U.S. patent application number 12/580524 was filed with the patent office on 2010-04-22 for method for producing crude oil.
Invention is credited to Werner Ernst, Michael Heisel.
Application Number | 20100096146 12/580524 |
Document ID | / |
Family ID | 42035155 |
Filed Date | 2010-04-22 |
United States Patent
Application |
20100096146 |
Kind Code |
A1 |
Heisel; Michael ; et
al. |
April 22, 2010 |
METHOD FOR PRODUCING CRUDE OIL
Abstract
The invention describes a method for injecting a fluid into a
crude oil-containing layer of rock or earth by means of a suitable
line, wherein the line is introduced into the layer of rock or
earth and the fluid is injected for the purpose of an enhanced
crude oil production from the crude oil-containing layer of rock or
earth.
Inventors: |
Heisel; Michael; (Pullach,
DE) ; Ernst; Werner; (Tubingen, DE) |
Correspondence
Address: |
The BOC Group, Inc.
575 MOUNTAIN AVENUE
MURRAY HILL
NJ
07974-2082
US
|
Family ID: |
42035155 |
Appl. No.: |
12/580524 |
Filed: |
October 16, 2009 |
Current U.S.
Class: |
166/400 ;
166/268 |
Current CPC
Class: |
E21B 43/168
20130101 |
Class at
Publication: |
166/400 ;
166/268 |
International
Class: |
E21B 43/16 20060101
E21B043/16 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 2008 |
DE |
102008052465.4 |
Aug 21, 2009 |
DE |
102009038445.6 |
Claims
1. A method for injecting a fluid into a crude oil-containing layer
of rock or earth by means of a suitable line, wherein the line is
introduced into the layer of rock or earth and the fluid is
injected for the purpose of an enhanced crude oil production from
the crude oil-containing layer of rock or earth, characterized in
that the fluid is discontinuously injected into the crude
oil-containing layer of rock or earth.
2. The method according to claim 1, characterized in that the fluid
is injected into the crude oil-containing layer of rock or earth in
a positioned manner.
3. The method according to claim 1, characterized in that the fluid
is injected in the gaseous state.
4. The method according to claim 3, characterized in that the fluid
is selected from the group consisting of nitrogen, carbon dioxide
and gaseous hydrocarbons.
5. The method according to claim 4 wherein said gaseous hydrocarbon
is methane.
6. The method according to claim 1, characterized in that the fluid
is injected in pulses.
7. The method according to claim 6, characterized in that different
fluids are injected in succeeding pulses.
8. The method according to claim 6, characterized in that the time
lag between two injection pulses is not shorter than pulse
length,
9. The method according to claim 8, characterized in that the time
lag between two injection pulses is one to ten times the pulse
length.
10. The method according to claim 6, characterized in that the
period required by the gas to cover half the distance between the
line, through which the fluid is injected, and the conveyor line,
is chosen as minimal pulse length.
11. The method according to claim 6, characterized in that the
fluid is injected from more than one line in a positioned manner,
wherein pulse length, pulse distance and/or start of the injection
in the case of at least one line is/are different from pulse
length, pulse distance and/or start of the injection in the case of
at least one other line.
12. The method according to claim 9, characterized in that the
quantities of induced fluids from at least two lines are adjusted
in such a manner that the induced fluid from a first line is
diverted in the direction of the conveyor line by means of the
quantity of the injected fluid from at least a second line.
13. The method according to claim 10, characterized in that the
direction of the induced fluids from at least two lines is adjusted
in such a manner that the combined fluid flow from the lines is
oriented in the direction of the conveyor line.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority from German Patent
Application No. DE 102008052465.4, filed Oct. 21, 2008, and German
Patent Application No. DE 102009038445.6, filed Aug. 21, 2009.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a method for injecting a fluid into
a crude oil-containing layer of rock or earth by means of a
suitable line, wherein the line is introduced into the layer of
rock or earth and the fluid is injected for the purpose of an
enhanced crude oil production from the crude oil-containing layer
of rock or earth.
