Thickened oil fireflooding connectivity judgment method
By monitoring changes in pressure, nitrogen, carbon oxides, and oil production between injection wells and production wells during heavy oil fire flooding, and combining this with on-site control, the problem of determining fire line connectivity in heavy oil fire flooding was solved, improving recovery rate and control efficiency while reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-11
- Publication Date
- 2026-05-12
AI Technical Summary
The lack of accurate methods for determining fire line connectivity in existing heavy oil fire flooding technologies leads to difficulties in fire flooding control, low recovery rates, and high tracer costs.
By monitoring the changes in pressure, nitrogen content, carbon dioxide content, and oil production between the injection well and surrounding production wells with ignition time, and combining this with on-site control measures, the initial, low-level, high-temperature, and effective connections are determined and established to optimize the combustion direction of the ignition line.
It improved the recovery rate of heavy oil fire flooding, clarified the direction of single-well control, maximized the utilization of oil reservoirs, and reduced monitoring costs.
Smart Images
Figure CN122014233A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of heavy oil development technology, specifically relating to a method for determining the connectivity of heavy oil fire-driven processes. Background Technology
[0002] In heavy oil development, fire flooding is an important method for oil recovery. In recent years, numerous field tests have been conducted both domestically and internationally, and the core technologies for fire flooding are basically mature. However, due to the highly complex mechanism of fire flooding, the control of the combustion line is extremely difficult. Without effective and precise means of monitoring the combustion line, it is necessary to find a suitable method for determining the connectivity between injection and production wells in high-temperature fire flooding of abandoned reservoirs after steam injection in heavy oil. This will provide technical support for fire flooding control and improve the overall recovery efficiency. Generally, steam injection recovery rates are only 10%–25%, while after switching to fire flooding, the overall recovery rate can reach over 60%.
[0003] In the prior art, the invention with publication number "CN104612666A" discloses a method for describing the combustion front position of a linear well network in fire flooding. First, it establishes a linear well network based on the defined positional relationship between injection and production wells. The injection wells ignite the oil reservoir. Then, during injection, the method continuously monitors the change in injection pressure over time to determine well connectivity. Acid values between wells are intermittently measured to determine the location of the fire front. During fire flooding, it is crucial to ensure continuous air injection from the injection wells to guarantee continuous combustion in the oil reservoir, thereby understanding the combustion dynamics and relevant reservoir parameters. This method requires a sufficient amount of sampling data and simultaneous oil sample extraction. For field implementation, this not only involves a huge workload but also means that oil samples may not be obtained from production wells simultaneously, complicating subsequent analysis and judgment.
[0004] In the prior art, invention publication number "CN104612666A" provides a method for monitoring the temperature of the leading edge of the fire line. This method includes the following steps: during gas injection in a gas injection well, an isotope-labeled tracer is injected into the injection pipeline and injected to the bottom of the well along with the air; samples are periodically taken from the production well for analysis, and the combustion temperature of the oil layer is determined by detecting the decomposition products containing the corresponding isotopes. This method is applied to monitoring the ignition process of a fire-prone oil layer in a heavy oil reservoir and the combustion temperature of the oil layer during the production process, and can determine the combustion state and connectivity of the oil layer. This technology mainly has the following drawbacks: firstly, the range of tracers suitable for high temperatures is very limited; secondly, the cost of using tracers is high, making the monitoring of the fire line temperature in a region very expensive. Summary of the Invention
[0005] The purpose of this invention is to provide a method for determining the connectivity of heavy oil fire-driven systems, in order to overcome the above-mentioned technical defects.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for determining the connectivity of heavy oil fire-driven pipelines, characterized by comprising the following steps: S1. Obtain a schematic diagram of the pressure change trend of the injection well after ignition with ignition time. Based on the obtained schematic diagram of the pressure change trend with ignition time, determine whether the injection well and the surrounding production wells have established an initial connection. If the initial connection has been successfully established, proceed to step S2. If the initial connection has not been successfully established, on-site adjustment of the surrounding production wells is required. S2. Obtain a schematic diagram showing the trend of nitrogen content in flue gas produced after ignition of surrounding production wells as a function of ignition time. Based on the obtained schematic diagram showing the trend of nitrogen content as a function of ignition time, determine whether a low-level connection has been established between the injection well and the surrounding production wells. If the low-level connection has been successfully established, proceed to step S3. If the low-level connection has not been successfully established, on-site control of the surrounding production wells is required. S3. Obtain a schematic diagram showing the trend of carbon dioxide content in the flue gas produced after the surrounding production wells are ignited, and determine whether the injection well and the surrounding production wells have established a high-temperature connection based on the obtained schematic diagram of the trend of carbon dioxide content with ignition time. If the high-temperature connection has been successfully established, proceed to step S4; if the high-temperature connection has not been successfully established, on-site control of the surrounding production wells is required. S4. Obtain a schematic diagram showing the trend of oil production over time after ignition of surrounding production wells. Based on the obtained schematic diagram, determine whether an effective connection has been established between the injection well and the surrounding production wells. If the effective connection has been successfully established, the production well will start to produce oil steadily and continuously. If the effective connection has not been successfully established, on-site control of the production well is required.
