CN114382451A - SAGD oil production method and enhanced oil production well pattern - Google Patents
SAGD oil production method and enhanced oil production well pattern Download PDFInfo
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- 238000010796 Steam-assisted gravity drainage Methods 0.000 title claims abstract description 177
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 107
- 239000003921 oil Substances 0.000 claims abstract description 164
- 238000011084 recovery Methods 0.000 claims abstract description 55
- 238000010793 Steam injection (oil industry) Methods 0.000 claims abstract description 26
- 238000000605 extraction Methods 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims abstract description 24
- 239000010724 circulating oil Substances 0.000 claims abstract description 9
- 238000002347 injection Methods 0.000 claims description 35
- 239000007924 injection Substances 0.000 claims description 35
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 33
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 20
- 239000001301 oxygen Substances 0.000 claims description 20
- 229910052760 oxygen Inorganic materials 0.000 claims description 20
- 229910052757 nitrogen Inorganic materials 0.000 claims description 15
- 239000007789 gas Substances 0.000 claims description 10
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 3
- 230000035699 permeability Effects 0.000 abstract description 6
- 238000004891 communication Methods 0.000 description 8
- 239000010779 crude oil Substances 0.000 description 6
- 238000011161 development Methods 0.000 description 6
- 239000000295 fuel oil Substances 0.000 description 6
- 238000002485 combustion reaction Methods 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 230000009467 reduction Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000003546 flue gas Substances 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000010924 continuous production Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 208000035126 Facies Diseases 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000010408 sweeping Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/2406—Steam assisted gravity drainage [SAGD]
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/243—Combustion in situ
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
- E21B43/305—Specific pattern of wells, e.g. optimising the spacing of wells comprising at least one inclined or horizontal well
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Abstract
The invention provides an SAGD oil production method and an enhanced oil production well pattern, wherein the SAGD oil production method adopts the SAGD enhanced oil production well pattern which comprises an SAGD well group and an encrypted horizontal well; the SAGD oil recovery method comprises the following steps: s10, after the SAGD well group is preheated, injecting horizontal well steam injection to produce horizontal well oil extraction; preheating the encrypted horizontal well and converting the preheated encrypted horizontal well into circulating oil extraction; step S20, after the steam cavity of the SAGD well group is communicated with the steam cavity of the encryption horizontal well, the encryption horizontal well stops circulating oil production and changes to continuous oil production; step S30, after igniting the residual oil in the steam cavity, continuously injecting air and steam into the encrypted horizontal well, specifically, injecting air into the long pipe and injecting steam into the short pipe. By the method, the problems of low oil recovery speed and low ultimate recovery rate in the middle and later stages of SAGD for reservoirs with high permeability in the prior art are solved.
Description
Technical Field
The invention relates to the technical field of oil extraction in oil fields, in particular to an SAGD oil extraction method and an enhanced oil extraction well pattern.
Background
SAGD (Steam Assisted Gravity Drainage) is a development mode for developing heavy oil reservoirs, is widely applied to double horizontal wells, generally comprises an injection horizontal well and a production horizontal well, high-dryness Steam is continuously injected into an oil layer by the injection horizontal well, and high-temperature produced liquid is produced by the production horizontal well right below the injection horizontal well. The double horizontal well SAGD technology has been successfully industrialized in Liaohe oil field and Xinjiang oil field in China at present.
Under the normal condition, the permeability of a reservoir developed by adopting super heavy oil SAGD is near 5000mD, the oil extraction speed can reach 6-8% in a peak period, and the recovery rate can reach 60%.
For a continental facies reservoir stratum, the reservoir stratum has serious heterogeneity, the viscosity of degassed oil at the reservoir temperature is more than 5 multiplied by 104mPa & s, the viscosity is still more than 20mPa & s at the temperature of 200 ℃, the permeability is often lower than 2000mD, the recovery rate at the peak stage is 2-3%, the recovery rate is lower than 55%, the problems of low oil recovery rate at the middle and later stages of SAGD and low final recovery rate exist, and the economic benefit of the SAGD technology is influenced.
