A method for assessing the sand production risk of multi-level combined injection and production in sandstone oil and gas reservoirs.

Abstract

This invention belongs to the technical field of sand production control in oil and gas reservoir-type gas wells within the oil and gas extraction industry. Specifically, it provides a method for determining the sand production risk of multi-layered syngas injection and production wells in sandstone oil and gas reservoirs. By dividing multi-layered syngas injection and production wells into stratified evaluation units, the sand production susceptibility, pressure circulation disturbance, flow scour disturbance, and flow direction conversion disturbance of each stratified unit are characterized. This allows for the construction of a stratified sand production risk index, enabling the ranking, classification, and identification of the primary sand production risk strata at different strata. This invention can specifically characterize the differences in sand production risk among different reservoir layers under multi-layered syngas injection and production conditions in sandstone oil and gas reservoirs, providing a basis for optimizing injection and production systems, stratified sand control design, and sand production monitoring in syngas injection and production wells.

Description

Technical Field

[0001] This invention belongs to the field of sand production control technology for gas wells in oil and gas reservoirs in the oil and gas extraction industry, specifically involving a method for determining the sand production risk of multi-level combined injection and production in sandstone oil and gas reservoirs. Background Technology

[0002] Underground gas storage facilities are crucial for ensuring natural gas peak shaving, emergency gas supply, and energy security. Sandstone oil and gas reservoir-type gas storage facilities are mostly converted from depleted gas reservoirs, depleted oil reservoirs, or sandstone reservoirs with sealing capabilities. Unlike conventional oil and gas reservoirs that produce continuously in one direction, gas storage facilities undergo long-term cyclical gas injection and production: during the injection phase, gas enters the reservoir from the wellbore, increasing formation pressure; during the production phase, gas flows from the reservoir back to the wellbore, decreasing formation pressure. This repeated injection and production subject the near-wellbore reservoir to long-term fluctuations in pore pressure, gas flow scouring, and flow direction reversals, potentially inducing disturbances in the rock skeleton structure, particle loosening, fine particle migration, and pore throat blockage, thereby increasing the risk of sand production.

[0003] For multi-layered sandstone oil and gas reservoirs, a single well typically connects multiple reservoir layers simultaneously for combined injection and production. These layers differ in thickness, porosity, permeability, pressure level, cementation strength, and fine particle content. Under the same wellbore pressure, each layer contributes differently in terms of injection volume, production volume, pressure fluctuation amplitude, and gas scouring intensity. In multi-layered combined injection and production, differences in permeability, pressure level, and mobilization capacity exist between layers, with high-permeability or high-pressure layers potentially handling the majority of the flow. When there are significant differences in interlayer pressure and seepage capacity, interlayer crossflow or localized backflow may occur. Such reverse flow alters the near-wellbore particle migration direction, potentially inducing particle re-migration, pore throat blockage, and increasing the risk of secondary sand production during subsequent gas production.

[0004] Therefore, the sand production risk of multi-layer syngas storage facilities is not the average risk of a single reservoir, but is jointly controlled by the sand production susceptibility of each sub-layer and external injection-production disturbances. Determining the relative sand production risk of different sub-layers and identifying the layers with the primary sand production risk are problems that need to be solved in the safe operation and sand control design of multi-layer syngas storage facilities.

[0005] The existing technology has the following problems: (1) In multi-layered injection and production wells, the cementation strength, porosity, fine particle content, pressure response and flow distribution of each sub-layer are different. Existing methods mostly evaluate single or multiple layers as equivalent to a single reservoir, which is difficult to directly apply to multi-layered injection and production gas storage facilities. It is easy to cover up the real high-risk sub-layers and make it difficult to identify the main sand-producing layer.

[0006] (2) During the multi-layer combined injection and production process, different sub-layers are subjected to different pressure cycles, flow velocity scouring and flow direction conversion effects, and backflow or inter-layer interference may also occur in local layers. Existing conventional oil and gas reservoir sand production prediction methods or gas storage single-layer sand production evaluation methods are difficult to consider these stratification differences at the same time, which may lead to inaccurate judgment results and be detrimental to future stratification sand prevention decisions.

[0007] (3) The sand production rate at the wellhead of a combined injection and production well is the result of the combined action of multiple sub-layers and cannot directly represent the measured sand production of a single sub-layer. Existing methods lack a simple way to calibrate the results of stratified risk assessment using whole-well sand production monitoring data, which is not conducive to rapid on-site judgment and dynamic adjustment.

[0008] Therefore, there is an urgent need to establish a rapid sand production risk assessment method for multi-level injection and production conditions in sandstone oil and gas reservoirs, so as to achieve layered risk ranking, identification of the main sand production layer, and on-site sand production intensity calibration. Summary of the Invention

[0009] The purpose of this invention is to provide a method for determining the sand production risk of multi-level combined injection and production in sandstone oil and gas reservoirs. This method addresses the problem that existing methods for evaluating sand production from single-layer or equivalent reservoirs are insufficient to reflect the differences in sand production susceptibility of reservoirs during multi-level combined injection and production, as well as the impact of stratified pressure circulation disturbances, stratified flow velocity scouring disturbances, and flow direction conversion disturbances on sand production risk.

[0010] This invention does not simply apply conventional single-layer sand production evaluation methods to multiple reservoir sub-layers. Instead, it divides multi-layered injection-production wells into several stratified evaluation units, characterizing the sand production susceptibility, pressure circulation disturbance, flow scour disturbance, and flow direction conversion disturbance of each stratified unit. This allows for the construction of a stratified sand production risk index, enabling the ranking, classification, and identification of the primary sand production risk layers at different layers. Through this method, the invention can more effectively characterize the differences in sand production risk among different reservoir sub-layers under multi-layered injection-production conditions in sandstone oil and gas reservoirs, providing a basis for optimizing injection-production systems, stratified sand control design, and sand production monitoring in injection-production wells.

[0011] To achieve the above objectives, this invention proposes a method for assessing the sand production risk of multi-level combined injection and production in sandstone oil and gas reservoirs, comprising the following steps: S1. Basic parameters of stratified injection and production wells in sandstone oil and gas reservoirs. Based on the existing reservoir stratification results, well completion connectivity sections, and production interpretation data of sandstone oil and gas reservoirs with combined injection and production wells, the evaluation units for each stratum were determined. Basic parameters such as reservoir properties, reservoir rock mechanics, fluid properties, seepage, injection and production dynamics, wellbore time, and on-site sand production monitoring were collected for each stratum evaluation unit. This provides a data foundation for subsequent evaluations of the stratification susceptibility to sand production, pressure circulation disturbance, flow velocity scour disturbance, flow direction conversion disturbance, and stratification sand production risk.

