This document discusses reservoir fluid geodynamics (RFG), which involves the redistribution of fluids and tar formation after an oil and gas charge into a reservoir. It provides several examples of how RFG processes like diffusion, convection, and phase changes can lead to different fluid property gradients and production profiles in different areas of the same reservoir or across fault blocks. Downhole fluid analysis and comprehensive geochemistry, combined with thermodynamic modeling of asphaltenes, can be used to evaluate reservoirs, understand connectivity, and explain issues like the formation of viscous tar deposits. RFG is a new approach that provides insight beyond traditional reservoir evaluations.

1. 11
Oliver C. Mullins, Schlumberger
and One Zillion Collaborators
Reservoir Evaluation &
Reservoir Fluid Geodynamics (RFG)
1) RFG: DFA and Thermodynamics
2) Connectivity and Equilibrated Asphaltenes
3) Disequilibrium and RFG Processes
4) Tar Formation
5) GCxGC & Geochemistry
OUTLINE

2. Basin modeling gives fluid
type, timing, volumes
INTO reservoir
Geologic Time Line
Almost No Modeling
of in-Reservoir
Fluid Geodynamics
No
Modeling
Modeling of
Production in Eclipse
Production Time Line
Missing Component of Reservoir Understanding and Modeling
Reservoir Fluid Geodynamics

3. Petroleum System
FILLS Reservoir
Reservoir Fluid Geodynamics
Redistributes Fluids & Tar Formation
Simulation
Produces Reservoir
Reservoir Fluid Geodynamics
Redistributes Fluids and Yields Tar Formation After Charge
Time Line
Geologic Past Present Day

4. Asphaltene Nanoscience
Asphaltene Thermodynamics
Diffusion
Fluid Mechanics
Reservoir Fluid Geodynamics Requirements:
Comprehensive
Science
DFA Data
of Reservoir
Reservoir Evaluation
Case Studies
Vertical, Lateral
Fluid
in Fields
Reservoir
Fluid Geodynamics
Fault block migration,
Formation overturn,
Gas charge into oil,
Tar mat formation,
Viscosity gradients,
Biodegradation & diffusion

5. F = mg. Newton’s 2nd Law
Peng-Robinson EoS 1976
HC
Liquids
Gas-Liquid Fluid- (dissolved) Solid
Flory-Huggins-Zuo EoS 2010
Yen-Mullins Model 2010
Gas
Cubic EoS Gas-Liquid
Crude Oil Thermodynamics; Asphaltenes Now Included.
No Predictions Without Asphaltenes of Heavy Oil, Tar, Viscosity…
Asphaltenes:
Van Der Waals EoS 1873

6. First High Resolution Images of Asphaltene Molecules
Agree with Yen-Mullins Model
IBM Zurich IBM Zurich, Schlumberger… Published in J. Amer. Chem. Soc.
Nobel Prize
for STM
STM Expt.
AFM Expt. AFM Expt.Atoms and Bonds
MO TheoryElectron Orbital

7. 7
2nd Optical
Analyzer
1st Optical
Analyzer
Pump
Sample
Bottles
Probes
Probe
(extended)
7
Downhole Fluid
Analysis (DFA)
Measure
Oil Color

8. Reservoir Fluid
Geodynamics
Petroleum System
Context
Gas Charge into Oil
Diffusion GOR Gradient
Different Reservoir
Realizations
Diffusion
& Convection
Fault Throw
Biodegradation
& Diffusion
Not Equilibrated
Gas Charge into Flank
Heavy Oil & Tar Mat
Connectivity
“Gas Flood” Local GOR Increase but
Connected
Compartments
Reservoir Baffling;
Low Production
Regional Viscosity
Gradients
Spill-Fill with
Biodegradation
Big Viscosity Trends
Tar in Natural
Fractions
No Production
in Flank
Gas Sweep & Tar GOR Gradient, Mobile Tar
Geologic Time
Diffusion/Mixing Connectivity

9. Equilibrated Asphaltenes (FHZ EoS)  Connected Reservoirs
Proven in Production in all Fluid Types
Volatile OilCondensate
9

10. Heavy Oil:100 kilometer length, 60 Meter  10x Gradient.
Matches FHZ with Yen-Mullins. No Adjustable Parameters Convective
Currents
Tar
No Adjustable
Parameters
Asphaltene Equilibration  Reservoir Connected
Proven in Production