Disclosure of Invention
The invention aims to provide an SAGD oil production method and an enhanced oil production well pattern, so as to solve the problems that in the prior art, for a reservoir with larger permeability, the SAGD middle and later stage oil production speed is lower, and the final recovery ratio is lower.
The above object of the present invention can be achieved by the following technical solutions:
the invention provides an SAGD oil production method, which adopts an SAGD intensified oil production well pattern, wherein the SAGD intensified oil production well pattern comprises an SAGD well group and a encryption horizontal well, and the SAGD well group comprises an injection horizontal well and a production horizontal well;
the SAGD oil recovery method comprises the following steps:
step S10, after the SAGD well group is preheated, injecting steam into the horizontal well, and producing oil from the horizontal well; preheating the encrypted horizontal well and converting the preheated encrypted horizontal well into circulating oil extraction;
step S20, after the steam cavity of the SAGD well group is communicated with the steam cavity of the encryption horizontal well, the encryption horizontal well stops circulating oil production and changes to continuous oil production;
and step S30, after residual oil in the steam cavity is ignited, continuously injecting air and steam into the encrypted horizontal well.
In a preferred embodiment, step S40 is implemented between step S10 and step S20, and step S40 includes: and injecting nitrogen gas along with the injection horizontal well.
In a preferred embodiment, the step S40 is performed starting when the steam cavity of the SAGD well group expands laterally by 40m at the top of the reservoir; when the steam cavity drain angle of the SAGD well group is reduced to 20 °, the step S30 is started.
In a preferred embodiment, in the step S40, the injection amount of the steam and the nitrogen in the gas injected into the horizontal well is in a ground volume ratio range of 1:20 to 1: 50.
In a preferred embodiment, in the step S30, the injection horizontal well injects steam, and the steam injection rate is less than 20 t/d.
In a preferred embodiment, a long pipe and a short pipe are arranged in the encrypted horizontal well; in the step S30, the long-pipe air injection and the short-pipe steam injection are adopted in the encrypted horizontal well, and the steam injection rate of the long-pipe air injection is 20000-50000 m3/d。
In a preferred embodiment, in step S30, oxygen-enriched air with oxygen content not less than 60% is injected into the steam chamber from the horizontal encrypted well, and after a plurality of consecutive days, residual oil in the steam chamber is ignited.
In a preferred embodiment, the toe end of the horizontal section of the horizontal infill well is raised.
In a preferred embodiment, in step S10, the SAGD well group is preheated in a circulating manner, and the encryption horizontal well is preheated in a throughput manner.
The invention provides an SAGD (steam assisted gravity drainage) enhanced oil recovery well pattern which comprises an encrypted horizontal well and at least two SAGD well groups, wherein each SAGD well group comprises an injection horizontal well and a production horizontal well;
the encrypted horizontal well is arranged between two adjacent SAGD well groups; and the toe end of the horizontal section of the encrypted horizontal well is upwards warped.
In a preferred embodiment, the toe end of the horizontal segment of the horizontal encrypted well is raised by 5-10 m.
In a preferred embodiment, the toe end of the horizontal segment of the raised encrypted horizontal well is a well segment with a horizontal segment close to 50m of the toe.
The invention has the characteristics and advantages that:
according to the SAGD oil extraction method, steam is adopted to assist gravity drainage development, the SAGD well group and the encrypted horizontal well are exploited simultaneously, the well spacing is reduced, the utilization of reserves among the SAGD well groups is accelerated, the oil extraction speed of the whole exploitation process is improved, and the steam cavities are communicated quickly.
