Steam diversion and heat insulation system and process method for thickened oil reservoir after multiple rounds of huff and puff

Abstract

The application discloses a steam diversion and heat insulation system after multi-round steam soaking of a heavy oil reservoir, which comprises, from a near wellbore zone to a deep formation, in order, a displacement slug, a heat solid sealing slug, an expandable modified vermiculite sealing and heat insulation slug, an N2 foam heat insulation slug and a gel pre-sealing slug, and the volume ratio of the slugs is (5-25):(5-10):(5-10):(15-30):(10-15); the gel pre-sealing slug and the heat solid sealing slug form a sealing boundary with strength respectively, the N2 foam heat insulation slug and the expandable modified vermiculite sealing and heat insulation slug filled between the gel pre-sealing slug and the heat solid sealing slug form two heat insulation layers, the two heat insulation layers and the two sealing boundaries form a sealing layer, and the thickness of the sealing layer is 5-10 meters. The application further discloses a process method of the steam diversion and heat insulation system after multi-round steam soaking of the heavy oil reservoir.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development, and relates to the field of heavy oil steam extraction, specifically the steam diversion insulation system and process method after multiple rounds of huff and puff in heavy oil reservoirs. Background Technology

[0002] After multiple rounds of steam huff and puff production, heavy oil reservoirs often experience steam channeling, leading to a significant drop in well production. The injected steam flows directionally along the channel, resulting in problems such as small steam sweep volume, low sweep efficiency, uneven reservoir development, severe steam heat loss, and low heat utilization efficiency, ultimately severely impacting reservoir development. Preventing and controlling steam channeling is a major challenge in heavy oil reservoir steam huff and puff production.

[0003] To address the steam channeling problem, commonly used on-site sealing and profile control techniques include high-temperature nitrogen foam profile control and high-temperature gel sealing. Both methods can improve development results to some extent. For example, Chinese invention patent application CN101280184A discloses a foam-curing profile control agent for steam injection wells. Its composition includes different proportions of curing slurry, foaming liquid, and nitrogen: A. The optimized formulation ratio of the foam-curing profile control agent is a 1:1 mass ratio of curing slurry to foaming liquid. B. The selected curing slurry is composed of modified silicate cement and a retarder, where the mass concentration of modified silicate is 15-40%, and the ratio of modified silicate cement to retarder is 5:1. C. The selected foaming liquid is composed of a certain concentration of nonionic surfactant AEO-SI and a stabilizer, where the mass concentration of AEO-SI is 3-8%, and the ratio of AEO-SI to stabilizer is 2:1. However, foam-cured profile control agents have a short shelf life and poor stability. As the number of injection cycles increases, the production enhancement effect of nitrogen foam profile control technology will become increasingly worse. For example, Chinese invention patent application CN 109025894A discloses a method for plugging steam leakage in horizontal wells for heavy oil thermal recovery, including the following steps: (1) inserting the steam injection string into the oil layer and using a general injection method to preheat the formation with steam; (2) injecting high-viscosity gel; (3) injecting silicate high-temperature plugging agent; (4) repeating steps (2) and (3) until the injection pressure requirements of the construction design are met; (5) injecting steam to heat the plugging agent and shutting in the well for 3-5 days; (6) injecting steam for injection and production. However, the gel system uses a high concentration and has a high cost. At high temperatures (≥150℃), the gelation time is generally less than 10 hours, resulting in poor deep migration ability of the system and failure to achieve deep leakage control.

[0004] To address the issue of low thermal efficiency, current main technologies employed are high-dryness stratified steam injection and gas-assisted steam huff and puff. For example, Chinese invention patent application CN 115596417A discloses a stratified steam drive extraction technology, specifically a stratified steam injection heating system. This system includes: a steam injection pipe; a heating device comprising multiple heating tubes arranged within the steam injection pipe along its height, with varying lengths; and a controller for controlling the heating temperature of the heating tubes. However, while high-dryness stratified steam injection technology improves steam thermal utilization efficiency to some extent, it cannot effectively reduce steam heat loss. Chinese invention patent application CN101592028A discloses a method for gas-assisted SAGD extraction of extra-heavy oil. The method involves selecting an oil layer at a depth of 530m, with a remaining oil saturation >0.50, a layer thickness >10.0m, horizontal permeability >250md, a vertical-to-horizontal permeability ratio >0.1, and a porosity >0.20. The oil layer must not contain continuously distributed impermeable mud or shale interlayers. Horizontal wells are drilled between the huff and puff vertical wells, with a well spacing of 35 meters, or a pair of horizontal wells are drilled at the bottom of the oil layer with a vertical distance of 6 meters. After three huff and puff cycles, thermal connectivity is established between the wells. Steam is continuously injected through the vertical wells. After three years of production through the horizontal wells, nitrogen and steam are injected through the vertical wells at a subsurface volume ratio of 0.5. Nitrogen injection is stopped after the total injection volume reaches 0.10 PV, and steam injection continues at a rate of 1.4m / s. 3 / d.ha.m, the bottom hole steam dryness is 70%, and the production-injection ratio is maintained at 1.2. However, although gas injection-assisted steam huff and puff technology improves the thermal utilization efficiency of steam to some extent, the gas tends to accumulate in the upper part of the reservoir due to gravity differentiation, which only reduces the heat loss at the top and still cannot significantly improve the thermal utilization efficiency.

