ORIGIN AND PROPERTIES OF HYDROCARBON (cơ sở KHOA học địa CHẤT dầu KHÍ SLIDE TIẾNG ANH)

CHAPTER 1:

ORIGIN & PROPERTIES OF
HYDROCARBON


1. THE ORIGIN OF PETROLEUM HYDROCARBON
2. REQUIREMENTS FOR PETROLEUM
ACCUMULATION
3. PETROLEUM CHEMISTRY
4. PHYSICAL and CHEMICAL PROPERTIES OF
CRUDE OIL
5. CLASSIFICATION and OCCURRENCES OF
CRUDE OIL
6. ALTERATION OF CRUDE OIL
7. GAS PROPERTIES and CLASSIFICATION


THE ORIGIN OF
PETROLEUM HYDROCARBON
• THEORIES OF INORGANIC ORIGIN
– Hypothesis of Dimitri Mendeleev
– Hypothesis of Sokolof

• THEORY OF ORGANIC ORIGIN
• Analogy with organic matter
• Biomarker
• The present of porphyrins
• The polarization of ray-light
• Evidence of carbon isotopes

Requirements for Petroleum
Accumulation
The task of finding a petroleum field is not a simple one.
• First, there must be a rock containing original organic matter-a
source rock . Usually this is a mudrock or shale, which is a very
common rock type and makes up about 80% of the world's
sedimentary rock volume. However, even an average shale contains
only about 1% to 2% organic matter, and this number can vary
widely. Many shales have very low organic content and make poor
source rocks.
• Then, the source rock must be buried deeply so that temperature
and time can cause the organic matter to mature into petroleum.
This usually requires deposition into sedimentary basins, depressed
areas thickly filled by sediments. Our search for petroleum is further
limited, since over half of the world's continental areas and adjacent
marine shelves have sediment covers either too thin or absent.


Requirements for Petroleum
Accumulation (cont)
• Even where the organic matter can
become mature, not all of it becomes
petroleum. In a typical example (Figure 01
) a normal marine shale with only 1%
original organic matter will have less than
a third of it converted to the hydrocarbon
molecules that make up oil and natural
gas (Waples, 1981). The rest remains
behind as an insoluble organic residue.

Figure 01


Requirements for Petroleum Accumulation
(cont)

• Five factors, therefore, are the critical risks to
petroleum accumulation (Figure 02): (1) a mature
source rock, (2) a migration path connecting
source rock to reservoir rock, (3) a reservoir rock
that is both porous and permeable, (4) a trap, and
(5) an impermeable seal.
• If any one of these factors is missing or
inadequate, the prospect will be dry and the
exploration efort will be unrewarded. Not
surprisingly then, less than half of the world's
explored sedimentary basins have proved
productive, (Huf, 1980) and typically only a
fraction of 1% of the petroleum basin's area, and
at most 5% to 10%, is actually prospective
(Weeks, 1975).


Figure 02: Five factors for petroleum accumulation


PETROLEUM CHEMISTRY
• Strictly speaking, hydrocarbons are

compounds that contain only two
elements, hydrogen and carbon.
Consequently, petroleum is quite
simple in its elemental composition. It
contains relatively few impurities,
mainly atoms of nitrogen, sulfur, and
oxygen.


PETROLEUM CHEMISTRY
• Table 1, shows the average
composition of petroleum in all three
of its natural states of matter, as
natural gas, liquid crude oil and solid
or semi-solid asphalt.


AVERAGE COMPARISION OF CRUDE
OIL, NATURAL GAS, ASPHALT
Element Crude oil
Natural gas
% Weight

Asphalt

% Weight

Carbon
82.2 – 87.1
Hydrogen 11.7 – 14.7

Sulfur
0.1 – 5.5
Nitrogen
0.5 – 1.5
Oxygen
0.1 – 4.5
Table 01

80 – 85
8.5 – 11
2–8
0–2
-

% Weight
65 – 80
1 – 25
trace – 0.2
1 – 15


PHYSICAL AND CHEMICAL
PROPERTIES OF CRUDE OIL
• “A mixture of hydrocarbons that existed in the
liquid phase in natural underground reservoirs
and remains liquid at atmospheric pressure after
passing through surface separating facilities”
• Primary hydrocarbon molecules with a C/H ratio
usually 6 ữ 8;
ã Crude oil varies in chemical composition and

physical properties;
• Crude oil ranges in color from transparent
through colors of greenish – yellow, reddish, and
brown to typical black.


