A method for identifying and quantitatively characterizing dead water

Abstract

The application discloses a method for identifying and quantitatively characterizing invalid water, and advantage injection-production well groups, layer positions and directions are accurately identified by combining dynamic and static data to establish a comprehensive evaluation index. Further, by combining micro-pore structure research, the distribution of large channels in the reservoir is determined, and the volume of the advantage channels is quantitatively calculated. Finally, by combining dynamic and monitoring data analysis, the change of water flow and swept volume fraction of injection-production channels at different stages is understood, and the quantitative characterization of invalid water bodies is realized, thereby laying a foundation for targeted tapping potential and treatment.

Description

Technical Field

[0001] This invention relates to the field of invalid water identification and quantitative characterization, and specifically to a method for invalid water identification and quantitative characterization. Background Technology

[0002] After old oilfields enter the stage of high water cut and high recovery, due to factors such as reservoir heterogeneity, water injection development and later transformation, different types of underground dominant channels are formed, developed and stabilized, ineffective water circulation is serious, and the horizontal and vertical utilization is uneven, resulting in adverse effects such as reduced water drive efficiency and reduced swept volume.

[0003] Existing technologies cannot accurately determine the specific layer and direction of ineffective water, nor can they quantitatively calculate the volume of dominant channels, the flow rate of water in stages, or quantitatively characterize ineffective water bodies. Summary of the Invention

[0004] To address the aforementioned issues, this invention establishes a dynamic and static comprehensive evaluation index based on a layered understanding, accurately identifying advantageous injection-production well groups, ineffective injection-production layers, and directions. Furthermore, by combining dynamic and monitoring data analysis, it understands the changes in water flow, water drive velocity, and swept volume components in the injection-production channel at different stages, thereby achieving a quantitative characterization of ineffective water volume.

[0005] This invention provides a method for identifying and quantifying ineffective water to address the problems of severe ineffective water circulation and uneven utilization in both planar and longitudinal directions. The technical solution is as follows:

[0006] A method for identifying and quantifying invalid water includes the following steps:

[0007] (1) Based on the results of hierarchical understanding, carry out the identification of the advantageous injection-production relationship of well, layer, and direction;

[0008] (2) Based on step (1), key water wells, key oil wells, and key well groups are identified. Wells with high cumulative injection and water absorption index are key water wells; wells with high production index and comprehensive water content are key oil wells; and well groups containing key oil wells and water wells are key well groups.

[0009] (3) Based on step (2), determine the key layers;

[0010] (4) Based on the above step (3), determine the dominant injection and production direction. The direction of the key oil well corresponding to the key water well is the dominant injection and production direction.

[0011] (5) Based on the results obtained in steps (2), (3) and (4), the volume of ineffective water is quantitatively calculated using the inter-well flow rate and velocity.

[0012] Furthermore, step (1) includes: comprehensively collecting data from coring, monitoring, logging interpretation, and development dynamics, and combining static and dynamic data to carry out injection-production splitting and stratification at the single sand body scale, and clarifying the stratification utilization and production status.

[0013] Furthermore, step (2) includes: using the results of step (1), through normalized comparison of well groups, and by comprehensively analyzing historical cumulative injection output and current water absorption and production index, identifying key water wells, key oil wells, and key well groups with advantageous injection-production relationships.

[0014] Furthermore, step (3) includes: based on the key water wells, key oil wells and key well groups determined in step (2) above, the identification of key advantageous injection and production layers is guided by the dynamic and static development parameters of oil wells and water wells combined with the evaluation of layered cumulative injection and the current injection production and water cut status. The main geological and development factors affecting the formation of advantageous channels are selected by using fuzzy identification method. Based on the comprehensive evaluation of dynamic and static indicators and dynamic indicators, the indicator weights are optimized to obtain a comprehensive evaluation index.

[0015] Furthermore, static indicators reflect the reservoir's sedimentary, physical properties, connectivity, and heterogeneous anisotropy, and specifically include: permeability, sandstone thickness, permeability gradient, coefficient of variation, protrusion coefficient, porosity, and clay content.

[0016] Furthermore, dynamic indicators reflect the dynamic response to changes in reservoir seepage characteristics, specifically including: cumulative fluid production intensity, fluid production index, overall water cut, water injection ratio, water absorption index, and stage water channeling coefficient.