[0012] Analysis of the sand-producing susceptibility of each layer in S2 sandstone oil and gas reservoir-type gas storage. Based on the initial cohesion or uniaxial compressive strength, porosity, and fine particle content of each stratified evaluation unit, the relative strength of cementation strength, skeleton looseness, and migratable particle content relative to the average level of multiple layers are characterized. The stratified sand production susceptibility is constructed by weighted product to analyze the sand production susceptibility caused by the reservoir properties of each layer.

[0013] S3, Characterization of the degree of stratified pressure circulation disturbance in combined injection and production wells of sandstone oil and gas reservoirs. Based on the formation pressure of each stratified evaluation unit during the gas injection and production stages, the pressure swing, average pressure level, and relative pressure disturbance intensity are first calculated, and then the average relative pressure disturbance intensity of each stratified unit is obtained; on this basis, the stratified unit is constructed. i Characteristic value of hierarchical pressure cyclic disturbance degree of each hierarchical evaluation unit , used to characterize the i The strength of the cyclical disturbances experienced by each stratified evaluation unit relative to the average level of the multi-level system.

[0014] S4, Characterization of the degree of stratified flow velocity scouring disturbance in sandstone oil and gas reservoir-type gas storage combined injection and production wells. S4.1 Based on the volumetric flow rate, wellbore radius, layer thickness and porosity of each layer evaluation unit in the gas injection and gas production stages, first calculate the actual near-wellbore gas velocity in the gas injection and gas production stages, and further obtain the strength of the circulating average near-wellbore velocity relative to the average level of multiple layers. S4.2. Based on the Forchheimer non-Darcy coefficient, gas density, permeability, gas kinematic viscosity and near-wellbore actual gas velocity, calculate the non-Darcy flow intensity during the gas injection and gas production stages, and obtain the strength of the evaluation unit's cyclic average non-Darcy flow intensity relative to the multi-layer average level. S4.3, Based on this, construct a characterization value for the degree of stratified flow velocity scouring disturbance. , used to characterize the i The strength of near-wellbore gas scouring and non-Darcy inertial disturbance experienced by each stratified evaluation unit relative to the multi-level average.

[0015] S5, Characterization of the degree of disturbance caused by the stratified flow direction conversion of the combined injection and production well in sandstone oil and gas reservoirs. S5.1. Based on the degree of bidirectional utilization of each stratified evaluation unit in the gas injection-gas production conversion process, first calculate the characteristic of the first... i The strength of the gas injection-gas production bidirectional utilization of each stratified evaluation unit relative to the average level of the multi-layer system; S5.2 Based on the local backflow flow ratio and the frequency of local backflow occurrence during the gas production stage, calculate and characterize the strength of the local backflow impact relative to the multi-level average during the gas production stage. S5.3, Based on this, construct a characterization value for the degree of disturbance of hierarchical flow direction conversion. , used to characterize the i The strength of the flow direction transformation and local backflow-induced sand production effect on each stratified evaluation unit relative to the multi-level average.

[0016] S6. Calculation of Sand Production Risk Index and Determination of Main Sand Production Layer in Combined Injection and Production Wells of Gas Storage S6.1 After obtaining the stratified sand production susceptibility, stratified pressure circulation disturbance, stratified flow velocity scour disturbance, and stratified flow direction conversion disturbance values ​​for each stratified evaluation unit, a comprehensive risk characterization value is first calculated to comprehensively characterize the reservoir's own sand production susceptibility and the combined effects of pressure circulation, flow velocity scour, and flow direction conversion disturbances. Then, the comprehensive risk characterization value is normalized by multi-level averaging to obtain the stratified sand production risk index, which is used to characterize the relative sand production risk among each stratified evaluation unit. Furthermore, based on the reference sand production rate and the wellhead measured sand production rate, a well-wide sand production intensity calibration coefficient is constructed, and the stratified sand production risk index is calibrated to obtain the calibrated stratified sand production risk index. S6.2 Finally, based on the stratified sand production risk index or the calibrated stratified sand production risk index, the risk ranking of each stratified evaluation unit is performed, and the stratified evaluation unit corresponding to the maximum value is determined as the main control sand production risk layer.

[0017] Specifically, the method for determining the sand production risk of multi-level combined injection and production in sandstone oil and gas reservoirs includes the following steps: S1. Basic parameters of stratified injection and production wells in sandstone oil and gas reservoirs. Based on the existing reservoir stratification results, well completion connectivity sections, and production interpretation data of sandstone oil and gas reservoir-type gas storage combined injection and production wells, the evaluation units of each stratum participating in the evaluation were determined, and basic parameters such as reservoir physical properties, reservoir rock mechanics, fluid physical properties, seepage, injection and production dynamics, wellbore time, and on-site sand production monitoring of each stratum evaluation unit were collected.

[0018] Establish a basic parameter set for each stratified evaluation unit. (Based on the first...) iTaking a stratified evaluation unit as an example, the basic parameter set includes reservoir physical property parameters, reservoir rock mechanical parameters, fluid physical property parameters, injection and production dynamic parameters, wellbore and time parameters, and field sand production monitoring parameters, as shown in Table 1.

[0019] Table 1. Basic Parameter Set for Risk Assessment Methods of Multi-level Co-injection and Co-production Sand Production in Sandstone Oil and Gas Reservoirs

[0020] The above parameters are used for subsequent evaluations of the degree of sand production in each stratum, evaluations of pressure circulation disturbance in each stratum, evaluations of flow velocity scouring disturbance in each stratum, evaluations of flow direction conversion disturbance in each stratum, and evaluations of sand production risk in each stratum.

[0021] S2, Characterization of the sand-producing susceptibility of each layer in sandstone oil and gas reservoir type gas storage. In this step, the initial cohesion is first used. The scientific principle behind cementation strength is that cohesion is one of the parameters of rock shear strength, reflecting the overall shear bond capacity formed by the cement, particle contact, and adhesion between sandstone particles. For weakly cemented sandstone reservoirs, the weaker the interparticle cementation, the lower the cohesion, and the more easily the reservoir experiences particle loosening and sand production under pressure cycling, flow scouring, and flow direction reversal disturbances.

