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Porosity and types

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Presentation on porosity

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Porosity and types

  1. 1. Presentation Topic: Porosity Presented to: Sir Toufeeq Ahmed Presented by: Samiullah Roll Number: 5208 Section: A Department: Geology University Of Haripur
  2. 2. Contents 1) Porosity defination 2) Factors effecting porosity 3) Types of porosity 4) Determination of porosity
  3. 3. Defination: The ratio of the pore volume in a rock to the bulk volume of that rock.  Denoted by φ.  Express in Percent.  Mathematical Form: φ = Vp/Vb
  4. 4. Porosity Diagram Sand Grains Cement Void space or pores
  5. 5. Factors effecting porosity 1) Particle sphericity and angularity 2) Packing 3) Sorting (variable grain sizes) 4) Cementing materials 5) Overburden stress (compaction)
  6. 6. Types of porosity There are two types of porosity 1) Primary porosity 2) Secondry porosity 1) Primary porosity The porosity of the rock that formed at the time of its deposition. 2) Secondry porosity Develops after deposition of the rock. For example: Fracture spaces formed in fractured reservoirs
  7. 7. Further types of porosity They are further subdivided into 1) Total porosity 2) Effective porosity 3) Microporosity 4) Mesoporosity 5) Macroporosity 1) Total Porosity The ratio of the entire pore space in a rock to its bulk volume. 2) Effective Porosity The measure of the void space that is filled by recoverable oil and gas φ = Vol. of interconnected pores + Vol. of deadend Total or bulk vol. of reservoir rock In very pure sandstone Total porosity is equal to Effective porosity
  8. 8. 3) Microporosity In solids , the term 'microporosity' refers to pores smaller than 2 nm in diameter. 4) Mesoporosity In solids , the term 'mesoporosity' refers to pores greater than 2 nm and less than 50 nm in diameter. 5) Macroporosity In solids , the term 'macroporosity' refers to pores greater than 50 nm in diameter.
  9. 9. Determination of Porosity 1) Direct method 2) Water evaporation method 1) Direct methods Determining the bulk volume of the porous sample, and then determining the volume of the skeletal material with no pores . pore volume = total volume − material volume. 2)Water evaporation method pore volume = weight of saturated sample − weight of dried sample)/density of water