A method and a steam injection string for staged and segmented balanced steam injection in thermal recovery horizontal wells

Abstract

The application discloses a kind of thermal recovery horizontal well step-by-step segmented balanced steam injection method and steam injection pipe column, it is related to oilfield development technical field, method includes the following steps: S 1, by distributed temperature and pressure profile test technology determines horizontal well section producing condition, determines initiative section, secondary producing section and producing difference well section;According to well section producing condition, remaining oil saturation determines well section type, well section type includes type I well section, type II well section, type III well section, according to well section type determines steam injection volume;S2, the blocking device of the injection distributor in type I well section, type II well section, type III well section decomposes temperature in turn increases.The application defines the steam distribution of different well sections, provides basis for the optimization selection of injection distributor position, plugging device material.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a method for staged equal steam injection in thermal recovery horizontal wells and a steam injection tubing string. Background Technology

[0002] Heavy oil reservoirs are characterized by high crude oil viscosity and significant differences in oil-water mobility ratios. Steam injection is primarily conducted through horizontal wells. After multiple rounds of injection, uneven utilization of horizontal well sections is caused by indiscriminate steam injection and reservoir heterogeneity. The average maximum temperature difference reaches 77°C, resulting in repeated steam scouring of high-permeability sections, leading to high recovery rates of remaining oil. Conversely, low-permeability sections remain largely unutilized, hindering oil recovery and causing a continuous decline in cyclical production capacity and reduced efficiency in thermal recovery development. In recent years, methods such as adjusting the position of the injector and using a combination of injectors and steam umbrellas for segmented steam injection have been explored to adjust the steam absorption profile of horizontal well sections. However, both methods fail to effectively adjust the steam absorption profile and achieve balanced utilization of the horizontal sections when reservoir heterogeneity is high and the injection pressure for different well sections cannot be determined in advance.

[0003] Publication No. CN118148595A discloses a method to improve the thermal utilization rate of heavy oil horizontal well reservoirs. For heavy oil thermal recovery wells with a permeability difference ≤1.5 and a steam injection pressure difference ≤1MPa within the horizontal well section, conventional steam injection tubing is configured; for heavy oil thermal recovery wells with a permeability difference >1.5 or a steam injection pressure difference >1MPa within the horizontal well section, segmented steam injection tubing is configured; the number, location, and flow rate of steam injection screens are optimized and adjusted according to reservoir characteristics, temperature and pressure profile test results, remaining oil saturation in the well section, changes in reservoir properties, and historical production data; and nitrogen foam profile control is used for some thermal recovery cycles.

[0004] Announcement No. CN111460647B discloses a quantitative allocation method for segmented targeted steam injection in horizontal wells after multiple rounds of huff and puff. The method includes: conducting well temperature and residual oil saturation tests on the horizontal well; plotting the well temperature curve and residual oil saturation curve on the same abscissa; experimentally determining the critical temperature at which heavy oil non-Newtonian fluids convert to Newtonian fluids; dividing the well temperature curve into high-temperature and low-temperature zones; identifying high and low residual oil saturation zones on the residual oil saturation curve and dividing it into several segmented curves; obtaining a fitting function; performing area integration on the polygon formed by the segmented curves and the abscissa to obtain the polygon area; calculating the area ratio of each polygon; and determining the segmented steam injection volume in the horizontal well to achieve quantitative allocation of the segmented steam injection volume.

[0005] Announcement No. CN115247543B discloses a method for targeted segmented water shut-off and staggered precision steam injection in horizontal wells of heavy oil reservoirs, including: Step 1, conducting water testing to determine the distribution of remaining oil; Step 2, optimizing the matching targeted segmented water shut-off tubing for horizontal well sections with lower remaining oil saturation based on different remaining oil saturation levels to achieve targeted water shut-off in high water-cut sections; Step 3, after injecting water shut-off agent for targeted segmented water shut-off, slowly withdrawing the water shut-off tubing; Step 4, optimizing the matching staggered precision steam injection tubing for horizontal well sections with higher remaining oil saturation based on different remaining oil saturation levels to achieve balanced utilization of remaining oil; Step 5, switching to pumping and opening the well after steam injection.

[0006] None of the aforementioned existing technologies offer a technical solution for selecting the type of injector plugging device based on the well section type, and their precision steam injection effect is weaker than that of this patent.

