Composite rapid preheating method for deep thickened oil drainage

Abstract

The invention discloses a deep thickened oil drainage composite rapid preheating method which comprises the following steps: step 101, drilling a plurality of vertical wells in the middle-upper part of an oil layer, and drilling a horizontal well at the bottom of the oil layer among the plurality of vertical wells; 102, variable-density perforation is conducted on the vertical well according to the longitudinal heterogeneity of the reservoir; 103, water vapor is injected into the vertical well and the horizontal well at high strength at the same time at the level slightly higher than the stratum fracture pressure; 104, after the well is soaked for a period of time, water is drained, and the next round of micro-fracturing high-strength steam injection is started; and 105, the temperature between the multiple vertical wells and the temperature between the multiple vertical wells and the horizontal well are monitored to exceed the temperature needed when crude oil in an oil layer reaches Newtonian fluid, and after preheating is finished, the vertical wells and the horizontal well enter the driving and discharging composite production stage. And rapid and uniform preheating between injection and production wells is realized, so that a favorable guarantee is provided for success of a driving and discharging composite production stage.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield development, and in particular relates to a composite rapid preheating method for deep-layer heavy oil flooding. Background Art

[0002] The proven reserves of heavy oil in the eastern part of Shengli Oilfield are 620 million tons, of which 575 million tons have been used so far. The oil reservoir is deep, thin and has high water energy. The heavy oil in the eastern part of Shengli is mainly developed by steam huff and puff, with a single development method and low recovery rate. It is necessary to change the method to significantly increase the recovery rate, but the two main technologies for increasing the recovery rate of heavy oil, steam flooding and SAGD, have limitations in deep heavy oil reservoirs. Steam flooding is mainly based on displacement, and the recovery rate can reach 40-60%, but the oil-gas ratio is relatively low; SAGD is mainly based on gravity drainage, and the recovery rate can reach 50-70%, and the oil-gas ratio is relatively high. Shengli heavy oil is deeply buried, and it is difficult to expand the steam cavity under low dry high pressure, and the adaptability of SAGD technology is poor. The composite flooding and drainage technology has the advantages of both. Its recovery factor is close to that of steam drive and SAGD, and its oil-gas ratio is higher than that of steam drive. Its requirements for reservoir burial depth and thickness are lower than those of SAGD, and its adaptable reservoir oil property range is wider than that of steam drive. It can be used as an effective replacement technology after high-cycle throughput of deep heavy oil, greatly improving the recovery factor of Shengli heavy oil.

[0003] Patent application CN113863908A discloses a method for improving the uniformity of steam injection in SAGD horizontal wells. The method includes: for double-tube steam injection: extending the length of the short pipe of the steam injection well to 1 / 6 to 1 / 2 of the length of the horizontal section of the horizontal well; for multi-point steam injection: setting the steam injection points of the steam injection well to 10 to 40 and / or extending the length of the oil pipe of the production well to 1 / 6 to 1 / 2 of the length of the horizontal section of the horizontal well. By changing the pipe string structure, an effective method for improving the uniformity of SAGD horizontal wells is formed. This method is suitable for SAGD production methods using steam injection in horizontal wells, but cannot solve the technical problem of uniformity of steam injection in vertical wells in the composite production method using deep heavy oil flooding.

[0004] Invention patent CN104165046B is an enhanced method for rapid and uniform SAGD startup. It includes: step 1, drilling and completing the SAGD well in the rock formation; step 2, adjusting the well to create stress conditions that are conducive to the formation of an expansion zone; step 3, injecting a stimulant into one or both of the two wells at a pressure greater than the in-situ minimum stress of the rock formation to begin connecting the expansion zone of the SAGD well, and continuously injecting the stimulant into the first well of the two wells while maintaining the target pressure in the second well of the two wells, so that the expansion zone spreads uniformly along the length of the well. The invention provides a method for establishing a laterally continuous, vertically guided expansion zone connecting two SAGD wells, which requires a complex downhole packer system to manage the uniform lateral extension of the expansion zone along the length of the SAGD well, has high process requirements, and is difficult to implement.

