CHE 404 - Midterm #1: Enhanced Oil Recovery Notes

Midterm #1: Enhanced Oil Recovery Notes Petroleum: Mix of hydrocarbons found in porous space of sedimentary rocks such as sandstone and limestone Portable, dense energy source May contain other elements: Sulfur, oxygen, nitrogen Trace metals Depending on pressure & temp, could be gas, liq or solid Heavy Oil: Petroleum with API gravity of less than 20° Viscous type of petroleum with high level of sulfur than conventional petroleum Hard recovery and refining due to high viscosity and sulfur content API gravity: API gravity: 141.5specific gravity -131.5 (°API) Inversely compares petroleum density relative to water If API gravity>10 , it is lighter and floats on water If API gravity <10, it is heavier and sinks in water has low proportions of volatile compounds with low MW but high proportions of volatile compounds with high MW high molecular weight fraction can be considered to be: paraffins complex aromatics asphaltenes with high melting and pour points Pour Point: Lowest temp at which oil will pour or flow when it is chilled without disturbance under definite conditions Min. temp required for oil to be able to make the oil move Asphaltenes: Brown to black powdery material produced by treatment of petroleum, residua or bituminous materials with low boiling liquid hydrocarbon Like pentane or heptane Soluble in benzene (aromatic solvents) carbon disulfide and chloroform History: Bitumen used for walls and towers more than 4000 years ago Petro used in medicine and lighting Crude oil burned to evaporate brine and produce salt Bagdad streets paved with non-volatile residue derived from petro seepages (asphaltenes) Petro distilled to produce naphtha which formed basis of incendiary Greek fire 1748, map of oil springs of Pennsylvania published by peter kalm, Russian traveler 1862, Russian refinery was built in the mature oil fields at baku Produced about 90% of world’s oil First commercial oil drill in North America was Oil springs, Ontario, Canada in 1858 US petro industry drilled 21 oil well in 1859 at Oil Creek, near Titusville, Pennsylvania Started out 25 bbl/day High demand for kerosene for oil lamps Petro refining began in the 20th century as internal combustion engine was introduced Demand was high and oil booms in texas. Oklahoma and cali quickly outpaced Penn. And Ont. Until 1950s, coal was world’s foremost fuel but petro quickly took over Present Situation: Oil industry needs a stimulus (something external that influences an activity) 80% of world petro found in middle east; majority Saudi Arabia However, in terms of overall reserves, Venezuela and Canada have maximum oil Most prolific basins have reached maturity and are slowing down Worlds demand for oil continues to grow fuelled by rapid growth of china and India Declining availability combined with rising demand exerts pressure to find alternative source Stimulus is in the form of reservoirs of heavy oil found in western hemisphere Resources are more difficult and costly to extract so barely been touched in past Could equate to the amount of resources found in the middle east Petroleum Composition: Natural mix of hydrocarbons (liquid) with sulfur , nitrogen oxygen metals and other elements Wide variety of specific gravity, API gravity and amount of residuum Vanadium, nickel occur in more viscous crud oils; adversely impact processing Major components; hydrogen and carbon with varying molecular structure Simplest hydrocarbons are large group of chainshaped molecules known as parrafins Ranges from methane (natural gas) To liquids refined to gasoline and crystalline waxes Ring shaped H-C; called naphthenes range from volatile liquids such as naphtha to high MW substances like asphaltenes Other aromatics (benzene) are raw materials for petrochemicals Petroleum Constituents: Widely varying constituents; physical properties vary also (eg colour) Provides high-value liquid fuels, solvents lurbicants etc Products separated into different generic fractions by distillation Vary from gases & liquids to near solid lubricants Fuels derived from petro contribute to 1/3-1/2 of total world energy supply Refinery residue, asphalt a premium product for roads, roofing etc Petro constituents cover wide range of boiling points carbon numbers, and other compounds of N, O, S and metal Can only be arbitrarily characterized in terms of boiling point and carbon number Some crude oils have high proportions of lower boiling comp. and others such as heavy oil and bitumen have higher proportions of higher boiling components (asphaltic components) Petroleum Origins Occurs underground at various depths n pressure Because of pressure, contains considerable natural gas in solution Underground petro is more mobile under reservoirs conditions because of elevated temps Subterranean formations decrease viscosity Geothermal gradient around 25-30°C/km depth Derived from aquatic plants n animals from millions years ago Remains mixed with mud and sand layered deposits were geologically transformed into sedimentary