[0007] Further, in step S1, the method for obtaining the schematic diagram of the pressure change trend of the injection well after ignition with ignition time is as follows: read the pressure value according to the automatic control device installed at the injection wellhead, and obtain the pressure change trend curve of the injection well after ignition with ignition time according to the read pressure value and its corresponding ignition time.
[0008] Furthermore, in step S1, the method for determining whether the initial connection has been successfully established is as follows: if the wellheads of the surrounding production wells begin to produce gas and the pressure of the injection well decreases, it proves that the initial connection has been successfully established; if the wellheads of the surrounding production wells do not produce gas and the pressure of the injection well does not decrease, it indicates that the initial connection has not been successfully established.
[0009] Furthermore, the method for determining the time when the initial connection has been successfully established is as follows: analyze the pressure change diagram after the injection well is ignited. When the pressure begins to drop for the first time, it indicates that a pressure relief point has begun to appear. The ignition time corresponding to this pressure relief point is the time when the underground fire line begins to advance towards the surrounding production wells, and it is also the time when the injection well establishes the initial connection with the surrounding production wells.
[0010] As a further optimization of the present invention, in S1, if the initial connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: First, ensure that both the injection well and the surrounding production wells can be opened for production normally, and then simultaneously adjust the parameters of the surrounding production wells so that the production fluid of each production well differs by ±3 tons, until the initial connection is successfully established.
[0011] Furthermore, in step S2, the method for obtaining the schematic diagram of the change trend of nitrogen content in the flue gas produced after the surrounding production wells are as follows: after ignition, the gas composition at the wellhead of the surrounding production wells is monitored by a gas chromatograph to obtain nitrogen content data. Based on the obtained nitrogen content data and its corresponding ignition time, the curve of the change trend of nitrogen content with ignition time is obtained.
[0012] Furthermore, in step S2, the method for determining whether the low-level connection has been successfully established is as follows: if the nitrogen content is >0%, it proves that the low-level connection between the injection well and the surrounding production wells has been successfully established; if no nitrogen content is found in the components, it indicates that the injection well has not established a low-level connection with the surrounding production wells.
[0013] Furthermore, the method for determining the time when the low-level connection has been successfully established is as follows: analyze the trend diagram of nitrogen content change in the flue gas produced by the surrounding production wells. When the N2 content in the gas composition is >0%, the ignition time at this time is the time when the underground fire line advances smoothly to the surrounding production wells, and it is also the time when the low-level connection between the injection well and the surrounding production wells is established.
[0014] As a further optimization of the present invention, in step S2, if the low-level connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: First, adjust the parameters of the wells where no nitrogen content is found and the adjacent production wells with nitrogen content > 0%. If the parameter adjustment is ineffective, implement steam injection and huff-and-puff measures for the wells where no nitrogen content is found until the low-level connection is successfully established.
[0015] Furthermore, in step S3, the method for obtaining the schematic diagram of the change trend of carbon dioxide content in the flue gas produced after the surrounding production wells are as follows: after ignition, the gas composition at the wellhead of the surrounding production wells is monitored by a portable flue gas analyzer to obtain carbon dioxide content data. Based on the obtained carbon dioxide content data and its corresponding ignition time, the trend curve of the change of carbon dioxide content with ignition time is obtained.
[0016] Furthermore, in step S3, the method for determining whether the high-temperature connection has been successfully established is as follows: if the carbon dioxide content is >10%, it proves that the injection well and the surrounding production wells have successfully established a high-temperature connection; if the carbon dioxide content is <10%, it indicates that the injection well has not established a high-temperature connection with the surrounding production wells.
