Wednesday, February 18, 2009

Oil characterisation

Process simulation is very crucial when designing any equipment in oil facilities or refineries since the physical properties of oils will dictate the size of equipment. Therefore, process simulation software is used when conducting conceptual study of any new field or refinery even for FEED.
In order to characterize the crude from different wells, lab analysis needs to be done by petroleum engineers and/or geologist. The analysis to be done should align with requirement of process engineer when characterizing the crude simulation software. Since physical properties calculated from simulation software and the stream of the oil is defined through lab analysis keyed in manually from data collected by petroleum engineers. So, data must be representative of the oil field to be developed. Those lab analysis really needed for process simulation must be consists of density, viscosity (two different temperatures), and true boiling points (TBP). These data can be used for both oil facility and refinery.
However, some petroleum engineers would do chromatograph method when analyzing newly found oil from fields. There are some circumstances to be considered when choosing one of the methods.
There are two approaches that can be considered when analyzing newly found oil which are boiling points and chromatograph method:-

Boiling points:-
This is boiling point method can used to characterize the crude for both oil facility and refinery. This is because can give various level of gas and oil since the oil is being categorized by different cut-point which refer to the boiling points. Hence, refineries need this test’s result when modeling simulation model for refineries. This is because refinery itself will separate the crude or condensate into different categories of gas and oil such as natural gas, liquefied petroleum gas, naphta, kerosene, diesel, etc and it really needs different cut points to separate it. This only can be done through characterization of crude by boiling points. However, this method more expensive to test in lab compared to chromatograph and this makes newly found oils are being tested by chromatograph method when characterizing crude to design oil facility (onshore or offshore). This is because the main function of oil facility is to separate among oil, gas, and water, whereby, refinery requires more than that.
Chromatograph method can be used for both oil characterization of oil facility and refinery. However, to run chromatography analysis for unknown of carbon number of hydrocarbon might cost really high compared to boiling point lab test. Therefore, chromatograph method usually is being used for only for oil facility purposes which require lesser analysis of carbon chain. Normally, the oil will be tested up to C30+, where the heavies will be lumped as one component. Cost wise, chromatograph method is considered viable if the test will be done up to C30. So, this approach only can be used for oil facility since the function of oil facility just to separate among oil, gas, and water. Whereby, the function of refinery is to process further on heavies who are having group of products and it needs more detail of the cut points. Therefore, it is advisable to characterize crude in different approach for both oil facility and refinery.

So, boiling point approach can be used for both characterization but relatively more expensive for oil facility relative to chromatograph method. Chromatograph method can be used still for both cases but relatively more expensive for refinery. As a conclusion, boiling point lab test result more viable and practical to use for refinery application and chromatography analysis for oil facility application.

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