secondary porosity. 1. n. [Geology] The porosity created through alteration of rock, commonly by processes such as dolomitization, dissolution and fracturing. See: diagenesis , diagenetic porosity , dolomitization , fracture porosity , moldic porosity , porosity , primary porosity , vugular porosity. Photomicrograph of secondary porosity in sandstone.
What is the difference between primary porosity and secondary porosity?
Some reservoirs have distinct primary and secondary porosity. Primary porosity is the original porosity of the rock when it formed, and secondary porosity is the pore space created by subsequent processes such as fracturing.
Do siliciclastic rocks have primary or secondary porosity?
In contrast, some carbonate rocks have more secondary porosity than primary porosity. Permeability in siliciclastic rocks commonly varies more strongly with primary intergranular porosity than with secondary intragranular porosity.
What is the porosity of a rock?
It is written as either a decimal fraction between 0 and 1 or as a percentage. For most rocks, porosity varies from less than 1% to 40%. Primary porosity is the amount of empty space caused by the creation of the rock itself. Secondary porosity is the amount of space created after the rock was formed, such as a crack in the rock.
What is the relationship between secondary porosity and dissolution pathway?
The secondary porosity increases by about 6%. In the early burial stage, volcanic rocks are subjected to overlying strata compaction, cementation of carbonate and quartz, tectonic activity, and others, forming dissolution pathways consist of primary pores, dissolution pores in hypergenic stage, structural fractures, and large-scale fractures.
What is secondary porosity in geology?
Primary porosity is the original porosity of the rock when it formed, and secondary porosity is the pore space created by subsequent processes such as fracturing.
What are the examples of secondary porosity?
Secondary porosity is formed from postdepositional processes, such as dissolution, reprecipitation, and fracturing. Fractures, root channels, and animal burrows are some examples of secondary porosity. Total porosity is the sum of the primary and secondary porosities.
What causes secondary porosity?
Secondary porosity can develop before the burial, after the burial, or as a result of other tectonic activity. Shrinkage of certain minerals creates fractures, and porosity increases. Dehydration of mud and recrystallization of minerals produces secondary porosity.
How do you find secondary porosity?
Secondary porosity is classically estimated from well logs as the difference of total density porosity minus total sonic porosity φf ≅ φd - φs. It is applicable to either carbonate rocks or clastic sandstones that may or may not contain clays.
What are the two main types of porosity?
Dissolution porosity is the pore space formed from the partial to complete dissolution of framework grains and/or cements. Fracture porosity is the void space associated with natural fractures.
What is secondary permeability?
Secondary permeability The permeability developed in a rock after its deposition, through such processes as weathering and fracturing. Secondary porosity The porosity developed in a rock after its deposition, through such processes as dissolution or fracturing.
What factors affect porosity?
The principal factors that control porosity are grain size and shape, the degree of sorting (a well-sorted sediment has a narrow range of grain size), the extent to which cement occupies the pore spaces of grains and the amount of fracturing.
What is the difference between permeability and porosity?
More specifically, porosity of a rock is a measure of its ability to hold a fluid. Mathematically, it is the open space in a rock divided by the total rock volume (solid and space). Permeability is a measure of the ease of flow of a fluid through a porous solid.
What is the meaning of porosity in science?
Porosity is defined as the ratio of the volume of pores to the volume of bulk rock and is usually expressed as a percentage.
How do you find primary porosity?
The first equation uses the total volume and the volume of the void. Porosity = (Volume of Voids / Total Volume) x 100%. The second equation uses the total volume and the volume of the solid. Porosity = ( ( Total Volume - Volume of the Solid ) / Total Volume ) x 100%.
What is the unit of porosity?
Porosity is also known as "pore space." The weight of an individual soil particle per unit volume. Particle density is usually expressed in units of grams per cubic centimeter (g/cm2).
What is porosity of a material?
Porosity is the volumetric fraction of pores in the material. These pores can be located on its surface or in its internal structure. Porosity is associated with the density of the material, and with the nature of its compounds and the existence of empty spaces between them.
Which of the following are part of primary porosity?
The primary porosity of granular material is affected by the shape and packing of grains, the distribution of grain sizes (sorting and uniformity) and the porosity of the particles themselves (Figure 10). The degree of cementation during lithification of sedimentary rocks will also affect the primary porosity.
What is the difference between permeability and porosity?