[0005] From the development practice of steam flooding and SAGD, in order to ensure the development effect, the reservoir must be preheated before the formal transition to the steam flooding and SAGD production stage to form an effective thermal connection between the injection and production wells. Before steam flooding, multiple rounds of single well throughput are generally used to form a certain thermal connection between the wells, but this preheating method has the problem of unevenness. SAGD generally uses steam injection cycle preheating, but this preheating method has the problems of long preheating time and high steam consumption.

[0006] Therefore, a new preheating method is urgently needed to overcome the defects of existing preheating technologies for steam flooding and SAGD, quickly achieve uniform and effective thermal connectivity between deep heavy oil flooding and composite injection and production wells, and provide guarantee for subsequent flooding and composite production. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a deep-layer heavy oil flooding composite rapid preheating method.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A deep layer heavy oil flooding composite rapid preheating method comprises the following steps:

[0010] Step 101: drilling a plurality of vertical wells in the middle and upper part of the oil layer, and drilling a horizontal well at the bottom of the oil layer between the plurality of vertical wells;

[0011] Step 102: performing variable density perforation on the vertical well according to the vertical heterogeneity of the reservoir;

[0012] Step 103: injecting water vapor into the vertical well and the horizontal well at a level slightly higher than the formation fracture pressure at high intensity;

[0013] Step 104: After soaking the well for a period of time, drain the water and start the next round of micro-fracturing high-intensity steam injection;

[0014] Step 105: Monitor that the temperatures between several vertical wells and between them and the horizontal wells all exceed the temperature required for the oil in the reservoir to become a Newtonian fluid, and the preheating is completed and the flooding and drainage composite production stage is entered.

[0015] Preferably, in step 101, two rows of vertical wells are drilled in the upper part of the oil layer, and one horizontal well is drilled at the bottom of the oil layer between the two rows of vertical wells.

[0016] Preferably, in step 101, the vertical trajectory of the completed horizontal well is guaranteed to be horizontal.

[0017] Preferably, in step 101, the trajectory of the horizontal section on the horizontal well plane cannot deviate from the center of the target; the well inclination and full angle change rate of the horizontal section above 50m vertical depth meet the supporting requirements of the flooding and drainage composite process.

[0018] Preferably, the completion and sand control technologies of the vertical wells and horizontal wells also meet the composite flooding and drainage requirements.

[0019] Preferably, in step 102, the vertical well is transported by cable and perforated at near-balanced pressure.

[0020] Preferably, in step 102, the pore density is reduced at the top of the oil layer and at the bottom where the physical properties are better.

[0021] Preferably, in step 102, all-round spiral perforation is adopted and perforation is carried out by oil pipe transportation.

[0022] Preferably, in step 103, a supercritical steam injection boiler is used to inject steam into the vertical well and the horizontal well simultaneously.

[0023] Preferably, in step 103, the steam injection pressure range is 2 to 3 MPa higher than the formation fracture pressure.

[0024] Preferably, in step 103, the steam injection intensity of the vertical wells and horizontal wells is increased to twice the conventional steam throughput, further accelerating the thermal connection between the injection and production wells.

[0025] Preferably, in step 104, the wells are shut down for a period of time to allow sufficient heat exchange between the injected steam and the oil reservoir, and then each well simultaneously recovers condensed water generated by the exchange of heat between the injected steam and the oil reservoir.

[0026] Preferably, in step 104, in order to shorten the preheating time, a higher liquid production intensity is used for recovery, and when the cumulative recovered water volume reaches the water equivalent of the injected steam, the next round of high-intensity combined injection and production is started.

[0027] Preferably, in step 105, old wells between vertical wells and between vertical wells and horizontal wells are used as observation wells to monitor the oil layer temperature, ensuring that there is at least one observation well between each vertical well and horizontal well.

