Open Journal of Applied Sciences, 2012, 2, 66-69
doi:10.4236/ojapps.2012.22008 Published Online June 2012 (
Development of Radio Fre quency Heating Technology for
Shale Oil Extraction
Yi Pan, Can Chen, Shuangchun Yang, Guiyang Ma
Liaoning Shihua University, Fushun, China
Received February 20, 2012; revised March 18, 2012; accepted March 22, 2012
With the shortage of energy and the rise of crude oil in the world, the development of oil shale is gaining more attention
globally. To solve the problem of traditional heat conduction with low efficiency and high cost for oil shale, a new
technology called radio frequency (RF) heating (microwave heating) is introduced in this paper. Radio frequency elec-
tromagnetic (microwave) can do work directly on medium molecule of oil shale and change into heat energy, the trans-
mission of which allows both inner and outer molecules heating simultaneously without heat conduction. Meanwhile,
oil shale is a poor microwave absorbing material and microwave absorbents must be added to reach pyrolysis tempera-
ture. By this means, shale oil could be heated at a higher speed and kerogen will gradually be cracked into gas and oil.
Then shale o il and gas will flow into the p roduction wells through fractures generated by heating and be pumped up to
the surface.
Keywords: Oil Shale; Shale Oil; Radio Frequency Heating; Microwave
1. Introduction
Oil shale is a significant fossil resource with substantial
reserves, which is as high as 400 billion if all be converted
into shale oil ,and it is equivalent to 5.4 times of the
world’s proven crude oil [1,2] .China is one of the richest
countries in oil shale resources over the world, with
31.567 billion tons of proven oil shale reserves, which
mainly distributes in MaoMing, HuaDian, FuShun, etc.,
ranking the fourth followed by America, Estonia and Bra-
zil in the world [3,4]. As a potential important resource,
many of the world’s companies have been working o n th e
research and development of the shale oil. In a report of
the US Department of Energy, it is confirmed that more
than thirty American enterprises actively involved in the
project of the oil shale. With the world’s energy demands
growing, it’s worthwhile seeking for the effective devel-
opment and economic utilization.
Oil shale, which mainly composed of mineral and kero-
gen, is a kind of low permeability rock. Kerogen is the
parent material of oil and natural gas. Although the
world has a large oil shale reserves, a large portion of
which is buried relatively deep (under 500 m). So, the
open and tunnel retorting system can’t be utilized. Only
by means of heating the oil shale formation, the shale oil
can be extracted effectively, which is commonly called
in-situ retorting technique. Currently, three heating meth-
ods have been adopted, namely conduction heating, con-
vection heating and radiation heating respectively. Com-
pared with the first two means which need long retorting
time and have low extraction rate [5], the microwave
heating can greatly make up for the deficiencies.
2. Microwave Heating of Oil Shale
2.1. Priciples
Microwave has dielectric thermal effect on materials, by
which the migration of ion and the rotary of polarity
molecules that make the molecules moving. That is, the
relatively static transient of polarity molecules changes
into dynamic and produces thermal effect by the dipolar
high-speed rotating of molecules. The change happens in
the inner part of the rolled substance that is internal
heating. For oil shale is a poor conductor of heat, the
utilization of conduction heating and convection heating
will lead to low speed. While the adoption of radio fre-
quency heating overcome the difficulties of heating un-
derground oil shale, which makes the retorting easier and
more effectively.
2.2. Mining Process
Lay nine wells in the single level oil sh ale seam, with the
thickness of 40 m and the buried depth of 300 m. Well 4
to well 9 locate on the intersection of squares with the
distance of 16 m, showing a positive hexagon grid distri-
Copyright © 2012 SciRes. OJAppS
Y. PAN ET AL. 67
bution. Well 1 to well 3 are heatin g wells, the distan ce of
which is 3 m (Ordinarily, the distance between wells is
designed as the frequency of wave. The higher the fre-
quency, the shorter the distance will be. The lower the
frequency, the longer the distance between wells [6].)
and drill each well into seam 10 .Then place a micro-
wave generator in well 2 and radiate microwave to heat oil
shale formation as the predetermined direction (See Fig-
ures 1 and 2). Detailed steps are introduced as follows:
Dill pinnate well 1 and 3 in the upper and lower seam
of oil shale respectively and inject microwave absor-
bents, forming symmetrical microwave absorbing sur-
Drill horizontal well 2 that radiate microwave and
perforate 20 holes at the wall of cased hole. Thus two
pinnate wells and a horizontal well make a heating
well group.
Drill vertical well 4 to 9 as producing wells.
Turn on the microwave generator and radiate micro-
wave under the power of 1700 kw. Oil and gas will
be extracted through producing wells after 60 days of
pyrolysis of oil shale formation. To guarantee that the
underground oil and gas will flow in gas phase, the
power of microwave generator and the closing time
of producing wells can be adjusted to control the un-
Figure 1. Well n e twork layout of microwave heating .
Figure 2. Well network profile of microwave heating.
derground pressure and temperature. When fluids ex-
ist in gas phase and the temperature of released oil
and gas is below 200 centigrade, oil and gas can be con-
tinuously release d and g et se para ted on the ground.
Later in the retorting process, turn off the microwave
generator and convert pinnate wells and horizontal
wells into injection wells when little oil and gas flow
out of the producing wells. Inject cold water, drive the
residual oil and gas, also it will lower the temperature
of subsurface formation. The cold water heated by the
subsurface stratum is recovered through other wells,
which can be used another well network after disposi-
tion [7].
