Method for optimizing deep low-permeability thick oil viscosity reduction pressure drive injection parameters

Abstract

The invention provides a method for optimizing injection parameters of deep low-permeability thick oil viscosity reduction pressure drive. The method for optimizing the injection parameters of the deep low-permeability thick oil viscosity reduction pressure drive comprises the steps that 1, pressure drive pump injection limited pressure is determined; 2, determining a reasonable formation pressure coefficient; 3, the injection amount required for recovering the formation pressure to the reasonable formation pressure is calculated; step 4, determining the concentration of the viscosity reducer injected by the viscosity reduction pressure drive; 5, the injection amount and the slug number of each slug in pressure driving are determined; step 6, determining a pressure driving slug interval period; and 7, after each slug is finished, entering the next slug until the total injection amount is finished. According to the method for optimizing the injection parameters of the deep low-permeability thick oil viscosity reduction pressure drive, the problem of rapid energy supplementation in the viscosity reduction pressure drive process is solved, meanwhile, the problems of water flooding, water channeling and poor fluidity caused by damage of thick oil pressure drive to a viscosity reduction cavity are solved, and the method for improving the single well productivity of deep low-permeability thick oil viscosity reduction pressure drive is provided.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a method for optimizing injection parameters of deep-layer low-permeability heavy oil with reduced viscosity and pressure drive. Background Art

[0002] Conventional steam injection thermal recovery has poor effects on deep low-permeability heavy oil due to the depth of the reservoir, low permeability, reservoir sensitivity and high crude oil viscosity.

[0003] In recent years, with the development of viscosity reduction drive technology, such reservoirs can be effectively utilized. However, conventional viscosity reduction drive replenishes formation energy slowly and cannot meet the demand for a significant increase in production capacity. At the same time, affected by reservoir heterogeneity, conventional displacement is prone to water flooding and water channeling, resulting in a decrease in later production capacity.

[0004] With the emergence of pressure drive technology, pressure drive is an effective means to quickly replenish the formation. Viscosity reduction pressure drive has also been applied to the development of deep low-permeability heavy oil. However, although continuous pressure drive can quickly replenish formation energy, due to the large injection volume, high injection pressure, and changes in crude oil rheology, the fluidity of crude oil deteriorates, and the displacement pressure difference becomes more difficult to establish.

[0005] After searching, the main methods for improving the development effect of deep heavy oil cold production are as follows:

[0006] In the Chinese patent application with application number: CN202010707437.4, a viscosity reduction and driving method for effectively mobilizing deep low-permeability heavy oil is involved, which method includes: step 1, selecting a viscosity reducer system; step 2, determining the well spacing of the reservoir well pattern; step 3, simulating production wells to carry out viscosity reducer throughput and driving effect, optimizing the driving effect cycle and the injection amount of the viscosity reducer, and determining the optimal viscosity reduction throughput and driving effect scheme; step 4, optimizing the displacement mode and viscosity reducer concentration, and determining the best viscosity reduction and driving scheme; step 5, producing wells according to the determined viscosity reduction throughput and driving scheme, and carrying out viscosity reduction and driving of injection wells according to the determined viscosity reduction and driving scheme. This method has good operability, low cost, and is conducive to promotion, and solves the problem of the difficulty in effectively mobilizing deep low-permeability heavy oil.

[0007] In the Chinese patent application with application number: CN202010539903.2, a method for displacement development of deep low-permeability heavy oil by fluidity regulation is involved, which includes: step 1, using a large-displacement high-speed flow injection method to break through the injection section accumulation zone and heavy component retention zone; step 2, the surface water pump continuously injects the viscosity reducer solution online; step 3, repeating steps 1 and 2, continuously reducing the high-viscosity zone retention area to establish an effective displacement pressure difference; step 4, reducing the viscosity of the crude oil to increase the viscosity of the injected solution, regulating the fluidity to increase the displacement sweep volume; step 5, continuously adjusting the injection concentration to achieve the best displacement effect. This method for displacement development of deep low-permeability heavy oil by fluidity regulation effectively solves the problems of unsuitability of deep low-permeability heavy oil reservoirs for thermal recovery, difficulty in establishing water-driven displacement pressure difference, and difficulty in expanding displacement sweep, and realizes the efficient use of such reserves.

