ASSESSMENT OF BASIC GEOLOGICAL BEDDING CONDITIONS OF OPERATIONAL FACILITIES IN PRODUCTION FORMATION FLUIDS

Abstract

The total overburden pressure on the seam wing is greater than the lateral pressure, and on the fold dome, on the contrary, the lateral overburden pressure is greater than the total. As a result, the layer material flows from the wing zones to the domed part, as a result of which the layer thickness on the dome increases, which is noted in the studies of Soviet scientists. Investigating the mechanism of formation fracture during water injection, we found that high fracture pressures are observed in wells located in the lower parts of the structure (fold wings), and smaller ones in the higher parts (fold dome). When the stability of rocks in the near-wellbore part of the formation is disturbed during the operation of wells, studies have established that fresh water causes hydration and swelling or dispersion of clays, which act as a cementing material in the rocks. This can lead to both a decrease in permeability and the development of destruction processes in the near-wellbore part of the formation. Prevention of this effect during well development is achieved by using saline formation water or fresh water with additives of hydration inhibitors, such as NaCl (5-10 %), CaC12 (1-3 %), KC1 (1-3 %). Another type of well completion complications is clogging of the near-wellbore part of the formation. According to available data, mud-acid treatment restores the rock permeability by about 50 % of the original value, while conventional flushing does not exceed 30 %. Therefore, the fight against sand production in wells should begin even during their construction by the correct selection of working fluids. The stability of sand vaults was investigated with various forms of sand grains and saturation of sand with fluids during fluid filtration. Laboratory studies have established that the stability of the vaults depends on the degree of roundness of the sand and the saturation of the liquid. The presence of clay particles in the sand increases the stability of the vaults, and an increase in water saturation decreases it. This is confirmed by the results of the analysis of the effectiveness of the introduction of thermal methods for enhancing oil recovery of clay sandstones saturated with high-viscosity oil. Besides, another of the main rheological properties of the rock is creep. Significant creep is inherent in associated rocks (clays, mudstones, shales). Krivoy Rog rocks, for example, quartz-sericite shale and arkosic sandstone, have creep, averaging 20-35 % of the initial elasticity of deformation, with the greatest deformations occurring in the first 1.5-2 days of loading. It was found that to ensure the stability of the fixed part of the formation in the annulus of the bottomhole zone of the well, static equilibrium should be maintained in the porous medium. Rocks with low values of rheological properties (with a low relaxation rate) provide a longer resistance of the near-wellbore part of the formation to destruction during well operation.