[0007] In summary, the technical solutions, technical problems to be solved, and beneficial effects of the above-disclosed technologies are all different from those of the present invention. Regarding the more technical features, technical problems to be solved, and beneficial effects of the present invention, the above-disclosed technical documents do not provide any technical inspiration. Summary of the Invention

[0008] To address the aforementioned deficiencies in existing technologies, the purpose of this invention is to provide a step-by-step, segmented, balanced steam injection method and steam injection tubing for thermal recovery horizontal wells.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] On the one hand, the present invention provides a method for staged equalization steam injection in a thermal recovery horizontal well, comprising the following steps:

[0011] S1. Determine the operational status of horizontal well sections using distributed temperature and pressure profile testing technology, and identify active, secondary, and poorly operational well sections.

[0012] The well section type is determined based on the well section utilization status and remaining oil saturation. Well section types include Class I, Class II, and Class III well sections. The steam injection volume is determined based on the well section type.

[0013] Furthermore, in S1, well sections with a remaining oil saturation of ≥50% that are either secondary or poorly activated are classified as Class I well sections;

[0014] Well sections with a residual oil saturation of 30% < 50% and poor utilization rate are classified as Class II well sections.

[0015] Well sections with a residual oil saturation of 20% to 30% that are either under-operation or poorly operated are classified as Class III well sections.

[0016] Steam demand for Class I well sections: Steam demand for Class II well sections: Steam demand for Class III well sections = 4-6:2-4:1-3.

[0017] Furthermore, if one of the Class I, Class II, and Class III well sections is missing, the steam distribution in the other class sections will be increased proportionally.

[0018] Furthermore, in S1, at least three time-segmented temperature curves are used to accurately identify the active use segment, the secondary use segment, and the differential use segment.

[0019] The decomposition temperature of the plugging device in the injection equipment increases sequentially in the S2, Class I, Class II, and Class III well sections.

[0020] Furthermore, in S2, a first injector is installed in Class I well sections, a second injector in Class II well sections, and a third injector in Class III well sections; thermal recovery packers are used to isolate the various well sections.

[0021] The first steam injection port of the first injector is blocked by the first plug; the second steam injection port of the second injector is blocked by the second plug; the third steam injection port of the third injector is blocked by the third plug.

[0022] The first blocker decomposes at 150-170℃;

[0023] The decomposition temperature of the second plug is 250-270℃;

[0024] The decomposition temperature of the third blocker is 300-320℃.

[0025] Preferably, in S2, the first plug is made of PVC.

[0026] The second plug is made of ABS or PMMA material;

[0027] The third plug is made of PE material.

[0028] Furthermore, in S2, the setting position of the thermal recovery packer avoids the position of the casing coupling. All the thermal recovery packers above the uppermost thermal recovery packer are equipped with heat insulation oil pipes. If there are no heat insulation oil pipes or the heat insulation oil pipes fail, the annulus above the thermal recovery packer is filled with nitrogen.

[0029] If two steam injection well sections of the same type are adjacent, then the two adjacent thermal recovery packers are merged, and a first-stage thermal recovery packer is installed.

[0030] Furthermore, in S2, after the injector is opened in the Class II and Class III well sections, profile control measures are implemented simultaneously. After the profile control system is injected, more than 5,000 standard cubic meters of nitrogen gas are replaced in the nitrogen slug.

[0031] S3. After the well is simmered and the flow is released, switch to pumping to open the well.

[0032] Secondly, the present invention provides a staged equalization steam injection string for a thermal recovery horizontal well, wherein the steam injection string is designed according to step S2 of the staged equalization steam injection method for a thermal recovery horizontal well.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. This invention can guide the setting of the injection device position, and at the same time, combined with the saturation test results, clarify the steam distribution requirements of each well section, strengthen the advantageous steam injection of the secondary activation section, the poor activation section and the remaining oil-rich well section, and improve the activation status of the horizontal well section.

[0035] 2. By comprehensively employing distributed temperature and pressure profile testing and saturation testing technologies, the steam distribution volume of different well sections was determined, providing a basis for the optimized selection of injector location and plug material.

[0036] 3. The structure of the injector has been improved, and plugs of different materials have been added to realize the function of opening in stages according to temperature, which enhances the advantage of steam injection in the secondary activation section and the poor activation section where the remaining oil is rich.

