U.S. patent application number 12/641579 was filed with the patent office on 2010-07-08 for gas activity analysis in the ground.
Invention is credited to Michael HEISEL.
Application Number | 20100170683 12/641579 |
Document ID | / |
Family ID | 42123330 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100170683 |
Kind Code |
A1 |
HEISEL; Michael |
July 8, 2010 |
GAS ACTIVITY ANALYSIS IN THE GROUND
Abstract
A method of introducing a propellant gas into the ground is
described, wherein a trace gas that can be analysed above the
ground or the earth's surface is added to said propellant gas.
According to the invention hydrogen is used as the trace gas,
whereby the proportion of the trace gas hydrogen in the propellant
gas/trace gas mixture is a maximum of 10% by vol., preferably a
maximum of 5% by vol.
Inventors: |
HEISEL; Michael; (Pullach,
DE) |
Correspondence
Address: |
The BOC Group, Inc.
575 MOUNTAIN AVENUE
MURRAY HILL
NJ
07974-2082
US
|
Family ID: |
42123330 |
Appl. No.: |
12/641579 |
Filed: |
December 18, 2009 |
Current U.S.
Class: |
166/403 |
Current CPC
Class: |
G01N 2001/388 20130101;
E21B 47/11 20200501; E21B 43/166 20130101 |
Class at
Publication: |
166/403 |
International
Class: |
E21B 43/22 20060101
E21B043/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 8, 2009 |
DE |
102009004104.4 |
Claims
1. A method of introducing a propellant gas into the ground,
wherein a trace gas that can be analysed above the ground or the
earth's surface is added to said propellant gas, characterised in
that hydrogen is used as the trace gas.
2. The method according to claim 1, characterised in that at least
one additional trace gas is added to the propellant gas in addition
to the hydrogen.
3. The method according to claim 1, characterised in that said
propellant gas is selected from the group consisting of nitrogen,
nitrogen-rich gas mixtures, carbon dioxide, carbon dioxide-rich gas
mixtures and saturated hydrocarbons.
4. The method according to claim 3, characterised in that said
saturated hydrocarbons are selected from the group consisting of
methane.
5. The method according to claim 1, characterised in that the
proportion of the trace gas hydrogen in the propellant gas/trace
gas mixture is a maximum of 10% by vol.
6. The method according to claim 1, characterised in that the
proportion of the trace gas hydrogen in the propellant gas/trace
gas mixture is a maximum of 5% by vol.
7. The method according to claim 2, characterised in that helium is
used as a further trace gas.
8. The method according to claim 1, characterised in that the
propellant gas/trace gas mixture is blended immediately before it
is introduced into the ground.
9. The method according to claim 1, characterised in that the
propellant gas/trace gas mixture is injected into the ground at a
depth of at least one metre below the earth's surface.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a method of introducing a
propellant gas into the ground, wherein a trace gas that can be
analysed above the ground or the earth's surface is added.
[0002] The term "ground" hereinafter denotes all types of soil,
rock and bedrock, into which gases or gas mixtures are introduced
for particular purposes, as explained below.
[0003] Gases or gas mixtures--hereinafter referred to as propellant
gases, are used in the ground to move substances or liquids. An
example of this is the displacement of ground water charged with
noxious substances, which is "driven" to a pumping site, where the
water is pumped to the surface. Once purification has taken place,
the water can once again be returned to the ground. Another example
is the driving of crude oil in reservoir rock, so that a greater
volume of crude oil stored in the rock can be extracted using EOR
(Enhanced Oil Recovery). Nitrogen and carbon dioxide are the most
commonly used propellant gases in this case.
[0004] In order to determine whether and, if appropriate, where the
propellant gas used flows or flows to in the ground, an easily
analysable gas--hereinafter referred to as the trace gas--is added
to the propellant gas and the concentration of this trace gas on
the earth's surface is measured. This enables conclusions to be
drawn as to where the propellant gas actually flowed to. Helium has
hitherto been commonly used as the trace gas. The helium molecule
is small, compared with the molecular size of the gases used as a
propellant. This means that the helium molecule is able to diffuse
through cracks, gaps and holes in the ground or rock more
easily.
[0005] Helium can be analysed in the presence of air. Because air
is approx. 79% nitrogen, traces of nitrogen, which may possibly
emerge from the ground or rock as a propellant gas, cannot be
detected in air. Helium, on the other hand, can still be detected
in traces in air too. The presence of helium on the surface
indicates where the actual propellant gas has flowed to. The
detection threshold for helium stands at around 5 mbar*l/s with
state-of-the-art helium analysis devices. The helium concentration
in the ambient air is approx. 5.24 vppm. A measuring device must
therefore be capable of detecting differences in concentration of
around a few vppm. This is entirely possible with the measuring
technology known today.
[0006] However, helium is a very rare gas, which on the one hand is
comparatively expensive and, on the other, is often not available
in sufficient quantities. In order to conduct investigations or for
EOR or the expulsion of water, however, large quantities or trace
gas have to be made available over prolonged periods often lasting
several months. A typical gas volume for the expulsion of water
charged with noxious substances is, for example, 1000 Nm.sup.3/hr
N.sub.2 with 10% by vol. helium, which is equivalent to a helium
volume of 100 Nm.sup.3/hr. This sort of helium volume can often not
be made available in practice currently, particularly since a
multiplicity of helium-consuming rival applications exist in
medical technology, in which human lives sometimes depend on the
availability of helium. It is therefore also understandable that
these applications are given higher priority in the apportionment
of helium.
