Interpretation Method And Software Design Of Pulsed Neutron Oxygen Activation Injection Profile Logging

Pulsed neutron oxygen activation logging is a nuclear logging technique that allows non-contact measurement of fluids,determination of flow velocity in tubing,tubing annulus,and jacket annulus,and determination of fluid flow status up and down simultaneously.Pulsed neutron oxygen activation logging is widely used to monitor injection profiles in oilfields.It is capable of monitoring water flow in tubes and determining water velocity at different depth points through a series of fixed point measurements made by logging instruments.Based on the research of oxygen activation injection profile logging interpretation method,and the analysis of measured well data in oil field,combined with the designed flow interpretation software,an optimized logging interpretation method is proposed.Firstly,the principle,measurement model and response factors of pulsed neutron oxygen activation logging are systematically analyzed.Then the characteristics of single flow peak and double flow peak are summarized by collecting oxygen activation logging data,and the current logging interpretation methods are analyzed.All kinds of complex peak shapes in oxygen activation logging are reduced and the flow rates under various spectral peaks are calculated.The current logging interpretation methods are to calculate the flow velocity by calculating the transit time and the source distance.Such methods need to filter the original measured data first,and then calculate the transit time according to the filtered time spectrum,which will lead to the loss of some useful signals,and then bring errors to the calculation of the transit time,and ultimately affect the accuracy of flow calculation.Therefore,based on the physical measurement principle of pulsed neutron oxygen activation logging,an optimal interpretation method of injection profile logging is proposed.This interpretation method describes the response of the detector to the activated water flow by establishing a theoretical model of the count rate changing with time.On this basis,the objective function is constructed.At the same time,a joint algorithm based on differential evolution and artificial bee colony is adopted to solve the water flow velocity in the objective function.The optimal interpretation method can directly extract the water velocity and calculate the water flow at the measuring point according to the cross-sectional area of the pipe string.In the part of case analysis,the optimal interpretation method is used to explain the injection well under different injection methods.The results show that the optimal interpretation method can directly measure the water velocity at the measuring point,and the calculated horizontal flow value has a high accuracy,which improves the injection profile interpretation accuracy.Finally,the oxygen activation flow calculation and interpretation software is developed based on the C# development environment of Visual Studio 2019 platform,and the application of the software to measured well data is verified.