EP2180139A2 - Method for producing crude oil - Google Patents

Abstract

The method involves introducing two lines (1, 2) into a crude oil-containing layer of rock or earth, and discontinuously injecting fluid into the crude oil-containing layer of rock or earth in a positioned manner and in a gaseous state for enhancing crude oil production from the crude oil-containing layer of rock or earth. Different fluids are injected in succeeding pulses, where time delay between two injection pulses is not shorter than pulse length. The two lines are spaced apart from a conveyor line (3) at different distances.

Description

The invention relates to a method for injecting a fluid into a petroleum-containing rock or soil layer by means of a suitable conduit, wherein the conduit is introduced into the rock or earth layer, and the fluid for the purpose of increased production of petroleum from the petroleum-containing Rock or soil layer is injected.

Petroleum is typically found in oil deposits near and below the surface of the earth. From these deposits, the oil is depending on the depth of the deposit in the open pit, as in the Canadian oil sands fields, but usually in civil engineering or by means of oil rigs, which allow a pumping in the middle of the sea won. Mainly oil is extracted in civil engineering. For this purpose, delivery lines are introduced to the depth of the oil reservoir under the surface of the earth by means of boreholes. About this conveyor line, the oil is extracted from the oil reservoir.

The funding is essentially carried out in three phases. At a greater depth, the oil is under the pressure of the burdensome earth layers and the associated associated gas. In the first phase, oil can often be pumped by the autogenous pressure in the reservoir without further action. When the internal pressure drops, the oil can be pumped up with technical aids such as deep pumps.

The autogenous pressure of the oil reservoir alone is generally insufficient after 10% to 15% of the amount in the deposit to transport the oil to the surface of the earth. This phase of primary oil production therefore follows the phase of secondary production. In this second phase, the reservoir pressure is increased by the injection of water, steam or gas through, introduced into the soil by means of holes, lines. According to the state of the art, water is usually pumped in at this stage, whereby between 30% and 40% of the oil originally present in the deposit (original oil in place or OOIP) can be conveyed to the earth's surface. The remainder remaining increasingly dense and dense oil in the deposit hinders further constant promotion. Further oil can only be extracted from the deposit via special processes for tertiary mineral oil extraction.

In this phase of petroleum production, various fluids are pressed under pressure with suitable lines into the vicinity or directly into the deposit according to the prior art. Known here u.a. Heat processes such as the injection of hot water or superheated steam or the injection of gases such as nitrogen and carbon dioxide. On the one hand, carbon dioxide increases the pressure in the deposit, but on the other hand it dissolves under suitable conditions in crude oil. Due to the dissolved carbon dioxide in the oil, the viscosity of the petroleum is significantly reduced and thus improves the promotion.

Such a tertiary petroleum production process is described in Patent Publication GB 2 379 · 685. At the in GB 2 379 685 described prior art, a second conduit for supplying a fluid is introduced into the crude oil deposit parallel to the delivery line of the petroleum. About this second line, a fluid consisting of water, steam, foam or foam, nitrogen and / or carbon dioxide is pressed into the oil reservoir. In this case, water or an aqueous solution or foam is preferably used. The line for the injection of the fluid, consists after the in GB 2 379 685 The prior art disclosed two different sections. Both sections are separated by plugs, commonly called "packers" in the petroleum industry, and can be separately charged with the fluid. The fluid is injected into the different regions of the oil reservoir via the two different sections in such a way that the supplied quantity of the fluid varies cyclically and asynchronously. The process is described as being particularly suitable for petroleum deposits that occur in geological formations that have fractures or gaps. With the help of in GB 2 379 685 described method, the proportion of water in the conveyed via the delivery line, water-petroleum mixture should be kept below a certain limit. The cyclical loading and the fractures and gaps present in the oil reservoir prevent an excessively large amount of water from entering the delivery line. With a suitable variation of the feed rates, the fractures and cracks work like drains, which drain the water from the surrounding layers. The injection of the fluid into the oil reservoir is done simply through horizontal holes in the supply line, which over the entire Scope of the line are distributed. The fluid is thus pressed spherically evenly distributed in all spatial directions from the supply line.

