Well pattern combination method for using super heavy oil difficult-to-exploit reserves

Abstract

The invention relates to a well pattern combination method using super heavy oil difficult-to-exploit reserves, and belongs to the technical field of oil exploitation. The method comprises the following specific steps: step 1, analyzing a main reason that the vertical well is difficult to use in development; 2, when the development of the vertical well is poor, horizontal well development is deployed; and thirdly, the steam injection mode is adjusted on the basis of the second step. According to the method, fishbone horizontal well and horizontal well vertical staggered superposition type well pattern deployment is adopted, meanwhile, a branch horizontal well and horizontal well staggered superposition combined huff and puff mode is created on the matched technology, the one-time tubular column pump circulation steam injection technology is assisted, steam cavity balanced expansion is achieved, overall heating of an oil reservoir is facilitated, and the oil reservoir quality is improved. And the transformation of the steam wave and volume from'point 'to'body' is accelerated, and the oil reservoir temperature is gradually increased, so that the steam development effect is improved, and the utilization of the difficult-to-exploit reserves of the super heavy oil reservoir is realized.

Description

Technical Field

[0001] The invention relates to a well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil, belonging to the technical field of petroleum exploitation. Background Art

[0002] The XX fault block of the XX oilfield is located in the eastern steep slope of the western depression of the Liaohe Depression and the northern part of the southern plunge zone of the central uplift. Geographically, it is located 10 km southeast of Panjin City, Liaoning Province. The southern part of the block is the W60 block, and the development target layer is the third segment of the Shahejie Formation of the Paleogene. The viscosity of the 50℃ degassed crude oil is greater than 20×10 4 mPa.s, is a super heavy oil reservoir with structural bottom water. In 1997, this block was developed with a well spacing of 100m, a square well pattern, and a set of vertical wells in the development layer. A total of 14 vertical wells were drilled, and 10 were put into production (4 were difficult to use and not put into production). The vertical wells put into production could not be injected with steam normally, and the reserves were in an unused state. There is an urgent need for a way to use the difficult-to-use reserves of super heavy oil reservoirs.

[0003] This difficult-to-recover block has the contradiction of heavy oil and deep burial. The conventional steam huff-and-puff method requires multiple rounds of steam injection to develop this type of difficult-to-recover reserves. The oil wells in the block can only be put into normal production when the heat accumulates to a certain level (4-5 rounds of steam injection cycle, about 12,000-20,000 cubic meters of steam are injected). It has the characteristics of low production capacity and poor economic benefits. After years of technical research and practice, XX Oilfield has successively developed side drilling, horizontal well and other drilling technologies that are widely used in super-heavy oil reservoirs to improve the recovery of difficult-to-recover reserves. At present, for super-heavy oil reservoirs, especially the 50℃ degassed crude oil with a viscosity greater than 20×10 4 For oil reservoirs with a flow rate of mPa.s, ordinary horizontal wells cannot realize the utilization of difficult-to-recover reserves due to their small heating radius. Summary of the invention

[0004] In order to solve the problem of low utilization rate of hard-to-recover reserves of extra-heavy oil, the present invention discloses a well network combination method for utilizing hard-to-recover reserves of extra-heavy oil, which adopts a well network deployment of vertically staggered and stacked herringbone horizontal wells and horizontal wells, and at the same time creates a "staggered and stacked branch horizontal wells and horizontal wells" combined throughput mode in supporting process technology, assists in a primary tubing pump circulation steam injection technology, realizes balanced expansion of the steam chamber, is beneficial to the overall heating of the oil reservoir, accelerates the transformation of the steam wave volume from "point" to "body", gradually increases the temperature of the oil reservoir, and realizes the utilization of hard-to-recover reserves of extra-heavy oil reservoirs.

[0005] The technical solution adopted by the present invention is a well pattern combination method for utilizing the hard-to-recover reserves of extra-heavy oil, and the specific steps are as follows:

[0006] Step 1: Analyze the main reasons why vertical well development is difficult to mobilize;

[0007] Step 2: Vertical well development is poor, so horizontal well development is deployed;

[0008] Step three, adjust the steam injection method based on step two.

