Investigation of increasing of the injection wells injectivity with self-diverting acid compositions in a layered heterogeneous carbonate reservoir

Abstract

Recently, a huge part of the remaining recoverable oil reserves is concen-trated in layered-heterogeneous carbonate reservoirs. For carbonate, dis-sected reservoirs, the problem of increasing the oil recovery coefficient by or-ganizing a system for maintaining reservoir pressure is still relevant. Oil fields at the last stage of operation have a number of factors that reduce the ef-fectiveness of impact on the bottom-hole zone of the productive formation. These factors include: high water content of the extracted products, low reservoir pressure, the presence of backwater flows, and the multiplicity of acid treatments. The carbonate reservoir is also complicated by multidirec-tional fracturing and a lower oil recovery coefficient compared to the terrige-nous one in addition to all these factors. The inflow in the carbonate reservoir mainly occurs through cracks, which is why there is often an advanced flood-ing both due to the advance of the water-oil contact and due to water break-outs from injection wells. In both cases, acid treatments can worsen the sit-uation, since they increase the permeability of watered channels-cracks to a greater extent due to higher filterability. Thus, as a result of repeated acid treatments of reservoirs with significant layer-by-layer heterogeneity and fracturing, the reservoir becomes even more heterogeneous in permeability. In turn, the matrix of the carbonate reservoir containing the main residual reserves under standard acid treatments is exposed to a greater extent super-ficially, in the best case, cavities are formed. Therefore, one of the important tasks of acidic action on the carbonate reservoir is the most complete involvement of its matrix in the drainage process. When treated with self-de-flecting acid, it is possible to form wormholes in the reservoir matrix not only due to inhomogeneities of the rock, but also due to redirection of the impact vector on the rock as a result of increasing the resistance of the formed gel. The article presents results of analysis of the efficiency of processing the bot-tom-hole zone of the formation to increase the intake capacity of injection wells in relation to the deposits of the Volgian stage of the Korchagin field.