Study On Response Mechanism And Data Processing Method For Density Logging With Controlled Neutron Source

In order to accurately calculate formation density using density logging with controlled neutron source,it is necessary to investigate formation density calculation methods and influence factors.The article used the numerical simulation program MCNP5 to study the vertical and horizontal detection characteristics of the instrument under different lithology and porosity conditions;The relationship between the thermal neutron count(ratio)and the formation density and hydrogen index,gave four calculation methods of formation density;the effects of different borehole and formation conditions i.e.lithology,borehole size,and formation water salinity on the four calculation methods,and the influence results on the four calculation methods are compared to analyze and their adaptability to different boreholes and formation conditions.The calculated results indicated that the tool had the highest radial resolution in sandstone;the porosity was negatively correlated with the investigation depth under the same lithological condition;the four calculation methods could accurately obtain the formation density except the compensation method of count rate ratio;for all the selected calculation methods,the deviation of the calculation results from the real values in limestone and dolomite strata were larger;The greater the formation water salinity,the greater the calculated error;when the borehole diameter was larger than the instrument one 5-6cm,the calculated formation density would have higher accuracy.;when the pore contains oil and gas,the calculated values would be lower than the real values;compared with other methods,the compensation method of the count rate ration had better adaptability to borehole and formation.