[0022] use m i Indicates the first i The strength of the bonded unit relative to the average level of the multilayer is evaluated in terms of its layered strength: ; In the formula, n The number of hierarchical evaluation units for the connection of combined injection and production wells; For the first i Initial cohesion of each hierarchical evaluation unit, MPa; The average initial cohesion of all stratified evaluation units, in MPa; or, ; In the formula, For the first i Uniaxial compressive strength of each stratified evaluation unit, MPa; The average uniaxial compressive strength of all stratified evaluation units, in MPa.

[0023] When initial cohesion is used to characterize bond strength, the following methods are employed: Characterizing the first i The strength of the bond in each layer is evaluated relative to the average level of the multilayer, where: ; When initial cohesion is lacking When using uniaxial compressive strength To replace and adopt Characterizing the first i The strength of the bond in each layer is evaluated relative to the average level of the multilayer, where: .

[0024] Porosity is used to characterize the looseness of the granular framework because it reflects the degree of development of pore space within the rock. For sandstone reservoirs, under similar conditions, higher porosity generally indicates a looser granular framework, weaker intergranular contact and support, making them more susceptible to particle loosening, migration, and localized structural damage under injection-production pressure fluctuations and gas scouring. Therefore, porosity can be used to characterize the granular framework. Characterizing the first i The degree of skeleton looseness of each hierarchical evaluation unit relative to the average level of the multi-level system, where: ; In the formula, For the first i Porosity of each stratified evaluation unit, decimal; This is the average porosity of all stratified evaluation units, expressed as a decimal.

[0025] Using fine particle content Characterizing the content of migratable particles is based on the principle that fine particles are more easily initiated, migrated, and redeposited under the influence of gas flow. When the content of fine particles is high, phenomena such as fine particle migration, pore throat blockage, local unblocking, and restart are more likely to occur in the near-wellbore area. Therefore, using... Characterizing the first i The relative strength of transferable particles within each hierarchical evaluation unit to the multi-level average, where: ; In the formula, For the first i The fine-grained content of each stratified evaluation unit, in decimal form; This represents the average fine particle content across all stratified evaluation units, expressed as a decimal. The particle size of the fine particles is less than or equal to 0.063 mm.

[0026] Constructing a characterization value for the degree of sand production in layers , characterizing the iThe susceptibility to sand production in a stratified evaluation unit under the same external injection-production disturbance is determined by its own cementation strength, pore structure, and fine particle content. The scientific principle behind this is that reservoir sand production is not solely determined by external injection-production disturbances, but is also controlled by the rock's own resistance to particle stripping, the looseness of its framework, and the content of migrateable particles. Specifically, cementation strength determines how easily particles are stripped, pore structure affects the stability of the particle framework, and fine particle content influences the likelihood of particle initiation, migration, and re-initiation after blockage. Therefore, a weighted synthesis of these three factors can be used to characterize the relative differences in the susceptibility to sand production among different stratified evaluation units.

[0027] No. i Characteristic values ​​of sand-producing stratification of each stratified evaluation unit Determine by the following formula: ; In the formula, , and These are the weighting coefficients of cementation strength, porosity, and fine particle content on the degree of sand production in stratification, respectively, and they satisfy the following: .

[0028] In a preferred embodiment, the following may be taken: .

[0029] when When >1, it means the first i The sand production degree of each stratified evaluation unit is higher than the average level of multiple layers; when When ≈1, it indicates that the sand production of this layer is close to the average level of multiple layers; when When the value is less than 1, it indicates that the sand production of this layer is lower than the average level of multiple layers.

[0030] S3: Characterization of the degree of pressure circulation disturbance in the stratified pressure circulation of sandstone oil and gas reservoir-type gas storage combined injection and production wells During the cyclic injection and production process of a gas storage facility, reservoir pressure increases during the injection phase and decreases during the production phase. Different stratified evaluation units experience varying pressure fluctuations due to differences in permeability, connectivity, and pressure response. These pressure fluctuations cause changes in effective stress, which in turn affect the stability of the near-wellbore reservoir particle skeleton and the risk of sand production. Therefore, this step characterizes the relative strength of cyclic pressure disturbances experienced by different stratified evaluation units during the injection and production phases by analyzing the formation pressure changes in each stratified evaluation unit.

[0031] No. i Pressure swing of each stratified evaluation unit and average pressure level They are represented as follows: ; ; In the formula, For the first i Formation pressure (MPa) in each stratified evaluation unit during the gas injection stage; For the first i Formation pressure (MPa) in each stratified evaluation unit during the gas production stage.

[0032] To eliminate the influence of pressure level differences among different stratified evaluation units, the ratio of pressure swing amplitude to average pressure level is used to characterize the relative pressure disturbance intensity experienced by the stratum within an injection-production cycle: ; In the formula, For the first i The relative pressure disturbance intensity of each stratified evaluation unit is dimensionless. The scientific principle behind this is that the same pressure amplitude acting on reservoirs with different average pressure levels has different relative effects on effective stress changes and particle skeleton disturbances; therefore, compared to directly using pressure amplitude... , It can more reasonably reflect the differences in disturbances between reservoirs with different pressure levels.

[0033] To facilitate comparisons between different stratified evaluation units, a multi-layered average relative pressure disturbance intensity is defined. : ; Further adoption Characterizing the first i The strength of the cyclical stress disturbance experienced by each stratified evaluation unit relative to the average level of the multi-level system is denoted as follows: : ; In the formula, For the first i The dimensionless characterization value of the degree of cyclic perturbation of stratified pressure in each stratified evaluation unit. When, it indicates the first i The pressure cycle disturbance intensity experienced by each stratified evaluation unit is higher than the average level of the multi-layer system; when When, it indicates that the pressure cycle disturbance intensity of this layer is close to the average level of multiple layers; when When the value is less than the average level of multiple layers, it indicates that the pressure cycle disturbance intensity of that layer is lower than that of multiple layers.

[0034] S4, Characterization of the degree of stratified flow velocity scouring disturbance in sandstone oil and gas reservoir-type gas storage combined injection and production wells. During the combined injection and production process in a gas storage facility, the near-wellbore gas velocities vary among different stratified evaluation units due to differences in thickness, porosity, permeability, and volumetric flow rate. Higher gas velocities result in stronger dragging and scouring effects of the fluid on sandstone particles, making it easier to induce particle stripping, fine particle migration, and sand production. Therefore, this step characterizes the relative strength of velocity-induced scouring disturbances in different stratified evaluation units by using actual near-wellbore gas velocities and non-Darcy flow intensity.

