COMPLETE SPECIFICATION
DE.SORPTION APPARATUS FOR ADSORBED ANALYSIS OF THE SOIL
SAMPLES FOR SURFACE GEOCHEMICAL EXPLORATION
Field of the Invention:
[OOOI] The present invention relates generally to the field of hydrocarbon
exploration and more particularly to analysis of the extracted adsorbed gases which
are used for providing exploration leads for drilling a well with the purpose of
discovering hydrocarbons.
Backqround of the Disclosure
[0002] It is known that the soil at or near the surface of the earth, contains
various substances which are indicative of the presence of petroliferous deposits
below the earth's surface. Such indicator substances may be gaseous hydrocarbons.
The experimental laboratory investigations have verified that the concentrations of
adsorbed hydrocarbons in the soil can be used as an aid to explore for oil and gas
accumulations in the subsurface.
[0003] In the field of hydrocarbon exploration, the gases that are extracted and
adsorbed from the soil samples are analyzed. The data obtained there from is used
for providing exploration leads for drilling's well with the purpose of discovering
hydrocarbons.
[0004] Desorbtion unit assembly is the main device which is used to desorb,
adsorbed gases from soil samples. Conventional desorbtion unit has a main unit,
.round bottom flask, graduated stem with an in built septum and a two way k stop cock.
However, the conventionally known desorbtion unit assembly has various limitations,
which include but are not limited to the following limitations: (a) It cannot be used
when soil samples need to be heated for desorbing the adsorbed gases from soil
samples; (b) The septum does not hold under vacuum and heating or in case of
calcareous samples. The septum comes out with a high force, thus spoiling the
experiment and also brings safety concern; (c) There is high probability that the total
desorbed hydrocarbon gases along with carbon dioxide will not pass through
potassium hydroxide and therefore carbon- dioxde does not get completely absorbed
in potassium hydroxide, thus leading to erroneous results; (d) It is very difficult to
determine if there is any leak in the unit, under vacuum.
[OOOS] There was thus a need to develop a desorbtion assembly, wherein the
septum and all other components of the apparatus holds good and remain intact
even under heating and vacuum, which is required for desorbing the adsorbed
gases; the carbon dioxide is absorbed completely by the potassium hydroxide; leak,
if any,. in the system when under vacuum is easily detected by the level of KOH in
the U-tube, thus ensuring that experiments are being carried out under desired
standard conditions.
Brief Description of the invention
[0006] The desorbtion unit assembly of the present invention addresses the
aforesaid problems. The present subject matter provides a desorbtion apparatus for
adsorbed analysis of soil samples for surface geochemical exploration. The
desorbtion is done under vacuum and heat. Therefore, the device has been
\,,fabricated keeping in mind both these needs. The desorbtion unit of the present
invention comprises of Main unit; Round Bottom Flask; U-TUBE; Graduated stcm
wherein Septum is fitted into the constriction of the graduated stem; two way stop
cock used for vaccum; springs. The U- TUBE ensures that Carbon-Dioxide gas,
which is also desorbed from the soil sample is completely absorbed by the
Potassium Hydroxide solution in the U-TUBE. Only the remaining hydrocarbon
gases move up to the graduated stem on displacement with water. The Potassium
Hydroxide levels in both the arms of the U-TUBE helps in checking for leak in the
unit after vacuum. Septum is fitted into the constriction of the graduated stem during
its fabrication, therefore the Septum will not come out during heat and vacuum.
Brief Description of the Drawings
[0007] The present invention and its advantages will be better understood by
referring to the detailed description which is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference number
identifies the figure in which the reference number first appears.
[OOOS] Fig. 1 illustrates a schematic layout of Desorbtion assembly, in
accordance with an embodiment of the present subject matter.
[OOOS] Fig. 2 illustrates the feature of the Desorbtion Assembly wherein the UTUBE
helps in checking the leak in the unit after vaccum, in accordance with an
embodiment of the present subject matter.
[OOI 01 Fig.3 illustrates the Desorbtion appatratus as is conventionally known.
Detailed description of the invention
[OOI I ] The Desorbtion unit assembly of the present invention has a Main unit;
Round.Bottom Flask; /I-TUBE; Graduated stem wherein Septum is fitted into the
constriction of the graduated stem; two way stop cock used for vaccum; and springs.
The main unit of the Desorbtion unit assembly of the present invention has two side
tubes, one of it is the U-TUBE (102), where Potassium Hydroxide is filled. One end
of the U-TUBE (102) extends to the top, leading to a joint. In this joint, is inserted a
graduated stem with a septum (107), with the help of springs. The septum (107) is
fixed within a constriction in the graduated stem.
