Porosity of a material is defined as that fraction of the bulk volume of this material that is not occupied by the solid framework of the material.In oil reservoirs,the porosity represents the percentage of the total space that is available for occupancy by eighter liquids or gases.It determines the storage capacity of the sand and is generally expressed on a percentage basis or as a fraction or a decimal.

One may distinguish two types of porosity,namely,absolute and effective:

Absolute porosity is the percentage of total void space with respect to the bulk volume regardless of the interconnection of the pore voids.

Effective porosity is the percentage of interconnected void space with respect to the bulk volume.

Grain volume methods:In these methods the consolidated sample is solvent extracted and dried;the bulk volume is determined eighter by the displacement of a liquid which does not penetrate the sample or by saturating the sample and volumetrically displacing a suitable li

Mercury-injection method:When a rock has a very small fraction of void space,it is diffucult to measure it by methods previously discussed.One may then resort to forcing a noncompressible liquid into the sample under very high pressure.The original idea appears to have been that of Horner(1944).

Bulk volume determination:The bulk volume of the extracted and dried samples may be determined by volumetric displacement of mercury.

Retort method: the procedures discussed above are nearly all combinations or modifications of methoads previously described in the availble literature which have been found satisfoctory in handling a great variety of core samples with various requirements of rapididty and accuracy. Other methods have been tested and found to be less desirable, such as the retort method( Yuster and Levine, 1938). The main objection to the retort method, still in common use, is the cracking of the oil with the resluting production of gases and the possibility of driving out water of crystallization.

It is obvious that the percentage of porosity may be calculated from such data by use of eighter of the two following relationships:

Per cent porosity=100x(bulk volume - grain volume/bulk volume)

Some common words found in the essay are:
Measurements Grain, Thornton Marshall, POROSITY Porosity, SATURATIONS Methods, Taylor1938 Titration, Horner1944 Loss, Yuster Levine, Dean Stark, Locke Bliss1950, Porosity MeasurementIn, bulk volume, capillary pressure, core samples, pressure curves, loss weight, capillary pressure curves, retort method, fluid saturation, fluid saturation determinations, porosity percentage, absolute porosity, percentage total, space respect bulk, void space respect, respect bulk volume,
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