CN111119820A

CN111119820A - SAGD oil recovery method

Info

Publication number: CN111119820A
Application number: CN201811280873.7A
Authority: CN
Inventors: 罗池辉; 赵睿; 陈河青; 杨智; 高成国
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2018-10-30
Filing date: 2018-10-30
Publication date: 2020-05-08
Anticipated expiration: 2038-10-30
Also published as: CN111119820B

Abstract

The invention provides an SAGD oil production method, which comprises the following steps: step S1: establishing a pressure differential between two adjacent groups of wells to create a high pressure group of wells and a low pressure group of wells and maintain normal production of the two groups of wells; step S2: after the production of the two groups of well groups is finished, closing the production wells of the high-pressure well group, and keeping the injection wells of the high-pressure well group, the production wells of the low-pressure well group and the injection wells of the low-pressure well group open; step S3: and adjusting the injection-production parameters of the well group to balance the injection-production of the well group. The invention solves the problem of low oil extraction efficiency in the middle and later periods of SAGD oil extraction in the prior art.

Description

SAGD oil recovery method

Technical Field

The invention relates to the technical field of oil well exploitation, in particular to an SAGD oil extraction method.

Background

The SAGD technology, namely the steam assisted gravity drainage technology, is widely applied to the oil field exploitation of the heavy oil reservoir. The main principle of the double-horizontal-well SAGD is that two vertical parallel horizontal wells are arranged at the bottom of an oil layer, steam is continuously injected into the oil layer from the horizontal well serving as an injection well at the upper part to heat the oil layer and crude oil, a steam cavity is continuously expanded to exchange heat with the crude oil in the oil layer, the heated and viscosity-reduced crude oil and steam condensate water flow downwards under the action of gravity, and the heated and viscosity-reduced crude oil and steam condensate water are extracted from a horizontally arranged production well at the lower part of the oil layer. Under the injection and production mode, crude oil is mainly drained under the action of gravity, the transverse expansion driving force is weak, a triangular detention area is easily formed between two adjacent steam cavities, particularly in the middle and later periods of exploitation, in the descending stage of the steam cavities, the oil drainage angle is gradually reduced, the action of gravity is weakened, the oil production amount begins to be greatly reduced, the oil production speed is reduced, and the triangular cold oil detention area formed between the adjacent steam cavities cannot be effectively used.

Disclosure of Invention

The invention mainly aims to provide an SAGD oil extraction method, which solves the problem that the oil extraction efficiency in the middle and later periods of the SAGD oil extraction in the prior art is low.

In order to achieve the above object, the present invention provides a SAGD oil production method including: step S1: establishing a pressure differential between two adjacent groups of wells to create a high pressure group of wells and a low pressure group of wells and maintain normal production of the two groups of wells; step S2: after the production of the two groups of well groups is finished, closing the production wells of the high-pressure well group, and keeping the injection wells of the high-pressure well group, the production wells of the low-pressure well group and the injection wells of the low-pressure well group open; step S3: and adjusting the injection-production parameters of the well group to balance the injection-production of the well group.

Further, in step S1, in two adjacent groups of wells, the pressure of one group of wells is increased to be a high pressure group, and the pressure of the high pressure group is 0.2MPa to 1.0MPa higher than the pressure of the low pressure group.

Further, the pressure of the high pressure well group is 0.2MPa to 0.5MPa higher than the pressure of the low pressure well group.

Further, the elevation of the high pressure well group is lower than the elevation of the low pressure well group.

Further, in step S2, when the steam chambers of the two adjacent sets of wells are communicated and the oil layer between the two sets of steam chambers is lowered by a predetermined height, the production of the two sets of wells is completed, and then the production wells of the high pressure well set are closed, and the steam or hot water is continuously injected into the steam chambers through the injection wells of the high pressure well set.

Further, in step S3, the injection amount of the injection well of the high-pressure well group is adjusted to 80t/d to 120t/d, and the production-injection ratio of the well group is maintained to 1.0 to 1.2.

Further, in step S3, the production well of the high pressure well group is closed, hot water is continuously injected into the steam cavity of the high pressure well group through the injection well of the high pressure well group, the temperature of the hot water is greater than 90 ℃, the injection amount is 80t/d to 100t/d, the low pressure well group keeps producing, and the production injection ratio of the well group is maintained to be 1.0 to 1.2.

Further, the SAGD oil recovery method further includes a pre-selection step prior to step S1, the pre-selection step including selecting a well group according to the expansion of the steam cavity of the well group, the expansion being such that the steam cavity of the well group expands to the top of the reservoir and extends at the top of the reservoir a distance of 1/6 to 1/4 well spacing along the lateral direction of the reservoir.

