A method for dynamically inverting effective fracture conductivity of a fractured well based on multi-modal monitoring data

Abstract

The present application belongs to the technical field of oil and gas field development and hydraulic fracturing, and particularly relates to a dynamic inversion method for effective fracture conductivity of a fractured well based on multi-modal monitoring data. The dynamic inversion method comprises an initial equivalent conductivity determination stage at the end of fracturing operation, an effective conductivity correction stage during flowback, a dynamic effective conductivity inversion stage during production, and a fracture production contribution evaluation stage. The dynamic inversion method continuously links the fracturing operation, flowback and production stages through the fracture conductivity parameter, and realizes the stage-by-stage determination and dynamic inversion of the effective fracture conductivity of the fractured well.

Description

Technical Field

[0001] This invention belongs to the technical field of oil and gas field development and hydraulic fracturing, specifically relating to a dynamic inversion method for the effective fracture conductivity of fracturing wells based on multimodal monitoring data. Background Technology

[0002] With the continuous expansion of low-permeability, ultra-low-permeability, and unconventional oil and gas resource development, hydraulic fracturing has become an important technical means to improve reservoir seepage conditions, establish high-conductivity channels between the reservoir and the wellbore, and increase single-well productivity. During hydraulic fracturing, high-pressure fracturing fluid enters the reservoir and induces rock fracturing, forming hydraulic fractures with a certain length, height, and width. Subsequently, proppant enters the fracture interior with the fracturing fluid and bears the fracture closure load after the pump is stopped, thereby maintaining the flow space and seepage capacity of the fracture.

[0003] Currently, the evaluation of fracturing effectiveness mainly relies on factors such as fracturing pressure, displacement, proppant injection procedure, microseismic monitoring, fracturing simulation, and post-fracturing production data to determine fracture half-length, fracture height, fracture width, fracture modification volume, and fracture network morphology. However, fractures formed during the fracturing phase are not equivalent to those that effectively conduct fluid during the flowback and production phases.

[0004] For multi-stage, multi-cluster hydraulically fractured wells, the proppant placement varies significantly within different fractures due to uneven fluid inflow, competitive fracture propagation, stress interference, and proppant diversion differences among different perforation clusters. Areas near the wellbore typically have higher proppant concentrations, while distal fractures, branch fractures, or secondary fractures may have insufficient proppant placement. During pump shutdown and flowback, insufficiently propped fracture areas may close rapidly as internal pressure decreases. Some fractures formed during fracturing, despite their large geometric dimensions, may contribute little to flow due to insufficient proppant or low connectivity with the wellbore. Therefore, evaluating fracturing effectiveness solely based on fracture length, height, or volumetric alteration primarily addresses the geometry of fractures formed during fracturing and cannot determine the extent to which effective conductivity is maintained within the fractures.

[0005] On the other hand, fracture conductivity is not a fixed parameter that remains constant throughout post-fracturing production. For propped fractures, fracture conductivity is determined by both fracture permeability and fracture width. As post-fracturing flowback and production continue, the internal pressure of the fracture gradually decreases, while the effective normal stress acting on the fracture surface and the proppant skeleton gradually increases. As the effective stress increases, the proppant undergoes compaction, embedding, and particle breakage, causing changes in fracture width and permeability, thus gradually reducing fracture conductivity. Therefore, the fracture conductivity determined at the end of fracturing only characterizes the initial fracture conditions under a specific pressure state and cannot directly represent the actual effective conductivity of the fracture after flowback and during the medium- to long-term production stages.

[0006] CN106353809A discloses a method for inverting and characterizing hydraulic fracturing fracture networks. It uses microseismic data, hydraulic fracturing construction data, and production data to invert the geometric morphology and properties of hydraulic fracturing fracture networks. Its focus is on determining the spatial morphology and related parameters of the hydraulic fracturing fracture network.

[0007] CN112539049A discloses a method for inverting fracturing fracture parameters based on automatic history fitting of production dynamics. This method establishes a fracture model and uses production dynamics for history fitting to correct fracture parameters. Its focus remains on using production dynamics to determine fracture geometry and attribute parameters. While this method can improve the accuracy of fracturing fracture morphology and parameter interpretation, a specific quantitative conversion relationship is still lacking between fractures formed during fracturing operations and those that maintain effective flow conduction after flowback.

[0008] CN117930384B discloses a method for inverting fracture parameters in oil and gas reservoirs based on ion analysis of fracturing flowback fluid. By establishing a complex fracture network flowback model, it fits simulated cumulative oil production, cumulative gas production, cumulative water production, and flowback fluid ion concentration with actual flowback data, and obtains the fracture inversion results at the flowback stage by adjusting fracture parameters. This method demonstrates that the flowback process contains important dynamic information that can constrain fracture parameters. However, once the fracture geometry has been determined during the fracturing operation stage, simultaneously adjusting multiple parameters such as fracture location, fracture width, fracture permeability, and fracture orientation during the flowback stage can easily lead to equivalent compensation between different parameters, thereby increasing the non-uniqueness of the inversion results.

[0009] CN117988837A discloses a method for inverting fracture parameters in fractured horizontal wells. This method obtains data from different stages, including pre-fracturing micro-injection pressure drop testing, segmented fracturing testing during fracturing, and post-fracturing well shut-in and production testing. It further interprets basic and effective fracture parameters, such as fracture half-length and fracture conductivity. This method embodies the idea of ​​jointly constraining fracture parameters based on data from different fracturing stages. However, its primary purpose remains obtaining comprehensive reservoir and fracture parameters. It has not yet established a dynamic inversion relationship centered on the same fracture conductivity parameter, with step-by-step inheritance and continuous correction from the construction stage, flowback stage, to the production stage.

[0010] Furthermore, existing methods for determining the reasonable conductivity of fractures primarily serve fracturing design, determining the reasonable conductivity in a design sense through reservoir parameters, fracture size, and production predictions. Propped long-term conductivity experiments and stress disturbance evaluation methods mainly study the conductivity performance of proppant under different closure stress conditions. These methods show that the conductivity of propped fractures is significantly affected by the proppant placement state and effective stress. However, there are still differences between the proppant conductivity obtained under experimental conditions and the actual effective fracture conductivity in field fracturing wells, requiring further correction based on actual flowback and production dynamics.

[0011] Therefore, existing technologies for fracturing fracture parameter inversion, flowback dynamic interpretation, and evaluation of propped fracture conductivity have at least the following problems: (1) The fracture geometry obtained from the fracturing construction simulation cannot directly represent the actual flow capacity of the effective fracture after flowback, and there is a lack of clear quantitative conversion parameters between the formed fracture and the effective fracture.

[0012] (2) The actual proppant placement inside the crack has obvious spatial non-uniformity. Using the average proppant concentration or simply the average crack conductivity is difficult to accurately reflect the flow bottleneck formed in the low conductivity area.

[0013] (3) During the backflow process, the rapid decrease in crack pressure, the increase in effective stress, and the lack of sufficient support for crack closure will lead to a significant change in crack conductivity. However, existing methods lack the ability to use backflow dynamic quantitative evaluation to assess the actual retention of crack conductivity formed during construction.

[0014] (4) During the production process, the crack pressure changes continuously, and the crack conductivity changes continuously with the effective stress. Using a fixed crack conductivity is difficult to reflect the long-term flow capacity of the crack.

[0015] (5) In multi-stage and multi-cluster fracturing wells, the flowback effectiveness, stress sensitivity and production contribution of different fracture units are different, and the average fracture parameters of the whole well are difficult to identify inefficient fractures and dominant fractures. Summary of the Invention

[0016] The purpose of this invention is to address the shortcomings of existing fracturing fracture evaluation and parameter inversion methods. These methods lack a continuous quantitative conversion relationship between fractures formed during fracturing and those that maintain effective conductivity during the flowback and production stages. Furthermore, the non-uniform proppant distribution and long-term effective stress changes within fractures are difficult to characterize within the same conductivity parameter system. Additionally, there is a lack of reliable alternative correction methods for the effective fracture state under incomplete flowback data, and the problem of excessive fracture parameters to be inverted in multi-stage, multi-cluster fracturing wells easily leads to parameter equivalence compensation and non-uniqueness in inversion. Therefore, this invention provides a dynamic inversion method for the effective conductivity of fracturing wells based on multi-modal monitoring data. This dynamic inversion method continuously links the three stages of fracturing, flowback, and production through fracture conductivity parameters, achieving stage-by-stage determination and dynamic inversion of the effective conductivity of fracturing wells.

[0017] The technical solution of this invention is as follows: A dynamic inversion method for the effective fracture conductivity of fracturing wells based on multimodal monitoring data includes the following steps: (1) Initial equivalent conductivity determination stage at the end of fracturing operation S1. Establish a forward model for fracturing operations based on the geological data, geomechanical parameters, and fracturing operation data of the target well.

[0018] The geological data and geomechanical parameters of the target well include reservoir thickness, porosity, permeability, formation pressure, elastic modulus, Poisson's ratio, maximum horizontal principal stress, minimum horizontal principal stress, and Biot coefficient.

[0019] Fracturing operation data includes operation time and displacement changes. Construction pressure The amount of fracturing fluid injected, the amount of proppant added, the proppant concentration, the type of proppant, and the location of the fracturing section and perforation cluster.