rock Gradually, organic matter decomposed and formed petro which migrated to more porous and permeable rocks such as sandstone and siltstone where it became entrapped Entrapped accumulations of petroleum called reservoirs Series of reservoirs within common rock structure or neighbouring formations referred to as oil fields Group of fields in single geologic environment called sedimentary basin or province Petroleum Recovery: Geologic techniques can determine existence of rock formations that are favorable for oil deposits, not whether oil is actually there Drilling is only way to ascertain the presence of oil With rotary equipment, wells can be drilled to depths of 9kms Once found, may be recovered (brought to surface) by pressure created by natural gas or water within reservoir Crude oil can be brought to surface by injecting water or steam in reservoir to raise pressure artificially or by injecting substances (CO2, polymers solvents) to reduce crude oil viscosity Thermal Recovery methods frequently used to enhance production of heavy crude oils Bcuz extraction is impeded by viscous resistance to flow at reservoir temp. Primary Recovery refers to process which petro in reservoir trap is forced to the surface by the natural pressure contained in the trap When reservoir is drilled. Pressure of water pushes oil upwards and replaces it in rock pores Recovery process known as water drive (pic) If drill penetrates layer of oil that has gas cap above it, pressure of gas forces oil down and eventually up the well Known as gas cap drive (pic) Gas dissolved in oil may be released as bubbles when trap is pieced Oil moves up, gas in oil expands and growing bubbles push oil to surface Known as Solution gas drive (pic) Most reservoirs have enough pressure to initially force petro to surface but pressure falls and petro production decreases because Less driving force for oil towards the well Gas moves into emptied pore spaces reduces the permeability of the rock, making I more difficult for oil to flow Fall in pressure & loss of dissolved gas increases surface tension and viscosity of oil Primary recov. Techniques account for 30% of total volume Secondary Recovery involves trying to maintain reservoir pressure Inject natural gas into reserv. Above oil forcing oil downwards then injecting water below oil forcing it upwards Gas used was gathered in primary recovery Disadvantage is released gas is marketable prduct Good method however because transporting gas is costly Re-inject gas can always be collected again Alternative secondary tech. involve Injecting CO2 and N into oil Makes oil more fluid and gas pushes oil upwards Tertiary recovery is most expensive approach which involves: Injecting steam, detergents, solvents Bacteria or bacterial nutrient solutions into remaining oil Steam Flooding: High-pressure steam heats oil, decreasing density and viscosity and increases flow rate Sometimes, oil set on fire to increase flow rate of the oil ahead of the combustion front Chemical Recovery: Injected Detergents reduce viscosity of oil and act as surfactants Reduces the ability of oil to stick easier for it to be flushed out Pic: Bacteria: Injecting bacteria into oil field Some bacteria produce polysaccharides which reduce permeability of the water filled pores of the reservoir and allow the injected water into the oil-filled pores pushing the oil out Some produced CO2 which helps increase pressure Other bacteria produce chemicals that reduce viscosity Petroleum Processing: After recovery, petro is transported to refineries by pipelines or ships Basic refinery process is distillation Separates crude oil into fractions of differing volatility After distillation, separation methods are used Adsorption, absorption Solvent extraction, crystallization Resulting constituents as light and heavy naphtha, kerosene and light and heavy gas oils may be subjected to thermal cracking(coking) and catalytic cracking Cracking breaks large molecule of heavier oils into smaller molecules that form lighter, more valuable naphtha fractions Reforming changes structure of straight chain paraffin molecules into branched-chain iso-parrafins to raise octane number of gasoline Heavy Oil Resources: Large resources in Canada, Venezuela, Russia US etc North America provide only 2% current oil production Heavy oil can be profitable but at smaller profit margin compare to conventional oil due to higher production cost Much more difficult to recover than conventional oil Has higher viscosity and usually requires thermal stimulation in reservoir Type of crude oil that is very viscous and does not flow easily High specific gravity, low H-C ratios, high C residues and high contents of asphaltenes, heavy metals, sulfur and N Needs specialized recovery and refining processes to produce useful fractions like naphtha, kerosene and gas oil Heavy oil reservoirs originated as convention oul that formed in deep formations but migrated into the surface region where they are degrade by bacteria and by weathering Deficient in H and has high C , S