A method for identifying water invasion channels in a tight sand gas reservoir

Abstract

The embodiment of the application provides a method for identifying water invasion channels in a tight sand gas reservoir, comprising: obtaining natural seismic data and reflection seismic data; performing tomographic inversion based on the natural seismic data to obtain a coarse grid velocity field model of a target region; performing interpolation processing on the coarse grid velocity field model based on the reflection seismic data to obtain a joint velocity field model; performing compaction correction on the velocity in the joint velocity field model according to structural elevation to obtain a corrected joint velocity field model; determining a water invasion identification index based on the corrected joint velocity field model of an adjacent development stage; and determining a water invasion channel according to the geological zoning of the target region and the water invasion identification index. The application can improve the accuracy and integrity of identifying water invasion channels.

Description

Technical Field

[0001] This application relates to the field of oil and gas field development technology, and in particular to a method for identifying water intrusion channels in tight sandstone gas reservoirs. Background Technology

[0002] Tight sandstone gas reservoirs are natural gas reservoirs in clastic rock formations characterized by low porosity, low permeability, and low gas saturation. The gas-water relationship within the reservoir is complex, and the gas and water occurrence states within the formation are diverse. As development progresses, water intrusion occurs in the reservoir, leading to a decrease in gas well production and a sudden increase in water production. To accurately grasp the dynamics of water intrusion, various professional methods are generally employed, including single-well production dynamic analysis, formation water chemical analysis and tracer tracking, static interpretation of fault structures, single-phase natural earthquake tomography, and microseismic dynamic monitoring. Each method has certain limitations and can only qualitatively identify simple water intrusion phenomena. Summary of the Invention

[0003] In view of this, the purpose of this application is to propose a method for identifying water intrusion channels in tight sandstone gas reservoirs.

[0004] Based on the above objectives, this application provides a method for identifying water intrusion channels in tight sandstone gas reservoirs, including:

[0005] Acquire natural earthquake data and reflection earthquake data; Based on the natural earthquake data, a tomographic inversion was performed to obtain a coarse-grid velocity field model of the target area; Based on the reflected seismic data, the coarse-grid velocity field model is interpolated to obtain a joint velocity field model; The velocity in the joint velocity field model is compacted and corrected according to the constructed elevation to obtain the corrected joint velocity field model. Based on the corrected joint velocity field model of adjacent development stages, the water intrusion identification index is determined. Based on the geological zoning of the target area and the aforementioned water intrusion identification indicators, the water intrusion channels are determined.

[0006] Optionally, the reflected seismic data includes a vertical sequence stratigraphic framework; Based on the reflected seismic data, the coarse-grid velocity field model is interpolated to obtain a joint velocity field model, including: Based on the longitudinal sequence stratigraphic framework, the coarse network velocity field model is divided into multiple strata, and velocity continuity constraints are set at the boundaries between adjacent strata; wherein, the multiple strata include upper strata, lower strata and middle strata; Based on the velocity of the corresponding middle strata in the coarse-grid velocity field model, interpolation is performed using the Kriging interpolation method. Based on the velocities of the upper and lower strata in the coarse-grid velocity field model, interpolation is performed using a linear interpolation method.

[0007] Optionally, the method for performing compaction correction on the velocity in the joint velocity field model based on the constructed elevation to obtain the corrected joint velocity field model is as follows: V p，corr,t = V p,raw,t -αH (3) V s，corr,t = V s,raw,t -βH (4) in, α、β This is the compaction correction coefficient for the target area. H To construct the elevation; V p,raw,t For development window t The P-wave velocity field in the joint velocity field model, V s,raw,t For development window t The transverse wave velocity field in the joint velocity field model; V p，corr,t For development window t The corrected longitudinal wave velocity field, V s，corr,t For development window t The corrected transverse wave velocity field.

[0008] Optionally, the method for determining the water intrusion identification index based on the corrected joint velocity field model of adjacent development stages is as follows: (7) (8) (9) in, The rate of change of the ratio of P-wave to S-wave velocity; , respectively development window t2 , t1 The corrected P-wave velocity field at the corresponding coordinate positions represents the P-wave velocity value. , respectively development window t2 , t1 The corrected transverse wave velocity field is the transverse wave velocity value at the corresponding coordinate position.

[0009] Optionally, determining the water intrusion channel based on the geological zoning of the target area and the water intrusion identification index includes: Within the same geological zone, the area where the potential dominant water intrusion channel is located is identified; wherein the rate of change of the P-wave velocity ratio in the area where the potential dominant water intrusion channel is located is positive and is a predetermined multiple of the rate of change of the P-wave velocity ratio in the surrounding area.

