Abstract
<jats:p>The paper presents approaches to the development and optimization of drilling fluid formulations intended for the operation of wells constructed under complex geological and technical conditions characteristic of the Karachaganak oil and gas condensate field. The relevance of the study is determined by the need to apply technologically advanced and environmentally safe drilling fluids capable of effectively penetrating low-permeability terrigenous formations and minimizing damage to the reservoir properties of productive horizons. Based on an analysis of the lithological and stratigraphic features of the section, formation pressures, temperature regime, and the nature of drilling complications, the selection of various types of drilling fluids for different drilling intervals is substantiated. The properties of inhibited, polymer-based, and salt-saturated fluids prepared using domestic reagents (CMC-600, SAIPAN, HIPAN, NTF, TPFN, KSSB) are considered in detail. Using the method of experimental design, drilling fluid compositions were developed and their key parameters were determined, including density, rheological properties, filtration characteristics, static and plastic shear stress, pH, and others. It was established that the technological efficiency of the fluids depends on wellbore stability, the mineral composition of the rocks, and the thermobaric conditions of the geological section. The obtained results confirm the necessity of minimizing the solid phase content, reducing hydrostatic pressure on the formation, and limiting hydrodynamic impulses during tripping operations. As an optimal system, the use of a clay-free water-based drilling fluid formulated with starch, alkaline silicates, and aluminum sulfate, with CaCO₃ used as a weighting agent that has minimal impact on unconsolidated reservoirs, is recommended. The study demonstrates the importance of a comprehensive and scientifically justified approach to the selection of drilling fluids under conditions of elevated formation pressures.</jats:p>