[0037] 4. By adopting a step-by-step opening injector and nitrogen foam profile control system, balanced utilization of horizontal well sections with large permeability differences is achieved, improving the thermal recovery effect of horizontal wells after multiple rounds of injection and injection. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the steam injection method in this invention;

[0039] Figure 2 This is a schematic diagram of the steam injection pipe column in this invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Please see Figures 1 to 2 This invention provides a step-by-step, segmented, balanced steam injection method for thermal recovery horizontal wells, comprising the following steps:

[0042] S1. By using distributed temperature and pressure profile testing technology, the utilization status of horizontal well sections is clarified. Using at least three temperature and pressure curves at different time periods, the active utilization section, secondary utilization section, and poor utilization section are identified. At the same time, combined with the saturation test results, the steam distribution requirements of each well section are clarified. The advantages of steam injection for secondary utilization section, poor utilization section, and remaining oil-rich section are strengthened to improve the utilization status of horizontal well sections.

[0043] Specifically, the active well section refers to the section with the lowest temperature on the first curve, and the temperature of the remaining curves gradually increases, indicating that the well section has significant activity; the secondary and poorly active well sections refer to the section with the highest temperature on the first curve, and the temperature of the remaining curves gradually decreases, indicating that the well section has poor activity.

[0044] Specifically, well sections with a remaining oil saturation of ≤30% are classified as high water-flooded well sections, and well sections with a remaining oil saturation of >30% are classified as medium water-flooded well sections.

[0045] Sub-operation and poorly operated well sections with a remaining oil saturation of ≥50% are classified as Class I well sections, and their steam distribution demand accounts for 40%-60% of the total steam injection volume.

[0046] Wells with a residual oil saturation of 30% < 50% and poor utilization rate are classified as Class II well sections, and their steam distribution demand accounts for 20%-40% of the steam injection volume.

[0047] For well sections with a residual oil saturation of 20% to 30% that are used for secondary or poor-performing operations, the steam distribution requirement accounts for 10% to 30% of the steam injection volume.

[0048] If the test results show that a certain type of well section is missing, the steam distribution of other types of well sections will be increased proportionally.

[0049] S2. Run the thermal recovery horizontal well into stages and segments of equal steam injection tubing to achieve balanced utilization of the horizontal well section;

[0050] Type I well section: The first injector is installed in the middle of the well section. The first steam injection hole of the first injector is blocked by the first plug. The first plug can be rapidly decomposed when the steam injection temperature reaches 150-170℃, so that the injector in the Type I well section can be opened for steam injection.

[0051] Type II well section: A second injector is installed in the middle of the well section. The second steam injection hole of the second injector is sealed by a second plug. The second plug begins to decompose when the steam injection temperature reaches 250-270℃, thus enabling the injection of steam into the Type II well section. After the injector is opened, profile control measures such as nitrogen foam are implemented to redirect the steam flow field. After the profile control system is completed, it replaces more than 5,000 standard cubic meters of nitrogen slug.

[0052] Class III well section: The third injector is installed in the middle of the well section. The third steam injection hole of the third injector is sealed by the third plug. The third plug begins to decompose when the steam injection temperature reaches 300-320℃, realizing the opening of the injector for Class III well section. After the third injector is opened, profile control measures such as nitrogen foam are implemented to achieve the reversal of the steam flow field. After the profile control system is completed, it replaces more than 5,000 standard cubic meters of nitrogen slug.

[0053] Thermal recovery packers are used to isolate different well sections. The setting position of the thermal recovery packers must avoid the casing coupling position. All thermal recovery packers above the uppermost thermal recovery packer are equipped with insulated tubing. If there is no insulated tubing or the insulated tubing fails the test, the annulus above the thermal recovery packer must be filled with nitrogen.

[0054] If two steam injection well sections of the same type are adjacent, the two adjacent thermal recovery packers are merged, and only one thermal recovery packer needs to be installed.

[0055] S3, switch to pumping and open the well.

[0056] This invention, through temperature and pressure profile and saturation testing, identifies the secondary, poorly functioning, and remaining oil-rich well sections. It then modifies the injectors requiring different steam injection volumes, matching different temperature-resistant plugs to the injector volume. As the steam injection volume decreases, the temperature resistance of the plugs gradually increases, allowing the injector to open step-by-step as the steam injection temperature rises. Simultaneously, a foam profile control system is injected. Compared to current segmented steam injection technology, this invention effectively adjusts the steam flow field with only simple modifications to the injector, and is safe and easy to implement. It is suitable for horizontal wells with shallow build-up points and large inclinations.

[0057] Example 1:

[0058] This embodiment provides an application example of a step-by-step, segmented, balanced steam injection method for thermal recovery horizontal wells.

[0059] It was applied to an oil well, C20-P61. It was put into production in the Ng layer, initially producing 30.6 tons of fluid and 4.5 tons of oil per day, with a water cut of 85.2%. After 17 cycles, it currently produces 11.4 tons of fluid and 1.1 tons of oil per day, with a water cut of 89.9%.