[0010] Optionally, the method further includes: Based on the corrected joint velocity field model, areas where the density of microseismic events per unit square kilometer is greater than a preset high-density threshold are identified, and these areas overlap with the areas where the potential dominant water intrusion channels are located. The areas with multiple water-flooded wells in the overlapping areas are designated as the main water intrusion channels. The predetermined multiple is 1.25, and the water-flooded wells are wells whose water geomorphology indicators and / or production dynamic data meet preset abnormal conditions.

[0011] Optionally, the method further includes: Based on the corrected joint velocity field model, the region where the density of microseismic events per unit square kilometer is in the preset medium density range is determined, and the region that overlaps with the region where the potential dominant water intrusion channel is located is identified. The region in the overlapping region where there is a single well with slight water exposure is identified as a secondary water intrusion channel; wherein, the predetermined multiple is 1.1.

[0012] Optionally, the method further includes: The contour lines where the rate of change of the P-wave / S-wave velocity ratio is 0 are used as the initial water intrusion front boundary.

[0013] Optionally, the method further includes: Based on the initial water intrusion front boundary, along the direction of water intrusion advance, the spatial location where the density of microseismic events within a unit square kilometer suddenly decreases from the first value to the second value is the corrected water intrusion front.

[0014] Optionally, the method further includes: when , ,and At that time, it was determined that only compaction occurred; when At that time, it was determined that there was formation water intrusion and fluid replacement.

[0015] As can be seen from the above, the method for identifying water intrusion channels in tight sandstone gas reservoirs provided in this application acquires natural earthquake data and reflection seismic data. Based on the natural earthquake data, tomographic inversion is performed to obtain a coarse-grid velocity field model of the target area. Based on the reflection seismic data, the coarse-grid velocity field model is interpolated to obtain a joint velocity field model. The velocities in the joint velocity field model are compacted and corrected according to the tectonic elevation to obtain a corrected joint velocity field model. Based on the corrected joint velocity field model of adjacent development stages, water intrusion identification indicators are determined. Based on the geological zoning of the target area and the water intrusion identification indicators, water intrusion channels are identified. This application can improve the accuracy and completeness of water intrusion channel identification. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the method flow of an embodiment of this application; Figure 2 This is a schematic diagram illustrating the changes in indicators during the first development stage of a specific embodiment of this application. Figure 3 This is a schematic diagram illustrating the changes in indicators during the second development stage of a specific embodiment of this application. Figure 4 This is a plan view of the microseismic events in the study area according to a specific embodiment of this application; Figure 5 This is a plan view of microseismic events on the northern wing of the study area according to a specific embodiment of this application; Figure 6 This is a schematic diagram of a microseismic profile of the southern wing of the study area according to a specific embodiment of this application; Figure 7A , 7B This is a schematic diagram of different drilling water type geochemical indicators in a specific embodiment of this application; Figure 8 This is a schematic diagram of the planar distribution of the water intrusion channel according to a specific embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0019] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] In related technologies, several methods for identifying water intrusion in tight sandstone gas reservoirs are generally analyzed independently. Each method has certain limitations, only able to qualitatively identify simple water intrusion phenomena and unable to distinguish water intrusion channels with different causes. For example, single-well production dynamic analysis methods can only achieve qualitative evaluation of a single point in the wellbore, lacking the ability to depict inter-well planar water intrusion paths and multi-channel spatial distribution; formation water chemical analysis and tracer tracking methods can only determine the source of water in a single well and qualitatively identify inter-well fluid connectivity, but cannot depict continuous planar water intrusion channels throughout the entire area; single-period natural earthquake tomography has weak vertical stratification capabilities and insufficient accuracy in velocity inversion of thin reservoir sections, failing to finely depict velocity differences within the reservoir; all these methods are unable to effectively distinguish conventional fracture-type water intrusion channels where edge and bottom water advances along primary high-angle fractures in the reservoir, as well as secondary fault channeling channels formed by activated strike-slip fractures under production pressure disturbances, connecting deep formation fluids.

