By Е.I. Кrаpivsky, V. O. Nekoutchaev, V.N. Ryzhakov
At production and processing of petroleum, gas and condensate
the radioactive slimes are depos-ited from stratal waters ,
their specific radio-activity reaching 1000 кBq/kg. The
radioactive salts and slimes are also deposited on the
petroleum and gas equipment (pumps, pipes, compressors etc.).
In the USA, according to doctor Grey P. R., more than 10
million tons of radioactive slimes are stored. The quantity of
radioactive stratal water slimes in Russia exceeds 50 million
tons, and many of them are treated as radioactive wastes.
Numerous cases of returning used radioactive pipes and
equipment from enterprises are known because of their high
radio-activity. Stored radioactive wastes bring harm to an
environment and population. In recent years the problem of
decontamination of radioactive slimes has been intensively
discussed in different papers. However, only few authors offer
the ways of practical solution to this problem .
Physial-geological preconditions of radioactive pollution of
oil and gas fields
It is now commonly accepted that the main source of oil- and
gas fields pollution by natural radionu-clids is stratal
water. The radioactive isotopes Ra-226 and Ra-228 are revealed
in the majority of stratal water tests of petroleum and gas
deposits. Increased concentration of radium is found in
phos-phorites, loam, organic substance, zeolite, mylonite,
radium - barite or witherite, nonsylfate of cloride solutions.
Modern sediments of radium are discovered in layered
aluminosilicate (kaolin, hydro of mica, montmorillonite),
phosphorite, organic substance, hydroxides of iron, loams.
Geochemistry of the behavior of radioactive elements (uranium,
radium, thorium, their products of disintegration and
potassium-40) in stratal waters of petroleum and gas deposits
is investigated in-sufficiently. In the Komi Republic (
Russia) the basic radioactive isotopes are Ra-226 and products
of radon disintegration . In some tests the presence of the
product of thorium disintegration - radium -228 is found. The
contribution of potassium in total radio-activity of slimes
and stratal waters, as a rule, is insignificant.
Ra is similar to Ва in chemical properties. Sulphate RaSO4,
carbonate RaCO3, oxalate RaC2O4, phosphate Ra3(PO4)2, chromate
RaCrO4, iodate Ra (JO3)2 – are weakly soluble salts. Bromide,
chlo-ride and nitrate of radium quite well soluble in water. A
product of radium disintegration is radon. Products of radon
disintegration are basic gamma emitters of uran-radium
radioactive series. In stratal waters and radioactive slimes
increased concentration of barium, cerium, phosphorus,
strontium and plumbum have been found. Total mineralisation of
stratal waters is about 100 g/l.
There are six sources of radioactive pollution typical for oil
and gas- condensate enterprises.
-
Installation of methanol regeneration. A specific
radio-activity of slimes is low - up to 1-2 кBq/kg. Slime, as
a rule, does not contain paraffin substances.
-
Steel tanks for storage of methanol stratal water.
Petroleum slimes are non-uniformly deposited at the bottom of
tank. After steaming of the tank by superheated steam this
deposit mixes up with paraffin substances, whose quantity may
reach 50 % of slimes volume. As a rule, the average specific
activity of slimes and paraffin mix does not exceed 10 кBq/kg.
-
Oil traps of refining works. The radio-activity of slimes
can reach 30 кBq/kg. Practically there is no paraffin in
slimes. Basically it contains hard soluble salts of radium
(radium barite, radium tiff). Slimes are also accumulated in
reservoirs of secondary settling and sand traps, in pond sump,
concrete troughs.
-
Deposits of salts on internal surface of pipelines and
equipment for production of petroleum and gas. Specific
radio-activity of salts reaches 30 кBq/kg. Laboratory
researches have shown, that these depos-its, containing radium
barite and radium – tiff are not readily soluble even in a
hydrochloric, sulfuric and acetic acid.
-
High radio-active slimes previously discarded on the
ground. It is one of the main sources of eco-logical danger in
oil- and gas fields.
-
Slime deposits in reservoirs for settling gas condensate
may be considered the sixth source of ra-dio-activity.
