A multi-stage extraction method for heavy oil

Abstract

This invention belongs to the field of reservoir development and oil production engineering technology, and specifically relates to a multi-stage extraction method for heavy oil. This invention employs a multi-stage plug method to inject a viscosity reducer into the reservoir. Each stage of the plug injects a viscosity reducer with different concentrations, injection volumes, and injection displacements. The concentration range of the viscosity reducer in each stage is 1-10 times the effective concentration. The sum of the injection volumes constitutes the total injection volume, and the injection displacement is 10-60 m³ / s. 3 / h. This invention has the advantages of low cost, long effective time, and high cycle oil accumulation.

Description

Technical Field

[0001] This invention belongs to the field of oil reservoir development and oil production engineering technology, and in particular relates to a multi-stage extraction method for heavy oil. Background Technology

[0002] my country is extremely rich in heavy oil resources, with more than 70 heavy oil fields discovered in 12 large and medium-sized oil-bearing basins and depressions, including the Bohai Bay Basin, Songliao Basin, Nanxiang Basin, Junggar Basin, and Erlian Basin, with reserves exceeding 80 × 10⁻⁶. 8 Due to its viscosity, heavy oil faces high resistance to continuous seepage within reservoirs. For most heavy oil fields, apart from thermal recovery methods such as steam injection and steam drive, the recovery rate of other oil recovery methods is very low, less than 5% of the original reserves. However, the high upfront investment and operating costs of thermal recovery make it difficult for heavy oil production to be profitable, thus hindering efficient development and severely limiting the extent of heavy oil extraction. Furthermore, steam injection, currently the main oil recovery technology for heavy oil, suffers from severe reservoir steam channeling after multiple rounds of steam injection, leading to a sharp increase in water cut and even sudden water flooding, resulting in the overall waste of the block's reserves. Other oil recovery technologies besides thermal recovery are difficult to maintain long-term normal production in heavy oil reservoirs, and as the viscosity of heavy oil increases, its development becomes increasingly difficult. The proven reserves of up to 130 million tons of extra-heavy oil, deep heavy oil, sensitive heavy oil, and thin-layer heavy oil remain untapped.

[0003] Heavy oil, due to its high viscosity, faces significant challenges in its migration within reservoir flow mechanisms. For reservoirs with high crude oil saturation, core data do not necessarily reflect the actual reservoir permeability. This is because heavy oil adsorbs onto the rock surface as it flows through pores, narrowing the flow channels and reducing relative permeability, which in turn hinders sustainable heavy oil production. Given the high cost of thermal recovery and the lack of effective heavy oil extraction methods, chemical viscosity reduction has emerged as the most promising alternative method for heavy oil extraction due to its low development cost, ease of implementation, long effective production cycle, and minimal reservoir damage.

[0004] However, given the complexity of reservoir conditions, chemical viscosity reduction still faces numerous challenges in its current field applications: 1. Using only viscosity reduction rate as a screening indicator neglects the adsorption of the agent by the reservoir, resulting in most agents lacking universality; 2. Designing field agent concentrations based solely on laboratory viscosity reduction results ignores the influence of reservoir recovery and water content, leading to either ineffective low-concentration or wasteful high-concentration agents; 3. Using uniform permeability and porosity to design injection volume ignores reservoir heterogeneity, resulting in high-pressure injection difficulties or insufficient coverage during field operations; 4. Using fixed injection rates and slug concentrations in field operations leaves no response to pressure changes during injection, severely limiting injection effectiveness; 5. The shut-in diffusion time after treatment is too long and based on experience, lacking effective parameters for judgment and optimization.