[0020] A forward model for hydraulic fracturing construction, namely a hydraulic fracturing fracture propagation model, is established based on a three-dimensional geological model to simulate the fracture initiation, propagation, and proppant transport process during hydraulic fracturing.

[0021] S2. Using construction pressure, displacement, and fluid volume, historical data are fitted in Kinetix software to determine the spatial distribution morphology of the fracturing fractures. The basic geometric morphology of the fracturing fractures includes fracture length, fracture height, fracture orientation, and the main flow path.

[0022] During fracture propagation, the relationship between the internal fluid pressure and the minimum horizontal principal stress of the reservoir is used to determine whether the fracture meets the conditions for initiation and continued propagation. Furthermore, the dynamic propagation process of fracture length, height, and width is simulated by combining changes in construction pressure and discharge rate. These fracture propagation conditions are used to determine the geometric boundary of the fracture formed during fracturing operations and are not used as freely adjustable parameters for subsequent dynamic inversion of effective conductivity.

[0023] The specific direction of fracture propagation is determined based on the regional geostress state, and the actual spatial distribution direction of the fracture is determined by combining the development of natural fractures, reservoir heterogeneity, and calculation results of the construction model.

[0024] The above calculations yield the spatial distribution of fractures after the fracturing operation. The geometric parameters such as fracture length, fracture height, fracture width, and spatial location are determined using Kinetix simulation results. The fracture spatial model required for subsequent proppant placement calculations is then obtained.

[0025] S3. Due to the significant spatial heterogeneity of actual hydraulic fracturing fracture systems, it is impossible to describe the entire fracture network using a single fracture parameter. Therefore, based on the spatial distribution morphology of hydraulic fracturing fractures, the complex fracture network is divided into multiple fracture inversion units with independent flow characteristics; each fracture inversion unit includes fracture geometry, proppant concentration, initial fracture width, effective closure stress, and initial conductivity.

[0026] The crack inversion unit is represented as: ; in: For the first One crack inversion unit; For the first The first inversion unit A localized crack segment; This represents the number of local cracks contained in the inversion unit.

[0027] The inversion element is determined based on the spatial resolution of the field dynamic data. The inversion element is not a single grid in the crack numerical model, nor is it an independent parameter region that must correspond to all actual cracks. Instead, it is the smallest parameter adjustment region that can be effectively constrained by the field dynamic data.

[0028] When the target well has distributed fiber optic monitoring, production logging, tracer testing, or other segmented dynamic data, the inversion unit can be divided according to fracture clusters or fracture cluster groups.

[0029] When the target well only has whole-well flowback data and conventional production dynamic data, multiple fracture regions that cannot be effectively distinguished by dynamic response are merged, or the fracturing section is used as the inversion unit.

[0030] By using the above methods, the number of inversion parameters is matched with the number of effective constraint information provided by actual dynamic data, thereby reducing the non-uniqueness caused by simultaneous inversion of multiple parameters.

[0031] By discretizing the crack space, the traditional description of crack parameters as a whole is transformed into a description of crack spatial distribution parameters.

[0032] S4. Due to the spatial non-uniformity of proppant placement within actual fractures, after determining the spatial distribution morphology of the fracturing fractures, the initial conductivity of local fracture segments is first determined based on the proppant concentration at different locations and the effective stress in the fracture normal direction. ; in: For the first Within the first inversion unit The initial local flow capacity at the end of construction of a local crack segment; The concentration of proppant applied per unit crack area; The effective stress in the normal direction of the local crack at the end of construction.

[0033] After fracturing, the fracture is subjected to closure, and the proppant gradually bears the closure load. The compression and embedding of proppant particles, as well as changes in the contact state of the fracture wall, all affect the effective width and permeability of the fracture. The degree of fracture closure is characterized by the effective stress normal to the fracture surface, which is determined by the total normal stress to the fracture surface, the internal pressure of the fracture, and the corresponding effective stress coefficient.

[0034] At the end of construction, the initial effective closure stress is determined based on the crack pressure and ground stress state output by the construction model, and is used as the stress condition for calculating the local crack conductivity.

[0035] As the effective stress in the crack normal direction increases, proppant particles are compressed and embedded, resulting in a corresponding decrease in the effective flow space of the crack and changes in the effective width and permeability of the crack. The degree of crack response to effective stress varies under different proppant placement conditions. Therefore, in determining the initial conductivity, both the local proppant placement condition and the effective stress conditions at the end of construction must be considered.

[0036] Based on the proppant concentration of each local crack segment and the effective stress conditions at the end of construction, the initial local conductivity at different locations is determined according to the aforementioned relationship of local crack conductivity.

[0037] Furthermore, based on the proppant mass conservation principle, the proppant concentration within different fracture elements was calculated; The proppant concentration for each fracture element is expressed as follows: ; In the formula: For the first The concentration of proppant applied to each fracture element; The mass of the proppant within the crack unit; This represents the effective area of ​​the crack.

[0038] During fracturing, the proppant enters the fracture along with the fracturing fluid, and its spatial distribution directly affects the effective flow capacity after the fracture is closed.

[0039] Based on the proppant placement results, the proppant state at different fracture locations is further determined. For cases where there is significant non-uniform proppant distribution within the same inversion unit, the corresponding proppant placement concentration can be further determined according to the local fracture segments and used as input parameters for subsequent calculations of local fracture conductivity.

[0040] S5. Based on the equivalent relationship of hydraulic resistance during fracture flow, the conductivity of locally non-uniform fractures is converted into the initial equivalent conductivity at the inversion element scale: ; in: For the first Initial equivalent diversion capacity at the end of construction of each inversion unit; For the first The main flow path length of each inversion unit; For the first The length of each local crack segment; For the first The number of local crack segments within each inversion unit.

[0041] The conductivity of a fracture is determined by both the effective fracture width and the fracture permeability. The initial effective fracture conductivity is calculated using the following formula: ; In the formula: This represents the initial effective conductivity of the crack; The initial fracture permeability; This represents the initial effective crack width.

[0042] For multiple local fracture segments distributed along the main flow path within the same inversion unit, the initial equivalent conductivity is the initial state dynamically corrected in the subsequent backflow and production stages. It is not the arithmetic mean of the local fracture conductivity, but rather an equivalent parameter obtained while maintaining the original non-uniform fracture system with the same flow resistance. This parameter is converted according to the aforementioned hydraulic resistance equivalence relationship to ultimately obtain the first... Initial equivalent diversion capacity at the end of construction of each inversion unit This is used to describe the overall flow capacity of the inversion unit.

[0043] S6. The initial equivalent conductivity of each inversion unit and its local fracture segment is correlated with the fracture spatial coordinates to form the initial equivalent conductivity field at the end of the fracturing operation.

[0044] This conductivity field reflects the spatial non-uniform conductivity characteristics formed by differences in proppant placement, crack geometry, and effective closure stress at different crack locations, rather than describing the entire crack network using a single average conductivity.

[0045] During fracturing, fracturing fluid carries proppant into the reservoir, forming a complex artificial fracture network. The settlement, migration, and placement of the proppant within the fractures lead to significant differences in the support state of fractures at different locations. Furthermore, reservoir heterogeneity, the degree of development of natural fractures, and variations in fracturing parameters further influence fracture propagation morphology, resulting in effective fractures that are not regular, single fractures but rather composed of multiple fracture units with different conductivity.

[0046] Existing fracturing fracture evaluation methods typically use parameters such as fracture half-length, fracture width, or average conductivity to describe the fracturing effect, treating the entire fracture system as a uniform fracture. This makes it difficult to reflect the heterogeneous conductivity characteristics of different regions within the fracture caused by differences in proppant concentration and changes in closure stress.

[0047] Therefore, a fracture spatial distribution model is first established based on fracturing construction data, and the initial support state inside the fracture at the end of fracturing is determined in conjunction with the proppant transport process. The initial equivalent conductivity corresponding to different fracture units is then calculated to provide initial constraints for the dynamic inversion of fracture conductivity in the subsequent flowback and production stages. The initial conditions for the dynamic correction of fracture conductivity in the flowback stage and the long-term evolution calculation of fracture conductivity in the production stage are obtained through step (1).

[0048] (2) Effective flow guidance capacity correction stage during the backflow stage S1. Calculate the effective flow conductivity coefficient of the return flow: Effective conductivity of the return flow The calculation formula is as follows: ; in: After the return process is completed, the first Effective equivalent flow guiding capacity of each inversion unit; For the first The initial equivalent diversion capacity at the end of construction of each inversion unit.

[0049] For the Each inversion unit has an initial equivalent conductivity at the end of the fracturing operation. During the backflow process, due to the decrease in crack pressure and the change in proppant bearing state, the actual effective conductivity decreases to [a lower value]. Once the effective conductivity coefficient for backflow is determined, the effective conductivity state of the corresponding inversion unit is corrected based on the initial equivalent conductivity at the end of construction, using this coefficient as a benchmark, thereby obtaining the effective equivalent conductivity at the end of backflow.

[0050] Without considering the reopening of cracks, the re-diffusion of proppant, or other factors that could increase the flow capacity of cracks during the backflow process, the effective conductivity coefficient of backflow is taken as a value greater than 0 and not exceeding 1. In this case, the effective equivalent conductivity after the backflow is completed is not higher than the initial equivalent conductivity at the end of construction.

