Assignment Help With Porosity


Fluid retaining capacity of reservoir rocks is called porosity. Mathematically it is ratio of void space in the rock to the bulk volume of the rock. In reservoir rocks there exist basically two types of porosity, expressed as …

  1. Original porosity and
  2. Induced porosity.

Porosity evolved through depositional environment is called original porosity, while Induced porosity is change form of original porosity due to geological changes basic structure of rocks. Following are the classifications of rock and its different porosity…

Rock Original Porosity Induced Porosity
Sandstone Intergranular Fracture development
Limestone Intercrystalline and oolitic Vugs and solution cavity

Rock having original porosity is more uniform in their characteristics than those rocks in which a large part of the porosity is induced. The porosity for the cubical packing arrangements is 47.6% and that of rhombohedral is 25.96%. In fact porosity of reservoir rock does not depend upon the grain size. Sometimes cementing material may seal off a part of the pore space, so we have to define porosity in some other words …

Petroleum Engineering Assignment Help Order NowTotal Porosity: It is the ratio of total void space in the rock to the bulk volumes of the rock.

Effective Porosity: It is the ratio of the interconnected pore void space in the rock to the bulk volume of the rock. Effective porosity is more important for reservoir engineering point of view. For tightly cemented material there is significant difference between effective porosity and total porosity. One important application of the effective porosity is its use in determining the original hydrocarbon volume in place. Consider a reservoir with an areal extent of A acres and an average thickness of h feet. The total bulk volume of the reservoir can be determined from the following expressions:

Bulk volume = 43,560 Ah, ft3


Bulk volume = 7,758 Ah, bbl

Where A = areal extent, acres

h = average thickness

The reservoir pore volume PV can then be determined by combining

Expressing the reservoir pore volume in

Cubic feet give:

PV = 43,560 Ahf, ft3

Expressing the reservoir pore volume in barrels gives:

PV = 7,758 Ahf, bbl

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