[0009] Furthermore, the step 1 specifically includes first obtaining a deep ultra-heavy oil reservoir according to the reservoir profile; secondly analyzing the reasons for the difficulty in producing the deep ultra-heavy oil reservoir according to its characteristics. Specifically, the burial depth of the thermally recovered heavy oil is greater than 900m and less than 1450m. According to the heavy oil classification standard, the viscosity is greater than 10×10 4 mPa.s, which belongs to deep extra-heavy oil reservoirs; due to the deep extra-heavy oil reservoirs are buried deep, poor physical properties, thicker oil products and long distances between wells, ordinary horizontal wells have a small heating radius, which makes it difficult for the reservoir fluid temperature to reach the production temperature, and the wells cannot be connected to overcome the starting pressure gradient, making it difficult to change the rheological properties of the crude oil, which is the main reason for the difficulty in production.

[0010] Furthermore, in the step 2, the well pattern is selected by adopting a three-dimensional mesh structure to realize the development mode from point to body. The three-dimensional mesh structure adopts a well pattern deployment of herringbone horizontal wells and horizontal wells vertically staggered and stacked.

[0011] Furthermore, the herringbone horizontal well and horizontal well vertically staggered overlapping well pattern is specifically to deploy horizontal wells and herringbone horizontal wells at intervals between adjacent vertical wells, and the main well of the herringbone horizontal well is also provided with a plurality of branch wells, and the wellbore of each branch well serves as an oil drainage channel.

[0012] The horizontal well and the herringbone well have a well spacing of 100m, and the branch wells of the horizontal well and the herringbone well have a well spacing of 50m.

[0013] The contact surface area between the wells and the oil layer is increased by vertically staggered and stacked herringbone horizontal wells and the swept volume of steam is increased.

[0014] Furthermore, in the step three, based on the poor quality of steam injection in vertical wells, the boiler outlet pressure being greater than 19 MPa, the low bottom hole dryness and the situation where steam injection cannot be injected, a combined throughput mode of "staggered overlapping of branch horizontal wells and horizontal wells" is created, and at the same time, a tubing pump is assisted to circulate steam injection to achieve balanced expansion of the steam chamber, accelerate the transformation of the steam wave volume from "point" to "body", and gradually increase the reservoir temperature to the level of production temperature.

[0015] Furthermore, the activation temperature is at least 70°C.

[0016] The present invention discloses a well network combination method for utilizing hard-to-recover reserves of ultra-heavy oil. The method has the beneficial effects of adopting a well network deployment of vertically staggered and stacked herringbone horizontal wells and horizontal wells, while creating a combined throughput mode of "staggered and stacked branch horizontal wells and horizontal wells" in supporting process technology, assisting a primary tubing pump circulation steam injection technology, realizing balanced expansion of the steam chamber, being beneficial to the overall heating of the oil reservoir, accelerating the transformation of the steam wave volume from "point" to "body", gradually increasing the temperature of the oil reservoir, thereby improving the steam development effect, and realizing the utilization of hard-to-recover reserves of ultra-heavy oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 The figure shows a schematic diagram of the vertically staggered and stacked well pattern deployment of herringbone horizontal wells and horizontal wells in Example 1 of the present invention;

[0019] Figure 2 Shown is a scatter plot of steam stimulation production effects of horizontal wells of different lengths in the W60 fault block.

[0020] As shown in the figure: 1. The first vertical well; 2. The second vertical well; 3. The third vertical well; 4. The fourth vertical well; 5. The first herringbone horizontal well; 6. The second herringbone horizontal well; 7. The branch well; 8. The first horizontal well.

[0021] Specific implementation methods

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In order to further understand the content of the present invention, the present invention is further described below in conjunction with specific implementation methods.

