Wettability and Rock Diagenesis: Why Microbes are Important€¦ · Wettability and Rock...
Transcript of Wettability and Rock Diagenesis: Why Microbes are Important€¦ · Wettability and Rock...
Imagine the result
Wettability and Rock Diagenesis: Why Microbes are Important
David B. Vance
ARCADIS US, Inc.
Presented at the 20th Annual CO2 Flooding Conference
December 11-12, 2014
Midland, Texas
Imagine the result
Imagine the result
Why Oil is in ROZs
• The upstream community has recognized that petroleum in place is biodegraded by anaerobic microbial processes such as sulfate reduction
• Then the question becomes, given geologic time frames, why is there any oil in ROZs
Imagine the result
The Reason there is Oil in ROZs
• There are two dynamic processes that preserve oil in an ROZ
• One is Microbial Self Limitation – Microbial biodegradation daughter products
stop degradation process • The second is the creation of an oil wet
system – Oil is physically retained on mineral surfaces
making it resistant to physical hydraulic flushing
Imagine the result
ROZ Oil Chemistry Biodegradation
Microbial Processes Biodegradation Process
Controls
Active Microbes In Situ ROZ Properties
• Specific degradation pathways can be associated with single or multiple organisms with gene coding that can be turned on/off in response to conditions
• Often degradation sequences require consortia of multiple microbes in cooperating communities
• Hydrocarbon structure has an effect • Biosurfactant production effects
interfacial properties • Degradation by-products like H2S can be
inhibitory to microbes
• Availability of electron acceptors in order of importance: Sulfate; Iron; Bicarbonate; Nitrate; Oxygen
• Salinity/Temperature/Pressure • Porosity/Permeability/Surface Area and
modification by microbial activity • Hydraulic heads and flow rates • Chemistry of the mineral matrix • Water/Petroleum/Gas interfacial forces • Chemical, physical properties and
structure of the petroleum
Microbial Processing of Petroleum with Positive and Negative Feedback Loops
Imagine the result
Modified Activity Diagram – Calcium, Anhydrite, Sulfur
0
1
2
3
4
5
6
0.1 1 10 100 1000
Log
aCa2
+/a2
H+
Hydrogen Sulfide (aq) mg/L
Calcite
Elemental Sulfur Anhydrite
After: Richard et al, 2005, Oil & Gas Sci. and Tech., Vol. 60, No. 2, pp. 275-285
Imagine the result
Microbial Self Limitation
Imagine the result
BTEX Degradation Median Half Lives in
Days
8
Ben
zene
Tolu
ene
Eth
ylB
enze
ne
Xyl
ene
1
10
100
1000
Anaerobic Biodegradation of Organic Chemicals in Groundwater:
A Summary of Field and Laboratory Studies
Prepared by:
Dallas Aronson, Philip H. Howard
Environmental Science Center, Syracuse Research Corporation
Imagine the result
Microbial Self Limitation (MSL)
• With Almost Universal Microbial Activity Associated with ROZs, Transition Zones, and Even Main Pay Zones – Why Does Petroleum Remain in Place over Millions of Years
• The Answer is Microbial Self Limitation (MSL)
Imagine the result
Microbial Self Limitation (MSL) (2) • Dominant in Sour Oil Systems is the Effect of
Hydrogen Sulfide from Sulfate Reduction • In Sweet Oil Systems Inhibition of Methanogenesis is
More Important • The Presence of Iron (Particular in Clastic Systems)
may Limit MSL Effects • Irrespective MSL Governs Residual Oil
Concentrations and the Geometry of ROZs and Transition Zones
• That knowledge may be used as an Assessment and Exploration tool
Imagine the result
Concentration of H2S that Induce Microbial Inhibition
0
200
400
600
800
1000
1200
mg/
L H
ydro
gen
Sulfi
de
Imagine the result
Microbial Self Limitation (MSL) – Consequences
• MSL Governs Residual Oil Concentrations and the Geometry of ROZs and Transition Zones
• MSL Effects Apply to Sour and Sweet Oil Systems, Carbonate and Clastic Geologic Systems
• At this Point it is Dominantly Applicable to Shallow Petroleum Systems that have Temperatures Suitable for Microbial Activity
Imagine the result
Microbial Self Limitation (MSL) – Consequences (2)
• Knowing that MSL is Taking Place can be used as an Assessment and Exploration tool Allowing for Fact Based Economic Decision Making Regarding Targeted ROZs
• The Suite of Available Analytical Tools Includes (but is not limited to): the Physical Chemistry of the Multiphase Oil/Water/Gas System; Specifics of Microbial Populations (using genetic probes for example); Digenetic Processes; Interfacial Chemistry; Physical Hydrodynamics; Geophysical Properties; and ETC
Imagine the result
Phase Distribution of H2S - mg/Kg
0.1
1
10
100
1000
Water Oil Water Oil Gas
Imagine the result
H2S – Phase Distribution Initial Rules of Thumb
• The mass loading of H2S in the petroleum phase will be 3 times higher than the concentration of H2S in water in contact with that petroleum
• The mass loading of H2S in any confined gas phase can be 100 times the concentration of H2S in the petroleum
Imagine the result
Microbial Diagenesis
Imagine the result
Porosity Curve
