By John Pack Greg Pudewell Jaynesh Shah Edwin L. Youmsi Pete

Petroleum-Oriented Nanotechnology  Many nanotechnology applications have become standard in petroleum refining.  Most obvious application for upstream operations is development of better materials

Petroleum-Oriented Nanotechnology  Lighter, stronger and more resistant equipment can be produced using nanotechnology.  It could also be used to develop new metering techniques with tiny sensors to provide improved data about the reservoir

Petroleum-Oriented Nanotechnology  Other emerging applications of Nanotechnology in reservoir engineering include; Development of “smart fluids” for enhanced oil recovery and drilling. Development of “nanofluids” which are used to enhance some of the properties of a fluid.  Nanotechnology in reservoir engineering is however still under- investigated.

What exactly is Nanotechnology?  A lot of confusion fueled partly by science-fiction.  Currently, there is no distinction between “true” nanotechnologies and other domains of atomic and molecular science/engineering.

What exactly is Nanotechnology?  Fairly representative definitions include; “Nanoscience is the study of phenomena and manipulation of material at atomic, molecular and macromolecular scales where properties differ significantly from those at a larger scale.” “Nanotechnologies are the design, characterization, production and application of structures, devices and systems by controlling shape and size at a nanometer scale.”

Colloidal Suspensions and Association Nanocolloids in Petroleum

Importance of Native Colloids for Petroleum Properties  Specialists argue that there is no novelty  Importance was emphasized several decades ago, esp. with bitumen  Any petroleum medium represents a colloid system with a dispersed colloidal phase composed mainly of asphaltenes  Important milestones in the research of asphaltene colloidal characterization: Publications of books based on materials of the 1993 International Symposium on the Characterization of Petroleum Colloids A Russian-language book on disperse systems in petroleum Asphaltene molecule from

Previous Colloid Models  No earlier or more recent models include a concept of asphaltene self-assembly into a variety of nanocolloidal configurations with a well- structured phase diagram  Most models from the start consider asphaltene as a solid (quasispherical) colloidal particle with diameter between 2-10 nm  There are no complex phase diagrams of hard sphere colloids  The “only critical” boundary being not a specific phase transformation, but a precipitation onset

Previous Colloid Models  Only one additional “critical boundary” appears in previous models  Colloidal particles are not permanently present in petroleum but are formed from molecular solutions of asphaltenes at certain critical conditions as a result of some association processes  These association processes were regarded to be similar to micellization phenomena of simple surfactants for a long time hilicSurfactants.jpg

Different Classes of Disperse Systems  The assumption of micellization places asphaltenes into a principally different class of disperse systems  Colloidal suspension A system of solid particles dispersed in a liquid  Association colloids Systems with particles which are formed by reversible micellization Usually exhibit a very rich phase behavior ranging from the simplest isotropic micellar phases to highly organized supramolecular nanostructures

For Example…  Note the appearance of enclosed phase domains (“closed loops”) at the phase diagram, representative of a so- called reentrant phase behavior  “Closed loops” are indicative of polymorphism of a system  Loops originate in liquid- liquid immiscibility phenomena and are characteristic signatures of directional noncovalent bonding in associating species Fig 3. A complex temperature-concentration (T- C) phase diagram for nonionic surfactant penta- ethyleneglycol dodecyl ether (C 12 E 5 ) in water from I. Evdokimov, SPE

Future Research into Association Colloids  Even after introducing the concept of micellization for nanoparticles of asphaltenes, petroleum researchers still remained content with the idea of single critical concentration (CMC) in surfactants  Possible analogies with known complex properties of association colloids has not been investigated  Although well-known published experimental results and recent publications provide multiple data in support of the concept of asphaltenes as “association colloids” es/research/complex/Hill_colloid_charge s.jpg

T-C Phase Diagram of Asphaltenes in Petroleum – Data Accumulation

Asphaltene Phase Diagrams  Phase changes in asphaltene-containing systems can be identified by revealing “specific points” in experimental concentration and temperature dependencies of system’s parameters Fig 4. Concentration and temperature effects on Herschel- Bulkley’s rheological parameters in asphaltene –rich model oil from I. Evdokimov, SPE

“Specific Points”  The T-C area of practical importance is wide: Pour point temperatures Asphaltene decomposition/coking “Infinitely diluted petroleum solutions” Solid Asphaltenes  This research group investigated concentration effects in dilute solutions with asphaltene contents from ~1 mg/L to ~1 g/L, close to room temperature  Detailed studies of temperature effects have been performed in the range from -50°C to ~400°C with bitumen and precipitated asphaltenes (concentrations used were from ~140 g/L to ~1200 g/L)

“Specific Points”  Specific concentrations/temperatures were neither noticed nor discussed in original publications but corresponding “specific points” are clearly seen in the published data plots  E.g., SANS study of asphaltene aggregation Provided detailed concentration dependencies of the radii of gyration RG in solutions of asphaltenes with concentrations mg/L at temperatures from 8°C to 73°C Provided qualitative discussion of concentration/temperature effects Did not specify obvious R G maxima at concentrations ~5, ~20-22 and ~70 g/L Replotting their original data on R G vs. T graph clearly indicate the presence of “specific temperatures” round °C

