R.B.Seyful-Mulyukov, E.N.Arutyunov
Genezis nefti. Analiticheskiy obzor
Petroleum Genesis
Analytical Review.Extended Summary of Russia publication
DOI: 10.14357/seyfulbook2013
The analysis of modern conceptions of the genesis of petroleum andhydrocarbon gases is presented. The analysis is exposed throughtwo existing models of their genesis: organic and inorganic ones.
They contradict each other concerning the mother matter and theprocesses of its transformation into petroleum and gas. During last50 years, the organic model is dominating in petroleum geology, aswell as in companies carrying out petroleum and gas exploration and
in universities teaching petroleum geology to students. The organicmodel is based on the assumption that the source of mother matteris the remainders of bacteria, plants, and animals. Such assumptionleads to logical consequences that are forced to be doubt about thismodel in whole. Let consider them.
1. In organic model, the mother matter is the lipid reminders ofmicroorganisms and lignin reminders of plants lived in the pastgeological periods. So, starting from Precambrian (650 million years ago), biosphere was capable to reproduce itself suchamount of organic matter to deposit into sediments to formmother matter from which billion tones of petroleum and trillion cubic meters of gas were generated later on. The weightof all lipids and lignins composed from terrestrial and marineorganisms is by several thousand times less than hydrocarbonspreading into Earth￡s crust. The calculations show that all organic matter accumulated during 1 million years is not enoughto produce petroleum to fill up one giant oil field. The idea oforganic nature of mother matter was not proved and it is the first dogma of organic hypothesis.
2. In organic model, the organic reminders are accumulated in marine bottom sediment. Later on, they form kerogen that is theraw material for petroleum and gas generation. The main process of kerogen transformation into petroleum is kerogen katagenesis or slow heating while mother matter is slowing down intohot depth strata of Earth. This process has not been provedaccording to thermodynamic principles (entropy change). However, mother beds of some regions have never reached the depthwith the temperature necessary for kerogen katagenesis. Romashka petroleum field in TatarstanRepublic and most of Persian Gulf petroleum giants can be served as examples. Theirmother matter has never reached the temperature level required
by katagenesis. It is the second dogma of organic model.
3. Organic model followers consider that petroleum and gas havebeen generated into mother bed or in some sort of generating natural kettle when migrated, mainly, horizontally throughsedimentary formations and finally accumulated into reservoirs.The distance of this petroleum and gas migration could be hundreds of kilometers. But experimentally and theoretically, it wasproved that the long distance migration of hydrocarbon fluidsthrough horizontal formation is impossible due to diffusion, filtration, and any other mode of movement as well as interactionwith geological media. Petroleum and gas horizontal migrationis impracticable and can be considered as a dogma only.
4. Currently, petroleum industry specialists say: Devonian crude,oil, Pennsylvanians crude and so on. This statement obviouslymeans that petroleum and gas after have being generated canstay into reservoir or somewhere else during hundreds of millionyears without changing its chemical composition. Such abilityis not compatible with petroleum as thermodynamic system asits entropy is changing. Such ability of petroleum contradicts
to its physical and chemical instability as the solutions of thecomplex composition.
Let analyze the correspondence of petroleum organic nature toits chemical composition and occurrence in the Earth crust.
Ninety percent of petroleum is composed by the molecules thatconsist of carbon and hydrogen atoms only. They are the pure hydrocarbons which are not presented in any living organism. But themolecules of lipids and lignin as organic acids could not be transferred into pure hydrocarbon ones under katagenesis condition dueto the lack of energy. Obviously, it means that at least 90% ofpetroleum hydrocarbons do not have organic nature.
Color and aggregate state of hydrocarbons change from deepstrata to surface in consecutive order. Color changes from lightcondensate and light petroleum to dark heavy oil and black bitumen.In the same order, aggregate state of hydrocarbons changes from gas,condensate to petroleum, heavy oil, and, finally, bituminous rocks.Vertical differentiation of hydrocarbons reflects their genesis as theprocess directed from Earth`s deep strata to the surface (Figs. 1and 2).
