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1. Determination Of Porosity By
Boyle’s Law Porosimeter

2. DEFINITION OF POROSITY
• Porosity(ɸ) : The ratio of the pore volume in a rock to the bulk volume of that
rock express in percent.
Mathematical form is :
ɸ=Vp /Vb

3. POROSITY
• Porosity is a measure of the void space in rock hence , measures how much HC
in rock.
• Porosity ɸ =Vp/Vb=(Vb –Vm)/Vb ; Vb=Vp+Vm
-theoretically, varies from 0% - 47.6%
-in practice , varies between 3% and 37%
• Porosity is a function of particle size distribution :
-framework materials (sandstone)-high ɸ
-interstitial material (shaly-sand)-low ɸ

4. CLASSIFICATION OF POROSITY
Porosity
Pore
connection
• Absolute
• Effective
Origin
• Primary
• Secondary

5. POROSITY

6. FACTORS THAT AFFECT POROSITY
Primary
• Particle sphericity and angularity
• Packing
• Sorting
Secondary ( Diagenetic)
• Cementing materials
• Overburden stress
• Vugs , dissolution and fractures

7. POROSITY
• Determination of Boyle’s porosimeter
• 𝑉𝑔 =
𝑉1 𝑃 𝑓−𝑃1 +𝑉2 𝑃 𝑓−𝑃2
𝑃 𝑓−𝑃1
Where, V1 & V2 are the calibrated
chamber volumes

8. USES OF POROSITY
• Basic use is to calculate volumetrically the quantity of hydrocarbon (HC) in the rock
- N =7758*As*H*ɸ*Soi
- N = HC volume in the reservoir ,res. bbl
- As = surface area ,acres
- H = thickness of formation, ft
- ɸ = porosity , fraction
- Soi = initial oil saturation ( 1.0-Swi), fraction
If N is divided by Bo’ we will get the volume on surface. Since oil shrinks as it comes to the
surface due to gas coming out, (Nsurface ˂ Nreservoir)

9. TRANSFORM OF LAB POROSITY TO
FORMATION POROSITY
• ɸ = ɸ e-CPΔP
• ΔP : effective overburden pressure change
• PC : rock compressibility
• ɸ : lab porosity

10. THANK YOU