[0017] Furthermore, the method for determining the time when the high-temperature connection has been successfully established is as follows: analyze the schematic diagram of the change trend of carbon dioxide content in the flue gas produced by the surrounding production wells. When the carbon dioxide content in the gas composition is >10%, the ignition time at this time is the time when high-temperature combustion is achieved in the direction of the production well, which is also the time when the high-temperature connection between the injection well and the surrounding production wells is established.
[0018] As a further optimization of the present invention, in step S3, if the high-temperature connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: adjust the parameters of the wells with carbon dioxide content <10% and the adjacent production wells, and at the same time, control the production of the well with the highest gas production shown in the production report of the surrounding production well group by using the casing pressure valve or directly controlling the shut-off, so as to ensure that the fire line is evenly advanced to the direction of weaker combustion until the high-temperature connection is successfully established.
[0019] Furthermore, in step S4, the method for determining whether effective connectivity has been successfully established is as follows: when the water cut of the production well begins to decrease and remains stable at 60-80%, and the wellhead begins to produce oil steadily and continuously, it proves that the injection well and the surrounding production wells have been successfully and stably connected. If this standard is not met, it means that the non-injection well has not established effective connectivity with the surrounding production wells.
[0020] Furthermore, the method for determining the time when the effective connection has been successfully established is as follows: analyze the oil production diagram of the surrounding production wells, and when the oil production begins to rise, it proves that the flue gas drive stage has been entered. The ignition time at this time is the time when the oil wall is established and steadily advanced in the direction of the production well, which is also the time when the effective connection between the injection well and the surrounding production wells is established.
[0021] As a further optimization of the present invention, in step S4, if the effective connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: by performing a priming and ignition effect on the production wells, the ignition line is directed towards the priming and ignition wells until an effective connection is successfully established.
[0022] Compared with the prior art, the present invention has the following beneficial effects: The heavy oil fire-flooding connectivity judgment method provided by this invention can provide early warning based on field conditions, especially for abnormal situations in individual wells. It can also clarify the direction of control in a single well, thereby changing the direction of fire line combustion, increasing the degree of reservoir activation, maximizing recovery rate, and ultimately improving the overall development effect of fire-flooding.
[0023] To make the above description of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description
[0024] Figure 1 This is a schematic diagram illustrating the process of the fire line advancing from the injection well to the surrounding production wells.
[0025] Figure 2 This is a schematic diagram showing the pressure change trend of the injection well after ignition with ignition time.
[0026] Figure 3 This is a schematic diagram showing the trend of nitrogen content in the flue gas produced after the production well is ignited, as a function of ignition time.
[0027] Figure 4 This is a schematic diagram showing the trend of carbon dioxide content in the flue gas produced after the production well is ignited, as a function of ignition time.
[0028] Figure 5 This is a schematic diagram showing the trend of oil production over time after the production well is ignited.
[0029] Figure 6 This is a schematic diagram illustrating the results of a throughput and induction effect measure implemented on a production well that failed to establish an effective connection.
[0030] Figure 7 This is the production curve of well H8.
[0031] Explanation of reference numerals in the attached figures: 1. Production well; 2. Injection well; 3. Leading edge of the fire line. Detailed Implementation
[0032] The invention can be further understood in conjunction with the following detailed description of preferred embodiments and included examples. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. If any definition of a specific term disclosed in the prior art differs from any definition provided herein, the definition provided herein shall prevail.
[0033] In a typical embodiment of this application, a method for determining the connectivity of heavy oil fire-driven pipelines is provided, comprising the following steps: S1. Obtain a schematic diagram of the pressure change trend of the injection well after ignition with ignition time. Based on the obtained schematic diagram of the pressure change trend with ignition time, determine whether the injection well and the surrounding production wells have established an initial connection. If the initial connection has been successfully established, proceed to step S2. If the initial connection has not been successfully established, on-site adjustment of the surrounding production wells is required. S2. Obtain a schematic diagram showing the trend of nitrogen content in flue gas produced after ignition of surrounding production wells as a function of ignition time. Based on the obtained schematic diagram showing the trend of nitrogen content as a function of ignition time, determine whether a low-level connection has been established between the injection well and the surrounding production wells. If the low-level connection has been successfully established, proceed to step S3. If the low-level connection has not been successfully established, on-site control of the surrounding production wells is required. S3. Obtain a schematic diagram showing the trend of carbon dioxide content in the flue gas produced after the surrounding production wells are ignited, and determine whether the injection well and the surrounding production wells have established a high-temperature connection based on the obtained schematic diagram of the trend of carbon dioxide content with ignition time. If the high-temperature connection has been successfully established, proceed to step S4; if the high-temperature connection has not been successfully established, on-site control of the surrounding production wells is required. S4. Obtain a schematic diagram showing the trend of oil production over time after ignition of surrounding production wells. Based on the obtained schematic diagram, determine whether an effective connection has been established between the injection well and the surrounding production wells. If the effective connection has been successfully established, the production well will start to produce oil steadily and continuously. If the effective connection has not been successfully established, on-site control of the production well is required.
