Gas drive front monitoring method

Abstract

The application discloses a gas drive front edge monitoring method, which is applied to a horizontal well or a high-inclination well and comprises the following steps: S1, field operation preparation; S2, field exploration and obvious protection mark for a measuring point; S3, field equipment debugging; S4, laying a measuring line along a ground projection of a perforated well section and carrying out gas injection testing; S5, obtaining and saving testing data and completing monitoring; and S6, pre-processing and editing the testing data. Therefore, the gas drive front edge monitoring method provides effective support and basis for reasonably regulating and controlling a well opening and closing system and process measures.

Description

Technical Field

[0001] This invention relates to the field of horizontal well and highly deviated well reservoir technology, and in particular to a gas drive front monitoring method and system. Background Technology

[0002] Oil and natural gas are important energy resources in my country. With social development, the contradiction between my country's demand for oil and gas resources and the limited availability of these resources has become increasingly prominent. To alleviate this contradiction, major oilfields and oil companies have adopted corresponding measures to stabilize and increase production. In particular, in the past two decades, enhanced oil recovery (EOR) technology has been widely applied and rapidly developed in my country's major eastern oilfields, which are in the middle and late stages of exploration and development. It has become an essential means for oilfields and oil companies to achieve high and stable production. Currently, older oilfields are entering the third stage of oil recovery, and gas-driven measures for reservoirs with low porosity have shown good results in improving oil recovery.

[0003] However, due to the non-homogeneity and anisotropy of underground reservoir media, many challenges arise in oil and gas field development, especially during the implementation of EOR (Extended Orifice Reservoir) technology. These challenges include difficulties in accurately assessing the distribution of remaining oil, water flooding of injection well networks, water channeling, and low control capabilities of infill well networks. These problems urgently require a comprehensive solution using various detection technologies that can reflect the characteristics of underground reservoirs.

[0004] After years of effort, technologies such as surface geophysical exploration, inter-well seismic imaging, vertical seismic profiling (VSP), inter-well resistivity and electromagnetic imaging, and tracers have been developed. However, due to limitations in detection resolution, field conditions, and the cost of measuring instruments, these technologies are severely restricted in practical applications. Well-to-surface combined potential monitoring, which utilizes both charging and natural potentials, has been widely applied in actual production due to its low cost and less stringent environmental requirements, yielding reliable measured data in development wells across multiple oilfields.

[0005] On the other hand, from a physical mechanism perspective, due to the significant difference in resistivity between oil / gas and water, injecting appropriate high-salinity fluids into the well allows for the generation of abundant resistivity information reflecting water saturation in the well-to-surface combined potential monitoring data. Through appropriate data processing and interpretation techniques, resistivity imaging results showing the differences between oil, gas, and water can be obtained. With the rapid development of electronic and computer technologies, field data acquisition technology for well / surface combined potential monitoring has matured and has been widely applied in numerous oilfields both domestically and internationally, yielding a large amount of qualified measured data. This technology has become another key reservoir geophysical technique following inter-well seismic imaging, and in some practical applications, such as the response to changes in reservoir oil / gas content or water saturation, it is superior to inter-well seismic imaging.

[0006] Among existing geophysical monitoring methods for oil fields, well logging technology provides a detection range of tens of centimeters to several meters around the wellbore, but it cannot detect lateral information between wells. While seismic geophysical methods address lateral exploration, their resolution is very low, yielding only block information and making it difficult to achieve quantitative or semi-quantitative analysis of different layers. In contrast, well-to-surface potential imaging technology has a very high resolution for oil and water beneath the formation, and can provide quantitative calculations (layer resistivity, saturation content, distance, and range) for the area around local wells in an oil field, covering several hundred meters.

[0007] For example, patent document CN106869913B discloses a method for detecting the water drive front of an oilfield water injection well using well location technology. It uses water drive, and the method cannot achieve dynamic monitoring of injection, calculate the average advance speed and the movement direction of the far well zone, nor indicate the injection sweep area.

[0008] Currently, most oilfields in China are entering the tertiary oil recovery stage. Previously used methods such as water injection and foam injection are becoming increasingly limited because conventional water injection is less effective in many microporous reservoirs. Reservoir development engineers have experimented with new gas injection methods, achieving good displacement effects and improving oil and gas recovery rates. However, obtaining information on the movement trajectory of injected gas within the reservoir—that is, the direction of injection and the distribution of its impact range—is crucial for oil and gas development engineers. Therefore, a monitoring method is needed to provide engineers with this information.

[0009] To improve oil recovery, drilling horizontal and highly deviated wells is a good method. However, monitoring horizontal and highly deviated wells is currently very difficult, and there is no effective monitoring method to provide effective support and basis for the rational regulation of well opening and closing systems and technological measures.