[0005] Chinese patent application CN104265254A discloses a multi-stage plug injection process for deep, extra-heavy oil production using oil-soluble viscosity reducers and liquid CO2. The process involves injecting the oil-soluble viscosity reducer and liquid CO2 in four stages using a plug injection method. The injection intensity of the oil-soluble viscosity reducer is 2–3 t / m, the CO2 injection intensity is 15–20 t / m, the ratio of oil-soluble viscosity reducer to CO2 is 1:6–12, and the injection speed of the oil-soluble viscosity reducer is 8–12 m / s. 3 The liquid CO2 injection rate is 10–15 t / h. The first stage of injection involves injecting 40% of the total oil-soluble viscosity reducer at a rate of 8–12 m / h. 3 / h; The second stage of injection involves injecting 33% of the total liquid CO2 injection volume into the liquid CO2 at a rate of 10–15 t / h, along with 20% oil-soluble viscosity reducer at a rate of 8–12 m / h. 3 / h; The third stage of the plug injects 33% liquid CO2 at a rate of 10-15 t / h, and injects 20% oil-soluble viscosity reducer at a rate of 8-12 m / h. 3 / h; The fourth stage of the plug injects 33% liquid CO2 at a rate of 10-15 t / h, and injects 20% oil-soluble viscosity reducer at a rate of 8-12 m / h. 3 / h, using positive injection, high-temperature anti-swelling agent solution to replace, well shut-in and simmering for 10-15 days before resuming production. Although this method uses multi-stage injection, each stage plug uses the same concentration of viscosity reducer.

[0006] For the extraction of heavy oil, there is still a need for more effective extraction methods to improve recovery rates. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-stage extraction method for heavy oil. The method described in this invention has simple steps, low implementation cost, significant effects, long effective operating time, and high cumulative oil production over a period of time.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A multi-stage extraction method for heavy oil involves injecting a viscosity reducer into the reservoir using a multi-stage plug approach. Each stage of the plug injects a viscosity reducer with different concentrations, injection volumes, and injection discharge rates. The concentration of the viscosity reducer in each stage is 1-10 times the effective concentration. The injection discharge rate for each stage is 10-60 m³ / h. The sum of the injection volumes of each stage is the total injection volume.

[0010] Furthermore, in the above-mentioned multi-stage extraction method for heavy oil, the effective concentration is the agent concentration of the viscosity reducer at 50-70℃, for heavy oil with a degassed and dehydrated viscosity >30000mPa·s, when the viscosity reduction rate is >95%.

[0011] Furthermore, in the above-mentioned multi-stage heavy oil extraction method, for vertical and inclined wells, the total injected fluid volume is determined according to the formula Q = πr 2 LΦ is calculated, where L: effective oil layer thickness, in meters; r: pretreatment radius, in meters; Φ: porosity; Q: total injected fluid volume, in cubic meters. 3 .

[0012] For horizontal wells, the total injected fluid volume is calculated using the formula Q = HLWΦ, where H: effective oil layer thickness (m); L: horizontal well section length (m); W: expected treatment distance (m); Φ: porosity; and Q: total injected fluid volume (m³). 3 .

[0013] Furthermore, for vertical and inclined wells, the multi-stage mining method preferably employs a three-stage plug injection method to inject the viscosity reducer into the reservoir.

[0014] Furthermore, the three-stage plug configuration is as follows: the first stage plug has an injection volume of 20-30% of the total injection volume, a concentration of 3-10 times the effective concentration, and an injection displacement of 10-20 m³ / h. 3 / h; Second stage plug, the injection volume is 20-50% of the total injection volume, the concentration is 1-6 times the effective concentration, and the injection displacement is 40-60m. 3 / h; Third stage plug, the injection volume is 20-30% of the total injection volume, the concentration is 1-2 times the effective concentration, and the injection displacement is 20-40m. 3 / h.

[0015] The liquid concentration and flow rate of the above three-stage plugging method are determined based on the viscosity reduction rate of the selected viscosity reducer. Specifically, in the first stage, for reservoirs with a recovery rate of <5% and poor crude oil mobility in the near-wellbore area, injecting a high-concentration agent at a low flow rate allows the viscosity reducer to fully contact the crude oil, achieving rapid viscosity reduction and avoiding high injection pressure. For reservoirs with a water cut >50%, this effectively avoids excessive dilution of the subsequent injection agent, resulting in agent waste. In the second stage, high-flow injection allows the agent to continuously advance to the far end, avoiding the formation of heavy oil rings that could cause reservoir blockage. In the third stage, reducing the injection flow rate and increasing the injection concentration further enhances the mobility of heavy oil in the injection space generated by the high-speed injection in the second stage, improving the reservoir's fluid production capacity.

[0016] Furthermore, for horizontal wells, the multi-stage production method preferably employs a four-stage plug injection method to inject the viscosity reducer into the reservoir.

