Complex geology, post-depositional alteration, and physicochemical features of sediments and pore fluids often pose problems to oil carbonate reservoir development planning. Meanwhile, lapse-time (4D) shallow electromagnetic (TEM) surveys may be a good tool to monitor waterflooding used for formation pressure maintaining and oil recovery enhancement in highly resistive carbonate reservoirs. Testing at an area developed by the Irkutsk Oil Company, with regard to key sweep efficiency criteria, has demonstrated good fit of injection volumes inferred from TEM data to real values, based on contrast of resistivity. The forecast of the displacement of the waterflooding front was made for five injection wells. These results have been obtained for the first time for a carbonate reservoir in East Siberia and are useful to enhance petroleum production in the region.
The parameters of the observation network and the intervals of the soundings were determined on the basis of hydrodynamic modeling of the reservoir and synthetic modeling of TEM signals. Three stages of full-scale electrical exploration were carried out. The use of TEM technology made it possible to verify the geological model of the oil reservoir structure and assess the type of prevailing pore space near the injection wells. The results of electrical exploration for predicting the displacement of the waterflooding front were confirmed by water breakthroughs in three production wells.
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