[0051] S2. For target wells with complete backflow test data: First, obtain dynamic data on the flowback stage of the target well.

[0052] The dynamic data during the backflow phase includes changes in backflow flow rate, changes in cumulative backflow volume, changes in bottom hole pressure, and data on shut-in pressure recovery.

[0053] The cumulative backflow volume is obtained by accumulating the backflow flow rate at each moment of the backflow stage over time. It is used to characterize the overall scale of fluid discharged from the fracture system into the wellbore during the backflow process, and together with the instantaneous backflow flow rate, it serves as the flow constraint for dynamic backflow inversion.

[0054] During the flowback process, the pressure decay process is determined based on the change in the fracture representative pressure at each moment relative to the initial flowback state. The fracture representative pressure can be determined based on bottom hole pressure monitoring, pressure recovery data, or dynamic data that reflects fracture pressure changes after wellbore pressure correction, and serves as an important pressure constraint for evaluating fracture closure and changes in flow state.

[0055] Then, maintain the fracture geometry, fracture spatial location, and initial proppant placement as determined in step (1); based on the fracturing construction forward model established in step (1), limit the free adjustment variables of the backflow stage to the backflow effective conductivity coefficients corresponding to each effective inversion unit; update the fracture flow parameters and calculate the simulated backflow dynamics.

[0056] Number of effective inversion units The number of grids in the crack numerical model is determined based on the spatial resolution of the on-site dynamic data and the amount of effective independent constraint information that can be provided. It is not directly equivalent to the number of grids in the crack numerical model, nor is it required to correspond one-to-one with the actual number of cracks.

[0057] During the runoff phase, the crack geometry, crack spatial location, and initial proppant placement determined in the first phase are maintained; these predetermined factors are not treated as freely adjustable variables. Only the effective conductivity coefficient of each inversion unit is adjusted to ensure consistency between the simulated and field runoff responses. This approach avoids the equivalent compensation between parameters caused by simultaneously adjusting crack geometry and flow parameters during the runoff phase.

[0058] For each set of backflow effective conductivity coefficients to be corrected, the backflow stage effective conductivity state of the corresponding inversion unit is updated based on the initial equivalent conductivity obtained in step (1), and the updated effective conductivity is assigned to the corresponding crack unit in the backflow numerical model.

[0059] When fracture permeability and fracture width are used as input fracture flow properties, the target effective flow capacity is converted into the equivalent fracture flow parameters required by the model based on the aforementioned relationship between fracture conductivity and fracture permeability and fracture width.

[0060] If the crack width determined by the construction model remains unchanged during the backflow stage, the equivalent crack permeability at the end of the backflow is determined based on the target effective flow capacity and the corresponding crack width, and the crack flow capacity in the numerical model is updated accordingly.

[0061] Finally, to quantitatively evaluate the degree of matching between the simulated response and the on-site backflow dynamics, an objective function for the backflow stage is established: ; in: For the first Simulate the backflow response at each time point; For on-site return and observation response; For different dynamic data weighting coefficients, N is the total number of valid observation data points participating in the dynamic matching of the back-row.

[0062] The effective conductivity coefficient during the backflow stage is adjusted to ensure that the objective function meets the preset error requirement or achieves the optimal matching result, thereby obtaining the effective equivalent conductivity at the end of the backflow of each inversion unit under the condition of having effective backflow data. This result serves as a data condition branch for subsequently determining the initial effective conductivity during the production stage.

[0063] The dynamic response to backflow can be selected from one or more of the following, based on field data: backflow flow rate, cumulative backflow volume, pressure changes during the backflow stage, and shut-in pressure recovery response. By appropriately setting the weights of different types of dynamic data, observation data with different dimensions and sensitivities can jointly participate in the correction of effective flow conduction capacity during the backflow stage.

[0064] This step involves establishing a dynamic simulation model of the backflow, calculating the simulated backflow flow rate, cumulative backflow volume, and pressure changes, and matching this model with on-site backflow data to obtain results that meet the error requirements. .

[0065] S3. For target wells lacking continuous backflow or effective pressure recovery data: First, determine the effective flow correction coefficient for early production according to the following formula. : ; in: This is the effective equivalent flow guiding capacity obtained based on early production dynamic correction; For the first The initial equivalent diversion capacity at the end of construction of each inversion unit.

[0066] Then, after the effective flow correction coefficient for early production is determined, the effective flow state of the corresponding inversion unit is corrected based on the initial equivalent flow capacity at the end of construction, so as to obtain the effective equivalent flow capacity after the return flow ends and before entering the long-term production stage.

[0067] In the specific correction process, the effective flow correction coefficients for early production of each inversion unit are iteratively adjusted, and the dynamic response of early production under the corresponding conditions is calculated respectively.

[0068] The parameters were determined based on the comprehensive matching degree between simulated liquid production, oil production, water content, and pressure response during periods with effective pressure recording, and on-site measured data.

[0069] When the main dynamic responses meet the preset error requirements, or when the optimal parameter combination with the best overall matching effect is obtained within the given parameter range, the early production effective flow correction coefficient of the corresponding inversion unit is determined.

[0070] Furthermore, the specific method for constraining the number of inversion parameters is as follows: To reduce the non-uniqueness of parameters in the dynamic inversion of multi-stage and multi-cluster fractured wells, the number of inversion parameters is limited based on the resolution capability of the field dynamic data.

[0071] When the target well has distributed fiber optic monitoring, production logging, tracer or other fracture cluster-level dynamic data that can stably distinguish the dynamic response of different fracture clusters, effective conductivity correction coefficients can be set according to fracture clusters or fracture cluster groups that can be independently identified.

[0072] When the on-site dynamic data can only be resolved down to the scale of the fracturing section, multiple fracture clusters that cannot be further distinguished by dynamic response within the same fracturing section are merged into one inversion unit, and a unified effective conductivity correction coefficient for the fracturing section is adopted, without setting independent free parameters for each fracture cluster within the section.

[0073] When the target well only has whole-well flowback or whole-well production dynamic data, the number of free inversion parameters should be limited. For a small number of fracturing sections whose fracture geometry, proppant placement, and initial equivalent conductivity have been determined through the fracturing construction stage, a limited number of section-level effective conductivity correction parameters can be retained within a given prior constraint range and corrected by joint history fitting. When different combinations of section-level parameters produce significant equivalent compensation to the whole-well dynamic response and stable correction results cannot be obtained, multiple inversion units that cannot be effectively constrained by dynamic data should be further merged, and a unified effective conductivity correction coefficient should be used for overall correction.

[0074] After the fracturing operation is completed, the fluid pressure inside the fracture gradually decreases, the contact state between the proppant and the fracture wall changes, and some fracturing fluid is returned into the wellbore, causing the flow conditions inside the fracture to gradually change from the fracturing operation state to the production flow state.

[0075] Since the fracture geometry and proppant spatial distribution determined during the fracturing operation only represent the initial state at the end of fracturing, the effective conductivity of the fractures changes due to fracture closure, proppant reloading, and changes in local flow channels during the flowback process. Therefore, it is necessary to use dynamic data from the flowback stage to correct the initial equivalent conductivity. Existing methods typically adjust fracture parameters directly using flowback pressure recovery or production dynamic data. However, for multi-stage, multi-cluster fracturing wells, adjusting the conductivity parameters of each fracture unit simultaneously would result in an excessive number of parameters to be inverted, potentially leading to similar dynamic responses from different combinations of fracture parameters and reducing the reliability of the inversion results.

[0076] In some fractured wells, due to limitations in field testing conditions, complete flowback flow, cumulative flowback volume, or pressure recovery data may not be available, making it impossible to directly use standard flowback dynamics to invert effective conductivity. Therefore, when the target well lacks continuous flowback flow or effective pressure recovery data, production data is not directly used to replace flowback data. Instead, early production dynamics after the flowback is completed and before long-term stable production are used as the basis for effective state correction.

[0077] By selecting the early production stage after fracturing and before long-term stable production, and utilizing the fluid production, oil production, water cut, and pressure decay characteristics at the time of effective recording during this stage, the initial equivalent conductivity at the end of the operation is corrected.

[0078] S4. Based on the type of on-site data, obtain the effective equivalent diversion capacity after the return flow is completed. This allows for the determination of the initial effective flow diversion capacity during the production phase. ; in: This represents the effective equivalent flow diversion capacity after the return flow is completed. After the return process is completed, the first Effective equivalent flow guiding capacity of each inversion unit; This is the effective equivalent flow guiding capacity obtained based on early production dynamic correction.

[0079] This step avoids mixing data with different physical meanings, while ensuring that effective crack conductivity state correction can be achieved under both engineering conditions where the backflow data is complete and the backflow data is missing.

[0080] In summary, step (2) uses the initial equivalent flow capacity of the inversion unit obtained in step (1) as the basis for the result. As a priori state, based on the spatial resolution of the field-returned data, the effective flow conduction state of only a limited number of inversion units is corrected to obtain the effective equivalent flow conduction capacity after the return process is completed. .

