The document defines a petroleum play as a conceptual model that identifies locations where hydrocarbons may be found based on the combination of reservoir rocks, a source of hydrocarbons, sealing rocks, and a trap. The main components of a petroleum play are a source rock, migration pathway, reservoir rock, sealing rock, and trap. A petroleum play framework enables exploration for potential oil and gas deposits.

1. Concept of petroleum play |pɪˈtrəʊlɪəm |pleɪ|
What is the petroleum play?
A petroleum play is a conceptual model of how reservoir rocks, a petroleum
charge system, seal rocks and a petroleum trap may combine to create
petroleum accumulations at a specific stratigraphic level (Allen & Allen, 1990). It
enables exploration geologists to identify locations where hydrocarbons may be
found and extracted and to define parts of a sedimentary basin in which
petroleum could be trapped.
Components of the petroleum play
The physical components of a petroleum play include the petroleum charge
system (source rock and migration pathway), the reservoir, the seal and the
trap(Figure 1). These are described below:

2. Figure 1. The main components of the petroleum play.
(Figure by S.Ilott)

3. Petroleum charge system |pɪˈtrəʊlɪəm| |tʃɑːdʒ|
|ˈsɪstəm|
This component consists of the source rock for the hydrocarbons together
with the migration pathway (or route) of the hydrocarbons to the reservoir
rock.
• A source rock |sɔːs| |rɒk| is any rock which has produced (or will produce)
hydrocarbons. Source rocks are usually fine grained sedimentary rocks. Their
organic matter content is such that when they are buried and heated, the
organic matter will produce hydrocarbons. For example, deep marine shales
(black shales) or non-marine carbonates can all be source rocks if they
contain high amounts of organic matter.
• A sedimentary rock contains both rock derived inorganic sediments (i.e.
minerals) and biologically-derived organic matter (from plants and animals)
which has been buried as a sediment. The potential of a source rock to
generate petroleum is directly related to its volume, organic richness and
thermal maturity. A good source rock will contain between 5% and 20%
organic matter.

4. Migration pathway
|maɪˈɡreɪʃ(ə)n| |ˈpɑːθweɪ|

5. Reservoir rock |ˈrezəvwɑː| |rɒk|
Porous |ˈpɔːrəs| and permeable |ˈpɜːmɪəb(ə)l| rock in which
hydrocarbons can be stored and from which hydrocarbons can be
extracted.

6. Seal rock (cap |kæp| rock) |siːl||rɒk|
The existence of a petroleum play depends upon the presence of a seal
(also called a cap rock or a top |tɒp| seal). A seal is a fine grained rock
which prevents the oil migrating to the surface. The seal can be formed
by a fine grained sedimentary rock (such as a shale or mudstone) or by
evaporates /evaporaits/.
The cap rock prevents the hydrocarbons from migrating out of the
reservoir.

7. • Petroleum
trap|pɪˈtrəʊlɪəm||træp|
A term which is used to describe
the geometry of the sealed
petroleum- bearing container or
rock (which includes the seal and
the reservoir).

8. • Some other important terms which may be used when discussing a petroleum play are hydrocarbons,
petroleum, oil-water contact, lead, prospect and oil- window.
• Hydrocarbons |ˌhaɪdrəˈkɑːbənz| are naturally occurring organic compounds containing carbon
(C) and hydrogen (H). They can be gaseous, solid or liquid and include natural gas, bitumen and
petroleum.
• Petroleum |pɪˈtrəʊlɪəm| is a mixture of hydrocarbons and lesser quantities of organic
molecules containing sulfur, oxygen, nitrogen and some metals. Term includes both oil (liquid
petroleum) and hydrocarbon gas. Therefore, we will often use "petroleum" in these notes
instead of "hydrocarbons".
• Petroleum describes a compound that includes high concentrations of any of the following
substances:
• Thermal and biological hydrocarbon gas found in conventional reservoirs as well as in gas
hydrates, tight reservoirs, fractured shale, and coal
• Condensates |ˈkɒnd(ə)nseɪt|
• Crude oils |kruːd| |ɔɪl|
• Natural bitumen |ˈnætʃ(ə)r(ə)l| |ˈbɪtjʊmən| in reservoirs, generally in siliciclastic and carbonate
rocks

9. The oil-water contact |ɔɪl| -|ˈwɔːtə|
|ˈkɒntækt|
• The oil-water contact is a bounding surface in a reservoir above
which predominantly oil occurs and below which predominantly
water occurs. This is due to the different densities of the oil and the
water, the oil has more buoyancy, so it tends to float on top of the
water, and therefore, to appear higher within the reservoir than the
water.

