Table of Contents
Source rocks are usually shales or limestones (sedimentary rocks). To be a productive source rock, the rock needs time to mature (time to form the oil and/or gas) and the hydrocarbons need to be able to migrate to a reservoir or seep. Marine rocks tend to form oil while terrestrial, or land, rocks tend to form gas.
Is shale a good reservoir rock?
Shale is a common type of tight reservoir that is composed of extremely fine-grained, sedimentary rock and may contain oil or natural gas – referred to as “shale oil” or “shale gas”.
Which rocks are proven to be good source rocks for hydrocarbon?
Possible source rocks are sedimentary rocks whose source potential has not yet been evaluated, but which may have generated and expelled hydrocarbons. Effective source rocks are sedimentary rocks, which have already generated and expelled hydrocarbons.
Is shale a reservoir or source rock?
Shale oil refers to the petroleum that remains in source rocks and has not undergone migration—a kind of fracture-pore oil deposit whose source rock and reservoir are the same.
What are the best source rocks?
Fine-grained, clay-rich sedimentary rocks including mudstone, shale (platy mudstone), marl (calcareous mudstone), limestone, and coaly rocks (especially for natural gas) are usually considered to be possible source rocks because coarse-grained sediments are too porous and permeable to retain organic matter.
Why was shale a poor reservoir rock?
Shale is a fine grained sedimentary rock composed of mud that may include clay minerals and organic material called kerogen. Unfortunately, due to the small size of these pores, the permeability of shale is about 9 orders of magnitude less than that of a conventional sandstone reservoir.
What is the best reservoir rock?
The best sandstone reservoirs are those that are composed mainly of quartz grains of sand size of nearly equal sizes or silica cement, with minimal fragmented particles. Sandstone reservoirs are generally 25 meters thick. Carbonate reservoir rocks.
How do you find the source of a rock?
To be a source rock, a rock must have three features: Quantity of organic matter. Quality capable of yielding moveable hydrocarbons. Thermal maturity.
How does oil escape from the source rock?
As the organic matter transforms into oil, this load-bearing kerogen turns into liquid. The fluid pressure of the oil within the black shales can become high enough to produce microfractures in the rock. Once the micro fractures form, the oil is squeezed out and the source rock collapses.
Which rock is the primary source of all other rocks?
Igneous rocks are primary rocks and other rocks (sedimentary and metamorphic) form from these primary rocks. Igneous rocks can be changed into metamorphic rocks.
What is shale oil vs crude oil?
The primary distinction between crude or conventional oil and shale oil is the way it collects. The oil in shale is typically found in smaller batches. As a result, shale oil often needs to be fractured so that the oil trapped within the shale can be recovered.
Does shale contain oil?
Oil-bearing shales are underground rock formations that contain trapped petroleum. The petroleum trapped within the rocks is known as “tight oil” and is difficult to extract. Companies extracting tight oil often use hydraulic fracturing (fracking), while companies extracting shale oil most often use heat.
What are the two most common types of reservoir rocks?
Reservoir rocks around the world is dominated by sedimentary rocks because generally it has primary porosity. Igneous and metamorphic rocks can be reservoir if there are in fracturing state (secondary porosity).
Can be a source rock for oil or natural gas?
A rock rich in organic matter which, if heated sufficiently, will generate oil or gas. Typical source rocks, usually shales or limestones, contain about 1% organic matter and at least 0.5% total organic carbon (TOC), although a rich source rock might have as much as 10% organic matter.
What is shale source rock?
Oil shale can be regarded as an organic-rich but immature source rock from which little or no oil has been generated and expelled. Subsurface source rock mapping methodologies make it possible to identify likely zones of petroleum occurrence in sedimentary basins as well as shale gas plays.
What is the difference between source rocks and reservoir rocks quizlet?
The movement of petroleum from a source rock to a reservoir rock. An impermeable rock above a reservoir rock that stops the further upward migration of petroleum. – Source rocks are formed from plankton which die and sink through the water column and accumulate on the seabed.
Is shale porous or nonporous?
Impermeable and/or non-porous materials include clay, shale, non-fractured igneous and metamorphic rocks. Porous/permeable layers are called aquifers; impermeable layers called aquicludes.
What is the difference between slate and shale?
When muddy sediments are buried and compacted for a long time, they form shale. When shale is buried deeper, for a longer time, and heated by the Earth’s crust, it forms slate.
Is shale a permeable rock?
Shales are characterized by very low porosity (typically less than 5%) and very low permeability (typically less than 1,000 nD), which make them challenging in recovering economically viable hydrocarbons.
What is the difference between source rocks and reservoir rocks?
Source rocks are usually a separate layer from the reservoir rock layers but occasionally they can be both source and reservoir. Source rocks are often offset from the reservoir, meaning that they are not directly below the reservoir but off to the side.
What two properties are needed for a rock to be a reservoir rock?
The two principal properties required from a rock to be a viable reservoir rock are porosity and permeability. Porosity is the capability of a rock to hold fluids in pores.
What is a good permeability for a reservoir?
The typical reservoir permeability range of 0.001 md (1 μD) to 0.1 md (100 μD) is considered.
What are the factors that promotes the preservation of source rock?
These factors are climate, sea-level changes, sedimentation rate, and surface paleoproductivity (Tyson, 1995(Tyson, , 2005 Katz, 2005) . In the present study, the types and abundances of organic matter was determined by microscopic analysis of the kerogen in transmitted and reflected light.
What rock types are typically good sources of oil and gas?
The types of rocks that contain oil and natural gas are all sedimentary rocks, rocks formed when grains and mineral particles deposited by running water fuse together.
Is Salt a cap rock?
A relatively impermeable rock, commonly shale, anhydrite, or salt, that forms a barrier or seal above and around reservoir rock so that fluids cannot migrate beyond the reservoir.