[0081] (3) Inversion stage of dynamic and effective flow diversion capacity in the production stage S1, obtained in step (2) As the initial effective conductivity during the production stage; during production, as the crack pressure changes, the normal effective stress on the crack surface changes, the first The inversion unit corresponds to the change of crack pressure with production time, the first... Each inversion unit during production time The representative crack pressure is denoted as .

[0082] According to the effective stress principle, the effective stress in the normal direction of the crack surface is as follows: ; in: For the first Each inversion unit in time The normal effective stress; This represents the total normal stress on the crack surface. The representative fracture pressure of the inversion unit; This represents the effective stress coefficient of Biot.

[0083] The fracture pressure can be obtained from fracture seepage models, reservoir numerical simulation results, or production dynamic fitting results, and is used to characterize the internal pressure state of fractures at different production stages.

[0084] The total normal stress on the fracture surface is determined based on the reservoir stress state and the spatial propagation direction of the fractures corresponding to the inversion unit. For fracture units with different spatial orientations, the stress state is converted into the total normal stress acting on the fracture surface according to the normal direction of the fracture surface, and this is used as the basic parameter for calculating the effective stress.

[0085] When the change in total stress during production is relatively small compared to the change in crack pressure, an engineering simplification can be adopted, as shown in the following formula: ; In the formula, For the first The total normal stress on the crack surface at the initial moment of the production stage of each inversion unit.

[0086] Based on the representative crack pressure changes at each production stage, the effective stress normal to the crack surface of different inversion units is calculated hourly, and the change process of effective stress over time during production is obtained. This result is used to identify whether the crack has experienced a new, higher effective stress state and to provide stress input for subsequent dynamic updates of conductivity based on stress sensitivity laws.

[0087] S2, adopting the method in the actual production stage Actual stress sensitivity coefficient of each inversion element Dynamic updates will be performed. The actual stress sensitivity coefficient of each inversion element is expressed as: ; in: For the first The inversion unit number Actual stress sensitivity coefficient for each effective stress range; This is a field correction factor; For the experimental conditions, the first The inversion unit number The conductivity attenuation coefficient within an effective stress range is used as a priori stress sensitivity coefficient.

[0088] During long-term proppant loading, as the effective closure stress of the crack increases, the pore space between proppant particles decreases, which may be accompanied by proppant compaction, particle breakage and embedding, thereby reducing the proppant crack's permeability and conductivity.

[0089] Specifically, based on the changes in conductivity under different effective stress conditions obtained from the experiment, the experimental loading stress range is divided into several effective stress intervals, and the conductivity attenuation coefficient corresponding to each effective stress interval is calculated.

[0090] Based on the experimentally obtained relationship between conductivity variation under different effective stress conditions, the first definition is... Conductivity attenuation coefficient within an effective stress range: ; in: The first obtained from the experiment The conductivity attenuation coefficient within an effective stress range; and These represent the experimental conductivity under the corresponding effective stress conditions.

[0091] It is only used to describe the basic stress sensitivity of the proppant system under experimental conditions and is not directly used as a parameter for dynamic inversion of cracks in the field.

[0092] Due to differences between experimental conditions and actual fracturing fracture environments, including variations in fracture roughness, proppant placement inhomogeneity, proppant embedding, fracturing fluid flowback, and the influence of long-term production history, the attenuation patterns of fracture conductivity in the field differ from those observed experimentally. Therefore, based on the stress sensitivity patterns obtained from long-term proppant conductivity experiments under different effective stress ranges, and considering proppant embedding, breakage, placement inhomogeneity, and differences in experimental conditions in actual fractures, a field correction factor is introduced. The stress sensitivity characteristics of different inversion units are modified.

[0093] Using the above method, the original requirement of simultaneously inverting multiple [databases / systems] can be reduced. Parameters are converted to adjust only a limited number of parameters. Parameters, reducing the number of parameters in the production dynamics inversion process.

[0094] The number of field correction coefficients is determined based on the spatial resolution of the field production dynamic data. When there is fracture cluster-level monitoring data that can stably distinguish the dynamic response of fracture clusters, corresponding field correction coefficients can be set for different identifiable fracture clusters or fracture cluster groups. When the field data can only be resolved to the scale of the fracturing section, fracture units that cannot be further distinguished within the same fracturing section are corrected using a unified field correction coefficient. When there is only whole-well production dynamic data and the independent stress-sensitive responses of different inversion units cannot be effectively distinguished, multiple inversion units that cannot be independently constrained by the dynamic data are corrected using a unified field correction coefficient.

[0095] S3. To account for irreversible conductivity losses caused by proppant compaction and embedding, the historical maximum effective stress is introduced, and the first... The historical maximum effective stress of each inversion element: ; in: For the first i The historical maximum effective stress of each inversion unit up to production time t; For the first i Each inversion unit at a historical moment τ The effective stress normal to the crack surface; τ It is a historical time variable that is no later than the current production time t.

[0096] Because the proppant compression deformation and crack closure processes are irreversible, the crack conductivity is affected not only by the current effective stress but also by the maximum effective stress experienced during production.

[0097] When the effective stress increases during the production process It is believed that this results in a new loss of diversion capacity; when It is believed that the cracks undergo an unloading process, but due to the irreversible changes caused by the compaction and embedding of the proppant, the loss of conductivity that has already occurred cannot be recovered.

[0098] S4, in the Within each production stage, based on the stress sensitivity principle, the dynamic effective flow guidance capacity of each production stage is updated to... : ; in: For the first The inversion unit number Actual stress sensitivity coefficient for each effective stress range; For the first The production stage is in the first The amount of effective stress change experienced within an effective stress range.

[0099] The field stress sensitivity coefficient used for dynamic updating The field correction is determined by the experimental prior stress sensitivity coefficient and the corresponding inversion unit field correction coefficient, according to the aforementioned field correction relationship. This process introduces the foundation stress sensitivity law obtained under proppant experimental conditions into the field crack dynamic conductivity update process, while simultaneously using a limited number of field correction parameters to correct for differences between experimental conditions and the actual crack environment.

[0100] The initial effective flow capacity of the production stage is determined in step (2). Starting from the initial state, in each subsequent production time step, the dynamic effective flow conduction capacity obtained from the previous time step is used as the initial state for the next time step, and the state is continuously updated according to the newly added effective stress and the corresponding on-site stress sensitivity coefficient in that time step. ; ultimately won the first The evolution of the dynamic effective flow guiding capacity of each inversion unit over production time This allows us to obtain the continuous dynamic change of the effective flow guiding capacity of each inversion unit over time throughout the entire production process.

[0101] Furthermore, in the Within the production time step, the first Effective stress increment of each inversion unit Represented as: ; In the first Within the production time step The historical maximum effective stress of each inversion unit; In the first Within the production time step The current effective stress of each inversion element.

[0102] When the newly added effective stress spans multiple stress-sensitive intervals, the newly added effective stress is decomposed according to each effective stress interval, denoted as... , represents the amount of new effective stress change when the i-th inversion unit falls into the r-th effective stress range during the k-th production time step.

[0103] S5. Correlate the dynamic effective conductivity of each inversion unit with its corresponding fracture spatial location to form the spatiotemporal distribution of effective fracture conductivity during the production stage, expressed as follows: ; in: Indicates the spatial location of the crack; Indicates the production time.

[0104] In this expression, spatial differences mainly arise from variations in fracture geometry, proppant placement, initial equivalent conductivity, and field correction parameters across different inversion units; temporal variations primarily stem from changes in normal effective stress caused by fracture pressure variations during production and their historical loading effects. Therefore, the dynamic effective fracture conductivity described in this invention is not a uniform, single time function for the entire well, but rather a dynamic fracture attribute that uses the inversion unit as the basic evaluation object and simultaneously exhibits spatial non-uniformity and temporal evolution characteristics.

[0105] The final output shows the initial effective flow guidance capacity of each inversion unit. Dynamic and effective flow guidance capability during production process The decay law of fracture conductivity; the distribution of dominant conductivity fractures at different time stages. The output results can serve as the basis for subsequent evaluation of fracture production contribution.

[0106] After the effective fracture conductivity is corrected during the flowback phase, the fracture enters the long-term production phase. During production, as formation fluids are continuously extracted, the internal pressure of the fracture continues to decrease, and the effective closure stress on the fracture surface gradually increases. This causes changes in the contact state between proppant particles, the contact state between proppant and the fracture wall, and the effective flow space of the fracture, resulting in dynamic changes in the fracture conductivity over production time.

[0107] Existing methods for evaluating the production dynamics of fractured wells typically treat fracture conductivity as a fixed parameter, relying solely on historical data by adjusting parameters such as fracture length and permeability. This approach fails to reflect the dynamic attenuation of fracture conductivity due to changes in effective stress over long-term production. For multi-stage, multi-cluster fractured wells, setting independent stress-sensitive parameters for each fracture unit would result in an excessive number of inversion parameters, making it impossible for production dynamic data to effectively constrain all parameters and leading to non-uniqueness in the inversion results.

[0108] To address the aforementioned problems, the present invention utilizes the effective flow guidance capability obtained in step (2) at the end of the backflow process. As the initial state of the production stage, by establishing the relationship between effective stress change and crack conductivity decay, the proppant stress sensitivity law obtained from experiments is introduced, and the field crack state is corrected by using low maintenance positive parameters, so as to realize the dynamic update of effective crack conductivity during the production process.