[0024] Example 1: Figure 1 As shown, a well pattern combination method for utilizing hard-to-recover reserves of ultra-heavy oil specifically includes:

[0025] Step one, analyzing the main reasons why vertical well development is difficult to use; specifically, firstly, obtaining deep ultra-heavy oil reservoirs based on well data; secondly, analyzing the reasons why deep ultra-heavy oil reservoirs are difficult to use based on their characteristics.

[0026] The test results of Block XX S3 were selected. The reservoir has a burial depth of 1360-1450m, a permeability of 200-600mD, a porosity of 18%, and a viscosity of degassed crude oil at 50℃ greater than 24×10 4 mPa.s, which belongs to deep extra-heavy oil reservoirs; due to the deep extra-heavy oil reservoirs are buried deep, poor physical properties, thicker oil products and long distances between wells, ordinary horizontal wells have a small heating radius, which makes it difficult for the reservoir fluid temperature to reach the production temperature, and the wells cannot be connected to overcome the starting pressure gradient, making it difficult to change the rheological properties of the crude oil, which is the main reason for the difficulty in production.

[0027] Step 2: Vertical well development is poor, so horizontal well development is deployed;

[0028] Specifically, the well network and well type selection: a three-dimensional mesh structure is adopted to realize the development mode from point to body. The three-dimensional mesh structure adopts the vertical staggered and superimposed well network deployment of fishbone horizontal wells and horizontal wells. In this embodiment, in order to facilitate the understanding of those skilled in the art, the fishbone horizontal wells and horizontal wells of 4 adjacent vertical wells are listed in the vertical staggered and superimposed well network deployment, specifically, the first fishbone horizontal well 5 is deployed between the first vertical well 1 and the second vertical well 2, and the first fishbone horizontal well 5 is also provided with 4 branch wells 7, and the 4 branch wells 7 wellbores are used as oil drainage channels; the first horizontal well 8 is deployed between the second vertical well 2 and the third vertical well 3, and the first horizontal well 8 and the first fishbone horizontal well 5 wellbores adopt a well spacing of 100m, and the first horizontal well 8 and the branch well 7 of the first fishbone horizontal well 5 adopt a well spacing of 50m, and so on, the second fishbone horizontal well 6 is deployed between the third vertical well 3 and the fourth vertical well 4, and so on.

[0029] like Figure 2As shown, according to the scatter plot of steam production effects of horizontal wells of different lengths in the W60 block, a long horizontal section is prone to uneven use and difficult to control. The existing horizontal well length is 240-900m. As the length of the horizontal well increases, the cumulative oil production per unit length shows a decreasing trend. Therefore, the horizontal well section should not be too long. The extension length of the horizontal section of the fishbone horizontal well bore is 350 meters, and the extension length of the horizontal section of the fishbone horizontal well branch well 7 is 120 meters, so the distance from the vertical well is 50 meters. The contact surface area between the well and the oil layer is increased by vertically staggered and stacked well patterns of fishbone horizontal wells and horizontal wells, and the swept volume of steam is increased. The oil layer of this block is the thickest in the middle on the plane (at point 6A of the second fishbone horizontal well), and gradually thins to the northeast. The oil-bearing well section is 40-60m long in the vertical direction, and the effective thickness of the oil layer is 18m. Among them, the sandstone group of the 1st oil layer group of the 3rd section of Shahejie Formation I is developed in a continuous manner, and the oil layers are generally 25-35m, with the thickest at the first vertical well 1. The sandstone group of the 2nd oil layer group of the 3rd section of Shahejie Formation I is thinner, generally 15-25m, and the thickest is at the first herringbone horizontal well 5. According to the development characteristics of the oil reservoir, the target layer of the deployment of the first vertical well 1 and the second vertical well 2 is the sandstone group of the 1st oil layer group of the 3rd section of Shahejie Formation I, and the target layer of the deployment of the third vertical well 3, the fourth vertical well 4 and the first herringbone horizontal well 5 is the sandstone group of the 2nd oil layer group of the 3rd section of Shahejie Formation I. This well configuration relationship not only takes into account the reservoir development, but also the stratified development can improve the utilization of reserves.

[0030] Step three: adjust the steam injection method based on the vertically staggered and stacked well pattern deployment of herringbone horizontal wells and horizontal wells.