and heavy metal content Requires additional processing for suitable refinery feedstock Heavy oil accounts for double the resources of conventional oil and offers the potential to satisfy current and future oil demand However more difficult to recover General definition of H-Oil is based on API gravity and viscosity Example, H-oils considered to be crude oil that has less than 20° API with heacy oils falling in the range of 10-15° Cold lake H-crude oil has 12° API-g Extra heavy oils (tar sand bitumen) have 5-10° API gravity Athabasca bitumen 8° API KNOW viscosity vs API gravity graph KNOW viscosity vs temp Vacuum residua range of 2-8° API Heavy oils have sulfur content higher than 2% by weight Extra heavy oil is applied to tar sand bitumen, which is incapable of free flow under reservoir conditions Bitumen recovered by mining Recovery depends on both characteristic of the oil as well as the reservoir such as temperature and pour point of oil Heavy oils fall in a range of high viscosity Viscosity subject to temperature effects, which is the reason fro the application of thermal methods of oil recovery Bitumen: Portion of petro that exist in reserv in semi-solid or solid phase Contains sulfur, metals and other non-hydrocarbons Natural bitumen viscosity of 10,000cP measure at the original tern perature of the reserv at atmo pressure and gas-free Frequent treatment before being refined Naturally occurring, found in deposits where permeability is low and passage of fluids can be achieved by fracturing tech. Recovery depends on composition and construction of sand Bitumen found in tar sand is extremely viscious and immobile under reserve conditions and cannot be recovered by second. Or enhanced recovery techn. Tar Sand (Bituminous Sand/Rock): Formation of bitumen is found filling in veins and fissures in fractured rock or impregnating relatively shallow sand, sandstone and limestone strata Sandstone reserve that is impregnated with heavy viscous black petro-lick material cannot be retrieved through a well by conventional techn. United states Federal Energy Administration: Several rock types that contain extremely viscous hydrocarbon which is not recoverable in its natural state by conventional oil well production including enchanced recovery techn. Hydrocarbon bearing rocks known as bitumen-rocks oil, impregnated rocks, oil sands, rock asphalt Tar alone implies heavy product remaining after destructive distillation or coal or other organic matter Pitch is the distillation residue of various types of tar Bituminous rocks=oil shale Oil shale are argillaceous, laminated, sediments of generally high organic content that can be thermally decomposed to yield appreciable amounts of oil, referred to as shale oil Pour point and reservoir temp used to better understand the difference between heavy oil and bitumen Heavy oil have less than 20° API gravity Bitumen have less than 10° API gravity Fossil Energy Resources : Categorized as naturally occurring hydrocarbons (petro, Natural gas, waxes hydrocarbon sources (oil shale, coal) conventional crude oil produced by primary & secondary techn. Where heavy oil requires tertiary and enhanced recovery bitumen near solid at room temp and at reservoir temp and requires extreme stimulation for recov. Bitumen is not crude oil and cannot be recovered by deposits Must be mined or by hot water process Bitumen is upgraded and converted to synthetic crude oul by thermal/hydrothermal process followed by a product hydrotreating to produce a low-sulfur H-C product know and synthetic crude oil Heavy oil is mobile in reserve and can be recovered by application of EOR technologies such as steam-based tech Bitumen: Characterized by pour point lowest temp at which oil will move, pour, flow when is it chilled wthout disturbance under definite conditions pour point of oil with reserve temp gives better indication of condition of oil than viscosity EXAMPLE, Athabasca bitumen with pour point of 50-100°C and deposit temp of 4-10°C is solid and have no mobility under conditions Injection of steam to raise and maintain resev temp above pour point of bitumen is difficult and nearly impossible Conversely, when reserv temp exceeds pour pint, oil is fluid in reserve and mobile Injection of steam raise and maintain reserve temp above pour point to enhance bitumen mobility is possible and recovery can be achieved KNOW CLASSIFICATION OF FOSSIL FUEL AS HYDROCARBON RESOURCES KNOW STATE OF OIL VS. RECOVERY SUMMARY: Heavy oil is more viscous than convention oil but is more abundant and requires dif methods of recovery Heavy oil is mobile in reserve where bitumen is immobile in deposit Properties vary with locations and reserve where they are found NATURE OF HEAVY OIL: Lower boiling components lost naturally, making oil heavy with high proportion of asphatic molecules and N, S, O in carbon network of hetero-atoms Contains heavy fractions or asphaltic materials Removal or reduction of asphaltene fraction by deasphalting or leaving them behind in reservoir improves refinability of heavy oil