[0005] Therefore, how to better solve the problems of severe steam heat loss and low heat utilization efficiency when steam injection is carried out in heavy oil reservoirs has become an urgent problem to be solved. Summary of the Invention

[0006] Purpose of the invention: In view of the shortcomings of the prior art, the present invention provides a steam diversion insulation system and process method after multiple rounds of huff and puff in heavy oil reservoirs. The present invention can block the steam channeling channel, reduce heat loss, expand the heat wave range and improve heat utilization efficiency, thereby improving the development effect of heavy oil reservoirs after high rounds of huff and puff.

[0007] Technical solution: A steam diversion insulation system following multiple rounds of huff and puff in heavy oil reservoirs, comprising sequentially adjacent displacement slugs, thermosetting sealing slugs, expandable modified vermiculite sealing insulation slugs, N2 foam insulation slugs, and gel pre-sealing slugs from near-wellbore to deep formation, wherein:

[0008] The volume ratio of the displacement plug, the thermosetting sealing plug, the expandable modified vermiculite sealing and insulating plug, the N2 foam insulating plug, and the gel pre-sealing plug is (5-25):(5-10):(5-10):(15-30):(10-15);

[0009] The pre-sealing plug of the gel and the thermosetting sealing plug each form a strong sealing boundary. The N2 foam insulation plug and the expandable modified vermiculite sealing insulation plug filled between the pre-sealing plug of the gel and the thermosetting sealing plug form two insulation layers. The two insulation layers and the two sealing boundaries form a sealing layer with a thickness of 5-10 meters.

[0010] Furthermore, the displacement slug is clean water or treated oilfield reinjection wastewater.

[0011] Furthermore, the thermosetting sealing segment is a phenolic resin thermosetting system, wherein:

[0012] The phenolic resin thermosetting system is composed of phenolic substances, formaldehyde, and water, wherein:

[0013] Based on the total mass of the phenolic resin thermosetting system, the phenolic substances account for 15wt%-30wt%, and the formaldehyde accounts for 15wt%-30wt%.

[0014] Furthermore, the phenolic substance is one of phenol, hydroquinone, resorcinol, and catechol.

[0015] Phenolic resin thermosetting systems can withstand temperatures up to 300℃. At low temperatures (usually 80℃), the viscosity is very low (10-50 mPa·s). When the temperature exceeds 120℃, the viscosity increases significantly, and the phenolic resin thermosetting system forms an irreversible cross-linked structure, which means it begins to cure. The curing time is 10h-72h.

[0016] Furthermore, the expandable modified vermiculite sealing and insulating plug is composed of a nonionic polymer, expandable modified vermiculite particles, and water, wherein:

[0017] Based on the total mass of the expandable modified vermiculite sealing and insulating slug, the nonionic polymer accounts for 0.3wt%-0.5wt%, the expandable modified vermiculite particles account for 0.5%-3wt%, and the balance is water.

[0018] The nonionic polymer is a nonionic polyacrylamide with a molecular weight of 5 million to 8 million. Under formation conditions, the viscosity of a 0.3% to 0.5% concentration of the nonionic polymer is above 20 mPa·s.

[0019] Furthermore, the initial particle size of the expandable modified vermiculite particles is 40-180μm. The initial expansion temperature of the expandable modified vermiculite plugging insulation slug is 160℃, the initial particle size is adjustable from 40-180μm, the expansion ratio is 2-8 times, and the heat transfer coefficient is low after expansion.

[0020] Furthermore, the N2 foam insulation plug is composed of a foaming agent and water, wherein:

[0021] Based on the total mass of the N2 foam insulation slug, the foaming agent accounts for 0.3wt%-0.5wt%, with the remainder being water;

[0022] The foaming agent is an alkyl sulfonate or alkylbenzene sulfonic acid.

[0023] Furthermore, the gel pre-sealing plug is composed of a polymer, a crosslinking agent, and water, wherein:

[0024] Based on the total mass of the gel pre-sealing plug, the polymer accounts for 0.3wt%-0.5wt%, the crosslinking agent accounts for 0.1wt%-0.5wt%, and the balance is water. The gel pre-sealing plug is an underground crosslinked polymer gel system with a gelation time of 8-24 hours and a temperature resistance of over 100℃.

[0025] Furthermore, the polymer is polyacrylamide with a molecular weight of 9 million to 10 million.

