During drilling through aquifers using the rotary drilling method with drilling fluid application, the phenomenon of formation clogging in near-well zone takes place. This leads to physical changes in pore spaces in consequence of the deposition solid phase particles originating from the drilling fluid. Due to this fact, filtration velocity in the clogged zones of the aquifer formation decreases, which results in increased pressure drawdown and decreased well hydraulic efficiency. Therefore, it causes a reduction of the well total capacity. The article consists of studies connected to the development of the mud which will constitute the basis for a complex mud system intended for hydrogeological drilling in different encountered geological conditions. In the framework of laboratory research, technological parameters of six, commonly applied in oil and gas industry, polymer agents as well as new agent developed at the Drilling, Oil and Gas Faculty AGH-UST in Krakow were examined. The undertaken studies showed that the new agent, marked as CAGEx, provides the required technological parameters and can be applied as a base for drilling muds intended for hydrogeological drilling. The undertaken industrial research of the new CAGEx drilling mud carried out while drilling water intake well, confirmed the great stability of its technological parameters as well as insignificant influence on rock permeability damage in filter zone. The water intake well is characterized by high hydraulic efficiency and does not require additional activation treatment.

Operations conducted by petroleum industry generate an entire range of drilling waste. The chemical composition of drilling waste and its toxicity depend primarily on the geological and technological conditions of drilling, the type of drilled rock deposits and on the type and composition of the drilling mud used. In the course of drilling operations, drilling fluids are in constant contact with bacteria, fungi and other organisms infecting the mud. Pioneer species, capable of surviving and using the resources of this specific environment, are selected. For this reason, the effectiveness of microbiota survival on different types of spent drilling muds and in different dilutions with brown soil was measured. Spent drilling muds samples came from drilling operations in various regions of Poland, e.g. Subcarpathia, the Polish Lowland and Pomerania regions. Oxygen consumption after 96 h was around 20 μg·g^‒1 dry mass in soil or soil/drilling water-based mud mixture. Soil mixes contained 10 wt% synthetic base, mud had a higher oxygen consumption – 38 μg · g^‒1 dry mass. Oxygen consumption decreases sharply as the content of the spent synthetic base mud fraction increases. A higher concentration of spent SBM (35 wt%) reduced the aerobic metabolism by slightly more than 50%. A high concentration of reduced carbon decreased the respiratory quotient (RQ) value to 0.7. All the researched drilling waste shows microbiological activity. At the full concentration of drilling fluids and non-dilution options, the chemical composition (salinity, inhibitors, etc.) strongly inhibits microbiota development and consequently, respiration