Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

A capillary tube viscometer is designed and constructed for the measuring viscosities of incompressible crude oils without any prior information on the composition and thermodynamics. Compared with the rolling ball viscometer, the devised equipment is very cost-effective in construction. With the combination of a ultra-accuracy quantitative pump and a precise differential pressure gauge, the optimum fluid velocity can be easily found depending on the specification of the capillary tube and the differential pressure transducer. For the verification of the experimental accuracy, the viscosities of water and n-decane were measured. The measured values showed a good agreement with the theoretical values. Experimental errors were less than 3% except for measurements at 35oC for the water and at 72.4oC for the n-decane. Under the isobaric condition of 1062.28 psia, the viscosities of Dubai and Arabian Medium crude oil were measured at various temperatures. From the curve fitting, the viscosity as a function of temperature is m = -4.75×log T + 23.32 for Dubai and m = -7.82×log T + 37.99 for Arabian Medium crude oil. In case of Arabian Medium crude oil, additional measurements were made with changing both temperature and pressure. The result showed the general characteristics of liquid viscosity such as temperature and pressure effect. The equipment devised in this study could be an economical alternative to the rolling ball viscometer, satisfying the high technical demand of experimental conditions. It may be used as a fundamental tool for the basic and advanced studies on the fluid properties as well.