[0010] Therefore, the research and development of an imaging interpretation system for well / situ potential monitoring data, and its application in studying the distribution of remaining oil and the oil-water propulsion boundary, are of great significance in both theoretical and practical applications of oil and gas development.

[0011] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0012] The purpose of this invention is to provide a gas drive front monitoring method and system, which provides effective support and basis for the rational control of well opening and closing systems and process measures.

[0013] To achieve the above objectives, this invention provides a gas drive front monitoring method applicable to horizontal wells or highly deviated wells. The gas drive front monitoring method includes: Step S1, field preparation; Step S2, on-site exploration and marking of monitoring points with clear protective markers; Step S3, on-site equipment debugging; Step S4, laying out survey lines along the ground projection of the perforated well section and conducting gas injection tests; Step S5, acquiring and saving test data to complete monitoring; and Step S6, preprocessing and editing the test data.

[0014] In one embodiment of the present invention, step S1 specifically includes: field site inspection; fine-tuning of the field observation system according to site conditions; design of field construction instrument setup and storage; measurement point layout and wiring; configuration of power supply lines and return electrode lines; line continuity testing; resistance testing between power supply and return wells; determination of optimized detection parameters for weak signals from the receiver; and receiver repeatability and consistency verification.

[0015] In one embodiment of the present invention, step S2 specifically includes: observing the terrain, determining the ground route layout, confirming possible obstacles on the ground, and marking any obstacles or elevation differences at the measuring points in the received signal for adjustment during calculation. Throughout the construction process, workers clearly mark the measuring points, inspect each measuring point, and set up clear signs at the construction site.

[0016] In one embodiment of the present invention, step S3 specifically includes: connecting the transmitter to the wellhead casing, powered by a generator; placing the transmitter 20 meters away from the wellhead, laying the return electrode wire, and connecting the oil and water wells in any direction, ensuring the distance between the return electrode well and the monitoring well is greater than the target layer depth; noting the well number, connecting a wire to the well being monitored, and measuring the resistance value with a multimeter to check the integrity of the line; connecting the receiver to the measuring line, detecting changes in the received signal at each measuring point based on the transmitter power strength, and adjusting the receiver.

[0017] In one embodiment of the present invention, step S4 specifically includes: using a theodolite and compass to locate the point, measuring the projection point, and drawing the wellbore trajectory line. Eleven reference common points are set at 25-meter intervals on both sides of the projection point along the vertical wellbore trajectory line. Twelve measuring lines are set on each side of the vertical wellbore trajectory line. Using the projection point as the test base point, nine reference electrodes are set at 25-meter intervals on both sides of the projection point along the wellbore trajectory line. Measurements are performed on the measuring lines on both sides of the vertical wellbore trajectory line, and five sets of continuous and stable data are sampled for each measuring line. Specifically, the gas injection test involves injecting deoxygenated air or natural gas.

[0018] In one embodiment of the invention, the sequence of the measuring lines is as follows: starting from the wellhead direction, the first line is taken. Facing the bottom of the well away from the wellhead, the left side is measured first, followed by the right side. Twelve measuring lines are monitored sequentially on each side of the wellbore trajectory line. The projection point of each layer is set as a common reference point. Each measuring line has 6 measuring points, spaced 50 meters apart, and is 300 meters long. The interval between each measuring line is 25 meters.

[0019] In one embodiment of the present invention, step S5 further includes: drawing a rose diagram, a potential diagram, and an inverted resistivity diagram based on the test data; determining the initial propulsion sweep direction of the injected gas through injection monitoring and calculating the initial propulsion sweep velocity at the start of injection; and calculating the average propulsion sweep velocity within the test time interval by combining the results of different measurements within different time intervals.

[0020] In one embodiment of the present invention, step S6 specifically includes: performing qualitative analysis and preliminary interpretation of the test data; establishing an initial geological and geophysical model based on geological, well logging, and geophysical data; performing forward simulation and constrained inversion; calibrating the well logging resistivity of the inversion results; and calculating water saturation using the inversion resistivity results in conjunction with porosity and formation water resistivity parameters.

[0021] Compared with existing technologies, the gas drive front monitoring method and system of the present invention, using well-to-surface potential imaging technology and appropriate monitoring processes, obtains effective data information. Through inversion technology, these data are processed and interpreted to obtain the answers desired by reservoir engineers, providing effective support and basis for the rational control of well opening and closing systems and process measures. Attached Figure Description

[0022] Figure 1 This is a flowchart of a gas-driven leading edge monitoring method according to an embodiment of the present invention;

[0023] Figure 2 This is a test wiring diagram of a gas-driven leading edge monitoring method according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the gas injection influence range of the gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram of the polarization distribution of gas injection points over one month according to a gas-driven leading edge monitoring method of an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram of the relative positions of a month's potential distribution in a gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0027] Figure 6 This is a schematic diagram of the potential distribution contour lines for a gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0028] Figure 7 This is a schematic diagram of the potential distribution polarization during one month of gas injection according to a gas-driven leading edge monitoring method of an embodiment of the present invention.

