Abstract
This article examines problems associated with the quality of cementing and casing integrity in oil and gas wells under conditions of increasing drilling activity in Kazakhstan. It is shown that complications such as behind-casing hydrocarbon migration, sustained casing pressure, and water coning are largely caused by poor cementing quality and the loss of wellbore integrity. It is noted that more than 30% of wells worldwide exhibit inter-casing pressures of varying intensity, which highlights the relevance and significance of this issue. The main causes of cement sheath degradation under the influence of mechanical, hydraulic, and thermal loads during well operation are analyzed. Particular attention is given to the problem of incomplete displacement of drilling fluids in the annular space, which leads to channel formation and a reduction in the isolation properties of the cement sheath. The role of buffer fluids in the cementing of wells drilled with hydrocarbon-based drilling fluids is also considered. The study emphasizes the need to develop effective buffer systems that ensure compatibility between drilling fluids and cement slurries, thereby improving displacement efficiency and enhancing the overall quality of well cementing and zonal isolation.