[0003] Crude oil is typically located in crude oil reservoirs close
to and below the earth's surface. Depending on the depth of the
reservoir, the crude oil is recovered from these reservoirs in open
cast drilling, as in the case of the Canadian oil sand fields, but
mostly in drift drilling or by means of drilling platforms, which
provide for a production in the middle of the ocean. Crude oil is
mainly recovered in drift drilling. For this purpose, conveyor
lines are introduced underneath the earth's surface as far as the
depth of the crude oil reservoir by means of boreholes. The crude
oil is recovered from the crude oil reservoir via this conveyor
line.
[0004] The production thereby substantially takes place in three
phases. In a greater depth, the crude oil is under the pressure of
the superimposed load of the layers of earth and of the associated
crude oil carrier gas, if applicable. In the first phase, the crude
oil can often be produced without additional measures by means of
the inherent pressure in the reservoir. In response to the decrease
of the inherent pressure, the oil can be conveyed to the surface by
means of technical resources, such as subsurface pumps.
[0005] As a rule, the inherent pressure of the crude oil reservoir
alone is no longer sufficient for transporting the crude oil to the
earth's surface after a production of from 10% to 15% of the
quantity available in the reservoir. This phase of the primary
crude oil production is thus followed by the phase of the secondary
production. In this second phase, the reservoir pressure is
increased by pumping water, steam or gas via lines, which have been
introduced into the earth by means of boreholes. According to the
state of the art, water is typically re-pumped in this phase,
whereby it is possible to convey between 30% and 40% of the oil,
which is originally present in the reservoir (original oil in place
or OOIP) to the earth's surface. The residual oil, which remains in
the reservoir and which is increasingly ductile and dense,
complicates a further constant production. Additional oil can be
conveyed out of the reservoir only via special methods for the
tertiary crude oil production.
[0006] According to the state of the art, different fluids are
pressed under pressure into the vicinity or directly into the
reservoir, respectively, by means of suitable lines in this phase
of the crude oil production. Among others, heat methods such as the
pressing in of hot water or superheated steam or the pressing in of
gases such as nitrogen and carbon dioxide are known hereby. On the
one hand, carbon dioxide increases the pressure in the reservoir,
but on the other hand also dissolves in the crude oil under
suitable conditions. The viscosity of the crude oil is considerably
reduced by means of the carbon dioxide dissolved in the crude oil
and the production is thus improved.
[0007] Such a method for the tertiary crude oil production is
described in patent publication GB 2 379 685. In the state of the
art described in GB 2 379 685, a second line is introduced into the
crude oil reservoir parallel to the conveyor line of the crude oil
for supplying a fluid. A fluid consisting of water, steam, steam
foam or foam, nitrogen and/or carbon dioxide is pressed into the
crude oil reservoir via this second line. Preferably, water or an
aqueous solution or foam, respectively, is hereby used. According
to the state of the art disclosed in GB 2 379 685, the line for
injecting the fluid consists of two different sections. Both
sections are separated by means of stoppers, which are typically
called "packer" in the oil industry and which can be separately
exposed to the fluid. The fluid is pressed into the different areas
of the crude oil reservoir via the two different sections in such a
manner that the supplied quantity of the fluid varies cyclically
and asynchronously. The method is described as being particularly
suitable for crude oil reservoirs, which appear in geological
formations, which encompass cracks or gaps. By means of the method
described in GB 2 379 685, the proportion of water in the
water-crude oil mixture conveyed via the conveyor line is to be
maintained below a certain threshold. The cyclical admission and
the cracks or gaps present in the crude oil reservoir prevent a
water quantity, which is too large, from reaching into the conveyor
line. In the case of a suitable variation of the conveying rates,
the cracks and gaps work like drainages, which divert the water
from the surrounding layers. The injection of the fluid into the
crude oil reservoir thereby simply takes place via horizontal holes
in the supply line, which are distributed across the entire
periphery of the line. The fluid is thus pressed out of the supply
line so as to be distributed in all spatial directions in a
spherically even manner.