[0035] The first under specified stratigraphic conditions i The volumetric flow rates of the gas injection and gas production stages in each stratified evaluation unit are as follows: and . No. i The near-wellbore actual gas velocities of each stratified evaluation unit during the gas injection and gas production stages are as follows: ; ; In the formula, and The first under the respective stratigraphic conditions i The volumetric flow rate (m³) of each stratified evaluation unit during the gas injection and gas production stages. 3 / s; Let be the radius of the wellbore, in meters (m). For the first i Each hierarchical evaluation unit has a layer thickness in meters. For the first i Porosity of each stratified evaluation unit, decimal.

[0036] To characterize the first i The overall velocity scouring intensity experienced by each stratified evaluation unit during an injection-production cycle is calculated, and the average near-wellbore velocity is determined. : ; And calculate the multi-layer average circulation near-wellbore velocity. : ; in, For the first i Actual near-wellbore gas velocity during the gas injection stage, m / s; For the first i Actual near-wellbore gas velocity during the gas production stage, m / s; The average near-wellbore flow velocity in the multi-layer circulation is , in m / s.

[0037] Further adoption Characterizing the first i The ratio of the near-wellbore gas velocity in each stratified evaluation unit to the average level of multiple layers indicates the strength of the velocity scouring effect experienced by that layer.

[0038] To characterize the effect of inertial effects on particle stripping and migration in high-speed gas flow, the following calculations were performed: i Non-Darcy flow intensity of each stratified evaluation unit during the gas injection and gas production phases , : ; ; In the formula, For the first i The Forchheimer non-Darcy coefficient of each hierarchical evaluation unit, m -1 ; and The gas density (kg / m³) under the pressure and temperature conditions during the injection and production stages of this layer, respectively. 3 ; For the first i The penetration rate of each stratified evaluation unit, m 2 ; and The first i Gas kinematic viscosity during the injection and extraction stages of each stratified evaluation unit, kg / (m·s); and These represent the non-Darcy flow intensities during the gas injection and gas production stages, respectively, and are dimensionless. The scientific principle behind this is that when the gas velocity is high, the near-wellbore flow no longer completely follows Darcy linear flow, and the inertial pressure drop gradually increases. A greater non-Darcy flow intensity indicates more significant gas inertial disturbance, and stronger instantaneous drag, disturbance, and stripping effects on particles, thus making it easier to induce fine particle migration and sand production.

[0039] No. i The cyclic average non-Darcy flow intensity of each stratified evaluation unit is: ; The average cyclic non-Darcy flow intensity of the multilayer is: ; Further adoption Characterizing the first i The strength of the non-Darcy flow intensity in each stratified evaluation unit relative to the average level of the multilayer.

[0040] Therefore, the first i Characteristic value of the degree of stratified flow velocity scouring disturbance in each stratified evaluation unit Determine by the following formula: ; In the formula, and These are the weighting coefficients for the cyclic average near-wellbore flow scouring and the cyclic average non-Darcy inertial effect, respectively. They are dimensionless and satisfy the following: .

[0041] Preferably, the and The determination was made based on indoor sand production experiments, historical sand production data from the field, and production dynamics inversion results.

[0042] More preferably, .

[0043] when When, it indicates the first i The stratified flow velocity scouring disturbance experienced by each stratified evaluation unit is stronger than the average level of the multi-layer flow; when When, it indicates the first i The stratified flow velocity scouring disturbance of each stratified evaluation unit is close to the average level of multiple layers; when When, it indicates the first i The stratified flow velocity scouring disturbance of each stratified evaluation unit is weaker than the average level of the multi-layer system.

[0044] S5, Characterization of the degree of disturbance caused by the stratified flow direction conversion of the combined injection and production well in sandstone oil and gas reservoirs. In the process of multi-level combined injection and production in sandstone oil and gas reservoirs, the evaluation units of each level will experience periodic flow reversals as the gas injection-production regime of the reservoir changes, as shown in the attached figure. Figure 1 As shown in the attached diagram. Simultaneously, during the gas production stage, due to differences in pressure response and seepage capacity among the various evaluation units, reverse flow from the wellbore to the reservoir may occur in local strata, i.e., localized backflow during the gas production stage, as illustrated in the attached diagram. Figure 2 As shown. Flow reversal causes repeated changes in the direction of fluid drag on near-wellbore particles, easily leading to particle loosening, rearrangement, and local restart. Therefore, this step characterizes the relative strength of flow reversal disturbances on different stratified evaluation units by the degree of bidirectional mobilization during the injection and production stages, and whether local backflow occurs during the production stage.

[0045] First, the following formula is used to represent the first... i The extent to which each stratified evaluation unit is utilized in both directions during the normal gas injection-gas production transition process: ; when hour, ; In the formula, For the first i The degree of bidirectional utilization of gas injection and gas production in each stratified evaluation unit is dimensionless. For the first i Actual near-wellbore gas flow velocity during the gas injection stage of each stratified evaluation unit, m / s; For the firsti Actual near-wellbore gas velocity during the gas production stage of each stratified evaluation unit, m / s.

[0046] The scientific principle behind the above formula is as follows: If a certain stratified evaluation unit is fully utilized in both the injection and production directions, and the near-wellbore velocities in both directions are similar, then the fluid drag direction experienced by the particles in that layer will undergo a relatively sufficient periodic reversal, resulting in a stronger flow direction conversion disturbance. If the layer is mainly utilized in a single stage, while the flow velocity is lower in the other stage, then the actual bidirectional flow disturbance it experiences is weaker. Therefore, The value range is 0-1. When the first... i When each stratified evaluation unit is fully utilized during both the gas injection and production stages, and the near-wellbore velocities in both directions are similar, Approaching 1; when the layer is primarily used in a single phase while the flow rate is very low in another phase. Close to 0.