[0026] Furthermore, the crosslinking agent is one of formaldehyde, phenolic crosslinking system, or organochromium crosslinker.

[0027] Furthermore, the phenolic cross-linking system is a mixture of phenolic substances, formaldehyde, and water.

[0028] Furthermore, the organochromium crosslinker is a solution of organochromium, wherein the organochromium is one or more of chromium oxalate, chromium acetate, chromium citrate, chromium malonate, chromium propionate, and chromium lactate, preferably chromium lactate.

[0029] When a heavy oil reservoir enters a high-cycle huff and puff phase, and the cycle effect deteriorates or a steam channel forms, the steam diversion insulation system after multiple cycles of huff and puff described above can be used for treatment.

[0030] The process method for the steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in any of the above-mentioned methods includes the following steps:

[0031] (1) Inject gel pre-sealing plugs into the target formation, with the injection volume being 10%-15% of the pore volume of the gas channel.

[0032] (2) Inject N2 foam insulation plugs into the target formation, with the injection volume being 15%-30% of the pore volume of the gas channel.

[0033] (3) Inject expandable modified vermiculite into the target formation to seal and insulate the heat-insulating sluice, with the volume injection amount being 5%-10% of the pore volume of the gas channel.

[0034] (4) Inject thermosetting sealing plugs into the target formation, with a volumetric injection volume of 5%-10% of the pore volume of the gas channel.

[0035] (5) Injecting displacement slugs into the target formation, the volumetric injection amount being 5%-25% of the pore volume of the gas channel. The displacement slugs are used to push the thermosetting sealing slugs away from the wellhead.

[0036] (6) After shutting in the well, there is no need to wait; the next round of steam injection can be carried out directly.

[0037] Furthermore, slug optimization design is performed before step (1):

[0038] By quantitatively describing the steam leakage channel after multiple rounds of injection and output, and calculating the pore volume of the steam leakage channel, the design injection volume of each slug in the steam diversion insulation system is optimized, where:

[0039] The pore volume of the vapor channel is calculated using the following formula:

[0040]

[0041] V – Pore volume of the vapor channel, m 3 ;

[0042] H f —Radius of the hot zone, in meters;

[0043] L f —Length of the gas leakage channel, in meters;

[0044] —Thickness of the gas channel, in meters;

[0045] —Porosity;

[0046] α – Vertical permeability coefficient;

[0047] β – Horizontal permeability coefficient.

[0048] Furthermore, the high-viscosity gel pre-sealing plug is injected using slow, controlled-pressure injection at a speed of 10-30 m / s. 3 / h, injection pressure not exceeding 20MPa;

[0049] Low-viscosity N2 foam insulation slugs are injected using rapid pressure-controlled injection at a rate of 50-100 m³ / h. 3 / h, injection pressure not exceeding 20MPa. This allows the foam to rapidly advance along the high-permeability channel, encapsulating nitrogen in the pre-seal plug of the gel and the subsequent expandable modified vermiculite sealing and insulation plug, preventing nitrogen from accumulating at the top of the reservoir under gravity separation.

[0050] After the steam-to-insulation system is injected into the formation, steam is injected into the formation. When the temperature of the thermosetting sealing block reaches 120°C, it begins to solidify. When the temperature continues to rise to 160°C, the expandable modified vermiculite begins to expand, blocking the large steam channel. N2 is blocked in the interlayer formed by the pre-gel and the thermosetting sealing, forming a sealing and insulation layer with front and rear sealing boundaries.

[0051] Compared with existing technologies, the present invention has the following advantages:

[0052] 1. The steam diversion insulation system is suitable for heavy oil reservoirs where steam channeling occurs after high-volume steam injection. It can meet reservoir conditions of 100-300℃ and overcomes the difficulties of conventional sealing systems in terms of temperature difference resistance, short sealing period, and inability to be injected into deep reservoirs.

[0053] 2. After the steam diversion insulation system is injected, steam can be directly injected for subsequent cycle production without the need for long well shut-in waiting, saving economic costs and improving the efficiency of heavy oil reservoir development.

[0054] 3. Expandable modified vermiculite can withstand temperatures above 300℃. It can slowly expand at 160℃, with an expansion time of 1-5 days and an expansion ratio of 2-8 times. The thermal conductivity of the expanded modified vermiculite system is further reduced, and it is more tightly bonded to the formation pores, ensuring the sealing strength and further improving the sealing and heat insulation effect.

[0055] 4. The gel pre-sealing slug mainly enters the deep formation along the high permeability channels of steam channeling, effectively blocking the high permeability channeling. The thermosetting sealing slug mainly blocks the high-temperature area according to the development of the thermal field, reducing heat loss and simultaneously realizing the steam diversion function.

