Evaluation of the Effectiveness of the Acid Treatment of Low-Permeability Carbonate Reservoirs Using a Developed Foam-Acid Composition Through Physical Modeling and 3D and 4D Tomography on Core Models

Abstract

Currently, fields with carbonate reservoirs are the main objects of geological exploration, providing the bulk of the increase in oil and gas reserves. Carbonate deposits are highly productive and provide about 60% of global oil production [1]. More than 200 fields with carbonate reservoirs are exploited in Russia. In recent years, low-permeability rocks have become increasingly promising as productive reservoirs. This paper examines the deposits of the Republic of Tatarstan. This fields are characterized by an average reservoir temperature of 23-25 °C, reservoir pressures of 50-60 bar and high salinity of water in the near well-bore area. The oil in the fields is highly bituminous, and the mineralization of water is more than 20 g/L. Currently, carbonate deposits are being actively developed in this area. Contamination or clogging of the bottomhole zone of production wells is one of the main problems that complicates oil production from carbonate reservoirs [2]. In the process of field development, the effectiveness of geological and technical actions to bottomhole treatment of wells decreases due to changes in the structure of reserves, well stock, deterioration of reservoir properties of the near well-bore area, increase in water cut, changes in the component and salt composition of the produced fluid. The most common method of cleaning the near well-bore area for carbonate reservoirs is the use of various types of hydrochloric treatment. The experience of using hydrochloric treatment technology in the fields of Tatarstan [3–6] has shown that this technology in its traditional design has less efficiency every year. The high rate of reaction with the rock does not allow the acid to penetrate deep into the formation, the low viscosity of the agent leads to the formation of large channels in highly permeable zones. As a result, low efficiency of repeated treatments is observed due to the expansion of existing channels and less radial distance from hole axis.