2.3. Technique Characteristics
Three ways can be adopted to transfer the heat to oil shale,
namely conduction heating, convection heating and ra-
diation heating [8]. Compared with other heating tech-
niques, microwave heating technique has advantages of
strong penetration, high heating speed and efficiency,
Real-Time heating, integrity, etc.
The Real-time represents it heats rapidly when taking
microwave to heat materials. Microwave radiation
promote polarity molecules to move severely, making
molecules collide and rub. The heating process takes
place in the whole object simultaneously with quick-
ness in temperature rise, temperature uniformity and
low temperature gradient.
The high efficiency of energy consumption mainly
reflects that medium materials can absorb microwave
and change it into heat energy directly. Microwave
heating requires no heat conduction.
Microwave heating has good selectivity, and it can
play different roles in different materials. With turning
off the microwave source, microwave energy is un-
available, which can control the temperature of oil
shale accurately.
The crack of oil shale by microwave heating will in-
crease the fractures, which contributes to the trans-
mission of microwave in oil sh ale, expanding heating
area and the discharge.
Heating shale oil by microwave, heating rate can be
easily adjusted. Conventional methods require a quite
long time to reach the predetermined temperature and
longer cooling time when stop heating. With micro-
wave heating process, the status of oil shale will change
as the output power of microwave regulated.
3. The Present Situation of Radio Frequency
3.1. RF/CF Technology Introduction of
As the expert in RF field, Raytheon has made a perfect
Copyright © 2012 SciRes. OJAppS
combination of his RF and CF which is from Hyde Park,
the other expert in CF field. By this in-situ technology,
oil shale is heated by CF, and critical CO2 drives the liq-
uid and gas out (as shown in Figure 3).
3.1.1. Proces s In troduction
RF/CF is a patent technology that combined radio fre-
quency heating and critical liquid driving [9]. The oil in-
dustry equipment drills and sends radio frequency an-
tenna or transmitter to the oil shale. The ray energy from
antenna or transmitter heats the oil shale, and critical
CO2 drives the oil to well, then the oil is pumped to
ground to condensate and storage. The CO2 is separated
and pumped to well to use again.
3.1.2. Process Ch aracteristics
The RF heating rate is quick through the volumetric
heating mode or selective heating mode. The process can
be controlled automatically and all the heating process
will not pollute environment. Development prospect of
RF/CF technology is bright du e to the advantages as fol-
High oil recovery rate . By usi ng R F/C F technology , 4 -
5 units power is produced by consuming 1 unit power.
It has higher economic benefits than ICP technology
(In-situ Retorting Technology), which produces 3.5
units powe r by cons uming 1 unit powe r.
The oil industry equipment is used to drill oil well in
oil shale. RF antenna or transmitter is sent down to
the underground and emits ray to heat the oil shale.
Crude oil is extracted and driven to well by injecting
critical CO2.
CO2 is separated and reinjected into well to recycle
using. At the same time, oil and gas can be refined to
gasoline, fuel oil and other p ro duct s.
Figure 3. Process of RF/CF technology.
Oil and gas can be extracted in only few months, it is
quicker that the other in-situ technology, which may
need many years.
The heating power can be adjust easily, and will pro-
vide a great variety of the products.
This technology can be u sed in the extr action of shale
oil, sand oil and heavy oil, and it has no residual and
will not pollute the groundwater.
Selective heating mode. It will heat the specified field
quickly to the aim temperature.
However, amounts of greenhouse gas will be inevitably
produced in the process of shale oil extraction, such as
CO2. Raytheon has done a lot of work in the field of CO2
isolation and made some achievements. At present Ray-
theon has obtained the patent of CO2 isolation technol-
ogy for RF/CF process [10,11]. For the traditional isola-
tion technology, the isolation effects will affected by
permeability, storage capacity, space size, temperature
and so on. RF/CF technology has avoided these problems
by using a closed injection-isolation system. The extrac-
tion mode will not discharge any CO2. The RF/CF tech-
nology needs lots of energy to get the radio frequency
weave, elec tric power is the orig inal choice, but it is expen-
sive, so Raytheon has began to research the using of alter-
native sources, such wind energy and solar energy. The
research work will build a firm foundation for the RF/CF
technology application in the extraction of shale oil.
3.2. RF Technology Introduction of LLNL
The RF heating technology has been researched by Amer-
ica Illinois Institute of Technology in the late of 1970s.
Vertical combination electrode was used to heat the shale
slowly. It needs lots of time to diffuse the heat by con-
duction. To avoid this defect, LLNL used radio fre-
quency to heat the shale. The RF has a strong penetrating
power and can be controlled easily (see Figure 4).
Figure 4. Process of LLNL technology.
Copyright © 2012 SciRes. OJAppS
Copyright © 2012 SciRes. OJAppS
4. Conclusions
In a word, the reserve of oil shale is abundant and its
distribution is concentrated, maybe it will become the
succession energy. The RF technology plays a main pole
in the research of shale oil extraction, and has a bright
application future. The bottleneck problem for RF de-
velopment is the power consumption. Because a lot of
electric power is used to get microwave, the cost of tech-
nology applying is higher. Generally, it needs one micro-
wave generator for every heating well, but it will in-
crease the cost also. The location of generator in well is
important. It is still a question now for how to locate the
generator, in order to get the longest effective distance
and highest utilization efficiency.
The shale oil and gas is a good fuel for boiler, and it can
be used to generate electricity. It is a circulation process
to use one part of shale oil to generate electricity and
then to generate microwave. How to build the circulation
in shale oil extractio n is a new task.
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