石油地质学英文课件Chapter-1

1、Chapter 1 Crude Oil, Natural Gas, Oilfield Water,Crude oils Natural gases Oil-field waters,1 Crude oils,1.1 Definition 1.2 Chemical properties 1.3 Distillation 1.4 Classification 1.5 The differences between marine and terrigenous oils 1.6 Physical properties,1.1 Definition,Crude oil is defined as a

2、mixture of hydrocarbons and non-hydrocarbons that exists predominantly as liquid, with varying amounts of dissolved gases and/or semisolid hydrocarbons in natural underground reservoirs.,1.1 Definition,The word petroleum originates from the Latin words petra(“rock and stone”) and oleum(“oil”), just

3、like its Chinese word, 石油 means “石” and “油”. Petroleum is a kind of mineral resources that occurs in the earth as gas, liquid, semi-solids or in more then one of these states. Liquid petroleum is called crude oil that consists chiefly of the liquid hydrocarbons, with varying amounts of dissolved gas

4、es, bitumens, and impurities, which can be produced from underground reservoir rocks through a drill pipe.,General Features,Chemically any liquid petroleum is an extremely complex mixture of hydrocarbon compounds, with varying amounts of non-hydrocarbon compounds of nitrogen, sulfur, oxygen and also

5、 vanadium(V) and nickel(Ni) as impurities. The proportions of the hydrocarbon constituents and the contaminants are different in various petroleum accumulations or oil fields. The physical properties of petroleum are different in various accumulations/fields.,1.2 Chemical properties,(1) Elemental co

6、mposition The main elements are Carbon and Hydrogen; The minor elements are Sulfur,Nitrogen and Oxygen (normally less than 3%); Trace elements are heavy metals,such as V and Ni.,The table below shows the elemental contents in natural gas, crude oil, asphalt, coal and kerogen,(2) Alkane series Paraff

7、ins,The general formula is CnH2n+2. C1-4 are gases. methane/CH4, ethane/C2H6，propane/ C3H8, butane/C4H10 C5-20 are liquids. C20+ are usually waxy solids. In CnH2n+2 in crude oil, usually n80. Alkane series can be divided into 2 types: a. the normal alkanes: n-alkanes b. the isomeric arkanes: i-alkan

8、es,Methane,Ethane,Propane,Butane,Pentane,Hexane,Heptane,(3) Naphthene or Cycloparaffin,general formular: CnH2n n5 The Cycloparaffins that are formed by joining the carbons in ring are the most common molecular structures in crude oils. The most common naphthenes in crude oil are methylcyclopentane a

9、nd methylcyclohexane. The average content of naphthenes is about 50% in crude oils, with the quantities increasing in the heavier fractions and decreasing in the lighter fractions.,Naphthenes,(4) Aromatic Hydrocarbons With general formular CnH2n-6; The term aromatic hydrocarbon originated from pleas

10、ant-smelling compounds in crude oils. However most HCs have very little odor in pure state. All aromatic HCs contain at least one benzene ring. They are unsaturated cycloHC series with double bonds between carbon atoms, likes benzene and its homologous: Benzene Naphthalene Paranaphthalene,(5) Nitrge

11、n, sulfur, oxygen compounds (Asphaltics),They are complex structural arrangements made of naphtheno-aromatic nuclei with chains and heteroatoms (O,N,S). Sulfur compounds：an average content of sulfur in crude oils is 0.65% by weight. Low or high sulfur crude oil: S1.0% b) Nitrogen compounds：Nitrogen

12、content is usually much lower than sulfur content in crude oils. The average nitrogen content is 0.094% by wt, in most crude oils nitrogen content is less than 0.2%. The most important nitrogen compound is porphyrin: Nickel(Ni) and Vanadium(V) porphyrin. c) Oxygen compounds: as saturated fatty acids

13、: phenols,About porphyrin,Porphyrins are characterized by a tetrapyrrolic nucleus(4 pyrrole rings), probably inherited from chlorophyll or hemin. So nickel porphyrin and vanadium porphyrin are biological markers indicating crude oils derived from organic matters. Chlorophyll, the green photosyntheti