A disadvantage of the method described so far in the prior art, however, is the high consumption of fluids. For example, if gas is used in a process for tertiary mineral oil production, it usually has to be transported to the source of oil in a complex manner. An extreme example here are platforms for oil production in the sea. If carbon dioxide is to be used for tertiary mineral oil production in such oil fields, it must be brought to the oil platform first by ship or by pipeline. In an alternative use of nitrogen for tertiary oil recovery on such platforms, the nitrogen would have to be generated on site, i. a small air separation unit will be installed.

The present invention is therefore based on the object, a method of the type mentioned input in such a way that the consumption of fluid is minimized.

The present object is achieved in that the fluid is injected discontinuously into the petroleum-containing rock or earth layer.

In accordance with the present invention, the fluid is discontinuously injected into the petroleum-containing rock or soil layer. That is, according to the invention, the fluid is not injected over the entire duration of the tertiary petroleum production process, but is injected intermittently into the petroleum-containing rock or earth layer only in certain phases or cycles.

In the context of this application, a discontinuous injection is understood to mean that the fluid is injected over a certain predetermined period of time and this period is followed by a phase in which no fluid is injected, which in turn is followed by a phase of fluid injection. A discontinuous injection of a gas thus takes place in several regular or irregular pulses or periods. That is, in a discontinuous injection of the fluid according to the invention, no fluid is injected over a certain and predetermined period of time. This period, in which no fluid is injected, may vary in duration, but always significantly more than a few seconds.

For the purposes of this application, the injection or injection of a fluid is understood as meaning the injection or introduction of the fluid into the petroleum-containing rock or earth layer.

By the discontinuous injection of the fluid according to the invention, fluid can be saved in a number of ways.

On the one hand, fluid is saved because in the time when no fluid is injected, the already injected fluid in the petroleum-containing rock or earth layer expands. The expanding fluid thus forms a fluid cushion which drives oil in the direction of the delivery line where it can be conveyed. On the other hand, after the injection of the fluid, the flow rate of the fluid in the petroleum-containing rock or earth layer increases. The oil dissolves from the rock or from the earth and is further promoted with significantly less pressure. In comparative experiments, it has surprisingly been found that in a discontinuous injection of the fluid according to the invention, the petroleum remains much less adhere to the petroleum-containing rock or soil layer, as in a continuous injection by a method according to the prior art. By virtue of the non-injection phases of the process of the present invention, the fluid can surprisingly also liberate oil from the petroleum-containing rock or soil layer which adheres to water cuticles or high surface area minerals in the petroleum-containing rock or earth layer. This fluid mixture, which contains the oil dissolved out in this way, can be moved by the next injection and thus reaches a second line, which serves as a delivery line.

Preferably, the fluid is directionally injected into the petroleum containing rock or soil layer. In this preferred embodiment of the invention, a significantly higher saving of necessary fluid can be achieved with the same conveying effect. The directed injection of the fluid, ie targeted injection of the fluid in the direction of the delivery line, the amount of injected fluid is additionally minimized during the injection phase. By directed injection, the fluid entry is no longer in the entire solid angle, but only in a partial area. This minimizes the amount of injected fluid. By combining the discontinuous injection according to the invention with a directed injection, a minimization of the reach injected amount of fluid. By means of the discontinuous injection according to the invention, a fluid cushion is formed, which, when directed, drives the crude oil in the direction of the delivery line, where it can be conveyed for days. The fluid injection forms a fluid cushion. In the case of the discontinuous injection according to the invention, this is set in motion by the following injections. In a directional injection in this embodiment of the invention, this fluid pad can be moved in the direction from the conduit to a second conduit, the second conduit serving as a delivery conduit.