PHYSICAL AND CHEMICAL PROPERTIES OF
CRUDE OIL (Cont)
• Oil at the surface tends to be more viscous, most
oils are less dense than water: generally
measured as the diference between its density
and that of water
• The specific gravity of crude oil generally
ranges from 0.780 (500 API) to 1.000 (100 API);

141.5
°API =

- 131.5

SG 60/60°F

Thus, does light oils have API < 10° ???


• The U.S. Bureau of Mines defines
heavy oils as those with API gravities
of less than 25°, which is equivalent
to 0.9 relative density. When oil
reaches an API gravity of 10°, it has a

relative density of one, and the same
density as fresh water. However,
almost all oils are lighter than water


• Crude oil is not the only liquid
hydrocarbon which may be produced
from an underground reservoir. A
light, clear, high API gravity, liquid
called condensate, or sometimes
distillate, is often obtained in
association with natural gas
production


• Condensates begin as components of a
heavier gaseous phase in the subsurface
where they are highly compressed and at
elevated temperatures. This gas phase
contains some dissolved hydrocarbons
which, when brought to lower surface
temperatures and pressures, exolve.
• The subsurface phase then separates into
distinct gas and liquid phases, the latter
called condensate


The physical properties of oil & gas
Hydrocarbon: composed of H and C

Gases

Dry
methane

Liquid
Oil, Crude

Wet
ethane,
propane

Plastic
Asphalts,
Coals,
Kerogen


SPECIFIC GRAVITY OF OILS
• European Beaume’ scale;
• API scale (American Petroleum Institute)
API gravity
> 40
(ρ<0.825) Light crude oils
25 ÷ 40 (0.825÷ 0.904) Medium crude
oils
< 25
(ρ >0.904) Heavy crude oils
The relation between API gravity and density
API30

33
36
LPG
0.876 0.860
0.845
0.570


VISCOSITY (à) OF OILS
ã A measure of the internal resistance or
friction of a fluid to flow or stress/rate of
shear;
• The viscosity of crude oil depends on the
molecular composition of oil, the amount of
dissolved gas and temperature;
• Unit Measurement CSG – Centipoises, cP
• A drilling mud has a viscosity of about 15
cp., water at 200C has a viscosity of 1.005
cp., crude oil has a viscosity of 1 to 3 cP At
reservoir conditions.


CHEMICAL PROPERTIES OF CRUDE
OIL
• In terms of Its fundamental chemistry, oil
consists largely of carbon and hydrogen
with traces of oxygen, sulfur, nitrogen, and
a rather unusual range of metals which
includes vanadium, nickel, and others.
• Though the composition of oils is relatively

straightforward, the number of
hydrocarbon compounds which may be
present is immense, and no two oils are
exactly identical in their composition.


• There are four major groups of compounds
which are commonly present in crude oil (table 02).
• These are:
– The paraffins,
– The naphthenes,
– The aromatics, and
– The resins & asphaltenes.
• The resins and asphaltenes are not pure
hydrocarbons and include elements other than
hydrogen and carbon. The paraffins, naphthenes
and aromatics are pure hydrocarbons.


Four important HC series in petroleum chemistry
— the paraffins, naphthenes, aromatics, and
resins & asphaltenes

Table 02


• Of these pure hydrocarbons, the
paraffins and naphthenes are
collectively referred to as saturated
hydrocarbons, those in which there is

sufficient hydrogen to satisfy the
electron requirements of the carbon
atoms. The aromatic hydrocarbons
are unsaturated with respect to
Figure 2
hydrogen .


The diference between
saturated and unsaturated
hydrocarbons.

• Figure 03:


• In addition to these four major groups
of compounds, crude oil also contains
small amounts of other compounds
that contain sulfur, oxygen, and
nitrogen, as well as organometallic
compounds.
• When they occur in organic molecules,
atoms other than hydrogen and
carbon are often collectively called
heteroatoms. The compounds they
form are called heterocompounds