[0056] 5. By combining two end-capping plugs (thermosetting end-capping plug and gel pre-end-capping plug) and two insulation plugs (expandable modified vermiculite sealing insulation plug and N2 foam insulation plug), the system's sealing and insulation capabilities are fully guaranteed while the thermal conductivity of the sealing and insulation system is greatly reduced. At the same time, the designed displacement plug further enhances the system's deep formation migration capability and strengthens the system's deep sealing and insulation effect. Attached Figure Description

[0057] The accompanying drawings are intended only to illustrate and explain the present invention and do not limit the scope of the invention.

[0058] Figure 1 This is a schematic diagram of the steam flow channel and heat flow field before the steam diversion insulation system after multiple rounds of heavy oil reservoir steam transfer using the present invention.

[0059] Figure 2 This diagram illustrates the blockage of the steam channel and the reversal of the heat flow field after the steam diversion insulation system following multiple cycles of huff and puff in a heavy oil reservoir, as described in this invention.

[0060] in:

[0061] A-Hot Zone

[0062] B-Cold Zone

[0063] C-heat flow field

[0064] L f - Length of the vapor channel

[0065] H f - Radius of the thermal zone

[0066] 1-Pre-sealing plug for gel

[0067] 2-N2 foam insulation slug

[0068] 3-Expandable modified vermiculite plugging and insulation slug

[0069] 4-Thermosetting sealing segment plug Detailed Implementation

[0070] The specific embodiments of the present invention are described in detail below.

[0071] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0072] Figure 1 This is a schematic diagram of the steam flow channel and heat flow field before the steam diversion insulation system after multiple rounds of heavy oil reservoir steam transfer using the present invention. Figure 2 This diagram illustrates the sealing of steam channeling pathways and the reversal of the heat flow field after multiple rounds of steam diversion insulation system applied to heavy oil reservoirs according to the present invention. Figure 2 It can be seen that after multiple rounds of steam diversion and insulation process, the steam channel is effectively blocked, the heating area is significantly expanded, and the hot fluid along the steam channel is diverted to other unaffected oil displacement areas, resulting in a significant improvement in production efficiency.

[0073] Example 1

[0074] Taking well A1 in a block of a heavy oil reservoir with an oil layer depth of 800m and a ground pressure of 7.5MPa, the gas channeling channel volume was obtained as 4352m³ after multiple rounds of injection and injection by quantitatively describing the gas channeling channel after multiple rounds of injection and injection. 3 The permeability increased from 4.06 μm 2 Increased to 42.04μm 2 The porosity increased from 33.7% to 40.4%. Well A1 entered a high-cycle throughput phase.

[0075] The steam diversion insulation system following multiple rounds of huff and puff in heavy oil reservoirs includes, sequentially from near-wellbore to deep formation, displacement slugs, thermosetting sealing slugs, expandable modified vermiculite sealing insulation slugs, N2 foam insulation slugs, and gel pre-sealing slugs, among which:

[0076] The volume ratio of the displacement plug, the thermosetting sealing plug, the expandable modified vermiculite sealing and insulating plug, the N2 foam insulating plug, and the gel pre-sealing plug is 10:8:8:24:12.

[0077] The pre-sealing plug of the gel and the thermosetting sealing plug each form a strong sealing boundary. The N2 foam insulation plug and the expandable modified vermiculite sealing insulation plug filled between the pre-sealing plug of the gel and the thermosetting sealing plug form two insulation layers. The two insulation layers and the two sealing boundaries form a sealing layer with a thickness of 8 meters.

[0078] Furthermore, the replacement plug is made of water.

[0079] Furthermore, the thermosetting sealing segment is a phenolic resin thermosetting system, wherein:

[0080] The phenolic resin thermosetting system is composed of phenolic substances, formaldehyde, and water, wherein:

[0081] Based on the total mass of the phenolic resin thermosetting system, the phenolic substances account for 20 wt%, and the formaldehyde accounts for 20 wt%.

[0082] Furthermore, the phenolic substance is phenol.

[0083] The thermosetting sealing block (phenolic resin thermosetting system) can withstand temperatures up to 300℃. At low temperatures (usually 80℃), the viscosity is very low (35mpa·s). When the temperature exceeds 120℃, the viscosity increases significantly, and the phenolic resin thermosetting system forms an irreversible cross-linked structure, which means it begins to cure. The curing time is 20h.

[0084] Furthermore, the expandable modified vermiculite sealing and insulating plug is composed of a nonionic polymer, expandable modified vermiculite particles, and water, wherein:

[0085] Based on the total mass of the expandable modified vermiculite sealing and insulating slug, the nonionic polymer accounts for 0.4 wt%, the expandable modified vermiculite particles account for 2 wt%, and the remainder is water.

[0086] The nonionic polymer is nonionic polyacrylamide with a molecular weight of 6.5 million. Under formation conditions, the viscosity of a 0.3%-0.5% concentration of the nonionic polymer is above 20 mPa·s.