[0008] However, the high consumption of fluids is a disadvantage of
the method described in the state of the art so far. For example,
in the event that gas is used in the case of a method for the
tertiary crude oil production, it must in most cases be transported
to the oil well in an extensive manner. Platforms for the oil
production in the ocean form an extreme example herein. In the
event that carbon dioxide is to be used for the tertiary crude oil
production in the case of such crude oil fields, said carbon
dioxide must first be brought to the oil platform by ship or by
pipeline. In the case of an alternative use of nitrogen for the
tertiary crude oil production on such platforms, the nitrogen would
have to be produced on location, that is, a small plant for air
separation would have to be installed.
SUMMARY OF THE INVENTION
[0009] The instant invention is thus based on the object of
embodying a method of the afore-mentioned type in such a manner
that the use of fluid is minimized.
[0010] The instant object is solved in that the fluid is injected
into the crude oil-containing layer of rock or earth in a
discontinuous manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention will be defined below in more detail by means
of the exemplary embodiments illustrated in the figures.
[0012] FIG. 1 shows an exemplary embodiment of the invention for
injecting a fluid from two lines, which are located approximately
at the same distance from the conveyor line.
[0013] FIG. 2 shows an exemplary embodiment of the invention for
injecting a fluid from two lines, which are located at different
distances from the conveyor line.
DETAILED DESCRIPTION OF THE INVENTION
[0014] According to the instant invention, the fluid is injected
into the crude oil-containing layer of rock or earth in a
discontinuous manner. That is, according to the invention, the
fluid is not injected for the entire length of the method for the
tertiary crude oil production, but is injected into the crude
oil-containing layer of rock or earth in a discontinuous manner
only in certain phases or cycles.
[0015] Within the scope of this application, a discontinuous
injection refers to the fact that the fluid is injected for a
certain predetermined period and that this period is followed by a
phase, in which no fluid is injected, said phase in turn being
followed by a phase of the fluid injection. A discontinuous
injection of a gas thus takes place in several regular or irregular
pulses or periods, respectively. Within the scope of this
application, the injection or the injecting of a fluid refers to
the pressing in or introduction of the fluid into the crude
oil-containing layer of rock or earth.
[0016] Fluid can be conserved in different ways by means of the
discontinuous injecting of the fluid according to the
invention.
[0017] On the one hand, fluid is conserved because the already
injected fluid expands in the rude oil-containing layer of rock or
earth in the period in which no fluid is injected. The expanding
fluid thus forms a fluid cushion, which drives oil in the direction
of the conveyor line, where it can be produced. On the other hand,
the flow speed of the fluid in the crude oil-containing layer of
rock or earth increases after the injecting of the fluid. The crude
oil loosens from the rock or from the earth and is further produced
with considerably lower pressure. Surprisingly, it became apparent
in comparative tests that in the case of a discontinuous injection
of the fluid according to the invention, the crude oil sticks to
the crude oil-containing layer of rock or earth to a considerably
smaller degree than in the case of a continuous injection according
to the method of the state of the art. By means of the phases of
the non-injection according to the method of the invention, the
fluid can surprisingly also remove oil from the crude
oil-containing layer of rock or earth. Said oil adheres to small
water films or minerals comprising a large surface in the crude
oil-containing layer of rock or earth. This fluid mixture, which
includes the oil, which was removed in such a manner, can be moved
by means of the next injection.
[0018] Preferably, the fluid is injected into the crude
oil-containing layer of rock or earth in a positioned manner. In
this preferred embodiment of the invention, a considerably higher
conservation of necessary fluid can be attained in response to a
consistent production effect. By means of the positioned injection
of the fluid, that is, by means of the specific injection of the
fluid in the direction of the conveyor line, the quantity of the
injected fluid is additionally minimized during the injection
phase. By means of the positioned injecting, the fluid entry no
longer takes place into the complete dihedral angle, but only into
a partial area. The quantity of the injected fluid is thus
minimized. By combining the discontinuous injection according to
the invention with a positioned injection, a minimization of the
injected fluid quantity can thus be attained in this embodiment of
the invention. The discontinuous injection according to the
invention leads to the formation of a fluid cushion, which, in the
case of a positioned entry, drives the crude oil in the direction
towards the conveyor line, where it can be produced above ground.
