Monte Carlo numerical simulation of response characteristics of compensated density logging in cased hole

Key words:  density logging  casing  response characteristics  Monte Carlo method

Abstract:

To investigate the response characteristics of traditional density logging tool in cased holes, using TLD density tool of Schlumberger company by Monte Carlo method，photon flux spectrum distribution and the crossplot of long-spacing versus short-spacing count rates were gained based on the mechanism of the interaction between photon and matter. The response relationship between photon flux and spacing，and formation electron-density, the effects of the thickness of casing or cement mantle on long-spacing versus short-spacing count rates were studied. Calculated results show that the traditional TLD density tool is very sensitive to formation density change in cased hole when the thickness of casing or cement mantle is less than 4.4 cm. The traditional density tool can measure formation density in cased hole. The results show that the compensated principle of density logging used in open hole can also be used in cased hole. The formation lithology can't be correctly distinguished using density tool behind casing and cement mantle in cased hole when the casing thickness is greater than a certain value.