[0109] (4) Evaluation stage of crack production contribution S1. Based on the dynamic effective flow guiding capacity obtained in step (3) during the production process, establish a basic production model containing all effective crack elements.

[0110] The crack flow properties of each inversion unit in the basic production model are obtained using the corresponding dynamic effective conductivity obtained from the third-stage inversion. And keep its dynamic characteristics unchanged as production time changes, so that the evaluation of fracture production contribution is based on the effective fracture state after production dynamic correction has been completed, rather than reusing the initial fracture parameters at the end of the fracturing operation.

[0111] In the basic model, all inversion units participate in fluid exchange, and their corresponding cumulative output is denoted as... It can be used to evaluate the cumulative production within the evaluation period under the condition that all effective crack elements act together.

[0112] S2. Calculation method for marginal production response of a single crack element: The marginal contribution analysis method is used to evaluate the impact of a single crack element on the overall production capacity; the flow conduction capacity of the target inversion element is reduced to a set state. ; in: To reduce the first Dynamic and effective flow guidance capability after each inversion unit; The coefficient for reducing the flow capacity is a value that is not less than 0 and less than 1.

[0113] when Further reduction indicates a stronger weakening of the flow capacity of the target inversion unit; when it is set to 0, it can be used to characterize the extreme case where the target inversion unit no longer provides effective flow guidance during the evaluation process.

[0114] Keeping reservoir parameters, production regime, and other inversion unit dynamic conductivity constant, only changing the first The effective flow guidance capacity of each target inversion unit is used to recalculate the output for the evaluation period. The resulting changes in production response should primarily reflect the impact of changes in the flow guidance state of the target inversion unit.

[0115] When evaluating different inversion units, a consistent weakening method or weakening scale should be used to ensure that the marginal production responses of different inversion units are comparable.

[0116] S3. After obtaining the dynamic effective conductivity of each inversion unit, the marginal production variation method is adopted to evaluate the impact of different fracture units on the overall well production.

[0117] By recalculating the production dynamics in step S2, the reduction of the first Cumulative output after the flow-guiding capacity of each inversion unit ; Define the first Marginal production impact of each inversion unit That is, the first The difference in output before and after adjusting the effective flow capacity of each inversion unit : ; in: The cumulative output while maintaining the current dynamic diversion capacity for all inversion units; To reduce the first The cumulative output after the flow diversion capacity of each inversion unit.

[0118] Indicates the first The impact of changes in the effective conductivity of a fracture unit on the overall well production capacity is a measure of the impact of these changes on the overall well production capacity. This indicator differs from the simple production allocation ratio; it reflects the marginal impact of a fracture unit on the overall production response when the effective conductivity of that fracture unit changes.

[0119] S4, Definition of the Normalized marginal production contribution index of each inversion unit : ; in: For the first The marginal production impact of each inversion unit; Because of the first jThe cumulative decrease in overall well production caused by the weakening of the conductivity of each inversion unit; The number of effective crack inversion units; The range of values .

[0120] After normalization, the sum of the normalized marginal production contribution indices of each inversion unit is 1, and the contribution index of a single inversion unit is a value between 0 and 1 under normal evaluation conditions. A larger contribution index indicates a higher relative impact of the conductivity change of that inversion unit on the overall well production response within the current evaluation period and model state. Through the above calculations, the relative contribution of different effective fracture units to the overall well production capacity can be obtained.

[0121] Since the cumulative production varies among different well groups and evaluation periods, the marginal production impact is further normalized to facilitate comparison between different fracture units. Indicates the first The marginal impact of each inversion unit on the overall well production response under the current model conditions. This indicator is used to identify dominant and inefficient fracture units and is not equivalent to the actual fracture production distribution ratio directly measured under production logging conditions.

[0122] S5. Because the conductivity of fractures changes with production time, the fracture production contribution index also exhibits time-varying characteristics. At different production stages... Calculate the normalized marginal production contribution index corresponding to each inversion unit according to the formula in step S4. .

[0123] By comparing the normalized marginal production contribution index of different inversion units at the same production stage, and analyzing the variation law of the contribution index of the same inversion unit at different production stages, dynamic dominant fractures can be identified. Specifically, fracture units with sustained high contribution, fracture units with high contribution in the early stage but significant decline in the later stage, and inefficient fracture units with high dynamic effective conductivity but limited impact on the overall well production response can be identified.

[0124] When there are clear engineering evaluation standards, the threshold for determining the contribution of dominant fractures can be set according to the number of inversion units of the target well, the distribution characteristics of the contribution index, and the evaluation purpose, so as to further classify and identify the dominant contribution fractures at different production stages.

[0125] After the calculation in step (3) above, the dynamic effective flow guiding capacity of different inversion units in the production process can be obtained. This parameter can characterize the effective conductivity of different fracture units as production time changes. However, in multi-stage and multi-cluster fracturing wells, although different fracture units all have a certain conductivity, their contribution to the actual production capacity of the well varies significantly due to differences in fracture spatial location, reservoir properties, pressure propagation range, and flow competition between fractures.

[0126] Existing methods typically evaluate fracture contribution based on fracture length, conductivity, or fracture production distribution ratio. However, areas with longer fractures do not necessarily have a higher production contribution, and actual production capacity is also affected by reservoir fluid supply capacity and pressure transmission capacity. Simply ranking fractures by conductivity only reflects their own flow capacity and cannot characterize their actual impact on overall well production dynamics. If production ratio is used to evaluate fracture contribution, different fractures influence each other, making it difficult to distinguish the marginal effect of a particular fracture unit on overall production capacity.

[0127] Therefore, based on the calculation results of dynamic effective flow capacity, this invention aims to establish a normalized marginal production contribution index evaluation method. By changing the effective flow state of the target inversion unit, the influence of the unit on the overall production response is analyzed, thereby realizing the identification of advantageous effective crack units.

[0128] This invention ultimately obtains the initial equivalent conductivity of each inversion unit at the end of the fracturing operation. The initial effective flow diversion capacity of the production stage determined after early production dynamic correction under conditions of missing or backflow dynamic data. Dynamic and effective flow guidance capability during production process And the normalized marginal contribution index of production at different production stages. This forms a comprehensive evaluation system covering the entire process from crack formation state to effective state after backflow, production dynamic state, and production contribution state.

[0129] By combining the dynamic effective conductivity change process with the evaluation of fracture production contribution, a step-by-step evaluation is achieved, from "whether a fracture has formed" to "whether the fracture maintains effective conductivity" and then to "whether the fracture makes a significant contribution to the overall well production," providing a basis for effective fracture identification, fracturing effect evaluation, and subsequent measure optimization in fractured wells.

[0130] The beneficial effects of this invention are as follows: (1) A continuous quantitative conversion relationship was established between the cracks formed during hydraulic fracturing and the actual effective flow-conducting cracks after fracturing.

[0131] Instead of directly using the fracture length, fracture height, or initial fracture properties obtained from fracturing simulation as fixed effective fracture parameters for the long-term post-fracturing production stage, the fracture conductivity is used as a continuous state parameter. The initial equivalent conductivity at the end of the fracturing operation, the initial effective conductivity after flowback or early production correction, and the dynamic effective conductivity during the long-term production process are inherited and updated stage by stage, thereby achieving continuous connection between the fracture states in the three stages of fracturing operation, flowback, and production.

[0132] Compared with existing methods that mainly focus on crack network geometry and attribute inversion, this method can further characterize the changes in the effective conductivity of construction-induced cracks under actual post-compression conditions.

[0133] (2) It can characterize the effect of the non-uniformity of proppant placement inside the actual crack on the overall flow capacity.

[0134] The initial conductivity of the local fracture segment is determined based on the proppant concentration and normal effective stress at different fracture locations, and the initial equivalent conductivity of the inversion unit is obtained according to the hydraulic resistance equivalent relationship on the main flow path, rather than using the simple arithmetic mean of the local conductivity.

[0135] Therefore, it can reflect the series flow bottlenecks formed in low-conductivity areas such as the far end of the well and the local low sand-covered area, making the initial effective conductivity state of the obtained inversion unit more consistent with the actual flow characteristics of non-uniform supported fractures.

[0136] (3) Improved the engineering applicability of the method under different levels of completeness of on-site data.

[0137] For target wells with complete backflow flow, cumulative backflow volume and pressure data, this invention uses backflow dynamics to correct the initial equivalent conductivity at the end of construction; for target wells lacking continuous backflow data, the early production dynamics after the end of backflow are used to replace and correct the initial effective conductivity state of the production stage, and the early production data and backflow data are not confused as the same physical process.

[0138] This makes the method applicable to both fractured wells with relatively complete flowback monitoring data and engineering conditions where on-site flowback test data is incomplete but production dynamic data is available.

[0139] (4) It reduces the non-uniqueness of parameters in the dynamic inversion of multi-stage and multi-cluster fracturing wells.

[0140] During the fracturing construction phase, the main geometric shape of the fracture and the proppant placement are determined first. In the subsequent flowback and production phases, the determined geometric parameters such as fracture length, fracture location, and fracture orientation are no longer adjusted simultaneously. Instead, a limited number of effective flow correction parameters and on-site stress-sensitive correction parameters are set based on the spatial resolution of the on-site dynamic data.