[0028] Preferably, in step 105, when the temperatures monitored by all observation wells reach the temperature required for the crude oil in the reservoir to become a Newtonian fluid, it indicates that good thermal connectivity has been achieved between the injection and production wells, and the flooding and drainage composite production stage can be entered.

[0029] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0030] In the present invention, on the basis of conventional throughput preheating, the steam chamber is expanded as evenly in the plane and in the longitudinal direction as possible through horizontal well drilling trajectory control, segmented completion technology, and vertical well variable density perforation. At the same time, high-intensity synchronous steam injection and synchronous short-time recovery of condensed water by micro-fracturing are used to achieve rapid and uniform preheating between injection and production wells, thereby providing favorable guarantees for the success of the flooding and drainage composite production stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of the present invention;

[0032] Figure 2 It is a schematic diagram of the trajectory of the horizontal well steady-inclination section in a specific embodiment of the present invention;

[0033] Figure 3 This is a diagram of a horizontal well segmented filling sand control string in a specific embodiment of the present invention;

[0034] Figure 4 A vertical well completion string diagram in a specific embodiment of the present invention;

[0035] Figure 5 It is a well location deployment diagram of the flooding and drainage composite well group in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following is combined with Figure 1-5 , further illustrating a specific implementation of a deep layer heavy oil flooding composite rapid preheating method of the present invention. A deep layer heavy oil flooding composite rapid preheating method of the present invention is not limited to the description of the following embodiments.

[0037] Embodiment 1:

[0038] A composite rapid preheating method for deep heavy oil flooding, such as Figure 1 As shown, the following steps are included:

[0039] Step 101: drilling a plurality of vertical wells in the middle and upper part of the oil layer, and drilling a horizontal well at the bottom of the oil layer between the plurality of vertical wells;

[0040] Step 102: performing variable density perforation on the vertical well according to the vertical heterogeneity of the reservoir;

[0041] Step 103: injecting water vapor into the vertical well and the horizontal well at a level slightly higher than the formation fracture pressure at high intensity;

[0042] Step 104: After soaking the well for a period of time, drain the water and start the next round of micro-fracturing high-intensity steam injection;

[0043] Step 105: Monitor that the temperatures between several vertical wells and between them and the horizontal wells all exceed the temperature required for the oil in the reservoir to become a Newtonian fluid, and the preheating is completed and the flooding and drainage composite production stage is entered.

[0044] Embodiment 2:

[0045] A deep heavy oil flooding composite rapid preheating method, the other steps are similar to those of Example 1, further, in step 101, two rows of vertical wells are drilled in the upper part of the oil layer, and a horizontal well is drilled at the bottom of the oil layer between the two rows of vertical wells.

[0046] Furthermore, in step 101, the vertical trajectory of the completed horizontal well is guaranteed to be horizontal.

[0047] Furthermore, in step 101, the trajectory of the horizontal section on the horizontal well plane cannot deviate from the center of the target; the well inclination and full angle change rate of the horizontal section above 50m vertical depth meet the requirements of the flooding and drainage composite process.

[0048] Furthermore, the completion and sand control technologies for vertical and horizontal wells also meet the composite requirements of flooding and drainage.

[0049] Embodiment 3:

[0050] A composite rapid preheating method for deep heavy oil drainage, wherein other steps are similar to those of Example 1. Further, in step 102, the vertical well is transported by cable and perforated at near-balanced pressure.

[0051] Furthermore, in step 102, the pore density is reduced at the top of the oil layer and at the bottom where the physical properties are better.

[0052] Furthermore, in step 102, all-round spiral perforation and oil pipe transportation are used for perforation.

[0053] Embodiment 4:

[0054] A composite rapid preheating method for deep heavy oil drainage, wherein other steps are similar to those of Example 1. Further, in step 103, a supercritical steam injection boiler is used to simultaneously inject steam into the vertical well and the horizontal well.