[0047] No. i Local backflow rate ratio during the gas production stage of each stratified evaluation unit Determine by the following formula: ; in: ; ; In the formula, For the first i The cumulative local backflow volume during the gas production phase of each stratified evaluation unit, in m³ 3 ; For the first i The absolute value of the cumulative flow during the gas production stage of each stratified evaluation unit, in m 3 ; For the first stage of gas extraction m Within the time period, the first i The stratified flow of each stratified evaluation unit, m 3 / s; Let m be the duration of the m-th time interval, in seconds. This is the discriminant function for local backflow during the gas production stage, and it is dimensionless. When the gas production stage... m Within a time period When >0, =1; when When ≤0, =0. When When =0, take =0.

[0048] Further, the following formula is used to characterize the first... i Frequency of local backflow during the gas production stage in each stratified evaluation unit across multiple injection and production cycles: ; In the formula, For the first i The frequency of local backflow during the gas production stage of each stratified evaluation unit is dimensionless. In order to be in The injection and extraction cycle i The number of cycles of local backflow during the gas production stage of each stratified evaluation unit, dimensionless; The injection / mining cycle is dimensionless.

[0049] Therefore, adopt Characterizing the combined impact of local backflow volume and frequency during the gas production stage: .

[0050] The scientific principle behind this is that the impact of local backflow on sand production risk depends not only on the amount of backflow but also on whether it occurs repeatedly. When the amount of local backflow is large and the frequency of occurrence is high, the possibility of particle migration, pore throat blockage, and subsequent restart is higher; when local backflow is only occasional or the amount of backflow is small, its impact on the risk of stratified sand production is relatively weak.

[0051] To facilitate comparisons between different stratified evaluation units, the average values ​​for each stratification are calculated separately: ; ; In the formula, The degree of bidirectional utilization of multi-layer average gas injection and gas production is dimensionless. The degree of local backflow impact during the multi-layer average gas production stage is dimensionless.

[0052] Further adoption Characterizing the first i The strength of the gas injection-production bidirectional utilization of each stratified evaluation unit relative to the average level of the multi-layer system is determined by using... This characterizes the strength of the local backflow impact during the gas production stage of this layer relative to the average level of multiple layers. If... =0, then take =0; if =0 indicates that no local backflow occurred during the gas production stage in any of the stratified evaluation units, so take 0. =0.

[0053] No. i Characteristic value of the degree of disturbance of the hierarchical flow direction conversion in each hierarchical evaluation unit Determine by the following formula: ; In the formula, The sand amplification factor induced by the change in flow direction is dimensionless; , These are the weighting coefficients for institutional injection-production conversion disturbances and local backflow disturbances during the gas production stage, respectively. They are dimensionless and satisfy the following conditions: .

[0054] In a preferred embodiment, the following may be taken: .

[0055] Preferably, the The determination is based on indoor injection-production conversion sand production experiments, historical wellhead sand production monitoring data of gas storage facilities, production dynamic inversion results, or experience with similar reservoirs.

[0056] when When it is close to 1, it indicates that the first... i The injection-production conversion and local backflow-induced sand production effects on the stratified evaluation units are relatively weak; when When the value is greater than 1, it indicates that the layer is affected by the normal gas injection-gas production transition and / or local backflow during the gas production stage, and there is an additional risk of particle migration, pore throat blockage, restart after blockage, and secondary sand production. The larger the value, the higher the risk of sand production induced by changes in flow direction in that layer.

[0057] S6. Calculation of Sand Production Risk Index and Determination of Main Sand Production Layer in Combined Injection and Production Wells of Gas Storage S6.1 Calculation of Layered Sand Production Risk Index In obtaining the first i Characteristic values ​​of sand-producing stratification of each stratified evaluation unit Characterization value of the degree of stratified pressure cycle disturbance Characterization value of the degree of stratified flow velocity scouring disturbance Characterization value of the degree of disturbance of stratified flow direction conversion Then, construct the first i Layered sand production risk index of each layered evaluation unit It is used to characterize the relative sand production risk of each layer evaluation unit in the multi-level injection and extraction process due to the combined effects of pressure circulation, airflow scouring and flow direction conversion.

[0058] First, construct the first i Comprehensive risk characterization value of each hierarchical evaluation unit : ; In the formula, , , and These are the weighting coefficients for sand production susceptibility, pressure circulation disturbance, velocity scouring disturbance, and flow direction conversion disturbance, respectively. They are dimensionless and satisfy the following conditions: .

[0059] Preferably, the weights are adjusted based on the gas storage facility's operational phase, on-site sand production monitoring data, and indoor sand production simulation experiments. For example, when the gas storage facility primarily exhibits reservoir loosening induced by significant pressure fluctuations, the weights can be increased. When high-velocity gas extraction leads to more significant particle stripping, it can improve... When the local backflow and direction conversion effects are more pronounced during multi-layer commingling mining, it can improve... .

[0060] More preferably, .

[0061] right Perform multi-level average normalization to obtain the first... i Layered sand production risk index of each layered evaluation unit : ; in: ; Right now: .

[0062] A calibration coefficient for the sand production intensity of the entire well is constructed based on the sand production rate at the wellhead. : ; In the formula, The measured sand production rate at the wellhead is in meters. 3 / d; For reference sand output rate, m 3 / d.

[0063] The reference sand discharge rate is determined based on on-site management thresholds, historical sand discharge data, or sand control design standards.

[0064] when A value >1 indicates that the overall sand production intensity of the combined injection and production well is currently higher than the reference level; when When the value is less than 1, it indicates that the overall sand production intensity of the combined injection and production well is currently lower than the reference level.

[0065] Based on the calibration coefficient of sand production intensity of the whole well Risk index for stratified sand production Calibration was performed to obtain the first... i Calibration of the sand production risk index for each stratified evaluation unit : ; in, Used to characterize the i The relative risk of sand production in each stratified evaluation unit compared to other stratified evaluation units. Used to characterize the overall sand production intensity of combined injection and production wells. This indicates that under the constraint of the overall well sand production rate, the first... i The calibrated risk level of each stratified evaluation unit; this indicator is used for stratified risk ranking and identification of the main control sand production risk layer, and does not represent the measured sand production of the stratified evaluation unit.

[0066] S6.2 Determination of the main control sand production risk layer Under the conditions of multi-level combined injection and extraction, or The largest stratified evaluation unit was identified as the stratum controlling sand production risk. Among them, Primarily used for stratified relative risk ranking when there is no wellhead sand production rate data; Primarily used for post-calibration risk assessment when existing wellhead sand production rate monitoring data is available. If multiple stratified assessment units... If all values ​​are at a high level, it is determined that the combined injection and production well has a risk of multiple layers of sand production.