[0008] In the Chinese patent application with application number: CN202011213140.9, a method for reducing viscosity and driving pressure in deep low-permeability heavy oil reservoirs is involved, which includes: step 1, screening and evaluating to determine the viscosity reduction displacement system; step 2, optimizing and determining the well pattern and spacing of the reservoir viscosity reduction and pressure drive; step 3, injecting the viscosity reduction system at high pressure, high speed and large displacement into the injection well to drive the plug and shut down the well; optimizing the injection amount and injection concentration of the viscosity reducer; step 4, shutting down the well after the viscosity reduction and huff-and-puff effect of the production well; determining the optimal viscosity reduction and huff-and-puff effect scheme; step 5, the production well is opened for production; step 6, repeating steps 3-5 until the development is completed. This method increases the production pressure difference between the injection and production wells, forms a large number of three-dimensional fracture networks, and improves the porosity and permeability structure of the formation; the sweep coefficient and oil displacement efficiency of the viscosity reducer solution are greatly improved, the viscosity of the oil phase is greatly reduced, and the liquid flow capacity in the formation is greatly improved, thereby greatly improving the production capacity of the oil well, and ultimately improving the recovery rate of the reservoir to achieve efficient development.

[0009] The above patented technologies mainly involve the selection of viscosity reduction system, viscosity reduction drive fluidity control, viscosity reduction pressure drive and other methods to improve the development effect of deep low-permeability heavy oil, but do not involve the pressure drive injection parameters. As the viscosity of underground crude oil increases, it is easy to cause one-way breakthrough under rigid water drive conditions, greatly reducing the oil recovery efficiency. At present, there is no relevant technology to solve the problems of water flooding and water channeling and poor crude oil fluidity that occur during the heavy oil pressure drive field experiment. For this reason, we have invented a method for optimizing the injection parameters of deep low-permeability heavy oil viscosity reduction pressure drive, which solves the above technical problems. Summary of the invention

[0010] The purpose of the present invention is to provide a method for optimizing injection parameters of deep-layer low-permeability heavy oil viscosity reduction pressure drive.

[0011] The object of the present invention can be achieved by the following technical measures: a method for optimizing injection parameters of deep-layer low-permeability heavy oil with reduced viscosity and pressure-driven injection, the method comprising:

[0012] Step 1, determining the pressure limit of the pressure-driven pump injection;

[0013] Step 2, determining a reasonable formation pressure coefficient;

[0014] Step 3, calculating the injection volume required to restore the formation pressure to a reasonable formation pressure;

[0015] Step 4, determining the concentration of viscosity reducing agent injected for viscosity reducing pressure flooding;

[0016] Step 5, determining the injection amount and number of each slug in the pressure drive;

[0017] Step 6, determining the pressure-driven segment plug interval period;

[0018] Step 7: After each segment is completed, the next segment is entered until the total injection volume is completed.

[0019] The purpose of the present invention can also be achieved by the following technical measures:

[0020] In step 1, the pressure limit of the adaptive pressure-drive water injection construction is determined according to the fracture pressure of the block.

[0021] In step 2, according to the formation deficit, the material balance method is used in combination with numerical simulation to determine the reasonable formation pressure coefficient.

[0022] In step 3, the required pressure-driven injection volume is calculated according to the target production pressure difference and the comprehensive compression coefficient.

[0023] In step 3, the formula for calculating the pressure drive injection volume is:

[0024] V=V P C t Δp Formula (1)

[0025] in

[0026] Where: V: pressure drive injection volume, m 3 ; V P : pore volume, m 3 ; C t : Comprehensive compression coefficient, Δp: target pressure difference, MPa; Porosity, %; C f : Rock compression coefficient, MPa -1 ; Co: crude oil compressibility, MPa -1 ; C w : Formation water compressibility, MPa -1 ; S o : Oil saturation, %; S w : Water saturation, %.

[0027] In step 4, the concentration of viscosity reducer injected for viscosity reduction pressure drive is determined. According to numerical simulation, the relationship curve between the injection concentration of viscosity reducer and net oil production shows that as the concentration of viscosity reducer increases, the net oil production first increases and then decreases, and the concentration corresponding to the highest net oil production; considering the economy and recovery factor comprehensively, the preferred displacement concentration is 1%-3%.