The fluid injection leads to the formation of a fluid cushion. In
the case of the discontinuous injection according to the invention,
said fluid cushion is set into motion by subsequent injections. In
the case of a positioned injection in this embodiment of the
invention, this fluid cushion can be moved in the direction from
the line to a second line, wherein the second line serves as a
conveyor line.
[0019] Preferably, the fluid is injected in the gaseous state.
Particularly preferably, the fluid consists of nitrogen, carbon
dioxide and/or gaseous hydrocarbons, particularly preferably
methane. The advantages of the method according to the invention
have an effect in particular in the case of the discontinuous
injection of gaseous fluids. For the most part, gaseous fluids such
as nitrogen or carbon dioxide are not present in sufficient
quantities in the vicinity of the crude oil-containing layers of
rock or earth. For the most part, these gaseous fluids would thus
have to be transported across longer distances. A considerable
reduction of the required fluid quantities, as it occurs according
to the method according to the invention, considerably improves the
efficiency of a method for producing crude oil from a crude
oil-containing layer of rock or earth. The gaseous fluid used in
each case is thereby advantageously chosen according to the state
and structural conditions of the crude oil-containing layer of rock
or earth. Gaseous hydrocarbons mix with the crude oil in the layer
of rock or earth, thus reduce the capillary forces, which hold the
crude oil in the layer of rock or earth and thus facilitate the
transport to the conveyor line. A similar effect occurs with the
use of gaseous carbon dioxide. Gaseous carbon dioxide mixes with
the crude oil and reduces the viscosity. When using gaseous carbon
dioxide, a simpler transport of the crude oil in the crude
oil-containing layer of rock or earth is thus attained as well.
[0020] The economically more cost-efficient nitrogen, however,
virtually does not mix with the crude oil. In the case of a
repeated injection of gaseous nitrogen, a gas front forms, into
which the light hydrocarbons contained in the crude oil from the
crude oil-containing layer of rock or earth diffuse. This increases
the viscosity of the remaining residual oil, which is thus more
difficult to remove from the layer of rock or earth. This
disadvantage can be overcome in that an injection phase is followed
by an idle phase, in which the remaining oil particles have time to
mix with the stored water. This mixture can then be driven to the
conveyor line in response to the next injection phase. It is also
advantageous for nitrogen that it does not have an aggressive
effect on metals and on the layer of rock or earth and that, as
compared to carbon dioxide, it is suitable in particular for less
permeable layers of rock or earth due to the small density.
Nitrogen is thereby preferably injected at an over-static pressure.
Nitrogen enters into the reservoir and expands in the provided
direction of injection as long as the gas pressure remains. The
residual oil in the pore structure can thereby be desorbed and can
be moved through the pore structure together with the gas. In the
event that the injection is interrupted, the nitrogen gas can also
expand laterally in the phase of the non-injection and can thus
permeate into pore spaces, in which oil still adheres to small
water films or to minerals comprising a large inner surface or in
which oil droplets are present in small pores. The oil-water
mixture formed in such a manner can be moved in the direction of
the conveyor line by means of the next injection.
[0021] Depending on the state of the crude oil-containing layer of
rock or earth, a combination of one or several of said gaseous
fluids can be advantageous. The combination of gaseous carbon
dioxide and gaseous nitrogen is hereby particularly advantageous.
The two afore-mentioned advantages of both fluids can also be
combined by means of the combination of the two fluids.
[0022] In another embodiment of the invention, gaseous fluids such
as carbon dioxide and liquid fluids such as water are combined. In
this embodiment of the invention, carbon dioxide and water are
injected so as to alternate, that is, the injection of carbon
dioxide is followed by a phase without fluid injection, which in
turn is followed by the injection of water. The injected gas
thereby causes an improved flowability of the oil and the
subsequently injected water causes the formation of oil banks in
the borders of the gas flows, which move more or less with straight
boundary lines.
