Application of gamma rays to determine the optimal location of wells excavated for petroleum exploration using Monte Carlo method

Gamma ray interactions with materials is a non-destructive method, which can be used for obtaining useful information such as the densities of the materials. In this work, the Monte Carlo Neutron – Photon (MCNP) code was used to simulate a block composed of sedimentary rocks with four holes (wells) so that each hole contained a detector. Then, by placing a Cs137 source in one of the holes and adding various percentages of water and oil to the sedimentary constituents of the block, the contrast value for the output and scattered gamma rays was obtained by the response function of the detector inside each of the wells. The response function of the detector in front of the source is greater than that of the other detectors. The obtained contrast in the block containing sedimentary rocks with forty percent of oil in the first to fourth holes is -219.10, -354.85, -174.75 and -197.30, respectively, and the contrast for the case of water in the first to fourth holes is -198.31, -330.87, -167.73 and -185026, respectively. Given the fact that by digging several holes either for the scattered or crossed gamma, one can obtain a better location for the detector position. It is also clear from the calculated valuesthat the contrast obtained from the second hole (that is in front of the source) is greater than the rest of the contrasts. However, due to the quantity D, the first hole is superior to the rest, because it can be distinguished from minerals by the percentage of materialsin the soil.