[OOI 21 The other tube (101) has a joint, which is connected with a round
bottom flask (103) with the help of springs. This flask (103) is filled with the
Orthophosphoric Acid.
[OOI 31 There is a two way stop cock (104) in the centre.of the tube (101). This
regulates the filling of the Potassium Hydroxide and Orthophophoric Acid.
[0014] There is another round bottom flask (105) on the top of the two way
I stop cock (104). This round bottom flask (105) has a joint. In this joint is inserted a
two way stop cock (106) which is connected to a rubber tube leading to the vacuum
pump and this helps in regulating the vacuum.
[OO 1 51 The desorbtion unit assembly as shown in Fig. 1 works in the following
t~~anneSro: il sample which has to be studied for its hydrocarbon gas composition, is
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! first dried, pulversied and seived through 270 mesh B.S.S. having 63 micron mesh Y:
size. The passing through material is usually clay and the material left on the mesh is
discarded.
[OOI 61 One gram of the clay sample is weighed and transferred to the round
bottom flask (103). Then, it is attached to the main unit with the help of springs.
[OOI 71 A graduated stem with septum (107), is inserted in the extended stem
of the U-TUBE (102) again with the help of springs. This is done to ensure that the
stem alongwith the septum (107), does not fly away during the application of heat
and vacuum.
[OOI 81 To the round bottom flask (105), another two way stop cock (106), is
connected. This stop cock (106) is connected to a rubber tube leading to the vacuum
pump.
1001 91 In the next step, the two way stop cock (104) is kept in vertical
position. The vacuum pump is then switched 'on, and once the whole unit is
evacuated, the two way stop cock (1 04) is kept in horizontal position
[0020] Thereafter, flask (105) is filled with Potassium Hydroxide, then two way
stop cock (104) is kept in vertical position. The unit is tilted to the right, so that
Potassium Hydroxide fills both the limbs of the U-TUBE (102). If the level in both
the limbs of the U-TUBE (102) is the same, the vacuum is holding good. If there is a
difference in the levels, the unit has to be checked for leakages.
[0021] Then the flask (105) is filled with Orthoposphoric acid, by controlling the
two way stop cock (104), it is filled in flask (103).
[0022] The two way stop cock (104), is brought to the horizontal position and
the unit is heated on a water bath.
[0023] On reaction of the acid with clay, Carbon Dioxide along with
hydrocarbon gases are liberated.
[0024] After heating for some time, the system is cooled, till no more gases
are liberated. Then the vacuum is displaced by filling the unit with water
[0025] The U-TUBE (102) ensures that all the gases pass through the
Potassium Hydroxide solution. Potassium Hydroxide absorbs the Carbon Dioxide
and the remaining gases, which are collected in the graduated stem the hydrocarbon
gases and are drawn out by inserting a syringe in the septum (107).
[0026] ,The gas in the syringe is subsequently injected in a gas chromatograph
for compositional analysis.
[0027] The unit in the present invention ensures a safe method to desorb the
hydrocarbon gases from the soil samples under vacuum and elevated temperatures.
The unit also ensures that the liberated gases pass through potassium hydroxide,
where carbon dioxide is absorbed and only the hydrocarbon gases are collected in
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the graduated stem. The U-TUBE (102) ensures that the total desorbed hydrocarbon , y-~
gases along with Carbon Dioxide passes through the U-TUBE (102). The Carbon
Dioxide is absorbed completely by the Potassium Hydroxide, present in the U-TUBE
(102). As we are only interested in the composition of the organic hydrocarbon
gases, carbon dioxide which is also desorbed, needs to be removed completely. This
is achieved by passing the gases through a U-TUBE (102) containing Potassium
Hydroxide, which completely absorbs the Carbon Dioxide. The Carbon Dioxide (parts
per million present in soil samples, which are calcareous in nature will be very high.
Addition of 50% Potassium Hydroxide solution in the limb of the U-TUBE (102) will
be easily sufficient to absorb the Carbon Dioxide in the newly designed unit. This
concentration of Potassium Hydroxide will help in removing the Carbon Dioxide
completely.
[0028] The newly designed unit is a small closed system. Therefore, the
vacuum is easily achieved. The vacuum facilitates the desorbtion to take place at a
lower temperature on heating on water bath.
[0029] In the newly designed unit, there is no possibility of contamination from
other hydrocarbon gases, as it is desorbed in the closed system under vacuum. The
gas sample is analysed in the gas chromatograph as soon as it is desorbed from the
soil sample, so there is no question of deterioration on waiting.