[0017] Furthermore, the four-stage plug configuration is as follows: the first stage plug has an injection volume of 10-20% of the total injection volume, a concentration of 3-10 times the effective concentration, and an injection displacement of 10-20 m³ / h. 3 / h; Second stage plug, the injection volume is 20-60% of the total injection volume, the concentration is 1-2 times the effective concentration, and the injection displacement is 30-50m. 3 / h; Third stage plug, the injection volume is 20-30% of the total injection volume, the concentration is 1-2 times the effective concentration, and the injection displacement is 40-60m. 3 / h; Fourth stage plug, the injection volume is 10-20% of the total injection volume, the concentration is 0.5-1 times the effective concentration, and the injection displacement is 20-30m. 3 / h.

[0018] The above four-stage plugging method involves the following steps: First stage plugging avoids high injection pressure or increases the concentration of reagents in the near-wellbore fluid; Second stage plugging with high flow rate can increase the sweep efficiency of the reagents in the unused areas of heavy oil in the horizontal section of the horizontal well, thereby improving the overall utilization rate of the horizontal section; Third stage plugging with high flow rate injects a higher concentration of reagents to maintain the reagent concentration in the casing area, improve the permeability of the near-wellbore reservoir, and increase the fluid production capacity of subsequent production; Fourth stage plugging uses the lowest effective concentration as the displacement fluid to increase the effective range of the pre-injection reagent, thereby increasing the mobility of more heavy oil.

[0019] Furthermore, the method also includes: after injecting the viscosity reducer into the reservoir, installing a pressure gauge on the casing, and starting production when the pressure is <1MPa.

[0020] Furthermore, the method is applicable to reservoir conditions where the heavy oil viscosity is <10000 mPa·s, the recovery rate is <25%, the water cut is <90%, the core permeability is >100 md, the porosity is >10%, and the clay content is <15%.

[0021] The method described in this invention is based on the mobility of heavy oil in the reservoir. It injects a viscosity reducer into the reservoir through a multi-concentration, multi-segment plugging method. At the same time, the injection parameters are adjusted according to the actual pressure changes to increase the injection coverage area. This significantly reduces the viscosity of heavy oil while increasing the relative permeability of the reservoir, thereby improving the mobility of heavy oil in the reservoir (mobility = permeability / viscosity) and achieving the goal of improving the recovery rate of heavy oil.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1) This invention utilizes a multi-stage heavy oil extraction method, by rationally setting the parameters of the viscosity reducer injected in each stage, which can significantly reduce the viscosity of heavy oil while increasing the relative permeability of the reservoir, thereby improving the mobility of heavy oil in the reservoir and effectively increasing the recovery rate of heavy oil.

[0024] 2) The injection agent of this invention requires no operation, which greatly saves costs. Intermittent injection avoids fatigue construction. The construction cycle is short (<3 days) and the well shut-in time is short (<1 day), which effectively improves the production cycle. The well opening and backflow of fluid is easy to demulsify and does not increase the burden of additional water treatment.

[0025] 3) Compared with the non-segmented mining method, the present invention can increase the continuous oil production time by 100% and the oil production volume by more than 200%. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0027] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] The following examples illustrate the preparation method of the viscosity reducer:

[0029] Add 300g of deionized water and 100g of kerosene to a 1500mL three-necked round-bottom flask, and stir with a magnetic stirrer. Then add 60g of acrylamide (AM), 10g of sodium acrylate (AA), 20g of 1-butenphenyl (PB), and 5g of acrylamide-2-methylpropanesulfonic acid (AMPS), and stir until completely dissolved and a white emulsion is formed. Next, add 0.15g of tetramethylethylenediamine (TEMED) catalyst, stir well, and then add Na2CO3 to adjust the pH to 8. Heat to 70℃ and purge with nitrogen for 30min to remove oxygen. Then add 5g of isopropanol, 0.15g of ammonium persulfate, and 0.15g of azoisobutyronitrile (AIBN). React until the solution becomes viscous and the magnetic stirrer stops rotating. Turn off the stirrer and stop the nitrogen purging. Let the reaction proceed for 8h. The gel block was removed from the flask, cut into small pieces, and placed in an oven at 80°C for 6 hours to dehydrate. After grinding and granulation, the yield was 75.2%. The resulting viscosity reducer is referred to as AM-SA-PB-AMPSNa (specifically as described in Example 1 of Chinese Patent CN109679639B).