Preferably, the fluid is injected in the gaseous state. Particularly preferably, the fluid consists of nitrogen, carbon dioxide and / or gaseous hydrocarbons, more preferably methane. The advantages of the method according to the invention are particularly useful in the discontinuous injection of gaseous fluids. Gaseous fluids such as nitrogen or carbon dioxide are usually not present in the vicinity of the petroleum-containing rock or earth layers in sufficient quantities. Therefore, these gaseous fluids usually have to be transported over longer distances. A significant reduction in the amount of fluid required, as occurs in the process of the invention, significantly improves the economics of a process for extracting petroleum from a petroleum-containing rock or soil layer. The gaseous fluid used in each case is expediently selected according to the properties and conditions of the petroleum-containing rock or earth layer. Gaseous hydrocarbons mix with the petroleum in the rock or soil layer, thereby reducing the capillary forces that hold the petroleum in the rock or earth layer and thus facilitate transport to the delivery line. A similar effect occurs with the use of gaseous carbon dioxide. Gaseous carbon dioxide mixes with the petroleum and reduces the viscosity. Thus, with the use of gaseous carbon dioxide also easier transport of petroleum is achieved in the petroleum-containing rock or soil layer.

The economically cheaper nitrogen, however, practically does not mix with the petroleum. Upon multiple injection of gaseous nitrogen, a gas front is formed, into which the light hydrocarbons contained in the oil diffuse from the petroleum-containing rock or earth layer. This increases the viscosity of the remaining oil, which is consequently heavier in the rock or soil layer is dissolved out. This disadvantage can be remedied by following the injection phase with a rest phase in which the remaining oil particles have time to mix with the storage water. This mixture can then be driven to the delivery line at the next injection phase. It is also advantageous for nitrogen that it does not have an aggressive effect on metals and the layer of rock or soil and, because of its lower density compared to carbon dioxide, is particularly suitable for less permeable rock or earth layers. Nitrogen is preferably injected with superatmospheric pressure. Nitrogen enters the reservoir and spreads in the intended injection direction as long as the gas pressure remains. In this case, the remaining oil in the pore structure can be desorbed and moved together with the gas through the pore structure. If the injection is interrupted during the non-injection phase, the nitrogen gas can also expand laterally and thus penetrate into pore spaces in which oil still adheres to water cuticles or to minerals with a large internal surface or oil droplets are present in small pores. The thus formed oil-water mixture can be moved by the next injection in the direction of the delivery line.

Depending on the nature of the petroleum-containing rock or earth layer, a combination of one or more of said gaseous fluid may be appropriate. Particularly advantageous in this case is the combination of gaseous carbon dioxide and gaseous nitrogen. By combining the two fluids, the above-mentioned advantages of both fluids can also be combined.

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 mutually injected, that is, on the injection of carbon dioxide, followed by a phase without fluid injection, which in turn is followed by the injection of water. In this case, the injected gas causes a better flowability of the oil and the subsequently injected water causes the formation of oil banks in the boundaries of the gas streams, which move more or less with straight boundary lines.

Advantageously, the fluid is injected in pulses. In this embodiment of the invention, the fluid is expediently injected in regular pulses of predetermined length. A pulse is understood to be the time span from which Start until the stop of the injection of the fluid. In this case, a plurality of pulses of predetermined length are expediently injected successively. There is no fluid injection between the pulses. The speed or the pressure of the fluid during a pulse are approximately constant. It has also proved to be advantageous to inject different fluids in successive pulses. By injecting different fluids in successive pulses, the various mechanisms of action and advantages of the respective fluids can advantageously be easily combined with one another. Thus, for example, gaseous carbon dioxide can be injected in a first pulse and thus the viscosity of the oil in the petroleum-containing rock or earth layer can be reduced. By injecting gaseous nitrogen in the following pulse, the petroleum can be driven with now lower viscosity in the direction of the delivery line.

Advantageously, the time interval between two injection pulses is not shorter than the pulse length, and is preferably the simple to ten times the pulse length. The pulsed injection ensures that the fluid cushion is reduced by increasing the pressure during the injection process and then increased again. This effect becomes smaller with shorter pulse lengths. Measurements have shown that too short pulse rates can even have a negative effect. In these cases, the injected fluid substantially exits through the conduit through which the fluid has been injected without propelling oil in the petroleum-rich rock or soil layer toward the production conduit. Therefore, care must be taken to ensure a sufficient pulse duration.

