Analysis of mining and geological conditions of a long borehole drilling on Talnakh ore cluster

Relevance of the work is caused by the necessity to drill the exploratory wells for searching rich copper-nickel ores at deep levels and flanks of Talnakh ore cluster. The main aim of the study is to analyze geological and technical conditions of drilling deep wells on Talnakh ore cluster; to study rock samples for further development of well construction technology using the complexes with removable core tubes. The methods used in the study: visual core description, analytical researches using the methods of X-ray fluorescence spectrometry, electron microscopy, X-ray, spectroscopic and tomographic analysis to determine the mineral composition of argillaceous rocks; labora tory testing of samples of chloritized rocks; calculations of pressure loss while drilling using complexes with removable core tube with polymer solution. The results. Analysis and research of geological material of Talnakh ore cluster showed that the instability of the walls of wells occurs due to stress state of rock mass and a specific mineral composition of the material filling the cracks of ore zones and composing the walls of wells in sedimentary sequences. The analytical researches revealed that the samples are porous rocks mixture (0,1-5 microns) of crystalline and amorphous minerals. Destruction of mudstone and gabbro-dolerite collapse when interacting with water-based drilling fluids occur due to their mineral composition, in particular with the presence of chlorite and montmorillonite. Water penetrates into the micropores and microcracks which promotes disclosure cracks, hydration of clay minerals with sliding pads formation and as a consequence, leads to destruction. Calculation of the pressure loss showed the need to develop diamond crowns with an outer diameter of 80-82 mm for drilling with the complex with a wireline in difficult geological conditions of Talnakh ore cluster.