Step S10 is a cavity expanding production stage, step S20 is a horizontal well assisted SAGD enhanced oil recovery production stage, and step S30 is an air assisted SAGD enhanced oil recovery stage. The horizontal well assists the SAGD production to effectively extract residual oil between wells, and the horizontal well assists the SAGD enhanced oil recovery production stage to reduce the steam injection amount and improve the oil-gas ratio of production. Residual oil in the air combustion steam cavity is injected and the inter-well hot oil is swept in the later period, the steam injection amount is further reduced in the air-assisted SAGD intensified oil production stage, the reduction of the exploitation cost in the whole exploitation process is realized, meanwhile, steam is injected, the residual oil on the lower portion is displaced to a production horizontal well in the SAGD well group, the crude oil continuously flows to the production well, and the recovery ratio is ensured to be up to more than 60% finally.
The SAGD oil production method is applied to thick oil development, well pattern adjustment is carried out by arranging the encrypted horizontal wells, and effective utilization of triangular zone oil layers between two adjacent horizontal well SAGD well groups is realized; and the steam cavity is ignited in the later period, air is injected, residual oil is further combusted, the SAGD production period is prolonged, the economic benefit is improved, and the middle and later period recovery ratio of the SAGD is greatly improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic of a SAGD oil recovery process provided by the present invention;
FIG. 2 is a schematic diagram of the structure of an SAGD enhanced production well pattern employed in the SAGD production process provided in the present invention;
FIG. 3 is a schematic of a SAGD oil recovery process provided by the present invention during an expanded cavity production phase;
FIG. 4 is a schematic of the SAGD oil recovery process provided by the present invention in a nitrogen assisted SAGD oil recovery stage;
FIG. 5 is a schematic of the SAGD oil recovery process provided by the present invention during an air assisted SAGD enhanced oil recovery stage;
FIG. 6 is a schematic of the SAGD oil recovery process provided by the present invention at a terminal stage.
The reference numbers illustrate:
10. a SAGD well group; 11. injecting into a horizontal well; 12. producing a horizontal well;
20. encrypting the horizontal well; 21. a toe end.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
Example one
The invention provides an SAGD oil production method, which adopts an SAGD intensified oil production well pattern, as shown in figure 2, the SAGD intensified oil production well pattern comprises an SAGD well group 10 and an encrypted horizontal well 20, the SAGD well group 10 comprises an injection horizontal well 11 and a production horizontal well 12; as shown in fig. 1, the SAGD oil recovery process includes: step S10, after the SAGD well group 10 is preheated, injecting steam into the horizontal well 11, and producing the horizontal well 12 for oil extraction; preheating the encrypted horizontal well 20 and converting the preheated encrypted horizontal well into circulating oil extraction; step S20, after the steam cavity of the SAGD well group 10 is communicated with the steam cavity of the encryption horizontal well 20, the encryption horizontal well 20 stops circulating oil production and changes to continuous oil production; in step S30, after the residual oil in the steam chamber is ignited, air and steam are continuously injected into the horizontal encrypted well 20.
According to the SAGD oil extraction method, steam is adopted to assist gravity drainage development, the SAGD well group 10 and the encrypted horizontal well 20 are exploited simultaneously, well spacing is reduced, utilization of reserves among the SAGD well group 10 is accelerated, oil extraction speed of whole-process exploitation is improved, and rapid communication of steam cavities is facilitated.
Step S10 is a cavity expanding production stage, step S20 is a horizontal well assisted SAGD enhanced oil recovery production stage, and step S30 is an air assisted SAGD enhanced oil recovery stage. The horizontal well assists the SAGD production to effectively extract residual oil between wells, and the horizontal well assists the SAGD enhanced oil recovery production stage to reduce the steam injection amount and improve the oil-gas ratio of production. Residual oil in the air combustion steam cavity is injected and the inter-well hot oil is swept in the later period, the steam injection amount is further reduced in the air-assisted SAGD intensified oil production stage, the reduction of the exploitation cost in the whole exploitation process is realized, meanwhile, steam is injected, the residual oil on the lower portion is displaced to a production horizontal well in the SAGD well group, the crude oil continuously flows to the production well, and the recovery ratio is ensured to be up to more than 60% finally.
