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Experimental Investigation of the Rheological Properties of a Typical Waxy Crude Oil Treated with Supercritical CO2 and the Stability Change in Its Emulsion
journal contribution
posted on 2019-05-13, 00:00 authored by Guangyu Sun, Chuanxian Li, Shuang Yang, Fei Yang, Yaqun ChenThe
application of supercritical CO2 (scCO2)-flooding
technology is increasing worldwide. After a waxy crude oil is treated
with scCO2, its composition and rheological properties
are changed and the stability of its emulsion is accordingly altered
as well, thus affecting the dewatering process in gathering stations.
To probe the specific changes occurring in waxy crude oil and its
emulsion after scCO2 flooding, a scCO2 treatment
device was first designed to simulate the reservoir conditions. Next,
the composition changes in the waxy crude oil caused by the scCO2 treatment were studied, and the changes in the rheological
properties, such as the pour point, viscosity, yield stress, and wax
precipitation characteristics, caused by the composition variation
were analyzed. Then, the stability of the degassed crude oil emulsion
and the corresponding interfacial properties were examined. Finally,
the demulsification characteristics of the emulsion under the action
of a demulsifier were tested. The results reveal a content increase
in the heavy components, such as asphaltenes, resins, and high-carbon-number
hydrocarbons, in the waxy crude oil as a result of the scCO2 extraction of the light components. This results in increases in
the pour point, wax appearance temperature, and abnormal point as
well as the growth of the apparent viscosity and yield stress. As
a result of the structural enhancement of the interface, as reflected
by the dilational modulus increase in the interface, the stability
of the scCO2-treated waxy crude oil emulsion is strengthened
and its demulsification efficiency is reduced after dosing with the
same demulsifier. All of these changes could unfavorably influence
the safe transportation of the produced fluid in scCO2-flooding
oil fields and the subsequent dewatering process.