[0060] Well C20-P61 is located in the eastern part of Unit 20. The well controls reserves of 105,000 tons, with accumulated fluid reserves of 112,000 tons and accumulated oil reserves of 14,000 tons, representing a recovery rate of 13.3%. Due to differences in reservoir permeability and the influence of general steam injection, the cycle production has gradually decreased to around 400 tons after multiple rounds of injection and drainage. The oil-steam ratio has dropped from 4.69 at the start of production to the current 1.79. Therefore, a staged, balanced steam injection method is adopted to address the problem of uneven utilization in the horizontal well section.

[0061] S1. By using distributed temperature and pressure profile testing technology and temperature curves from three or more different time periods, the operational status of the horizontal well section is clarified. After multiple rounds of injection and output, the temperature field of the entire horizontal section shows a negative anomaly change, and the operational status of the middle section is significantly better than that of the two ends. The design steam distribution for the 18th cycle is 2,500 tons.

[0062] The temperature rise in the middle section of the horizontal section (1065-1260m) is relatively large, the formation activity is relatively obvious, and the remaining oil saturation is 26.6%, which belongs to Class III well section;

[0063] The temperature rise in the first section of the horizontal section (1026-1064m) is relatively small, which is the secondary operating section. The remaining oil saturation is 37.2%, which belongs to the Class II well section.

[0064] The temperature rise in the latter part of the horizontal section (1261-1298m) remained unchanged, indicating a poor mobilization zone. The remaining oil saturation was 52.1%, classifying it as a Class I well section.

[0065] According to the method provided by the present invention, the ratio of Class I well section: Class II well section: Class III well section is 4-6:2-4:1-3, and 6:3:2 is selected as the steam distribution ratio for this cycle;

[0066] Therefore, the steam distribution demand for Class I well sections accounts for 60% of the steam injection volume, and the steam distribution volume for this cycle is 1,500 tons;

[0067] Steam demand in Class II well sections accounts for 30% of the total steam injection volume, with a steam distribution volume of 750 tons for this cycle.

[0068] Steam distribution demand for Class III well sections accounts for 10% of the total steam injection volume, with a steam distribution volume of 250 tons for this cycle.

[0069] S2. Run the thermal recovery horizontal well into stages and segments of the steam injection tubing to achieve balanced utilization of the horizontal well section.

[0070] Step-by-step balanced steam injection tubing: The middle section of the horizontal segment, 1065-1260m, is a Class III well section. The third injector installed in this tubing has a specification of φ8mm~φ10mm×10 holes / m×2m. The plugger is designed with PE material. After the injection is started, nitrogen foam profile control is continuously implemented. After the profile control system is completed, it replaces the nitrogen plug.

[0071] The first section of the horizontal segment, from 1026 to 1064m, is a Class II well section. The second injector installed in this tubing string has a specification of φ8mm~φ10mm×10 holes / m×2m. The plug is designed to be made of ABS or PMMA material. After the injection is started, nitrogen foam profile control is continuously implemented. After the profile control system is completed, it replaces the nitrogen plug.

[0072] The latter section of the horizontal section, from 1261 to 1298m, is a Class I well section. The first injector installed in this test was φ8mm~φ10mm×20 holes / m×2m. The plug was made of PVC material. After the injector was opened, the steam injection temperature was maintained at no more than 200℃ for continuous steam injection.

[0073] Steam injection process: The steam injection temperature is maintained at 200℃. First, 1500 tons of steam are injected into the latter section of the horizontal section, 1261-1298m.

[0074] After accumulating 1500 tons of steam injection, the steam injection temperature is increased to 270℃, and the second distributor at 1026-1064m in the front section of the horizontal section is opened to inject 750 tons of steam. Nitrogen and foaming agent are injected simultaneously with the steam injection. The nitrogen discharge rate is 600 standard cubic meters / hour, and the foaming agent discharge rate is 0.1 cubic meters / hour. The injection continues for 50 hours.

[0075] After a cumulative steam injection volume of 2250 tons, the steam injection temperature is increased to 320℃, and the third injector in the middle section of the horizontal section (1065-1260m) is opened to inject 250 tons of steam. Simultaneously, nitrogen and foaming agent are injected, with a nitrogen discharge rate of 600 standard cubic meters per hour and a foaming agent discharge rate of 0.1 cubic meters per hour. This process is repeated for 20 hours.