The SAGD oil extraction method is applied to thick oil development, well pattern adjustment is carried out by arranging the encrypted horizontal wells 20, and effective utilization of triangular zone oil layers between two adjacent horizontal well SAGD well groups 10 is realized; and the steam cavity is ignited in the later period, air is injected, residual oil is further combusted, the SAGD production period is prolonged, the economic benefit is improved, and the middle and later period recovery ratio of the SAGD is greatly improved. When the 10-day production of the SAGD well group is reduced to 4t/d, the production is ended.
Preferably, when the steam cavities of the two SAGD well groups 10 are communicated with the steam cavity of the encrypted horizontal well 20, the horizontal well assisted SAGD enhanced oil production stage is shifted.
Arranging an encrypted horizontal well 20 beside the SAGD well group 10; preferably, as shown in FIG. 2, the infill horizontal well 20 is parallel to the direction of the SAGD well groups 10 and is located intermediate two adjacent groups of SAGD well groups 10. The long pipe and the short pipe are arranged in the encrypted horizontal well 20; specifically, in step S10, the encryption horizontal well 20 is circulated to long-pipe steam injection and short-pipe oil recovery. In step S20, the encrypted horizontal well 20 continuously recovers oil to a long pipe and stops steam injection, and then changes to a short pipe continuous production.
Specifically, in step S30, igniting the residual oil in the steam cavity may be: and injecting an oxygen-enriched air slug into the horizontal well, and igniting residual oil in the steam cavity. The oxygen-enriched air slug is formed by intermittently injecting oxygen-enriched air in the form of slug.
In an embodiment of the present invention, step S40 is performed between step S10 and step S20, and step S40 includes: the horizontal well 11 is injected with nitrogen.
Step S40 is a nitrogen assisted SAGD oil recovery stage. After the SAGD well group 10 enters a steam cavity expansion stage, nitrogen is adopted for auxiliary production, and the nitrogen is used as non-condensable gas, so that the temperature of the whole steam cavity can be reduced, the heat loss of the steam cavity to a top and bottom cover layer is reduced, and the whole production oil-steam ratio of the stage is improved; meanwhile, as shown in fig. 4, the non-condensable gas carries heat more than steam, and the triangular steam cavity shape is adjusted to be an elliptical shape, which is beneficial to accelerating the establishment of the communication relationship between the steam cavity of the SAGD well group 10 and the steam cavity of the horizontal well.
Preferably, step S40 is initiated when the steam cavity of the SAGD well group 10 expands laterally 40m on top of the reservoir.
Furthermore, in step S40, the injection amount of the steam and the nitrogen gas in the gas injected into the horizontal well 11 is in the range of 1:20 to 1: 50. The nitrogen assisted SAGD production stage reduces heat loss during production, and the injection of nitrogen reduces heat loss during production. The nitrogen auxiliary cavity expansion and the liquid recovery of the encrypted horizontal well 20 are operated cooperatively, which is beneficial to accelerating the expansion of the steam cavity and improving the oil recovery speed.
In-situ combustion is an oil extraction method, in which the temperature of a thick oil layer reaches the ignition point of crude oil by using electric and chemical methods, and air or oxygen is injected into the thick oil layer to continuously combust the crude oil in the oil layer.
In one embodiment of the invention, step S30 begins when the steam cavity drain angle of SAGD well group 10 is reduced to 20 °.
The flue gas produced by the fire will supplement the energy of the stratum, and part of the super heavy oil will be cracked and thinned under the high temperature condition, thereby enhancing the underground fluidity of the crude oil. And in the later period of the SAGD, the steam cavity of the target layer has the characteristics of large volume and high temperature, the normal production of the SAGD can be maintained through the supplementary energy of the flue gas, the temperature of the steam cavity is reduced through the partial pressure effect of the flue gas, and the heat loss of the top and bottom cover layers is reduced.
