Influence of Clay Content in Reservoir Rocks on Efficiency of Killing Production Wells

This paper presents the problem of workover operations in the production wells. Liquid hydrocarbons recovery involves many operations, and production wells workover and servicing are essential parts of this process. Most of the well intervention operations require preliminary well killing that includes generating a hydrostatic back pressure with a column of fluid required density to eliminate any reservoir fluid inflow and gas surges. Preliminary well killing ensures safety of both crew members and production zone. This work focuses on a specialized additive for workover fluids developed by authors aiming to create and stabilize inverse emulsions. The results of conducted research have shown that the application of special additives not only significantly reduces clay swelling (from 25% to 3.1% in the case of a 5% NaCl solution) but also prevents sudden changes in wettability. These findings lead to conclusion that the use of special formulations results in preserving reservoir permeability by maintaining the size of pores and fractures. Simultaneously, it prevents the formation from a water blockage that could impact fluid flow paths. In case of using kill fluids based on inverse emulsions the permeability decreased 1.5 times less than in case of using water-based fluids.