[0055] Furthermore, in step 103, the steam injection pressure range is 2 to 3 MPa higher than the formation fracture pressure.

[0056] Furthermore, in step 103, the steam injection intensity of the vertical wells and horizontal wells is increased to twice the conventional steam throughput, further accelerating the thermal connection between the injection and production wells.

[0057] Embodiment 5:

[0058] A composite rapid preheating method for deep heavy oil drainage, wherein the other steps are similar to those of Example 1. Further, in step 104, the well is shut down for a period of time to allow the injected steam and the oil reservoir to fully exchange heat, and then each well simultaneously recovers condensed water generated after the injected steam exchanges heat with the oil reservoir.

[0059] Furthermore, in step 104, in order to shorten the preheating time, a higher liquid production intensity is used for recovery. When the cumulative recovered water volume reaches the water equivalent of the injected steam, the next round of high-intensity combined injection and production is started.

[0060] Embodiment 6:

[0061] A deep heavy oil flooding composite rapid preheating method, the other steps are similar to those of Example 1. Further, in step 105, old wells between vertical wells and between vertical wells and horizontal wells are used as observation wells to monitor the oil layer temperature, ensuring that at least one observation well is provided between each vertical well and horizontal well.

[0062] Furthermore, in step 105, when the temperatures monitored by all observation wells reach the temperature required for the crude oil in the reservoir to become a Newtonian fluid, it indicates that good thermal connectivity has been achieved between the injection and production wells, and the flooding and drainage composite production stage can be entered.

[0063] Embodiment 7:

[0064] A composite rapid preheating method for deep heavy oil flooding, such as Figure 1 As shown, Figure 1 The present invention is a flow chart of a composite rapid preheating method for deep heavy oil drainage.

[0065] In step 101, two rows of vertical wells are drilled in the middle and upper part of the oil layer, and one horizontal well is drilled at the bottom of the oil layer between the two rows of vertical wells. In order to ensure the stable expansion of the steam chamber in the flooding and drainage composite stage, the horizontal section trajectory in the vertical direction must be kept horizontal; since the horizontal well is drilled between the two rows of vertical wells, in order to ensure a reasonable distance between the injection and production wells, the horizontal section trajectory in the plane cannot deviate from the center of the target; the well inclination and full angle change rate of the horizontal section above 50m vertical depth must meet the requirements of the flooding and drainage composite process. The completion and sand control processes of the two rows of vertical wells and one horizontal well must also meet the flooding and drainage composite requirements.

[0066] In a possible implementation, two rows of vertical wells are drilled in the middle and upper part of the target reservoir, and one horizontal well is drilled at the bottom of the reservoir between the two rows of vertical wells. The vertical error of the horizontal section trajectory from the center of the target is no more than ±1.0 m, and the horizontal section trajectory from the center of the target is no more than ±2.0 m. The well inclination is less than 50° above the vertical depth of the horizontal section by 50 m, and the full angle change rate is controlled within 3° / 25 m. Figure 2 The horizontal well was completed by three openings. 1 / 2 Technical Casing Suspension 5 1 / 2 composite wire-wrapped screen completion, horizontal open hole screen segmented completion and segmented filling for sand control, such as Figure 3 As shown; the second row of vertical wells adopt casing cementing perforation completion and extrusion filling for sand control. The process enters step 102.

[0067] Furthermore, in step 102, two rows of vertical wells are transported by cables and perforated at near-balanced pressure to avoid contaminating the reservoir; considering steam overburden and longitudinal heterogeneity, the pore density is reduced at the top of the oil layer and the bottom with better physical properties to achieve a balanced steam absorption profile and enhance the expansion of the steam chamber; all-round spiral perforation is used and perforation is carried out by tubing.