[0034] In another typical embodiment of this application, a method for determining the connectivity of heavy oil fire-driven operations is mentioned, which includes the following detailed steps: S1. Obtain a schematic diagram of the pressure change trend of the injection well after ignition with ignition time. Based on the obtained schematic diagram of the pressure change trend with ignition time, determine whether the injection well and the surrounding production wells have established an initial connection. If the initial connection has been successfully established, proceed to step S2. If the initial connection has not been successfully established, on-site adjustment of the surrounding production wells is required. In step S1, the method for determining whether the initial connection has been successfully established is as follows: if the wellheads of the surrounding production wells begin to produce gas and the pressure of the injection well decreases, it proves that the initial connection has been successfully established; if the wellheads of the surrounding production wells do not produce gas and the pressure of the injection well does not decrease, it indicates that the initial connection has not been successfully established.
[0035] Furthermore, if the initial connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: First, ensure that both the injection well and the surrounding production wells can be opened for production normally. Then, simultaneously adjust the parameters of the surrounding production wells so that the fluid production of each production well differs by ±3 tons until the initial connection is successfully established.
[0036] S2. Obtain a schematic diagram showing the trend of nitrogen content in flue gas produced after ignition of surrounding production wells as a function of ignition time. Based on the obtained schematic diagram showing the trend of nitrogen content as a function of ignition time, determine whether a low-level connection has been established between the injection well and the surrounding production wells. If the low-level connection has been successfully established, proceed to step S3. If the low-level connection has not been successfully established, on-site control of the surrounding production wells is required. In S2, the method for determining whether a low-level connection has been successfully established is as follows: if the nitrogen content is >0%, it proves that the low-level connection between the injection well and the surrounding production wells has been successfully established; if no nitrogen content is found in the components, it indicates that the injection well has not established a low-level connection with the surrounding production wells.
[0037] Furthermore, if the low-level connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: First, adjust the production parameters of the wells where no nitrogen content is found and the adjacent production wells with nitrogen content > 0%. If the adjustment of parameters is ineffective, implement steam injection and huff-and-puff measures for the wells where no nitrogen content is found until the low-level connection is successfully established.
[0038] S3. Obtain a schematic diagram showing the trend of carbon dioxide content in the flue gas produced after the surrounding production wells are ignited, and determine whether the injection well and the surrounding production wells have established a high-temperature connection based on the obtained schematic diagram of the trend of carbon dioxide content with ignition time. If the high-temperature connection has been successfully established, proceed to step S4; if the high-temperature connection has not been successfully established, on-site control of the surrounding production wells is required. Furthermore, in step S3, the method for determining whether the high-temperature connection has been successfully established is as follows: if the carbon dioxide content is >10%, it proves that the injection well and the surrounding production wells have successfully established a high-temperature connection; if the carbon dioxide content is <10%, it indicates that the injection well has not established a high-temperature connection with the surrounding production wells.
[0039] Furthermore, if the high-temperature connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: adjust the parameters of wells with carbon dioxide content <10% and adjacent production wells, and at the same time, control the production of the well with the highest gas production shown in the production report of the surrounding production well group by using the casing pressure valve or directly shutting it off to ensure that the fire line is evenly advanced in the direction of weaker combustion until the high-temperature connection is successfully established.
[0040] S4. Obtain a schematic diagram showing the trend of oil production over time after ignition of surrounding production wells. Based on the obtained schematic diagram, determine whether an effective connection has been established between the injection well and the surrounding production wells. If the effective connection has been successfully established, the production well will start to produce oil steadily and continuously. If the effective connection has not been successfully established, on-site control of the production well is required.