[0021] In the Kuqa Bashkichik Formation fracture-pore type ultra-deep tight sandstone gas reservoir scenario, the reservoir is buried at a depth of over 6000m, with extremely strong formation compaction. The degree of compaction varies significantly at different structural elevations, with deeper and stronger compaction at lower structural elevations. Both formation compaction and formation water intrusion alter elastic parameters such as P-wave velocity, S-wave velocity, and the P-S / S-wave velocity ratio. Relying solely on a single seismic elastic parameter for water intrusion interpretation results in highly ambiguous interpretations. Conventional techniques cannot quantitatively isolate the interference of compaction or accurately extract formation water intrusion characteristic signals. Furthermore, the block's structure is elongated and strip-shaped, with significant differences in structural undulation and fracture development between the east-west and north-south flanks. This leads to significant differences in water intrusion propagation speed and the location of the water intrusion front. Conventional techniques struggle to quantitatively characterize the differentiated water intrusion front boundaries in different directions and flanks, resulting in a lack of refined quantitative geological basis for on-site water control, production restriction, and channel closure development measures, thus limiting the effectiveness of water management and gas stabilization.

[0022] In view of this, the embodiments of this application provide a method for identifying water intrusion channels in tight sandstone gas reservoirs. Based on natural earthquake data and reflection seismic data, a high-resolution joint velocity field model is constructed. Combined with microseismic monitoring data, single-well production dynamics, and formation water geochemical detection data, the dominant water intrusion channels in the gas reservoir development process are quantitatively characterized, effectively distinguishing water intrusion channels of different origins and improving the accuracy and completeness of water intrusion channel identification.

[0023] The technical solution of this application will be further described in detail below through specific embodiments.

[0024] like Figure 1 As shown in the embodiment of this application, a method for identifying water intrusion channels in tight sandstone gas reservoirs is provided, including: S101: Acquire natural earthquake data and reflection earthquake data; In this embodiment, natural earthquake data, reflection earthquake data, whole-well production dynamic data, microseismic monitoring data, formation water geochemical detection data, etc., of the target area are collected, and preprocessing such as noise reduction and cleaning is performed on various types of data to obtain preprocessed data.

[0025] The natural earthquake data includes multi-period natural earthquake catalogs and phase reports, specifically including the time of occurrence, epicenter, focal depth, and first arrival P-wave / S-wave travel times for each natural earthquake. The reflection earthquake data includes static reflection seismic interpretation results, specifically including reflection seismic profiles obtained from artificial shot acquisitions, structural elevation contour lines, fault geometry interpreted from reflection seismic data, and longitudinal sequence stratigraphic framework. The whole-well production dynamics data includes daily gas production from a single well. Q g Daily water production Q w Formation pressure P p Formation water chloride concentration C CL- Time to water exposure, water-to-air ratio R wg = Q w / Q g Etc. Microseismic monitoring data includes the plane coordinates, occurrence time, and energy of microseismic events. Formation water geochemical detection data includes the ionic composition and mineralization of formation water in different development stages and well areas.

[0026] In some methods, for natural earthquake data and reflection earthquake data, all vibration data during drilling, fracturing, and downhole maintenance periods are removed to avoid the impact of engineering noise. For microseismic monitoring data, by matching the spatiotemporal coordinates of the natural earthquake catalog, microseismic data that coincides with natural earthquakes caused by crustal structure are removed based on parameters such as the specific time and geographical location of the earthquake event. At the same time, original microseismic data of fluid migration and fault activation with energy greater than a certain energy threshold are retained, while minor vibration data caused by instrument noise are removed.

[0027] S102: Based on natural earthquake data, tomographic inversion is performed to obtain a coarse-grid velocity field model of the target area; In this embodiment, based on natural earthquake data, a coarse-grid velocity field model of the target area is established using the tomographic velocity inversion modeling method. The coarse-grid velocity field model includes the P-wave velocity field and the S-wave velocity field. Natural earthquake data from different periods can be used to construct coarse-grid velocity field models for different periods, reflecting the P-wave velocity field and S-wave velocity field at different times.

[0028] S103: Based on reflection seismic data, the coarse-grid velocity field model is interpolated to obtain a joint velocity field model; In this embodiment, considering the limited accuracy of the coarse-grid velocity field model constructed based on natural earthquake data, the coarse-grid velocity field model is subjected to longitudinal fine interpolation by combining the longitudinal sequence stratigraphic framework in the reflection seismic data to obtain a joint velocity field model, thereby improving the longitudinal resolution of the reservoir section.

[0029] In some implementations, a joint velocity field model is obtained by interpolating the coarse-grid velocity field model based on reflection seismic data, including: Based on the vertical sequence stratigraphic framework, the coarse network velocity field model is divided into multiple strata, and velocity continuity constraints are set at the boundaries between adjacent strata; among them, multiple strata include upper strata, lower strata and middle strata; Based on the velocities of the corresponding middle-layer strata in the coarse-grid velocity field model, the Kriging interpolation method is used for interpolation; Based on the velocities of the upper and lower strata in the coarse-grid velocity field model, a linear interpolation method is used for interpolation.