Occurrence of petroleum and gas commercial accumulations isvery indicative. Accumulations are located in the rocks of any composition, any age, in all continents and continental shelves. Globaloccurrence of petroleum and gas accumulations is the reflection of
unique mechanism of their generation and deep unique source encircling of all the Earth￡s crust. The generation of petroleum and gasinto isolated sedimentary lenses, existed in the past geological periods, completely does not correspond to global, over all occurrenceof petroleum and gas accumulations.Summing up, it can be stated that petroleum composition, color, and aggregate states as well as its occurrence do not prove themain points of organic model.
One may ask why there areso many contradictions in organic model. Why are their basic points that became dogmas stillin use by all petroleum exploration companies in the processes ofpetroleum and gas accumulations exploration and risk assessment?
The answer is simple. Because of the tradition which camefrom petroleum colleges and universities. During last 60 years, thepetroleum geology as the discipline teaching to students is based onorganic model only. It became the only truth like the Bible.
In reality, petroleum field geologist has never fitted the basicconditions of any model with main element that provides petroleumand gas accumulations. They are structure, reservoir, shield of impenetrable rocks, and canal of fluid migration. The problem is thatelements as petroleum geology alphabet do not run out logicallyfrom mechanism of petroleum and gas generation in mother rocks.That is why, for geologist, the assumption that petroleum and gashave been generated, for example, 100 miles away and 100 millionyears ago cannot be and is not in reality interesting and important.
Figure 1 Gaseous hydrocarbons generation and migration
Figure 2 The main stages of hydrocarbon molecules generation
Many Russian geologists and geochemists step by step beginsupporting the idea on the deep, inorganic petroleum and gas genesis. The main substitution of deep petroleum origin proceeds frombasic things.
First point. Petroleum is the complex system of the hydrocarbon molecules organization. Ninety five percent of them consist ofcarbon and hydrogen atoms. Atoms appeared in the mantle as theresult of decompression its super compressed homogeneous substanceexisting in the state of elementary particles [1, 2].
Second point. The further transformation of carbon and hydrogen atoms has happened according to general development ofmatter. It was established by V. Ambartsumyan in 1960 [3] on thebasis of astrophysical observation and has universal meaning. Thematter is developing from simple state to the mode of complex organization from more condense state to less one, from more heatedto cold state. As far as it is universal law, it could be applied tothe development of complex system that petroleum is. Petroleumgenesis is a consecutive process of the transformation of simplesthydrocarbon molecules that appeared in the upper mantle into thecomplex ones during their migration.For the first time, the present authors introduced the idea aboutinformation content of hydrocarbon molecule calculated in bit because it directly concerns the petroleum genesis process. Physicistsand mathematicians proved that information is one of the fundamental attributes of matter intrinsic to all atoms including carbonand hydrogen ones.The cognition of information as the phenomena from physical,mathematical, philosophical, and biological points of view was presented by Tisso and Velte [4] much earlier than the organic model.In 1900, Planck stated the hypothesis on the quantum behaviorof the elementary particles. It means that particles beside corpuscular properties irradiate quant of energy and possess wave function.Later, Heisenberg [5] established kinematics and dynamics of elementary particles in the form of quantum field theory.Brilluen [6] introduced notion .bound information\ and .information entropy\ that meant the application of the physical value toexpress the thermodynamic state of complex system.Ashby [7] contributed into the cognition of the relation betweeninformation and variety, complicity, and organization. These notions refer to organic and inorganic systems in biology, geology, geography, and topology as well as in many others sciences. Ursul [8]presented the analysis of information phenomena from philosophical, mathematical, physical, and biological points of view.Zeilinger [9] taking into consideration the features and performance of elementary particles in quantum field formulated theprinciples of information quantization and connection between elementary systems and information. He concluded: .An elementarysystem carries 1 bit of information.
Let apply the information characteristics to the hydrocarbonmolecules.As it was calculated by Gurevich [10], the information contentof five atoms constituting 99% of petroleum is as follows: C - 109,H - 10, S - 317, N - 139, and O - 149 bit.. Petroleum genesis is a consecutive process of simplest hydrocarbon molecules transformation into complex ones. It means thatthe sequence of hydrocarbon molecules created in the process couldbe expressed by the formulas as well as by the bit of information.