[0028] In step 5, the injection volume and number of each slug in the pressure drive are determined; in order to control the pressure front to just reach the bottom of the oil well, when calculating the slug injection volume, the reservoir is considered to be a mean medium, radial flow is used during production, the injection volume is constant V, the formation thickness is h, the sweep radius is R, and the injection direction coefficient is γ, and the functional relationship between the maximum displacement radius of the water well injection and the injection volume is derived.

[0029] In step 5, the maximum displacement radius of the water well injection and the injection volume have the following functional relationship:

[0030]

[0031] Where: h: oil layer thickness, m; Porosity, %; a: percentage of high permeability water absorption thickness to total thickness, %; γ: injection direction coefficient, %; According to Formula 2, the slug injection amount and the number of slugs are determined by comparing the effects of different slug injection amounts in numerical simulation.

[0032] In step 6, considering the blockage and reservoir resistance of heavy oil near and far wellbore, the displacement requirement is less than 0.8m 3 / min, numerical simulation of the slug interval period, and adjustment on site based on actual pressure drop.

[0033] In step 7, after each plug is injected, the formation pressure is balanced and then the next plug is injected until the total injection volume is completed, so that the formation pressure is gradually raised and finally reaches a reasonable formation pressure.

[0034] The purpose of the present invention can also be achieved through the following technical measures: a deep low permeability heavy oil viscosity reduction pressure drive injection parameter optimization system, which adopts a deep low permeability heavy oil viscosity reduction pressure drive injection parameter optimization method to improve the single well production capacity of deep low permeability heavy oil viscosity reduction pressure drive.

[0035] The method for optimizing injection parameters for viscosity reduction and pressure drive of deep low permeability heavy oil in the present invention achieves rapid replenishment of formation energy, shortens the time to establish displacement pressure difference, avoids linear water channeling, and reduces the influence of crude oil rheological changes on seepage by optimizing injection parameters, thereby achieving the purpose of greatly improving the single well production capacity. Compared with the prior art, the method for optimizing injection parameters for viscosity reduction and pressure drive of deep low permeability heavy oil solves the problem of rapid energy replenishment during viscosity reduction and pressure drive by combining numerical simulation with water drive front monitoring results, production conditions, etc., and solves the problem of water flooding and water channeling and deterioration of fluidity caused by the destruction of the viscosity reduction cavity by heavy oil pressure drive, and provides a set of methods for improving the single well production capacity by viscosity reduction and pressure drive of deep low permeability heavy oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of a specific embodiment of the method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil of the present invention;

[0037] Figure 2 A comparison diagram of reasonable formation pressure coefficient simulation results of a specific embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of a curve showing the relationship between different pressure-driven injection amounts and sweep radius according to a specific embodiment of the present invention;

[0039] Figure 4 A bar graph of net oil production at different pressure drive injection viscosity reducer concentrations according to a specific embodiment of the present invention;

[0040] Figure 5 It is a schematic diagram of comparison of numerical simulation results of production effects of different enhanced slug injection amounts in a specific implementation block of the present invention;

[0041] Figure 6 A schematic diagram of effect curves before and after implementation of a slug-type viscosity reduction pressure flooding according to another specific embodiment of the present invention;

[0042] Figure 7 Schematic diagram of synthetic curve of the effect of W block plug-type viscosity reduction pressure drive well group promoted and applied by the present invention. DETAILED DESCRIPTION

[0043] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0045] The method for optimizing injection parameters of deep low-permeability heavy oil viscosity reduction pressure drive of the present invention comprises the following steps:

[0046] Step 1: Adapt the pressure limit of the pressure-driven water injection pumping construction according to the fracture pressure of the block;

[0047] Step 2: According to the formation deficit, the material balance method is used in combination with numerical simulation to determine the reasonable formation pressure coefficient;

[0048] Step 3: Set the target production pressure difference and calculate the pressure-driven injection volume according to Formula 1 based on the comprehensive compression coefficient.

[0049] The formula for calculating the pressure drive injection volume is:

[0050] V=V P C t Δp Formula (1)

[0051] in

[0052] Where: V: pressure drive injection volume, m 3 ; V P : pore volume, m 3 ; C t : Comprehensive compression coefficient, Δp: target pressure difference, MPa; Porosity, %; C f : Rock compression coefficient, MPa -1 ; Co: crude oil compressibility, MPa -1 ; C w : Formation water compressibility, MPa -1 ; S o : Oil saturation, %; S w : Water saturation, %.