[0029] Figure 8 This is a schematic diagram of the relative positions of a month's potential distribution in a gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0030] Figure 9 This is a schematic diagram of the potential distribution contour lines for a gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0031] Figure 10 This is a schematic diagram of the horizontal slice position after one month of gas injection in the gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0032] Figure 11 This is a schematic diagram of a horizontal slice inverted after one month of gas injection, according to a gas-driven leading edge monitoring method of an embodiment of the present invention.

[0033] Figure 12 This is a schematic diagram of the inversion horizontal slice position of the air-driven leading edge monitoring method according to an embodiment of the present invention.

[0034] Figure 13 This is a schematic diagram of the inversion horizontal slice of the gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0035] Figure 14 This is a schematic diagram of the position of the pre-perforation potential contour lines in a gas-driven leading-edge monitoring method according to an embodiment of the present invention.

[0036] Figure 15 This is a schematic diagram of the position of the potential contour line one month after gas injection according to a gas-driven leading edge monitoring method of an embodiment of the present invention.

[0037] Figure 16 This is a schematic diagram of obtaining the inverted resistivity of the injection layer before gas injection using a gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0038] Figure 17 This is a schematic diagram of obtaining the inversion resistivity of the injection layer one month after gas injection using a gas-driven leading edge monitoring method according to an embodiment of the present invention. Detailed Implementation

[0039] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0040] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0041] Figure 1 This is a flowchart of a gas-driven leading edge monitoring method according to an embodiment of the present invention. Figure 2 This is a test wiring diagram of a gas-driven leading edge monitoring method according to an embodiment of the present invention.

[0042] like Figures 1 to 2 As shown, in a first aspect, a gas drive front monitoring method according to a preferred embodiment of the present invention is applied to horizontal wells or highly deviated wells. The gas drive front monitoring method includes: step S1, field construction preparation; step S2, field exploration and marking the measuring points with clear protective markers; step S3, on-site equipment debugging; step S4, laying out measuring lines along the ground projection of the perforated well section and conducting gas injection tests; step S5, acquiring and saving test data to complete monitoring; and step S6, preprocessing and editing the test data.

[0043] In one embodiment of the present invention, step S1 specifically includes: field site inspection; fine-tuning of the field observation system according to site conditions; design of field construction instrument setup and storage; measurement point layout and wiring; configuration of power supply lines and return electrode lines; line continuity testing; resistance testing between power supply and return wells; determination of optimized detection parameters for weak signals from the receiver; and receiver repeatability and consistency verification.

[0044] In one embodiment of the present invention, step S2 specifically includes: observing the terrain, determining the ground route layout, confirming possible obstacles on the ground, and marking any obstacles or elevation differences at the measuring points in the received signal for adjustment during calculation. Throughout the construction process, workers clearly mark the measuring points, inspect each measuring point, and set up clear signs at the construction site.

[0045] In one embodiment of the present invention, step S3 specifically includes: connecting the transmitter to the wellhead casing, powered by a generator; placing the transmitter 20 meters away from the wellhead, laying the return electrode wire, and connecting the oil and water wells in any direction, ensuring the distance between the return electrode well and the monitoring well is greater than the target layer depth; noting the well number, connecting a wire to the well being monitored, and measuring the resistance value with a multimeter to check the integrity of the line; connecting the receiver to the measuring line, detecting changes in the received signal at each measuring point based on the transmitter power strength, and adjusting the receiver.

[0046] In one embodiment of the present invention, step S4 specifically includes: using a theodolite and compass to locate and measure the projection point, and drawing the wellbore trajectory line. Eleven reference common points are set at 25-meter intervals on both sides of the projection point along the vertical wellbore trajectory line. Twelve measuring lines are set on each side of the vertical wellbore trajectory line. Using the projection point as the test base point, nine reference electrodes are set at 25-meter intervals on both sides of the projection point along the wellbore trajectory line. Measurements are performed on the measuring lines on both sides of the vertical wellbore trajectory line, and five sets of continuous and stable data are sampled for each measuring line. The azimuth, interval, and length distance data in step S4 can be corrected according to the monitoring well conditions. Specifically, the gas injection test involves injecting deoxygenated air or natural gas.

[0047] Table 1 below shows an example of data sampled from a survey line:

[0048] Table 1

[0049]

[0050] In one embodiment of the invention, the sequence of the measuring lines is as follows: starting from the wellhead direction, the first line is taken. Facing the bottom of the well away from the wellhead, the left side is measured first, followed by the right side. Twelve measuring lines are monitored sequentially on each side of the wellbore trajectory line. The projection point of each layer is set as a common reference point. Each measuring line has 6 measuring points, spaced 50 meters apart, and is 300 meters long. The interval between each measuring line is 25 meters.