[0087] Furthermore, the initial particle size of the expandable modified vermiculite particles is 50 μm. The initial expansion temperature of the expandable modified vermiculite plugging insulation slug is 160℃, the initial particle size is adjustable from 40 to 180 μm, the expansion ratio is 4 to 6 times, and the heat transfer coefficient is low after expansion.

[0088] Furthermore, the N2 foam insulation plug is composed of a foaming agent and water, wherein:

[0089] Based on the total mass of the N2 foam insulation slug, the foaming agent accounts for 0.4 wt%, and the remainder is water;

[0090] The foaming agent is sodium alkyl sulfonate.

[0091] Furthermore, the gel pre-sealing plug is composed of a polymer, a crosslinking agent, and water, wherein:

[0092] Based on the total mass of the gel pre-sealing plug, the polymer accounts for 0.4 wt%, the crosslinking agent accounts for 0.2 wt%, and the balance is water. The gel pre-sealing plug is an underground crosslinked polymer gel system with a gelation time of 18 hours and a temperature resistance of over 100℃.

[0093] Furthermore, the polymer is polyacrylamide with a molecular weight of 9.5 million.

[0094] Furthermore, the crosslinking agent is formaldehyde.

[0095] The process method for the steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs described in any of the above-mentioned methods, applied to well A1, includes the following steps:

[0096] (1) Inject gel pre-sealing plugs into the target formation, with the injection volume being 12% of the pore volume of the gas channel.

[0097] (2) Inject N2 foam insulation plugs into the target formation, with the injection volume being 24% of the pore volume of the gas channel.

[0098] (3) Inject expandable modified vermiculite into the target formation to seal and insulate the heat-insulating sluice, with the volume injection amount being 8% of the pore volume of the gas channel;

[0099] (4) Inject thermosetting sealing plugs into the target formation, with the injection volume being 8% of the pore volume of the gas channel.

[0100] (5) Injecting displacement slugs into the target formation, the volume of which is 20% of the pore volume of the gas channel. The displacement slugs are used to push the thermosetting sealing slugs away from the wellhead.

[0101] (6) After shutting in the well, there is no need to wait; the next round of steam injection can be carried out directly.

[0102] Furthermore, slug optimization design is performed before step (1):

[0103] By quantitatively describing the steam leakage channel after multiple rounds of injection and output, and calculating the pore volume of the steam leakage channel, the design injection volume of each slug in the steam diversion insulation system is optimized, where:

[0104] The pore volume of the vapor channel is calculated using the following formula:

[0105]

[0106] V – Pore volume of the vapor channel, m 3 ;

[0107] H f —Radius of the hot zone, in meters;

[0108] L f —Length of the gas leakage channel, in meters;

[0109] —Thickness of the gas channel, in meters;

[0110] —Porosity;

[0111] α – Vertical permeability coefficient;

[0112] β – Horizontal permeability coefficient.

[0113] Furthermore, the high-viscosity gel pre-sealing plug is injected using slow, controlled-pressure injection at a speed of 20m. 3 / h, injection pressure 15MPa;

[0114] The low-viscosity N2 foam insulation slug uses rapid pressure-controlled injection at an injection speed of 80m. 3 / h, injection pressure 15MPa.

[0115] After multiple rounds of steam diversion and insulation treatment, the steam channel of Well A1 was effectively blocked, the heating area was significantly expanded, and the hot fluid along the steam channel was diverted to other unaffected oil displacement areas, resulting in a significant improvement in production efficiency.

[0116] Example 2

[0117] Taking well A2 in a block of a heavy oil reservoir, with an oil layer depth of 760m and a ground pressure of 7.0MPa, a quantitative description of the gas channeling pathway after multiple rounds of injection and injection was performed, yielding a gas channeling volume of 3953m³. 3 The permeability increased from 3.86 μm 2 Increased to 36.09μm 2 The porosity increased from 32.7% to 41.4%. Well A2 entered a high-cycle throughput phase.

[0118] The steam diversion insulation system following multiple rounds of huff and puff in heavy oil reservoirs includes, sequentially from near-wellbore to deep formation, displacement slugs, thermosetting sealing slugs, expandable modified vermiculite sealing insulation slugs, N2 foam insulation slugs, and gel pre-sealing slugs, among which:

[0119] The volume ratio of the displacement plug, the thermosetting sealing plug, the expandable modified vermiculite sealing and insulating plug, the N2 foam insulating plug, and the gel pre-sealing plug is 25:10:10:15:15.

[0120] The pre-sealing plug of the gel and the thermosetting sealing plug each form a strong sealing boundary. The N2 foam insulation plug and the expandable modified vermiculite sealing insulation plug filled between the pre-sealing plug of the gel and the thermosetting sealing plug form two insulation layers. The two insulation layers and the two sealing boundaries form a sealing layer with a thickness of 10 meters.