[0053] Step 4, determine the concentration of viscosity reducer injected for viscosity reduction pressure flooding. According to numerical simulation, the relationship curve between the injection concentration of viscosity reducer and net oil production shows that as the concentration of viscosity reducer increases, net oil production first increases and then decreases, and the concentration corresponding to the highest net oil production. Considering the economy and recovery factor comprehensively, the preferred displacement concentration is 1%-3%.

[0054] Step 5, determine the injection volume and number of each slug in the pressure drive. In order to control the pressure front to just reach the bottom of the oil well and avoid excessive injection to damage the viscosity reduction cavity, the directional coefficient is determined based on the monitoring results of the water drive front, production conditions and reservoir thickness, and the injection volume and number of slugs are determined based on the comparison of the effects of different slug injection volumes by numerical simulation.

[0055] In order to control the pressure front to just reach the bottom of the oil well, when calculating the slug injection volume, the reservoir is considered to be a mean medium, the production is radial flow, the injection volume is constant V, the formation thickness is h, the sweep radius is R, and the injection direction coefficient is γ. It is derived that the maximum displacement radius of the water well injection and the injection volume have the following functional relationship:

[0056]

[0057] Where: h: oil layer thickness, m; Porosity, %; a: percentage of high permeability water absorption thickness to total thickness, %; γ: injection direction coefficient, %; According to Formula 2, the slug injection amount and the number of slugs are determined by comparing the effects of different slug injection amounts in numerical simulation.

[0058] Step 6: Determine the interval period of pressure-driven segment plugging. Considering the blockage and reservoir resistance in the near-well and far-well areas of heavy oil, the displacement requirement is <0.8m 3 / min, numerical simulation of the slug interval period, and adjustment on site based on actual pressure drop.

[0059] Step 7: After each plug is injected, wait for the formation pressure to be balanced before entering the next plug until the total injection volume is completed, so that the formation pressure is gradually raised and finally reaches a reasonable formation pressure.

[0060] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, preferred embodiments are given below and the technical solution of the present invention is described in detail in conjunction with the accompanying drawings.

[0061] The following are several specific embodiments of the present invention.

[0062] Example 1

[0063] In a specific embodiment 1 of the present invention, Figure 1 As shown, Figure 1 The flowchart of the method for optimizing injection parameters of deep-layer low-permeability heavy oil viscosity reduction pressure drive of the present invention. The method for optimizing injection parameters of deep-layer low-permeability heavy oil viscosity reduction pressure drive comprises the following steps:

[0064] In step 101, the pressure limit of the pressure-driven water injection pumping operation is determined according to the fracturing pressure of the block;

[0065] In step 102, according to the formation deficit, a reasonable formation pressure coefficient is determined by using a material balance method in combination with numerical simulation;

[0066] In step 103, the required pressure drive injection amount is calculated according to the target pressure difference and the comprehensive compression coefficient according to Formula 1:

[0067] V=V P C t Δp Formula (1)

[0068] in

[0069] Where: V: pressure drive injection volume, m 3 VP: pore volume, m 3 ; C t : Comprehensive compression coefficient, Δp: target pressure difference, MPa; Porosity, %; C f : Rock compression coefficient, MPa -1 ; Co: crude oil compressibility, MPa -1 ; C w : Formation water compressibility, MPa -1 ; S o : Oil saturation, %; S w : Water saturation, %.

[0070] In step 104, the concentration of the viscosity reducer injected for viscosity reduction pressure flooding is determined. According to numerical simulation, the relationship curve between the concentration of the viscosity reducer injected and the net oil production shows that the net oil production increases first and then decreases with the increase of the viscosity reducer concentration, and the concentration corresponding to the highest net oil production. Considering the economic performance and recovery rate comprehensively, the preferred displacement concentration is 1%-1.5%.