[0041] Furthermore, in step S4, the method for determining whether effective connectivity has been successfully established is as follows: when the water cut of the production well begins to decrease and remains stable at 60-80%, and the wellhead begins to produce oil steadily and continuously, it proves that the injection well and the surrounding production wells have been successfully and stably connected. If this standard is not met, it means that the non-injection well has not established effective connectivity with the surrounding production wells.
[0042] Furthermore, if effective connection is not successfully established, the specific method for on-site control of surrounding production wells is as follows: by performing priming and injection on the production wells, the ignition line is directed towards the priming and injection wells until effective connection is successfully established.
[0043] In yet another typical embodiment of this application, a method for determining the connectivity of heavy oil fire-driven operations includes the following further detailed steps: S1. Read the pressure value from the automatic control device installed at the injection wellhead, and obtain the pressure change trend curve of the injection well after ignition with ignition time based on the read pressure value and its corresponding ignition time.
[0044] Based on the obtained pressure change trend diagram with ignition time, it is determined whether the injection well and surrounding production wells have established initial connectivity. The specific method is as follows: if the surrounding production wells begin producing gas and the injection well pressure decreases, it proves that the initial connectivity has been successfully established; if no gas is produced at the surrounding production wells and the injection well pressure does not decrease, it indicates that the initial connectivity has not been successfully established. It is worth mentioning that the method for determining the time when the initial connectivity has been successfully established is as follows: analyze the pressure change diagram after the injection well ignites. When the pressure first begins to decrease, it indicates the start of a pressure relief point. The ignition time corresponding to this pressure relief point is the time when the underground fire line begins to advance towards the surrounding production wells, and it is also the time when the injection well and surrounding production wells establish initial connectivity.
[0045] If the initial connection has been successfully established, proceed to the next step, namely step S2; if the initial connection has not been successfully established, on-site control of the surrounding production wells is required. The specific control method is as follows: first, ensure that the injection well and the surrounding production wells can be opened for production normally, and then simultaneously adjust the parameters of the surrounding production wells so that the production fluid of each production well differs by ±3 tons, until the initial connection is successfully established.
[0046] S2. After ignition, the gas composition of the surrounding production wellhead is monitored by gas chromatography detection method (gas chromatograph) of the produced gas from the fire drive to obtain nitrogen content data. Based on the obtained nitrogen content data and its corresponding ignition time, the trend curve of the nitrogen content change with ignition time is obtained.
[0047] Based on the obtained schematic diagram of nitrogen content variation with ignition time, it is determined whether a low-level connection has been established between the injection well and the surrounding production wells. The specific method is as follows: if the nitrogen content is >0%, it proves that the low-level connection between the injection well and the surrounding production wells has been successfully established; if no nitrogen content is found in the components, it indicates that the injection well has not established a low-level connection with the surrounding production wells. It is worth mentioning that the method for determining the time when the low-level connection has been successfully established is as follows: analyze the schematic diagram of nitrogen content variation in the flue gas produced by the surrounding production wells. When the N2 content in the gas components is >0%, the ignition time at this point is the time when the underground fire line successfully advances to the surrounding production wells, and it is also the time when the low-level connection between the injection well and the surrounding production wells is established.
[0048] If the low-level connection has been successfully established, proceed to step S3; if the low-level connection has not been successfully established, on-site control of the surrounding production wells is required. The specific control method is as follows: first, adjust the parameters of the wells where no nitrogen content is found and the adjacent production wells with nitrogen content > 0%. If the parameter adjustment has no effect, implement steam injection and huff-and-puff measures for the wells where no nitrogen content is found until the low-level connection is successfully established.
[0049] S3. After ignition, the gas composition at the wellhead of the surrounding production well is monitored using a portable flue gas analyzer to obtain carbon dioxide content data. Based on the obtained carbon dioxide content data and its corresponding ignition time, a trend curve of the carbon dioxide content changing with ignition time is obtained.
[0050] Based on the obtained schematic diagram of the carbon dioxide content change trend with ignition time, it is determined whether a high-temperature connection has been established between the injection well and the surrounding production wells. The specific determination method is as follows: if the carbon dioxide content is >10%, it proves that a high-temperature connection has been successfully established between the injection well and the surrounding production wells; if the carbon dioxide content is <10%, it indicates that a high-temperature connection has not been established between the injection well and the surrounding production wells. It is worth mentioning that the method for determining the time when the high-temperature connection has been successfully established is as follows: analyze the schematic diagram of the carbon dioxide content change trend in the flue gas produced by the surrounding production wells. When the carbon dioxide content in the gas composition is >10%, the ignition time at this time, that is, the time when high-temperature combustion (i.e., the temperature of the leading edge 3 of the fire line) is reached in the direction of the production well, is also the time when the high-temperature connection between the injection well and the surrounding production wells is established.
