Density and Viscosity of Hydrocarbons at Extreme Conditions Associated with Ultra-Deep Reservoirs-Measurements and Modeling

摘要

There is a lack of experimental density and viscosity data particularly at extremely high temperature, high pressure (HTHP) conditions associated with ultra-deep petroleum formations found at depths of approximately 20000 ft or more, where the pressure and temperature can reach as high as 35000 psia and 500oF, respectively. In many applications, such as the simulation of oil reservoirs and the design of transport equipment, it is more convenient to use models to obtain such properties. However, development of reliable models requires sufficient experimental data that cover the entire temperature and pressure ranges of interest.udA HTHP density prediction model has been developed by utilizing the concept of volume- translation (VT) in the SRK and PR equations of state. The new proposed model provides very accurate density predictions over a wide range of temperature and pressure. The overall mean absolute percentage deviation (MAPD) of 1-2% obtained with the new model is substantially lower than those calculated with other models considered in this study.udA novel windowed, high temperature, high pressure rolling ball viscometer was designed and constructed specifically for this project. The viscometer has been calibrated with n-decane and used to measure the viscosity of n-octane for temperatures to 500oF and pressures to 35000 psia. A literature review of different viscosity models has shown that the friction theory and free volume theory models are superior to many other viscosity models. A correction term added to the F-theory model has been proposed to get more accurate predictions.udIn the oil industry, there is a need to identify a viscosity standard that is representative of light oils produced from ultra-deep formations found beneath the deep waters of the Gulf of Mexico. Deepwater viscosity standard (DVS) is a liquid that would exhibit a viscosity of roughly 20 cP at 500oF and 35000 psia. This work suggests Krytox® GPL 102 as a promising candidate for a HTHP DVS. The windowed rolling ball viscometer calibrated with dioctyl phthalate were used to determine the viscosity of Krytox® GPL 102, and all of the results were modeled with scaling theory.ud