[0068] In one possible implementation, cable transmission is used, and the near-ground formation balance pressure of 11.5 MPa is used to perforate the three layers of the steam injection vertical well of the flooding composite well group in the target block. The perforating gun type is 127 gun, and the bullet type is selected according to the physical properties and water flooding degree of the three layers, 127 deep penetration, 127BH, and 127 efficiency enhancement, respectively, with a hole density of 16 to 40 holes / m, a full-range spiral hole arrangement in the perforation phase, and perforation by tubing transmission. The specific perforation plan on site is shown in Table 1. The process enters step 103.

[0069] Table 1 Elastic performance parameters of perforating guns in vertical wells with steam injection in a flooding composite well group in a certain block

[0070]

[0071] Furthermore, in step 103, a supercritical steam injection boiler is used to simultaneously inject steam into two rows of vertical wells and one horizontal well, and the steam injection pressure is controlled within a range of 2 to 3 MPa higher than the formation fracture pressure, in order to generate a number of microcracks in the formation, which is conducive to faster thermal connection between the injection and production wells. At the same time, the steam injection intensity of the vertical wells and horizontal wells is increased to twice that of conventional steam throughput, which can further accelerate the thermal connection between the injection and production wells.

[0072] In a possible implementation, after the fracturing construction test, the target reservoir formation fracture pressure is 23.5MPa, and two 23t 26MPa supercritical boilers are used to simultaneously inject steam into two rows of vertical wells and one horizontal well of the flooding composite well group, and the steam injection rate of each well is maintained at 4-5t / h. The steam injection intensity of the vertical well should reach about 200-250t / m, and the converted cycle gas injection volume is about 4000-5000t. The steam injection intensity of the horizontal well should reach about 15-20t / m, and the converted cycle gas injection volume is about 5000-6000t. The entire flooding composite well group injects a total of 33,000t of steam in one cycle, which takes about 30 days. The process enters step 104.

[0073] Furthermore, in step 104, the wells are kept idle for a period of time to allow the injected steam and the reservoir to fully exchange heat, and then the condensed water generated by the injected steam exchanging heat with the reservoir is simultaneously recovered from each well. In order to shorten the preheating time, a higher liquid production intensity is used for recovery, and when the cumulative recovered water volume reaches the water equivalent of the injected steam, the next round of micro-fracturing high-intensity combined injection and production begins.

[0074] In a possible implementation, after the wells are shut down for 4-5 days, the wells are opened to recover condensed water. The recovery rate of vertical wells is 120 t / d, and the recovery rate of horizontal wells is 200 t / d. After about 40 days of recovery, the cumulative recovery water volume can reach the water equivalent of the injected steam, and the next round of micro-fracturing high-intensity combined injection and production is started, and the operations of steps 103 and 104 are repeated. The process enters step 105.

[0075] Furthermore, in step 105, old wells between vertical wells and between vertical wells and horizontal wells are used as observation wells to monitor the temperature of the oil layer, and at least one observation well is ensured between each vertical well and horizontal well. When the temperature monitored by all observation wells reaches the temperature required for the oil layer crude oil to be converted into Newtonian fluid, it indicates that good thermal connectivity has been achieved between the injection and production wells, and the flooding and drainage composite production stage can be entered.

[0076] In a possible implementation, six old wells between the vertical wells and the horizontal wells in the target area support stop flooding composite well group are used as temperature and pressure observation wells, such as Figure 5 At the same time, according to the rheological curve of crude oil in the target area, the required temperature for the crude oil to be converted into Newtonian fluid is 70°C. After two rounds of micro-fracturing and high-intensity combined injection and production in the two rows of vertical wells and one horizontal well in the flooding and drainage composite well group, the temperatures monitored by the six observation wells all exceeded 70°C, and comprehensive thermal connectivity has been achieved between the vertical wells and the horizontal wells, and the flooding and drainage composite production stage can be entered at this time.