Further, in step S30, steam is injected into the horizontal well 11 at a steam injection rate of less than 20 t/d.
The injection of the horizontal well 11 is performed in a low-speed steam injection mode, so that the temperature around a production well is increased, and the fluidity of the super heavy oil near a shaft is improved; secondly, because the residual oil saturation in the steam cavity is low, a stable oil wall is not easy to form, air injected by the encrypted horizontal well 20 can locally protrude, when steam is injected into the SAGD injection horizontal well 11, the oxidation of the air and crude oil is promoted, the oxygen content in the shaft of the production horizontal well 12 is controlled below the safe production limit of 5%, the safety risk is favorably controlled, and the safety of the later period of the SAGD is improved.
In the air-assisted SAGD oil recovery stage, the oxygen-enriched air slug is adopted to efficiently ignite the residual oil in the SAGD steam cavity, the subsequent air is used for continuously driving and sweeping the hot oil between wells, and a small amount of steam is injected into the injection horizontal well 11 of the SAGD well group 10, so that the risk of oxygen breakthrough is reduced, and the viscosity reduction and the oil recovery of the hot oil are facilitated.
Further, in step S30, the long-tube air injection and the short-tube steam injection are adopted in the encrypted horizontal well 20, and the steam injection rate of the long-tube air injection is 20000-50000 m3/d。
Generally, the steam injection amount in the SAGD stage is 100-200 t/d. In the oil extraction method, the steam injection amount in the later period of the SAGD is only maintained in a lower horizontal well, the daily injection amount is 20t/d, the low-cost air is injected again, the operation cost of each ton of oil is reduced by 60%, and the low-cost operation mode provides guarantee for the later-period continuous production of the SAGD. The recovery ratio is obviously improved.
Further, in step S30, injecting oxygen-enriched air with oxygen content not less than 60% into the steam cavity from the encrypted horizontal well 20, igniting residual oil in the steam cavity after continuously injecting the oxygen-enriched air for a plurality of days, and then, 20000-50000 m3And/d air injection is continuous. Preferably, both oxygen enriched air and air are injected using long tubes in the infill horizontal well 20; the steam injection rate of the oxygen-enriched air can be 50000m3The number of consecutive injections may be 5 days.
The SAGD steam contains oil saturation related to the operation temperature, the SAGD middle and later period operation pressure is generally reduced to 1-2 MPa, the residual oil saturation is only 15-20% under the corresponding 200 ℃ condition, and the oxygen with higher concentration is injected into the encrypted horizontal well 20, so that successful ignition of low oil saturation in a steam cavity is facilitated. And the residual oil swept by the steam in the steam cavity is utilized to the maximum extent by injecting air subsequently, the oxygen in the air is exhausted by burning the residual oil under the medium-high temperature condition, and the saturation degree of the residual oil in the pores is reduced to be within 5 percent.
In one embodiment of the present invention, the horizontal segment toe end 21 of the horizontal encrypted well 20 is raised. An encrypted horizontal well 20 with an upturned toe end 21 is encrypted between two adjacent SAGD well groups 10, so that the control storage capacity of a well pattern is improved, and the rapid extraction of residual oil in a triangular zone between wells is facilitated. The SAGD well group 10 and the encrypted horizontal well 20 are put into production at the same time and then produced at the same time, so that the oil extraction speed of the whole stage is improved, and the production of the whole stage can be completed in the safe production period of the steel pipe column. The upturned well body structure of the encrypted horizontal well 20 accelerates the communication between the steam cavity of the encrypted horizontal well 20 and the steam cavity of the SAGD well group 10, is favorable for assisting the SAGD well group 10 in draining oil through the encrypted horizontal well 20, and is favorable for accelerating oil recovery in middle and later periods.
