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Bài giảng Reservoir Engineering - Chapter 2: Reservoir rock properties - Trần Nguyễn Thiện Tâm

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Vietnam National University - Ho Chi Minh City  
University of Technology  
Faculty of Geology & Petroleum Engineering  
Department of Drilling - Production Engineering  
Course  
Reservoir Engineering  
Trần Nguyễn Thiện Tâm  
Email: [email protected]  
12/11/2017  
Reservoir Engineering  
1
References  
Holditch Resevoir Engineering (Schlumberger)  
Reservoir Engineering  
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2
Chapter 2  
Reservoir rock  
properties  
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3
Contents  
Reservoir  
Porosity  
Permeability  
Saturation  
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4
Reservoir  
A subsurface body of rock having sufficient porosity and  
permeability to store and transmit fluids.  
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Porosity  
The fraction of total volume that is available for the storage of  
fluids.  
Vp  
Porosity      
Vb  
Vb Vma  
Vb  
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Porosity  
Rock matrix  
Reservoir Engineering  
Pore space  
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Pore-Space Classification  
Total porosity, ϕt  
Total Pore Space  
t   
Bulk Volume  
Effective porosity, ϕe  
Interconnected Pore Space  
e   
Bulk Volume  
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Comparison of Total and Effective Porosities  
. Very clean sandstones: ϕt = ϕe  
. Poorly to moderately well -cemented intergranular materials:  
ϕt ≈ ϕe  
. Highly cemented materials and most carbonates: ϕe < ϕt  
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Permeability  
Permeability is a property of the porous medium and is a  
measure of the capacity of the medium to transmit fluids.  
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Absolute Permeability  
When the medium is completely saturated with one fluid, then the  
permeability measurement is often referred to as specific or  
absolute permeability.  
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11  
Effective Permeability  
When the rock pore spaces contain more than one fluid, then the  
permeability to a particular fluid is called the effective  
permeability.  
Effective permeability is a measure of the fluid conductance  
capacity of a porous medium to a particular fluid when the  
medium is saturated with more than one fluid.  
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Relative Permeability  
Relative permeability is defined as the ratio of the effective  
permeability to a fluid at a given saturation to the effective  
permeability to that fluid at 100% saturation.  
Oil:  
keo  
kro   
k
Water:  
kew  
krw   
k
Gas:  
keg  
krg   
k
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13  
In-Situ Saturation  
Rock matrix  
12/11/2017  
Water  
Oil and/or gas  
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14  
Fluid Saturation  
Saturation is defined as that fraction, or percent, of the pore  
volume occupied by a particular fluid (oil, gas, or water).  
total volume of the fluid  
fluid saturation   
pore volume  
Applying the above mathematical concept of saturation to each  
reservoir fluid gives  
volume of gas  
volume of oil  
Sg   
So   
pore volume  
pore volume  
volume of water  
pore volume  
Sw   
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Fluid Saturation  
The saturation of each individual phase ranges between zero to  
100%. By definition, the sum of the saturations is 100%,  
therefore  
Sg + So + Sw = 1.0  
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Example  
A core, 2.75 cm long and 2.75 cm in diameter has a porosity of  
25%. It is saturated with oil and water, where the oil content is  
1.8 cm3.  
a) What is the pore volume of the core?  
b) What are the oil and water saturations of the core?  
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Average porosity  
Arithmetic average ϕ = Σϕi/n  
Thickness-weighted average ϕ = Σϕihi/Σhi  
Areal-weighted average ϕ = ΣϕiAi/ΣAi  
Volumetric-weighted average ϕ = ΣϕiAihi/ΣAihi  
where n = total number of core samples  
hi = thickness of core sample i or reservoir area i  
ϕi = porosity of core sample i or reservoir area i  
Ai = reservoir area i  
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Example  
Calculate the arithmetic average and thickness-weighted average  
from the following measurements:  
Sample  
Thickness, ft  
Porosity, %  
1
2
3
4
5
6
1.0  
1.5  
1.0  
2.0  
2.1  
1.1  
10  
12  
11  
13  
14  
10  
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Average permeability  
Average Permeability (Parallel Flow):  
n
k h  
i1  
n
i i  
kavg  
h
i
i1  
Average Permeability (Series Flow):  
n
L
i
i1  
n
kavg  
Lk  
i
i1  
i
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20  
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