Many technologies for enhanced oil recovery in case of the complex carbonate reservoirs are based on acid treatment of bottomhole formation zone, and creation of new channels of filtration through rock dissolution. Disadvantages of acid solution practice are widely known. This work was aimed to test new technology for acid treatment of carbonate reservoirs and a new method of its injection into the formation. The new acid technology is based on acid composition containing complex agent AFK.
It was found that the oil produced from carbonate reservoir before application of the new technology was characterized by a practically constant density, viscosity and composition during the reservoir development. At the initial stage of new technology application (first six months) the increase in the density and viscosity and the proportion of resinous-asphaltenic components was periodically registered.
Long-time impact of new technology has led to the stabilization of the composition and properties of oil produced, as well as to the increase of the production enhancement. Earlier it was found that carbonate rocks with higher porosity and permeability contain heavier oil, and the carbonate rocks with the worst reservoir properties contain lighter oil. Taking this into account, the following assumption can be made: the new technology primarily acts to areas of a reservoir rock with high permeability and releases the heavy oil. Then the zones of reservoir rock with low permeability are involved, from which the lighter oil is displaced.
The results of the investigation can be used to develop the criteria of efficiency and duration of the application of new technologies to enhance oil recovery, as well as to define and predict the product characteristics of the produced oil.References
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