Comparative Study On The Application Of MCNP And Geant4 In Well Logging

With the development of society and science technology,the scale of exploration and exploitation of petroleum has been increasing,and the exploitation of petroleum and gas has become more and more difficult,the development of azimuth-while-drilling gamma logging technology is very important.Monte Carlo simulation is one of the important application methods for the study of gamma logging.As a general particle transport software,MCNP is difficult to use in some cases,another Monte Carlo.simulation software should be found as a supplement.To this end,this paper will use Geant4 and MCNP to model a certain type of azimuthal gamma instrument.Through a series of simulation measurements and data calculation,compare the different of the both Monte-Carlo simulation software in application and the applicability in the field of gamma logging.Firstly,a geometric model and a formation sampling scheme were established to compare the modeling efficiency of the both software.After verifying the built model with experimental results,various performance response characteristics of the instrument,such as radial detection depth,longitudinal resolution and azimuth resolution,could be measured.In this process,we can not only compare their simulation accuracy and computational efficiency,but also compare their means of data processing and model modification.The significant difference between azimuthal gamma logging while drilling and natural gamma logging is that the measured data include azimuthal information,which can be used for geosteering to improve logging efficiency.Therefore,a set of algorithm for azimuthal gamma imaging is proposed based on the investigation of the process of azimuthal gamma measurement in the formation radioactive environment,and using MCNP and Geant4 to simulate the detection process of the azimuth gamma instrument in the formation of different dip angles to evaluate the algorithm,which shows the effectiveness of the imaging algorithm.The algorithm proposed in this paper interpolates the four-sector data integrated by the simulation data to obtain the azimuth gamma image of the corresponding formation,and the formation dip angles will be calculated by using the sinusoidal curve amplitude in the image.According to the error of the dip angle,the application of the both in azimuthal gamma imaging is compared.In this paper,the Monte Carlo simulation model of a certain type of azimuthal y instrument is established and verified by comparing GEANT4 and MCNP,then analyzed the performance of the instrument,and proposed and realized the algorithm of using the azimuth gamma measurement data for formation imaging.After a series of simulation works,it is concluded that the modeling methods of the both have their own advantages and disadvantages,the simulation accuracy can meet the logging practice application.In contrast,MCNP is more concise and general,while Geant4 is more convenient in the aspects of simulation program function customization and data processing.In general,the application of Geant4 in the field of gamma logging is feasible and has practical significance.It provides a new modeling method and application scenario for simulators,and has a good engineering and practical prospect.