Further, the pre-selection step also comprises the step of selecting two adjacent groups of wells with the same reservoir physical property and/or the same steam cavity development condition.

Further, the oil layer has an oil layer porosity greater than 0.28, a horizontal permeability greater than 1000mD, an oil saturation greater than 0.55, and no continuous mudstone and shale interbedders in the oil layer.

By applying the technical scheme of the invention, the pressure difference is established between the two adjacent well groups, so that the transverse driving force is generated between the high-pressure well group and the low-pressure well group, the purpose of combining oil displacement and oil drainage is achieved, the oil in a retention area between steam cavities of the adjacent well groups is quickened to be used, and the oil recovery speed and the oil recovery ratio in the middle and later periods of the SAGD are improved. And because the production well of high-pressure well group is closed, and the horizontal driving force between the well group can further be increased to injection well continuous operation for steam in the high-pressure well group can enter into in the low-pressure well group more effectively, makes the triangle-shaped cold oil detention district between the adjacent steam chamber that conventional can't use for get effective use, thereby realizes increasing substantially the recovery ratio of later stage in the SAGD oil recovery.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 shows a schematic of the configuration of a well group of the present invention utilizing a SAGD oil recovery process at the beginning of the pressure differential build-up; and

figure 2 shows a schematic diagram of the configuration of the well group of figure 1 after a pressure differential has been established.

Wherein the figures include the following reference numerals:

10. a high pressure well group; 20. a low pressure well group; 30. a production well; 40. an injection well; 50. a steam chamber.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

It is noted that, unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

In the present invention, unless specified to the contrary, use of the terms of orientation such as "upper, lower, top, bottom" or the like, generally refer to the orientation as shown in the drawings, or to the component itself in a vertical, perpendicular, or gravitational orientation; likewise, for ease of understanding and description, "inner and outer" refer to the inner and outer relative to the profile of the components themselves, but the above directional words are not intended to limit the invention.

The invention provides an SAGD oil production method, aiming at solving the problem of low oil production efficiency in the middle and later periods of SAGD oil production in the prior art.

A SAGD oil recovery process as shown in fig. 1, comprising: step S1: establishing a pressure differential between adjacent sets of wells to create a high pressure well set 10 and a low pressure well set 20 and maintain normal production of the two sets; step S2: after production of the two sets of well groups is completed, the production wells 30 of the high pressure well group 10 are closed, and the injection wells 40 of the high pressure well group 10, the production wells 30 of the low pressure well group 20 and the injection wells 40 of the low pressure well group 20 remain open; step S3: and adjusting the injection-production parameters of the well group to balance the injection-production of the well group.

This embodiment is through establishing the pressure differential between two adjacent well groups for produce the lateral drive power between high-pressure well group 10 and the low-pressure well group 20, reach the displacement of reservoir oil, the purpose that the draining combines together, accelerate to use the oil in the stagnant area between the steam chamber 50 of adjacent well group, improve SAGD middle and later stage oil recovery speed and recovery ratio. And because the production well 30 of the high-pressure well group 10 is closed, and the injection well 40 continuously works, the lateral driving force between the well groups can be further increased, so that steam in the high-pressure well group 10 can more effectively enter the low-pressure well group 20, and a triangular cold oil retention area between the adjacent steam cavities 50 which cannot be used conventionally is effectively used, thereby greatly improving the recovery ratio in the middle and later periods of SAGD oil production.

In this embodiment, in step S1, in two adjacent groups of wells, the pressure of one group of wells is increased to be the high-pressure group 10, and the pressure of the high-pressure group 10 is 0.2MPa to 1.0MPa higher than that of the low-pressure group 20, so as to increase the lateral driving force between the high-pressure group 10 and the low-pressure group 20 while ensuring the normal operation of the whole group of wells.

Preferably, the pressure of high pressure well group 10 is 0.2MPa to 0.5MPa higher than the pressure of low pressure well group 20.

In this embodiment, the high pressure well group 10 has an elevation lower than the elevation of the low pressure well group 20. Typically, the reservoir is not perfectly horizontal, which is generally at a certain inclination, and correspondingly, the elevation of one of the two adjacent well groups is entirely higher than the elevation of the other well group, so that the well groups match the reservoir. This embodiment is to increase the pressure of the lower elevation well group as the high pressure well group 10 so that the steam or hot water injected into the high pressure well group 10 through the injection well 40 can move upward by itself to exchange heat with the cold oil in the stagnant zone more effectively.