[0071] In step 105, the injection volume and number of each slug in the pressure drive are determined. In order to control the pressure front to just reach the bottom of the oil well and avoid excessive injection to damage the viscosity reduction cavity, the directional coefficient is determined in combination with the water drive front monitoring results, production conditions and reservoir thickness, and the slug injection volume is calculated according to Formula 2:

[0072]

[0073] Where: h: oil layer thickness, m; Porosity, %; a: percentage of high permeability water absorption thickness to total thickness, %; γ: injection direction coefficient, %; According to Formula 2, the slug injection amount and the number of slugs are determined by comparing the effects of different slug injection amounts in numerical simulation.

[0074] The slug injection volume and number of slugs are determined by comparing the effects of different slug injection volumes using numerical simulation. 3, determine the number of pressure-driven segment plugs to be 4.

[0075] In step 106, considering the blockage and reservoir resistance in the near and far wellbore areas, the displacement requirement is <0.8m 3 / min, pressure-driven daily injection displacement 600m 3 / d. According to numerical simulation, the slug interval is 10 days, which is adjusted to 12 days on site according to the actual pressure drop.

[0076] In step 107, after each segment plug is injected into the well, step 105 is repeated to inject the next segment plug until the total injection volume is completed, so that the formation pressure is gradually raised and finally reaches a reasonable formation pressure.

[0077] Example 2

[0078] In a specific embodiment 2 of the present invention, as Figure 1 As shown, Figure 1 The flowchart of the method for optimizing injection parameters of deep-layer low-permeability heavy oil viscosity reduction pressure drive of the present invention. The method for optimizing injection parameters of deep-layer low-permeability heavy oil viscosity reduction pressure drive comprises the following steps:

[0079] In step 101, the pressure limit of the pressure-driven water injection pumping operation is determined according to the fracturing pressure of the block;

[0080] In step 102, according to the formation deficit, a reasonable formation pressure coefficient is determined by using a material balance method in combination with numerical simulation;

[0081] In step 103, the required pressure drive injection amount is calculated according to the target pressure difference and the comprehensive compression coefficient according to formula (1):

[0082] V=V P C t Δp Formula (1)

[0083] in

[0084] Where: V: pressure drive injection volume, m 3 ; V P : pore volume, m 3 ; C t : Comprehensive compression coefficient, Δp: target pressure difference, MPa; Porosity, %; C f : Rock compression coefficient, MPa -1 ; Co: crude oil compressibility, MPa -1 ; C w : Formation water compressibility, MPa -1 ; S o : Oil saturation, %; S w: Water saturation, %.

[0085] In step 104, the concentration of the viscosity reducer injected for viscosity reduction pressure flooding is determined. According to numerical simulation, the relationship curve between the injection viscosity reducer concentration and the net oil production shows that the net oil production increases first and then decreases with the increase of the viscosity reducer concentration, and the concentration corresponding to the highest net oil production. Considering the economy and recovery factor comprehensively, the preferred displacement concentration is 1.5%.

[0086] In step 105, when calculating the slug injection volume, the reservoir is considered to be a mean medium and radial flow is used during production: Assuming that the injection volume is constant V, the formation thickness is h, the sweep radius is R, and the injection direction coefficient is γ, it is derived that the maximum displacement radius of the well injection and the injection volume have the following functional relationship:

[0087]

[0088] Where: h: oil layer thickness, m; Porosity, %; a: percentage of high permeability water absorption thickness to total thickness, %; γ: injection direction coefficient, %; According to Formula 2, the slug injection amount and the number of slugs are determined by comparing the effects of different slug injection amounts in numerical simulation.

[0089] According to Formula 2, the injection volume of the pressure-driven segment plug is optimized to 3000m 3 , the number of slugs is 5.

[0090] In step 106, considering the blockage and reservoir resistance in the near and far wellbore areas, the displacement requirement is <0.8m 3 / min, pressure-driven daily injection displacement 1000m 3 / d, and the slug interval period is 15 days according to numerical simulation.

[0091] In step 107, after each plug is injected into the well, step 105 is repeated to inject the next plug until the total injection volume is completed, so that the formation pressure is gradually raised and finally the target formation pressure is reached.

[0092] Example 3

[0093] In Block W of a deep low-permeability sensitive heavy oil reservoir, the burial depth is 1500m, the viscosity of the degassed crude oil on the ground is 18000mPa.s, the permeability is 135mD, and the elastic yield is 0.089×10 4 t / MPa, the natural energy is weak. In order to quickly replenish the formation energy and shorten the time to establish the displacement pressure difference between oil and water wells, W152-X21 was selected to carry out viscosity reduction pressure drive.

