API-gravity

Probably the simplest tool in discriminating between, notably, LNAPL product types is the measurement of API gravity. API gravity is similar to specific gravity but differs by the following conversion  

The common technique used to measure the API gravity of a hquid sample is with a hydrometer graduated in degrees of API gravity. The hydrometer is inserted in the liquid sample and allowed to float freely. When equilibrium is reached, the API gravity may be read from the exposed portion of the hydrometer. 

Gasoline Light crude Heavy crude Asphalt 

This industry standard that is based on ASTM D287/1298, is the single most utilized crude property measurement for making crude purchases. It is quite common for measurements to range from values in the low teens (asphaltic crude) to those having values in the 50 s (condensates). While this test normally is done by the hydrometer method and is simple to perform, it does have some crucial steps that need to be performed. The first step is to insure that the crude aliquot taken is representative. API is measured along with the temperature of the cmde that is then converted to an API at 60 °F (the industry standard). 

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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. 

There are no definitions for categorising reservoir fluids, but the following table indicates typical GOR, API and gas and oil gravities for the five main types. The compositions show that the dry gases contain mostly paraffins, with the fraction of longer chain components increasing as the GOR and API gravity of the fluids decrease. 

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... 

Water corresponds to an API gravity of 10 cmde oils fall between 10 and 60°AP1. The most common cmde oil values are in the 35—40° range. 

Three frequently specified properties are density—specific gravity—API gravity, characterization factor, and sulfur content (2,6,7). The API (American Petroleum Institute) gravity is a measure of density or specific gravity (sp gr) ... 

In the petroleum industry, a common indicator of specific gravities, known as the API gravity or °API, is usuaHy appHed to cmde oils. The formula for the API gravity is... 

Thus, the higher the specific gravity, the lower the API gravity. Water, having a specific gravity of 1, has an API gravity of 10. 

Heavy oil is another type of petroleum, different from conventional petroleum insofar as the flow properties are reduced. A heavy oil is much more difficult to recover from the subsurface reservoir. These materials have a high viscosity and low API gravity relative to the viscosity and API gravity of conventional petroleum (Fig. 1) (3,4), and recovery of heavy oil usually requires thermal stimulation of the reservoir. 

The definition of heavy oil is usually based on API gravity or viscosity, but the definition is quite arbitrary. Although there have been attempts to rationalize the definition based on viscosity, API gravity, and density (2,3), such definitions, based on physical properties, are inadequate, and a more precise definition would involve some reference to the recovery method. 

The API gravity of tar sand bitumen varies from 5 to ca 10°API, depending on the deposit, and the viscosity is very high. Whereas conventional cmde oils may have a high (>100 MPa-s(=cP)) viscosity at 40°C, tar sand bitumen has a viscosity on the order of 10-100 kPa-s(10 -10 P) at formation temperature (ca 0—10°C), depending on the season. This offers a formidable obstacle to bitumen recovery and, as a result of the high viscosity, bitumen is relatively nonvolatile under conditions of standard distillation (Table 4) (12,13), which influences choice of the upgrading process. 

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. 

Measured TBP and API gravity of feed, computed atmospheric pressure EFV (from API Technical Data Book), and molecular weight of feed ... 

No. Component name Molecular weight Specific gravity API gravity (Ibrnioiyh... 

API gravity. The specific gravity of petroleum or petroleum products is often expressed in terms of degrees API on a scale defined by... 

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. 

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