In this embodiment, in step S2, when the steam chambers 50 of two adjacent well groups are communicated and the oil layer between the two steam chambers 50 is lowered to a predetermined height, the oil production level is rapidly lowered, which indicates that the production of the two well groups is completed, at this time, the well groups have been used for 8-12 years, then the production wells 30 of the high pressure well group 10 are closed, the injection wells 40 of the high pressure well group 10 are kept injecting steam or hot water into the steam chambers 50 continuously, the low pressure well group 20 is kept producing normally, so that a lateral driving force is established between the low pressure well group 20 and the high pressure well group 10, and the production of cold oil in the stagnant zone is started.

In the present embodiment, in step S3, the injection amount of the injection well 40 of the high pressure well group 10 is adjusted to 80t/d to 120t/d, and the production ratio of the well group is maintained to 1.0 to 1.2 until the production is finished.

Specifically, the production wells 30 of the high pressure well group 10 are closed, hot water is continuously injected into the steam cavities 50 of the high pressure well group 10 through the injection wells 40 of the high pressure well group 10, the temperature of the hot water is greater than 90 ℃, the injection amount is 80t/d to 100t/d, the low pressure well group 20 keeps producing, the steam injection amount of the low pressure well group 20 is 80t/d to 100t/d, and the production-injection ratio of the well group is maintained to be 1.0 to 1.2, preferably 1.1. As a certain temperature field is formed in the retention area around the steam cavity 50 at the last stage of SAGD production, the flow can be realized without overhigh heat, and the high-pressure well group 10 can achieve the effects of supplementing pressure and displacing crude oil by replacing steam injection with hot water at the stage, thereby achieving the purposes of reducing heat loss and improving oil-steam ratio.

In this embodiment, the SAGD oil recovery method further includes a preselection step before step S1, the preselection step is to select a suitable well group to implement the SAGD oil recovery method according to the condition of the well group, the preselection step includes selecting the well group according to the expansion condition of the steam cavity 50 of the well group, the expansion condition is that the steam cavity 50 of the well group expands to the top of the oil layer and expands to the distance of 1/6 to 1/4 well distance along the transverse direction of the oil layer at the top of the oil layer, at this time, the well group has been used for 5-8 years in production, the steam cavity 50 is in a V shape overall, the triangular area formed between the V-shaped areas of the two steam cavities 50 is the stagnation area, as shown in the processes of fig. 1 to 2, when the pressure difference between the high pressure well group 10 and the low pressure well group 20 is just generated, the oil at the top of the stagnation area can firstly exchange with the hot gas to become, and is produced from the production well 30 by flowing into the production well 30 under the action of gravity, and as the production process advances to a later stage, the oil in the stagnant zone is gradually exchanged from top to bottom and is produced, so that the oil in the stagnant zone is produced.

Optionally, the pre-selecting step further comprises selecting two adjacent sets of wells having the same reservoir properties and/or the same development of the steam chamber 50. The reservoir physical properties and the steam cavity 50 development conditions of the two adjacent groups of wells are not necessarily completely the same, but only approximately the same or similar, and generally, the reservoir physical properties and the steam cavity 50 development conditions of the two adjacent groups of wells are similar.

Optionally, the reservoir has a reservoir porosity greater than 0.28, a horizontal permeability greater than 1000mD, an oil saturation greater than 0.55, and no continuous mudstone and shale interbeddings in the reservoir.

Preferably, the oil layer has an oil layer porosity of 0.3 to 0.34, a horizontal permeability of 2000mD to 2200mD, a vertical permeability to horizontal permeability ratio of 0.6 to 0.8, and an oil saturation of 0.7 to 0.76.

The implementation process of the SAGD oil recovery method of the embodiment is as follows:

(1) and (3) carrying out oil reservoir coarse screening, wherein the buried depth of a selected oil layer is 240m, the thickness of a continuous oil layer is 22m, the porosity of the oil layer is 0.32, the horizontal permeability is 2100mD, the ratio of the vertical permeability to the horizontal permeability is 0.7, the oil saturation is 0.73, continuous mudstone and shale interlayers do not develop in the oil layer, and the viscosity of the degassed crude oil is 2.9 ten thousand centipoise at the temperature of 50 ℃.

(2) The SAGD well spacing for oil reservoir deployment is 80m, the horizontal segment length is 400m, the production horizontal well spacing is 2m from the bottom of an oil layer, the steam injection horizontal well spacing is 5m from the production horizontal well, two adjacent SAGD groups with similar reservoir physical properties are selected, the two SAGD groups are put into production simultaneously, and the operating pressure is 2.8-3.0 MPa; after 6 years of conversion to SAGD production, from the monitoring results, the steam chamber 50 was topped and expanded laterally by 18-30 m.