11. Tar
Giant Asphaltene Gradient NOT a Maturity Gradient !
From Convective Currents of Asphaltene-Enriched Oil.

12. 12
CH4
CH4
CH4
CH4
High
GOR
Low
Asphltn
Low
GOR
High
Asphtn
Diffusive
Gas Front
0
1
2
3
4
5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
020406080100
Height(meters)
Cluster
Gradient
0
GOR scf/bbl
2k 4k 6k 8k
4k 6k 8k 10k 12k
Saturation Pressure (psi)
CH4
Connected Reservoir But Not Equilibrated.
Recent Gas Charge Into Oil. Diffusion  Large GOR Gradients.
Asphaltene Expulsion. Convection Large Asphaltene Gradients.
Gravity Current
Pumps Asphaltenes to Base
Diffusion Gives
HUGE GOR
Gradient at Top

13. 3 Adjacent Fault Blocks. Same Petroleum System.
3 Entirely Different Realizations.

14. Asphaltene Content in Liquid Phase
• Well 1:
– large disequilibrium
– high Asphaltene Content
• Well 2 & Well 3:
– oil equilibrated
– low Asphaltene Content
Where did the Asphaltene go?
How and Why?

15. Fault Block 1. GIANT Disequilibrium in 40 Meters !!!
Pleistocene condensate charge into Oil Reservoir
Gas Diffusion and Asphaltene Migration Ongoing
DFA Asphaltenes
Depth(meters)
GOC
OWC

16. 1) 1st Movie of Tar Mat Formation
2) Different Gradients Due to Baffling. Production Differs by 10x.
Well 1. Baffled. NOT Equilibrated
Low DST Production Rate
Well 2. Equilibrated.
High Production.
Asph GOR Core Ex
Equilibrated; Tiny Fluid Gradients
Late Gas
Charge
Into Oil
Reservoir
Initial
Gas
Asphaltene
1 2
OD
120 180
GOR m3
/m3
Asphaltenes GOR
TVD
Not Equilibrated; Huge Gradients
0
OD
Tar
Tiny
Asphtn
FHZEoS
TAR
600
%AsphGOR
200180
SLOW Diffusion FAST Diffusion

17. SEM. Tar Mat. Phase Separated Asphaltene
Trapped
Oil

18. Shale
Baffle
Well 3. Density Stacking / Vertical Charge Above Shale. “Tar Mat”
Asphaltenes Throughout.
Core %Asphaltene
Tar on
Shale
FB/Well #3
Asphaltenes
On Baffle
Methane diffusionAsphaltene
Diffusion
(Slow)
Lateral
Gas
Sweep
H2O
Vertical Gas Sweep
Shale
Lateral Sweep in Trap Filling Below Shale.

19. FB 1. Baffled.
BIG Gradients
Low DST Rate
FB 2. Equilibrated.
Tar Mat
High Production.
Late
Gas
Charge
Into
Oil
Resrvr
SAME
Initial
Point
Gas
Asphaltene
1 2
OD
Asphaltenes
TVD
Not Equilibrated;
Huge Gradients
Asph
Equilibrated;
Tiny Fluid Gradients
0
OD
Tar
Tiny
Asphtn
FHZEoS
Core Ex
TAR
600
%Asph
%Aspht
FB 3. Equilibrated.
Tar on Shale.
Aspht Coating
Near Charge Point.
Lateral ChargeGood SandPoor Sand, Many NF.
RFG: Late Gas into Oil. 3 Very Different Realizations.

20. Primary Sand Connected and Equilibrated Asphaltenes.
Flank Not Equilibrated. Connected?

21. Well B: Mud gas isotope:
dC13
Lateral Sweep. Surge in Gas, GOR Across Field. Connected.
DFA GOR
surge across field
Well B: DFA GOR
GOR
Well A
Well B

22. Reservoir Connected !!!
New ! Not in Literature.

23. 280
300
320
340
360
380
400
420
440
460
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
TVDSS m
OD at ch[5]
Mud filtrate
No n-alkanes
Many n-alkanes
GC Confirms Biodegradation at/near OWC
OBM contamination
IMPACT OF BIODEGRADATION
DFA Color. Asphaltene Content

24. 270
310
350
390
430
470
0.0 0.5 1.0 1.5 2.0
TVDss, m
OD & Asphaltene
Alkanes Consumed at OWC
FHZ w Diffusion
FHZ (2nm)
Diffusion Has not yet reached this high
Biodegradation and Diffusion.
Severe Biodegradation TRIPLED Asphaltene Content PM 06
3x
Oil Volume
Alkane
Consumption
via Biodegradation
Concentrates Asphaltenes
ALKANE
Diffusion