[0121] Furthermore, the displacement sluice is treated oilfield reinjection wastewater.

[0122] Furthermore, the thermosetting sealing segment is a phenolic resin thermosetting system, wherein:

[0123] The phenolic resin thermosetting system is composed of phenolic substances, formaldehyde, and water, wherein:

[0124] Based on the total mass of the phenolic resin thermosetting system, the phenolic substances account for 15 wt% and the formaldehyde accounts for 15 wt%.

[0125] Furthermore, the phenolic substance is hydroquinone.

[0126] Furthermore, the expandable modified vermiculite sealing and insulating plug is composed of a nonionic polymer, expandable modified vermiculite particles, and water, wherein:

[0127] Based on the total mass of the expandable modified vermiculite sealing and insulating slug, the nonionic polymer accounts for 0.3 wt%, the expandable modified vermiculite particles account for 0.5%, and the remainder is water.

[0128] The nonionic polymer is nonionic polyacrylamide with a molecular weight of 5 million.

[0129] Furthermore, the initial particle size of the expandable modified vermiculite particles is 40 μm.

[0130] Furthermore, the N2 foam insulation plug is composed of a foaming agent and water, wherein:

[0131] Based on the total mass of the N2 foam insulation slug, the foaming agent accounts for 0.3 wt%, and the balance is water;

[0132] The foaming agent is alkylbenzene sulfonic acid.

[0133] Furthermore, the gel pre-sealing plug is composed of a polymer, a crosslinking agent, and water, wherein:

[0134] Based on the total mass of the gel pre-sealing plug, the polymer accounts for 0.3 wt%, the crosslinking agent accounts for 0.1 wt%, and the remainder is water.

[0135] Furthermore, the polymer is polyacrylamide with a molecular weight of 9 million.

[0136] Furthermore, the crosslinking agent is a phenolic crosslinking system.

[0137] The process method for the steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs described in any of the above-mentioned methods, for the frequent treatment of well A2, includes the following steps:

[0138] (1) Inject gel pre-sealing plugs into the target formation, with the injection volume being 15% of the pore volume of the gas channel.

[0139] (2) Inject N2 foam insulation plugs into the target formation, with the injection volume being 15% of the pore volume of the gas channel;

[0140] (3) Inject expandable modified vermiculite into the target formation to seal and insulate the heat-insulating sluice, with the volume injection amount being 10% of the pore volume of the gas channel.

[0141] (4) Inject thermosetting sealing plugs into the target formation, with the injection volume being 5% of the pore volume of the gas channel.

[0142] (5) Injecting displacement slugs into the target formation, the volume injection amount being -25% of the pore volume of the gas channel. The displacement slugs are used to push the thermosetting sealing slugs away from the wellhead.

[0143] (6) After shutting in the well, there is no need to wait; the next round of steam injection can be carried out directly.

[0144] Furthermore, slug optimization design is performed before step (1):

[0145] By quantitatively describing the steam leakage channel after multiple rounds of injection and output, and calculating the pore volume of the steam leakage channel, the design injection volume of each slug in the steam diversion insulation system is optimized, where:

[0146] The pore volume of the vapor channel is calculated using the following formula:

[0147]

[0148] V – Pore volume of the vapor channel, m 3 ;

[0149] H f —Radius of the hot zone, in meters;

[0150] L f —Length of the gas leakage channel, in meters;

[0151] —Thickness of the gas channel, in meters;

[0152] —Porosity;

[0153] α – Vertical permeability coefficient;

[0154] β – Horizontal permeability coefficient.

[0155] Furthermore, the high-viscosity gel pre-sealing plug is injected using slow, controlled-pressure injection at a speed of 10m. 3 / h, injection pressure 18MPa;

[0156] The low-viscosity N2 foam insulation slug uses rapid pressure-controlled injection at an injection speed of 50m. 3 / h, injection pressure 18MPa.

[0157] After multiple rounds of steam diversion and insulation treatment, the steam channel of Well A2 was effectively blocked, the heating area was significantly expanded, and the hot fluid along the steam channel was diverted to other unaffected oil displacement areas, resulting in a significant improvement in production efficiency.

[0158] Example 3

[0159] Taking well A3 in a block of a heavy oil reservoir, with an oil layer depth of 850m and a ground pressure of 7.9MPa, a quantitative description of the gas channeling pathway after multiple rounds of injection and injection was performed, yielding a gas channeling volume of 4842m³. 3 The permeability increased from 4.57 μm 2 Increased to 48.22μm 2 The porosity increased from 35.7% to 46.4%. Well A3 entered a high-cycle throughput phase.

[0160] The steam diversion insulation system following multiple rounds of huff and puff in heavy oil reservoirs includes, sequentially from near-wellbore to deep formation, displacement slugs, thermosetting sealing slugs, expandable modified vermiculite sealing insulation slugs, N2 foam insulation slugs, and gel pre-sealing slugs, among which:

[0161] The volume ratio of the displacement plug, the thermosetting sealing plug, the expandable modified vermiculite sealing and insulating plug, the N2 foam insulating plug, and the gel pre-sealing plug is 5:10:5:15:10.