[0030] According to the Sinopec Shengli Administration's enterprise standard "Q / SH1020 1519-2013 General Technical Conditions for Heavy Oil Viscosity Reducers", at 50°C, for heavy oil with a degassed and dehydrated viscosity >30000 mPa·s, the effective concentration of AM-SA-PB-AMPSNa when the viscosity reduction rate is >99% is 0.5 wt%. Examples 2-5 below all use the above-mentioned viscosity reducer.

[0031] Example 1

[0032] A vertical well in an oilfield has crude oil with a viscosity of 6630 mPa·s (degassed and dehydrated viscosity at reservoir temperature), a recovery rate of 14.5%, a water cut of 85.5%, a core permeability of 1300 md, a porosity of 31.8%, an effective oil layer thickness of 3.8 m, and a clay content of 6.4%.

[0033] The processing radius r is 10 meters, and the formula Q = πr is used. 2 LΦ (L: effective oil layer thickness; r: treatment radius; Φ: porosity; Q: total injected fluid volume) calculates the total injected fluid volume Q to be approximately 380m³. 3 .

[0034] The three-stage plug concentration injection method is adopted: the first stage plug, the injection volume is 100m³. 3 (26.3% Q), viscosity reducer concentration of 4wt%, injection displacement of 10m³ 3 / h, poor crude oil mobility in the near-wellbore area, low-volume injection of high-concentration reagents can effectively avoid excessive dilution of subsequent reagents and waste; second-stage plug, injection volume 180m 3 (47.4% Q), viscosity reducer concentration of 2wt%, injection displacement of 60m³ 3 / h, high-volume injection allows the reagent to continuously advance to distant sites, avoiding the formation of heavy oil rings that could cause reservoir blockage; the third-stage plug has an injection volume of 100m³. 3 (26.3% Q), viscosity reducer concentration 0.5wt%, injection displacement 40m³ 3 / h, reducing the injection displacement and increasing the injection concentration, further enhances the mobility of heavy oil in the injection space generated under high-speed injection of the second-stage plug, thereby improving the reservoir's liquid production capacity.

[0035] After construction is completed, a casing pressure gauge is installed with a pressure of 0.1 MPa, and the well is started for production.

[0036] Results: The oil production increased continuously for 8 months, with a cumulative increase of 715 tons during the period. The peak production during the period was 9.8 tons / day, and the peak duration was 33 days.

[0037] Example 2

[0038] A certain oilfield deviated well has crude oil viscosity of 6887 mPa·s (degassed and dehydrated viscosity at reservoir temperature), recovery rate of 21%, water cut of 50.7%, core permeability of 589 md, porosity of 28.5%, effective oil layer thickness of 8.2 m, and clay content of 10.5%.

[0039] The processing radius r is 10 meters, and the formula Q = πr is used. 2 LΦ (L: effective oil layer thickness; r: treatment radius; Φ: porosity; Q: total injected fluid volume) calculates the total injected fluid volume Q to be approximately 730 m³. 3 .

[0040] The three-stage plug concentration injection method is adopted: the first stage plug, the injection volume is 200m³. 3 (27.4% Q), viscosity reducer concentration 3wt%, injection displacement 20m 3 / h, near-wellbore area has poor crude oil mobility, low-volume injection of high-concentration reagents allows the viscosity reducer to fully contact the crude oil, achieving rapid viscosity reduction and avoiding high injection pressure; second-stage plug, injection volume 350m 3 (48% Q), viscosity reducer concentration 1wt%, injection displacement 50m 3 / h, high-volume injection allows the reagent to continuously advance to distant sites, avoiding the formation of heavy oil rings that could cause reservoir blockage; the third-stage plug has an injection volume of 180m³. 3 (24% Q), viscosity reducer concentration 0.5wt%, injection displacement 30m 3 / h, reducing the injection displacement and increasing the injection concentration, further enhances the mobility of heavy oil in the injection space generated under high-speed injection of the second-stage plug, thereby improving the reservoir's liquid production capacity.

[0041] After construction was completed, a casing pressure gauge was installed with a pressure of 6 MPa. After the well was shut down for 6 hours, the pressure dropped to 1 MPa, and the well was opened for production directly.

[0042] Results: The oil production increased continuously for 12 months, with a cumulative increase of 1585t during the period. The peak production during the period was 15.8t / d, and the peak duration was 61 days.

