Injection-production string and method for improving recovery efficiency of thermal recovery horizontal well

Abstract

The invention provides an injection-production pipe column and method for improving the recovery ratio of a thermal recovery horizontal well, the injection-production method for improving the recovery ratio of the thermal recovery horizontal well adopts the injection-production pipe column for improving the recovery ratio of the thermal recovery horizontal well, and comprises the following steps: step 1, determining the injection amount of each parameter injected into an oil well; 2, combined fluid of high-dryness steam, a viscosity reducer, a high-temperature-resistant oil displacement agent and foam is injected into the oil reservoir through the horizontal well, and then the high-dryness steam is injected; 3, the injected combined fluid and the high dry steam form multiple sections of continuous balanced high-temperature steam cavities in the injection-production pipe column for improving the recovery efficiency of the thermal recovery horizontal well, and balanced steam injection is achieved; 4, the optimal oil discharge angle is designed; and 5, the injection-production effect of the implementation well is analyzed. According to the method, the steam injection effect and the liquid production profile can be monitored, then the steam distribution position of each section is optimized, and the overall recovery efficiency and economic benefits of the heavy oil reservoir are improved.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to an injection-production pipe string and a method for improving the recovery rate of a thermal horizontal well. Background Art

[0002] The geological reserves of heavy oil in the world far exceed those of conventional crude oil. With the increasing demand for oil, heavy oil has a strategic position as an alternative to conventional oil energy, as it is several to ten times higher than conventional crude oil resources. Heavy oil resources are widely distributed, mainly in the United States, Venezuela, Canada, the Soviet Union, etc., with geological reserves of about 4000×10 8 China's heavy oil asphalt resources are widely distributed, and the estimated heavy oil resources can reach 30×10 8 t or more. At present, the development of horizontal wells mainly includes steam huff and puff, steam drive, HDCS, HDNS, SAGD technology, etc. The development of conventional thermal recovery horizontal wells is affected by reservoir heterogeneity, the horizontal section is unevenly used, and the contradiction of steam channeling is very prominent. HDCS and HDNS technologies are mainly used in super-heavy oil reservoirs. When the above two technologies are used, the steam chamber is affected by the steam injection pressure and generally does not develop upward, but is more likely to develop on both sides of the horizontal well, which limits the effect of horizontal well development. SAGD technology has higher requirements for reservoir thickness (oil layer thickness ≥ 15m). For oil layers with interlayer development or oil layer thickness ≤ 15m, the economic benefits of this technology become worse. At present, the development of heavy oil reservoirs in China is mainly based on steam huff and puff development. Due to the high average huff and puff rounds, most thermal recovery development wells are in the multi-round huff and puff stage. Affected by factors such as low reservoir pressure and serious steam channeling problems, they present problems such as low thermal efficiency of injected steam and poor development effect. Horizontal wells have become an important means of increasing and stabilizing production due to their advantages such as high well-controlled reserves and large oil drainage area.

[0003] After heavy oil thermal recovery entered multiple rounds of huff and puff, reservoir heterogeneity, edge and bottom water invasion, and unreasonable steam injection technology led to uneven steam absorption profiles in the horizontal section, large differences in the degree of utilization, and high water content in the cycle. The advantage of the large oil leakage area of ​​the horizontal well could not be effectively utilized, which seriously affected the development effect of the thermal recovery horizontal well. With the increase of the huff and puff rounds, the reservoir heterogeneity intensified, steam channeling and high water content became increasingly complex, and steam mainly flowed ineffectively in areas with low oil saturation. There was still enriched oil near the well that was difficult to effectively utilize, and the steam utilization rate was low. Efficient adjustment of the injection and production profile of the long horizontal section can improve the phenomenon of uneven steam absorption in the plane, realize balanced and effective utilization of the reservoir, increase the utilization rate and recovery rate, and achieve quality and efficiency improvement in the development of heavy oil reservoirs.

[0004] In the Chinese patent application with application number: CN201810086297.6, a thermal well forced segmentation injection and production string and method are mainly provided. The injection and production string includes a steam injection and oil production integrated pump, a self-adjusting uniform steam injection device, a self-adjusting oil well liquid inlet device, and a steam injection string plug connected to the oil pipe from top to bottom in sequence. The self-adjusting uniform steam injection device and the self-adjusting oil well liquid inlet device are grouped as a group, and the number is set to at least two groups. The self-adjusting uniform steam injection device and the self-adjusting oil well liquid inlet device of each group correspond to the same injection and production layer at the same time. The oil pipe is also connected to a steam injection expansion packer, which is isolated on the inner wall of the thermochemical isolation plug in the casing. The number of the steam injection expansion packer and the thermochemical isolation plug is set to be consistent and at least three are set. Each thermochemical isolation plug forces the injection and production layer to be segmented. It can overcome the problems of uneven production, steam channeling and high water content caused by heterogeneity during steam injection and production in horizontal wells, thereby improving the overall recovery rate and economic benefits of the oil field. Although the packer and self-adjusting injector overcome the uneven production caused by heterogeneity in the injection and production process of horizontal wells, the process string used cannot achieve equal dryness steam distribution, which in turn affects the production degree of each section of the horizontal section, resulting in large differences in the production degree.

[0005] In the Chinese patent application with application number: CN201810159365.7, a stratified steam injection pipe column and method under the general sand control of thermal production straight inclined wells are involved. The process steam injection pipe column is mainly suitable for the stratified steam injection process of straight inclined wells. The process pipe column uses the density difference between the gas and liquid phases to establish a liquid phase separation of a certain thickness. The establishment of phase separation can effectively improve the dryness of the steam injection in the lower oil layer, reduce the problem of the small steam absorption ratio of the lower oil layer caused by steam overburden and oil layer heterogeneity, and then use interlayer separation and critical flow distributors to ensure the effective isolation of the upper and lower oil layers under the general sand control conditions of the straight inclined well, and improve the effective utilization rate of steam thermal energy and the overall utilization effect of the oil layer. However, this technology is limited by the pipe column structure, and cannot test the suction profile and liquid production profile of each layer in real time, and cannot provide guidance on the evaluation of steam injection effect and production effect.