14、c pigment of plants. Hemin, the red pigment of animal blood. There are other metals, like iron(Fe), zinc(Zn), copper(Cu), lead(Pb), arsenic(As), molybdenum(Mo), cobalt(Co), magnesium(Mg), chromium(Cr) etc in crude oils, but only a very little amount.,1.3 Distillation and uses,Distillation is the pri

15、ncipal method for separating crude oils into useful products. The common distillate fractions are: Gasoline (C5-C10) Kerosine (C11-C13) Diesel oil (C14-C18) Heavy gas oil (C19-C25) Lubricating oil (C26-C40) Residuum (C40),A distillation tower,A refinery tower is equivalent to a series of individual

16、distillation flasks, in which the distillate fractions from the first flask is condensed in the second flask, and then redistilled to produce a distillate for the third flask.,Aromatics,Naphthenoaromatics,Nitrogen, sulfur, and oxygen compounds,The light gasoline fraction of oil is dominated by the n

17、ormal, iso-, and cycroparaffins. From Gasoline into the heavier fractions, There is a marked increases in the Aromatics + naphthenoaromatics.,Aromatics,Naphthenoaromatics,Nitrogen, sulfur, and oxygen compounds,After diesel, NSO compounds content increases markedly, the residuum is dominated by NSO c

18、ompounds.,1.4 Classification,Some classifications have been proposed by geochemists and oil refiners. A classification of petroleum has been proposed by Tissot and Welte (1978) based primarily on the contents of the various structural types of hydrocarbons: P =Paraffin N=Naphthenes AA=Aromatics and

19、Asphaltenes+resins S= Saturated hydrocarbon,1) S50%, AA40%,PN: Paraffinic oils 2) S50%, AA40%,NP: Naphthenic oils 3) S50%, AA10%: Aromatic intermediate oils 5) S50%, AA50%, P10%,N25%: Aromatic naphthenic oils 6) S50%, AA50%, P10%,N25%: Aromatic Asphaltic oils,On oil types On wax contents On sulfur c

20、ontents On trace elemental contents, as V,Ni, V/Ni On stable isotopes of carbon,1.5 The difference between marine and terrigenous crude oils,1.6 Physical properties,1) Density and Specific Gravity 2) Viscosity Smell 3) Fluorescence 4) Color 5) Smell 6) Calorific Values,1) Density and Specific gravit

21、y,Oil density is usually less than 1000kg/m3, oil is lighter than water. But some crude oils, dense oils, can heavier than water, their density can larger than 1000kg/ m3 . To produce dense oil is very difficult.,Viscosity is an inverse measure of the ability of a substance(fluid) to flow. The great

22、er viscosity of a fluid, the more difficult it flows. Oil viscosity is generally dependent chiefly on the amount of gas dissolved in it and on the temperature.,2) Viscosity,3) Fluorescence,All oils exhibit more or less fluorescence, the aromatic oils are the most fluorescent. Fluorescent color of cr

23、ude oils can be yellow, green, or blue. Fluorescence must be observed under ultraviolet radiation. Fluorescence is used in well logging to locate oil showing in cores, cuttings, and drilling muds.,4) Color5) Smell6) Calorific Value,2 Natural Gases,2.1 Concepts 2.2 Chemical compositions 2.3 Physical

24、properties 2.4 About gas hydrate,2.1 Concepts,Petroleum gas, commonly called natural gas or hydrocarbon gas, consists of the lighter paraffin hydrocarbons, of which the most abundant is methane gas (CH4). In the oil industry, natural gas is defined as a mixture of hydrocarbons and varying quantities

25、 of non-hydrocarbcons that exists either in the gaseous phase or in solution with crude oil in underground reservoirs.,2.1 Concepts,Associated gas: the gas occurs with oil. Non-associated gas: the gas occurs alone. Aggregated gas: The gas in gas reservoir, Condensed gas. The gas in oil and gas reser

26、voir. Decentralized gas: The gas dissolved in oil, the gas dissolved in oil-field waters, the liquefied gas, the coal bed gas, and the methane hydrate.,2.2 Chemical compositions,1.Hydrocarbon gas: Methane/CH4, main composition of gas Ethane/C2H6, Propane/C3H8, takes various amounts in gas Butane/C4H

