Using surface downhole ERT for detecting contaminants in deep aquifers due to the exploitation of oil reservoirs

GRUNHUT, VIVIAN; BONGIOVANNI, MARÍA VICTORIA; OSELLA, A.,

NEAR SURFACE GEOPHYSICS

EUROPEAN ASSOC GEOSCIENTISTS & ENGINEERS

Lugar: Houten (Holanda); Año: 2018 vol. 16 p. 545 - 556

1569-4445

The exploitation of a hydrocarbon reservoir whether conventional or unconventional may cause environmental damages. Even though sink wells used by oil companies are located much deeper than aquifers, they may eventually contaminate the water with brine leakage, oil spill or other polluting agent, such as chemicals used in hydraulic fracturing. This is why it is extremely important to do vulnerability studies. In this case we want to see if it is possible to detect and characterize contaminations of an aquifer that lies above an oil reservoir, approximately at 250 m depth, with current injections on surface and voltages sensors in a well. It is not usual to use downhole measurements at that depth to monitor a contaminated aquifer, which is why we want to see if it is possible to identify the contamination of a part of the aquifer with surface-downhole measurements. In order to achieve this we have designed an electrical model of the reservoir including the contaminated aquifer with either a conductive or resistive contamination such as saline brine, oil spill or CO2, and numerically simulated the forward and inverse geoelectrical responses.