T-C Phase Diagram of Asphaltenes in Petroleum – Current Version

Current T-C Phase Diagram Asphaltenes in Petroleum  First cumulative T-C plot of all “specific points” Fairly well-defined phase boundaries Limited data does not allow for statistical analysis ○ Numerical values of “critical” parameters should Be regarded as approximate Concentration-Defined Phase Boundaries Temperature-Defined Phase Boundaries Fig. 5 from I. Evdokimov, SPE

Concentration-Defined Phase Boundary  Primary aggregation boundary (Line 1 in diagram) Ca mg/l (20 o C) Obtained by measuring ○ UV/vis absorption ○ Viscosity ○ NMR relaxation Attribution of boundary to primary association of asphaltenes monomers recently Also confirmed by fluorescence technique Fig. 5 from I. Evdokimov, SPE

Concentration-Defined Phase Boundary  Liquid-liquid demixing boundary (line 2 in diagram) Ca mg/l (20 o C) Revealed for solutions of solid asphaltenes and of heavy crudes by: ○ Optical absorption ○ NMR relaxation ○ Viscosity ○ Ultrasonic velocity, etc. Closed loop phase boundary is a well known feature of demixing systems ○ Boundaries 2 and 3 in diagram seem to be part of a closed loop “Upper” and “lower” “critical solution temperatures” present in diagram Fig. 5 from I. Evdokimov, SPE

Concentration-Defined Phase Boundary  “Former CMC” boundaries (lines 3a and 3b in diagram) Most documented one ~ 1-10 g/l Published “CMC” data tend to concentrate at 2 sub-ranges ○ 1-3 g/l and 7-10 g/l Asphaltenes do not exhibit true CMC behavior so CNAC (critical nanoaggregrate concentration) was introduced Diagram shows that “Former CMC” boundaries reflect phase transformations in secondary systems of complex nanocolloids formed at the demixing boundary At least one of the “former CMC” lines may be just a continuation of a demixing (liquid-liquid separation)closed loop Fig. 5 from I. Evdokimov, SPE

Concentration-Defined Phase Boundary Highest-Concentration boundaries (lines 4 and 5 in diagram)  Strong effects observed at g/l and contributed to a “second aggregation concentration ”  Detailed SANS studies “Dilute regime” (from 3 to 4) ○ Aggregates are independent entities with radii of few nanometers “Semi-dilute regime” (above boundary 4) ○ Internal structure of aggregates remains unchanged ○ Aggregates interpenetrate and form soft fractal objects, imparting high fluid viscosities “Concentrated regime” (above boundary 5, above g/l) ○ Large flocculated asphaltene domains may form “spatially-organized two- phase textures” Fig. 5 from I. Evdokimov, SPE

Temperature-Defined Phase Boundaries  Several temperature-controlled phases of aggregated asphaltenes (right-hand side of diagram) Freezing ○ Exhibit heat capacities consistent with an ordered solid α-phase (25-30 °C) ○ Amorphous (glassy) phase ○ Structure controlled by interactions between polar alkane side chains β-phase (30-100°C) ○ Phase transition acquire more dense structures ○ Controlled by bonding to pericondensed aromatic segments γ-phase ( °C) ○ Phase with crystalline order Higher Temperatures ○ Amorphous asphaltenes soften and liquefy ○ Crystalline domains melt at °C ○ Above 350°C asphaltenes decompose and form liquid crystalline mesophase Fig. 5 from I. Evdokimov, SPE

Immediate Relevance to the Properties of Native Petroleum

 Some skeptics wonder why we need these scientific speculations and nice pictures It is true that we cannot make any suggestion about the details of nanocolloid phases in “live” petroleum ○ More complicated and costly experiments are needed Detailed inspection of the world’s “dead” petroleum fluids show surprisingly strong effects which may originate in the phase diagram of asphaltene nanocolloids (fig 5) ○ Highlights some of the previously overlooked features Fig. 5 from I. Evdokimov, SPE

Plot of viscosity vs asphaltene content  Log- log plot for 200 crudes of various geographical/geological origin  Solid line is insignificant, only to emphasize apparent viscosity extreama  Stastics have to be improved, especially in the low asphaltene contents  Even “raw” data in fig 6 clearly demonstrate a coincidence of shaprp viscosity anomalies with all but one phase boundaries (phase 1) Applies to wt% Most current databases classify <0.01 wt% as “zero asphaltene content”  Almost absence of native free-flowing crude oils with asphaltene contents above the phase boundary 5 May be a natural “solubility limit” of asphaltene in native crude oils Fig. 6 from I. Evdokimov, SPE