[0076] Compared to the previous cycle, with the steam injection rate remaining basically the same, the steam injection pressure increased from 9.6 MPa to 11.4 MPa, effectively utilizing the remaining oil.

[0077] S3. After the well is simmered and the flow is released, switch to pumping to open the well.

[0078] Production effect evaluation: The drainage period after well opening of C20-P61 was shortened by 12 days compared with the previous cycle. The oil production during the cycle was 734 tons, an increase of 240 tons year-on-year. This shows that the construction optimization scheme of the thermal recovery horizontal well step-by-step balanced steam injection method of the present invention can reflect the effect of adjusting the steam intake profile of the matching steam injection tubing and achieving balanced utilization.

[0079] The method for staged equal steam injection in thermal recovery horizontal wells provided by this invention is simple and safe to construct by adjusting the steam flow field of the horizontal well, and achieves balanced utilization of the horizontal well section, thereby improving the cycle development effect and benefits of thermal recovery horizontal wells after multiple rounds of injection and output.

[0080] Example 2:

[0081] This embodiment provides an application example of a step-by-step, segmented, balanced steam injection method for thermal recovery horizontal wells.

[0082] It was applied to an oil well, C20-P87. It was put into production in the Ng layer, initially producing 30.3 tons of fluid and 18.8 tons of oil per day, with a water cut of 37.7%. After 20 cycle runs, it currently produces 8.1 tons of fluid and 0.8 tons of oil per day, with a water cut of 90.1%.

[0083] Well C20-P87 is located in the western part of Unit 33. The well controls reserves of 122,000 tons, with accumulated fluid reserves of 99,000 tons and accumulated oil reserves of 16,000 tons, representing a recovery rate of 13.1%. After multiple rounds of injection and drainage, the cycle production gradually decreased to around 410 tons. Therefore, a step-by-step, segmented, balanced steam injection method was chosen to address the uneven utilization of the horizontal well section.

[0084] S1. By using distributed temperature and pressure profile testing technology and temperature curves from three or more different time periods, the operational status of the horizontal well section is clarified. The results of distributed temperature and pressure profile and saturation testing show that after multiple rounds of injection and discharge, the temperature field of the entire horizontal section shows a negative anomaly. The operational status of the front section is significantly better than that of the middle and rear sections. The design steam distribution for the 21st cycle is 2800 tons.

[0085] The temperature rise in the first section of the horizontal segment (1012-1055m) is relatively large, the formation activity is relatively obvious, and the remaining oil saturation is 28.5%, which belongs to Class III well segment.

[0086] The temperature rise in the middle section of the horizontal section (1056-1072m) is relatively small, which is the secondary operating section. The remaining oil saturation is 45.7%, which belongs to the Class II well section.

[0087] The temperature rise in the latter part of the horizontal section (1073-1154m) remained unchanged, indicating a poor mobilization zone. The remaining oil saturation was 57.4%, classifying it as a Class I well section.

[0088] This period's design requires steam distribution for Class I well sections, which accounts for 40% of the total steam injection volume. The total steam distribution volume for this period is 1120 tons.

[0089] The steam distribution demand for Class II well sections accounts for 20% of the steam injection volume, with a steam distribution volume of 560 tons in this cycle;

[0090] Steam demand in Class III well sections accounts for 40% of the total steam injection volume, with a steam distribution volume of 1,120 tons in this cycle.

[0091] S2. Run the thermal recovery horizontal well into stages and segments of the steam injection tubing to achieve balanced utilization of the horizontal well section.

[0092] Step-by-step balanced steam injection tubing: The first section of the horizontal segment, 1012-1055m, is a Class III well section. The third injector installed in this tubing has a specification of φ8mm~φ10mm×10 holes / m×2m. The plugger is designed with PE material. After the injection is started, nitrogen foam profile control is continuously implemented. After the profile control system is completed, it replaces the nitrogen plug.

[0093] The middle section of the horizontal segment, from 1056 to 1072m, is a Class II well section. The second injector installed in this tubing string has a specification of φ8mm~φ10mm×10 holes / m×2m. The plugger is designed to be made of ABS or PMMA material. After the injection is started, nitrogen foam profile control is continuously implemented. After the profile control system is completed, it replaces the nitrogen plug.

[0094] The latter section of the horizontal section, from 1073 to 1154m, is a Class I well section. The first injector installed in this test was φ8mm~φ10mm×20 holes / m×2m. The plug was made of PVC material. After the injector was opened, the steam injection temperature was maintained at no more than 200℃ for continuous steam injection.