[0006] In the Chinese patent application with application number: CN201610947834.2, an oil and gas production device for oil fields is involved, in particular, an integrated injection and production device for horizontal wells. The invention also relates to a method for using such an integrated injection and production device to achieve steam injection and oil production. The integrated injection and production device disclosed in the invention is composed of a first insulated oil pipe, an insulated downhole compensator, a second insulated oil pipe, an integrated injection and production pump, a third insulated oil pipe, a packer, an oil pipe and at least one steam injection and oil production unit connected in sequence. By integrating the design of the steam injection and oil production device, a set of pipe strings is realized for horizontal well steam injection and production, which not only simplifies the process and avoids the occurrence of complex situations, but also can alleviate the contradiction of uneven use of horizontal wells in both the steam injection and production stages. However, since this technology is an integrated injection and production device, it does not take into account the real-time monitoring of the production process and the steam injection process, and cannot adjust the next step measures in time according to the steam injection and production effects.

[0007] In the Chinese patent application with application number: CN201810086297.6, a thermal well forced segmentation injection and production string and method are involved. The injection and production string includes a steam injection and oil production integrated pump, a self-adjusting uniform steam injection device, a self-adjusting oil well liquid inlet device, and a steam injection string plug connected to the oil pipe from top to bottom in sequence. The self-adjusting uniform steam injection device and the self-adjusting oil well liquid inlet device are a group, and the number is set as at least two groups. Each group of self-adjusting uniform steam injection device and self-adjusting oil well liquid inlet device corresponds to the same injection and production layer at the same time. The oil pipe is also connected to a steam injection expansion packer, which is isolated on the inner wall of the thermochemical isolation plug in the casing. The number of the steam injection expansion packer and the thermochemical isolation plug is set to be consistent and at least three are set. Each thermochemical isolation plug forces the injection and production layer to be segmented. It can overcome the problems of uneven production, steam channeling and high water content caused by heterogeneity in horizontal well steam injection and production, thereby improving the overall recovery rate and economic benefits of the oil field. However, this technology cannot increase the oil leakage during the recovery process due to the limitation of the pipe string structure, which in turn affects the recovery effect.

[0008] The above existing technologies are greatly different from the present invention and fail to solve the technical problem we want to solve. For this reason, we have invented a new injection and production string and method for improving the recovery rate of thermal horizontal wells. Summary of the invention

[0009] The purpose of the present invention is to provide an injection and production string and method for improving the recovery rate of thermal horizontal wells by monitoring the injection and production profile of the entire wellbore and analyzing the injection and production effect of the implementation well through real-time collected injection and production data.

[0010] The object of the present invention can be achieved through the following technical measures: an injection and production string for improving the recovery rate of thermal horizontal wells, the injection and production string for improving the recovery rate of thermal horizontal wells includes multiple isolation units, a thermosensitive packer, an injection and production integrated pump, a sucker rod, an optical fiber and a ground signal processor, each isolation unit includes an oil drain, a constant flow dispenser, a cyclone equal dryness distributor and an interlayer packer connected in sequence, the thermosensitive packer isolates the multiple isolation units in the horizontal section of the horizontal well, one end of the injection and production integrated pump is connected to the thermosensitive packer, and the other end is connected to the sucker rod, the optical fiber is connected to the ground signal processor and is lowered into the oil layer to transmit the collected injection and production data to the ground signal processor, and the ground signal processor processes the injection and production data to obtain the actual situation downhole.

[0011] The purpose of the present invention can also be achieved by the following technical measures:

[0012] The number of the plurality of isolation units is equal to the number of optimized horizontal well segments.

[0013] The swirl flow equal dryness distributor comprises an outer tube of the swirl flow equal dryness distributor, an outer spiral and an inner spiral. The outer spiral and the inner spiral are both located in the outer tube of the swirl flow equal dryness distributor. The outer spiral surface turns right, and the inner spiral surface turns left, forming a test channel with a double spiral structure.

[0014] The constant flow dispenser adopts a critical flow nozzle structure, and is designed with a steam flow range of 4-15t / h, a pressure range of 8-21MPa, and a dryness range of 60-85%.

[0015] The steam flow in the constant flow dispenser belongs to the typical wet steam flow, and the critical flow control equation of wet steam is:

[0016]

[0017] Wherein, W is the wet steam flow rate, t / h; Y is the wet steam expansion coefficient; d is the diameter of the Venturi nozzle throat, mm; H is the length of the Venturi nozzle throat, mm; ρ is the wet steam density, kg / m3; P1 is the critical flow nozzle inlet pressure, MPa.

[0018] The constant flow dispenser is located at a distance of 3 to 5 times the pipe diameter of the cyclone equal dryness distributor downstream of the cyclone equal dryness distributor.

[0019] The oil drainer includes a main body, a pressure cap, a steel ball and a spring. The two ends of the oil drainer are connected to the upper joint and the lower joint of the oil pipe. The spring is installed at the oil drain hole on the inner wall of the main body. The steel ball is installed between the spring and the pressure cap so that the steel ball is just stuck between the pressure cap and the spring.

