Heavy Crude Oil Dewatering Processes for Fluid Property Measurements: Comparison, Impact, and Suitability of Methods

CATEGORY: HEAVY CRUDE 
Heavy Crude Oil Dewatering Processes for Fluid Property Measurements: Comparison, Impact, and Suitability of Methods

Type	Conference Paper
Author	Hongying Zhao
Author	Afzal Memon
URL	http://www.onepetro.org/doi/10.2118/174465-MS
Date	2015
Abstract	While a representative clean heavy oil sample is critical to obtain accurate fluid property data, required for heavy oil production, processing, and transportation designs, it is challenging to remove water from a heavy oil sample due to its near-water density and high viscosity. Researchers investigated three heavy oil dewatering techniques, determining their impact on heavy oil properties, and recommending suitable method(s) for preparing heavy oil samples for laboratory fluid phase behavior and property measurements. The three demulsification methods, centrifugation, the addition of demulsifiers, and distillation, were evaluated and compared. Researchers selected three dead heavy oil samples ranging from 20 to 11 API gravity degrees and with viscosities ranging from 100 to 5,000 mPa·s at 310.9 K (38°C). They prepared a stable emulsion with a 30 vol% synthetic brine using each heavy oil sample, which they used to evaluate each of the demulsification methods. Study results revealed that centrifugation had minimal impact on sample properties, although it was difficult to reduce the residual water content below the dewatering target of less than 1 wt%. The addition of chemical demulsifiers followed by mild centrifugation resulted in samples that met the dewatering target. The change in fluid properties caused by the demulsifier method was similar to the minor changes observed by the centrifugation method. Distillation could remove water from all three emulsions to below the dewatering target, if appropriate experimental procedures were followed. However, distillation had the strongest impact on dewatered oil properties due to the loss of light/intermediate components, despite precautions to minimize the mass loss. In current open literature, the effect of the heavy oil sample preparation procedure on the measured heavy oil properties and PVT data is rarely reported in detail, which makes it a challenge to properly perform the data interpretation and use them in relative modelling and design work.