Carbon and hydrogen atoms and some hydrocarbon molecules created during theprocess have been considered as an example just demonstrate theidea:
Hydrogen and carbon atoms -hydrocarbon protomoles - (aliphatic) methane -izopentane -(aromatic) benzene -...... - (heteroatomic) pyridine -light petroleum -bitumen.
If one express this sequence by the formulas it will looks like:
H,C - CH -CH4 -C5H10 -C6H6 -C5H5NO -...... -C32H66OSN -C45H51O2SN.
The same sequence expressed by bit of information looks like:
10 -109 -119 -154 -605 -711 -883 -4862 –6219 bit.
The substantiation of deep inorganic petroleum genesis needsto take into account two more important factors that are usuallybeyond consideration.
1. During the genesis process, independently whether it is organicor inorganic one, carbon and hydrogen atoms are not additionally retried from any carbon-containing rocks. In organic model,initial quantity of carbon and hydrogen atoms consists of organic reminders and while passing to kerogen does not changeduring all kathagenesis stages. Their initial quantity providesthe genesis process.In inorganic model, carbon and hydrogen atoms are continuously supplying by mantle substance decompression. Duringhydrocarbon molecules transformation in lithosphere, carbonand hydrogen atoms are also not retrieved from any rocks thatcontain them.The constancy of initial carbon and hydrogen atoms during allgenesis process shows that petroleum is the self-developmentprocess of matter (in this case, of the hydrocarbons system)without input of carbon and hydrogen atoms from other lithosphere systems.
2. Petroleum consists of three types of molecules: aliphatic, aromatic and heteroatomic [11]. The molecules were created ondifferent stages of genesis process. In this case, the question arises why, finally, more than 500 molecules, from which petroleumconsists, created on different stages of the process did not changetheir composition and structure? The answer is in quantumbehavior of the elementary particles of carbon and hydrogenatoms that compose all hydrocarbon molecules. Initial hydrocarbon protomoles formation just after atoms appearance means consecutive overlapping of their atoms orbitals. The order ofoverlapping keeps quantum state of atoms in the initial hydrocarbon molecule. In this way, the invariable quantum matrixof hydrocarbon molecules was created which has informationcontent as well (see below). During further molecules transformations, the matrix does not change. That is why, one type ofmolecules does not disappear during further genesis process butin primeval form are included in the system composition. Matrix or the main quantum state of carbon and hydrogen atomswave field did not change under any state of the system.
All the facts, considerations, and logical consequences setforth above allow believe that petroleum genesis is a processof consecutive transformation of carbon and hydrogen molecules(see Fig. 1).
Joining of carbon and hydrogen atoms into simplest methanemolecule on the deep interior corresponding to about +1500 ◦Cis the starting point for all variety of hydrocarbon molecules formation. Methane formation is the modern process embracing allEarth￡s sphere between mantle and lithosphere. From this level ofenergy, methane gives birth to two branches of hydrocarbons stream(see Fig. 1).The fist one is the vertical transit of gaseous hydrocarbons without loss of their chemical composition. Due to small size of molecule(gas kinetic diameter of methane molecule is less than 5.88 ’A),methane can migrate through cracks, split, faults, and fractureskeeping its chemical composition. Kadik and Lukanin [12] established that methane is magma phobic and can be carried by magmaplumes without solving into magma melt.
By one way or another, methane migrates up constituting themain ascending hydrocarbon flow. Its scale exceeds atmosphere- biosphere- ocean carbon cycle by many times. Methane vertical flowis formed by its scattering into atmosphere, accumulation on ocean
bottom as gas hydrate and the accumulation into reservoirs as gas fields.
The second branch of methane stream is its migration resulted by the transformation of one type of hydrocarbon molecule intoanother and the only way of it is the catalytic transformation. Jarmain [13] showed many ways of hydrocarbon catalytic conversionoccurred during interaction of electron structures of carbon and hydrogen atoms with the catalyst ones. The role of the last ones playsaluminum silicates and transitional metals that compose the rocks.