[0043] Example 3

[0044] A horizontal well in an oilfield has crude oil with a viscosity of 7700 mPa·s (degassed and dehydrated viscosity at reservoir temperature), a recovery rate of 23.3%, a water cut of 87.7%, a core permeability of 2100 md, a porosity of 32.3%, an effective oil layer thickness of 4.2 m, a clay content of 4.2%, and a horizontal section length of 105.8 m.

[0045] The treatment distance W is 5 meters. Using the formula Q = HLWΦ (H: effective oil layer thickness; L: horizontal well section length; W: expected treatment distance; Φ: porosity; Q: total injected fluid volume), the total injected fluid volume Q is approximately 720 m³. 3 .

[0046] The four-stage plug concentration injection method is adopted: the first stage plug, the injection volume is 100m³. 3 (13.8% Q), viscosity reducer concentration 5wt%, injection volume 10m³ 3 / h, increase the reagent concentration of the near-wellbore fluid; second stage plug, injection volume 400m 3 (55.7% Q), viscosity reducer concentration 1wt%, injection displacement 40m 3 / h, high-volume injection increases the sweep efficiency of the injected material in unused areas, increasing the overall utilization rate of the horizontal section; third-stage plug, injection volume 100m 3 (13.8% Q), viscosity reducer concentration 3wt%, injection displacement 60m³ 3 / h, low-volume injection of high-concentration reagents to maintain reagent concentration in the casing area, improve near-wellbore reservoir permeability, and increase subsequent production capacity; fourth stage plug, injection volume 120m 3 (16.7% Q), viscosity reducer concentration 0.5wt%, injection displacement 25m 3 / h, using the lowest effective concentration as the displacement fluid, increases the effective range of the pre-injection agent, allowing more heavy oil to improve its flowability.

[0047] After construction, a casing pressure gauge was installed with a pressure of 4 MPa. The well was shut in for 2 hours, and the pressure dropped to 0.5 MPa. The well was then opened for production.

[0048] Results: The oil production increased continuously for 12 months, with a cumulative increase of 2891t during the period. The peak production during the period was 21.3t / d, and the peak duration was 83 days.

[0049] Example 4

[0050] A horizontal well in an oilfield has crude oil viscosity of 8910 mPa·s (degassed and dehydrated viscosity at reservoir temperature), recovery rate of 8.9%, water cut of 21.6%, core permeability of 1500 md, porosity of 30.3%, effective oil layer thickness of 8.9 m, clay content of 10.3%, and horizontal section length of 82 m.

[0051] The treatment distance W is 5 meters. Using the formula Q = HLWΦ (H: effective oil layer thickness; L: horizontal well section length; W: expected treatment distance; Φ: porosity; Q: total injected fluid volume), the total injected fluid volume Q is approximately 1080 m³. 3 .

[0052] The four-stage plug concentration injection method was adopted: the first stage plug, with an injection volume of 150m³. 3 (13.9% Q), viscosity reducer concentration 5wt%, injection volume 10m³ 3 / h, to avoid high injection pressure; second stopper, injection volume 550m 3 (51% Q), viscosity reducer concentration 1wt%, injection displacement 40m 3 / h, high-volume injection increases the sweep efficiency of the injected fluid in unused areas, improving the overall utilization rate of the horizontal section; third-stage plug, injection volume 200m 3 (18.5% Q), viscosity reducer concentration 2wt%, injection volume 50m³ 3 / h, low-volume injection of high-concentration reagents to maintain reagent concentration in the casing area, improve near-wellbore reservoir permeability, and increase subsequent production capacity; Fourth stage plug, injection volume 180m³ 3 (16.7% Q), viscosity reducer concentration 0.5wt%, injection displacement 25m 3 / h, using the lowest effective concentration as the displacement fluid, increases the effective range of the pre-injection agent, allowing more heavy oil to improve its flowability.

[0053] After construction was completed, a casing pressure gauge was installed, with a pressure of 6.8 MPa. The well was shut down for 6 hours, and the pressure dropped to 1.2 MPa, at which point production was resumed directly.

[0054] Results: The oil production increased continuously for 12 months, with a cumulative increase of 3490t during the measure period. The peak production during the period was 16.3t / d, and the peak duration was 100 days.

[0055] Comparative Example

[0056] A vertical well in an oilfield has crude oil with a viscosity of 5630 mPa·s (degassed and dehydrated viscosity at reservoir temperature), a recovery rate of 12.5%, a water cut of 80.5%, a core permeability of 1000 md, a porosity of 30.3%, an effective oil layer thickness of 4.5 m, and a clay content of 5.4%.