[0031] Specifically, based on the poor quality of steam injection in vertical wells, the boiler outlet pressure is greater than 19MPa, the bottom hole dryness is low, and there are situations where steam injection cannot be injected, a combined throughput method of "staggered branch horizontal wells and horizontal wells" is created, and steam injection is carried out by combining herringbone horizontal wells and horizontal wells. The branch well 7 of the herringbone horizontal well is used to expand the contact area between steam and oil layer, and the branch well 7 of the herringbone horizontal well is combined with adjacent vertical wells for steam injection, so as to improve the thermal connectivity and the steam absorption capacity of the oil layer; when injecting steam, a single column pump is used to circulate steam injection, which can reduce frequent operations, realize continuous throughput, and quickly form a small steam chamber. At the same time, the steam thermal energy utilization rate is high, and the throughput effect is improved. By deploying multiple horizontal wells and herringbone horizontal wells between adjacent rows of vertical wells, the well spacing is reduced, the thermal connectivity is improved, the steam absorption capacity of the oil layer is improved, and the temperature can be quickly and stably maintained at the required temperature for use.

[0032] This method has been applied to actual well conditions. There are 15 oil wells in the block, 10 of which are in operation and 5 are horizontal wells with throughput development. The cycle oil production is more than 1,000 tons. At the same time, 5 vertical wells are put into use on the basis of establishing a certain temperature field in the region. The cycle oil production is greater than 600 tons, the stage oil production is 54,100 tons, and the stage recovery rate is 10.5%, which is 7.5% higher than the recovery rate in the vertical well production stage.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A well pattern combination method for utilizing hard-to-recover reserves of ultra-heavy oil, the specific steps are as follows: Step 1: Analyze the main reasons why vertical well development is difficult to mobilize; Step 2: Vertical well development is poor, so horizontal well development is deployed; Step three, adjust the steam injection method based on step two.

2. A well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 1, characterized in that: Step one specifically includes firstly obtaining a deep ultra-heavy oil reservoir according to the reservoir overview; and secondly analyzing the reasons why the deep ultra-heavy oil reservoir is difficult to produce according to its characteristics.

3. A well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 2, characterized in that: The identification of deep ultra-heavy oil reservoirs is specifically that the burial depth of thermally recovered heavy oil is greater than 900m and less than 1450m. According to the classification standard of heavy oil, the viscosity is greater than 10×10 4 mPa.s.

4. A well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 1, characterized in that: The specific step in step two is to select the well pattern and well type: adopt a three-dimensional network structure to realize the development mode from point to body.

5. A well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 4, characterized in that: The three-dimensional network structure adopts the vertically staggered and superimposed well pattern deployment of herringbone horizontal wells and horizontal wells.

6. A well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 5, characterized in that: The herringbone horizontal wells and horizontal wells are vertically staggered and stacked in a well pattern, specifically, horizontal wells and herringbone horizontal wells are deployed at intervals between adjacent vertical wells, and the main well of the herringbone horizontal well is also provided with a plurality of branch wells (7), and the wellbore of each branch well (7) serves as an oil drainage channel.

7. A well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 6, characterized in that: The horizontal well and the herringbone horizontal well have a well spacing of 100 m, and the horizontal well and the branch well (7) of the herringbone horizontal well have a well spacing of 50 m.

8. The well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 1, characterized in that: In step three, based on the poor quality of steam injection in vertical wells, boiler outlet pressure greater than 19 MPa, low bottom hole dryness and the situation where steam injection cannot be injected, a combined throughput mode of "staggered overlapping of branch horizontal wells and horizontal wells" is created, and a tubing pump is assisted to circulate steam injection to achieve balanced expansion of the steam chamber, accelerate the transformation of steam wave volume from "point" to "body", and gradually increase the reservoir temperature to the level of producing temperature.

9. A well pattern combination method for utilizing hard-to-recover reserves of extra-heavy oil according to claim 8, characterized in that: The operating temperature is at least 70°C.

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