Monday, September 16, 2019

Tight Oil

In addition, oil from tight sandstone and from shale formations is another type of crude oil which varies from a gas-condensate type liquid to a highly volatile liquid.

Tight oil refers to the oil preserved in tight sandstone or tight carbonate rocks with low matrix permeability- in these reservoirs, the individual wells generally have no natural productivity or their natural productivity is lower than the lower limit of industrial oil flow, but industrial oil production can be obtained under certain economic conditions and technical measures. Such measures include acid fracturing, multistage fracturing , horizontal wells, and multilateral wells. 

The term light tight oil is also used to describe oil from shale reservoirs and tight reservoirs because the crude oil produced from these formations is light crude oil. The term light crude oil refers to low-density petroleum that flows freely at room temperature and these light oils have a higher proportion of light hydrocarbon fractions resulting in higher API gravities (between 37 and 42 degrees) (Speight, 2014a). However, the crude oil contained in shale reservoirs and in tight reservoirs will not flow to the wellbore without assistance from advanced drilling (such as horizontal drilling) and fracturing (hydraulic fracturing) techniques. 

There has been a tendency to refer to this oil as shale oil. This terminolgy is incorrect insofar as it is confusing and the use of such terminology should be discouraged as illogical since shale oil has been the name given to the distillate produced from oil shale by thermal decomposition. 

There has been the recent (and logical) suggestion that shale oil can be referred to as kerogen oil (IEA, 2013).

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