[0051] In one embodiment of the present invention, step S5 further includes: drawing a rose diagram, a potential diagram, and an inverted resistivity diagram based on the test data; determining the initial propulsion sweep direction of the injected gas through injection monitoring and calculating the initial propulsion sweep velocity at the start of injection; and calculating the average propulsion sweep velocity within the test time interval by combining the results of different measurements within different time intervals.

[0052] In one embodiment of the present invention, step S6 specifically includes: qualitative analysis and preliminary interpretation of the test data; establishing an initial geological and geophysical model based on geological, well logging, and geophysical data; forward modeling and constrained inversion; calibration of the well logging resistivity of the inversion results; and calculating water saturation using the inversion resistivity results in conjunction with porosity and formation water resistivity parameters. Through the above steps, the following objectives are achieved:

[0053] This method measured field data collected before, during, and after injection, and produced results such as rose diagrams, potential diagrams, and inverted resistivity diagrams, achieving the goal of dynamic monitoring of the injection well's transverse direction; the resistivity of all areas affected by gas injection generally increased.

[0054] By monitoring during injection, the initial propulsion direction of the injected gas can be determined, and the initial propulsion velocity at the start of injection can be calculated. By combining the results of different measurements in different time intervals, the average propulsion velocity in the test time interval and the gas migration direction in the far well zone can be calculated.

[0055] By comparing the pre- and post-injection relationships and combining the inversion results map, the affected wells in the surrounding areas are indicated in layers, explaining the reservoir heterogeneity, the connectivity of the oil layer injection channels, and the injection-production effect relationship in the gas drive development process in different orientations; the abrupt change zones in different orientations are shown, indicating the injection-affected area; and in some cases, the unaffected areas can be indicated.

[0056] By indicating the gas injection range through the results diagram, the generation of the secondary gas cap, gas drive radius, and abrupt change zone can be calculated, providing support and basis for the next step of rationally controlling the well opening and closing system and implementing process measures.

[0057] Secondly, according to a preferred embodiment of the present invention, a gas-driven front monitoring system includes: a monitoring module, an acquisition module, a storage module, and a processing and editing module. The monitoring module is used to test the monitoring well or the surface of the target layer. The acquisition module is used to acquire the data tested by the monitoring module. The storage module is used to store the test data acquired by the acquisition module. The processing and editing module is used to preprocess and edit the test data.

[0058] In practical applications, the gas drive front monitoring method of the present invention involves arranging a measurement network along the horizontal wellbore trajectory at the projection points on the ground and using potential monitoring technology to obtain useful data.

[0059] Basic cabling: (Taking Huping 42-31 well as an example) Figure 3 and Figure 4 (As shown)

[0060] Using a theodolite and compass, the projection point was measured, and the wellbore trajectory line (fishbone line) (116.3°) was drawn. Along the vertical wellbore trajectory line, 11 reference common points were set at 25-meter intervals on both sides of the projection point. Including the electrode on the projection point, there were a total of 12 points. Along both sides of the vertical wellbore trajectory line, about 12 small measuring lines were set on each side (6 measuring points are called (fish rib lines), with a maximum total of 24 lines).

[0061] like Figure 2 As shown, the survey line sequence is as follows:

[0062] 1. The direction from the wellhead is taken as the first line;

[0063] 2. With your back to the wellhead and facing the bottom of the well, measure the left side first, then the right side;

[0064] 3. Monitor 12 fish rib lines on each side of the wellbore trajectory line (fish ridge line);

[0065] 4. Each layer's projection point is set as a common reference point;

[0066] 5. Each (fish rib line) has 6 measuring points, spaced 50 meters apart, and is 300 meters long;

[0067] 6. The interval between each (fish rib line) is 25 meters.

[0068] Insulating tape and short wires are provided for timely replacement and protection of potentially damaged lines. Any major problems with the test probes or lines should be reported to the project manager immediately, and a spare line should be available on site.

[0069] Tests were conducted on wells Huping 42-31 using the following methods:

[0070] Section 2: (2057~2146m): Azimuth 115.7 degrees, displacement 410 meters, length: 86m, midpoint approximately: 2100m, displacement 410m; (The ground projection distance of the entire perforation section is approximately 280m, therefore 280 / 25m=11 lines can just cover the perforation section).

[0071] Along the wellbore trajectory line (115.7-degree line), with the projection point as the test base point, nine reference electrodes are set at 25-meter intervals on both sides of the projection point, four closer to the wellbore and five closer to the bottom of the well, plus the electrode on the projection point, for a total of ten.

[0072] right Figure 2 First, measure the left side lines 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. After measuring each line, measure the right side.

