Crude oil API gravity

Fig. 4. Box plot distribution of Kuparuk A and Kuparuk C crude oil API gravity.

As a rule of thumb, both vanadium and nickel increase with the asphaltic content of the crude oil (API gravity is an indicator). The lighter oils contain less metal. With some exceptions, the... 

The simultaneous application of these two chemical processes in an appropriately chosen field was not a problem, because the required ranges for crude oil API gravity, reservoir temperature, and reservoir water salinity were about the same for both processes. 

Figure 3. Correlation between crude oil API gravity and sulfur...

Crude Oil API Gravity Specific Gravity Sulfur (wt%) Nitrogen (wt%)... 

Accurate determination of the gravity of crude oil is necessary for the conversion of measured volumes to volumes at the standard temperature of 15.56°C (60°F) (ASTM D1250, Petroleum Measurement Tables). Gravity is also a factor reflecting the quality of crude oils. API gravity is a special function of relative density (specific gravity) represented by the following ... 

The objective of this chapter is to present the definition and classification of heavy petroleum, as well as describe the main properties that characterize heavy crude oils (API gravity, viscosity, asphaltenes content, etc.). Definition, application, and types of assay for crude oil are provided together with detailed experimental information about the assays of various crude oils. The problems faced during different steps of production, transportation, upgrading, and refining of heavy petroleum are also highlighted. 

Crude Source API Gravity Vacuum Bottoms, vol% Total Nitrogen of Heavy Vacuum Gas Oil, PPM... 

Either American Petroleum Institute degrees (°API) or specific gravity provides information on the paraffinic or aromatic nature of crude. The API gravity of most crude oil falls between the range of 20°API to 45°API. 

Table X shows the results of calculations for two RCC tests made on the same feedstock. The predictions are consistent with actual yields. Tables XI and XII are also results of slurry oil plus coke yield predictions from various reduced crudes. All prediction made in Tables X-XII were made with reduced crudes having an API gravity of 10-20. The saturates and monoaromatics factors change as the API gravity of the reduced crude feedstock changes. Tables XIII and XIV give the results of slurry oil plus coke predictions for West Texas Intermediate and Illinois Basin reduced crudes. These two reduced crudes have API gravities of 20-30. Again consistent predictions were made.

It is clearly seen that the heavier crudes (low API gravity) exhibit much more difficulty to fiow as compared with lighter oils (high API gravity). 

Specific gravity is important commercially because the crude oil price depends partly on this property. The specific gravity is expressed most often in degrees API (see Chapters 1 and 4). 

The API gravity of water is 10°. A light crude oil would have an API gravity of 40°, while a heavy crude would have an API gravity of less than 20°. In the field, the API gravity is readily measured using a calibrated hydrometer. 

The oil density at surface is readily measured by placing a sample in a cylindrical flask and using a graduated hydrometer. The API gravity of a crude sample will be affected by temperature because the thermal expansion of hydrocarbon liquids is significant, especially for more volatile oils. It is therefore important to record the temperature at... 

A crude-oil assay always includes a whole crude API gravity and a TBP curve. As discussed by Nelson (op. cit., pp. 89-90) and as shown in Fig. 13-85, a reasonably consistent correlation (based on more than 350 distillation curves) exists between whole crude API gravity and the TBP distillation curve at 101.3 kPa (760 torr). Exceptions not correlated by Fig. 13-85 are highly paraffinic or naphthenic crude oils. 

The oil for an oil-base mud can be diesel oil, kerosene, fuel oil, selected crude oil, or mineral oil. There are several requirements for the oil (1) API gravity = 36° - 37°. (2) flash point = 180°F or above, (3) fire point = 200°F or above, and (4) aniline point = 140°F or above. Emulsifiers are more important in oil-base mud than in water-base mud because contamination on the drilling rig is very likely, and it is very detrimental to oil mud. Thinners, on the other hand, are far more important in water-base mud than in oil-base mud oil is dielectric, so there are no interparticle electric forces to be nullified. 

The API (American Petroleum Institute) gravity is another way to express the relative masses of crude oils. The API gravity could he calculated mathematically using the following equation ... 

The crude oil produced from the Main Zone of the Torrance Field has an API gravity of 18° and contains 5.3 weight percent asphaltenes. The solubility of the asphaltene molecules in Main Zone oil was measured by the Oliensis Test(35). In this test, the solubility parameter Qf ie oil was lowered by adding to the oil successively larger volumes of hexadecane, a poor solvent for asphaltene molecules. The minimum volume (in milliliters) of hexadecane, which when added to 5 g of crude oil, will cause the chromatographic separation of the asphaltene fraction is termed the Oliensis Number. The Oliensis Number for the Main Zone crude oil is 3, indicating that the asphaltene molecules are not well-solubilized in the oil. Small changes in the solubility parameter of the Main Zone oil can cause the asphaltenes to precipitate. 

Figure 2. Change in quality (API gravity) of imported crude oils in US.

EIA, Percentages of Total Imported Crude Oil by API Gravity 2006. [cited 2006 June] Available from http //tonto.eia.doe.gov/dnav/pet/pet move ipct k a.htm. 

In general, upgrading concerns to those processes in which the API gravity of the crude oil or its viscosity decrease. Numerous reducing viscosity methods for heavy oil are currently commercialized [407], involving different means, such as physical methods... 

When petroleum occurs in a reservoir that allows the crude material to be recovered by pumping operations as a free-flowing dark- to light-colored liquid, it is often referred to as conventional petroleum. Heavy oils comprise the other types of petroleum they differ from conventional petroleum in being much more difficult to recover from subsurface reservoirs. The definition of heavy oils is usually based on the API gravity or viscosity value, and the definition is quite... 

For many years, petroleum and heavy oil were very generally defined in terms of physical properties. For example, heavy oil was considered to be a crude oil that had gravity between 10 and 20° API. For example. Cold Lake heavy crude oil (Alberta, Canada) has an API gravity equal to 12°, but extra-heavy oil (such as tar sand bitumen), which requires recovery by nonconventional and nonenhanced methods, has an API gravity in the range 5 to 10°. Residua would vary depending on the temperature at which distillation was terminated, but vacuum residua were usually in the range 2 to 8° API. 

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