27、10 2. Non-hydrocarbon gas: N2, CO2, H2S, H2, CO, SO2, Hg, etc.,2.3 Physical properties,1 Density and specific gravity of natural gas Density means the weight of a given volume, such as kilograms per cubic meter. The density of a natural gas depends on its pressure (p), temperature (t), apparent mole

28、cular weight (m) and compressibility factor (z). Dg= 0.1196571pmg/(zt),The density of nature gas under the reservoir condition is larger than that of standard gas, usually 150 250kg/m3. The specific gravity of natural gas means the ratio of natural gas density to that of air (28.97). Also the ratio

29、of molecular weight of natural gas to that of air: rg=mg/28.97,2 The solubility,a. in water Henly formula: Q=C*P Q:solubility, C:solution coefficient, P: pressure. b. in crude oil the solubility depends on the pressure, temperature, composition of gas, the content of light HC in crude oils.,2.4 Abou

30、t the gas hydrate (Just for reference),Gas hydrates are crystalline compounds in which the ice structure of water is distorted to form cages that contain the gas molecules. The hydrates are solids resembling wet snow in appearance, and they form both above and below 0under specific pressure - temper

31、ature conditions. The water molecules form two kinds of unit cell structures.,The smaller unit structure contains 46 water molecules, which can hold up to 8 methane molecules. Gases such as CH4, C2H6, H2S, and CO2 can fit into this structure. The larger unit cell contains 136 molecules of water. Gas

32、es such as propane and iso-butane can fit into it. These are the only gaseous hydrocarbons that form hydrates. The pentanes and n-butane molecules are too large. A methane hydrate in which all the ice stages are completely filled with methane contains about 172 m3 CH4 of hydrate at STP. In nature th

33、e more typical ratio is 40 m3 CH4/m3 of hydrate. Natural hydrate units generally have six or seven H2O molecules per CH4 molecule.,The pressure-temperature diagram for methane and a 0.6 gravity gas (C1+C2+C3) is shown in Figure 7-8. Hydrates are formed by increasing pressures and are decomposed by i

34、ncreasing temperatures. Since the pressure required to form gas hydrates increases logarithmically as the temperatures increase linearly, it is apparent that the hydrates in most sedimentary basins decompose in the temperature ranging 70 to 80(21 to 27), because the pressures are inadequate to prese

35、rve them. Hydrate usually occurs in permafrost territory, polar region, and deep sea bottom sediments. It is estimated that there is very rich amount of hydrate around the world. But, now it is difficult to exploit hydrate in technical.,3 Oil-field Waters,3.1 Concepts 3.2 Source of oil-field waters

36、3.3 Chemical compositions and degree of mineralization 3.4 Classification,3.1 Concepts,Oil-field waters in general are termed brines. The water found in petroleum reservoir rocks is usually referred to as interstitial water, but it is improbable that the water which now exists in the pores of a rese

37、rvoir rock is the same water which was in the same group of pores at the time when the sediments were first laid down. The expressions bottom water meaning water underlying the oil and edge water“ means water lying down dip and therefore laterally with respect to the oil zone. Clearly, both terms ar

38、e concerned with the same body of water in a given reservoir rock. Also, top water, intermediary waters.,3.2 Source of oil-field waters,Sedimentation water: the water in which sediments were deposited. Infiltration water: the water that has fallen as rain water and has filled up the porous and perme

39、able rocks. Transform water: the water transformed from clay minerals or organic matters. Plutonic water: the water formed by magmatism or metamorphism.,3.3 Chemical composition and degree of mineralization,1 Inorganic: 6 kinds of ion: sodium(Na+)+potassium(k+), calcium(ca2+), magnessium(mg2+) chlor

40、ides(Cl-), sulfates(SO42-), bicarbonates(HCO3-)+carbonates(CO32-), and other trace elements.,3 positive ions,3 negative ions,2 Organic: HC, Phenols, salt of organic acid Indeed, it has been proposed that a lateral increase in the benzene content of the brine in a given stratum may point towards an oil accumulation in that stratum.,3 the gas dissolved in oil-field water,The degree of mineralization,Its also called concentr