Asph. Impact capital and operating expense require for recov. Transportation refining and environmental restoration Detection of H-C taks number of forms: Direct identification of H-C @surface Direct identification H-C indicators @subsurface indirect identification of indicators at both @surface &subsurface Oil Exploration: traditionally simple recognition of oil that has seeped to the surface Colonel Edwin Drake drilled first well in Oil creek Pennsy. To search oil in subsurface in 1859 Direct identification when seeped H-C at surface Pioneers looked for potential reservs, seals and source units as well as frequency, orientation and geological history of folds and faults that could be H-C traps Plate Tectonics: one of more important developments in petro studies Movement of plates creates large scaled depressions into which quantities of seidments eroded from surrounding high ground may accumulate Accum. Can be thousands of km think and referred to as sedimentary basins Comparisons with basins n H-C producing regions help narrow down search for reservoirs Mapping of gravity and magnetic anomalies used to identify large-scale changed in structure of basement and sedimentary basins and major diff in rock density Can be applied for land and water and can be collected from plan or satellite Large scale photogeolocial surveys and satellite imaging shows anticlinal and faulted structural features, seeps and salt domes frequently associated with oil occurrences 2-D grid of seismic data collected to obtain pic of subsurface of targeted area Involves generation f seismic wave using energy source like air gun or dynamite Waves travel through earth’s rock layers and reflects back off key surfaces Reveals detailed structure of subsurface (software) Used to indicate nature of folded and faulted structures that could lead to H-C leads 3-d and 4-d also used for detailed analysis Particularly important in monitoring production performance of reserv In the end, only way to confirm presence or absence of H-C at depth is drilling Drilling is preferred over extensive and expensive seismic techni. Wells analyzed using electric, sonic radioactive logging techni that measure characteristics of rocks n fluids Cost of 10 million per offshore exploration well, companies use direct n indirect methods before drilling Theories of Origin of Oil Heavy oil biologically degrade and weathered by water Bacteria feeding on mitrated conven oil removing hydrogen and producing denser, heavy oil Also light H-C could have evaporated Abiogenic Origin Theory: Large amounts of C exist naturally, some in form of H-C H-C less dense than aqeous pore fluids and migrate upward through deep fracture networks Thermophilic, rock dwelling microbial life forms responsible for biomarkers found in petro Role not yet understood N-alkanes (common in petro) do not spontaneously evolve from methane at pressures found in sedimentary basins Theory suggests origin of H-C from deep generation (below 190km) Biogenic Origin Theory: Theory suggest petro formation arises from decay or organic matter in earth Progressive change of materials by microscopic aquatic organisms over eons in marine or near marine sedimentary rocks Transformation began soon after deposition with bacteria playing role in initial stags and clay as catalysts Heat within strata provide energy for reaction with temp increasing with depth Petro formed at temps not exceeding 100-120C w/ H-C forming at temps low as 65C Most heavy oil and bitumen is expelled from source rocks as light or medium oil which mitgrates to a trap If trap is elevated into oxidizing zone, several processes cant convert oil into heavy oil like: Water washing Bacterial degradation (aerobic biodegradation) Evaporation Biodegradation proposed to also occur at depth in subsurface reserve that have a water leg and have not been heated to more than 80C Heavy and conventional oil can vary in composition depending on age and location of reserve Lower mobility of heavy oil makes it likely two wells in same reserve will produce heavy oil with dif characteristics Occurrence and Distribution: Petro found in sedimentary rocks throughout world 4 main issues control occurance and distribution of convention n heavy oil: Source Reservoir Seal Trap Source: Fine grained rock unit containing sufficient organic matter that generates H-C when heated or pressurized Marine algal most like to generate oil under optimum maturation conditions Rocks by land plant matter will tend to create gaseous H-C Lower gravity than surrounding ground water there move away from source rock (upwards) until they are trapped in reserve Remains of enormous quantities of aquatic plants and organisms mixed with sand and muf at bottom of water Reservoir: Pressure from earth’s crust forced petro into tiny open spaces Reservoir is a rock unit that acts as a storage device from H-C that migrate from source rock Good quality reserve, porosity is 20% of rock volume However, pores need to be interlinked in a manner that fluids can move into and out (exploration) 