[0141] For crack elements that cannot be effectively constrained independently by dynamic data, further parameter merging is performed to reduce the equivalent compensation between different crack parameters, thereby improving the stability and engineering interpretability of the dynamic inversion results.

[0142] (5) It can reflect the dynamic evolution of effective crack conductivity with effective stress and loading history during long-term production.

[0143] By combining the stress sensitivity prior law obtained from long-term proppant conductivity experiments with field production dynamics, the stress sensitivity law under experimental conditions is transformed to actual crack conditions through a limited number of field correction coefficients. At the same time, the historical maximum effective stress is introduced, and new irreversible conductivity loss is calculated only for the newly added loading portion that exceeds the existing maximum effective stress, so as to avoid restoring the conductivity loss caused by proppant compaction, embedding and breakage when the crack is unloaded or reloaded within the historical stress range.

[0144] Compared to methods that use fixed crack flow capacity or only determine reasonable flow capacity in the design sense, this method can obtain effective flow capacity with time evolution characteristics in the field.

[0145] (6) It further distinguishes between dynamic effective flow conduction capacity and the actual production impact of cracks.

[0146] After obtaining the dynamic effective conductivity of each inversion unit, the dynamic effective conductivity of the target inversion unit is changed while keeping the reservoir parameters, production regime and other fracture unit states unchanged. The cumulative production change of the whole well is calculated and a normalized marginal production contribution index is established accordingly.

[0147] The evaluation results reflect the relative impact of changes in the conductivity of the target fracture on the overall well production response, rather than simply replacing the fracture production contribution with fracture length, conductivity, or the production logging segment production ratio. Therefore, it can identify high-conductivity but low-contribution fractures, continuously high-contribution fractures, and inefficient fractures with significant long-term decay, providing a basis for fracturing effect evaluation, production system adjustment, and subsequent measure optimization. Attached Figure Description

[0148] Figure 1 This is a flowchart illustrating the method for dynamically inverting the effective fracture conductivity of fracturing wells based on multimodal monitoring data, as per the present invention.

[0149] Figure 2 This is a schematic diagram illustrating the stress-sensitive prior law, field correction, and irreversible update of the proppant crack conductivity of the present invention.

[0150] Figure 3This is a schematic diagram showing the dynamic effective conductivity and the change of effective stress in the normal direction of the fracture surface with the production stage of each inversion unit of the inclined well 22 in this embodiment of the invention.

[0151] Figure 4 This is a schematic diagram illustrating the fitting effect and relative error between the simulation results and measured data in an embodiment of the present invention; wherein, Figure 4 In the middle (a), the simulated values ​​of each fitting index deviate from the measured values. Figure 4 In the middle (b), the relative error of each fitting index is represented. Detailed Implementation

[0152] The technical solution of the present invention will be described in detail below.

[0153] Example 1 The following section, using field data from Well 22 in Block B, provides a detailed explanation of the dynamic inversion method for the effective fracture conductivity of fracturing wells based on multimodal monitoring data.

[0154] The basic data used include reservoir interpretation results from well 22 in a certain block, fracturing operation records of the first and second stages, and post-fracturing production dynamics data.

[0155] Field data are used to establish basic reservoir and fracture models, constrain fracturing operations and production dynamics; fracture geometric parameters, proppant spatial placement, initial equivalent conductivity, early production effective conductivity and dynamic effective conductivity during production stages are calculated according to the aforementioned methods.

[0156] Taking two-stage fracturing as an example, the specific implementation process is explained. For fracturing wells with more fracturing stages and fracture clusters, corresponding inversion units can be divided based on the effective independent constraint information provided by the on-site dynamic data, and the effective fracture conductivity can be dynamically inverted using the same method.

[0157] The specific steps are as follows: The target formation of this fractured well is mainly located within a depth range of 3088.8m to 3147.4m. Reservoir interpretation results show that there are 11 sub-layers interpreted as oil-bearing layers within the target formation, with a total effective oil layer thickness of 13.7m, an average porosity of 16.90%, an average permeability of 34.77mD, and an average clay content of 12.60%.

[0158] This well lists 12 perforated sub-layers, with a total perforation thickness of 12.5m and a total of 108 perforations. The perforated sections include 3088.8–3089.8m, 3095.0–3096.5m, 3098.1–3099.1m, 3102.7–3103.7m, 3105.0–3106.0m, 3116.5–3117.5m, 3120.0–3121.0m, 3123.5–3124.5m, 3129.0–3130.0m, 3131.3–3132.3m, 3137.0–3138.0m, and 3142.5–3143.5m.

[0159] Pre-fracturing fluid level was 70.9m. 3 550.5m of sand-carrying liquid 3 Displacement fluid 55.9m 3 Total liquid volume: 677.3m 3 The typical construction discharge volume is 9.5–10.2 m³. 3 The pump speed is [unspecified] / min, with a typical construction pressure of 41.2–48.7 MPa, a bursting pressure of 57.8 MPa, and a shutdown pressure of 34.9 MPa. 30.8 m³ of 40 / 70 mesh silica sand is added in the first stage. 3 40 / 70 mesh ceramsite 19.2m 3 Total sand volume: 50m³ 3 .

[0160] Pre-fracturing fluid level of 62.0 m³ was introduced before the second stage of fracturing. 3 323.2m of sand-carrying liquid 3 Displacement fluid 47.6m 3 Total liquid volume: 432.8m 3 The typical construction discharge volume is 9.5–10.1 m³. 3 The pump speed is [value missing] / min, with a typical construction pressure of 38.9–43.4 MPa, a bursting pressure of 43.9 MPa, and a shutdown pressure of 35.8 MPa. 12 m³ of 40 / 70 mesh silica sand is added in the second stage. 3 40 / 70 mesh ceramsite 9m 3 30 / 50 mesh ceramsite 9m 3 Total sand volume: 30m³ 3 And add 16 temporary blocking knots.

[0161] The post-pressurization production dynamics data includes 52 valid records, with a cumulative liquid production of 785.5 t and a cumulative oil production of 227.9111 t. The initial recorded pressure was 20.97 MPa, which gradually decreased with production, reaching a minimum of 0.40 MPa. Some pressure data was missing during the later pumping phase of production. Therefore, in the production dynamics correction process, the early stage of production used a combination of liquid volume, oil volume, water cut, and pressure data as constraints, while the later stage primarily used liquid volume, oil volume, and water cut as constraints.

[0162] Since the existing dynamic data of this well is mainly whole-well production data, and lacks segmented production logging, distributed fiber optic monitoring or tracer data that can stably distinguish the independent dynamic response of each perforation cluster, independent free inversion parameters are not set for each of the 12 perforation layers. Instead, two inversion units are divided according to the two-stage fracturing operation on site, which are denoted as the first inversion unit and the second inversion unit, respectively.

[0163] The inversion cell division results are used for subsequent initial equivalent conductivity calculation, early production state correction, and long-term production dynamic updates. The number of inversion cells is determined by the effective independent information that dynamic data can provide, rather than by the number of grids in the crack numerical model.

[0164] The geomechanical parameters and proppant conductivity parameters used are shown in Table 1 below.

[0165] Table 1

[0166] Reservoir interpretation parameters, perforation data, and two-stage fracturing operation curves were input into the Kinetix fracturing operation simulation software. The actual operation pressure curve was used as the fitting target to perform historical fitting of fracture geometry and proppant placement distribution.

[0167] During the construction history fitting process, the basic parameters affecting crack propagation and proppant transport are adjusted to match the simulated construction response with the on-site fracturing process.

[0168] After completing the construction phase calculations, determine the main spatial location of the cracks, crack length, height, width, and the range of proppant application.

[0169] In the subsequent early and long-term production inversion stages, the main crack geometry parameters remain fixed and are no longer used as free inversion variables.

[0170] Based on the construction history fitting, the parameters of the two main crack elements are shown in Table 2 below.

[0171] Table 2

[0172] The crack half-length, crack height, crack width, and effective support length are model results obtained by fitting the construction history, which are used to characterize the crack geometry and proppant placement at the end of the fracturing operation.

[0173] At the end of the fracturing operation, the effective stress in the normal direction of the fracture surface of the inversion unit is calculated according to the aforementioned method. This embodiment takes... The total normal stress on the crack surface of the first inversion element is 43.0 MPa, and the total normal stress on the crack surface of the second inversion element is 42.5 MPa.

[0174] Since direct pressure monitoring data inside the fracture was not obtained at the end of construction of the target well, the on-site pump shutdown pressure was used as an engineering approximation of the representative fracture pressure, with 34.9 MPa for the first segment and 35.8 MPa for the second segment.

[0175] Therefore, the effective normal stress on the crack surface at the end of the construction of the first inversion unit is:

[0176] This represents the effective stress in the normal direction of the crack surface at the end of the construction of the first inversion unit, which is calculated to be 13.34 MPa.

[0177] At the end of the construction of the second inversion unit, the effective normal stress on the crack surface is:

[0178] Using the pump shutdown pressure as the representative pressure of the fracture is an engineering approach under conditions where direct pressure data inside the fracture is lacking. When the average fracture pressure output from the fracturing construction model, the bottom hole pressure after correction for hydrostatic pressure and friction, or other monitoring data that can characterize the pressure inside the fracture can be obtained, the corresponding pressure should be used to determine the effective stress of the fracture.

