SIMULAÇÃO NUMÉRICA MULTIFÁSICA DE FLUIDO DE PERFURAÇÃO E DE TRANSPORTE BENZENO EM POÇO DE PETRÓLEO NA BAHIA, BRASIL NUMERICAL SIMULATION OF MULTIPHASE FLUID DRILLING AND TRANSPORT OF BENZENE IN AN OIL WELL IN BAHIA, BRAZIL

Drilling fluids with varied chemical composition are used in oil well industry due to their specific prop- erties with respect to the well particular characteristics. Environmental concern led the oil industry to research and produce fluid compositions that are potentially harmless to the environment and at the same time, offer similar per- formance to the former fluids based on diesel oil. This document shows simulations of the fluid emulsion based on hydrogenated n-paraffin with water, based on a case study at the Sao Sebastiao Aquifer, in the Bacia do Reconcavo, Bahia. Among the compounds that form the n-paraffin fluid there are trace concentrations aromatic group BTEX (benzene, toluene, ethylbenzene and xylenes) of environmental concern. Numerical simulation was divided in two phases: a) multiphase: where the n-paraffin fluid invasion of the geological formation immediately adjacent to the drilling wall indicated that the fluid would reach a distance of 15cm from the wall with maximum saturation of 60% of the porous medium; b) transport: from the previous results, it was simulated the fate of dissolved benzene, which indicated that it could reach a distance of 3,0m from the well wall where concentrations were under CETESBs intervention values (CETESB, 2005).