Patent ID: 11940590
Assignee: CHINA UNIVERSITY OF PETROLEUM (EAST CHINA)
Field: Measurement (Instruments)
Classification: CPC G  E  Y | IPC E  G

Claim 2:
3. The fast forward method for gamma-ray logging of highly-deviated and horizontal wells according to claim 2, wherein step S11 comprises the following processes:
for an infinitely large uniform formation, assuming that a gamma source intensity density of the formation is I0 and an average linear attenuation coefficient of gamma-rays passing through the formation is μ;
by considering the gamma detector as a point crystal, establishing a spherical coordinate system with the center of the detector as the origin, where a distance between the formation and the origin is R; and
according to the following formula of a natural gamma-ray flux of a certain point in the infinitely large uniform formation in the spherical coordinate system, obtaining the gamma-ray flux of the formation received by the gamma detector:, J
   R
  
  =
  
   
    
     I
     0
    
    μ
   
   ⁢
   
    (
    
     1
     -
     
      e
      
       
        -
        μ
       
       ⁢
       R
      
     
    
    )
   
  
 

according to the average linear attenuation coefficient μ of gamma-rays passing through the formation, obtaining a radius r0 when the gamma-ray flux reaches 99% of a gamma-ray flux corresponding to the infinitely large formation, and taking r0 as the effective detection radius of the gamma detector; and allowing the distance between the infinitely large formation and the origin to tend to infinity, at this time, a limit value of the gamma-ray flux is I0/μ;
where,
I0 refers to the gamma source intensity density of the formation, unit: number of photons cm−3;
μ refers to the average linear attenuation coefficient of gamma-rays passing through the formation, unit: cm−1;
R is the distance between the formation and the origin, unit: cm; and
JR refers to the gamma-ray flux of the formation received by the detector, unit: number of photons cm−2.