[0030] In this embodiment, based on the coarse-grid velocity field model, and combined with the longitudinal sequence stratigraphic framework obtained from reflection seismic interpretation, the coarse-grid velocity field model is divided into multiple strata. Velocity interpolation is performed on each of the divided strata. During the interpolation process, velocity continuity constraints are applied to the boundaries between adjacent strata to avoid distortion caused by abrupt changes in boundary velocity.

[0031] In some approaches, the velocity of the joint velocity field model can be expressed as: Vp，raw,t = F interp [V p,raw (t),Z top ,Z bot ,Z int ] (1) V s，raw,t = F interp [V s,raw (t),Z top ,Z bot ,Z int ] (2) in, F interp For the vertical sequence stratigraphic framework constraint, the interpolation function is... V p,raw (t), V s,raw (t) In the coarse-grid velocity field model, the development window is respectively... t Longitudinal wave velocity field, transverse wave velocity field; V p，raw,t 、V s，raw,t Develop time windows for the joint velocity field model t Longitudinal wave velocity field, transverse wave velocity field; Z top The depth of the top interface of the Bashkichik Formation. Z bot The depth of the bottom interface of the Bashkichik Formation. Z int This refers to the depth of the internal stratification interface within the reservoir. There can be multiple internal strata, depending on the formation thickness. If the formation is thick and has significant internal structural deformation, there can be multiple strata. If the formation is relatively flat and the formation thickness does not vary much, there can be only one stratum.

[0032] In some approaches, the Kriging interpolation method is used for velocity interpolation in the Bashkichik Formation reservoir, while the linear interpolation method is used for velocity interpolation in the upper strata above the top of the Bashkichik Formation and the lower strata below the bottom of the Bashkichik Formation. By performing independent interpolation on the three strata, and using continuous velocity constraints on the top and bottom interfaces of the Bashkichik Formation, a joint velocity field model is constructed that takes into account both the long-term evolution of strata mining velocity and the fine vertical resolution of the reservoir, based on preserving the dynamic changes in mining velocity captured by natural earthquakes over many years and combining vertical interpolation with the vertical stratification framework of reflection seismic data.

[0033] In some approaches, modeling software such as Petrel, GeoMap, and Surfer can be used for modeling. The coordinate transformation tools of the modeling software are used to perform unified coordinate transformation based on seismic data. Layer overlay tools are used to match the coordinate positions of the vertical sequence stratigraphic framework data to the corresponding coordinate positions in the coarse-grid velocity field model. The coordinate positions of microseismic events are projected to the corresponding coordinate positions in the coarse-grid velocity field model. The wellhead coordinates and well trajectory vertical depth are matched to the corresponding coordinate positions in the coarse-grid velocity field model. In this way, layered interface constraints and refined interpolation are performed in the coarse-grid velocity field model.

[0034] S104: Compaction correction is performed on the velocity in the joint velocity field model based on the tectonic elevation to obtain the corrected joint velocity field model; In this embodiment, the velocity in the joint velocity field model is compacted and corrected based on the constructed elevation to obtain the corrected joint velocity field model. The correction method is as follows: V p，corr,t = V p,raw,t -αH (3) V s，corr,t = V s,raw,t -βH (4) in, α、β The compaction correction coefficient for the target area is obtained through calibration in an uncompacted zone of a pure gas reservoir. H To construct the elevation, V p，corr,t For development window t The corrected longitudinal wave velocity field, V s，corr,t For development window tThe corrected shear wave velocity field is obtained by performing compaction correction on each P-wave velocity value in the P-wave velocity field of the joint velocity field model. The corrected P-wave velocity field is formed by all the corrected P-wave velocity values. Similarly, the corrected shear wave velocity field is formed by performing compaction correction on each shear wave velocity value in the joint velocity field model. The corrected P-wave velocity field and the shear wave velocity field together form the corrected joint velocity field model. By using a quantized compaction correction formula to correct seismic elastic parameters, interference from ultra-deep compaction signals can be reduced.

[0035] Based on the corrected P-wave velocity field and S-wave velocity field, the corrected P-wave / S-wave velocity ratio is calculated: (5) Or it can be expressed as: (6) in, For development window t The corrected P-wave velocity field and the P-wave velocity field at the corresponding coordinate position (x, y, z) P-wave velocity values With transverse wave velocity value The ratio of longitudinal to transverse wave velocities.

