Avaliação da concentração de metais pesados e hidrocarbonetos no solo do campo de petróleo Fazenda Belém nos municípios de Aracati e Icapuí no Estado do Ceará

Abstract

This work is a preliminary evaluation for determination of background or base line in heavy metals and hydro-carbons in ground of the Fazenda Belém Oil Field Belém in the city of Aracati, State of the Ceará, for comparisons with samples proceeding from areas where oil spills have occurred. The study has involved collecting of ground samples in the area, in previously selected places, taking in consideration the geology, the type of ground, oil characteristics as density, temperature, viscosity and Basic Sediment and Water (BSW). The values of concentration for some metals in the ground, the permeability, texture, density,porosity, depth of infiltration of the oil in the ground through the simulation of oil spill had been determined in lease, besides evaluating metal texts and Hidrocarbonetos Policíclicos Aromáticos (HPA) before and after the simulation of the spill. The method to simulate the spill consisted of placing, in the sampling points, a stainless steel scaffolding with dimension of 1mX1mX0,20m, leaked, after that it was spilled oil,formed emulsion of oil percentage and another one of water, removed from the closest well next to the studied place. One waited five days so that the infiltration of the oil occurred. After the determined stated period, a cut was done in the ground,inside of the area with oil with the objective of verifying the depth of infiltration and the thickness of the layer. This depth was measured with a milimetric measuring tape. After that all the oil layer was removed, the ground was perforateed with handy tract until the depth of 1 meter and samples were collected for analysis in laboratory.The research done in the field is more representative, it allows to verify in situ what can occur in the ground in case of accident with oil spill, besides making possible the determination of the permeability and the thickness of the infiltrated oil layer, without modifying the natural characteristics of the ground. The results of the analyzes of the ground samples collected before and after the simulation of the oil spill in the three selected places have not presented contamination for Hidrocarbonetos Policíclicos Aromáticos (HPA). All the concentrations of HPAs have presented values below of the limit of detection of the used method in the analysis. The concentrations of metals have not presented significant variation in the ground samples collected before and after the simulation of the spill, being inferior to the values of reference of quality for ground of national works of the Companhia de Tecnologia Sanitária e Ambiental of São Paulo State and Fadigues and International Guidelines (Canada), List Dutch and generic values of selection for ground of the Environment Protection Agency of the United States (EPA). This work will provide support in the decontamination and cleanness of the areas in case of accidents within oil spill occurrence. The previous knowledge of the possible depth of infiltration of the oil in the ground at the temperature up to 50°C, in accordance with the permeability and porosity in the place, will make it possible a better cleanness and recoverying of the area and it will facilitate the calculation of the volume of spilled oil.