Over the past decades, high-viscosity and heavy oil fields have been explored and put on stream. Generally, these oils have viscoplastic properties due to high-molecular-weight components, such as resins and asphaltenes. This paper presents some aspects of producing oils that behave like non-Newtonian fluids. Based on the analysis of crude oil rheology in Tatarstan fields, interpretation technique has been developed for the available data to be used in reservoir simulators. This paper reviews various fluid types and analyzes viscosity versus shear rate. It is concluded that in reality, fluids often demonstrate pseudo-plastic characteristics with yield limits, and require more complicated equations to characterize their flow behavior, compared to Newtonian fluids.
By the example of Bobrik horizon, the Melninsky field, pressure differential –viscosity relationship has been identified wherein simulated cutoff values of these parameters yield a 5% error, compared to the case without regard to oil viscoplastic properties. Numerical studies prove the necessity of considering the structural and mechanical oil properties. When modeling oil fields where these properties are well-pronounced, pressure gradient distribution maps should be used based on isobar maps to identify the most promising areas for reservoir stimulation operations, including infill drilling, reservoir pressure maintenance, and formation heating. Optimization of reservoir pressure maintenance system and denser well spacing pattern increase sweep efficiency and maintain pressure differential required for heavy oil flowing while providing a larger radial extent of the reservoir. Formation heating reduces the effect of viscoplastic properties in the zones with low oil mobility.
