Some features of the properties of reservoir hydrocarbon systems in the development of gas-condensate deposits

Abstract

During the development of gas condensate reservoirs, the extracted product contains not only “dry” gases but also liquid hydrocarbons. These hydrocarbons are unstable in both content and the composition of the reservoir mixture as reservoir conditions change due to phase transitions. Therefore, to forecast development, it is advisable to use experimental data in geological and technological modeling. The compositional PVT model (construction of phase process diagrams) requires current data on the component composition of fluids. This information is important for obtaining accurate initial parameters for field development forecasting. The study notes that to achieve a positive result with an accuracy of approximately ±3 to 5%, the following conditions were met during the study: the capacity of the field separator ensured the entrainment of liquid droplets in the reservoir mixture of no more than 4 cm3/m3. Based on integrated measurements taken during separation sampling, the condensate-gas ratio (CGR) and the physicochemical characteristics of the condensate (density, dynamic viscosity, and other properties) were determined. Based on the analysis of the obtained results, the saturated condensate yield (SCY) was determined; it varied over a wide range, ranging from 69.8 g/m3 to 513.2 g/m3 of separation gas. Changes in the gas condensate mixture properties were observed with a decrease in reservoir pressure from 29.89 to 26.33 MPa. This decrease in pressure led to the formation of a depression funnel in the near-wellbore zone and resulted in the influx of a two-phase hydrocarbon mixture. Also, based on the PVT data, the dependences of the precipitated liquid phase on pressure were constructed for the gas condensate system under study. The predicted condensate recovery factor was experimentally determined, and the condensation pressures of hydrocarbons in the reservoir system were measured.