TECHNOLOGICAL COMPLICATIONS (FORMATION DAMAGE) DURING CO2 INJECTION FOR ENHANCED OIL RECOVERY. Part 1. GEOCHEMICAL PROCESSES INVOLVING ROCK MINERALS, CHANGE OF PETROPHYSICAL AND GEOMECHANICAL ROCK PROPERTIES

Decrease in permeability, porosity, change in wettability of oil-bearing formations during field development are defined by a general term - formation damage, which occur at various stages of field development, including drilling, production, application of enhanced oil recovery methods, well stimulation technologies with acid compositions, hydraulic fracturing and well workover. Reservoir damage leads to a reduction in the oil and gas content of reservoirs and in the economic efficiency of operation. In this regard, it is important to understand and prevent formation damage based on experimental and analytical methods, the applicationof which will minimize damage to the oil and gas bearing reservoir. The review considers anthropogenic processes that cause damage to oil and gas reservoir when CO2 is injected by various methods to enhance oil recovery. The processes of interaction of CO2 with formation rock are considered in detail. The main geochemical transformations of rock minerals are given, which lead to changes in the structure of pore space, permeability and porosity, decrease of geomechanical properties. Secondary sedimentation processes and risks of rock particles removal into the borehole are discussed.