Well-known interdependence of viscosities and densities in crude oils Noticeable peaking of specific gravities at asphaltene phase boundaries showin in fig 7 Asphalene decomposition table with “Resin and Asphaltene Content of various Crude Oils” (from source) ○ Properties of 20 crudes with non-zero asphaltene content from diverse locations (Canada, Venezuela, Mexico, USA, Russia, Brazil, Iraq, France, Algeria) ○ Plot of specific gravity vs asphaltene content from table shown in fig 8 ○ When compared to figures 6 and 7, one can see the same peaks of specific gravity to the same asphaltene phase boundaries ○ Boundary 3b not seen due to lack of data points Specific Gravity vs Asphaltene Content “ Asphaltene Deposition and Its Control”: ~mansoori/Asphaltene.Decomposition.and.Its.Control_html Fig. 7 from I. Evdokimov, SPE Fig. 8 from I. Evdokimov, SPE

Property Transformations  Fig 9: Properties from boundary A in fig 5  Left Hand Side Variations of the pour point of a Tatarstan crude after 1 hour thermal pre-treatments, Temp close to phase boundary A Properties ○ 895 g/l 3.5 wt% asphaltenes ○ 20 wt% resins0.3 wt% waxes Most Dramatic Pour point Deviation ○ to o C (at pre-treatment Temp of 36.5 o C)  Right Hand Side Dramatic Density Deviation near boundary A in fig 5 Measured by refractive index With no phase boundary, expected gradual decrease with density at top marginally smaller than the bottom Expected behavior below 28 o C and above 37 o C Between 28 and 37 o C (at boundary A) there is a strong transient stratification of density and presumably of composition of the oil Fig. 5 from I. Evdokimov, SPE Fig. 9 from I. Evdokimov, SPE

Deposits at steel surfaces  Study of deposits from petroleum fluids with high asphaltene content (12.3 g/l) on steel surfaces  Fig. 10 Filled in symbols ○ Deposits from fluids which “thermal history” never crossed boundary A Open symbols ○ Deposits from a fluid that was heated at least once above o C ○ Afterwards, Increase of deposition persisted below the phase boundary (at o C) for at least one month Fig. 10 from I. Evdokimov, SPE

Nanophase-Resembling Phenomena in Brine-Petroleum Dispersions

 Oil well output typically consists of water in a crude oil  Water/oil mixtures are not “nanosystems” as are nanocolloids but there are similarities Both have well-defined phase diagrams Water/oil dispersion controlled by oil’s “indigenous surfactants” including nanocolloidal asphaltenes ips.org

Water/Oil Mixtures “Nano- Resemble” Nanoemulsion Systems  Microwave heated from °C  Sharp variations of specific heat due to abrupt changes in morphology Resembles those observed in nanoemulsion systems “Percolation threshold” at water cuts ≈ 0.2 “Bicontinuous morphology” at water cuts ≈ 0.4 “Close packed” at water cuts ≈ 0.6 I. Evdokimov, SPE

Water/Oil Mixture Measurements of Density  Water cuts from indicative of an asphaltene-mediated “middle phase”  T-C contours of excess, non-ideal densities show strong correlation to the bicontinuous domains of the T-C phase diagram for association nanocolloids I. Evdokimov, SPE

Demulsification Efficiency  Demulsification: Breaking of liquid-liquid emulsions  Improved demulsification efficiencies attributed to “percolation” (0.2) and “bicontinuous” ( ) phenomena I. Evdokimov, SPE

How Nanocolloidal Research can be Useful in Reservoir Engineering  Avoid any lengthy operations in the vicinity of the temperature-defined boundary “A” (Fig. 5) to avoid increase in viscosity and pour point (Fig. 9)  However, storage at this boundary “A” may result in increases stratification of petroleum light/heavy components (Fig. 9)  Approaching a nanophase boundary by blending crude oils may result in viscosity and density peaking (Figs. 6,7) ere2007.com

Conclusions

 In petroleum engineering, nanotechnologies are not considered important enough for widespread use, except for in refineries and “smart fluids” for EOR  This research shows there is enough evidence to consider oils as “association nanofluids”  Emerging technologies should account for complex phase diagrams of nanocolloids capp.ca

Further Research  This research is far from complete  Much more investigation need be done on the complex phase diagrams regarding asphaltene nanocolloids  Other types of nanocolloids should be investigated and their phase diagrams drawn up as well  Various other colloids (such as water) should be investigated in regards to property changes careers-scotland.org.uk

References  Evdokimov, Igor N., Nikolaj Yu. Eliseev, Aleksandr P. Losev, and Mikhail A. Novikov. "Emerging Petroleum-Oriented Nanotechnologies for Reservoir Engineering." (2006). Society of Petroleum Engineers. Web. 10 Mar  Ratner, M. A., and Ratner, D.: Nanotechnology: A Gentle Introduction to the Next Big Idea, Prentice Hall, New Jersey,  Crane, C., Wilson, M., Kannangara, K., Smith, G., and Wilson, W.: Nanotechnology: Basic Science and Emerging Technologies, CRC Press,  Jackson, S. A.: Innovation and Human Capital: Energy Security and the Quiet Crisis. Am. Petrol. Inst.,  Asphaltene Deposition and Its Control”: d.Its.Control_html

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