[0073] The test order on the right is: -10, -9, -8, -7, -6, -5, -4, -3, -2, -1.

[0074] according to Figure 2 The wiring method is used to measure 6×20=120 measurement points, and 5 sets of continuous and stable data are sampled for each line; the projection point is on the 5th line from left to right, with 5 lines and a distance of 125 meters along the bottom of the well, and 4 lines and a distance of 100 meters along the wellhead, and 6 points are monitored for each line.

[0075] In the forward modeling, a finite difference algorithm is proposed to adapt to existing computer resources. In the imaging interpretation, this invention employs a regularized least squares inversion imaging algorithm with inequality constraints to obtain the three-dimensional resistivity distribution of the subsurface reservoir. Based on the background resistivity distribution and the reservoir resistivity changes before and after fluid injection, combined with groundwater salinity and other data, the residual oil and gas distribution and the driving fluid flow state are estimated. Let the measured potential data be... Model parameters are expressed as vectors. This means that the three-dimensional subsurface medium is divided into several rectangular elements, each with a fixed resistivity. Appropriate model parameters are found through successive linearization of the objective function and regularized least-squares iteration with inequality constraints, so that the theoretical response obtained from the forward modeling is optimized. The best fit of the measured potential data in the least squares sense. The model parameters at this point serve as the actual parameters of the underground reservoir. Resistivity imaging results, combined with three-dimensional reservoir parameter distribution, are used to study the remaining oil distribution and gas propagation boundary.

[0076] Field measurements utilize a multi-channel array-type high-precision potential measuring instrument, including a high-performance receiving and transmitting system, and other auxiliary equipment. The transmitting system is capable of transmitting ultra-low frequency square wave pulses at multiple frequencies, including 1Hz. The receiver employs pseudo-random coding weak signal detection technology, significantly enhancing its anti-interference capability. All operations of the measurement system are controlled by an external laptop microcomputer. The instrument system used for field measurements can be divided into three main parts: the power supply section, the current transmitting section, and the receiving section. The equipment type and performance parameters are described below:

[0077] 1. Power supply section: The generator is a Japanese Yamaha EF6000 AC / DC generator with a maximum output current of 20 amps; the output voltage is available in two levels: 110 volts and 220 volts.

[0078] 2. ZFL-1000 / 250V10A Current Transmitter: Converts the AC voltage input from the generator into an ultra-low signal output of 1Hz. Its current regulation accuracy is 1%, frequency stability is 0.01%, maximum output current amplitude is 20A, and output signal waveform frequency is 1.0Hz.

[0079] 3. IIID-VEMP-36 Well Inter-well Information Monitoring System: Measures the potential difference between two electrodes at different locations corresponding to the transmitting radio frequency point on the ground. The receiver has a resolution of 1 microvolt, an input impedance of 10 megohms, and a potential measurement accuracy of 0.1%.

[0080] Well-to-surface potential (BPT) imaging involves supplying a high-power current through the well casing to the downhole surface, measuring the potential distribution caused by changes in the electrical properties of the subsurface medium, and studying the resistivity distribution of the subsurface medium. The correlation between formation resistivity changes and fluid saturation is the foundation for BPT measurements to study fracture and residual oil distribution. Compared to well logging, BPT measurement has the advantage of a larger lateral detection area; compared to surface electrical measurement methods, it has the advantages of greater detection depth and higher resolution because the current can be directly supplied to the target layer.

[0081] Based on the relative changes in potential before and after gas injection monitoring, a comprehensive analysis of residual anomalies during and after injection, especially those during the relatively stable period after injection, can indicate the direction of gas injection and the water boundary region. Areas with large anomalies represent the gas injection propulsion region. Based on the location of the anomaly gradient zone, the gas injection region can be qualitatively determined, and after inversion, a quantitative interpretation of the gas injection boundary can be achieved.

[0082] In practical applications, the specific steps for implementing this invention in a single well are as follows: field construction preparation, including field site exploration, fine-tuning of the field observation system according to site conditions, and design for setting up and storing field construction instruments; measurement point layout and wiring, configuration of power supply lines and return electrode lines, line continuity testing, and resistance testing between power supply and return wells; determination of optimized detection parameters for weak signals from the receiver; and receiver repeatability and consistency verification.

[0083] Before construction, the well-to-ground potential imaging technology gas drive front testing team submitted the construction design and communicated with the client's geological engineer. After the construction design was approved, they went to the site for on-site inspection, communicated with relevant technical personnel in the work area about the timing of switching the injection well, identified the person in charge of the well switching in the work area, exchanged contact information, and obtained the signature of the relevant departments in the work area for the construction order.

[0084] Step 1: On-site survey: Observe the terrain, determine the layout of the ground line, and confirm any possible obstacles on the ground. If there are obstacles or elevation differences at the measuring points, they need to be marked in the received signal and adjusted during the calculation.