[0020] The size of the spring and the inner wall hole of the main body are different, so that the spring can be just stuck on the inner wall hole and play the role of a spring base. The oil drain hole at the pressure cap is also different in size from that of the steel ball. The oil discharge hole of the pressure cap is just tangent to the steel ball to form a line seal. The pressure cap and the main body are connected together by threads.

[0021] The injection and production string for improving the recovery rate of thermal horizontal wells also includes a fiber optic protector and a wellhead penetration sealer. The optical fiber is bundled with the outer wall of the oil pipe through the fiber optic protector and lowered into the oil layer. The optical fiber passes through the thermosensitive sealer and the multiple isolation units in the horizontal section of the horizontal well. In the vertical section of the horizontal well, the optical fiber is bundled with the outer wall of the oil pipe through the fiber optic protector, passes through the wellhead penetration sealer to the ground, and is connected to the ground signal processor on the ground.

[0022] The optical fiber is prefabricated inside the coiled tubing.

[0023] The injection and production string for improving the recovery rate of thermal horizontal wells also includes an armored optical fiber filler, which is located in the continuous oil pipe and wraps the optical fiber in the middle.

[0024] The object of the present invention can also be achieved by the following technical measures: an injection-production method for improving the recovery rate of thermal horizontal wells, the injection-production method for improving the recovery rate of thermal horizontal wells adopts an injection-production string for improving the recovery rate of thermal horizontal wells, including:

[0025] Step 1, determining the injection amount of each parameter injected into the oil well;

[0026] Step 2, injecting a combination fluid of high-dry steam, viscosity reducer, high-temperature resistant oil displacement agent, and foam into the oil reservoir through a horizontal well, and then injecting high-dry steam;

[0027] Step 3, the injected combined fluid and high-dryness steam form multiple continuous balanced high-temperature steam chambers in the injection and production string for improving the recovery rate of thermal horizontal wells, thereby achieving balanced steam injection;

[0028] Step 4, design the best oil unloading angle;

[0029] Step 5, analyzing the injection-production effect of the implemented well.

[0030] The purpose of the present invention can also be achieved by the following technical measures:

[0031] In step 1, the injection amount of each parameter is determined according to the actual situation of the oil well according to the numerical simulation results and the optimization design drawing, including the type, variety and amount of injected viscosity reducer, foam and high temperature resistant oil displacement agent.

[0032] In step 1, the downhole steam dryness needs to be calculated through numerical simulation to form the dryness limit value during steam drive. The dosage of viscosity reducer, high-temperature resistant oil displacement agent, and foam agent also needs to be optimized. The purpose of the optimization design is to construct a high-temperature steam chamber above the horizontal well, and the crude oil after viscosity reduction flows from the edge of the steam chamber to the lower part of the reservoir by gravity.

[0033] In step 2, a combination fluid of high-dry steam, viscosity reducer, high-temperature resistant oil displacement agent and foam is injected into the reservoir through a horizontal well at a pressure slightly higher than the reservoir pressure. After the injection of the above-mentioned agents and multi-fluids is completed, high-dry steam is injected.

[0034] In step 4, during the recovery process, a calculation model is established to design an optimal oil drainage angle to form the thermal recovery horizontal well injection and production process string of the present invention.

[0035] In step 4, a calculation model is established, and the relationship between the optimal oil drainage angle and the oil production rate is expressed by the following expression:

[0036]

[0037] Where: K-absolute permeability;

[0038] K ro - relative permeability;

[0039] g - acceleration due to gravity;

[0040] m-dimensionless viscosity-temperature coefficient;

[0041] θ-optimal oil leakage angle at the leading edge of the steam chamber

[0042] Q0-Oil production rate per unit well length;

[0043] ν os - Kinematic viscosity of crude oil at steam temperature.

[0044] In step 5, the injection-production string for improving the recovery rate of thermal horizontal wells of the present invention is used to monitor the injection-production profile of the entire wellbore, and the injection-production effect of the implementation well is analyzed through the injection-production data collected in real time.

[0045] The injection and production string and method for improving the recovery rate of thermal horizontal wells in the present invention solve the need for on-demand steam injection in equal dryness sections of oil layer sections, and at the same time can monitor the steam injection effect and liquid production profile, and then optimize the steam distribution position of each section, thereby improving the overall recovery rate and economic benefits of heavy oil reservoirs. The injection and production string and method for improving the recovery rate of thermal horizontal wells in the present invention can improve the development effect of thermal horizontal wells, overcome the problems of uneven utilization and steam overburden caused by heterogeneity during steam injection and production of horizontal wells, thereby improving the overall recovery rate and economic benefits of oil fields. The present invention mainly injects high-dryness steam into the reservoir through a horizontal well in a manner slightly higher than the reservoir pressure, injects a combination fluid of a viscosity reducer, a high-temperature resistant oil displacement agent, and a foam, forms a high-temperature steam chamber in the reservoir, and then forms multiple continuous balanced high-temperature steam chambers in the horizontal section through the steam equal dryness distribution technology of the present invention plus the process of segmented isolation, thereby achieving the purpose of balanced steam injection. In order to strengthen multi-point oil drainage and increase production during the recovery process, a special calculation model is used to design the optimal oil drainage angle, add oil drainage tools, and improve the recovery effect. In order to verify the reliability and implementation effect of the technology, the distributed optical fiber monitoring technology described in the present invention is used to monitor the injection and production profile of the entire wellbore, and the injection and production effect of the implementation well is analyzed through the real-time collected injection and production data. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a specific embodiment of the injection-production process method for improving the recovery rate of thermal horizontal wells of the present invention;

[0047] Figure 2 It is a schematic diagram of an injection-production process string for improving the recovery rate of thermal horizontal wells by bundling the oil pipe outside the oil pipe in a specific embodiment of the present invention;