Decontamination
of radioactive slimes on the territory of a gas - condensate
enterprise
The basic purpose of the developed technology is the reduction
of quantity of slimes with the increased radio-activity stored
on the territory of a gas-condensate enterprise. The basis of
the technol-ogy is dissolution and lixiviation of radium. It
is divided into some parts:
-
research of a radio-activity of
slimes in settling reservoirs by a radiometric method based
on a differ-ential methodics and its selective removal;
research of slimes radio-activity in oil trap and its
selective or complete removal;
-
allocation of slimes in special
containers for temporary storage; determination of slimes
specific ac-tivity; determination of slimes structure by
X-ray radiometer method; placing of the container with
slimes in technological tank;
-
determination of slimes specific
activity in technological reservoir by differential
methodics;
-
addition of reagents (salts of
natrium, barium, cerium) for increasing of decontamination
efficiency; processing of slimes by the steam from mobile or
stationary steam generator ; removal paraffin sub-stances
and determination of their specific activity by alfa, beta
and gamma - radiation; burning of par-affin substances;
-
drain of radioactive liquid in
intermediate reservoir, determination of its specific
activity; dilution of technological liquid in intermediate
reservoir up to a level of specific activity lower than 0,1
кBq/kg; a compulsory filtration of a radioactive liquid
through sand or zeolite filter; determination of specific
activity of the filter;
-
removal of technological water
into refining works, its dilution up to a level less than
0,1 kBq/l; de-termination of a specific radio-activity of a
liquid in refining works, and returning of liquid in wells
to the depth of 3700 m; control of a specific radio-activity
of a seam in a well based on the data of gamma - logging;
-
adding acid for lixiviation and
dissolution of radium and its salts to slimes remaining
after steaming, control of a specific radio-activity of
slime and solution;
-
repeated steaming of slimes with
acid and reagents to prevent from coprecipitation and
pollution of the surface of the technological equipment;
control of a specific slimes radio-activity and
technological solution by alfa, beta and gamma - radiation,
definition of barium, cerium and lead concentration in
slimes by roentgen-radiometric method; the control of a
specific radio-activity of acidiferous solution and its
preliminary dilution up to a level lower than 0,1 кBq/kg;
-
washing of slimes with hot water
with reagent as long as neutral or weakly acid reaction
takes place, control of slimes specific radio-activity;
-
moving of slimes to the gas
furnace for annealing of paraffin substances; burning of
slimes together with paraffin and coke;
-
repeated processing of annealed
slimes by acid and steam, its washing; the control of a
specific radio-activity of annealed slimes by alfa, beta and
gamma - radiation;
-
dilution of slimes by
nonradioactive sand or sandy loam up to a level of a
specific radio-activity lower than 1,5 кBq/kg; storage or
utilization of slimes, monitoring of radioecological
situation on all objects of warehousing and using diluted
slime and its moving.
For slimes from oil trap the
sequence of operations is similar. The operation of burning
and cal-cination should precede other technological operations
if possible.
The cost of decontamination of
radioactive slimes for northern areas of Russia does not
exceed 150 dollars per ton.
Conclusion
-
The geochemistry of radium
behaviour in stratal waters of petroleum and gas deposits of
the north-ern regions of Russia has been investigated.
Radiochemical situation on the territory of oil- and gas
fields has been studied. It is shown, that the basic sources
of radioactive pollution of oil and gas fields are stratal
waters with the increased concentration of radium-226 and
radium-228.
-
The theoretical and methodical
bases for the control and management of processes of
radioactive slimes decontamination have been created. The
requirements to the equipment for management of
de-contamination processes are proved.
-
The experimental industrial
installation for decontamination of slimes with the
increased radioactiv-ity with productivity of 2000 tons per
year and the bases of decontamination technology have been
cre-ated. The project of ecologically safe installation has
been developed.
-
The new detectors of alfa-, beta-
and gamma - radiations, the techniques for measurement of
spe-cific activity of radium disintegration products have
been developed; the methodics of radiation con-trol and
ecological monitoring of an environment is proved.
-
In industrial conditions the
influence of processes of lixiviation, dissolution,
deemanation, sorbtion, thermal and high-temperature
processing on decontamination of the large volumes of slimes
with in-creased radio-activity has been investigated. To the
best of the authors knowledge the technology has no Russian
or foreign analogues.
-
It is proved, that as a result of
decontamination of slimes with a specific radio-activity up
to 100 кBq/kg the solid insoluble final product can have
specific activity no more than 1,5 кBq/kg, and liquid final
product - less than 1 Bq/l. The liquid product of
decontamination is pumped to depth 3700 m and mixes up with
natural stratal waters, whose radio-activity is tens times
as high and reaches 100 Bq/l.
-
For the first time new ways of
reduction of quantity and specific activity of petroleum
slimes in oil traps and settling reservoir are offered and
checked up. The way of transformation of insoluble radium
minerals to soluble forms has been developed.
We think this work has practical
meaning not only for the Russian Federation, where about
several hundred thousands tons of slimes per year are formed
in oil and gas fields, many of which have increased
radio-activity, but it can also be important for oil- and gas
producting foreign countries. Basic results of that work and
technological methodics can be used for decontamination of
radioactive soils and sediments. Rather low cost of
decontamination of soils and slimes allows to use technology
in commercial scale.
References:
1. Nikiforov Yu.A. Radioactive
pollution of an environment at oil extracting on an example of
the Stavropol deposits. Russian geophysical magazine, №3,
1994, P. 81-84.
2.. Krapivsky E.I., Smirnov Yu.G.
Ruzakov V.N. Decontamination of radioactive ground and
petro-leum slime on the basis of radiometric sorting and
management of technological process. Russian geo-physical
magazine. 2001. № 21-22. P. 96-105
3. Grey P.R. NORM Contamination
in the Petroleum Industry.Journal of Petroleum Technology.
1993. vol.45. № 1. P.12 - 16.
Authors:
Krapivsky E.I. - professor of
physics dep. of Ukhta State Technical University. Adress:
Pervomayskaya 13, Ukhta, Komi Republic, Russia 169300. Phone
(82147) 3-67-49
E-mail:
nekouch@uii.sever.ru
Nekoutchaev V.O. - head of
physics dep. of Ukhta State Technical University, professor
Adress: Per-vomayskaya 13, Ukhta, Komi Republic, Russia
169300. Phone (82147) 3-67-49
E-mail:
nekouch@uii.sever.ru
Ryzhakov V.N. - director of
Vuktyl board "Severgasprom", Vuktyl, VGPU, Komi Republic,
Russia 169400
E-mail:
nekouch@uii.sever.ru
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