[0162] The pre-sealing plug of the gel and the thermosetting sealing plug each form a strong sealing boundary. The N2 foam insulation plug and the expandable modified vermiculite sealing insulation plug filled between the pre-sealing plug of the gel and the thermosetting sealing plug form two insulation layers. The two insulation layers and the two sealing boundaries form a sealing layer with a thickness of 5 meters.

[0163] Furthermore, the replacement plug is made of water.

[0164] Furthermore, the thermosetting sealing segment is a phenolic resin thermosetting system, wherein:

[0165] The phenolic resin thermosetting system is composed of phenolic substances, formaldehyde, and water, wherein:

[0166] Based on the total mass of the phenolic resin thermosetting system, the phenolic substances account for 30 wt% and the formaldehyde accounts for 30 wt%.

[0167] Furthermore, the phenolic substance is resorcinol. In another embodiment, the phenolic substance is catechol.

[0168] Furthermore, the expandable modified vermiculite sealing and insulating plug is composed of a nonionic polymer, expandable modified vermiculite particles, and water, wherein:

[0169] Based on the total mass of the expandable modified vermiculite sealing and insulating slug, the nonionic polymer accounts for 0.5 wt%, the expandable modified vermiculite particles account for 3 wt%, and the remainder is water.

[0170] The nonionic polymer is nonionic polyacrylamide with a molecular weight of 8 million.

[0171] Furthermore, the initial particle size of the expandable modified vermiculite particles is 80 μm.

[0172] Furthermore, the N2 foam insulation plug is composed of a foaming agent and water, wherein:

[0173] Based on the total mass of the N2 foam insulation slug, the foaming agent accounts for 0.5 wt%, and the remainder is water;

[0174] The foaming agent is potassium alkyl sulfonate.

[0175] Furthermore, the gel pre-sealing plug is composed of a polymer, a crosslinking agent, and water, wherein:

[0176] Based on the total mass of the gel pre-sealing plug, the polymer accounts for 0.5 wt%, the crosslinking agent accounts for 0.5 wt%, and the balance is water.

[0177] Furthermore, the polymer is polyacrylamide with a molecular weight of 10 million.

[0178] Furthermore, the crosslinking agent is an organochromium crosslinker.

[0179] The process method for the steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs described in any of the above-mentioned methods, applied to well A3, includes the following steps:

[0180] (1) Inject gel pre-sealing plugs into the target formation, with the injection volume being 10% of the pore volume of the gas channel.

[0181] (2) Inject N2 foam insulation plugs into the target formation, with the injection volume being 15% of the pore volume of the gas channel;

[0182] (3) Inject expandable modified vermiculite into the target formation to seal and insulate the heat-insulating sluice, with the volume injection amount being 5% of the pore volume of the gas channel;

[0183] (4) Inject thermosetting sealing plugs into the target formation, with the injection volume being 10% of the pore volume of the gas channel.

[0184] (5) Injecting displacement slugs into the target formation, the volume injection amount is 5% of the pore volume of the gas channel. The displacement slugs are used to push the thermosetting sealing slugs away from the wellhead.

[0185] (6) After shutting in the well, there is no need to wait; the next round of steam injection can be carried out directly.

[0186] Furthermore, slug optimization design is performed before step (1):

[0187] By quantitatively describing the steam leakage channel after multiple rounds of injection and output, and calculating the pore volume of the steam leakage channel, the design injection volume of each slug in the steam diversion insulation system is optimized, where:

[0188] The pore volume of the vapor channel is calculated using the following formula:

[0189]

[0190] V – Pore volume of the vapor channel, m 3 ;

[0191] H f —Radius of the hot zone, in meters;

[0192] L f —Length of the gas leakage channel, in meters;

[0193] —Thickness of the gas channel, in meters;

[0194] —Porosity;

[0195] α – Vertical permeability coefficient;

[0196] β – Horizontal permeability coefficient.

[0197] Furthermore, the high-viscosity gel pre-sealing plug is injected using slow, controlled-pressure injection at a speed of 30m. 3 / h, injection pressure 10MPa;

[0198] The low-viscosity N2 foam insulation slug uses rapid pressure-controlled injection at a speed of 100m. 3 / h, injection pressure 10MPa.

[0199] After multiple rounds of steam diversion and insulation treatment, the steam channel of Well A3 was effectively blocked, the heating area was significantly expanded, and the hot fluid along the steam channel was diverted to other unaffected oil displacement areas, resulting in a significant improvement in production efficiency.