[0048] Figure 3 It is a schematic diagram of an optimization chart for the amount of an oil-soluble viscosity reducing agent in a specific embodiment of the present invention;

[0049] Figure 4 A schematic diagram of a carbon dioxide dosage optimization curve in a specific embodiment of the present invention;

[0050] Figure 5 It is a schematic diagram of a key injection parameter optimization diagram 1 in a specific embodiment of the present invention;

[0051] Figure 6 It is a schematic diagram of a key injection parameter optimization plate 2 in a specific embodiment of the present invention;

[0052] Figure 7 It is a schematic diagram of a key injection parameter optimization plate 3 in a specific embodiment of the present invention;

[0053] Figure 8It is a structural schematic diagram of a cyclone equal dryness distributor in a specific embodiment of the present invention;

[0054] Fig. 9 It is a schematic diagram of swirl shaping in a specific embodiment of the present invention;

[0055] Fig.10 It is a schematic diagram of a spring-biased constant flow dispenser in a specific embodiment of the present invention;

[0056] Fig.11 It is a schematic diagram of a critical flow offset type constant flow dispenser in a specific embodiment of the present invention;

[0057] Fig.12 It is a schematic diagram of an oil drain in a specific embodiment of the present invention;

[0058] Fig.13 It is a schematic diagram of a coiled tubing injection-production process string for improving the recovery rate of thermal horizontal wells in a specific embodiment of the present invention;

[0059] Fig.14 This is a structural diagram of a prefabricated optical fiber in a coiled tubing in a specific embodiment of the present invention;

[0060] In the figure, 1-oil drain; 2-constant flow dispenser; 3-cyclone equal dryness distributor; 4-interlayer packer; 5-thermal packer; 6-injection-production integrated pump; 7-sucker rod; 8-oil pipe; 9-optical fiber; 10-optical fiber protector; 11-wellhead penetration sealer; 12-ground signal processor; 13-continuous oil pipe; 1-1-main body; 1-2-pressure cap; 1-3-steel ball; 1-4-spring body; 13-1 continuous oil pipe; 13-2 armored optical fiber filling material; 13-3 optical fiber. DETAILED DESCRIPTION

[0061] 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.

[0062] 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.

[0063] The structure of the injection-production pipe string for improving the recovery rate of thermal horizontal wells of the present invention mainly comprises an oil drain, a constant flow injection distributor, a cyclone equal dryness distributor, an interlayer packer, a thermal sensitive packer, an injection-production integrated pump, a sucker rod, an oil pipe, an optical fiber, an optical fiber protector, a wellhead penetration sealer and a ground signal processor.

[0064] During the injection process, balanced injection is achieved mainly through oil drainer + constant flow dispenser + cyclone equal dryness distributor + interlayer packer + oil drainer + constant flow dispenser + cyclone equal dryness distributor + interlayer packer.... (depending on the number of optimized horizontal well segments) oil drainer + constant flow dispenser + cyclone equal dryness distributor + thermal packer. During the injection process, data is collected through pre-set distributed optical fibers. The steam injection profile data downhole is transmitted to the ground data signal processor on the ground through optical fibers for data processing, and then the steam injection effect of the well is analyzed through real-time steam injection data. Among them, the role of conventional thermal recovery tools such as thermal packers, constant flow dispensers, and interlayer packers is to form multiple uniform high-temperature steam chambers in the horizontal section, while the cyclone equal dryness distributor achieves the same dryness of steam distribution in each section of the horizontal section, thereby ensuring the steam injection effect. In the process of recovery, due to the process adjustment and optimization in the early stage, multiple segmented uniform and continuous high-temperature steam chambers have been formed in the horizontal section. When the injection amount of steam reaches the design requirements, the best oil leakage angle will be formed in the steam chamber, so that multiple oil leakage points are formed in the process of recovery, reducing the oil leakage resistance and increasing the oil production. In order to test the production of each section in the production process, the optical fiber test of the production profile can be carried out through the optical fiber, and the test data of the production profile under the well is transmitted to the ground signal processor on the ground through the optical fiber for data processing, and the production of the well is analyzed and evaluated by the collected data. The evaluation result can verify the specific implementation effect of the process of the present invention, analyze and evaluate the dosage, injection position and injection effect of various agents such as the viscosity reducer (oil soluble or water soluble), high temperature oil displacement agent, foam (nitrogen, carbon dioxide or nitrogen + carbon dioxide) selected in the early stage, and can also analyze the contradiction of the reservoir according to the actual production profile, so as to provide a reliable basis for adjusting the plan of the rotation.

[0065] The technical solution described in the present invention is to first determine the type, variety and quantity of viscosity reducer, foam and high temperature resistant oil displacement agent to be injected according to the numerical simulation results and the optimization design drawing, then design the process pipe column structure, and carry out preliminary preparation work according to the results of the optimization design. After the injection of the above-mentioned agents and multi-fluids is completed, high-dry steam is injected.

[0066] like Figure 1 As shown, Figure 1 The present invention is a flow chart of the injection-production process method for improving the recovery rate of thermal horizontal wells.

[0067] Step 1: According to the actual situation of the oil well, the injection volume of each parameter is determined according to the numerical simulation results and the optimization design drawing, mainly including the type, type and quantity of injected viscosity reducer, foam and high temperature oil displacement agent. The downhole steam dryness needs to be calculated by numerical simulation software to form the dryness limit value when steam drive is formed. The dosage of various agents such as viscosity reducer (oil soluble or water soluble), high temperature oil displacement agent, foam (nitrogen, carbon dioxide or nitrogen + carbon dioxide) also needs to be optimized. The purpose of the optimization design is to construct a high temperature steam chamber above the horizontal well, and the crude oil after viscosity reduction flows from the edge of the steam chamber to the lower part of the reservoir by gravity.