[0036] S105: Determine water intrusion identification indicators based on the corrected joint velocity field model of adjacent development stages; In this embodiment, corrected joint velocity field models for different development stages are established according to the above method, such as corrected joint velocity field models for the early, middle, and late stages of development. Based on the corrected joint velocity field models of two adjacent development stages, water intrusion identification indicators are determined. The method is as follows: (7) (8) (9) Or it can be expressed as: (10) (11) (12) in, Let be the rate of change of the ratio of P-wave velocity to S-wave velocity at coordinate position (x, y, z). , respectively development window t2 , t1 The corrected P-wave velocity field is the P-wave velocity value at coordinate position (x,y,z). , (x, y, z) represent the development window. t2 , t1 The corrected shear wave velocity field is the shear wave velocity value at coordinate position (x, y, z). Let be the change in the longitudinal wave velocity field at coordinate position (x, y, z). This represents the change in the transverse wave velocity field at coordinate position (x, y, z). Development window. t1 Corresponding to the first development stage, development window t2 corresponds to the second development stage, and the first development stage is earlier than the second development stage.

[0037] S106: Determine the water intrusion channels based on the geological zoning and water intrusion identification indicators of the target area.

[0038] In this embodiment, based on reflection seismic data, the target area is divided into multiple geological zones according to structural elevation, with the compaction intensity of each geological zone decreasing progressively. Specifically, a three-dimensional reflection seismic structural surface is constructed based on the reflection seismic data. A structural elevation planar grid of the top interface of the Bashkichik Formation reservoir is extracted from the three-dimensional reflection seismic structural surface. This planar grid has undergone unified coordinate transformation, and each grid point has a corresponding reservoir top surface elevation value. A structural elevation histogram is plotted, and data distribution inflection points are determined based on the elevation histogram. Multiple elevation boundary values ​​are set based on these inflection points, and the planar grid is divided into multiple geological zones based on these elevation boundary values. For example, setting two elevation boundary values ​​can divide the planar grid into three geological zones. Then, the wellhead coordinates are projected onto the planar grid, and the structural elevation of the reservoir top interface corresponding to each well is read to verify that the key well falls within the corresponding geological zone.

[0039] In the Kuqa Bashkichik Formation fracture-pore type ultra-deep tight sandstone gas reservoir scenario, it is divided into three geological zones from west to east: the western low-lying zone with the highest compaction intensity (including wells KS8-11 to KS805), the moderately compacted transition zone (including wells KS8-5 to KS8004 to KS8-2), and the eastern high-lying zone with the weakest compaction intensity (including wells KS8003 to KS8-10). The elastic evolution patterns of the three geological zones are analyzed using water intrusion identification indicators. Specifically, for the western low-lying zone, the change in the P-wave velocity field... The change in transverse wave velocity field is initially negative and then positive. The rate of change of the P-wave / S-wave velocity ratio is initially negative and then approaches zero. Initially slightly negative, then consistently positive; for the middle transition region, the change in the P-wave velocity field... The change in the transverse wave velocity field is positive throughout. The rate of change of the P-wave velocity ratio is initially negative and then slightly positive. The value remains positive; for the eastern high-altitude region, the change in the P-wave velocity field... The initial value approaches 0, and the subsequent value increases positively, indicating the change in the shear wave velocity field. Fluctuating slightly between positive and negative values, the rate of change of the P-wave velocity ratio... It continues to rise.

[0040] In some embodiments, compaction and formation water intrusion fluid replacement are determined based on water intrusion identification indicators. Specifically, when the change in the P-wave velocity field... Change in transverse wave velocity field And the rate of change of the P-wave / S-wave velocity ratio At that time, it was determined that only compaction occurred. When the rate of change of the longitudinal and transverse wave velocities... At that time, it was determined that formation water intrusion and fluid replacement were present. Combined with quantitative analysis of water intrusion identification indicators, it can solve the problems of superposition and confusion between strong compaction and formation water fluid replacement signals in ultra-deep dense sandstone, multiple interpretations of elastic parameters, and the inability to quantitatively remove compaction interference.

[0041] In some embodiments, water intrusion channels are determined based on the geological zoning of the target area and calculated water intrusion identification indicators, including: Within the same geological zone, the areas where potential dominant water intrusion channels are located are identified; wherein, the rate of change of the P-wave velocity ratio in the area where the potential dominant water intrusion channel is located is positive and is a predetermined multiple of the rate of change of the P-wave velocity ratio in the surrounding area.

