| Horizontal wells,highly deviated wells and other unconventional oil and gas wells have become the hotspot of global oil and gas resources exploration and development.It is of great significance to enhance the development and promotion efforts to ensure energy supply and optimize energy structure in China.Azimuth logging while drilling is one of the effective ways to improve reservoir recovery and realize unconventional reservoir development.Azimuth gamma logging while drilling is an effective means for evaluating reservoir interface,optimizing instrument drilling scheme and providing geological guidance.However,the application of azimuth gamma while drilling is greatly limited due to the technical problems such as instrument calibration and environmental interference.In this paper,aiming at the response and imaging law of azimuth gamma logging while drilling in different formations in practical application and the influence of borehole environment on gamma response,the forward simulation study of gamma logging while drilling is carried out,the numerical calculation model of instrument formation is established,the method of environmental correction is formed,and the azimuth gamma logging evaluation caused by borehole environmental factors is eliminated.Misjudgement.Provide technical support for oil and gas energy development in China.According to the technology of azimuth gamma logging while drilling,the gamma field distribution law of horizontal formation is analyzed from the action process of gamma ray and formation.MCNP model is established to simulate the response characteristics of azimuth gamma while drilling,and the counting rate conversion of simulation data is carried out according to API calibration method.It is concluded that the detection depth of upper and lower strata is 17 cm and 20 cm respectively,and the longitudinal resolution of detector with length of 10 cm is 20 cm,and the azimuth sensitivity is 19.24 degrees.Through the establishment of MCNP model,the gamma response law of different borehole sizes,instrument eccentricity and mud environment is simulated and studied,the gamma correction formula is formed,and the environmental correction chart is completed.Starting from the geometric relationship between the instrument and the formation structure,the forward modeling is carried out.The different formation conditions,such as the dip angle between the instrument and the formation,the thickness of the drilling target formation and the distance between the detector and the formation interface,are changed.The gamma response distribution characteristics are simulated and the calculation formulas of the basic parameters of the formation are summarized.The environmental correction and formation parameters calculation of gamma curve and imaging map are carried out by using Gamma data of drilling azimuth of field oil wells.The comparison with actual formation conditions is basically consistent,which verifies the feasibility of the method.According to the attenuation effect of gamma field in medium,the fast forward calculation of azimuth gamma while drilling is preliminarily realized,which is basically consistent with the results of MCNP and provides new technical support for the application of azimuth gamma while drilling.Monte Carlo numerical simulation of azimuth gamma logging while drilling is based on the characteristics of formation gamma.This paper studies the detection characteristics and basic formation laws of azimuth gamma while drilling,summarizes the calculation methods of formation parameters providing geological guidance,carries out the API calibration conversion of azimuth gamma while drilling,and finally establishes the environmental calibration chart of azimuth gamma while drilling to form a systematic forward measurement method of azimuth gamma while drilling.Four measured azimuth Gamma data are processed and the results are consistent with the reality.A fast forward method of azimuth gamma while drilling is preliminarily realized.Compared with MCNP,the calculation speed is several hundred times faster.However,there are still some shortcomings in counting rate conversion and volume detector integration,resulting in low accuracy.In order to complete the field application of fast forward method,further improvement should be made. |
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