[0068] Step 2: Design the process string structure, carry out preliminary preparations according to the results of the optimized design, and inject a combination of high-dry steam, viscosity reducer, high-temperature oil displacement agent, and foam into the reservoir through the horizontal well at a pressure slightly higher than the reservoir pressure. After the injection of the above-mentioned agents and multi-fluids is completed, high-dry steam is injected.

[0069] Step 3: The steam equal dryness distribution technology of the present invention plus the process of segmented isolation forms multiple continuous balanced high-temperature steam chambers in the horizontal section to achieve balanced steam injection. During the design process of the steam equal dryness distribution technology in the process string, the double-helix optimization technology is innovatively proposed. This technology fully mixes the steam and liquid through the positive collision of the inner and outer pipe steam, transforming it into a uniform bubble flow, thereby ensuring the consistency of steam dryness in each layer. The structure of the device not only ensures the full mixing of steam and liquid, but also provides a test channel for the test of the injection and production profile.

[0070] Step 4: During the recovery process, the optimal oil leakage angle is designed through the calculation model described in the present invention to form the thermal recovery horizontal well injection and production process string described in the present invention.

[0071] Step 5: In order to verify the reliability and implementation effect of the technology, the distributed optical fiber monitoring technology described in the present invention is used to monitor the injection and production profile of the entire wellbore, and the injection and production effect of the implementation well is analyzed through the injection and production data collected in real time.

[0072] The features and performance of the present invention are further described in detail below in conjunction with specific embodiments.

[0073] Embodiment 1:

[0074] In the selection of injection fluid, this embodiment combines the actual field experience, and generally the oil-soluble viscosity reducer is selected such that the viscosity reduction rate of the target block oil sample is generally at least greater than 80%, and the static oil washing rate is greater than 85%; carbon dioxide is generally liquid carbon dioxide with a purity greater than 99%; steam is generally required to have a bottom hole dryness greater than 40%, and correspondingly, the wellhead dryness is generally at least greater than 75% in the east and greater than 70% in the west.

[0075] Multi-cycle injection parameters: Oil-soluble viscosity reducers are generally injected for 1 to 3 cycles, and the amount of viscosity reducer used in the first cycle depends on the crude oil viscosity and oil layer thickness of the reservoir. The specific values ​​are as follows: Figure 5 From the second cycle onwards, the value decreases by 20% each cycle.

[0076] The amount of carbon dioxide used is related to the thickness of the oil layer. The specific value is as follows: Figure 4 As shown, with the increase of cycles, it increases by 10-20% cycle by cycle. When nitrogen is selected, it is selected according to the formation pressure. When the formation pressure is less than 5MPa, 120,000 standard cubic meters are injected; when the formation pressure is 5-6MPa, 100,000 standard cubic meters are injected; when the formation pressure is 6-8MPa, 80,000 standard cubic meters are injected; when the formation pressure is greater than 8MPa, carbon dioxide injection should be selected.

[0077] The steam injection rate is related to the well length, and the specific value is as follows: Figure 6 As shown, the initial steam injection intensity is 5 to 10 t / m, and increases with each cycle, with a cycle increase of about 5%.

[0078] Steam and gas generally increase by 10% to 20% in the first 10 cycles. The "oil-soluble viscosity reducer + carbon dioxide + steam" huff-and-puff process is generally applicable to super-heavy oil reservoirs with reservoir pressure greater than 7MPa, and single wells with multiple rounds of thermal recovery where the formation has certain energy but there is oil-heavy blockage in the near-wellbore area. The "oil-soluble / water-soluble viscosity reducer + nitrogen + steam" huff-and-puff process is generally applicable to heavy oil reservoirs with reservoir pressure less than 7MPa, and single wells with heavy oil after multiple rounds of huff-and-puff where the formation urgently needs to replenish energy. For ordinary heavy oil reservoirs with low viscosity and low water content, water-soluble viscosity reducers with a static oil washing rate of >40% can be used instead of oil-soluble viscosity reducers.

[0079] Heavy oil reservoirs with moderate to strong water sensitivity generally require a high-temperature anti-swelling process.

[0080] For blocks where HDCS is applied, it is recommended to switch to HDNS or HNS technology when the reservoir pressure drops below 7MPa; for blocks where HDNS is applied, it is recommended to switch to HNS technology after 5 to 7 rounds.

[0081] Medium-deep super-heavy oil reservoir: HDCS is used in the initial stage, and the maximum horizontal well thickness is more than 5m; variable well spacing is used according to different thicknesses, the oil layer thickness is 6-25m, and the general well spacing is 105-65m; the horizontal section length is about 150m. For injection parameter selection, please refer to Figure 3 and Figure 6 Plate shown.

[0082] The injection parameters for extra-heavy oil and ordinary heavy oil reservoirs refer to the lower limit values ​​in the plate. After multiple rounds, when the reservoir pressure drops below 7MPa, it can be switched to HDNS or HNS.

[0083] Shallow and thin layer ultra-heavy oil reservoir: HDNS is used in the initial stage. The maximum horizontal well layout thickness is generally more than 5m; the well spacing is about 100m; and the horizontal section length is about 200m.

[0084] There are two types of reservoirs where injection parameters are optimized, as shown in the following table.

[0085] Table 1 Reservoir classification (HDNS process parameter optimization)

[0086] Reservoir properties Type I oil reservoir Type II oil reservoir Average effective thickness, m 5.0 5.0 Average porosity, decimal 0.352 0.352 <![CDATA[Average permeability, ×10 -3 μm 2 > 9306 4306 Crude oil viscosity (50℃), mPa.s 6000 9000 Formation temperature, °C 28 28 Horizontal section length, m 200 200

[0087] Optimization results of a type of reservoir parameters:

[0088] The optimal value of steam injection intensity is 10.5~12m 3 / m.