The time interval between two injection pulses, i. the time in which no fluid is injected, must also be sufficiently long. Advantageously, therefore, the time interval between two injection pulses is not shorter than the pulse length. Measurements have shown that sometimes at shorter times a negative effect occurs, i. the fluid is not pressed by the pulse in the direction of the delivery line. Longer times are possible. For economically viable operation, a time interval between two injection pulses is preferably used, which is the simple to ten times the pulse length.

More preferably, the minimum pulse length is the time required for the gas to travel halfway between the line through which the fluid is injected. and the support line. Thus, in this embodiment of the invention ensures that the petroleum is propelled in the direction of the delivery line through the injected fluid. If there are no measurements of the fluid velocity in the respective petroleum-containing rock or earth layer, a velocity in the range of 0.5 m / min. up to 5 m / min. accepted. The speed depends on the porosity of the respective petroleum-containing rock or earth layer. For petroleum-containing rock or soil layers with high porosity, a high fluid velocity can be assumed.

In one embodiment of the invention, the fluid is injected as a directed pressure surge. In this embodiment of the invention, the fluid is injected as a short-term surge directed into the petroleum-containing rock or soil layer. This process is repeated several times, with no fluid being injected between the pressure surges.

In one embodiment of the invention, the fluid is injected from more than one line directed, wherein pulse length, pulse interval and / or start of the injection at least one line is different from pulse length, pulse spacing and / or start the injection of at least one other line / are. If more than one line is used for directional and pulsed injection of fluid streams in the direction of a delivery line, it is expedient to inject both fluid streams at a time offset. It is expedient to wait until the fluid flow which has been injected first has actually come into the range of the second fluid flow. As a result, a displacement of the first fluid flow in the direction of the delivery line is possible. Too early or too late injection of the second fluid stream, the combined fluid stream is conducted past the delivery line. Pulse length, pulse interval and / or time of injections must be chosen so that the entire fluid is injected in the direction of the delivery line.

In another embodiment of the invention, in which the fluid is injected from two lines, both equidistant from the delivery line, it is expedient to start the pulses simultaneously and with the same pulse length but different injection direction.

Conveniently, the amounts of injected fluids from at least two lines are adjusted so that the injected fluid from a first conduit through the Amount of injected fluid from at least one second line, the direction of the delivery line is deflected. The amount of injected fluid from the second conduit is thereby adjusted so that it can deflect the injected fluid from the first conduit in the direction of the delivery line. The amount of fluid injected in the second conduit is suitably similar to the magnitude of the amount of injected fluid from the first conduit. Preferably, the ratio of the amounts of injected fluids is between 10: 1 and 1: 1. Likewise, the direction of the induced fluids is expediently set from at least two lines such that the combined fluid flow is directed out of the lines in the direction of the delivery line.

The present invention has a number of advantages over the prior art. In particular, the amount of induced fluid can be significantly reduced for an equal delivery rate over the prior art. Fluid is saved since the already-induced fluid propagates in the petroleum-containing rock or soil layer during the phase in which no fluid is induced. Furthermore, the velocity of the induced fluid in the petroleum-containing rock or earth layer increases in phases, whereby the petroleum is much better dissolved out of the rock or earth layer than in a continuously flowing at the same speed fluid flow.

Figur 1:

ein Ausführungsbeispiel der Erfindung zur Injektion eines Fluides aus zwei Leitungen, die ungefähr gleich weit von der Förderleitung entfernt sind.

Figur 2:

Ein Ausführungsbeispiel der Erfindung zur Injektion eines Fluides aus zwei Leitungen, die unterschiedlich weit von der Förderleitung entfernt sind.

In the following, the invention will be explained in more detail with reference to the embodiments illustrated in the figures. Show it

FIG. 1:

an embodiment of the invention for the injection of a fluid from two lines, which are approximately equidistant from the feed line.

FIG. 2:

An embodiment of the invention for the injection of a fluid from two lines that are different distances from the delivery line.