[0057] With a treatment radius r of 10 meters, the total injection volume Q is approximately 430 m3, calculated using the formula Q = πr²LΦ (L: effective thickness of the oil layer; r: treatment radius; Φ: porosity; Q: total injected fluid volume). The concentration of AM-SA-PB-AMPSNa used is 0.5 wt%.

[0058] Single-stage plug homogeneous concentration injection method was adopted: concentration 2.0 wt%, injection displacement 20 m³ / s. 3 / h, total injection 200m 3 The solution temperature was 56℃. After construction was completed, a casing pressure gauge was installed with a pressure of 0.2MPa, and the well was started for production.

[0059] Results: The continuous increase in oil production lasted only 3 months, with a cumulative increase of 215 tons during the measure period. The peak output during the period was 3.6 tons / day, and the peak duration was 14 days.

[0060] Compared with the comparative examples, Examples 1-4 show that the multi-segment plug, multi-concentration injection method significantly increases oil production compared to the single-segment plug, uniform-concentration injection method. Furthermore, measures are more effective in low water-cut wells than in high water-cut wells, and measures in horizontal wells are significantly more effective than those in vertically inclined wells.

[0061] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for multi-stage extraction of heavy oil, characterized in that, Includes the following steps: Viscosity reducers are injected into the reservoir using a multi-stage plug method. Each stage uses a different concentration, injection volume, and injection flow rate of the viscosity reducer. The concentration of the viscosity reducer in each stage ranges from 0.5 to 10 times the effective concentration; the injection flow rate for each stage is 10-60 m³ / s. 3 / h; The sum of the injection fluid volumes of each segment plug is the total injection fluid volume; The effective concentration is the agent concentration of the viscosity reducer at 50-70℃, for heavy oil with a degassed and dehydrated viscosity >30000 mPa•s, when the viscosity reduction rate is >95%. For vertically inclined wells, the total injected fluid volume is calculated using the formula Q=πr 2 LΦ is calculated, where L: effective oil layer thickness, in meters; r: pretreatment radius, in meters; Φ: porosity; Q: total injected fluid volume, in cubic meters. 3 ; For horizontal wells, the total injected fluid volume is calculated using the formula Q = HLWΦ, where H: effective oil layer thickness (m); L: horizontal well section length (m); W: expected treatment distance (m); Φ: porosity; and Q: total injected fluid volume (m³). 3 ; For vertical and inclined wells, the multi-stage mining method uses a three-stage plug to inject viscosity reducer into the reservoir; The three-stage plug method is as follows: the first stage plug, the injection volume is 20-30% of the total injection volume, the concentration is 3-10 times the effective concentration, and the injection displacement is 10-20m. 3 / h; Second stage plug, the injection volume is 20-50% of the total injection volume, the concentration is 1-6 times the effective concentration, and the injection displacement is 40-60m. 3 / h; Third stage plug, the injection volume is 20-30% of the total injection volume, the concentration is 1-2 times the effective concentration, and the injection displacement is 20-40m. 3 / h; For horizontal wells, the multi-stage production method uses a four-stage plug to inject viscosity reducer into the reservoir; The four-stage plug method is as follows: For the first stage plug, the injection volume is 10-20% of the total injection volume, the concentration is 3-10 times the effective concentration, and the injection displacement is 10-20 m³ / h. 3 / h; Second stage plug, the injection volume is 20-60% of the total injection volume, the concentration is 1-2 times the effective concentration, and the injection displacement is 30-50m. 3 / h; Third stage plug, the injection volume is 20-30% of the total injection volume, the concentration is 1-2 times the effective concentration, and the injection displacement is 40-60m. 3 / h; Fourth stage plug, the injection volume is 10-20% of the total injection volume, the concentration is 0.5-1 times the effective concentration, and the injection displacement is 20-30m. 3 / h; The method further includes: after injecting the viscosity reducer into the reservoir, installing a pressure gauge on the casing, and starting production when the pressure is <1MPa; The method is applicable to reservoir conditions where the viscosity of heavy oil is <10000 mPa•s, the recovery rate is <25%, the water cut is <90%, the core permeability is >100 md, the porosity is >10%, and the clay content is <15%.