[0085] Step 2: Throughout the construction process, staff will clearly mark the measuring points and inspect each measuring point. Clear signs will be set up at the construction site.

[0086] Step 3: On-site equipment debugging; Connect the transmitter to the wellhead casing, powered by a generator. Place the transmitter 20 meters away from the wellhead and run the remote electrode line to an oil / water well 1500 meters away in any direction. Record the well number, connect another line to the well being logged, and use a multimeter to measure the resistance value to check the integrity of the line. Connect the receiver to the logging line, and according to the power strength of the transmitter, detect the changes in the received signal at each logging point, and debug the receiver.

[0087] Step 4: Along the horizontal wellbore trajectory, establish a survey network at the projection points on the ground. Use a theodolite and compass to locate and measure the projection points, then draw the wellbore trajectory line (fishbone line). Along the vertical wellbore trajectory line, set 11 reference common points every 25 meters on both sides of the projection points, totaling 12 points including the electrodes at the projection points. Set approximately 12 small survey lines on each side of the vertical wellbore trajectory line (6 survey points are called (fish rib lines), with a maximum total of 24 lines). Provide insulating tape and short wires, and promptly replace and protect any potentially damaged lines. Report any major issues with the probes and wiring to the project manager immediately, and have a spare set of lines on site. The measurement sequence is as follows: starting from the wellhead, the first line is taken; facing away from the wellhead and towards the bottom of the well, the left side is measured first, followed by the right side; 12 fish rib lines are monitored on each side of the wellbore trajectory line (fish rib line); the projection point of each layer is set as a common reference point; each fish rib line has 6 measurement points, with an interval of 50 meters and a length of 300 meters; the interval between each fish rib line is 25 meters.

[0088] Step 5: Measurement. Test each test line separately. The test procedures and methods are as follows:

[0089] Along the wellbore trajectory line, using the projection point as the test base point, nine reference electrodes are set at 25-meter intervals on both sides of the projection point: four closer to the wellbore and five closer to the bottom of the well, totaling ten electrodes including the one at the projection point. The measurement sequence is as follows: first, measure the left side lines 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, then measure the right side after each line is completed. The test sequence for the right side is: -10, -9, -8, -7, -6, -5, -4, -3, -2, -1. A total of 6 × 20 = 120 measurement points are established using the wiring method, with five sets of continuous and stable data collected for each line. The projection point is on the fifth line from the left, with five lines (125 meters) along the bottom of the well and four lines (100 meters) along the wellhead. Six points are monitored along each line.

[0090] Step 6: If there are obstacles or elevation differences at the detection point, move it to the nearest available location and record the findings; any discrepancies between the detection point and the ideal detection point should also be recorded.

[0091] Step 7: For any work not completed at night, a designated person shall be assigned to guard the site.

[0092] Step 8: Obtain electrical signal data, protected by dual hard drives.

[0093] Step 9: After construction is completed, collect the construction lines in sequence and place them on the construction vehicle; clean up the site and move on to the next construction site.

[0094] On-site electricity use is divided into construction electricity and domestic electricity, and ensuring its safety depends on the management of power lines. Power lines that meet safety requirements must be erected. Temporary overhead lines must be at a safe height, and damaged or aging wires must not be used. Temporary wiring is also prohibited. The wiring and installation of distribution boxes and sockets must comply with safety regulations. On-site building materials should be neatly arranged, and the placement of flammable and explosive materials must comply with safety regulations. After the completion of each construction process, waste materials should be promptly removed from the construction site, and safety signs should be posted on electrical equipment and in designated areas.

[0095] In practical applications, taking the Huping 42-31 well as an example, the basic measurement design is as follows: the planar distribution of measurement points for a single well / subsequent measurement is shown in the test wiring diagram. Figure 2 As shown in the diagram. Centered on the detection projection point (blue dot) of the measured well, N perpendicular projection lines (fishbone lines) are set to the surface of the horizontal wellbore. The spacing between each line (fishbone line) is the same length (50 meters). Each line (fishbone line) is perpendicular to the projection of the horizontal wellbore trajectory onto the ground (fishbone line). Each line shares a common reference electrode (blue dot). The return electrode is selected from an adjacent well approximately 1200-1500 meters away from the measured well.

[0096] Measuring point locations: Perforation fracturing section 2 (2057~2146m), section 4 (1888~1940m).

[0097] Projection point location: Section 2: (2057~2146m): Azimuth 115.7 degrees, displacement 410 meters.

[0098] Section 4 (1888~1940m): Azimuth 116.3 degrees, displacement 220 meters.

[0099] According to the basic principles of well-to-surface potential technology, after the injection of deoxygenated air, the crude oil is displaced and migrates. The difference in resistivity on both sides of the oil-water interface will cause changes in the surface monitoring potential. The direction of the increased potential indicates the location of the reservoir; the direction of the decreased potential indicates the location of the reservoir reflux.