[0179] Based on the proppant placement distribution obtained from the construction model and the reference law of the flow conductivity of similar proppants, the initial estimate of the local crack flow conductivity of each inversion unit along the main flow direction is made.

[0180] The effective supporting fractures of each inversion unit are divided into near-wellbore, middle, and far-wellbore sections along the main flow direction. The calculation results of the local conductivity of the two fracture sections are shown in Table 3 below.

[0181] Table 3

[0182] For different local fracture segments on the same main flow path, the initial equivalent flow capacity of the entire inversion unit is determined by the hydraulic resistance equivalent method.

[0183] The initial equivalent flow conduction capacity of the first inversion unit is: .

[0184] The initial equivalent flow conduction capacity of the second inversion unit is: .

[0185] The value represents the initial equivalent flow capacity at the end of construction of the second inversion unit, expressed as D·cm.

[0186] Therefore, the initial equivalent conductivity of the two fracture sections at the end of the fracturing operation is shown in Table 4.

[0187] Table 4

[0188] Calculation results show that the equivalent conductivity of the inversion unit is not the arithmetic mean of the conductivity of local fractures. Although the fracture size and effective support length of the first inversion unit are larger than those of the second inversion unit, there is a lower conductivity region at its far end, which generates a large series hydraulic resistance in the main flow path, thereby reducing the initial equivalent conductivity of the entire inversion unit.

[0189] Since existing data do not include continuous flow rate, cumulative flow rate, and complete shut-in pressure recovery data that can be independently used for standard flowback inversion, the standard flowback inversion method with complete flowback data is not adopted. Instead, the early production effective state correction method under the condition of missing flowback data is adopted.

[0190] The initial stage of production after the return flow is completed, characterized by high moisture content and rapid pressure decline, is selected as the early stage of effective production state correction.

[0191] Table 5 below shows some of the on-site production data for this stage.

[0192] Table 5

[0193] While keeping the main geometric parameters of the crack constant, the initial equivalent conductivity at the end of construction of the two inversion units is used as the basis. This is a priori value, representing the effective flow correction coefficient for early-stage production. Adjustments will be made.

[0194] The effective flow characteristics of the two inversion units are corrected by comparing simulated liquid volume, oil volume, water content, and pressure changes during the pressure recording phase with early-stage production dynamics in the field. The calculation process is as follows: ; .

[0195] After early production dynamic correction, the initial effective diversion capacity of the first inversion unit during the production stage decreased by approximately 24% compared to the initial equivalent diversion capacity at the end of construction, while that of the second inversion unit decreased by approximately 31%. Although the initial equivalent diversion capacity of the second inversion unit was higher at the end of construction, its early production effective diversion correction coefficient was lower than that of the first inversion unit.

[0196] Gain initial effective flow control capability during the production phase Subsequently, based on pressure changes during long-term production, the dynamic effective conductivity of the two inversion units was updated. During production, as the pressure inside the crack gradually decreases, the effective normal stress on the crack surface increases accordingly. For the first... Each inversion unit, in production time The effective stress in the normal direction of the crack surface at that time is calculated according to the aforementioned effective stress relationship.

[0197] Based on the production system and dynamic changes in production, the production process is divided into the early effective production stage, the stable production stage of 2 mm nozzles, the low-pressure production stage of 2 mm nozzles, the production stage of 5 mm nozzles, and the open-spray and oil extraction stage.

[0198] Based on the actual data of the target well, a long-term conductivity test curve completely corresponding to the proppant combination of that well will not be established separately. In the specific implementation process, the general experimental law of gradual decay of conductivity of similar proppants such as 40 / 70 mesh quartz sand, 40 / 70 mesh ceramsite, and 30 / 50 mesh ceramsite under different effective closure stress conditions is adopted to a priori constrain the changing trend and reasonable value range of the basic stress sensitivity coefficient, and the sensitivity of the on-site fracture stress is corrected in combination with the actual production dynamics of the target well.

[0199] Because the proppant combinations of the first and second inversion units differ, each adopts a priori stress sensitivity variation trend corresponding to its proppant composition. However, the stress sensitivity coefficients for each effective stress range are not all set as independent free parameters. The actual stress sensitivity coefficients after on-site correction are determined through production dynamic fitting, and the dynamic conductivity is updated accordingly.

[0200] The stress sensitivity coefficients used in the production stage calculations listed above refer to the actual stress sensitivity coefficients determined on-site after applying the aforementioned prior constraints and production dynamic corrections. .

[0201] After production dynamic correction, the representative effective stress and dynamic effective flow conduction capacity of the two inversion units at different production stages are shown in Table 6 below.

[0202] Table 6

[0203] Taking the first stage as an example, after the initial stage following the return flow, when the nozzle enters a stable production period of 2 mm, the effective stress increases from 25.2 MPa to 29.8 MPa. The stress increment is: .

[0204] After the aforementioned prior constraints and production dynamic corrections, the actual on-site stress sensitivity coefficient for this effective stress range is 0.026 MPa. -1 ,but: .

[0205] During the production process, the dynamic effective flow conduction capacity of the first inversion unit gradually decreased from 17.3 D·cm at the beginning of the production stage to 10.2 D·cm at the end of the production stage; compared with the initial equivalent flow conduction capacity of 22.8 D·cm at the end of construction, the flow conduction capacity retention ratio at the end of the production stage was 44.7%.

[0206] The dynamic effective flow-carrying capacity of the second inversion unit gradually decreased from 18.8 D·cm at the beginning of the production stage to 12.6 D·cm at the end of the production stage; compared with the initial equivalent flow-carrying capacity of 27.2 D·cm at the end of construction, the flow-carrying capacity retention ratio at the end of the production stage was 46.3%.

[0207] Both inversion units exhibited a continuous decline in conductivity as production time increased. The conductivity retention ratio at the end of production in the second inversion unit was slightly higher than that at the beginning of construction.

[0208] A production model containing two fracture elements was established in INTERSECT. The dynamic conductivity of the first and second segments was used as inputs for fracture properties that change over time, and historical data was fitted using field production dynamics. The fitting targets included daily fluid production, daily oil production, water cut, and wellhead or bottomhole pressure during periods with pressure recording. Details are shown in Table 7.

[0209] Table 7

[0210] As shown in Table 7, the relative errors of cumulative liquid volume, cumulative oil volume, and representative pressure point are all at a low level. The established fracture dynamic conductivity model can reflect the dynamic changes in production of the target well well and can be used to evaluate the production contribution of the subsequent fracturing stage.

[0211] like Figure 4 As shown in (a), the simulated values ​​of the fitting indices, such as cumulative liquid volume, cumulative oil volume, initial pressure, intermediate pressure, final liquid volume, and final oil volume, are generally close to the measured values; Figure 4As shown in Figure (b), the relative errors of all fitting indices are less than 5%, with the largest relative error being 3.75%. The results indicate that after dynamically updating the effective conductivity of the cracks using the method of this invention, the model can better characterize the dynamic response at different production stages, thus verifying the rationality of the dynamic inversion results.

[0212] After fitting the production history, the model's cumulative oil production is consistent with the actual cumulative oil production. The baseline model's cumulative oil production is taken as: .

[0213] Keeping the reservoir geological parameters, production regime, and dynamic diversion state of another inversion unit unchanged, the dynamic effective diversion capacity of the target inversion unit is reduced respectively, and the production calculation is recalculated.

[0214] After reducing the effective flow capacity of the first inversion unit, the cumulative oil production during the evaluation period was 112.60 t. Therefore, the marginal production impact of the first inversion unit is: .

[0215] After reducing the effective conductivity of the second inversion unit, the cumulative oil production during the evaluation period was 126.80 t. Therefore, the marginal production impact of the second inversion unit is: .

[0216] The normalized marginal production contribution index of the two inversion units was further calculated.

[0217] The first inversion unit is: .

[0218] The second inversion unit is: .

[0219] The evaluation results of the effective flow guidance capacity and production contribution of the two inversion units throughout the entire process are shown in Table 8 below.

[0220] Table 8

[0221] Among them, the normalized marginal production contribution index Used to characterize the first [missing information] under current reservoir model, production regime, and dynamic fracture state conditions. The relative impact of changes in the conductivity of each inversion unit on the overall well production response is not equivalent to the actual segmented production ratio obtained directly from production logging.

[0222] The calculation results show that the first inversion unit has a larger construction scale, a larger fracture half-length and an larger effective support length, and its normalized marginal contribution to the overall well production response is higher than that of the second inversion unit. However, during long-term production, the conductivity of the first inversion unit decreased from 22.8 D·cm to 10.2 D·cm, and the long-term retention rate was 44.7%.

[0223] The second inversion unit has a relatively small construction scale, but its flow capacity at the end of production is still 12.6 D·cm, with a total retention rate of 46.3%. The long-term flow capacity retention is slightly higher than that of the first inversion unit.

[0224] The above results indicate that evaluating fracturing effectiveness solely based on total hydraulic fluid volume, total sand volume, fracture half-length, or fracture conductivity at a single moment is insufficient to fully reflect the actual effective state of the fracture after early closure and long-term production stress changes.

