Quantitative evaluation

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Quantitative evaluation Examine procedures in
which data from 2 or more logs will be used to
evaluate for the amount of hydrocarbon compared
to pore water within a formation The proportion
of pore space occupied by water is known as water
saturation (Sw) e.g. if 65 of the formation is
occupied by water and 35 by hydrocarbons the
water saturation is 0.65 (percent water
saturation is 65) Definition of the formation
factor (F) F Ro/Rw Where Ro is the
resistivity of the total formation (rock matrix
fluids) saturated with water Rw is the
resistivity of the water itself
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• F Formation factor is used to help calculate
  water
• saturation function of porosity
• Definition F Ro/Rw
• Definition for water saturation Sw vRO/RT
• RO RT (for a 100 saturated sand)
• Substituting in the equations and rewriting for
  water
• saturation we have
• RO F. RW
• SW F. RW/RT

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QUANTITATIVE EVALUATION FOR HYDROCARBON
POTENTIAL Archie equation
(1942) F a/fm a constant which is
lithology dependent m empirically derived
constant f porosity (e.g. 30 enter as 0.30)
Actual values for a and m are lithology and
region dependent Some examples F 0.82/f
uncompacted sands F 1/ f2 compacted
formations, chalk F 1/ f2.2 compacted
clastic and oolitic rocks F 0.62/ f2.15
recrystallized carbonates (sucrosic
texture) F 1.13/f1.73 generic value
for large number of samples
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• Analysis for
  Hydrocarbon Potential
• Definition Rwa
  Rt / F
• Rwa apparent water resistivity
• Rt is measured from a deeply focused induction
  log
• F is calculated from the formula using log
  measured porosity
• value
• est Sw () vRw/ Rwax 100
• Rw Rwa of a 100 water saturated formation.
  Measure from
• an obvious water-bearing formation
• Rwa Analysis Rwa/ Rw
• Ratio Rwa lt 2 No oil production

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Hydrocarbon potential
Locations SP mv Resistivity ohm-m Resistivity ohm-m Resistivity ohm-m f F Rwa est Sw Rwa analysis Rwa/Rw Hydrocarbon Production y/n
Locations SP mv sh dp dp in. f F Rwa est Sw Rwa analysis Rwa/Rw Hydrocarbon Production y/n
1
2
3
4
5
Use F 0.83 / f2
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READINGS AND CALCULATIONS
Levels SP mv Resistivity ohm-m Resistivity ohm-m Resistivity ohm-m f F Rwa est Sw Rwa/ Rw Prod. y/n
Levels SP mv sh dp dp in. f F Rwa est Sw Rwa/ Rw Prod. y/n
1 - 62 0.26 0.2 0.20 .30 9 0.02 100 1 N
2 - 45 7.50 6.0 6.70 .06 228 0.03 82 1.5 N
3 - 49 1.50 0.5 0.50 .23 16 0.03 82 1.5 N
4 - 18 1.08 0.8 0.98 .13 49 0.02 100 1 N
5 - 15 0.94 0.8 0.98 .26 12 0.08 50 4 Y