[0042] In this embodiment, water intrusion channels are initially identified by combining water intrusion identification indicators. Within the same geological zone, strip areas with a positive rate of change in the P-wave and S-wave velocity ratio, which are predetermined multiples of the rate of change in the P-wave and S-wave velocity ratio of the surrounding area, are identified as potential advantageous water intrusion channels. The accuracy of preliminary identification of water intrusion channels by using quantitative water intrusion identification indicators is improved by more than 70%.

[0043] Based on the initial identification of potential water intrusion channels, and by further combining multi-source data such as whole-well production dynamics data, microseismic monitoring data, and formation water geochemical detection data, the water intrusion channels were determined, specifically: In some methods, based on the corrected joint velocity field model, areas where the density of microseismic events per unit square kilometer is greater than a preset high-density threshold are identified, and these areas overlap with the areas where potential dominant water intrusion channels are located. The areas with multiple water-flooded wells in the overlapping areas are designated as the main water intrusion channels. Among these, the rate of change of the P-wave and S-wave velocity ratio in the area where the potential dominant water intrusion channel is located is 1.25 times the rate of change of the P-wave and S-wave velocity ratio in the surrounding areas. Water-flooded wells are those whose water geomorphology indicators and / or production dynamic data meet preset anomaly conditions.

[0044] Optionally, the formation water chloride concentration in the water-flooded well exceeds a preset abnormal threshold; for example, multiple wells meeting this threshold... C CL->5000mg / L, daily water production Q w Continuing to rise, water-to-air ratio R wg The overlapping areas that increase year by year are identified as effective main water intrusion channels.

[0045] In other methods, based on the corrected joint velocity field model, regions where the density of microseismic events per unit square kilometer is in the preset medium density range are identified, and these regions overlap with the regions where potential dominant water intrusion channels are located. The regions where a single well with slight water seepage exists are designated as secondary water intrusion channels. The rate of change of the P-wave velocity ratio in the region where the potential dominant water intrusion channel is located is 1.1 times that of the surrounding region.

[0046] In some implementation methods, the density of microseismic events per unit square kilometer is: (13) In the formula, This represents the total number of microseismic events within the model's grid. The grid area is expressed in km². 2 Optionally, the high-density threshold can be set to 30 per square kilometer, i.e., when... >30 units / km 2 When an area is identified as a high-density microseismic event zone, the main water intrusion channel can be determined by combining data on potential dominant water intrusion channels and formation water geochemical detection. The medium-density range can be set at 10-30 channels per square kilometer. units / km 2 When an area is identified as a medium-density microseismic event zone, secondary fracture seepage channels can be determined by combining well water seepage data; the low-density threshold can be set to 10 per square kilometer, i.e., when... 10 units / km 2 At that time, it was determined to be a low-density microseismic event area, belonging to a dense matrix slow seepage zone.

[0047] In some methods, microseismic monitoring data can be combined to analyze the spatiotemporal migration patterns of microseisms and the dynamic expansion process of water intrusion. Specifically, microseisms migrate from west to east along faults, while lateral and subsurface water flows from west to east along the main water intrusion path of the fractures; microseisms migrate bidirectionally from east to west and from north to south along strike-slip faults. Strike-slip faults are activated by mining pressure, posing a risk of secondary flow of deep fluids, thus filling the gap in early warning of large-scale deep fluid intrusion risks.

[0048] In some cases, if the ion composition and mineralization of the well water in a water-flooded well differ significantly between the later and early stages of development within the same strike-slip fault zone, and there is bidirectional migration due to microseismic events, it can be determined that the fault is conducting deep formation fluids, forming a secondary water intrusion channel.

[0049] In some embodiments, the method further includes using contour lines with a rate of change of 0 for the P-wave / S-wave velocity ratio as the initial water intrusion front boundary. Based on the identification of the initial water intrusion front boundary, the initial water intrusion front boundary is corrected using microseismic monitoring data; specifically, the density of microseismic events per unit square kilometer along the direction of water intrusion advance is calculated. The spatial location of a sudden drop in value (e.g., a sudden drop from the first value to the second value) is the corrected water intrusion front.

[0050] In the scenario of fracture-pore type ultra-deep tight sandstone gas reservoir in the Kuqa Bashkichik Formation, the research example is a complete whole extending in a near east-west direction anticline structure. The part dipping to the north is called the north wing, and the part dipping to the south is called the south wing. The water intrusion front can be distinguished according to the difference in the distribution of microseismic events on the north and south wings. For example, the south wing front is biased to the west (east of KS805), and the north wing has a bidirectional water intrusion front close to well KS8-3.