10. The gas-oil contact|ɡæs| |ɔɪl| |ˈkɒntækt|
The gas-oil contact is a bounding surface in a reservoir above which
predominantly gas occurs and below which predominantly oil occurs. This is
due to the different densities of the gas and the oil, the gas has more
buoyancy, so it tends to float on top of the oil, and therefore, to appear
higher within the reservoir than the oil and known as a gas cap.

11. The gas-water contact |ɡæs| -|ˈwɔːtə|
|ˈkɒntækt|
The gas-water contact is a bounding surface in a reservoir above which
predominantly gas occurs and below which predominantly water occurs.
This is due to the different densities of the gas and the water, the gas has
more buoyancy, so it tends to float on top of the water, and therefore, to
appear higher within the reservoir than the water.

12. Original oil-water and current oil-water
contact
Water flooding

13. • A lead |liːd| is an indication or hint of the presence of a subsurface trap that gives
geologists a reason to explore further. A lead in hydrocarbon exploration, is a
subsurface structural or stratigraphic feature with the potential to have
entrapped oil or natural gas.
• A prospect |ˈprɒspekt| is an identified trap that has a good chance of containing a
reservoir rock, having suitable seals to trap any potential hydrocarbons, being on a
migration path, and also being present at the time that the petroleum was
migrating. It also must be of a sufficient size to warrant drilling. A prospect results
from the investigation of leads. Therefore, with a prospect we have a much higher
probability of finding hydrocarbons than with a lead. Once a prospect has been
drilled, it is no long a prospect, but becomes known as either a proven petroleum
field (a discovery) or a dry hole.

14. The oil window |ɔɪl| |ˈwɪndəʊ|
• The oil window is a temperature dependant interval in the subsurface
where oil is generated and expelled from the source rocks. The oil
window is often found in the 60-120 degree Celsius |ˈselsɪəs| interval
|ˈɪntəv(ə)l|(aprox. 2-4 km depth), while the corresponding gas window
|ɡæs| |ˈwɪndəʊ| is found in the 100-200+ degree Celsius interval (3-6
km depth).

15. Well /wel/
An oil well is a hole dug into the Earth that serves the purpose of
bringing oil or other hydrocarbons - such as natural gas - to the surface.
Oil wells almost always produce some natural gas and frequently
bring water up with the other petroleum products.
Types of Wells
There are numerous different ways that oil well can be drilled to maximize the
output of the well while minimizing other costs. The most common type of well
drilled today is known as a conventional well |kənˈvenʃ(ə)n(ə)l| . одинарная
скважина
Horizontal wells |hɒrɪˈzɒnt(ə)l| are an alternative type of well used when
conventional wells do not yield enough fuel ˈfjuːəl| . These wells are drilled and
steered to enter a deposit nearly horizontally. These wells can hit targets and
stimulate reservoirs in ways that a vertical well cannot.
Other types of wells include offshore wells |ˌɒfˈʃɔː| , which are wells that are
drilled in the water instead of onshore. These provide access to previous
inaccessible oil deposits. Multilateral wells |mʌltɪˈlæt(ə)r(ə)l| are wells used
occasionally that have several branches off of the main borehole that drain a
separate part of the reservoir.
Vertical Well‐ |ˈvɜːtɪk(ə)l| A hole drilled or bored vertically into the earth
usually cased with metal pipe for the production of oil or gas

16. Oil deposits |ɔɪl| |dɪˈpɒzɪts|
• reserves of petroleum found underground or under the
sea.
• A deposit is an area in the earth’s crust where solid or
gaseous resources are found in a high natural
concentration.
If extraction of the deposit is worthwhile, it is referred
to as a workable deposit.
If extraction of the deposit is worthwhile in the future, it
is referred to as a usable deposit.
• Deposits contain resources such as natural gas
|ˈnætʃ(ə)r(ə)l| |ɡæs|, crude oil |kruːd| |ɔɪl|,
coal |kəʊl|, ore |ɔː|, salt |sɔːlt|, stone |stəʊn| and
other minerals |ˈʌðə| |ˈmɪn(ə)r(ə)lz|.

17. Oil field
• Definition of oil field
• A region rich in petroleum deposits