[0023] Advantageously, the fluid is injected in pulses. In this
embodiment of the invention, the fluid is advantageously injected
in regular pulses of predetermined length. A pulse is thereby
understood to be the time period from start to stop of the
injection of the fluid. Advantageously, several pulses of
predetermined length are thereby injected consecutively. The
injection of different fluids in response to succeeding pulses has
also proven to be advantageous. Advantageously, the different
mechanisms and advantageous of the respective fluids can simply be
combined with one another by means of the injection of different
fluids in succeeding pulses. For instance, gaseous carbon dioxide
can be injected in a first pulse and the viscosity of the oil in
the crude oil-containing layer of rock or earth can thus be
reduced. The crude oil now having a lower viscosity can now be
driven in the direction of the conveyor line by means of the
injection of gaseous nitrogen in the succeeding pulse.
[0024] Advantageously, the time lag between two injection pulses is
not shorter than the pulse length and is preferably one to ten
times the pulse length. By means of the pulsed injection, it is
attained that the fluid cushion is reduced by increasing the
pressure during the injection process and is subsequently increased
again. This effect becomes smaller with decreasing impulse lengths.
Measurements have shown that it is even possible for a negative
effect to occur in the case of pulse quantities, which are too
short. In these cases, the injected fluid substantially escapes
again through the line, through which the fluid has been injected,
without having driven the oil in the crude oil-containing layer of
rock or earth in the direction of the conveyor line. A sufficient
pulse period must thus be observed.
[0025] The time lag between two injection pulses, that is, the time
during which no fluid is injected, must also be sufficiently long.
Advantageously, the time lag between two injection pulses is thus
not shorter than the pulse length. Measurements have shown that now
and then a negative effect occurs in the case of shorter periods,
that is, the fluid is not pressed in the direction towards the
conveyor line by means of the pulse. However, longer periods are
possible. A time lag between two injection pulses, which is one to
ten times the pulse length, is preferred for an economically
sensible operation.
[0026] The period required by the gas to cover half the distance
between the line, through which the fluid is injected, and the
conveyor line, is particularly preferred as minimal pulse length.
In this embodiment of the invention, it is thus ensured that the
crude oil is pushed on in the direction of the conveyor line by
means of the injected fluid. In the event that measurements
relating to the fluid speed in the respective crude oil-containing
layer of rock or earth are not available, a speed in the range of
from 0.5 m/min to 5 m/min is assumed. The speed is thereby a
function of the porosity of the respective crude oil-containing
layer of rock or earth. In the case of crude oil-containing layers
of rock or earth comprising a high porosity, a high fluid speed can
be assumed.
[0027] In an embodiment of the invention, the fluid is injected
from more than one line in a positioned manner, wherein pulse
length, pulse distance and/or start of the injection in the case of
at least one line is/are different from pulse length, pulse
distance and/or start of the injection in the case of at least one
other line. In the event that more than one line is used for the
positioned and pulsed injection of fluid flows in the direction of
a conveyor line, it is advantageous to inject both fluid flows in a
time-lagged manner. Sensibly, one should make sure that the first
injected fluid flow has actually arrived in the reach of the second
fluid flow. A shifting of the first fluid flow in the direction of
the conveyor line thus becomes possible. In the case of an early or
late injection of the second fluid flow, the combined fluid flow is
conveyed past the conveyor line; pulse length, pulse distance
and/or time of the injections must thereby be chosen in such a
manner that all of the fluid is injected in the direction of the
conveyor line.
[0028] In another embodiment of the invention, in the case of which
the fluid is injected from two lines, which have the same distance
from the conveyor line, it is advantageous to start the pulses at
the same time and with the same pulse length, but with different
injection direction.