[0051] In one specific embodiment, in the scenario of a fracture-pore type ultra-deep tight sandstone gas reservoir in the Bashiqichik Formation at a depth of 6400~8200m in the Kuqa foreland mountains, natural earthquake data, reflection seismic data, 5-year well production dynamics, continuous microseismic monitoring data, and formation water geochemical detection data for three periods (e.g., 2017, 2021, and 2025) were collected. Based on the natural earthquake data of each period, tomographic inversion modeling was performed to obtain the corresponding coarse-grid velocity field model. Combined with the vertical sequence stratigraphic framework of the reflection seismic data, the coarse-grid velocity field model of each period was vertically interpolated to obtain the joint velocity field model of each period. The compaction correction formula was used to eliminate the compaction interference in the joint velocity field model to obtain the corrected joint velocity field model of each period. Geological zones were then divided.

[0052] like Figure 2 , 3 As shown, based on the corrected joint velocity field model of two adjacent periods, the water intrusion identification index is calculated according to formula (7)-(9) to obtain the water intrusion identification index of adjacent development stages. According to the water intrusion identification index, the potential dominant water intrusion channel from west to east of KS802-KS805-KS8004 is initially identified; the initial water intrusion front boundary is identified according to the rate of change of the P-wave and S-wave velocity ratio.

[0053] like Figure 4-6 As shown, based on microseismic monitoring data, the density of microseismic events per unit square kilometer was calculated. It was identified that the density of microseismic events in the grid west of KS8004 exceeded the high-density threshold, and the chloride ion concentration in multiple wells exceeded 5000 mg / L, with a daily water production... Q w Continuing to rise, water-to-air ratio R wgIt has been increasing year by year and has been identified as the main water intrusion channel.

[0054] Meanwhile, the bidirectional migration of microseismic activity along the KS806 strike-slip fault indicates a risk of deep fluid cross-flow. Figure 7A , 7B As shown, the difference in salinity between water samples from the later and earlier stages of development and that of conventional edge and bottom water exceeds 20%, indicating a secondary water intrusion channel. Based on the density variation gradient of microseismic events, along the direction of water intrusion advance on both the north and south wings, the spatial location where the density of microseismic events drops sharply per unit square kilometer is taken as the corrected water intrusion front.

[0055] like Figure 8 As shown, by overlaying the fracture map, the planar map of water invasion identification index changes in the two development stages, the density grid map of microseismic events, the historical water flooding zoning map, and the dynamic layer of the whole well, a comprehensive water invasion model map is generated. This comprehensive water invasion model map marks the planar distribution of three types of water invasion channels (Type I, Type II, and Type III), including the main water invasion channels, secondary water invasion channels, and secondary water invasion channels. This can provide a basis for implementing differentiated water control, fracture sealing measures, and well site optimization development work for gas reservoirs, resulting in a 2.1% decrease in the overall gas production decline rate of the block.

[0056] The water intrusion channel identification method for tight sandstone gas reservoirs provided in this application constructs a high-resolution joint velocity field model based on natural earthquake data and reflection seismic data. The velocity field model is corrected using a compaction correction formula to reduce interference from ultra-deep compaction signals. Water intrusion identification indices are calculated based on the corrected joint velocity field model. Potential dominant water intrusion channels and water intrusion fronts are preliminarily identified based on these indices. By integrating microseismic monitoring data, whole-well production dynamic data, and formation water chemistry data, the method accurately identifies primary, secondary, and secondary water intrusion channels and water intrusion fronts. Through mutual constraints among multiple indices, the method significantly reduces interpretability ambiguity and improves the accuracy and completeness of water intrusion channel identification. It has advantages such as low cost, full-area coverage, and strong engineering applicability, and is suitable for water intrusion identification in ultra-deep tight sandstone gas reservoirs of the same type, such as the Kuqa Dabei and Bozi reservoirs.

[0057] It should be noted that the method in this embodiment can be executed by a single device, such as a computer or server. The method can also be applied in a distributed scenario, where multiple devices cooperate to complete the task. In such a distributed scenario, one of these devices may execute only one or more steps of the method in this embodiment, and the multiple devices will interact with each other to complete the method described.

[0058] It should be noted that the above description describes specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims may be performed in a different order than that shown in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this application as described above, which are not provided in the details for the sake of brevity.

[0060] Additionally, to simplify the description and discussion, and to avoid obscuring the embodiments of this application, the well-known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided drawings. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this application, and this also takes into account the fact that the details of the implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this application will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuits) have been set forth to describe exemplary embodiments of this disclosure, it will be apparent to those skilled in the art that the embodiments of this application can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0061] Although this disclosure has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed.