[0095] Steam injection process: The steam injection temperature is maintained at 200℃. First, 1120 tons of steam are injected into the latter section of the horizontal section, 1056-1072m.

[0096] After a cumulative steam injection volume of 1120 tons, the steam injection temperature is increased to 270℃, and the second injector in the middle section of the horizontal section (1056-1072m) is opened to inject 560 tons of steam. Nitrogen and foaming agent are injected simultaneously with the steam injection. The nitrogen discharge rate is 600 standard cubic meters per hour, and the foaming agent discharge rate is 0.1 cubic meters per hour. The injection continues for 30 hours.

[0097] After a cumulative steam injection volume of 1680 tons, the steam injection temperature is increased to 320℃, and the third injector in the first section of the horizontal section (1012-1055m) is opened, injecting 1120 tons of steam. Simultaneously, nitrogen and foaming agent are injected, with a nitrogen discharge rate of 600 standard cubic meters per hour and a foaming agent discharge rate of 0.1 cubic meters per hour, continuously for 70 hours.

[0098] Compared to the previous cycle, with the steam injection rate remaining basically the same, the steam injection pressure increased from 9.0 MPa to 9.6 MPa, but the pressure increase was not significant.

[0099] S3. After the well is simmered and the flow is released, switch to pumping to open the well.

[0100] Production performance evaluation: The drainage period after well C20-P87 was opened was shortened by 2 days compared with the previous cycle. The oil production during the cycle was 486 tons, an increase of only 70 tons year-on-year. This indicates that the increased demand for steam distribution in Class III well sections failed to significantly improve the effective utilization of the remaining oil.

[0101] Example 3:

[0102] This invention provides an application example of a step-by-step, segmented, balanced steam injection method for thermal recovery horizontal wells.

[0103] It was applied to an oil well, C20-P99. It was put into production in the Ng layer, initially producing 23.3 tons of fluid and 10.0 tons of oil per day, with a water cut of 57.0%. After 19 cycles, it currently produces 5.5 tons of fluid and 1.1 tons of oil per day, with a water cut of 78.4%.

[0104] Well C20-P99 is located in the middle of Unit 33, with a single well controlling reserves of 126,000 tons, accumulating 78,000 tons of fluid and 17,000 tons of oil, and a recovery rate of 13.5%. After multiple rounds of injection and purging, the cycle production gradually decreased to about 350 tons. Therefore, the method of step-by-step balanced steam injection was adopted to address the problem of uneven utilization in the horizontal well section.

[0105] S1. By using distributed temperature and pressure profile testing technology and temperature curves from three or more different time periods, the operational status of the horizontal well section is clarified. The results of distributed temperature and pressure profile and saturation testing show that after multiple rounds of injection and discharge, the temperature field of the entire horizontal section shows a negative anomaly. The operational status of the front section is significantly better than that of the middle and rear sections. The design steam distribution for the 20th cycle is 2,500 tons.

[0106] The temperature rise in the first section of the horizontal segment (1044-1079m) is relatively large, the formation activity is relatively obvious, and the remaining oil saturation is 24.2%, which belongs to Class III well segment;

[0107] The temperature rise in the middle section of the horizontal section (1080-1152m) is relatively small, which is the secondary operating section. The remaining oil saturation is 47.9%, which belongs to the Class II well section.

[0108] The temperature rise in the latter part of the horizontal section (1153-1172m) remained unchanged, indicating a poor mobilization zone. The remaining oil saturation was 55.1%, classifying it as a Class I well section.

[0109] This period's design requires steam distribution for Class I well sections, which accounts for 60% of the steam injection volume. The steam distribution volume for this period is 1,500 tons.

[0110] The steam distribution demand for Class II well sections accounts for 20% of the steam injection volume, with a steam distribution volume of 500 tons in this cycle;

[0111] The steam distribution demand for Class III well sections accounts for 20% of the steam injection volume, with a steam distribution volume of 500 tons in this cycle.

[0112] S2. Run the thermal recovery horizontal well into stages and segments of the steam injection tubing to achieve balanced utilization of the horizontal well section.

[0113] Step-by-step balanced steam injection tubing: The first section of the horizontal segment, 1044-1079m, is a Class III well section. The third injector installed in this tubing has a specification of φ8mm~φ10mm×10 holes / m×2m. The plugger is designed with PE material. After the injection is started, nitrogen foam profile control is continuously implemented. After the profile control system is completed, it replaces the nitrogen plug.

