Estudo da aplicação da análise por ativação com nêutrons para a verificação da integridade da cimentação em poços de petróleo utilizando Simulação Monte Carlo

Abstract

The integrity of all the oil wells structures, in general, and the cementing of the wells – responsible for the fixation of the wells in the adjacent terrestrial formation –, in particular, is crucial for their safe operation and also for their safe abandonment in the post extraction stage. The verification of the integrity of the cementitious sheath of petroleum wells is mostly done with the use of ultrasonic tools. Despite providing good results, this verification method ends up being very costly in terms of time and financial variables due to the operational conditions in the petroleum wells. In the present work, we study the possibility of using neutron activation analysis for this purpose – based on the properties of the characteristic gamma rays emission by the elements with the excitation of their nucleus. The study was carried out using different configurations of Monte Carlo simulations made with the MCNP code using a 14 MeV neutron source. The results show that this method of verification of the cementitious sheath integrity in oil wells is viable and that the distinction between the involved materials, based on this technique, can be performed by the analysis of the absolute values of the energy peaks recorded experimentally, by the ranges of emission ratios between peaks of different elements and by the variation of these ratios with the materials thicknesses.