[0089] The optimal nitrogen injection strength is 225Nm 3 / m.

[0090] The optimal value of viscosity reducer injection intensity is 0.15t / m.

[0091] Optimization results of the second type of reservoir parameters:

[0092] The optimal value of steam injection intensity is 10m 3 / m.

[0093] The optimal value of nitrogen strength is 150Nm 3 / m.

[0094] The optimal value of viscosity reducer is 0.1t / m.

[0095] The specific injection parameters for reservoirs with different crude oil viscosities can be found in the following table: Figure 7 Plate shown.

[0096] The multi-round injection parameters can be found in the table below.

[0097] Table 2 HDNS multi-round injection parameter adjustment principles (recommended)

[0098] cycle Steam consumption Viscosity reducer dosage Nitrogen dosage 2-5 +10％ -15％ +10％ 5-10 +5％ -10％ +12％ >10 +3％ 0 +15％

[0099] like Figure 8 As shown, the cyclone equal dryness distributor mainly optimizes the steam dryness and flow rate through the cyclone mixing device. The main structure of the device is composed of: 3-1 cyclone equal dryness distributor outer tube, 3-2 outer spiral, 3-3 inner spiral, 3-4 test channel, etc. The main feature of the device is that the outer spiral surface 3-2 turns right, the inner spiral surface 3-3 turns left, and the inner and outer spiral surfaces form a double spiral structure, such as Figure 8As shown in FIG. 1 , the internal and external spiral inclination angles of the structure have been verified through numerical simulation and indoor experiments. The optimal spiral inclination angles of the internal and external spirals are both 60°, and the inclination angle is zero at the lower end outlet.

[0100] The main principle of the device is to use the steam from the inner and outer pipes to collide positively. When the upstream flow on the pipeline is a non-uniform flow type such as stratified flow, wave flow, slug flow, uneven annular flow, etc., such as Figure 4 As shown. Under the action of the inner and outer spiral flow channels, the above flow pattern is unified and rectified into an annular flow with a liquid film evenly distributed around the pipeline, so that the gas and liquid are fully mixed, and then the gas-liquid two-phase flow entering each constant flow distributor has the same composition, ensuring the consistency of steam dryness in each layer. Another inventive point of the device is that the swirl flow channel is designed on the inner pipe wall, and the injection and production profile test channel flows out, solving the problem of not being able to test in real time during the production process.

[0101] The constant flow dispenser adopts a critical flow nozzle structure, and the designed steam flow range is 4-15t / h, the pressure range is 8-21MPa, and the dryness range is 60-85%, which belongs to typical wet steam flow. The wet steam critical flow control equation of the present invention is:

[0102]

[0103] Wherein, W is the wet steam flow rate, t / h; Y is the wet steam expansion coefficient; d is the diameter of the Venturi nozzle throat, mm; H is the length of the Venturi nozzle throat, mm; ρ is the wet steam density, kg / m3; P1 is the critical flow nozzle inlet pressure, MPa.

[0104] The constant flow dispenser mainly adopts an offset steam flow control device, and its internal structure can be a spring structure or a critical flow injection structure, which is an existing product and will not be described in detail here. Fig.10 and 11 shown.

[0105] The positional relationship between the swirl equal dryness distributor and the constant flow distributor is determined through a large number of numerical simulation calculations and indoor test data. It is finally determined that when the constant flow distributor is located 3 to 5 times the pipe diameter downstream of the swirl equal dryness distributor, its axial liquid film thickness is more uniform, the annular flow pattern is more stable, and the consistency of steam dryness can be better achieved.

[0106] In the oil production process of oil fields, most of the pumping wells use tubular pumps. Since the fixed valve of tubular pumps is one-way, the crude oil in the tubular will be sprayed on the ground when the oil pipe is lifted, which will cause crude oil loss and environmental pollution on the one hand, and increase the difficulty of operation on the other hand. In the operation of heavy oil wells, when the steam injection process is completed, there are problems such as large fluid resistance, slow release speed, and slow oil layer pressure relief during the recovery process.

[0107] In order to reduce the recovery resistance, strengthen multi-point oil drainage and increase the production, the present invention adopts a special calculation model, designs the optimal oil drainage angle, adds oil drainage tools, expands the blowout and production channels, effectively solves the problem of slow oil layer pressure relief and increases the production of oil wells.

[0108] like Fig.12 As shown, the oil drainer connects the oil pipe in the pump with the casing when the oil pipe is lifted. Since the internal liquid level of the oil pipe in the pump is high, the crude oil in the oil pipe will flow into the casing and will not be sprayed on the ground during the lifting operation, nor will it cause a series of problems such as loss of crude oil and fluid resistance during the recovery process.

[0109] The structure of the oil drainer includes 1-1—main body; 1-2—pressure cap; 1-3—steel ball; 1-4—spring body; Fig.12 As shown, the oil drainer mainly consists of a main body, a pressure cap, a steel ball, and a spring body. The two ends of the oil drainer are connected to the upper joint and the lower joint. A spring is installed at the oil drain hole on the inner wall. A steel ball is installed between the spring and the pressure cap, so that the steel ball is just stuck between the pressure cap and the spring. The size of the spring and the inner wall hole of the main body are different, so that the spring can just be stuck on the inner hole, playing the role of a spring base. The size of the oil drain hole at the pressure cap and the steel ball is also different. The inner hole of the pressure cap is just tangent to the steel ball, forming a line seal. The pressure cap and the main body are connected together by threads.