[0114] The middle section of the horizontal segment, from 1080 to 1152m, is a Class II well section. The second injector installed in this tubing string has a specification of φ8mm~φ10mm×10 holes / m×2m. The plug is designed to be made of ABS or PMMA material. After the injection is started, nitrogen foam profile control is continuously implemented. After the profile control system is completed, it replaces the nitrogen plug.

[0115] The latter section of the horizontal section, from 1153 to 1172m, is a Class I well section. The first injector installed in this test was φ8mm~φ10mm×20 holes / m×2m. The plug was made of PVC material. After the injector was opened, the steam injection temperature was maintained at no more than 200℃ for continuous steam injection.

[0116] Steam injection process: The steam injection temperature is maintained at 200℃. First, 1500 tons of steam are injected into the latter section of the horizontal section, from 1153 to 1172m.

[0117] After accumulating 1500 tons of steam injection, the steam injection temperature is increased to 270℃, and the second injector in the middle section of the horizontal section (1080-1152m) is opened to inject 500 tons of steam. Simultaneously, nitrogen and foaming agent are injected, with a nitrogen discharge rate of 600 standard cubic meters per hour and a foaming agent discharge rate of 0.1 cubic meters per hour. The injection continues for 30 hours.

[0118] After accumulating 2000 tons of steam injection, the steam injection temperature is increased to 320℃, and the third injector in the first section of the horizontal section (1044-1079m) is opened to inject 500 tons of steam. Simultaneously, nitrogen and foaming agent are injected, with a nitrogen discharge rate of 600 standard cubic meters per hour and a foaming agent discharge rate of 0.1 cubic meters per hour. This process is continued for 30 hours.

[0119] Compared to the previous cycle, with the steam injection rate remaining basically the same, the steam injection pressure increased from 9.7 MPa to 10.2 MPa, showing a partial increase in pressure.

[0120] S3. After the well is simmered and the flow is released, switch to pumping to open the well.

[0121] Production performance evaluation: The drainage period after well C20-P99 was opened was shortened by 5 days compared with the previous cycle. The oil production during the cycle was 490 tons, an increase of 140 tons year-on-year. This indicates that the utilization of the remaining oil was improved after only increasing the steam distribution demand of Class I well sections, but there is still potential for further improvement.

[0122] Comparative Example 1:

[0123] An oil well, C20-P61, was put into production in the Ng layer. Initially, it produced 30.6 tons of fluid and 4.5 tons of oil per day, with a water cut of 85.2%. After 15 cycles, it currently produces 12.5 tons of fluid and 1.5 tons of oil per day, with a water cut of 87.5%.

[0124] Well C20-P61 is located in the eastern part of Unit 20. The single well controls reserves of 105,000 tons, with accumulated fluid of 89,000 tons and accumulated oil of 11,000 tons, resulting in a recovery rate of 10.5%. Due to differences in reservoir permeability and the influence of general steam injection, the cycle production gradually decreased to about 450 tons after multiple rounds of injection and purging. Therefore, the design of the variable-point uniform steam injection tubing string was optimized.

[0125] D1. By using distributed temperature and pressure profile testing technology and temperature curves from three or more different time periods, the operational status of the horizontal well section is clarified. The results of distributed temperature and pressure profile and saturation testing show that after multiple rounds of injection and discharge, the temperature field of the entire horizontal section shows a negative anomaly change, and the operational status of the middle section is significantly better than that of the two ends. The design steam distribution for this cycle is 2,500 tons.

[0126] The temperature rise in the middle section of the horizontal segment (1054-1241m) is relatively large, the formation activity is relatively obvious, and the remaining oil saturation is 29.7%.

[0127] The temperature rise in the first section of the horizontal section (1026-1053m) is relatively small, making it a secondary operating section with a remaining oil saturation of 45.1%.

[0128] The temperature rise in the latter part of the horizontal section (1242-1298m) remained unchanged, indicating a poor operating range, with a remaining oil saturation of 56.9%.

[0129] D2. Run the variable-point uniform steam injection tubing string into the thermal recovery horizontal well.

[0130] Matching components for the variable-point uniform steam injection tubing string: an injection device lowered into the rear section of the horizontal section, with specifications of φ8mm~φ10mm×30 holes / m×2m;

[0131] The filling device inserted at the front of the horizontal section has a specification of φ8mm~φ10mm×20 holes / m×2m;

[0132] The filling device is inserted in the middle of the horizontal section, with specifications of φ8mm~φ10mm×10 holes / m×2m.

[0133] The design utilizes injectors with different orifice densities to achieve steam throttling in different well sections, control the steam intake differences in different well sections, and improve the operational status of horizontal well sections.