[0007] It was further suggested that other reaction-inert gases,
particularly other noble gases like argon, krypton or xenon should
be considered as trace gases. Argon, which is obtained in large
volumes from air decomposers, exists in the ambient air in a
proportion of approx. 1%. For this reason, traces of argon that
occur in the trace gas application are not detectable. Another
aggravating factor with the other noble gases mentioned above is
that mass spectrometers have to be used for detection. However,
hydrocarbons are also indicated in the region of the spectral lines
of these gases, as a result of which the analysis can be distorted.
This is an unacceptable disadvantage, particularly when used for
EOR.
BRIEF SUMMARY OF THE INVENTION
[0008] The problem addressed by the present invention is that of
indicating a generic method of introducing a propellant gas into
the ground, which avoids the aforementioned disadvantages.
[0009] In order to solve this problem, a generic method of
introducing a propellant gas into the ground is suggested, which is
characterised in that hydrogen is used as the trace gas.
[0010] Further advantageous embodiments of the method according to
the invention for introducing a propellant gas into the ground,
which are objects of the dependent patent claims, are characterised
in that [0011] at least one additional trace gas is added to the
propellant gas in addition to the hydrogen, [0012] nitrogen-rich
gas mixtures, carbon dioxide, carbon dioxide-rich gas mixtures
and/or saturated hydrocarbons, such as methane, are used as the
propellant gas, [0013] the proportion of the trace gas hydrogen in
the propellant gas/trace gas mixture is a maximum of 10% by vol.,
preferably a maximum of 5% by vol., [0014] helium is used as a
further trace gas, [0015] the propellant gas/trace gas mixture is
blended immediately before it is introduced into the ground and
[0016] the propellant gas/trace gas mixture is injected into the
ground at a depth of at least one metre below the earth's
surface.
DETAILED DESCRIPTION OF THE INVENTION
[0017] According to the invention, hydrogen is now used as the
trace gas. While the use of hydrogen as a test gas for identifying
leaks and for tightness testing has been known for some time, the
use of hydrogen as a trace gas has not been considered hitherto.
Due to its explosion risk when mixed with air, hydrogen can only be
used as a trace gas in very special cases.
[0018] It is advantageously used as a forming gas--this refers to
hydrogen/nitrogen gas mixtures--with a hydrogen share of 5% and a
nitrogen share of 95%. According to ISO 10156, the lower explosion
threshold is around 5.7% by vol. hydrogen in air. However, this
explosion risk must be definitively removed, if hydrogen is to be
safely used as a trace gas. It has now surprisingly emerged that,
provided it is handled correctly, hydrogen can be safely used as a
trace gas at even higher contents of up to approx. 10% by vol..
[0019] Investigations have shown that hydrogen used as a trace gas
surprisingly diffuses significantly quicker in the ground or rock
than gases customarily used as propellants. The hydrogen
concentrations found are therefore lower than in the propellant
gas/trace gas mixture supplied to the ground, even at a small
distance from the injection site. A rapid separation of the
propellant gas/trace gas mixture evidently occurs, which means that
a lower and therefore uncritical hydrogen concentration results.
This effect can now be exploited to enable hydrogen to be used as a
trace gas in concentrations of over 5%.
[0020] If the hydrogen trace gas emerges at the earth's surface,
its concentration in the air is several orders of magnitude below
the lower explosion threshold, if the injection site is at least
approx. 1 metre beneath the earth's surface. This is because even
with a diffusion length of one metre, the hydrogen content has
actually dropped from several % by vol. to a few ppm. Consequently,
an increase in the hydrogen concentration of the propellant
gas/trace gas mixture to values off 10% by vol. and more is
possible without there being any risk to the individuals taking the
measurements and/or the immediate environment.
[0021] Hydrogen can be detected in air in concentrations below 1
ppm. Hydrogen therefore meets the necessary prerequisites as a
trace gas: [0022] Hydrogen is normally only present in the ambient
air in low concentrations of under 1 ppm, which means that trace
quantities that are detected also originate from the trace gas and
undoubtedly not from the environment. [0023] Hydrogen detectable in
air in the range <1 ppm. [0024] Hydrogen is only slightly
reactive at ambient temperature, so that there are few if any
secondary reactions with earth or rock. Such reactions could
distort the measuring result significantly. [0025] Hydrogen is
produced in large quantities and is usually readily available in an
industrial setting. [0026] The hydrogen measuring or analytical
equipment needed for the practical execution of the method
according to the invention for introducing a propellant gas into
the ground is adequately known from the state of the art. This
equipment does not usually require modification for the intended
application.
[0027] If the method according to the invention is used for EOR in
large oil fields, it may be necessary to mix hydrogen and the
propellant gas, preferably nitrogen, on site. In practice, the
upper limit for consumption of the propellant gas/trace gas
mixture, which is supplied in bottles, is around 50 Nm.sup.3/hr.
Propellant gas/trace gas mixture volumes that go beyond this are
produced by mixing propellant gas and trace gas on site, in
accordance with an advantageous embodiment of the method according
to the invention.
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