[0225] Using the method described above, the following can be obtained sequentially: .

[0226] The initial conductivity of the inversion unit is obtained by estimating the initial conductivity of the local initial conductivity state formed by fracturing construction through hydraulic resistance equivalence. Then, the initial effective conductivity state of the production stage is determined by utilizing the early production dynamics after the flowback is completed. Furthermore, the effective conductivity of the production stage dynamics is updated by considering the long-term effective stress history. Finally, the normalized marginal impact of different inversion units on the overall well production capacity is evaluated.

[0227] This enables continuous evaluation of the fracturing fractures in Well 22 of Block B from the "construction-formed state" to the "early effective state," then to the "long-term effective state" and "production contribution state," providing a basis for evaluating fracturing effectiveness, identifying inefficient fractures, adjusting production systems, and optimizing fracturing designs for similar wells in the future.

Claims

1. A method for dynamic inversion of effective fracture conductivity in fracturing wells based on multimodal monitoring data, characterized in that, Includes the following steps: (1) Initial equivalent conductivity determination stage at the end of fracturing operation S1. Establish a forward model for fracturing operations based on the geological data, geomechanical parameters, and fracturing operation data of the target well. S2. Historical data fitting was performed using construction pressure, displacement, and fluid volume in Kinetix software to determine the spatial distribution morphology of the fracturing fractures. S3. Based on the spatial distribution morphology of the fracturing fractures, the complex fracture network is divided into multiple fracture inversion units with independent flow characteristics. S4. After determining the spatial distribution morphology of the fracturing fractures, first determine the initial conductivity of the local fracture segment based on the proppant concentration and the effective stress in the fracture normal direction at different locations: ； in: For the first Within the first inversion unit The initial local flow capacity at the end of construction of a local crack segment; The concentration of proppant applied per unit crack area; The effective stress in the normal direction of the local crack at the end of construction; S5. Based on the equivalent relationship of hydraulic resistance during fracture flow, the conductivity of locally non-uniform fractures is converted into the initial equivalent conductivity at the inversion element scale: ； in: For the first Initial equivalent diversion capacity at the end of construction of each inversion unit; For the first The main flow path length of each inversion unit; For the first The length of each local crack segment; For the first Number of local crack segments within each inversion unit; S6. The initial equivalent conductivity of each inversion unit and its local fracture segment is correlated with the fracture spatial coordinates to form the initial equivalent conductivity field at the end of the hydraulic fracturing operation. (2) Effective flow guidance capacity correction stage during the backflow stage S1. Calculate the effective conductivity coefficient of the backflow; Effective conductivity coefficient of the backflow The calculation formula is as follows: ； in: After the return process is completed, the first Effective equivalent flow guiding capacity of each inversion unit; For the first Initial equivalent diversion capacity at the end of construction of each inversion unit; S2. For target wells with complete backflow test data: First, obtain dynamic data of the flowback stage of the target well; Then, maintain the fracture geometry, fracture spatial location, and initial proppant placement as determined in step (1); based on the fracturing construction forward model established in step (1), limit the free adjustment variables in the backflow stage to the backflow effective conductivity coefficients corresponding to each effective inversion unit; update the fracture flow parameters and calculate the simulated backflow dynamics; Finally, the objective function for the back-row stage is established: ； in: For the first Simulate the backflow response at each time point; For on-site return and observation response; For different dynamic data weighting coefficients, N is the total number of valid observation data points participating in the dynamic matching of the back-up; Adjust the effective conduction coefficient of the backflow stage so that the objective function of the backflow stage reaches the preset error requirement or obtains the optimal matching result, and obtain the effective equivalent conduction capacity of each inversion unit at the end of the backflow under the condition of having effective backflow data; S3. For target wells lacking continuous backflow or effective pressure recovery data: First, determine the effective flow correction coefficient for early production according to the following formula. : ； in: This is the effective equivalent flow guiding capacity obtained based on early production dynamic correction; For the first Initial equivalent diversion capacity at the end of construction of each inversion unit; Then, after the effective flow correction coefficient for early production is determined, the effective flow state of the corresponding inversion unit is corrected based on the initial equivalent flow capacity at the end of construction, so as to obtain the effective equivalent flow capacity after the return flow ends and before entering the long-term production stage. S4. Based on the type of on-site data, obtain the effective equivalent diversion capacity after the return flow is completed. This allows for the determination of the initial effective flow diversion capacity during the production phase. ； in: This represents the effective equivalent flow diversion capacity after the return flow is completed. After the return process is completed, the first Effective equivalent flow guiding capacity of each inversion unit; This is the effective equivalent flow guiding capacity obtained based on early production dynamic correction; (3) Inversion stage of dynamic and effective flow diversion capacity in the production stage S1, obtained in step (2) As the initial effective flow guiding capacity in the production stage; during the production process, the first Each inversion element corresponds to the change in crack pressure over production time; according to the effective stress principle, the effective stress normal to the crack surface is as follows: ； in: For the first Each inversion unit in time The normal effective stress; This represents the total normal stress on the crack surface. The representative fracture pressure of the inversion unit; This represents the effective stress coefficient of Biot. S2, adopting the method in the actual production stage Actual stress sensitivity coefficient of each inversion element Dynamic updates will be performed. The actual stress sensitivity coefficient of each inversion element is expressed as: ； in: For the first The inversion unit number Actual stress sensitivity coefficient for each effective stress range; This is a field correction factor; For the experimental conditions, the first The inversion unit number The conductivity attenuation coefficient within an effective stress range; S3. Introducing the historical maximum effective stress, defining the first... The historical maximum effective stress of each inversion element: ； in: For the first i The historical maximum effective stress of each inversion unit up to production time t; For the first i Each inversion unit at a historical moment τ The effective stress normal to the crack surface; τ For historical time variables that are no later than the current production time t; S4, in the Within each production stage, based on the stress sensitivity principle, the dynamic effective flow guidance capacity of each production stage is updated to... : ； in: For the first The inversion unit number Actual stress sensitivity coefficient for each effective stress range; For the first The production stage is in the first The effective stress change experienced within an effective stress range; S5. Correlate the dynamic effective conductivity of each inversion unit with its corresponding fracture spatial location to form the spatiotemporal distribution of effective fracture conductivity during the production stage, expressed as follows: ； in: Indicates the spatial location of the crack; Indicates production time; (4) Evaluation stage of crack production contribution S1. Based on the dynamic effective flow guiding capacity obtained in step (3) during the production process, establish a basic production model containing all effective crack elements. S2. Calculation method for marginal production response of single crack unit: Reduce the flow capacity of the target inversion unit to a set state; ； in: To reduce the first Dynamic and effective flow guidance capability after each inversion unit; The coefficient for reducing the flow capacity is a value that is not less than 0 and less than 1. S3. Recalculate the production dynamics through step S2 to obtain a reduction in the first step. Cumulative output after the flow-guiding capacity of each inversion unit ; Define the first Marginal production impact of each inversion unit : ； in: The cumulative output while maintaining the current dynamic diversion capacity for all inversion units; To reduce the first Cumulative output after the flow diversion capacity of each inversion unit; S4, Definition of the Normalized marginal production contribution index of each inversion unit : ； in: For the first The marginal production impact of each inversion unit; Because of the first j The cumulative decrease in overall well production caused by the weakening of the conductivity of each inversion unit; The number of effective crack inversion units; The range of values ; S5, at different production stages Calculate the normalized marginal production contribution index corresponding to each inversion unit according to the formula in step S4. ; By comparing the normalized marginal production contribution index of different inversion units at the same production stage, and analyzing the variation law of the contribution index of the same inversion unit at different production stages, dynamic advantage cracks are identified.

2. The method for dynamic inversion of effective fracture conductivity in fracturing wells based on multimodal monitoring data according to claim 1, characterized in that, In step (1), the proppant concentration in different fracture units is calculated based on the proppant mass conservation relationship; The proppant concentration for each fracture element is expressed as follows: ； In the formula: For the first The concentration of proppant applied to each fracture element; The mass of the proppant within the crack unit; This represents the effective area of ​​the crack.

3. The method for dynamic inversion of effective fracture conductivity in fracturing wells based on multimodal monitoring data according to claim 1, characterized in that, Each fracture inversion unit in step (1) includes fracture geometry, proppant concentration, initial fracture width, effective closure stress, and initial conductivity. The crack inversion unit is represented as follows: ; in: For the first One crack inversion unit; For the first The first inversion unit A localized crack segment; This represents the number of local cracks contained in the inversion unit.

4. The method for dynamic inversion of effective fracture conductivity in fracturing wells based on multimodal monitoring data according to claim 1, characterized in that, In step (3), under the experimental conditions, the first The inversion unit number Conductivity attenuation coefficient within an effective stress range The result is calculated using the following formula: ； in: The first obtained from the experiment The proppant conductivity attenuation coefficient within an effective stress range; and These represent the experimental conductivity under the corresponding effective stress conditions.

5. The method for dynamic inversion of effective fracture conductivity in fracturing wells based on multimodal monitoring data according to claim 1, characterized in that, In step (3) at the first Within the production time step, the first Effective stress increment of each inversion unit Represented as: ； In the first Within the production time step The historical maximum effective stress of each inversion unit; In the first Within the production time step The current effective stress of each inversion element.

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