25. DFA Color / Asphaltene Increase is 3X
from Deep to Shallow Reservoir

26. Naphthalene
1-Methyl Naphthalene
2-Methyl Naphthalene
C2-Naphthalenes
C3-Naphthalenes
Hopanes
Resv:1
Thermal Maturity
Contamination
Water Washing
GCxGC
1st Column
2ndColumn

28. Peters-Moldowan = 2
Resv: 1
Resv: 4
Peters-Moldowan = 4
Minimal Water Washing
Moderate Water Washing
Peters-Moldowan = 6
(25-Norhopanes appeared)
Extensive Water Washing
Resv: 6
Naphthalene
Naphthalene
Naphthalene
C2-Naphthalene
C2-Naphthalene
C2-Naphthalene
C4-Naphthalene
C4-Naphthalene
C4-Naphthalene

29. 3X Increase in Asphaltenes:
• PM 2 6
• Water Washing (Assisted by Biodegradation)
• Some Maturity Variation
Asphaltenes

30. Early Oil Tar Stuck in Charge Plane Makes No Sense (to me).
60oC
1st Cold, Solid Bitumen Exits
NanoDarcy! (Sink in Water?)
Then Heats Up !
Reservoir (say 100oC)
Greatly Decreasing Viscosity
Hot Roofing Tar
Drilling Hazard Tar.

31. Then the Hot Tar Gets Stuck in the Grand Canyon
(or giant fault). Can’t Get Out !!
(or JUST maybe there is another explanation)
Reservoir Fluid Geodynamics can provide the answer.

32. Conclusions
Reservoir Fluid Geodynamics (RFG):
Redistribution of Fluids, Tar After Charge.
A New Way to Evaluate Reservoirs
RFG Enabled by Asphaltene Thermodynamics, DFA & Case Studies
Equilibrated Asphaltenes  Reservoir Connectivity.
Disequilibrium  Geodynamic Processes.
Charging, Baffling, Diffusion, Convection, Phase change /Tar etc.
Chemical Composition; GCxGC with Geochemistry
Compare with Thermodynamics.
Drilling Hazard Tar Needs a New Look.
Universal DFA Workflows to Address Most Reservoir Concerns.

33. Petroleum System
FILLS Reservoir
Present Day
0 Ma After
Charge
3 Ma After Charge:
Asphaltenes Equilibrated
~12 Ma After Charge:
Biomarkers Equilibrate
Asphaltenes Equilibrate FASTER than Biomarkers
Due to Charge Sequence.
Same as Tornado…?
Diffusion
More
Diffusion
Reservoir
Charge
Liquids
Liquids
Liquids
TVDSS
TVDSS
TVDSS
Gas
Gas
Gas
Geologic Past

34. Density Stacking of Crude Oils.
First Heavy Oils, Then Light Oils.

35. No Tat Mat. Core Extracts Merely Contain Oil.
Fault Block 1.
Giant Disequilibrium in 40 Meters!!.
Late
Gas
Charge
Into
Oil
Reserv
oir
Initial
Gas
Asphaltene
Current
Asphaltene in Oil Asphaltene in Core Extracts

36. Gas Charge
into Oil
Gas Charge into Oil Reservoir & Reservoir Fluid Geodynamics
Diffusion
Convection
Heavy Oil /Tar
Flank Charge
& Seal Failure
Tar Occlusion in
Natural Fractures
DS Report
Independent
Low Production
Drilling Hazard
OTC Paper
Different Production Concerns: Connectivity, PI, Tar Mat, Viscosity…

37. DFA Color / Asphaltenes r
g/cc
GORPressure
Not Equilibrated
Poor Production
Equilibrated
Good Production
Connectivity, Baffling, Compartments;
DFA Gradients and Production

38. Connectivity.
Low GOR Black Oil.
Tahiti Field
38
Pressure:
Two Stacked Sands
Chevron
Uplift
Causes
Faulting

39. DW
0 2 3
x4
x6
x7
TVD
Feet
103
DFA Color  %Asphtn
In Each Main Sand: Equilibrated Asphaltenes: CONNECTED.
Proven Correct in Production.





 

kT
hgV
ODhOD
r
exp)0()(
OilColumn
Dia ~ 2nm
1
FHZ EoS