2 main types that make giant reservoirs: Sandstones: Made up of sand grains (quax and feldspar) Carbonates Calcium carbonate grains (corals, algae, sheels) or mud Seal: To stop upward movement of H-C and constrain them to on zone Seal consist of rocks that are impermeable to fluid flow Mudstone or shale Very fine0grained rocks containing clay minerals Dense igneous rocks Sometimes, signfitcant rock and fluid pressure differences that prevent H-C movement Traps: For petro commercial quantities, trap must have persistent to prevent its escape 2 major kinds of traps: Structural Created by deformation of earth’s crust Folding or faulting of rocks rsults in entrapment of petro Stratigraphic Due to higher porosity and permeability of oil-bearing rocks that of adjacent rocks Most contain salt water Natural gas always present Important to maintaining pressure during production Oil Exploration and discovery: 600 basins found Tracts of land tilted toward common center 400 actually drilled and explored 160 have produce commercial quantities 200 have not been touched as for restrictions Like governments, territorial disputes etc 25/160 basins account for 80% of total discoviers (10 billion barrels) Destin Dome extremely promising petro potential (600 milllion $$$) but had many dry holes Heavy Oil Categories: Shallowst resources (<150ft) Shallow resources (150-300 ft deep) Medium depth (300-1000ft, pressure <200 from cap rock seal) Intermediate depth (1000-3000ft, pressure >200psi) Deep (>3000ft) Carbonate resources (variable porosity) Thinly bedded resoucres (<30ft thick) Highly laminated resources (low vertical permeability, often shale layering) Reservoirs: Heavy oil found in artic, Africa, north and south america Most heavy oil recovered produced from under ground reserve Presence of active seeps in area is evidence that oil n gas are still migrating When the pour point of the oil is lower than the reserve temp (sufficiently high reserve temp), heavy oil can be recovered by means in conventional way However, as it reaches surface, it can become really viscous Very shallow heavy oil reservs can be mined and oil allowed to drain into mine tunnel Deeper deposits can be produced by horinzontal wells or injecting steam, lowering viscosity and improving recovery efficiency Oil Reserves: Most nations do not reveal data and provide underestimated claims Can be manipulated for political reasons Total amount of conventional Oil or heavy oil in a reserve s know as Overall Oil In Place (OOIP) Only fraction of oil can be brought to surface Ratio reserve to OOIP referred to Recovery Factor May change over time Ex. Investments such as gas injection or water flooding Most early estimates of reserves of oil field are conservative and tend to grow with time, called Reserves Growth Reserves classified as Proven Reserves that are actually found by drilling operation and recoverable by current technologies High accuracy Potential Based upon geological info about types of sediments which are likely to occur Educated guess Probable Reserves that are nearly certain but have slight doubt that it exists Possible Reserves with greater degree of uncertainity about recovery but about which there is some info Undiscovered None Total Petro-initially in place Quantity of petro that is estimated to exist originally in naturally occurring accum Discovered petro-initially in place That is estimated, on a given date, to be contained in know accum and that already produced therefrom Undiscovered petro-initially in place Quantity of petro that is estimated on given fate to be contained in accum yet to be discovered Classified as prospective resources Contingent Resources quantities of petro that are estimated on a given date to be potentially recoverable from known acumulaions but are not currently considered as commercially recoverable accum for which there is no current marker and recovery dependent on development of new technology or evaluation still at early stage Estimated Ultimate recovery (EUR) Petro that is estimated to be potentially recoverable from an accum and those quantities already produced therefrom Term applied to individual accum of any status/maturity (discovered or undiscov) LEARN RESOURCE ESTIMATION CHART Terms low ,best and high estimate Best estimate: closest to the quantity hat will actually be recovered from accu between date of estimate and date of abandonment Low and high are ranges for best estimate Reservoir: Subsurface, porous, permeable rock that has the capability to sore (porosity) and transmit its fluids (permeability) 1-100?m in length and diameter Common reserve rocks Sandstone Limestone Dolomite Created by deposition, conversion, migration and entrapement of H-C To produce oil, fluids flow to well-bores through heterogeneous porous media of the reserve Fluid movements governed by potential gradients, permeability, injection and production points and viscosities Elements of Reservoirs Source rock containing organic matter converted into petro Migratory athway from source work to reserv