[0067] because Normalization using multi-level averages allows it to characterize the relative sand production risk between different stratified evaluation units. As an alternative approach: when When ≥1.15, it indicates that the first... i The relative sand production risk of each stratified evaluation unit is higher than the average level of multiple layers; When 1.15> When ≥0.85, it indicates that the first... i The relative sand production risk of each stratified evaluation unit is close to the average level of the multi-level evaluation units; when When, it indicates the first i The relative sand production risk of each stratified evaluation unit is lower than the average level of the multi-layer evaluation.

[0068] Furthermore, according to Risk classification is performed for each tiered evaluation unit. As an optional approach: when When <0.8, the first is determined to be... i Each stratified evaluation unit is a low-risk sand-producing layer; When 0.8≤ When <1.2, determine the first i Each stratified evaluation unit is a medium-risk sand production layer; When 1.2≤ When <1.5, determine the first i Each stratified evaluation unit is a high-risk layer for sand extrusion. when When ≥1.5, the first is determined. iEach stratified evaluation unit is a layer with extremely high sand production risk.

[0069] The above thresholds can be adjusted based on on-site sand discharge monitoring data, historical operating data, and sand control management requirements of the gas storage facility.

[0070] Through the above method, this invention can calibrate the sand production intensity of the entire well by using the sand production rate at the wellhead, based on the reservoir's own sand production properties, pressure circulation disturbance, flow velocity scour disturbance, and flow direction conversion disturbance. This enables the ranking of sand production risks in multi-layered injection and production wells and the identification of the main sand production risk layers, providing a basis for optimizing the injection and production system, designing layered sand control, and monitoring sand production.

[0071] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention takes each known sub-layer in the combined injection and production well as the sub-layer evaluation unit, and considers the differences in cementation strength, porosity, fine particle content, pressure response and flow distribution of each layer to sort and judge the risk of sand production in each layer, so as to avoid the problem of simply equating multiple reservoirs with a single reservoir and thus masking the problem of high-risk sub-layers.

[0072] (2) This invention characterizes the degree of sand production in each layer, the degree of pressure cycle disturbance in the layer, the degree of flow velocity scouring disturbance in the layer, and the degree of flow direction conversion disturbance in the layer. This allows the evaluation results to simultaneously consider factors such as the sand production probability, pressure cycle, flow velocity scouring, injection-production flow direction conversion, and local backflow during the gas production stage of each layer. This is beneficial for identifying the main sand production risk layer and providing a basis for layered sand prevention decisions.

[0073] (3) The present invention takes into account that the sand production rate at the wellhead of the combined injection and production well is the mixed result of the combined action of multiple small layers. Instead of directly using it as the measured sand production of a single layer, the present invention uses the measured sand production rate at the wellhead to construct the sand production intensity calibration coefficient of the whole well and calibrate the sand production risk index of the layer, thereby improving the ability to combine the evaluation results with the field monitoring data, and facilitating rapid on-site judgment and dynamic adjustment. Attached Figure Description

[0074] Figure 1 A schematic diagram illustrating the flow direction changes during the gas injection-gas extraction process in a gas storage facility; Figure 2 This is a schematic diagram of a partial backflow during the gas extraction stage of a sandstone gas storage facility. Detailed Implementation

[0075] Example 1 This embodiment uses a combined injection and production well in a sandstone oil and gas reservoir as an example. This well connects four sandstone reservoir layers, designated as Reservoir 1, Reservoir 2, Reservoir 3, and Reservoir 4. Based on existing well logging interpretation, production logging, well test interpretation, and completion connectivity data, all four reservoir layers are used as stratified evaluation units in the calculation. Table 2 lists the main input parameters used in this implementation case.

[0076] Table 2 Case Well Foundation Input Parameters

[0077] Other parameter values ​​are as follows: Gas density during injection and extraction phases: kg / m 3 , kg / m 3 ; Gas kinematic viscosity during the gas injection and gas extraction stages: kg / (m·s), kg / (m·s); Non-Darcy coefficient: ; Wellbore radius: =0.1m; Number of injection / collection cycles: N=20; Number of gas production cycles in which local backflow occurred in reservoir 2: =8; No local backflow occurred in reservoirs 1, 3, and 4, i.e. ; Measured sand production rate at the wellhead: =0.0055m 3 / d; Reference sand output rate: =0.005m 3 / d; Full well sand production strength calibration coefficient: .

[0078] Local backflow identification during the gas production stage is achieved by segmenting the flow rate by time period. Based on the formation flowmeter test data, reservoir 2 showed positive flow during certain time periods, indicating that gas was entering the reservoir from the wellbore in reverse, which was determined to be a local backflow during the gas production stage.

[0079] Cumulative local backflow during the gas production stage of reservoir 2: =0.012 m³; Absolute value of cumulative flow during the gas production stage of reservoir 2: =0.0223 m³; The local backflow rate ratio of reservoir 2 in this embodiment is calculated as follows: ; Its backflow frequency is: ; therefore: ; No local backflow occurred in other reservoirs, therefore: .

[0080] Calculate the first i Characteristic values ​​of sand-producing stratification of each stratified evaluation unit hour, ; Calculate the first i Characteristic value of the degree of stratified flow velocity scouring disturbance in each stratified evaluation unit hour, ; Calculate the first i Characteristic value of the degree of disturbance of the hierarchical flow direction conversion in each hierarchical evaluation unit hour, =0.3, .

[0081] According to the calculation methods of S2 to S5 of the present invention, the characterization values ​​of the degree of sand production by stratification are obtained respectively. Characterization value of the degree of stratified pressure cycle disturbance Characterization value of the degree of stratified flow velocity scouring disturbance Characterization value of the degree of disturbance of stratified flow direction conversion As shown in Table 3.

[0082] Table 3 Calculation results of the stratified evaluation coefficients for case wells

[0083] As can be seen from Table 3, reservoir 2 , and The high values ​​indicate that the reservoir is prone to sand production, and that it experiences strong pressure circulation disturbances and flow direction reversal disturbances. In particular, the localized backflow during the gas production stage of reservoir 2 further exacerbated the situation. It is significantly higher than that of other reservoirs.

[0084] Take the weight: ; Calculate the first i The comprehensive risk characterization value of each stratified evaluation unit was calculated, and then the stratified sand production risk index was calculated. The sand production rate at the wellhead was used for calibration. The calculation results are shown in Table 4.