(3) Adjusting the operating pressure of one well group to be 0.2-0.5MPa higher than that of the adjacent well, keeping the steam injection amount of the two well groups at 150t/d and the production-injection ratio at 1.0-1.2, keeping the two well groups in the state for continuous SAGD production, and after 3.5 years, fusing the steam cavities 50 of the two well groups and reducing the steam cavities to a certain height, so that the oil extraction level is greatly reduced.

(4) And (3) shutting down the production wells 30 of the high-pressure well group 10, switching the injection wells 40 to continuously inject hot water, wherein the temperature of the hot water is higher than 90 ℃, the injection amount is 80-100t/d, continuing SAGD production by the low-pressure wells, the steam injection amount is 80-100t/d, and maintaining the overall production-injection ratio to be about 1.1 until the completion.

Compared with the conventional SAGD of the same block, the middle and later oil recovery speed of the SAGD of the two well groups implementing the method is averagely improved by 45 percent, the ultimate recovery efficiency is averagely improved by 15.6 percent, and the oil-gas ratio is basically unchanged.

The data in the above embodiment is data used in actual construction, and may be adjusted according to actual conditions.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

1. the problem of low oil recovery efficiency in the middle and later periods of SAGD oil recovery in the prior art is solved;

2. the oil in a retention area between adjacent steam cavities is used quickly, and the oil recovery speed and the oil recovery ratio in the middle and later periods of the SAGD are improved;

3. the operation is simple and the implementation is convenient.

It is to be understood that the above-described embodiments are only a few, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise, and it should be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of features, steps, operations, devices, components, and/or combinations thereof.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A SAGD oil recovery process, comprising:

step S1: establishing a pressure differential between two adjacent groups of wells to create a high pressure group of wells (10) and a low pressure group of wells (20) and maintain normal production of both groups of wells;

step S2: after production of both sets of wells is complete, closing the production wells (30) of the high pressure well set (10), the injection wells (40) of the high pressure well set (10), the production wells (30) of the low pressure well set (20) and the injection wells (40) of the low pressure well set (20) remaining open;

step S3: and adjusting the injection-production parameters of the well group to balance the injection-production of the well group.

2. The SAGD oil recovery method of claim 1, wherein in two adjacent sets of the wells, the pressure of one of the sets of wells is increased to the high pressure well set (10), and the pressure of the high pressure well set (10) is 0.2MPa to 1.0MPa higher than the pressure of the low pressure well set (20) in step S1.

3. The SAGD oil recovery process of claim 2, wherein the pressure of the high pressure well group (10) is 0.2 to 0.5MPa higher than the pressure of the low pressure well group (20).

4. The SAGD oil recovery method of claim 2, wherein the elevation of the high pressure well group (10) is lower than the elevation of the low pressure well group (20).

5. The SAGD oil recovery method of claim 1, wherein, in step S2, when steam chambers (50) of two adjacent sets of the wells communicate and an oil layer between the two sets of the steam chambers (50) descends to a predetermined height, production of the two sets of the wells is completed, and then production wells (30) of the high pressure well set (10) are closed, and steam or hot water injection into the steam chambers (50) through injection wells (40) of the high pressure well set (10) is maintained continuously.

6. The SAGD oil recovery method of claim 1, wherein in step S3, injection well (40) of the high pressure well group (10) is adjusted to an injection rate of 80t/d to 120t/d and a production-injection ratio of the well group is maintained to 1.0 to 1.2.

7. The SAGD oil recovery method of claim 6, wherein in step S3, a production well (30) of the high pressure well group (10) is closed, hot water is continuously injected into a steam cavity (50) of the high pressure well group (10) through an injection well (40) of the high pressure well group (10) and the temperature of the hot water is greater than 90 ℃, the injection amount is 80t/d to 100t/d, the low pressure well group (20) keeps producing, and the production injection ratio of the well group is maintained to be 1.0 to 1.2.

8. The SAGD oil recovery method of claim 1, further comprising a pre-selection step prior to step S1, the pre-selection step including selecting the well group according to the spread of its steam cavity (50) extending to the top of the reservoir and at the top of the reservoir along the lateral spread of the reservoir 1/6 to 1/4 well spacing.

9. The SAGD oil recovery method of claim 8, wherein the pre-selection step further includes selecting two adjacent sets of the wells having the same reservoir properties and/or the same development of the steam cavity (50).

10. The SAGD oil recovery process of claim 8, wherein the reservoir has a reservoir porosity greater than 0.28, a horizontal permeability greater than 1000mD, an oil saturation greater than 0.55, and the reservoir is free of continuous mudstone and shale interbeddes.