[0030] Several experiments have been conducted under similar conditions in
both conventional and the newly designed apparatus of the present invention. The
newly designed apparatus shows repeatable results with higher concentration of
t .hydrocarbons, proving that complete reaction is taking place in the x newly designed
apparatus. Carbon Dioxide was below detectable limit (bdl) in the newly designed
unit. It can be seen from the following table that the results obtained for the same
samples when analyzed simultaneously in two- different .apparatus i.e. the
conventiorially existing unit (Unit II) and the newly designed and developed unit (Unit
I), that the concentration of all the hydrocarbons from C1 to C3 increased when
analyzed through the newly designed and developed Unit I.
Note: 'Unit I' is the newly developed and designed apparatus;
'Unit II' is the conventionally existing apparatus.
['0031] The experiments clearly demonstrate the advantage of Unit I over Unit
II.
[0032] Several experiments conducted prove that the septum (107) and all
other components of the apparatus holds good and remain intact even under heating
and vacuum, required to maintain for desorbing adsorbed gases.
'[0033]
X- In the newly designed and developed unit, as shown in Fig. 2, the
Potassium Hydroxide levels in both the arms of the U-TUBE (102), helps in checking
for leak in the unit after vacuum. If there is a leak in the unit after vacuum, the level of
Potassium Hydroxide in both the limbs of the U-TUBE (102) will not be at the same
level. If the leak is from the gas collecting end, then the level in that limb would go
down and vice versa, if from the stop cock end, level would come down in that limb,
due to the pressure exerted by the air.
[0034] Although the subject matter has been described in considerable detail,
various embodiments of the invention are possible. It is to be understood that the
appended claims are not necessarily limited to the features described herein.

WE CLAIM:
1. A desorbtion unit assembly for adsorbed analysis of the soil samples for
surface geochemical exploration, the desorbtion unit assembly comprising:
a main unit having two side tubes (101) (102), one of which tubes is UTUBE
(102), wherein Potassium Hydroxide is filled; and the other tube (101)
has a joint, which IS connected with a round bottom flask (103) with the help of
springs;
graduated stem wherein Septum (107) is fitted into the constriction of
the graduated stem;
two way stop cock (104) (106) wherein a two way stop cock (104) is in
the centre of the tube (101) for regulating the filling of the Potassium
Hydroxide and Orthophophoric Acid;
and springs.
2. The desorbtion unit assembly as claimed in claim 1, wherein one end of the
U-TUBE (102) extends to the top, leading to a joint, in which joint is inserted a
graduated stem with a septum (107) with the help of springs.
3. The desorbtion unit assembly as claimed in claim 2 having another round
bottom flask (105) on the top of the two way stop cock (104) wherein the
round bottom flask (105) has a joint In which joint is inserted a two way stop
cock (106) which is connected to a rubber tube leading to the vacuum pump
and this helps in regulating the vacuum.
4. The desorbtion unit assembly as claimed in claim 1 wherein 1 gram of the clay
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'W sample is weighed and transferred to the round bottom flask (103), which is
then attached to the main unit with the help of springs.
5. The desorbtion unit assembly as claimed in claim 4 wherein graduated stem
with septum (107) is inserted in the extended stem of the U-TUBE (102) again
with the help of springs to ensure that the stem alongwith the septum (107),
does not fly away during the application of heat and vacuum.
6. The 'desorbtion unit assmebly as claimed in claim 5 wherein the two way stop
cock (104) is kept in vertical position and then the vacuum pump is switched
on to evacuate the whole unit, which unit when evacuated, the two way stop
cock (1 04) is kept in horizontal position.
7. The desorbtion unit assembly as claimed in claim 6 wherein flask (105) is
filled with Potassium Hydroxide, then two way stop cock (104) is kept in
vertical position and the unit is tilted to the right so that Potassium Hydroxide
fills both the limbs of the U-TUBE (1 02).
8. The desorbtion unit assembly as claimed in claim 7 wherein the flask (105) is
filled with Orthoposphoric acid and by controlling the two way stop cock (104),
it is filled in flask (1 03).
9. The desorbtion unit assembly as claimed in claim 8 wherein the two way stop
cock (104), is brought to the horizontal position and the unit is heated on a
water bath.
10.The desorbtion unit as claimed in any of the preceeding claims wherein the U'
i , k TUBE (102) ensures that all the gases pass through the Potassium Hydroxide
solution so that the Potassium Hydroxide absorbs the Carbon Dioxide and the
remaining gases, which are collected in the graduated stem the hydrocarbon
gases and are drawn out by inserting a syringe in the septum (107).