rock To stroe and yield fluid Seal- impermeable cap rock that prevents upward escape of petro to surface Trap- physical arrangement or space that prevents migration Factor Affecting Production: Composition of reservoir fluids Reservoir fluid properties Before and following production Atmospheric conditions Reserv Pressure data Producing area, height of column of H-C fluid, fracturing or faulting, amount of water production Mobility of fluids Geometry, structure of reserv Processes: Deposition: Occurs when organic rich sediment settles in regions (rivers, continental shelves) Silt or clays atop sediment keep out O2 T & P increase w/ depth and deothermal gradient (25-30C/km) converts organic matter to petro Conversion: Breakdown of organic matter Involves: Diagenesis Catahenesis Metagenesisto form kerogen Kerogen is high MW org residue found in many types of sediment (ex Oil shale) Migration: Movement of oil/gas from its source rock to a reserv rock Porosity n permeability control movement of H-C Entrapment: Occurs when H-C move into formation that is sealed (ex. Shale; fine grain size has very high capillary forces that prevent fluid flow) Cannot be retained unless there is a trap Trap forms when buoyancy forces driving the upward migration of hydrocarbons through permeable rock cannot overcome capillary forces of sealing medium Seal is fundamental part of trap that prevents further upward migration Common trap is anticline trap (DRAWING) fold of rock that is convex upward and sealed at top and bottom planar fracture/discontinuity across rocks can help retain oil called Fault Trap (DRAWING) Salt dome trap (DRAWING) Anticline, fault n salt dome traps are called structural traps Majority of petro found in these traps Stratigraphic traps: (DRAWING) Hold oil due to change rock properties instead of structural dif Hydrodynamic Traps: Least common, caused by diff in water pressure that will not allow oil to move out Pores of Reservoirs: Pores r opening b/w grains of rock, cavities inside fossils and openings caused by dissolution or fracture Pores = 1mm wide Fossil Cavities = 30-50mm wide Fractures may be 1mm but extended over many KM Connectivity of pores provides permeability Heterogeneity: Affects fluid movement and hence oil production If unaccounted, can lead to erroneous estimates Wettability: Tendency of one fluid to spread on or adhere to a solid surface in presence of other immiscible fluids At equilibrium, wetting fluid completely occupies smallest pores and is in contact w/ majority of rock surface Reservoir could be water-wet or oil-wet One of the important parameters influencing saturation, distribution, and flow of fluids in porous media Ex. Water flooding; a strongly oil-wet rock is much less efficient than one in water-wet rock In heavy oil reservoir, amount of gas will be less than conventional oil Reser. Usually contain natural gases, oil, water and acid gases Distribution: Uniform distributed pores of uniform size: An upper zone, pores filled with gas (gas cap) Middle zone, pores occupied by oil n gas in solution with 10-30% water Lower zone, pores will with water Transition zones b/w these zones at certain T n P , there may be no gas cap but only oil with dissolved gas overlying the water water w/ dissolved salt (or brine) is co-produced with oil oil n gas wells produce more water than oil; 7:1 ratio Sampling: main objective is to obtain representative samples for reservoir fluids for determining their properties critical to avoid 2-phase flow in reservoir, minimize fluid contamination factors such as producing area, height of column of H-C fluid, fracturing or faulting, and water production affect fluid composition and sampling methods large complex reserv. Serveral samples required 2 types of sampling: Surface sampling Surface sample captures gas n oil samples from separator then recombined at measured producing gas-oil ratio (GOR) cleaner sample than bottomhole Subsurface, downhole, bottomhole sampling Close to reservo. Conditions Adequate cleaning needed Avoid 2 phase flow Advantage of capturing fluids at reservoir conditions Main advantage, offers viable means to capture single phase samples and eliminate uncertainties associated with surface samples heavy oil Sampling requires xtra step: adequate near wellbore cleaning to mins sample contamination optimal drawdown to min sand production and avoid 2 phase flow H-Oils require customized PVT cells Fractionation: Physical composition of crude oil as determined by various physical techn. Most common fraction: asphaltenes After removal of asphaltene fraction, further fractionation of petro is also possible by variation of H-C solvent Fractionation of heavy oil into components other than asphaltenese proves useful info about recovery process Methods include: PONA (parraffins, olefins, naphthenes, aromatics) PIONA (parraffins, iso-parafinns, olefins, naphthenes, aromatics) PNA (parraffins, naphthenes, aromatics) PINA (parraffins, iso-parraffins, naphthenes, aromatics) SARA (saturates, aromatics, resins, asphaltenese)