In step S30, the design mode of injecting air into the upwarp-type encrypted horizontal well 20 allows air to directly enter the top of the oil reservoir, so as to realize combustion or high-temperature oxidation at the top of the oil reservoir, and form a high-concentration gas cap at the top to reduce heat loss of the steam cavity.
Further, the toe end 21 of the horizontal section of the encrypted horizontal well 20 is tilted up by 5-10 m.
In one embodiment of the present invention, in step S10, the SAGD well group 10 is preheated cyclically, and the encryption horizontal well 20 is preheated throughput.
The encryption horizontal well 20 with the upwarp design is produced in a circulating preheating mode, steam cavity expansion of the toe end 21 part is easier to realize, and the possibility of communication between the SAGD well group 10 and the steam cavity of the encryption horizontal well 20 is improved. The encryption horizontal well 20 adopts a mode of first handling preheating and then circulating oil extraction, and the effective communication between the steam cavity of the encryption horizontal well 20 and the SAGD steam cavity can be realized at a higher speed.
The SAGD oil extraction method is suitable for the middle and later period enhanced oil extraction of the SAGD of the double horizontal wells of the super heavy oil, gives transition marks at different stages, and realizes the ordered transition at different stages; the SAGD oil recovery method comprises the following steps: the method comprises a cavity expanding production stage, a nitrogen-assisted SAGD oil production stage, a horizontal well-assisted SAGD enhanced oil production stage and an air-assisted SAGD enhanced oil production stage; the method comprises 4 oil extraction stages, improves the SAGD development effect in different stages, and improves the production effect of the SAGD whole process.
In order to make the SAGD oil recovery process easier to understand, specific embodiments are illustrated below.
Basic oil deposit parameters: the oil reservoir burial depth is 250m, the porosity is 32%, the oil saturation is 75%, the net-to-wool ratio is 0.8, the horizontal permeability is 2500mD, the vertical permeability is 1250mD, the oil layer thickness is 30m, the temperature is 15 ℃, and the viscosity is 1500000mPa.s under the oil reservoir temperature condition.
A. Deploying SAGD (steam assisted gravity drainage) enhanced oil production well pattern
Deploying the SAGD intensified oil production well pattern in a production area of a heavy oil reservoir, wherein the SAGD intensified oil production well pattern at least comprises 2 SAGD well groups 10 and 1 encrypted horizontal well 20, a production horizontal well 12 is deployed at the bottom of an oil reservoir, an injection horizontal well 11 and the production horizontal well 12 are located on the same vertical plane, and the vertical distance is 4-6 m; the horizontal distance between the production horizontal well 12 and the encrypted horizontal well 20 is 40m, the well section of the horizontal section of the encrypted horizontal well 20, which is close to 50m of the toe, is upwarped, the upwarped longitudinal height is 5-10 m, and preferably, the track of the toe end 21 of the encrypted horizontal well 20 is controlled to be vertically upwarped by 10m at the last horizontal section 50 m.
B. Expanded cavity production stage
After the SAGD well group 10 is circularly preheated to realize communication, steam is continuously injected into the horizontal well 11, the dryness of a well mouth is 90%, the steam injection speed is more than 120 tons/day, the bottom pressure of the steam injection well is 4MPa, the production horizontal well 12 continuously discharges the liquid, and the pressure difference between wells of the horizontal well is controlled to be 0.2-0.5 MPa. The encrypted horizontal well 20 is subjected to steam injection continuously at the toe end 21 and liquid discharge continuously at the heel end by adopting a long pipe after being preheated, the steam injection speed of the long pipe is controlled at 60t/d, and the bottom pressure is controlled at 3.8 MPa. Wherein the SAGD steam cavity expands from the steam cavity of the horizontal well as shown in figure 3.