[0062] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this disclosure.

Claims

1. A method for identifying water intrusion channels in tight sandstone gas reservoirs, characterized in that, include: Acquire natural earthquake data and reflection earthquake data; Based on the natural earthquake data, a tomographic inversion was performed to obtain a coarse-grid velocity field model of the target area; Based on the reflected seismic data, the coarse-grid velocity field model is interpolated to obtain a joint velocity field model; The velocity in the joint velocity field model is compacted and corrected according to the constructed elevation to obtain the corrected joint velocity field model. Based on the corrected joint velocity field model of adjacent development stages, the water intrusion identification index is determined. Based on the geological zoning of the target area and the aforementioned water intrusion identification indicators, the water intrusion channels are determined.

2. The method according to claim 1, characterized in that, The reflected seismic data includes a vertical sequence stratigraphic framework; Based on the reflected seismic data, the coarse-grid velocity field model is interpolated to obtain a joint velocity field model, including: Based on the longitudinal sequence stratigraphic framework, the coarse network velocity field model is divided into multiple strata, and velocity continuity constraints are set at the boundaries between adjacent strata; wherein, the multiple strata include upper strata, lower strata and middle strata; Based on the velocity of the corresponding middle strata in the coarse-grid velocity field model, interpolation is performed using the Kriging interpolation method. Based on the velocities of the upper and lower strata in the coarse-grid velocity field model, interpolation is performed using a linear interpolation method.

3. The method according to claim 1, characterized in that, The method for performing compaction correction on the velocities in the combined velocity field model based on the constructed elevation to obtain the corrected combined velocity field model is as follows: V p，corr,t = V p,raw,t -αH （3） V s，corr,t = V s,raw,t -βH （4） in, α、β This is the compaction correction coefficient for the target area. H To construct the elevation; V p,raw,t For development window t The P-wave velocity field in the joint velocity field model, V s,raw,t For development window t The transverse wave velocity field in the joint velocity field model; V p，corr,t For development window t The corrected longitudinal wave velocity field, V s，corr,t For development window t The corrected transverse wave velocity field.

4. The method according to claim 3, characterized in that, The water intrusion identification index is determined based on the corrected joint velocity field model of adjacent development stages, using the following method: （7） （8） （9） in, The rate of change of the ratio of longitudinal to transverse wave velocities; , respectively development window t2 , t1 The corrected P-wave velocity field at the corresponding coordinate positions represents the P-wave velocity value. , respectively development window t2 , t1 The corrected transverse wave velocity field is the transverse wave velocity value at the corresponding coordinate position.

5. The method according to claim 4, characterized in that, The process of determining water intrusion channels based on the geological zoning of the target area and the water intrusion identification indicators includes: Within the same geological zone, the area where the potential dominant water intrusion channel is located is identified; wherein the rate of change of the P-wave velocity ratio in the area where the potential dominant water intrusion channel is located is positive and is a predetermined multiple of the rate of change of the P-wave velocity ratio in the surrounding area.

6. The method according to claim 5, characterized in that, Also includes: Based on the corrected joint velocity field model, areas where the density of microseismic events per unit square kilometer is greater than a preset high-density threshold are identified, and these areas overlap with the areas where the potential dominant water intrusion channels are located. The areas with multiple water-flooded wells in the overlapping areas are designated as the main water intrusion channels. The predetermined multiple is 1.25, and the water-flooded wells are wells whose water geomorphology indicators and / or production dynamic data meet preset abnormal conditions.

7. The method according to claim 5, characterized in that, Also includes: Based on the corrected joint velocity field model, the region where the density of microseismic events per unit square kilometer is in the preset medium density range is determined, and the region that overlaps with the region where the potential dominant water intrusion channel is located is identified. The region in the overlapping region where there is a single well with slight water exposure is identified as a secondary water intrusion channel; wherein, the predetermined multiple is 1.

1.

8. The method according to claim 4, characterized in that, Also includes: The contour lines where the rate of change of the P-wave / S-wave velocity ratio is 0 are used as the initial water intrusion front boundary.

9. The method according to claim 8, characterized in that, Also includes: Based on the initial water intrusion front boundary, along the direction of water intrusion advance, the spatial location where the density of microseismic events within a unit square kilometer suddenly decreases from the first value to the second value is the corrected water intrusion front.

10. The method according to claim 4, characterized in that, Also includes: when , ,and At that time, it was determined that only compaction occurred; when At that time, it was determined that there was formation water intrusion and fluid replacement.

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