[0094] In step 101, the pressure limit of the pressure-driven water injection pumping operation is determined according to the fracturing pressure of the block;

[0095] In step 102, according to the formation deficit, the material balance method is used in combination with numerical simulation to determine the reasonable formation pressure coefficient. According to the numerical simulation method, the reasonable formation pressure coefficient is calculated, and the reasonable formation pressure coefficient is determined by simulating the relationship curve between the formation pressure coefficient and the net oil production. Figure 2 As shown in the figure, the curve relationship diagram is a comparison diagram of production effects under different formation pressures of the W152 unit numerical simulation. With the increase of the amount of viscosity reducer injected, the net oil production first increases and then decreases. When the formation pressure is maintained at 17.86MPa, the net oil production is the largest. This point is selected as the reasonable formation pressure, and the pressure coefficient at this time is calculated to be 1.2 of the original formation pressure (reasonable formation pressure coefficient = reasonable formation pressure / original formation pressure).

[0096] In step 103, the required pressure drive injection amount is calculated according to the target pressure difference and the comprehensive compression coefficient according to formula (1):

[0097] V=V P C t Δp Formula (1)

[0098] in

[0099] Where: V: pressure drive injection volume, m 3 ; V P : pore volume, m 3 ; C t : Comprehensive compression coefficient, Δp: target pressure difference, MPa; Porosity, %; C f : Rock compression coefficient, MPa -1 ; Co: crude oil compressibility, MPa -1 ; C w : Formation water compressibility, MPa -1 ; S o : Oil saturation, %; S w : Water saturation, %.

[0100] In step 104, according to numerical simulation, the relationship curve between the injection viscosity reducer concentration and the net oil production (such as Figure 3 ) It is concluded that as the viscosity reducer concentration increases, the net oil production first increases and then decreases, and the concentration corresponding to the highest net oil production. Taking into account the economy and recovery factor, the viscosity reducer concentration of 1% is preferably determined for viscosity reduction pressure flooding.

[0101] In step 105, when calculating the slug injection volume, the reservoir is considered to be a mean medium and radial flow is used during production: Assuming that the injection volume is constant V, the formation thickness is h, the sweep radius is R, and the injection direction coefficient is γ, it is derived that the maximum displacement radius of the well injection and the injection volume have the following functional relationship:

[0102]

[0103] Where: h: oil layer thickness, m; Porosity, %; a: percentage of high permeability water absorption thickness to total thickness, %; γ: injection direction coefficient, %; According to Formula 2, the slug injection amount and the number of slugs are determined by comparing the effects of different slug injection amounts in numerical simulation.

[0104] Combined with formula 2, different pressure-driven injection amounts correspond to different sweep radii (such as Figure 4 ), the advancement distance in the dominant direction is 78m, corresponding to the injection volume of 3000m 3 , combined with numerical simulation to compare the injection effects of different slug injection volumes (such as Figure 5 ), determine the slug injection volume of 3000m 3 , injected in 4 segments.

[0105] In step 106, considering the blockage and reservoir resistance in the near and far wellbore areas, the displacement requirement is <0.8m 3 / min, pressure drive daily injection displacement 1000m 3 / d. According to numerical simulation, the slug interval period is 15 days, which is adjusted on site according to the actual pressure drop.

[0106] In step 107, after each plug is injected into the well, step 105 is repeated to inject the next plug until the total injection volume is completed, so that the formation pressure is gradually raised and finally the target formation pressure is reached.

[0107] Before the implementation, the average daily liquid production of the well group was 4t / d and the daily oil production was 2.6t / d. After the implementation of the plug-type viscosity reduction flooding, the average daily liquid production increased to 7t / d and the daily oil production increased to 3.4t / d, with significant effects on increasing oil production and energy. Figure 6 .

[0108] After the promotion and application in Block W, the displacement relationship between oil and water wells was gradually established. The unit effect curve is shown in the figure below. Figure 7 The average single-well production capacity increased by 1.2t / d, the single-well oil production increased by 523t, the oil well efficiency increased from 37.5% to 81.3%, and the unit production increased and remained stable.

