Detecting contaminants in aquifers through modeling of surface-downhole geoelectrical data

VICTORIA BONGIOVANNI; VIVIAN GRÜNHUT; ANA OSELLA

Turin

Congreso; Near Surface Geoscience - 21th European Meeting of Environmental and Engineering Geophysics.; 2015

EAGE

The exploitation of a hydrocarbon reservoir typically consists of three successive steps. The second step consists of injecting brine in some of the wells in order to maintain reservoir pressure. Even though sinks wells used by oil companies are located much deeper than aquifers, they may eventually cause environmental damages contaminating the water with brine leakage, oil spill or other polluting agent. This is why it is extremely important to do vulnerability studies. It is very difficult to detect an anomaly located in a sheet that is thin in relation to its depth with a narrow lateral extension (no more than a hundreds of meters) using only surface electrodes. That is why in this work we want to see if it is possible to identify the contamination of a great part an aquifer that lies above an oil reservoir, approximately at 300 m depth, with current injections on surface and voltages sensors in only one well. In order to achieve this we have designed an electrical model of the reservoir using log data and geological information from wells, including the contaminated aquifer with either a conductive contamination such as saline brine or a resistive contamination such as oil spill, and numerically simulated the forward and inverse geoelectrical responses.