[0110] Based on the development status of the target well, the type of viscosity reducer is selected to strengthen viscosity reduction, reduce the difficulty of cavity making, inject foam or nitrogen, carbon dioxide, maintain the formation energy while reducing the heat loss of the top cap layer, so that a high-temperature steam chamber is constructed above the horizontal well, and high-temperature resistant oil displacement agent is injected to assist in the injection of viscosity-reduced crude oil from the edge of the steam chamber to the lower part of the reservoir by gravity, and then the steam equal dryness distribution technology of the present invention plus the process of segmented isolation are used to form multiple continuous balanced high-temperature steam chambers in the horizontal section. According to the requirements of the steam chamber oil leakage inclination angle, the steam injection amount is optimized to form multiple points of oil leakage during the recovery process and increase production. Finally, combined with the injection and production profile data tested in the whole process, the actual injection and liquid production conditions are analyzed to verify the actual application effect of the technology and provide reliable data support for the adjustment of the next rotation plan. Finally, the problems of poor development effect of horizontal wells in heavy oil reservoirs, serious steam channeling problems, and low reservoir pressure are solved.

[0111] Embodiment 2:

[0112] like Figure 2As shown, it is an integrated process string for balanced injection and production testing of thermal recovery horizontal wells. This implementation method is mainly an implementation method of bundling 9 optical fibers on the outer wall of 8 oil pipes. The process string is sequentially connected with 1 oil drainer, 2 constant flow dispenser, 3 cyclone equal dryness distributor, 4 interlayer packer, 1 oil drainer, 2 constant flow dispenser, 3 cyclone equal dryness distributor, 4 interlayer packer (not limited to two sections, the actual number of constant flow dispensers and interlayer packers depends on the number of sections of the horizontal section of the horizontal well), 3 cyclone equal dryness distributor, 5 thermal sensitive packer, 6 injection and production integrated pump, 7 sucker rod, 8 oil pipe, 9 optical fiber, 10 optical fiber protector, 11 wellhead crossing sealer and 12 ground signal processor. Before going down the well, the optical fiber 9 is bundled on the outer wall of the oil pipe 8 through the optical fiber protector 10 and lowered into the oil layer. In the horizontal section, the optical fiber 9 needs to pass through the tools such as the 5 thermal-sensitive packer, the 3 cyclone equal dryness distributor, the 4 interlayer packer, the 2 constant flow dispenser, and the 1 oil drainer. In the vertical well section, the optical fiber is bundled on the outer wall of the oil pipe 8 through the optical fiber protector 10, and finally passes through the sealer 11 at the wellhead to the ground, and is connected to the ground signal processor 12 on the ground to process the collected injection and production data, and finally obtain the actual situation underground.

[0113] Embodiment 3:

[0114] like Fig.13 As shown, it is an integrated process string for balanced injection and production testing of thermal recovery horizontal wells. This implementation method is mainly an implementation method in which 9 optical fibers are prefabricated inside 13 coiled tubings. The process string is sequentially connected with 1 oil drainer, 2 constant flow dispensers, 3 cyclone equal dryness distributors, 4 interlayer packers, 1 oil drainer, 2 constant flow dispensers, 3 cyclone equal dryness distributors, 4 interlayer packers (not limited to two sections, the actual number of constant flow dispensers and interlayer packers depends on the number of sections of the horizontal section of the horizontal well), 3 cyclone equal dryness distributors, 5 thermal sensitive packers, 6 injection and production integrated pumps, 7 sucker rods, 13 coiled tubings, and 12 ground signal processors. Before going down the well, 9 optical fibers are prefabricated inside 13 coiled tubings and lowered into the oil layer. In the horizontal section, the 13 coiled tubings need to be connected to 5 thermal-sensitive packers, 3 cyclone equal-dryness distributors, 4 interlayer packers, 2 constant-flow injectors, 1 oil drain and other tools. In the vertical well section, the 9 optical fibers pass through the 13 coiled tubings and finally pass through the wellhead to the ground. They are connected to the 12 ground signal processors on the ground to process the collected injection and production data and finally obtain the actual situation downhole.

[0115] like Fig.14As shown, 13-1 is a continuous oil pipe; 13-2 is an armored optical fiber filler; 13-3 is an optical fiber, wherein 13-3 is located in the middle and mainly plays the role of sensing signals. 13-2 is an armored optical fiber filler and mainly plays the role of protecting 13-3 optical fiber from disconnection and corrosion. The packaged 13-2 and 13-1 are finally prefabricated in the 13-1 continuous oil pipe and lowered into the oil well.

[0116] 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.

[0117] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. An injection and production string for improving the recovery rate of a thermal horizontal well, characterized in that: The injection-production string for improving the recovery rate of thermal horizontal wells includes multiple isolation units, a thermosensitive packer, an injection-production integrated pump, a sucker rod, an optical fiber and a ground signal processor. Each isolation unit includes an oil drain, a constant flow injector, a cyclone equal dryness distributor and an interlayer packer connected in sequence. The thermosensitive packer isolates the multiple isolation units in the horizontal section of the horizontal well. One end of the injection-production integrated pump is connected to the thermosensitive packer, and the other end is connected to the sucker rod. The optical fiber is connected to the ground signal processor and is lowered into the oil layer to transmit the collected injection-production data to the ground signal processor. The ground signal processor processes the injection-production data to obtain the actual situation downhole.

2. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, characterized in that: The number of the plurality of isolation units is equal to the number of optimized horizontal well segments.

3. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, characterized in that: The swirl flow equal dryness distributor comprises an outer tube of the swirl flow equal dryness distributor, an outer spiral and an inner spiral. The outer spiral and the inner spiral are both located in the outer tube of the swirl flow equal dryness distributor. The outer spiral surface turns right, and the inner spiral surface turns left, forming a test channel with a double spiral structure.

4. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, characterized in that: The constant flow dispenser adopts a critical flow nozzle structure, and is designed with a steam flow range of 4-15t / h, a pressure range of 8-21MPa, and a dryness range of 60-85%.

5. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 4, characterized in that: The steam flow in the constant flow dispenser belongs to the typical wet steam flow, and the critical flow control equation of wet steam is: Wherein, W is the wet steam flow rate, t / h; Y is the wet steam expansion coefficient; d is the diameter of the Venturi nozzle throat, mm; H is the length of the Venturi nozzle throat, mm; ρ is the wet steam density, kg / m3; P1 is the critical flow nozzle inlet pressure, MPa.

6. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, characterized in that: The constant flow dispenser is located at a distance of 3 to 5 times the pipe diameter of the cyclone equal dryness distributor downstream of the cyclone equal dryness distributor.

7. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, characterized in that: The oil drainer includes a main body, a pressure cap, a steel ball and a spring. The two ends of the oil drainer are connected to the upper joint and the lower joint of the oil pipe. The spring is installed at the oil drain hole on the inner wall of the main body. The steel ball is installed between the spring and the pressure cap so that the steel ball is just stuck between the pressure cap and the spring.

8. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 7, characterized in that: The size of the spring and the inner wall hole of the main body are different, so that the spring can be just stuck on the inner wall hole and play the role of a spring base. The oil drain hole at the pressure cap is also different in size from that of the steel ball. The oil discharge hole of the pressure cap is just tangent to the steel ball to form a line seal. The pressure cap and the main body are connected together by threads.

9. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, characterized in that: The injection and production string for improving the recovery rate of thermal horizontal wells also includes a fiber optic protector and a wellhead penetration sealer. The optical fiber is bundled with the outer wall of the oil pipe through the fiber optic protector and lowered into the oil layer. The optical fiber passes through the thermosensitive sealer and the multiple isolation units in the horizontal section of the horizontal well. In the vertical section of the horizontal well, the optical fiber is bundled with the outer wall of the oil pipe through the fiber optic protector, passes through the wellhead penetration sealer to the ground, and is connected to the ground signal processor on the ground.

10. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, characterized in that: The optical fiber is prefabricated inside the coiled tubing.

11. The injection-production string for improving the recovery rate of thermal horizontal wells according to claim 10, characterized in that: The injection and production string for improving the recovery rate of thermal horizontal wells also includes an armored optical fiber filler, which is located in the continuous oil pipe and wraps the optical fiber in the middle.

12. An injection-production method for improving the recovery rate of a thermal horizontal well, characterized in that: The injection-production method for improving the recovery rate of thermal horizontal wells adopts the injection-production string for improving the recovery rate of thermal horizontal wells according to claim 1, comprising: Step 1, determining the injection amount of each parameter injected into the oil well; Step 2, injecting a combination fluid of high-dry steam, viscosity reducer, high-temperature resistant oil displacement agent, and foam into the oil reservoir through a horizontal well, and then injecting high-dry steam; Step 3, the injected combined fluid and high-dryness steam form multiple continuous balanced high-temperature steam chambers in the injection and production string for improving the recovery rate of thermal horizontal wells, thereby achieving balanced steam injection; Step 4, design the best oil unloading angle; Step 5, analyzing the injection-production effect of the implemented well.

13. The method for improving the recovery rate of thermal horizontal wells according to claim 12, characterized in that: In step 1, the injection amount of each parameter is determined according to the actual situation of the oil well according to the numerical simulation results and the optimization design drawing, including the type, variety and amount of injected viscosity reducer, foam and high temperature resistant oil displacement agent.

14. The method for improving the recovery rate of thermal horizontal wells according to claim 13, characterized in that: In step 1, the downhole steam dryness needs to be calculated through numerical simulation to form the dryness limit value during steam drive. The dosage of viscosity reducer, high-temperature resistant oil displacement agent, and foam agent also needs to be optimized. The purpose of the optimization design is to construct a high-temperature steam chamber above the horizontal well, and the crude oil after viscosity reduction flows from the edge of the steam chamber to the lower part of the reservoir by gravity.

15. The method for improving the recovery rate of thermal horizontal wells according to claim 12, characterized in that: In step 2, a combination fluid of high-dry steam, viscosity reducer, high-temperature resistant oil displacement agent and foam is injected into the reservoir through a horizontal well at a pressure slightly higher than the reservoir pressure. After the injection of the above-mentioned agents and multi-fluids is completed, high-dry steam is injected.

16. The method for improving the recovery rate of thermal horizontal wells according to claim 12, characterized in that: In step 4, during the recovery process, a calculation model is established to design an optimal oil drainage angle to form the thermal recovery horizontal well injection and production process string of the present invention.

17. The method for improving the recovery rate of thermal horizontal wells according to claim 16, characterized in that: In step 4, a calculation model is established, and the relationship between the optimal oil drainage angle and the oil production rate is expressed by the following expression: Where: K-absolute permeability; K ro - relative permeability; g - acceleration due to gravity; m-dimensionless viscosity-temperature coefficient; θ-optimal oil leakage angle at the leading edge of the steam chamber Q0-Oil production rate per unit well length; ν os - Kinematic viscosity of crude oil at steam temperature.

18. The method for improving the recovery rate of thermal horizontal wells according to claim 12, characterized in that: In step 5, the injection-production string for improving the recovery rate of thermal horizontal wells of the present invention is used to monitor the injection-production profile of the entire wellbore, and the injection-production effect of the implementation well is analyzed through the injection-production data collected in real time.

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