[0109] Compared with the existing technology, the method for optimizing injection parameters for viscosity reduction and pressure drive of low-permeability heavy oil solves the problem of quickly replenishing formation energy during viscosity reduction and pressure drive, and solves the problems of water flooding and water channeling and deterioration of crude oil fluidity that occur during the heavy oil pressure drive field experiment. It provides a solution for improving the single-well production capacity by viscosity reduction and pressure drive of deep low-permeability heavy oil.

[0110] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0111] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil, characterized in that: The method for optimizing injection parameters of deep low-permeability heavy oil viscosity reduction pressure drive includes: Step 1, determining the pressure limit of the pressure-driven pump injection; Step 2, determining a reasonable formation pressure coefficient; Step 3, calculating the injection volume required to restore the formation pressure to a reasonable formation pressure; Step 4, determining the concentration of viscosity reducing agent injected for viscosity reducing pressure flooding; Step 5, determining the injection amount and number of each slug in the pressure drive; Step 6, determining the pressure-driven segment plug interval period; Step 7: After each segment is completed, the next segment is entered until the total injection volume is completed.

2. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 1, characterized in that: In step 1, the pressure limit of the adaptive pressure-drive water injection construction is determined according to the fracture pressure of the block.

3. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 1, characterized in that: In step 2, according to the formation deficit, the material balance method is used in combination with numerical simulation to determine the reasonable formation pressure coefficient.

4. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 1, characterized in that: In step 3, the required pressure-driven injection volume is calculated according to the target production pressure difference and the comprehensive compression coefficient.

5. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 4, characterized in that: In step 3, the formula for calculating the pressure drive injection volume is: V=V P C t Δp Formula (1) in Where: V: pressure drive injection volume, m 3 ; V P : pore volume, m 3 ; C t : Comprehensive compression coefficient, Δp: target pressure difference, MPa; Porosity, %; C f : Rock compression coefficient, MPa -1 ; C o : Crude oil compressibility, MPa -1 ; C w : Formation water compressibility, MPa -1 ; S o : Oil saturation, %; S w : Water saturation, %.

6. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 1, characterized in that: In step 4, the concentration of viscosity reducer injected for viscosity reduction pressure drive is determined. According to numerical simulation, the relationship curve between the injection concentration of viscosity reducer and net oil production shows that as the concentration of viscosity reducer increases, the net oil production first increases and then decreases, and the concentration corresponding to the highest net oil production; considering the economy and recovery factor comprehensively, the preferred displacement concentration is 1%-3%.

7. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 1, characterized in that: In step 5, the injection volume and number of each slug in the pressure drive are determined; in order to control the pressure front to just reach the bottom of the oil well, when calculating the slug injection volume, the reservoir is considered to be a mean medium, radial flow is used during production, the injection volume is constant V, the formation thickness is h, the sweep radius is R, and the injection direction coefficient is γ, and the functional relationship between the maximum displacement radius of the water well injection and the injection volume is derived.

8. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 7, characterized in that: In step 5, the maximum displacement radius of the water well injection and the injection volume have the following functional relationship: Where: h: oil layer thickness, m; Porosity, %; a: percentage of high permeability water absorption thickness to total thickness, %; γ: injection direction coefficient, %; According to Formula 2, the slug injection amount and the number of slugs are determined by comparing the effects of different slug injection amounts in numerical simulation.

9. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 1, characterized in that: In step 6, considering the blockage and reservoir resistance of heavy oil near and far wellbore, the displacement requirement is less than 0.8m 3 / min, numerical simulation of the slug interval period, and adjustment on site based on actual pressure drop.

10. The method for optimizing injection parameters for viscosity reduction and pressure flooding of deep low-permeability heavy oil according to claim 1, characterized in that: In step 7, after each plug is injected, the formation pressure is balanced and then the next plug is injected until the total injection volume is completed, so that the formation pressure is gradually raised and finally reaches a reasonable formation pressure.

11. Deep low-permeability heavy oil viscosity reduction pressure drive injection parameter optimization system, characterized in that: The deep low-permeability heavy oil viscosity reduction pressure drive injection parameter optimization system adopts the deep low-permeability heavy oil viscosity reduction pressure drive injection parameter optimization method described in any one of claims 1 to 10 to improve the single well productivity of deep low-permeability heavy oil viscosity reduction pressure drive.

Images