Catalytic reactions under specific temperature and pressurelead to the formation of all variety of hydrocarbon molecules. Thereactions are progressing without changing the carbon atoms number in the molecules (isomerization) or with their number changing(hydrogenization and dehydrogenization), alkylation, or polymerization. The generation of high molecular hydrocarbons during fluidmigration can take place during any of four stages.The first stage is the formation of the chain type of hydrocarbonmolecule while carbon atoms are joining by one bond and thus creating carbon skeleton. In that way, alkanes (paraffin or saturatedhydrocarbon) are generating. During the second stage, the chain ofcarbon atoms is closed up to the circle forming alkenes (naphthenesor isoparaffin). They are capable to exist under less tense thermodynamic conditions and are more volatile than alkanes with thesame quantity of carbon atoms. Naphthenes form many differentstereo chemic molecules due to their volatility (see Fig. 2).
The third stage is the aromatic molecules appearance. Thistype of carbon atoms joining creates the molecular structure morestable compared to the chains and the circles ones. The moleculeof aromatic hydrocarbon (benzene) has no double bond betweencarbon atoms. Valent bond role plays the valent orbital that consists of sixelectrons captured from each carbon atoms theseformingtwo electron cloud. Aromatic molecules can consist of two, three, four, |ve, and more aromatic rings.
Summing up the model of the deep inorganic model ofpetroleum and hydrocarbon natural gas genesis, one can state:
1. The petroleum and hydrocarbon natural gas genesis is the contemporary process that is the privilege of modern geologicalperiod.
2. Petroleum is a final product of catalytic conversion of the simplest hydrocarbon molecules into the complex ones. The processbegins in the upper mantle by carbon and hydrogen atoms appearance. They form the simplest hydrocarbons that are transferred into all variety of petroleum hydrocarbons. Algorithmof hydrocarbons conversion is obeying to the law of the energyconservation under matter conversion from one form to another.The process ends in reservoir where immediately petroleum destruction starts. It is the law of evolution. The driving forceof the process is the change of thermodynamic conditions forascending hydrocarbons flow.
3. Hydrocarbon gases in the pools and gas hydrate on the oceanbottom are the finish strata of gaseous hydrocarbons, mainly,methane migration.
4. Petroleum or/and gas is/are concentrating as commercial accumulations under obvious presence of trap, reservoir, shield,and canal for fluid migration. Accumulation can take place in
the any geological object that is the combination of trap, reservoir,and shield. Geological object can be seated in sedimentary,metamorphic, or magmatic rocks. Phase state of hydrocarbonin accumulation (gas condensate, light crude oil, heavy crudeoil, bitumen andothers) depends upon thermodynamic conditionsand geologic media.
Finally, let consider how inorganic model of petroleum genesis effectson the exploration work in the given license block. Recently, its geological structure was reconstructed by compiling three-dimensional(3D) basin model that shows structural and rocks assemblage interaction and heterogeneity. The model was compiled on the baseof wells and geophysical data. It is a 3D picture, some sort of thedigital photo of Earth interior.Geological interpretation of this 3D scheme is the reconstruction of the main factors of petroleum and gas accumulations. Theyare geological structure and petroleum and gas source or the location of place they are come from. Field geologist can recognize the first factor from the digital 3D model because they are structure,reservoir, and shield.The reconstruction of petroleum source and genesis processis the main problem in the practical application of the theory ofpetroleum geology. Geologist having in mind organic model mustdetermine the mother bed location and then understand how fluidshave migrated to reservoir. Both tasks have no solution neither fromtheoretical nor practical points of view. Mother bed can gave birthto petroleum sometimes, may be 100 million years ago, and somewhere locating 100 km away from the licensing block. That is whygeologist could not get anything valuable concerning the mother bedfrom digital 3D model.
The scheme of deep inorganic genesis with dominating of thevertical hydrocarbons fluid movement save geologist from the necessity to reconstruct the process. Genesis process as well as theways of the petroleum and gas migration are progressing deep inside Earth and could not be registered by any means and expressed mathematically. Geologist has to be out of this development. Geologist just must know that petroleum genesis is contemporary process, occurring globally, on the depths corresponding tothe Earth`s crust temperature interval from +600 to +200 ◦C. Theshortest way for petroleum and gas to reach the geological objectwhere they can accumulate is the vertical migration. Hydrocarbonfluids vertical flow could be stopped up by shield rocks only butaccumulation happened if trap and reservoir were available. Trap,reservoir, shield, and canal of fluid migration are the main aims ofgeologist who explores petroleum and gas accumulation.