[0051] If the high-temperature connection has been successfully established, proceed to step S4; if the high-temperature connection has not been successfully established, on-site control of the surrounding production wells is required. The specific control method is as follows: adjust the parameters of wells with carbon dioxide content <10% and adjacent production wells, and at the same time, control the production of the well with the highest gas production shown in the production report of the surrounding production well group by using the casing pressure valve or directly shutting it off to ensure that the fire line is evenly advanced in the direction of weaker combustion until the high-temperature connection is successfully established.
[0052] S4. Read the daily oil production data in the production single-well metering system, and then obtain a schematic diagram of the trend of oil production over time after the surrounding production wells are ignited.
[0053] Based on the obtained diagram showing the trend of oil production over time, it is determined whether an effective connection has been established between the injection well and the surrounding production wells. The specific method is as follows: when the water cut of the production well begins to decrease and stabilizes at 60-80%, and the wellhead begins to produce oil steadily and continuously, it proves that the injection well and the surrounding production wells have successfully and stably established an effective connection. If this standard is not met, it indicates that the non-injected well has not established an effective connection with the surrounding production wells. It is worth mentioning that the method for determining the time when the effective connection has been successfully established is as follows: analyze the oil production diagrams of the surrounding production wells. When the oil production begins to increase, it indicates the entry into the flue gas drive stage. The ignition time at this point, i.e., the time it takes for an oil wall to be built and steadily advanced in the direction of the production well, is also the time when the effective connection between the injection well and the surrounding production wells is established.
[0054] If effective connectivity has been successfully established, the production well will begin to produce oil steadily and continuously. If effective connectivity has not been successfully established, on-site control of the production well is required. The specific control method is to use a priming and injection system to guide the fire line towards the priming and injection well until effective connectivity is successfully established.
[0055] Under the condition of successful ignition, the heavy oil fire-drive connectivity determination method of the present invention is as follows: The mechanism and process of high-temperature fire drive for heavy oil: Air is continuously injected into the formation through injection well 2, causing the surrounding crude oil to combust at high temperatures in situ, forming a narrow high-temperature combustion zone. This zone then propagates from injection well 2 towards the surrounding production well 1 (see [reference]). Figure 1 High temperatures during the period (i.e.) Figure 1 3) The crude oil near the wellhead is distilled and cracked. Light oil and steam move forward and exchange heat with rocks and fluids, condensing down. The heavy hydrocarbons left after distillation and cracking - coke - are burned as fuel, and the resulting flue gas heats and displaces the crude oil.
[0056] The first step is to obtain a schematic diagram showing the pressure change trend of injection well 2 after ignition with ignition time. When the pressure begins to drop for the first time, it indicates the start of a pressure relief point, proving that injection well 2 has established initial connectivity with the surrounding production well 1 (e.g., Figure 2 (as shown) The second step is to obtain a schematic diagram showing the trend of nitrogen (N2) content in the flue gas produced after the surrounding production wells are ignited, as a function of ignition time. Figure 3 When the N2 content in the gas component is >0%, it proves that a low-level connection has been successfully established between the injection well and the surrounding production wells. The third step is to obtain a schematic diagram showing the change in carbon dioxide (CO2) content in the flue gas produced after the surrounding production wells are ignited, as a function of ignition time (e.g., Figure 4 As shown in the figure, when the CO2 content in the gas component is >10%, it proves that a high-temperature connection has been established between the injection well and the surrounding production wells; The fourth step is to obtain a schematic diagram showing the trend of oil production changes with ignition time after ignition of surrounding production wells (e.g., Figure 5 As shown in the figure, when the oil production begins to rise, it proves that the flue gas drive stage has been entered, and an effective connection has been successfully established between the injection well and the surrounding production wells.
[0057] The present invention will be further described below with reference to specific implementation examples: Example 1 The old Hongqian 1 well area underwent steam injection and steam drive from 1991 to 2014, achieving a recovery rate of 32.3%, but the regional rated recovery rate was only 27.2%, essentially rendering it abandoned. In 2018, the area transitioned to fire-driven development and production. During this period, by implementing the heavy oil fire-driven connectivity assessment method described in this invention, 75 well groups were successfully ignited, and all 492 corresponding production wells achieved connectivity. In nearly six years of ignition, cumulative oil production reached 696,000 tons, with a stage recovery rate of 13.3%.