FIG. 1 shows an embodiment of the method according to the invention, wherein the fluid is injected via the two lines 1 and 2 in the petroleum-containing rock or soil layer. Both lines 1 and 2 are approximately equal to the delivery line. 3 away. From line 1, the gas stream G1 is pulsed injected into the petroleum-containing rock or soil layer. From the line 2, the gas stream G2 is also pulsed induced in the petroleum-containing rock or earth layer. Here are pulse lengths of about 20 min. used. The time interval between two pulses of an injection line is about 1 hour. The injected gas quantities G1 and G2 are each of the same order of magnitude. Due to the superimposition of the directed and pulsed gas flows G1 and G2, a resulting gas flow G3, which moves in the direction of the delivery line 3, is formed. Thus, the oil is driven in the direction of the delivery line 3 by the directional and pulsed gas streams. In this embodiment of the invention, nitrogen and carbon dioxide are alternately injected, so that the different properties of both gases can be used for crude oil production.

FIG. 2 shows an embodiment of the invention, wherein the fluid is injected via two lines 1 and 2 in the petroleum-containing rock or earth layer. In this embodiment of the invention, the two lines 1 and 2 spaced at different distances from the feed line 3. In this embodiment of the invention, the pulsed injection of the fluid from line 1 begins before the pulsed injection of the fluid from line 2. That is, the two pulses from line 1 and line 2 are staggered in time. The time interval between an injection pulse in line 1 and an injection pulse in line 2 corresponds to the time required for the fluid induced from line 1 to reach line 2 in the injection area of the fluid. In this embodiment of the invention, the fluid is injected via line 1 with a pulse length of three hours. After a delay of about one hour, the fluid from line 2 is injected with a pulse length of three hours. Subsequently, pulses are injected from both lines with a pulse length of one hour. Here, shorter pulse lengths are used, since from the second pulse the fluid cushion in the rock only has to be brought into motion or kept in motion.

Depending on the characteristics of the respective petroleum-containing rock or earth layer, a pulse duration of one hour for injection from line 1 and a pulse duration of 2 hours for injection from line 2 is also possible. If the petroleum-bearing rock or earth layer in the immediate vicinity of line 1 is very porous, a fluid cushion can build up there very quickly. Is the petroleum-containing rock or earth layer in the vicinity of line 2 less porous, longer pulse lengths are used here, since the construction of a fluid cushion also takes longer.

Claims (12)

A method of injecting a fluid into a petroleum-containing rock or soil layer by means of a suitable conduit, wherein the conduit is introduced into the rock or soil layer, and the fluid for the purpose of increased production of petroleum from the petroleum-containing rock or soil layer is injected, characterized in that the fluid is injected discontinuously into the petroleum-containing rock or soil layer. A method according to claim 1, characterized in that the fluid is injected directed into the petroleum-containing rock or soil layer. A method according to claim 1 or 2, characterized in that the fluid is injected in the gaseous state. A method according to claim 3, characterized in that the fluid consists of nitrogen, carbon dioxide and / or gaseous hydrocarbons, preferably methane. Method according to one of claims 1 to 4, characterized in that the fluid is injected in pulses. A method according to claim 5, characterized in that in successive pulses different fluids are injected. A method according to claim 5 or 6, characterized in that the time interval between two injection pulses is not shorter than the pulse length, preferably the simple to ten times the pulse length. Method according to one of claims 5 to 7, characterized in that as a minimum pulse length, the time is selected that the gas needs to travel halfway between the line through which the fluid is injected, and the delivery line. Method according to one of claims 5 to 8, characterized in that the fluid is injected from more than one line directed, wherein pulse length, pulse spacing and / or start of the injection at least one line different from pulse length, pulse spacing and / or start of the injection of at least one other line is / is. A method according to claim 9, characterized in that the amounts of induced fluids from at least two lines are adjusted such that the induced fluid is deflected from a first line through the amount of injected fluid from at least one second line in the direction of the delivery line. A method according to claim 9 or 10, characterized in that the direction of the induced fluids from at least two lines is set such that the combined fluid flow is directed from the lines in the direction of the conveying line. Method according to one of claims 2 to 4, characterized in that the fluid is injected as a directed pressure surge.

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