“Bow” Shaped Character of Porosity Curve Porosity and PhotoElectric Cross section Log A characteristic “bow” shape on logs is generally present in the ROZs with decreasing resistivity and increasing porosity below the oil/water contacts
Imagine the result
Biogeochemical Diagenesis • Sulfate Reduction using Anhydrite of
Gypsum in the Mineral Matrix Produces an Increase in Porosity by Dolomitization – This induces surface effects as well
• In Clastic Systems the Reduction of
Ferric Iron Oxides to Produce Soluble Ferrous Iron can Increase Porosity in General as well as Preferentially Enlarge Pore Throats
Imagine the result
Biogeochemical Diagenesis (2) • Biogenic Mineral Products such as
Dolomite are Often Generated as Nano-Scale Crystallites – that Impacts other Physical/Chemical Process by Influencing Interfacial Chemistry and Chemical Reaction Rates
• That in Turn Induces Oil Wet Conditions – An oil wet system is resistant to physical
hydraulic sweeping over geologic time frames
Imagine the result
Dolomitization in ROZs – Biogeochemical Effects
• Sulfate Reduction Converts Gypsum to Limestone and Then Dolomite
• The Cell Walls of Active Microbes and Extracellular Polysaccharides Have Points of Negative Charge and Scavenge Magnesium for the Water Environment to meet Metabolic Needs
Imagine the result
Changes in Molar Volume
0
10
20
30
40
50
60
70
80
Gypsum Anhydrite Calcite Dolomite
Normalized Molar Volume cm3/Mole
Imagine the result
Diagenesis in Clastics • With iron oxide cements: • Conversion to ferrous iron
increases porosity and opens pore throats
• It may free fines • It may generate colloidal
ferric iron oxides
Imagine the result
Wettability
Imagine the result
Calcite 9.5
pH Point of Mineral Surface Zero Charge Sulfur
2.3 Fe Oxide 8.5
Quartz 2.0
Clays 2.5
Feldspars 2.0
Dolomite 8.0
Gypsum 10.3
14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
pH
Incr
easi
ng a
cidi
ty
+ + -
- -
+
Red = Positive Charge on Mineral Surface; Blue = Negative Charge
+ +
+
+
+ - -
-
-
-
Imagine the result
Anaerobic Benzene Degradation Detailed Pathway with Examples of Carboxyl Groups on Intermediate's
Microbial Biotechnology Volume 4, Issue 6, pages 710-724, 30 MAR 2011 DOI: 10.1111/j.1751-7915.2011.00260.x http://onlinelibrary.wiley.com/doi/10.1111/j.1751-7915.2011.00260.x/full#f2
Imagine the result
Surface Area vs. Crystal Size
0
500
1000
1500
2000
2500
1.00E-091.00E-081.00E-071.00E-061.00E-051.00E-041.00E-03
Surf
ace
Area
Met
ers p
er G
ram
Crystal Diameter Meters Millimeter Micron Nano Meter
Imagine the result
Nano Scale Effects
• Surface area per unit mass increases • The number of crystal planes, edges, and
defects increase • Those features enhance the potential for
surface attachment • The process creates roughness and nano
to micro channels which increases capillarity forces
Imagine the result
After Brown 2001 Science Vol. 294 pp. 67-70
Water Wet Mineral Surface
Imagine the result
There are Complex Interfacial Forces at Work
• Smaller and lighter molecules at any given temperature have a higher velocity than larger molecules or agglomeration of molecules
• Petroleum biodegradation generates small soluble charged and polar molecules
• Higher physical kinetic velocities contribute to migration to a mineral surface
Imagine the result
Becoming Oil Wet
Carbonate Mineral With Positive Surface
Charge
+ +
+ +
+
+
+
Petroleum
Petroleum
Petroleum
Petroleum
Imagine the result
Becoming Oil Wet Biodegradation & Biogenic
Products
Carbonate Mineral With Positive Surface
Charge
+ +
+ +
+
+
+
Biodegraded Petroleum
Biodegraded Petroleum
Biodegraded Petroleum
Small Soluble Alcohols, Ketones and Carboxylic Acids – Polar and Charged
Imagine the result
Petroleum
Becoming Oil Wet Attachment of Small Soluble Charged and Polar Species – Degradation and Biogenic
Carbonate Mineral With Positive Surface
Charge
+ +
+ +
+
+
+ Biodegraded Petroleum
Biodegraded Petroleum
+ -
Surface Conditioning
Film
Imagine the result
Petroleum
Becoming Oil Wet Co-Adsorption and Agglomeration on Non-
Polar Liquid Hydrocarbon
Carbonate Mineral With Positive Surface
Charge
+ +
+ +
+
+
+ Biodegraded Petroleum
Biodegraded Petroleum
+ -
Imagine the result
( o r g a n i c )
S t a g n a n t f l u i d
M o b i l e f l u i d
S o i l o r r o c k m a t r i x
Carbonate
Wettability - Adhesion and Cohesion
Adhesion Cohesion
Imagine the result
Summary The Role of Microbial Biogeochemistry
– Enhanced porosity driven by biogenic changes in carbonate mineral suites
– Chemical composition of the petroleum • Hydrocarbons are consumed and graded by sulfate
reducing microbes • That process generates hydrogen sulfide that
inhibits microbial activity at concentrations over 100 to 200 mg/L – That prevents total hydrocarbon consumption
– The production of small soluble charged and polar species by biodegradation initiates the oil wet process • Charged/Polar species attach • Non-polar and liquid petroleum then adsorb and
agglomerate
Imagine the result