the T2 spectrum morphology. This method is applied to the continuous T2 cutoff value calculation of NMR logging in X7 area, and the calculated T2 cutoff value is used to calculate reservoir parameters such as porosity and permeability, which significantly improves the calculation accuracy of reservoir parameters.
nuclear magnetic resonance loggingvariable T2 cutoff valuelow porosity and permeability reservoirbound water porosityDaqing oilfield
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