[0029] Advantageously, the quantities of injected fluids from at
least two lines are adjusted in such a manner that the injected
fluid from a first line is diverted in the direction of the
conveyor line by means of the quantity of the injected fluid from
at least a second line. The quantity of injected fluid from the
second line is thereby adjusted in such a manner that it can divert
the injected fluid from the first line in the direction of the
conveyor line. Advantageously, the quantity of the fluid injected
in the second line is similar to the magnitude of the quantity of
the injected fluid from the first line. Preferably, the ratio of
the quantities of the injected fluids lies between 10:1 and 1:1.
Likewise, the direction of the induced fluids from at least two
lines is advantageously adjusted in such a manner that the combined
fluid flow from the lines is oriented in the direction of the
conveyor line.
[0030] The instant invention encompasses a number of advantages as
compared to the state of the art. In particular the quantity of the
induced fluid for the same conveyor capability can be reduced
considerably as compared to the state of the art. Fluid is
conserved, because the already induced fluid expands in the crude
oil-containing layer of rock or earth during the phase, in which no
fluid is induced. The speed of the induced fluid in the crude
oil-containing layer of rock or earth furthermore increases in
phases, whereby the crude oil is removed from the layer of rock or
earth to a considerably improved degree than with a fluid flow,
which flows continuously at the same speed.
[0031] FIG. 1 shows an exemplary embodiment of the method according
to the invention, wherein the fluid is injected into the crude
oil-containing layer of rock or earth via the two lines 1 and 2.
Both lines 1 and 2 are located at approximately the same distance
from the conveyor line 3. The gas flow G1 is injected into the
crude oil-containing layer of rock or earth from the line 1 in a
pulsed manner. The gas flow G2 is also induced into the crude
oil-containing layer of rock or earth from the line 2 in a pulsed
manner. Pulse durations of approx. 20 min are used thereby. The
time lag between two pulses of an injection line is approx. 1 hour.
The injected gas quantities G1 and G2 are thereby in the same
magnitude in each case. Due to the overlap of the positioned and
pulsed gas flows G1 and G2, a resulting gas flow G3 forms, which
moves in the direction of the conveyor line 3. The crude oil is
thus driven in the direction of the conveyor line 3 by means of the
positioned and pulsed gas flows. In this embodiment of the
invention, nitrogen and carbon dioxide are injected so as to
alternate, so that the different characteristics of both gases can
be used for the crude oil production.
[0032] FIG. 2 shows an exemplary embodiment of the invention,
wherein the fluid is injected into the crude oil-containing layer
of rock or earth via two lines 1 and 2. In this exemplary
embodiment of the invention, the two lines 1 and 2 are spaced apart
from the conveyor line 3 at different distances. In this exemplary
embodiment of the invention, the pulsed injection of the fluid from
line 1 starts prior to the pulsed injection of the fluid from line
2. This means that the two pulses from line 1 and line 2 are
time-lagged. The time lag between an injection pulse in line 1 and
an injection pulse in line 2 thereby corresponds to the time, which
the fluid induced from line 1 requires to reach into the injection
area of the fluid from line 2. In this exemplary embodiment of the
invention, the fluid is injected via the line 1 with a pulse length
of three hours. After a delay of approx. one hour, the fluid from
line 2 is injected with a pulse length of three hours. Pulses with
a pulse length of one hour are subsequently injected from both
lines. Shorter pulse lengths are used here, because after the
2.sup.nd pulse, the fluid cushion in the rock must only be set into
motion or maintained in motion, respectively.
[0033] A pulse length of one hour is also possible for the
injection from line 1 and a pulse length of 2 hours is possible for
the injection from line 2 as a function of the characteristic of
the respective crude oil-containing layer of rock or earth. In the
event that the crude oil-containing layer of rock or earth in the
immediate surroundings of line 1 is highly porous, a fluid cushion
can establish there very rapidly. In the event that the crude
oil-containing layer of rock or earth in the surroundings of line 2
is less porous, longer pulse lengths are used here, because the
establishment of a fluid cushion also takes longer.
* * * * *