C. Nitrogen assisted SAGD oil recovery stage
And (3) after production for 3 years, the 10-day oil yield of the SAGD well group reaches 50t/d, the 20-day oil yield of the encryption horizontal well reaches 11t/d, when the SAGD steam cavity expands to 40m at the top of the oil layer, the steam injection amount of the SAGD is reduced by 10%, the ground volume ratio of the injection amount of steam to nitrogen is controlled to be 1: 20-1: 50, the bottom hole pressure of the injection well is 4MPa, and the bottom hole pressure of the encryption horizontal well 20 is controlled to be 3.8 MPa. A schematic of this stage is shown in figure 4.
D. Horizontal well assisted SAGD enhanced oil recovery production stage
After the steam cavity of the SAGD well group 10 is communicated with the steam cavity of the encryption horizontal well 20, steam and nitrogen are continuously injected into the injection horizontal well 11, steam injection of a long pipe of the encryption horizontal well 20 is stopped, short pipe continuous liquid production is converted, and the bottom hole pressure of the injection horizontal well 11 and the bottom hole pressure of the encryption horizontal well 20 are controlled to be 0.3-0.6 MPa.
E. Air-assisted SAGD enhanced oil recovery stage
Along with the reduction of the height of the steam cavity, the yield enters a reduction stage, when the oil drainage angle of the SAGD steam cavity is reduced to 20 degrees, namely the steam cavity is converged and then reduced by 13m from the top of an oil layer, oxygen-enriched air with the oxygen content of 60 percent is injected into the long pipe of the 20 long pipes of the encrypted horizontal well, and the injection speed is 50000m3D, continuously injecting for 5 days to ignite the oil layer, and then 20000-50000 m3And d, continuously injecting air, and reducing the steam injection speed of the SAGD injected horizontal well 11 to 20t/d, wherein the schematic diagram of the stage is shown in figures 5 and 6. When the 10-day production of the SAGD well group is reduced to 4t/d, the production is ended.
With respect to the above-described embodiments of the present invention, the prediction comparison was made with the SAGD production effect of a single dual horizontal well.
The predicted production is shown in the table below.
| Comparison of techniques | Time (year) | Recovery of oil | Oil to steam ratio |
| SAGD with single double horizontal well | 12.5 | 51.7 | 0.198 |
| The invention | 17.0 | 69.0 | 0.225 |
As shown in the table, from the production point of view, the SAGD adopting the single double horizontal well has the effective production time of 12.5 years, the final recovery rate of 51.7 percent and the oil-gas ratio of 0.198. The economic and effective production time of the invention is about 17 years, and the ultimate recovery rate is 69%. The production degree of the nitrogen-assisted SAGD oil production stage and the horizontal well-assisted SAGD intensified oil production stage is 31%, and the air-transfer-assisted SAGD intensified oil production stage is 5%. Compared with the SAGD of a single double horizontal well, the SAGD is improved by 17.3 percent. The method can be implemented in the whole SAGD process, and can also be implemented at the middle and later stages.
Example two
The invention provides an SAGD intensified oil production well pattern, as shown in figure 2, the SAGD intensified oil production well pattern comprises a ciphered horizontal well 20 and at least two SAGD well groups 10, the SAGD well group 10 comprises an injection horizontal well 11 and a production horizontal well 12; the encrypted horizontal wells 20 are arranged between two adjacent SAGD well groups 10; the toe end 21 of the horizontal section of the horizontal encrypted well 20 is raised.
The encrypted horizontal well 20 with the upward toe end 21 improves the control reserve of a well pattern and is beneficial to quickly extracting residual oil in a triangular zone between wells. The SAGD well group 10 and the encrypted horizontal well 20 are put into production at the same time and then produced at the same time, so that the oil extraction speed of the whole stage is improved, and the production of the whole stage can be completed in the safe production period of the steel pipe column. The upturned well body structure of the encrypted horizontal well 20 accelerates the communication between the steam cavity of the encrypted horizontal well 20 and the steam cavity of the SAGD well group 10, is favorable for assisting the SAGD well group 10 in draining oil through the encrypted horizontal well 20, and is favorable for accelerating oil recovery in middle and later periods.
