What causes these radon anomalies? Some possibilities:
- Reports listed in the annotated bibliography (below) describe the success of surface and airborne radiometric surveys in
exploration for oil and gas.
Most of these papers refer to gamma radiation, but some refer to radon.
Radon geochemistry can be more sensitive than gamma, because it is based on alpha radiation
which has a lower background count.
Our Lucas cells provide radon-thoron ratios, which are more sensitive still.
These ratios have been successful in uranium exploration and
should prove useful in oil and gas exploration as well.
We have a formula to resolve radon from thoron giving on-the-spot results with our field instruments.
Like all exploration methods, radon and thoron geochemistry will benefit from a thorough
understanding of the geological setting of the reservoir.
Upward migrating non aqueous-phase formation fluids
Upward migrating aqueous-phase formation fluids (formation water)
Radon geochemistry in soil gas and groundwater has been widely used by environmental
scientists in the search for hydrocarbon contamination (NAPL or non aqueous-phase liquids).
Radon has an affinity for organic liquids, and in the presence of NAPL the radon concentration in groundwater or soil
gas is reduced due to partitioning into the organic NAPL phase.
This results in lower radon values over hydrocarbon contamination and we expect similar low values over natural
hydrocarbon sources such as a reservoir or reservoir edge.
Matolin et al. (see annotated bibliography below) noted increased levels of radon and thoron over an oil
productive zone, which they attribute to enhanced radon gas
emanation from U- and Th-bearing minerals decomposed by hydrocarbon-generated groundwater
acids ("enhanced emanation power").
Fractures and shale gas
Aqueous-phase formation fluids
can carry upward dissolved members of the uranium decay series (radium etc.), which are leached out
of formations with normal background levels. These elements are then deposited near surface.
Near surface enrichments of radium result in recognizable anomalies of radon and possibly
Our radon-thoron ratios allow us to correct for local variability in soil
permeability and weather conditions.
The impermeable structure which traps the oil and gas into a commercial reservoir can deflect
the upward migration path of these formation fluids, resulting in a recognizable pattern of radon and gamma
radioactivity at surface.
In this case we can expect a concentration above the field boundary, ideally in the form of a halo or part halo.
Another possible cause of radon anomalies over reservoir edges is the development of fractures
due to differential compaction, resulting in
increased permeability. This process, in the case of reef structures, is described by
Sikka and Shives, 2002 (see annotated bibliography below).
Click here for annotated bibliography
Ghahremani (see below) hypothesized that shale gas yields will be optimized where natural fracturing of
the shales is greatest, and that such fracturing will allow radon to migrate to surface causing radon anomalies in
We measure: radon - radium - thoron - radon daughters - alpha radiation.
is recognized as the most sensitive and reliable method for these elements.
Our instruments are used around the world in exploration for uranium, oil & gas, groundwater and hydrothermal,
and in environmental protection, health physics, earthquake prediction, and evaluation of hydrocarbon and NAPL contamination.
In the radon business since 1968, our latest major instrument update was 2015.
Modern, low-power, field-rugged electronics. Some earlier versions still working after 35 years.
Continuous real-time monitoring and data recording.
Winter and summer, from the Sahara Desert to the Canadian Shield, our instruments have faced up to severe field conditions.
- Intrinsically safe functions.
Sensitive to geochemical trace levels necessary for radon in lake water and for radon-thoron isotope ratios.
Can work in a tent without electricity or be carried from point to point in the field.
50 readings per day. Results available immediately.
Rechargeable battery pack good for a long day in the field and recharges in a few hours.
Can be operated by junior personnel if carefully supervised.
Same instruments used for radon and radium in soil, sediment,
plant parts, rocks, water, soil gas, air, and snow, and for radon daughters in air.
- EPA compliant.
Click here for more details of instruments.
Click here for or other instruments, components and
accessories we provide
Technical specification sheets and pictures of our instruments provided on request.
Multilingual consulting and training (if required).
For instruments contact|
R.H. Morse & Associates Ltd.
Robert H. Morse, Ph.D., P.Eng.
April 15, 2011