Nonconventional Reservoir fluids
Author Xuxun Huang     Editor Poomisant Srimaharaja

Unconventional resources
After the beginning of modern technologies and high oil prices in the past ten years, many countries have used the new method to produce from unconventional resources that were harder to produce than the conventional resources. Unconventional resources consist of Oil Sands, Extra-heavy Oil, Shale Oil or Tight Oil, Oil Shale, Shale Gas, and Coal-bed Methane.
Therefore, we will talk about this important topic in any kind of unconventional resources.
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Oil sand
Oil sand is a mix of sand, water, mud and bitumen which is solid or semi-solid at room temperature and therefore can’t move. Moreover, bitumen is a portion of high density oil. Canada is the country with the largest oil sand resources in the world and has a reserve of more than 5 thousand million barrels at present.
We can produce oil sands by two ways which are mining and in-situ. We will specific in in-situ that inject the heat deep into the ground by the horizontal well injector to reduce viscosity of bitumen so it can flow into the producer well which is shown in the second picture below.
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Oil Sand
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Oil production from Oil Sand.
​Extra-Heavy Oil
First, Let's talk about the physical properties of extra-heavy oil. Extra-heavy oil has lower viscosity than bitumen and can flow better with higher temperature in extra-heavy oil reservoirs compared to oil sand reservoirs. Extra-heavy oil has been found mostly in Venezuela. For extra-heavy oil we don’t use the heat to increase oil recovery but we use low temperature production first and follow with enhanced recovery such as injection of heat and chemicals.
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Extra-Heavy oil is very viscous.
​Shale Oil or Tight Oil
Shale oil or Tight oil is crude oil located in shale or any low permeability rock. Shale oil just has been produced recently which began in USA by using the new technology called horizontal well and multi-stage hydraulic fracturing in 2008. That is one of the reasons of decreasing oil prices in the present because USA will not need to import oil anymore. Moreover, USA can also export the oil to other countries. However, these methods will help the petroleum flow into the well easier. As the exploration research shows that USA has the most shale oil in the world which has reserves more than twenty-four thousand million barrels.
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Hydraulic fracturing for production from Shale oil.
​Oil Shale
Oil Shale is a shale rock which is rich in kerogens, solid and used to be a fossil before changing into crude oil or gas. Therefore, we will talk about the difference of Shale Oil and Oil Shale.
Oil Shale is the shale that has oil or kerogens and Shale Oil is the oil that is inside the Shale or the impermeability rock.
Oil Shale has been found for a long time and abundant in the US that almost 77% of oil shale in the world is located USA.
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Oil Shale
Shale Gas
Shale gas is one kind of natural gas that is located in shale. There are many properties. The important properties is viscosity. Shale gas production must use different recovery processes from normal gas. Nowadays we usually produce shale gas by hydraulic fracturing methods to create more space in the formation that will let the gas move into the horizontal well. China, USA, Argentina, Mexico, South Africa and others have a lot of shale gas which the most is China.
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Oil shale mining production in 2010 from many countries.
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Shale gas production and prediction of shale gas.
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Shale gas production
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Location of Shale gas in many countries around the world.
​Coalbed Methane
Coalbed methane is methane that is located in coal by adsorbing on the rock surface. Moreover, coalbed methane(CMB) consists of high methane and little of other gas.  Some of CBM has 96% of methane and 3.5% of nitrogen. We separate types of coalbed methane by percentage of methane.
Low grade coalbed methane has low methane in rock including of peat, lignite. All of these is biogenic methane, this methane was created by bacteria.
Middle grade coalbed methane, highest volume of methane, such as bituminous. Moreover, this middle grade coalbed methane is methane that is derived thermally. And we called this method coalification.
High grade coalbed methane, includinganthracite, has lower methane than bituminous. So we will focus on middle coalbed methane first.
Coalbed methane is produced by vertical well or horizontal well. However, it depends on the characteristic of the reservoirs combining with hydraulic fracturing methods.
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The production of coalbed methane.
​Gas hydrate
Another name of gas hydrate is methane hydrate and it is a form of crystal formation such that methane is covered by this crystal formation. And we can find the gas hydrate only in the cold place such as arctic, permafrost or ocean. Moreover, it must have the suitable pressure and temperature to create this form of crystal.
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Gas hydrate in permafrost and ocean area.
This video can explain the difference of conventional and unconventional reservoir fluids.


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References
energy.gov
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