Features of acid treatment in conditions of high temperature collectors
During of developing oil fields, the permeability of the bottomhole formation zone (BHZ) decreases over time for various reasons. For example, the BHZ permeability may deteriorate as a result of: swelling of the clay cement of the reservoir rock, especially in the case of the prevalence of montmorillonite in its composition; the deposition of salts or asphaltene-resin-paraffin substances at the boundaries of the phases; penetration of drilling fluids and killing fluids, etc. Reduced permeability, in turn, adversely affects the production rate of wells, and sometimes even leads to its absence. At the same time, modern, constantly evolving, drilling technologies allow revealing deeper layers, which are characterized by high temperatures. Therefore, there is an increasing need for the development and improvement of acid treatment methods in such conditions. To reduce the risks of acid treatments of such wells, it is advisable to study the possible complications that are promoted by the increase in temperature. The authors of the article analyzed the profile literature, on the basis of which the main problems arising during the acid treatments of high-temperature reservoir layers were identified and considered. Among the problems addressed are: rapid acid neutralization, intensive precipitation processes, acceleration of the metal corrosion process, as well as limitations on the thermal stability of solutions. Existing methods of solving the above problems, which have already found their application in the oil and gas industry, are also considered. The materials presented in the article allow us to conclude that for a successful acid treatment of a high-temperature collector, a number of factors should be taken into account at the technology selection stage. Particular attention should be paid to the penetrating ability of the acid composition, its corrosiveness and compatibility with reservoir fluids, thermal stability.