[0058] Example 2 Well H1 is a production well in the second line of an injection well. After its ignition in 2018, all surrounding production wells produced gas, but well H1 did not, indicating that the fire line was not well-developed in that direction. After applying the aforementioned heavy oil fire-flood connectivity assessment method to this well and performing huff-and-puff induction, if... Figure 6 As shown, daily gas production increased from 0 to 314 cubic meters, and daily oil production increased from 0.2 tons to 1.5 tons.
[0059] Wells h2-h7 are the production wells of the hH01-hH07 injection well group. All six wells are in a low-fluid-production state. After simultaneously adjusting this well and the surrounding wells using the above-mentioned heavy oil fire-drive connectivity judgment method, the results are shown in Table 1 below. Table 1 is a comparison table of changes before and after the field single-well adjustment of h2-h7 wells. As can be seen from Table 1, the fluid volume and oil volume of the six wells have increased significantly.
[0060] Table 17 Comparison of Changes Before and After On-site Single-Well Control in Well Groups
[0061] Well H8 is a production well in a certain well group, such as... Figure 7 As shown, after the well was ignited, it took effect quickly, with a significant decrease in water cut and a significant increase in oil production, indicating that a stable oil wall was established near the well. However, due to the excessive development in the direction of the well, the gas production was too large. The well was promptly shut down for two months, and normal production resumed after it was reopened. Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.
Claims
1. A method for determining the connectivity of heavy oil fire-driven combustion systems, characterized in that, Includes the following steps: S1. Obtain a schematic diagram of the pressure change trend of the injection well after ignition with ignition time. Based on the obtained schematic diagram of the pressure change trend with ignition time, determine whether the injection well and the surrounding production wells have established an initial connection. If the initial connection has been successfully established, proceed to step S2. If the initial connection has not been successfully established, on-site adjustment of the surrounding production wells is required. S2. Obtain a schematic diagram showing the trend of nitrogen content in flue gas produced after ignition of surrounding production wells as a function of ignition time. Based on the obtained schematic diagram showing the trend of nitrogen content as a function of ignition time, determine whether a low-level connection has been established between the injection well and the surrounding production wells. If the low-level connection has been successfully established, proceed to step S3. If the low-level connection has not been successfully established, on-site control of the surrounding production wells is required. S3. Obtain a schematic diagram showing the trend of carbon dioxide content in the flue gas produced after the surrounding production wells are ignited, and determine whether the injection well and the surrounding production wells have established a high-temperature connection based on the obtained schematic diagram of the trend of carbon dioxide content with ignition time. If the high-temperature connection has been successfully established, proceed to step S4; if the high-temperature connection has not been successfully established, on-site control of the surrounding production wells is required. S4. Obtain a schematic diagram showing the trend of oil production over time after ignition of surrounding production wells. Based on the obtained schematic diagram, determine whether an effective connection has been established between the injection well and the surrounding production wells. If the effective connection has been successfully established, the production well will start to produce oil steadily and continuously. If the effective connection has not been successfully established, on-site control of the production well is required.
2. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S1, the method for obtaining the schematic diagram of the pressure change trend of the injection well after ignition with ignition time is as follows: read the pressure value according to the automatic control device installed at the injection wellhead, and obtain the pressure change trend curve of the injection well after ignition with ignition time according to the read pressure value and its corresponding ignition time.
3. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S1, the method for determining whether the initial connection has been successfully established is as follows: if the wellheads of the surrounding production wells begin to produce gas and the pressure of the injection well decreases, it proves that the initial connection has been successfully established; if the wellheads of the surrounding production wells do not produce gas and the pressure of the injection well does not decrease, it indicates that the initial connection has not been successfully established.
4. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1 or 3, characterized in that, The method for determining the time when the initial connection has been successfully established is as follows: Analyze the pressure change diagram after the injection well is ignited. When the pressure begins to drop for the first time, it indicates that a pressure relief point has begun to appear. The ignition time corresponding to this pressure relief point is the time when the underground fire line begins to advance towards the surrounding production wells, and it is also the time when the injection well establishes the initial connection with the surrounding production wells.
5. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In S1, if the initial connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: First, ensure that both the injection well and the surrounding production wells can be opened for production normally. Then, adjust the parameters of the surrounding production wells at the same time so that the production fluid of each production well differs by ±3 tons until the initial connection is successfully established.
6. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S2, the method for obtaining the schematic diagram of the change trend of nitrogen content in the flue gas produced after the surrounding production wells are as follows: after ignition, the gas composition at the wellhead of the surrounding production wells is monitored by a gas chromatograph to obtain nitrogen content data. Based on the obtained nitrogen content data and its corresponding ignition time, the curve of the change trend of nitrogen content with ignition time is obtained.
7. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S2, the method for determining whether the low-level connection has been successfully established is as follows: if the nitrogen content is >0%, it proves that the low-level connection between the injection well and the surrounding production wells has been successfully established; if no nitrogen content is found in the components, it indicates that the injection well has not established a low-level connection with the surrounding production wells.
8. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1 or 7, characterized in that, The method for determining the time when the low-level connection has been successfully established is as follows: Analyze the trend diagram of nitrogen content change in the flue gas produced by the surrounding production wells. When the N2 content in the gas composition is >0%, the ignition time at this time is the time when the underground fire line advances smoothly to the surrounding production wells, and it is also the time when the low-level connection between the injection well and the surrounding production wells is established.
9. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 7, characterized in that, In S2, if the low-level connection is not successfully established, the specific method for on-site control of the surrounding production wells is as follows: First, adjust the parameters of the wells where no nitrogen content is found and the adjacent production wells with nitrogen content > 0%. If the parameter adjustment is ineffective, implement steam injection and huff-and-puff measures for the wells where no nitrogen content is found until the low-level connection is successfully established.
10. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S3, the method for obtaining the schematic diagram of the trend of carbon dioxide content in the flue gas produced after the surrounding production wells are ignited with the ignition time is as follows: after ignition, the gas composition at the wellhead of the surrounding production wells is monitored by a portable flue gas analyzer to obtain carbon dioxide content data. Based on the obtained carbon dioxide content data and its corresponding ignition time, the trend curve of carbon dioxide content with ignition time is obtained.
11. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S3, the method for determining whether the high-temperature connection has been successfully established is as follows: if the carbon dioxide content is >10%, it proves that the injection well and the surrounding production wells have successfully established a high-temperature connection; if the carbon dioxide content is <10%, it indicates that the injection well has not established a high-temperature connection with the surrounding production wells.
12. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1 or 11, characterized in that, The method for determining the time when the high-temperature connection has been successfully established is as follows: Analyze the schematic diagram of the change trend of carbon dioxide content in the flue gas produced by the surrounding production wells. When the carbon dioxide content in the gas composition is >10%, the ignition time at this time is the time when high-temperature combustion is achieved in the direction of the production well, which is also the time when the high-temperature connection between the injection well and the surrounding production wells is established.
13. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 11, characterized in that, In S3, if the high-temperature connection fails to be established, the specific method for on-site control of surrounding production wells is as follows: For wells with carbon dioxide content <10% and adjacent production wells, adjust parameters. At the same time, control production or shut down the well with the highest gas production shown in the production report of the surrounding production well group by using casing pressure valves to ensure that the fire line advances evenly in the direction of weaker combustion until a high-temperature connection is successfully established.
14. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S4, the method for determining whether effective connectivity has been successfully established is as follows: when the water cut of the production well begins to decrease and remains stable at 60-80%, and the wellhead begins to produce oil steadily and continuously, it proves that the injection well and the surrounding production wells have been successfully and stably connected. If this standard is not met, it means that the non-injection well has not established effective connectivity with the surrounding production wells.
15. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1 or 14, characterized in that, The method for determining the time when the effective connection has been successfully established is as follows: Analyze the oil production diagram of the surrounding production wells. When the oil production begins to rise, it proves that the flue gas drive stage has been entered. The ignition time at this time is the time when the oil wall is established and steadily advanced in the direction of the production well, which is also the time when the effective connection between the injection well and the surrounding production wells is established.
16. The method for determining the connectivity of heavy oil fire-driven combustion according to claim 1, characterized in that, In step S4, if effective connection is not successfully established, the specific method for on-site control of surrounding production wells is as follows: by performing a priming and injection process on the production wells, the ignition wire is directed towards the priming and injection wells until effective connection is successfully established.