[0077] In summary:

[0078] On the basis of conventional throughput preheating, the present invention uses horizontal well drilling trajectory control and segmented completion technology and vertical well variable density perforation to make the steam chamber expand evenly in the plane and vertical direction as much as possible. At the same time, through micro-fracturing high-intensity synchronous steam injection and synchronous short-time condensate recovery, rapid and uniform preheating between injection and production wells is achieved, thereby providing favorable guarantee for the success of the flooding and drainage composite production stage.

[0079] Compared with the existing SAGD steam injection cycle preheating, the preheating method provided by the present invention can shorten the preheating time by 50%, reduce the steam consumption by 80%, and improve the preheating uniformity by nearly 25% compared with the steam drive throughput preheating.

[0080] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A composite rapid preheating method for deep heavy oil flooding, characterized in that: The following steps are involved: Step 101: drilling a plurality of vertical wells in the middle and upper part of the oil layer, and drilling a horizontal well at the bottom of the oil layer between the plurality of vertical wells; Step 102: performing variable density perforation on the vertical well according to the vertical heterogeneity of the reservoir; Step 103: injecting water vapor into the vertical well and the horizontal well at a level slightly higher than the formation fracture pressure at high intensity; Step 104: After soaking the well for a period of time, drain the water and start the next round of micro-fracturing high-intensity steam injection; Step 105: Monitor that the temperature between several vertical wells and between them and the horizontal wells exceeds the temperature required for the oil in the reservoir to become a Newtonian fluid, and the preheating is completed and the flooding and drainage composite production stage is entered.

2. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 1, characterized in that: In step 101, two rows of vertical wells are drilled in the upper part of the oil layer, and one horizontal well is drilled at the bottom of the oil layer between the two rows of vertical wells.

3. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 2, characterized in that: In step 101, the horizontal well is drilled and its vertical trajectory is guaranteed to be horizontal.

4. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 3, characterized in that: In step 101, the trajectory of the horizontal section on the horizontal well plane cannot deviate from the center of the target; the well inclination and full angle change rate of the horizontal section above 50m vertical depth meet the requirements of the flooding and drainage composite process.

5. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 3, characterized in that: The completion and sand control technologies of the vertical wells and horizontal wells also meet the composite requirements of flooding and drainage.

6. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 1, characterized in that: In step 102, the vertical well is transported by cable and perforated at near-balanced pressure.

7. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 3, characterized in that: In step 102, the pore density is reduced at the top of the oil layer and at the bottom where the physical properties are better.

8. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 3, characterized in that: In step 102, all-round spiral perforation is adopted and perforation is carried out by oil pipe transportation.

9. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 1, characterized in that: In step 103, a supercritical steam injection boiler is used to inject steam into the vertical well and the horizontal well simultaneously.

10. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 9, characterized in that: In step 103, the steam injection pressure range is 2 to 3 MPa higher than the formation fracture pressure.

11. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 9, characterized in that: In step 103, the steam injection intensity of the vertical wells and horizontal wells is increased to twice the conventional steam throughput, further accelerating the thermal connection between the injection and production wells.

12. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 1, characterized in that: In step 104, the wells are kept idle for a period of time to allow the injected steam and the oil reservoir to fully exchange heat, and then each well simultaneously recovers condensed water generated by the injected steam exchanging heat with the oil reservoir.

13. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 12, characterized in that: In step 104, in order to shorten the preheating time, a higher liquid production intensity is used for recovery. When the cumulative recovered water volume reaches the water equivalent of the injected steam, the next round of high-intensity combined injection and production begins.

14. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 1, characterized in that: In step 105, old wells between vertical wells and between vertical wells and horizontal wells are used as observation wells to monitor the oil layer temperature, ensuring that there is at least one observation well between each vertical well and horizontal well.

15. A deep layer heavy oil flooding composite rapid preheating method as claimed in claim 14, characterized in that: In step 105, when the temperatures monitored by all observation wells reach the temperature required for the crude oil in the reservoir to become a Newtonian fluid, it indicates that good thermal connectivity has been achieved between the injection and production wells, and the flooding and drainage composite production stage can be entered.

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