[0100] The monitoring target is the gas injection well Huping 42-31, and the receiving wells are Huping 41-31, Huping 41-3, Huping 40-31, Huping 44-3, Huping 44-21, etc. Figure 3 As shown.

[0101] This well involves gas injection into the perforated section. Based on the principle of well-to-surface potential monitoring, potential data can directly indicate the direction of abnormal underground gas and show the static distribution of underground gas. If the resistivity of the injected gas is higher than that of the formation water, the potential value after gas injection will decrease; if the resistivity of the injected gas is lower than that of the formation water, the potential value after gas injection will increase. Monitoring was conducted on the second section (2057~2146m) and the fourth section (1888~1940m) of the newly perforated fracturing section of the Huping 42-31 well before perforation and one month after normal gas injection. Field monitoring data were obtained, and these data were processed and interpreted to explain the gas injection water drive front.

[0102] Figure 4 and Figure 6 The data shows that during the first month of gas injection, the main directions of gas injection were north and south. The higher potential at measuring points 50m to 150m along measuring line 5 likely indicates the main direction of gas injection; similarly, the higher potential at measuring points -50m to -150m along measuring line 6 also suggests a similar direction. The injected gas diffused uniformly throughout the measuring area.

[0103] Analysis suggests that the main gas transport routes are located at the measuring points 50m to 100m along measuring line 5 and at the measuring points -50m to -100m along measuring line 6.

[0104] Figure 7 and Figure 9 The data shows that during the first month of gas injection, the main directions of gas injection were northeast and southwest. The high potential at the measuring points between -50m and -100m on measuring line 2 likely indicates the main direction of gas injection; the high potential at the measuring points between 50m and 100m on measuring line 4 likely indicates the main direction of gas injection; the high potential at the measuring points between 50m and 100m on measuring line 6 likely indicates the main direction of gas injection; and the high potential at the measuring points between -50m and -100m on measuring lines 7 and 8 likely indicates the main direction of gas injection.

[0105] The inversion of potential monitoring data involves setting N perpendicular projection lines (fishbone lines) on the surface of the horizontal wellbore, centered on the detection projection point (blue dot) of the measured well. Each measurement line (fishbone line) is spaced at a uniform length (50 meters) and is perpendicular to the projection of the horizontal wellbore trajectory onto the ground (fishbone line). Each measurement line shares a common reference electrode (blue dot). The return electrode is selected in an adjacent well approximately 1200-1500 meters away from the measured well. Measurement point locations: Perforated fracturing section 2 (2057~2146m), section 4 (1888~1940m). Projection point locations: Section 2 (2057~2146m): azimuth 115.7 degrees, displacement 410 meters. Section 4 (1888~1940m): azimuth 116.3 degrees, displacement 220 meters.

[0106] Figure 10 and Figure 11 This is the inversion result of the resistivity before perforation. Based on the inversion diagram, the location of the main gas transport channels is determined. Comprehensive analysis suggests that the main gas transport channels are located at measuring points 50m to 100m along survey line 5 and -50m to -100m along survey line 6.

[0107] Figure 12 and Figure 13 The results, combined with the potential contour map and inversion map, show that the location of the main gas transport channels was determined. Comprehensive analysis indicates that the main gas transport channels are located at the 50m to 100m measuring points of survey line 5 and the -50m to -100m measuring points of survey line 6. The well showed significant oil displacement, with gas injection advancing more noticeably in the northern and southern parts of the radius survey area, and more evenly elsewhere. The displacement effect on the external oil-water mixture was more pronounced in the north and south directions.

[0108] Figures 14 to 17 This is a potential contour map. Figure 17 The area covered by the white dashed line represents the range affected by gas injection, while the white arrows indicate the direction of injection. Red indicates maximum potential values, reflecting good permeability or low resistivity of the underground medium. A combined potential inversion map one month after injection shows that, based on the combined potential contour map and the combined inversion map, the second gas transport channel is mainly located in the north and south directions. The injection front advances approximately 100m northward from the perforation projection point and approximately -150m southward. The fourth gas transport channel is mainly located in the northeast and southwest directions. The injection front advances approximately 50m southward from 50m to 100m northeastward and from -50m to -100m southwestward. The gas injection displacement effect is significant, reaching as far as +100m and -150m from the fishbone line.

[0109] The two perforated fracturing sections monitored in this study yielded high-quality raw electrical resistivity tomography (EPT) data. After data processing, the electrical structure was clear, effectively reflecting the electrical changes caused by the gas injection boundary. The potential anomaly map after gas injection monitoring showed that the second section had better gas injection performance, while the fourth section had the best. Analysis of the potential line plot, potential anomaly contour map, and resistivity inversion map revealed the main injection directions: Section 2: North-southwest; Section 4: Northeast-southwest. This had an impact on Huping 42-41 and Huping 42-21, as the resistivity of these two wells was significantly reduced in the inversion map.

