Reservoir rock:

 A permeable subsurface rock that contains petroleum. Must be both porous and permeable.


​Reservoir rocks are dominantly sedimentary (sandstones and carbonates); however, highly fractured igneous and metamorphic rocks have been known to produce hydrocarbons, albeit on a much smaller scale
The three sedimentary rock types most frequently encountered in oil fields are shales, sandstones, and carbonates
 
Each of these rock types has a characteristic composition and texture that is a direct result of depositional environment and post-depositional (diagenetic) processes (i.e., cementation, etc.)

Source rock: ​

A sedimentary rock in which petroleum forms. They are widely agreed to be sedimentary rocks.


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The ​RESERVOIR ROCK is the container of oil and gas underground
Understanding reservoir rock properties and their associated characteristics is crucial in developing a prospect  ​
Find out more about:

SHALES

Shales are able to be Source rocks and Seals
​Description
Shales are dark-brown to black or dark gray in color with smooth lateral surfaces (normal to depositional direction)
Properties
​Composed of clay and silt-sized particles
Can be excellent seals because of its low permeability
Can be main source of hydrocarbons if its original composition has rich organic components
Place
​Deposited on river floodplains, deep oceans, lakes or lagoons

SANDSTONES

Can be sandstone reservoirs
​Description
Composed of sand-sized particles
Typically light beige to tan in color, can also be dark brown to rusty red
Properties
​Sandstone porosity is between 10-30%
​Intergranular porosity is largely determined by sorting (primary porosity)
Place
​Sandstones are deposited in a number of different environments. These can include deserts (e.g., wind-blown sands, i.e., eolian), stream valleys (e.g., alluvial/fluvial), and coastal/transitional environments (e.g., beach sands, barrier islands, deltas, turbidites) 

CARBONATES

Can be Carbonates reservoirs
​Description
Grains/clasts are the skeletal or shell remains varying in size and shape
These clasts can be used to identify the age of the reservoir using the method as indicating fossil’s age
Usually light or dark gray, abundant fossil molds and casts, vuggy porosity
Properties
Porosity is largely a result from dissolution and fracturing(secondary porosity)
Carbonates such as coquina are nearly 100% fossil fragments
Susceptible to dissolution weathering
Place
Shallow marine depositional environments (lagoons, etc.)
Classification
Dolomites(calcium magnesium carbonate CaMg(Co3)2)
Limestones (Mudstones, Wackestones,Packstones, Grainstones, and Boundstones)