Electrical Petrophysics lecture
-
Upload
freebookie88 -
Category
Documents
-
view
248 -
download
1
Transcript of Electrical Petrophysics lecture
-
8/18/2019 Electrical Petrophysics lecture
1/40
Electrical Petrophysics
PETE 3036
Well Logging
Fall 2015
-
8/18/2019 Electrical Petrophysics lecture
2/40
Objectives1. To understand and quantify the phenomenon of electrical
conduction in porous and permeable rocks,
2. To understand the influence of (a) porosity, (b) connate water
salinity and temperature, (c) grain sorting and cementation, (d)
partial hydrocarbon saturation, (e) wettability, and (f) clay
concentration, on the effective electrical resistivity of rocks,3. To introduce the concepts of formation factor and electrical
resistivity index,
4. To understand the petrophysical limitations of Archie’s
equations,
5. To introduce methods to calculate the electrical resistivity of
connate water, and
6. To perform basic exercises on the calculation of hydrocarbon
saturation.
-
8/18/2019 Electrical Petrophysics lecture
3/40
Reading Material
Chapter 6 and Chapter 11, Openhole logAnalysis and formation evaluation, byBateman
Chapter 1, Electrical Resistivity of Rocks, pp 1-24 of the book Theory, Measurement, and
Interpretation of Well Logs by Z. Bassiouni,Z.,1994, SPE Textbook Series Vol. 4,Richardson, Texas.
-
8/18/2019 Electrical Petrophysics lecture
4/40
How is the ELECTRICAL RESISTIVITY of this
rock related to porosity and hydrocarbon
saturation?
EXAMPLE: Fontainebleu Sandstone
-
8/18/2019 Electrical Petrophysics lecture
5/40
How is the ELECTRICAL RESISTIVITY of this
rock related to porosity and hydrocarbon
saturation?
Large quartz grains
showing quartz-filled
fractures and
porosity filling quartz
(SEM-CL image).
-
8/18/2019 Electrical Petrophysics lecture
6/40
-
8/18/2019 Electrical Petrophysics lecture
7/40
-
8/18/2019 Electrical Petrophysics lecture
8/40
-
8/18/2019 Electrical Petrophysics lecture
9/40
-
8/18/2019 Electrical Petrophysics lecture
10/40
ELECTRICAL CONDUCTIVITY AND RESISTIVITY
-
8/18/2019 Electrical Petrophysics lecture
11/40
ELECTRICAL RESISTIVITY OF ROCK
CONSTITUENTS
-
8/18/2019 Electrical Petrophysics lecture
12/40
-
8/18/2019 Electrical Petrophysics lecture
13/40
Electrical Resistivity of Non-NaCl
-
8/18/2019 Electrical Petrophysics lecture
14/40
-
8/18/2019 Electrical Petrophysics lecture
15/40
-
8/18/2019 Electrical Petrophysics lecture
16/40
-
8/18/2019 Electrical Petrophysics lecture
17/40
-
8/18/2019 Electrical Petrophysics lecture
18/40
-
8/18/2019 Electrical Petrophysics lecture
19/40
-
8/18/2019 Electrical Petrophysics lecture
20/40
-
8/18/2019 Electrical Petrophysics lecture
21/40
-
8/18/2019 Electrical Petrophysics lecture
22/40
ELECTRICAL RESISTIVITY OF ROCKS:
MAIN TENDENCIES
-
8/18/2019 Electrical Petrophysics lecture
23/40
-
8/18/2019 Electrical Petrophysics lecture
24/40
-
8/18/2019 Electrical Petrophysics lecture
25/40
Comparison of R w and R o
Let’s consider a cylinder of water with the samevolume as the water volume in the core.
Vp = A L = Ae Le
Ae = A L / Le
rw = Rw Le / Ae = Rw Le2 / ( A L )
To make a comparison, let’s set rw equal to ro.
(In other words, the combination of Le and Aefor the cylinder of water that yields the same
electrical resistance as the water filled core.
-
8/18/2019 Electrical Petrophysics lecture
26/40
ro = Ro L / A
Recall for the core:
rw = Rw Le2 / ( A L )
And for the water:
R o
= F R w
Comparison of R w and R o (cont.)
Let’s define:
12
L
L R R e
W O
)/(/ 2
L A L R A L ReW O
1
2
L
L F e
-
8/18/2019 Electrical Petrophysics lecture
27/40
R o = F R w
F is know as the formation resistivity factor:
Comparison of R w and R o (cont.)
Let: Le / L = (Known as tortuosity)
1
2
L
L F e
2 F
-
8/18/2019 Electrical Petrophysics lecture
28/40
ARCHIE’S “Clean Sand” Equation
-
8/18/2019 Electrical Petrophysics lecture
29/40
-
8/18/2019 Electrical Petrophysics lecture
30/40
-
8/18/2019 Electrical Petrophysics lecture
31/40
-
8/18/2019 Electrical Petrophysics lecture
32/40
Generalized Formation Resistivity
Relationships• Sandstones
– Humble: F = 0.62 -2.15
–
Simplified Humble: F = 0.81 -2
– Phillips’: F = 1.45 -1.54
– Chevron: F = 1.13 -1.73
• Carbonates
– Caruthers (1968): F = -2
– Shell: F = -1.87+0.019/
Most commonly used
-
8/18/2019 Electrical Petrophysics lecture
33/40
-
8/18/2019 Electrical Petrophysics lecture
34/40
-
8/18/2019 Electrical Petrophysics lecture
35/40
-
8/18/2019 Electrical Petrophysics lecture
36/40
-
8/18/2019 Electrical Petrophysics lecture
37/40
-
8/18/2019 Electrical Petrophysics lecture
38/40
“m” and “n”
• m = cementation exponentvaries with pore geometrysandstones -1.1 to 2.5carbonates -2.9 or higher
• n = saturation exponentreflects path of electric current through porenetwork that is partially full of brineaffected by wettability, clays, residualhydrocarbonsArchie’s equation assumes n = 2, ranges from
1 to 2.5
-
8/18/2019 Electrical Petrophysics lecture
39/40
Homework
• Problems 1.14, 1.15 and 1.16 from textbook
• Please find resistivity of a fracing water-based
fluid with the following information at 270F
Sulfates, ppm 200
Chlorides, ppm 100
Calcium, ppm 0.01
Bicarbs, ppm 97.60
Magnesium, ppm 14.39
-
8/18/2019 Electrical Petrophysics lecture
40/40
Review Questions1. Using simple physics arguments, explain why the electrical resistivity of a
rock is related to porosity.
2. Is the electrical resistivity of a rock controlled by its solid or fluid component,
or by both?
3. List four independent petrophysical/measurement conditions that will cause
Archie’s first law to
breakdown?4. The porosity variable used in Archie’s equations, is it total or effective
porosity?
5. Why is it often said that Archie’s second law is not scientifically sound?
6. Why is the electrical conductivity of clays in contact with water relatively
high?7. When does presence of clay/shale in a rock will cause Archie’s first law to
breakdown?
8. Explain why the wettability of a rock could have a sizable influence on the
rock’s electrical conductivity.