More specifically, porosity of a rock is a measure of its ability to hold a fluid. Mathematically, it is the open space in a rock divided by the total rock volume (solid and space). Permeability is a measure of the ease of flow of a fluid through a porous solid.
What is Cul de Sac pore?
Cul-de-sac pores [dead end] are those pores that have only one throatpassage connecting with another pore. Closed pores [isolated] are those have no communication with otherpores.
Which of the following material has lowest porosity?
Igneous or metamorphic rocks have the lowest primary porosity because they commonly form at depth and have interlocking crystals.
What is secondary porosity?
Secondary Porosity. Secondary porosity is the result of geological processes (diagenesis and catagenesis) after the deposition of sediment. The magnitude, shape, size, and interconnection of the pores may have no direct relation to the form of original sedimentary particles.
What is the primary and secondary porosity of a reservoir?
Some reservoirs have distinct primary and secondary porosity. Primary porosity is the original porosity of the rock when it formed, and secondary porosity is the pore space created by subsequent processes such as fracturing. Warren and Root (1963) developed the dual-porosity (or ‘double-porosity’) model to represent this type of reservoir, in which there are regions that contribute to the pore space but not the flow capacity. This true in practice as not all pores are connected. A real-world reservoir cut by fractures ( Fig. 5.8A) is represented by regularly spaced matrix blocks, connected by straight and evenly spaced fractures ( Fig. 5.8B ).
What is the response of a dual porosity model?
The dual-porosity model has a characteristic pressure derivative response ( Fig. 5.9 ). The first reservoir response is from the fractures as they have greater transmissivity and are connected directly to the wellbore. There is a flat derivative associated with this (and semilog straight line). After some period the primary porosity in the matrix will begin to respond, flowing into the fractures and causing the pressure derivative to dip, though once established will return to the flat derivative (second semilog straight line) ( Horne, 1995 ).
What causes porosity in rocks?
Solution porosity: Channels due to the solution of rocks by circulating warm or hot solutions; openings caused by weathering, such as enlarged joints and solution caverns; and voids caused by organisms and later enlarged by solution.
What is fracture porosity?
Fracture porosity: Openings created by structural failure of the reservoir rocks under tension caused by tectonic activities such as folding and faulting. These openings include joints, fissures, and fractures. In some reservoir rocks, such as the Ellenberger carbonate fields of West Texas, fracture porosity is important. Porosity due to fractures alone in the carbonates usually does not exceed 1% [ 7 ].
Which type of rock has primary porosity?
Primary porosity is dominant in clastic—also called detrital or fragmental—sedimentary rocks such as sandstones, conglomerates, and certain oolitic limestones [ 7 ]. However, it is important to emphasize that both types of porosity often occur in the same reservoir rock. View chapter Purchase book. Read full chapter.
Is adsorption in the primary or secondary porosity?
The above examples are fundamentally related to the adsorption in the primary porosity [ 100]. The utility of the adsorption in the secondary porosity [100] is evidenced in the use of natural and synthetic zeolites as solid electrolytes, since the cationic conduction of zeolites is highly enhanced by the adsorption of water in the secondary porosity [ 15, 101 ].
What is secondary porosity?
A rock that is fractured or weathered (including solutioned) after its initial formation has secondary poros ity. Whether the porosity is primary or secondary, the combined properties are included in the effective porosity. In most cases, the development of secondary porosity increases the effective porosity of a porous material.
What are the two phases of porosity?
The porosity of earth materials originates during two phases: 1) during the deposition of sediments, lithification or cooling of crystalline rock; and 2) after deposition as the earth material is exposed to other conditions such as compaction, weathering, fracturing and/or metamorphism. As a result, earth materials can have porosities dominated by ...
What is the porosity of both rooms?
The answer is that the porosity of both rooms would be exactly the same because the uniformly sized spheres in a cubic arrangement produce the same volume of voids in both rooms. The porosity of both rooms would be 48%.
Why do clays have high porosities?
However, clay deposits often have high porosities because their microscopic mineral platelets are negativity charged, pushing the platelets apart and allowing water molecules to occupy the space between the grains. The small, uniformly sized, elongated particle shapes, coupled with their charged nature, results in a large volume of open space even though the spaces are small. As a consequence, porosities of clays can range from 40% to over 70% (Figure 10; Table 1 and Table 2 ).
What is the porosity of a cubic packing?