Through the design mode of injecting air into the upwarping encrypted horizontal well 20, the air can directly enter the top of an oil reservoir, combustion or high-temperature oxidation at the top of the oil reservoir is realized, a high-concentration gas cap is formed at the top, and the heat loss of a steam cavity is reduced.
Further, the toe end 21 of the horizontal segment of the upturned encrypted horizontal well 20 is a well segment with a horizontal segment close to 50m of the toe.
The encryption horizontal well 20 with the upwarp design is produced in a circulating preheating mode, steam cavity expansion of the toe end 21 part is easier to realize, and the possibility of communication between the SAGD well group 10 and the steam cavity of the encryption horizontal well 20 is improved.
The above description is only a few embodiments of the present invention, and those skilled in the art can make various changes or modifications to the embodiments of the present invention according to the disclosure of the application document without departing from the spirit and scope of the present invention.
Claims (10)
1. The SAGD oil production method is characterized by adopting an SAGD intensified oil production well pattern, wherein the SAGD intensified oil production well pattern comprises an SAGD well group and a encryption horizontal well, and the SAGD well group comprises an injection horizontal well and a production horizontal well;
the SAGD oil recovery method comprises the following steps:
step S10, after the SAGD well group is preheated, injecting steam into the horizontal well, and producing oil from the horizontal well; preheating the encrypted horizontal well and converting the preheated encrypted horizontal well into circulating oil extraction;
step S20, after the steam cavity of the SAGD well group is communicated with the steam cavity of the encryption horizontal well, the encryption horizontal well stops circulating oil production and changes to continuous oil production;
and step S30, after residual oil in the steam cavity is ignited, continuously injecting air and steam into the encrypted horizontal well.
2. The SAGD oil recovery method of claim 1, wherein step S40 is performed between the step S10 and the step S20, the step S40 comprising: and injecting nitrogen gas along with the injection horizontal well.
3. The SAGD oil recovery method of claim 2, wherein the step S40 is started when the steam cavity of the SAGD well string is expanded laterally by 40m on top of the reservoir;
when the steam cavity drain angle of the SAGD well group is reduced to 20 °, the step S30 is started.
4. The SAGD oil recovery method according to claim 2, wherein in step S40, the injection amount of steam and nitrogen in the gas injected into the horizontal well is in the range of 1:20 to 1:50 on the ground volume ratio.
5. The SAGD oil recovery method of claim 3, wherein in step S30, the injection horizontal well injects steam at a rate of less than 20 t/d.
6. The SAGD oil recovery method of claim 5, wherein long and short pipes are provided in the infill horizontal well; in the step S30, the long-pipe air injection and the short-pipe steam injection are adopted in the encrypted horizontal well, and the steam injection rate of the long-pipe air injection is 20000-50000 m3/d。
7. The SAGD oil recovery method of claim 5, wherein in step S30, oxygen-enriched air with oxygen content not less than 60% is injected into the steam chamber from the horizontal infill well, and after a plurality of consecutive days, residual oil in the steam chamber is ignited.
8. The SAGD oil recovery method of claim 1, wherein the horizontal segment toe end of the infill horizontal well is upwarped.
9. The SAGD oil recovery method of claim 8, wherein in step S10, the preheating mode of the SAGD well group is circulation preheating, and the preheating mode of the encryption horizontal well is throughput preheating.
10. The SAGD intensified oil production well pattern is characterized by comprising a ciphered horizontal well and at least two SAGD well groups, wherein each SAGD well group comprises an injection horizontal well and a production horizontal well;
the encrypted horizontal well is arranged between two adjacent SAGD well groups; the toe end of the horizontal section of the encrypted horizontal well is upwarped; the toe end of the horizontal section of the encrypted horizontal well is upwards tilted by 5-10 m;
and the toe end of the horizontal section of the upturned encrypted horizontal well is a well section with the horizontal section close to the toe by 50 m.
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