The thermal steam effect (TSE) on oil-saturated carbonate rock with residual water saturation (case study of core material taken from Chernoozerskoe and Pionerskoe oil fields of the Republic of Tatarstan) was simulated using a specially designed laboratory test bench. In advance, in order to study the effect of the mineral composition of the rock on the results of thermal stimulation, thermal oxidation of the Chernoozerskoye and Pionerskoye oils in carbonate rock and quartz sandstone was investigated, and it was shown that the carbonate rock shifted the low-temperature oxidation onset temperature towards higher temperatures, and the process of low-temperature oxidation occurred faster. It was shown that during TSE in the oil-saturated rock the low-temperature oxidation of oil occurred, and a change in the gas relative permeability of rock was detected. It was established that steam with a temperature of 150 °C did not pass through the pore space of a low-permeable carbonate core sample. In increasing steam temperature up to 200–300 °C the vapor began to pass through a core. For a highly permeable carbonate core sample it was determined that an increase of TSE temperature from 200 to 350 °C leaded to an increase in gas relative permeability by 6.8 times.
The oil-displacement efficiency by steam in our experiments performed at a temperature of 250–300 °C was less than 30 %. In light of this, the thermal steam stimulation for the development of heterogeneous carbonate oil reservoirs was not recommended. For development of carbonate reservoir the combination of the TSE method with solvent injection was recommended. It was shown that combination of the TSE with solvent injection could increase the oil-displacement efficiency up to 70 %.
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