[0200] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs, characterized in that, This includes, sequentially from near-wellbore to deep formation, displacement slugs, thermosetting sealing slugs, expandable modified vermiculite sealing and insulation slugs, N2 foam insulation slugs, and gel pre-sealing slugs, among which: The volume ratio of the displacement plug, the thermosetting sealing plug, the expandable modified vermiculite sealing and insulating plug, the N2 foam insulating plug, and the gel pre-sealing plug is (5-25):(5-10):(5-10):(15-30):(10-15); The pre-sealing plug of the gel and the thermosetting sealing plug each form a strong sealing boundary. The N2 foam insulation plug and the expandable modified vermiculite sealing insulation plug filled between the pre-sealing plug of the gel and the thermosetting sealing plug form two insulation layers. The two insulation layers and the two sealing boundaries form a sealing layer with a thickness of 5-10 meters. The thermal conductivity of the expanded modified vermiculite system is further reduced, and it binds more tightly to the formation pores, ensuring the strength of the seal and further improving the sealing and insulation effect.

2. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 1, characterized in that, The displacement slug is clean water or treated oilfield reinjection wastewater.

3. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 1, characterized in that, The thermosetting sealing plug is a phenolic resin thermosetting system, which is composed of phenolic substances, formaldehyde, and water, wherein: Based on the total mass of the phenolic resin thermosetting system, the phenolic substances account for 15wt%-30wt%, and the formaldehyde accounts for 15wt%-30wt%.

4. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 3, characterized in that, The phenolic substance is one of phenol, hydroquinone, resorcinol, and catechol.

5. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 1, characterized in that, The expandable modified vermiculite sealing and insulating plug is composed of a nonionic polymer, expandable modified vermiculite particles, and water, wherein: Based on the total mass of the expandable modified vermiculite sealing and insulating slug, the nonionic polymer accounts for 0.3wt%-0.5wt%, the expandable modified vermiculite particles account for 0.5wt%-3wt%, and the balance is water.

6. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 5, characterized in that, The nonionic polymer is a nonionic polyacrylamide with a molecular weight of 5 million to 8 million; The initial particle size of expandable modified vermiculite particles is 40-180 μm.

7. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 1, characterized in that, The N2 foam insulation plug is composed of a foaming agent and water, wherein: Based on the total mass of the N2 foam insulation slug, the foaming agent accounts for 0.3wt%-0.5wt%, with the remainder being water; The foaming agent is an alkyl sulfonate or alkylbenzene sulfonic acid.

8. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 1, characterized in that, The gel pre-sealing plug is composed of a polymer, a crosslinking agent, and water, wherein: Based on the total mass of the gel pre-sealing plug, the polymer accounts for 0.3wt%-0.5wt%, the crosslinking agent accounts for 0.1wt%-0.5wt%, and the balance is water; The polymer is polyacrylamide with a molecular weight of 9 million to 10 million.

9. The steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 8, characterized in that, The crosslinking agent is one of formaldehyde, phenolic crosslinking system, or organochromium crosslinker.

10. The process method for the steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Inject gel pre-sealing plugs into the target formation, with the injection volume being 10%-15% of the pore volume of the gas channel. (2) Inject N2 foam insulation plugs into the target formation, with the injection volume being 15%-30% of the pore volume of the gas channel. (3) Inject expandable modified vermiculite into the target formation to seal and insulate the heat-insulating sluice, with the volume injection amount being 5%-10% of the pore volume of the gas channel. (4) Inject thermosetting sealing plugs into the target formation, with a volumetric injection volume of 5%-10% of the pore volume of the gas channel. (5) Injecting displacement slugs into the target formation, the volumetric injection amount being 5%-25% of the pore volume of the gas channel. The displacement slugs are used to push the thermosetting sealing slugs away from the wellhead. (6) After shutting in the well, there is no need to wait; the next round of steam injection can be carried out directly.

11. The process method for the steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 10, characterized in that, Slug optimization design is performed before step (1): By quantitatively describing the steam leakage channel after multiple rounds of injection and output, and calculating the pore volume of the steam leakage channel, the design injection volume of each slug in the steam diversion insulation system is optimized, where: The pore volume of the vapor channel is calculated using the following formula: V – Pore volume of the vapor channel, m 3 ; H f —Radius of the hot zone, in meters; L f —Length of the gas leakage channel, in meters; —Thickness of the gas channel, in meters; —Porosity; α – Vertical permeability coefficient; β – Horizontal permeability coefficient.

12. The process method for the steam diversion insulation system after multiple rounds of huff and puff in heavy oil reservoirs as described in claim 10, characterized in that, For high-viscosity gel pre-sealing plugs, slow-speed controlled-pressure injection is used, with an injection speed of 10-30m. 3 / h, injection pressure not exceeding 20MPa; Low-viscosity N2 foam insulation slugs are injected using rapid pressure-controlled injection at a rate of 50-100 m³ / h. 3 / h, injection pressure not exceeding 20MPa.

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