A cubic packing is the loosest possible arrangement and rhombohedral packing is the tightest possible arrangement. Therefore, the minimum and maximum porosity for a material made of uniformly sized spheres is 26% and 48%, respectively. When grains making up an earth material have an internal porosity, the material is said to have dual porosity ...
What is the primary porosity of Earth?
Primary Porosity. The porosity of an earth material during its original formation is referred to as primary porosity . A number of factors influence the porosity of earth materials. The primary porosity of granular material is affected by the shape and packing of grains, the distribution of grain sizes (sorting and uniformity) ...
How does porosity affect the void space?
Just as secondary porosity enhances the overall void space in earth materials, the porosity of both unconsolidated and consolidated materials decreases with time as younger sediments are deposited on top of older layers, burying and compressing them. The weight of the overlying material compresses the older layers to varying degrees depending on the nature of the material and the initial arrangement of the sediment grains. Generally, porosity is less in formations with greater burial depths (Figure 12), but the variable character of material with similar names (e.g., silt, clay) and the differences in the weight of the overlying sediments makes it nearly impossible to predict the value of porosity given the type of material and depth of burial as indicated by the large scatter on the graphs of Figure 12.
What is primary porosity?
Primary porosity is porosity associated with the original depositional texture of the sediment. That is, primary porosity is the pore space in between the detrital grains and within the depositional matrix. This type of primary porosity is referred to as primary intergranular porosity.
Which rocks have more secondary porosity?
In siliciclastic rocks, primary porosity makes up a larger proportion of the total rock porosity than does secondary porosity. In contrast, some carbonate rocks have more secondary porosity than primary porosity.
What is the percentage of void space in a rock?
Porosity is the percentage of void space in a rock. It is defined as the ratio of the volume of the voids or pore space divided by the total volume. It is written as either a decimal fraction between 0 and 1 or as a percentage. For most rocks, porosity varies from less than 1% to 40%. Primary porosity is the amount of empty space caused by the creation of the rock itself. Secondary porosity is the amount of space created after the rock was formed, such as a crack in the rock.
What is the permeability of siliciclastic rocks?
Permeability in siliciclastic rocks commonly varies more strongly with primary intergranular porosity than with secondary intragranular porosity. Secondary pores are commonly “dead-end” pores (and do not contribute much to fluid flow).
What is secondary intragranular porosity?
Secondary intragranular porosity (leaching of grains) is the most easily recognizable (and quantifiable) secondary porosity. Secondary intergranular porosity (leaching of cement) is in some cases difficult to recognize and quantify.
What is the porosity of sandstone?
Secondary intragranular (leached-grain) porosity in sandstones ranges from 3–5% of the total rock volume. This upper limit may reflect the capacity (or limit) of the fluids to dissolve the mineral matter.
What is the porosity of a rock?
For most rocks, porosity varies from less than 1% to 40%. Primary porosity is the amount of empty space caused by the creation of the rock itself. Secondary porosity is the amount of space created after the rock was formed, such as a crack in the rock. 5.1K views. ·.
What is the difference between primary and secondary porosity?
There are three other ways to classify porosity. Primary porosity is the amount of empty space caused by the creation of the rock itself. Secondary porosity is the amount of space created after the rock was formed, such as a crack in the rock.
What is the porosity of a rock?
The porosity of a rock depends on many factors with the most prominent one being how well sorted the particles of the rock are. If a rock is made up of only one size of particles, it is called well-sorted . However, if the rock has a bunch of differently sized particles, it is poorly-sorted. A poorly sorted rock has a lower porosity than a well-sorted rock. This is because the smaller particles will fall into the empty spaces filling them up.
Why is a rock poorly sorted?
A poorly sorted rock has a lower porosity than a well-sorted rock. This is because the smaller particles will fall into the empty spaces filling them up. For example, think about a jar full of giant jawbreakers.
How much porosity does a rock have?
The rock has 3.2% porosity. Now that we know how to use the basic equation for porosity, let's expand on it. As you can image, it is hard to determine how much empty space is inside a rock. However, if we know the total volume and the volume of the solid, we can figure out the volume of the void.
What is the ratio of voids to total volume?
Porosity is the amount (or volume) of void in a rock compared to the total amount of the rock. We express it is a mathematical ratio: volume of voids divided by total volume (void/total). Usually this ratio is multiplied by 100% so that we can speak and compare in percentages instead of decimals, as shown in this equation:
