Study on the Effects of the Rheological Properties for Flow Behaviour of Assam Crude Oil with Various Chemicals

Abstract

The crude oil exhibit Non-Newtonian flow behaviour which results in serious problems related to its transportation from oil fields to refineries. The rheological behaviours of different Assam crude oil namely Jorajan, Bhogpara, Lakwa and Kothaloni with or without surfactants were studied in the present work. The crude oil mixtures for the study were prepared by blending with kerosene. Anionic surfactant BL (Black Liquor) and Chrome free lignosulphonate and non-ionic surfactant TX100 (Triton X100) were used. Rheological experiments were carried out by Grace M3600 viscometer. The experimental data’s was interpreted with the model of Ostwald-de Waele power-law and Bingham Plastic with the entire range of data at 40 °C and 80 °C. Hence the required shear stress or yield stress was obtained for the crude oil mixtures.

Effect of several parameters like shear rate, temperature, density and rpm and addition of kerosene on viscous behaviours had been studied. Crude oil of Kothaloni oil field having API gravity of 36⁰ was mixed with CMC values of different surfactants which are 0.6% Black Liquor, 0.04% TX100, 4% of 1 Molar Chrome free lignosulphonate and 5% Kerosene. On investigation it was observed that there was a significant decrease in dynamic viscosity and increase in shear stress with increase in shear rate after adding non ionic surfactant TX-100, anionic surfactants Black liquor and liqnosulphonate as compared with the pure crude oil. Further, there was significant decrease in dynamic viscosity when 5% kerosene was added with the surfactants. The experimental results showed that viscosity of an anionic surfactant Black liquor when mixed with crude oil decreased by almost 19.10% on addition of 0.6%wt/v of the surfactant at shear rate 1021.3 s⁻¹ and at a temperature of 40 °C. The purpose was to observe the viscosity reduction at a maximum speed of 600 rpm and at room temperature. Shear stress of the above mixture was also reduced by almost 15.38%. Viscosity of the mixture was further reduced by almost 70.78% on addition of 5% kerosene to the above mixture. Again, by adding different anionic surfactant chrome free lignosulphonate (4% wt/v) to crude oil a viscosity reduction of 16.85% and shear stress reduction of 14.28% was observed. Viscosity was further reduced to 68.53% and shear stress to 68.13% when kerosene was added to the above mixture. Another non-ionic surfactant TX-100 resulted in a viscosity and shear stress reduction of 12.34% and 12.08% respectively. Further addition of kerosene reduced its viscosity to 65.17% and shear stress 64.83%. It was observed that black liquor generally exhibited better reduction of viscosity than lignosulphonate. Also by mixing two crudes of different API (one lighter, Jorajan 5 and the other heavier, Kothaloni) a reduction of 66.29% viscosity and 65.93% shear stress was observed. This was solely done in order to show that when two pipes carrying crude of different API from different well heads, the crudes gets mixed and flows through one pipe towards the same oil collecting stations, thus facilitating the flow of heavy crude by reducing its specific gravity and enhancing the property of heavier crude oil.