[0110] In summary, the air-driven leading edge monitoring method and system of the present invention have the following beneficial effects:

[0111] 1. By using well-to-surface potential imaging technology and adopting appropriate monitoring processes, effective data information was obtained. Through inversion technology, this data was processed and interpreted to obtain the answers that reservoir engineers wanted, providing effective support and basis for the rational regulation of well opening and closing systems and process measures.

[0112] 2. By comparing the results before and after injection, and combining the inversion results map, the affected wells in the surrounding areas were indicated in layers. This explained the reservoir heterogeneity, the connectivity of the main injection channel of the oil layer, and the injection-production effect relationship during the gas drive development process in different orientations. It also showed the abrupt change zone in different orientations, indicated the injection affected area, and indicated the unaffected areas of individual wells.

[0113] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A gas front monitoring method applied to horizontal or highly deviated wells, characterized in that, The gas drive front edge monitoring method comprises: Step S1, field construction preparation; Step S2, field exploration, and obvious protection marks are made on the measuring points; Step S3, field equipment debugging; Step S4, measuring lines are laid along the ground projection of the perforated well section, and gas injection testing is performed; Step S5, test data are obtained and saved, and the monitoring is completed; and Step S6, the test data are preprocessed and edited; The step S4 specifically comprises: The projection point is measured and the wellbore trajectory line is drawn by using the theodolite and compass positioning; Eleven reference common points are arranged on both sides of the projection point along the vertical wellbore trajectory line at intervals of 25 meters; Twelve measuring lines are arranged on both sides of the wellbore trajectory line; Nine reference electrodes are arranged on both sides of the projection point along the wellbore trajectory line at intervals of 25 meters; The measuring lines on both sides of the wellbore trajectory line are measured respectively, and 5 groups of continuous stable data are sampled for each measuring line; The gas injection testing is specifically injecting oxygen-reduced air or natural gas; The step S5 further comprises: A rose diagram, a potential diagram and an inversion resistivity diagram are drawn according to the test data; The initial propagation and direction of the injected gas are determined by injection monitoring, and the initial propagation and speed of the injected gas are calculated; The average propagation and speed of the injected gas in the test time interval are calculated by combining different measurement results in different time intervals; The step S6 specifically comprises: The test data are qualitatively analyzed and preliminarily interpreted; Geological and geophysical initial models are established according to geological, logging and geophysical data; Forward simulation and constrained inversion are performed; Logging resistivity calibration of the inversion result is performed; Water saturation is calculated by using the inversion resistivity result in combination with porosity and formation water resistivity parameters; Residual oil distribution and gas propagation boundary are studied by using the resistivity imaging result in combination with three-dimensional reservoir parameter distribution.

2. The gas drive front monitoring method of claim 1, wherein, The step S1 specifically comprises: The field construction site is explored, and field observation system fine tuning, field construction instrument setting and storage design are performed according to the field conditions; Measuring point arrangement and measuring point wiring, power supply line and return electrode line configuration, line continuity test, power supply and return well resistance test are performed; Optimized detection parameters of the receiver weak signal are determined; and The repeatability and consistency of the receiver are checked.

3. The gas drive front monitoring method of claim 1, wherein, The step S2 specifically comprises: The ground line arrangement is determined by observing the topography, and possible obstacles on the ground are confirmed, if there are obstacles and elevation differences at the measuring points, the obstacles and elevation differences are marked in the received signal, and the received signal is adjusted during calculation; and During the whole construction process, the staff makes obvious protection marks on the measuring points, and inspects each measuring point, and obvious marks are set on the construction site.

4. The gas drive front monitoring method of claim 1, wherein, The step S3 specifically comprises: The transmitter is connected with the wellhead casing, and the power supply is provided by the generator; A return loop is placed 20 meters away from the wellhead, and a lead wire is connected to an oil-water well in any direction, the return electrode well and the monitoring well are more than the depth of the target layer apart; The well number is noted, a line is connected to the measured well, and the resistance value is measured by a multimeter to check whether the line is intact; and The receiver is connected with the measuring line, the change of the received signal of each measuring point is detected according to the strength of the transmitter power supply, and the receiver is debugged.

5. The gas drive front monitoring method of claim 1, wherein, The order of the measuring lines is: The first one is from the wellhead direction; Face to the well bottom, first measure the left side, then the right side; Each side of the wellbore trajectory line is monitored in turn by 12 measuring lines; Each layer projection point is set as a common reference point; Each measuring line has 6 measuring points with an interval distance of 50 meters and a length of 300 meters; The interval between each measuring line is 25 meters.

Images