[0085] Table 4. Risk Assessment Results of Sand Production in Case Wells

[0086] Note: The risk level threshold is an optional threshold and can be adjusted according to on-site management requirements.

[0087] As shown in Table 4, reservoir 2 has the highest risk index for stratified sand production and the highest risk index for calibrated stratified sand production. =1.180 and =1.300. Therefore, reservoir 2 is determined to be the main sand-producing risk layer of this multi-layered combined injection and production gas storage well, and should be a key monitoring and sand-control layer.

[0088] As can be seen from this embodiment, the present invention can quickly assess the risk of sand production in multi-layered gas storage wells based on limited stratified reservoir parameters, injection-production dynamic parameters, and wellhead sand production rate, and identify the main sand production risk layers, providing a basis for subsequent injection-production system optimization, key layer monitoring, and stratified sand control design.

Claims

1. A method for assessing the sand production risk of multi-level combined injection and production in sandstone oil and gas reservoirs, characterized in that... Includes the following steps: S1. Basic parameters of stratified injection and production wells in sandstone oil and gas reservoirs; Analysis of the sand-producing susceptibility of each layer in S2 sandstone oil and gas reservoir-type gas storage. Based on the initial cohesion / uniaxial compressive strength, porosity, and fine particle content of each stratified evaluation unit, the strength of cementation, skeleton looseness, and migratable particle content relative to the average level of the multilayer were obtained, and the characterization value of the degree of sand release in the stratification was constructed. S3, Characterization of the degree of stratified pressure circulation disturbance in combined injection and production wells of sandstone oil and gas reservoirs. Based on the formation pressure during the gas injection and gas production stages, the pressure swing amplitude and average pressure level are calculated to obtain the relative pressure disturbance intensity and construct a characterization value for the degree of layered pressure cycle disturbance. S4, Characterization of the degree of stratified flow velocity scouring disturbance in sandstone oil and gas reservoir-type gas storage combined injection and production wells. S4.

1. Based on the volumetric flow rate, wellbore radius, layer thickness and porosity of the gas injection and gas production stages, calculate the actual near-well gas velocity during the gas injection and gas production stages, and obtain the strength of the circulating average near-well velocity relative to the average level of the multilayer. S4.

2. Based on the Forchheimer non-Darcy coefficient, gas density, permeability, gas kinematic viscosity and near-wellbore actual gas velocity, calculate the non-Darcy flow intensity during the gas injection and production stages, and obtain the strength of the cyclic average non-Darcy flow intensity relative to the multi-level average. S4.3 Construct characterization values ​​for the degree of stratified flow velocity scouring disturbance; S5, Characterization of the degree of disturbance caused by the stratified flow direction conversion of the combined injection and production well in sandstone oil and gas reservoirs. S5.

1. Based on the actual near-wellbore gas flow rate during the gas injection and gas production stages, obtain the strength of the bidirectional gas injection-gas production utilization relative to the multi-layer average level. S5.

2. Based on the local backflow flow ratio and the frequency of local backflow during the gas production stage, obtain the strength of the local backflow impact relative to the multi-level average during the gas production stage. S5.3 Construct a characterization value for the degree of disturbance in the hierarchical flow direction conversion; S6. Calculation of Sand Production Risk Index and Determination of Main Sand Production Layer in Combined Injection and Production Wells of Gas Storage S6.1 Calculate the comprehensive risk characterization value, perform multi-level average normalization, and obtain the stratified sand production risk index; Based on the reference sand production rate and the measured sand production rate at the wellhead, a calibration coefficient for the sand production intensity of the whole well is constructed, and the stratified sand production risk index is calibrated to obtain the calibrated stratified sand production risk index. S6.

2. Based on the stratified sand production risk index or the calibrated stratified sand production risk index, the risk ranking of each stratified evaluation unit is determined, and the stratified evaluation unit corresponding to the maximum value is determined as the main control sand production risk layer.

2. The determination method according to claim 1, characterized in that, In step S2, use m i Indicates the first i The strength of the bonded unit relative to the average level of the multilayer is evaluated in terms of its layered strength: ； In the formula, n The number of hierarchical evaluation units for the connection of combined injection and production wells; For the first i Initial cohesion of each hierarchical evaluation unit, MPa; The average initial cohesion of all stratified evaluation units, in MPa; or, ； In the formula, For the first i Uniaxial compressive strength of each stratified evaluation unit, MPa; The average uniaxial compressive strength of all stratified evaluation units, in MPa; in, ； ； use Characterizing the first i The relative strength of the skeleton looseness of each stratified evaluation unit compared to the average level of the strata: ； In the formula, For the first i Porosity of each stratified evaluation unit, decimal; The average porosity of all stratified evaluation units, decimal. use Characterizing the first i The relative strength of transferable particles within each hierarchical evaluation unit compared to the multi-level average: ； In the formula, For the first i The fine-grained content of each stratified evaluation unit, in decimal form; The average fine particle content of all stratified evaluation units, decimal. No. i Characteristic values ​​of sand-producing stratification of each stratified evaluation unit : ； In the formula, , and These are the weighting coefficients of cementation strength, porosity, and fine particle content on the degree of sand production in stratification, respectively, and they satisfy the following: .

3. The determination method according to claim 1, characterized in that, In step S3, No. i Pressure swing of each stratified evaluation unit and average pressure level They are represented as follows: ； ； In the formula, For the first i Formation pressure (MPa) in each stratified evaluation unit during the gas injection stage; For the first i Formation pressure (MPa) in each stratified evaluation unit during the gas production stage; ； In the formula, For the first i The relative pressure disturbance intensity of each hierarchical evaluation unit, dimensionless; Define the multi-layered average relative pressure disturbance intensity : ； ； In the formula, For the first i The dimensionless characterization value of the degree of cyclic perturbation of stratified pressure in each stratified evaluation unit.