[0134] Compared to the previous cycle, with the steam injection rate remaining basically the same, the steam injection pressure decreased from 10.5 MPa to 10.1 MPa.

[0135] D3. After the well is simmered and the flow is released, switch to pumping to open the well.

[0136] Production performance evaluation: The drainage period after well C20-P61 was opened was 5 days longer than the previous cycle. The oil production during the cycle was 410 tons, a decrease of 80 tons year-on-year. This indicates that the variable point uniform steam injection method failed to improve the utilization of the horizontal well section. Due to the influence of heterogeneity, the steam absorption difference in the horizontal well section is still large.

[0137] All components not discussed in detail in this application, as well as the connection methods of these components, are well-known technologies in this field. They can be directly applied and will not be elaborated further.

[0138] In this invention, the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0139] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0140] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0141] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for staged, segmented, and balanced steam injection in a thermal recovery horizontal well, characterized in that, Includes the following steps: S1. Determine the operational status of horizontal well sections using distributed temperature and pressure profile testing technology, and identify active, secondary, and poorly operational well sections. Well section type is determined based on well section utilization status and remaining oil saturation. Well section types include Class I, Class II, and Class III well sections. Steam distribution requirements are determined based on well section type. The decomposition temperature of the plugging device in the injection equipment increases sequentially in the S2, Class I, Class II, and Class III well sections.

2. The method for staged equal steam injection in a thermal recovery horizontal well according to claim 1, characterized in that, In S2, the first injector is installed in the Class I well section, the second injector is installed in the Class II well section, and the third injector is installed in the Class III well section; thermal recovery packers are used to isolate the various well sections. The first steam injection port of the first injector is blocked by the first plug; the second steam injection port of the second injector is blocked by the second plug; the third steam injection port of the third injector is blocked by the third plug. The first blocker decomposes at 150-170℃; The decomposition temperature of the second plug is 250-270℃; The decomposition temperature of the third blocker is 300-320℃.

3. The method for staged equal steam injection in a thermal recovery horizontal well according to claim 2, characterized in that, In S2, the first plug is made of PVC. The second plug is made of ABS or PMMA material; The third plug is made of PE material.

4. The method for staged equal steam injection in a thermal recovery horizontal well according to claim 2, characterized in that, In S2, the thermal recovery packer is set at a position that avoids the casing coupling position. All thermal recovery packers above the top thermal recovery packer are equipped with heat-insulating oil pipes. If there are no heat-insulating oil pipes or if the heat-insulating oil pipes fail, the annulus above the thermal recovery packer is filled with nitrogen. If two steam injection well sections of the same type are adjacent, then the two adjacent thermal recovery packers are merged, and a first-stage thermal recovery packer is installed.

5. The method for staged equal steam injection in a thermal recovery horizontal well according to claim 2, characterized in that, In S2, after the injector is opened in Class II and Class III well sections, profile control measures are implemented simultaneously. After the profile control system is injected, more than 5,000 standard cubic meters of nitrogen gas are replaced in the nitrogen slug.

6. A method for staged equal steam injection in a thermal recovery horizontal well according to any one of claims 1, characterized in that, In S1, well sections with a remaining oil saturation of ≥50% that are either secondary or poorly activated are classified as Class I well sections. Well sections with a residual oil saturation of 30% < 50% and poor utilization rate are classified as Class II well sections. Well sections with a residual oil saturation of 20% to 30% that are either under-operation or poorly operated are classified as Class III well sections. Steam demand for Class I well sections: Steam demand for Class II well sections: Steam demand for Class III well sections = 4-6:2-4:1-3.

7. The method for staged equal steam injection in a thermal recovery horizontal well according to claim 6, characterized in that, In S1, if one of the Class I, Class II, and Class III well sections is missing, the steam distribution of the other well sections is increased proportionally.

8. The method for staged equal steam injection in a thermal recovery horizontal well according to claim 1, characterized in that, In S1, at least three time-segmented temperature curves are used to identify the active use segment, the secondary use segment, and the differential use segment.

9. A method for staged equal steam injection in a thermal recovery horizontal well according to any one of claims 1-8, characterized in that, It also includes S3, which involves switching to pumping after the well is simmered and vented.

10. A staged, segmented, balanced steam injection string for thermal recovery horizontal wells, characterized in that... The steam injection string is designed according to step S2 of the step-by-step equalization steam injection method for thermal recovery horizontal wells as described in any one of claims 1-8.

Images