Undersaturated Oil Viscosity Correlation for Adverse Conditions

摘要

The determination of viscosity is required for evaluation of thernpressure drop resulting from flow through porous media,rntubing or pipelines. Viscosity is a necessary property tornascertain well productivity or to properly size tubing, pipelinesrnand pumps. Numerous methods exist to estimate viscosity forrncomputer calculations. Oils encountered in deep waterrnenvironments are often highly undersaturated – in some casesrnin excess of 15,000 psi. For transport, the dead oil must bernpumped in an environment with temperatures as low as 35°F.rnAt this temperature, the dead oil atmospheric viscosity can bernin excess of 500 cp. The pressure required to pump oilrnthrough pipelines from deep water can exceed 3000 psi at thernpump on the platform and over 5000 psi at the sea floor. Thernpressure effect on viscosity results in a significant additionalrnincrease in this property which can adversely affect pipelinernperformance. The existing methods for estimatingrnundersaturated viscosity were not developed using data thatrnencompasses the pressure or viscosity range that are currentlyrnencountered by the industry. A large database comprised ofrn1,399 oils and 10,248 data points was constructed to evaluaternthe accuracy of existing correlation methods. Pressurerndifferentials up to 25,000 psi and viscosity in excess of 1000rncp are included in the database to ensure that viscosity at bothrntypical conditions and the extreme conditions encountered inrndeep water are represented. The existing methods are shownrnto be inadequate over this wide range of conditions. A newrnmethod was developed that offers improved accuracy andrnconsistency over the expanded range of viscosity and pressurerndifferential.