Multiphase Metering Experience in Russia's High-Viscous and Foamy Oil: Lessons Learned

Abstract

Abstract Russkoye field lies in the northern part of Western Siberia and has great oil reserves of over 1.3 billion tons. This is a unique field in terms of its complexity for development. Challenges include remote location of the field, surrounded by marshlands, and harsh Arctic climate, thick permafrost layer, heterogeneity and discontinuity of rocks made of poorly consolidated sandstones, presence of a large gas cap and an underlying aquifer, unique rheological properties of oil, high density, viscosity, tendency to form stable foam and emulsions. Combination of all these challenges brought considerable delays in formulation of an optimized field development plan and commissioning program. Accurate measurements of surface flow rates are key requirements for reservoir characterization and production monitoring on any oil field. Oil production rates, gas-oil ratios, water-cut data, physical, chemical and rheological properties of oil are especially critical at the test commercial production phase on wells of the Russkoye field. These data are the basis for monitoring production trends, gas breakthrough from the gas cap and water encroachment from the underlying aquifer, for inflow profiling in horizontal sections, optimizing well performance for enhanced oil recovery, and they allowed for solving primary engineering tasks arising during development and making production prognosis over the field life. As first effects were delivered for test commercial production on Russkoye field, some issues were encountered in collecting accurate and high-quality measurement data that would provide a good repeatability. To find the best solution for well flow rate measurements, attempts were made for some years to use test separators with different metering modules and a multi-phase flowmeter with Venturi tube and two-level gamma gage. All above equipment had been proved and certified. In addition, calibrated test tanks are used in some well pads for fluid rate measurements. The challenges associated with the accuracy of flow rate measurements are caused mainly by unique rheological properties of formation oil, in particular, its high density (940 kg/m3), viscosity at surface conditions (∼700 cP at 15 °C) and its tendency to form stable foam and emulsion. These factors, together with extreme low-temperature environments of the Arctic, forced JSC Tyumenneftegas engineers to look for an alternative engineering solution to achieve accurate flow rate measurements on Russkoye field.