This document discusses petro-physical properties of reservoirs, including definitions of key concepts like fluid saturation, irreducible saturation, critical saturation, and residual saturation. It explains that saturation is defined as the percentage of pore volume occupied by a fluid (oil, gas, or water). It also provides an example of calculating average oil and water saturation for an under-saturated oil reservoir using porosity and oil saturation data from multiple samples. The document concludes by listing references for further reading on petroleum reservoir engineering topics.

1. Petro-Physical
Properties of Reservoir

2. • Definition
• Changes in fluid saturation during a life of a
reservoir
• Numerical approach
• References

3. Fluid Saturation
• Saturation is defined as the percent, or
fraction , of the pore volume occupied by a
particular fluid (Oil, Gas or Water).
– Eg: oil saturation is 70% it implies that pore space
of reservoir is occupied by oil about 70% .
• Applying above equation to each reservoir
fluid

4. Change in Fluid Saturation during
Reservoir Life Cycle
• Irreducible Saturation: a saturation level below
which the fluid will not flow through microscope
pores and channels in the porous medium
• Critical Saturation: the minimum threshold value
of saturation above which oil or gas begins to
flow towards the wellbore
• Movable Saturation: the max volume of oil or gas
that can be moved or produced from a reservoir
• Residual Saturation: left over saturation of fluid
after primary recovery

6. Average Saturation
• The average value of initial fluid saturation in
the reservoir
• Average saturation of each reservoir fluid is
• The saturation of each individual phase ranges
between 0%-100%
Sg + So + Sw =1

7. Where it is use?
• Original Oil in place
• Total compressibility

8. Numerical approach
• For a given under-saturated oil reservoir,
calculate a average oil and water saturation.
The following data are given:
Sample hi,ft Porosity (%) Oil Saturation
(%)
1 1 12 80
2 1.4 15 77
3 1.5 11 76
4 2.5 10 75
5 3.6 12 70

9. Solution

10. References
• Petrogate Academy Dehradun
• Tarek Ahmed Petroleum Reservoir Engineering
• Tarek Ahmed Advanced Petroleum Reservoir
Engineering
• John Lee, Oil and Gas well testing
• Amanath Chowdary, Oil and Gas well Testing

11. Thank You