4. The determination method according to claim 1, characterized in that, In step S4.1, No. i The near-wellbore actual gas velocities of each stratified evaluation unit during the gas injection and gas production stages are as follows: ； ； In the formula, and The first under the respective stratigraphic conditions i The volumetric flow rate (m³) of each stratified evaluation unit during the gas injection and gas production stages. 3 / s; Let be the radius of the wellbore, in meters (m). For the first i Each hierarchical evaluation unit has a layer thickness in meters. For the first i Porosity of each stratified evaluation unit, decimal; Calculate the average near-wellbore velocity of the circulation : ； Calculate the average circulation near-wellbore velocity in multiple layers : ； in, For the first i Actual near-wellbore gas velocity during the gas injection stage, m / s; For the first i Actual near-wellbore gas velocity during the gas production stage, m / s; The average near-wellbore velocity for multi-layer circulation is given in m / s. In step S4.2, Calculate the first i Non-Darcy flow intensity of each stratified evaluation unit during the gas injection and gas production phases , : ； ； In the formula, For the first i The Forchheimer non-Darcy coefficient of each hierarchical evaluation unit, m -1 ; and The gas density (kg / m³) under the pressure and temperature conditions during the injection and production stages of this layer, respectively. 3 ; For the first i The penetration rate of each stratified evaluation unit, m 2 ; and The first i Gas kinematic viscosity during the injection and extraction stages of each stratified evaluation unit, kg / (m·s); and These represent the non-Darcy flow intensities during the gas injection and gas extraction phases, respectively, and are dimensionless. No. i The cyclic average non-Darcy flow intensity of each stratified evaluation unit is: ； The average cyclic non-Darcy flow intensity of the multilayer is: ； In step S4.3, No. i Characteristic value of the degree of stratified flow velocity scouring disturbance in each stratified evaluation unit : ； In the formula, and These are the weighting coefficients for the cyclic average near-wellbore flow scouring and the cyclic average non-Darcy inertial effect, respectively. They are dimensionless and satisfy the following: .

5. The determination method according to claim 1, characterized in that, In step S5.1, ； when hour, ; In the formula, For the first i The degree of bidirectional utilization of gas injection and gas production in each stratified evaluation unit is dimensionless. For the first i Actual near-wellbore gas flow velocity during the gas injection stage of each stratified evaluation unit, m / s; For the first i Actual near-wellbore gas velocity during the gas production stage of each stratified evaluation unit, m / s; ； In the formula, The degree of bidirectional utilization of multi-layer average gas injection and gas production is dimensionless. In step S5.2, No. i Local backflow rate ratio during the gas production stage of each stratified evaluation unit : ； in: ； ； In the formula, For the first i The cumulative local backflow volume during the gas production phase of each stratified evaluation unit, in m³ 3 ; For the first i The absolute value of the cumulative flow during the gas production stage of each stratified evaluation unit, in m 3 ; For the first stage of gas extraction m Within the time period, the first i The stratified flow of each stratified evaluation unit, m 3 / s; Let m be the duration of the m-th time interval, in seconds. This is a dimensionless discriminant function for local backflow during the gas extraction stage. During the gas extraction stage m Within a time period When >0, =1; when When ≤0, =0; when When =0, take =0; No. i The frequency of local backflow during the gas production stage in each stratified evaluation unit across multiple injection and production cycles. : ； In the formula, For the first i The frequency of local backflow during the gas production stage of each stratified evaluation unit is dimensionless. In order to be in The injection and extraction cycle i The number of cycles of local backflow during the gas production stage of each stratified evaluation unit, dimensionless; This refers to the number of injection-extraction cycles, dimensionless. use Characterizing the combined impact of local backflow volume and frequency during the gas production stage: ； ； In the formula, The degree of local backflow impact during the multi-layer average gas production stage is dimensionless. In step S5.3, No. i Characteristic value of the degree of disturbance of the hierarchical flow direction conversion in each hierarchical evaluation unit : ； when When =0, =0; when When =0, =0; In the formula, The sand amplification factor induced by the change in flow direction is dimensionless; , These are the weighting coefficients for institutional injection-production conversion disturbances and local backflow disturbances during the gas production stage, respectively. They are dimensionless and satisfy the following conditions: .

6. The determination method according to claim 1, characterized in that, In step S6.1, Construct the first i Comprehensive risk characterization value of each hierarchical evaluation unit : ； In the formula, , , and These are the weighting coefficients for sand production susceptibility, pressure circulation disturbance, velocity scouring disturbance, and flow direction conversion disturbance, respectively. They are dimensionless and satisfy the following conditions: ; right Perform multi-level average normalization to obtain the first... i Layered sand production risk index of each layered evaluation unit : ； A calibration coefficient for the sand production intensity of the entire well is constructed based on the sand production rate at the wellhead. : ； In the formula, The measured sand production rate at the wellhead is in meters. 3 / d; For reference sand output rate, m 3 / d; No. i Calibration of the sand production risk index for each stratified evaluation unit : ； S6.2 Determination of the main control sand production risk layer Under the conditions of multi-level combined injection and extraction, or The largest stratified evaluation unit was determined to be the stratum with the main control sand production risk. in, Stratified relative risk ranking for use when there is no wellhead sand production rate data; Post-calibration risk assessment when existing wellhead sand production rate monitoring data is available.

7. The determination method according to claim 6, characterized in that, when When ≥1.15, it indicates that the first... i The relative sand production risk of each stratified evaluation unit is higher than the average level of multiple layers; When 1.15> When ≥0.85, it indicates that the first... i The relative sand production risk of each stratified evaluation unit is close to the average level of the multi-level evaluation units; when When, it indicates the first i The relative sand production risk of each stratified evaluation unit is lower than the average level of the multi-layer evaluation.

8. The determination method according to claim 6, characterized in that, when When <0.8, the first is determined to be... i Each stratified evaluation unit is a low-risk sand-producing layer; When 0.8≤ When <1.2, determine the first i Each stratified evaluation unit is a medium-risk sand production layer; When 1.2≤ When <1.5, determine the first i Each stratified evaluation unit is a high-risk layer for sand extrusion. when When ≥1.5, the first is determined. i Each stratified evaluation unit is a layer with extremely high sand production risk.

9. The determination method according to claim 1, characterized in that, The reference sand discharge rate is determined based on on-site management thresholds, historical sand discharge data, or sand control design standards.

10. The determination method according to claim 1, characterized in that, Step S1 is as follows: Based on the existing reservoir stratification results, well completion connectivity sections, and production interpretation data of the sandstone oil and gas reservoir-type gas storage and injection / production wells, determine the evaluation units of each stratification participating in the evaluation, and collect the basic parameters of each evaluation unit. The basic parameters include reservoir properties, reservoir rock mechanics, fluid properties, seepage, injection-production dynamics, wellbore time, and field sand production monitoring parameters.

Images