[0017] Furthermore, step (4) includes: using the results of step (3), establishing a quantitative calculation method for the comprehensive index of the dominant channel, a dynamic and static combined comprehensive evaluation, and identifying the dominant direction between wells with a single sand body as the unit.

[0018] Furthermore, the quantitative calculation method for the comprehensive index is as follows: Comprehensive Index = Static Index (Sandstone Thickness * 0.3 + Porosity * 0.1 + Permeability * 0.3 + Breakthrough Coefficient * 0.3) * 0.5 + Dynamic Index (Water Saturation * 0.5 + Inter-well Water Flow Ratio * 0.5) * 0.5;

[0019] Among them, oil saturation can be directly monitored at the oil production site, and water saturation is obtained by subtracting oil saturation from 1.

[0020] Furthermore, step (5) includes: based on the conclusions obtained from steps (2), (3) and (4), combined with the tracer or numerical simulation tracer and the dynamic reaction of water channeling in the field, the advance speed of the water drive front and the water flow rate between stages can be obtained, and the dynamic ineffective water volume can be quantitatively calculated.

[0021] The inter-well water flow rate is defined as the volume of water flowing from the injection well to the production well and being extracted from the production well during a specific development period.

[0022] Time required for one ineffective water circulation = injection-production well distance / water drive front advance speed;

[0023] Ineffective water volume = inter-well flow rate × time required for one cycle of ineffective water.

[0024] The advantages of this invention compared to the prior art are:

[0025] This invention utilizes fuzzy recognition to select the main geological and development parameters affecting the formation of dominant channels and ineffective injection-production cycles, optimizes the index weights, derives a comprehensive evaluation index, and identifies key ineffective water-bearing well layers. The main geological parameters include permeability, effective thickness, and range; the development parameters include oil well production index, cumulative production intensity, and overall water cut; and water well water absorption index, water injection ratio, and water channeling coefficient.

[0026] This invention introduces the concepts of inter-well water flow rate and inter-well water flow ratio to determine ineffective injection-production directions. It uses the water drive front advance velocity and inter-well water flow rate to quantitatively calculate the dynamic ineffective water volume.

[0027] In response to the problems of highly dispersed and hidden underground residual oil during the ultra-high water-cut period, and the great difficulty in tapping potential, a relatively complete research system for identifying advantageous channels and quantifying ineffective water has been formed, based on the idea of ​​finding water and identifying ineffective water, thereby guiding the tapping potential of residual oil. This lays the foundation for targeted tapping and remediation.

[0028] Compared with existing technologies, this invention can quantitatively calculate the volume of dominant channels, the flow rate of water in stages, and quantitatively characterize ineffective water bodies. The innovative results are obvious and the level of advancement is high. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the inventive steps in this invention;

[0030] Figure 2 It refers to the different levels and layers of stratification and utilization.

[0031] Figure 3 This is a flowchart of the calculation process for the comprehensive index of the advantageous channel;

[0032] Figure 4 This is a composite flow chart of the layered ineffective injection and extraction index. Detailed Implementation

[0033] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0034] Example 1

[0035] like Figure 1 As shown, a method for identifying and quantifying invalid water includes the following steps:

[0036] (1) Based on the results of hierarchical understanding, carry out the identification of the advantageous injection-production relationship of well, layer, and direction;

[0037] (2) Based on step (1), key water wells, key oil wells, and key well groups are identified. Wells with high cumulative injection and water absorption index are key water wells; wells with high production index and comprehensive water content are key oil wells; and well groups containing key oil wells and water wells are key well groups.

[0038] (3) Based on step (2), determine the key layers;

[0039] (4) Based on the above step (3), determine the dominant injection and production direction. The direction of the key oil well corresponding to the key water well is the dominant injection and production direction.

[0040] (5) Based on the results obtained in steps (2), (3) and (4), the volume of ineffective water is quantitatively calculated using the inter-well flow rate and velocity.

[0041] Step (1) includes:

[0042] Based on data from coring, monitoring, well logging interpretation, and development dynamics, we will conduct injection-production segmentation and stratification at the single sand body scale by combining static and dynamic analysis, and clarify the stratification utilization and production status.

[0043] By applying the seepage resistance coefficient method and taking the injection-production balance of the well group as the basis, the plane distribution coefficient and vertical splitting coefficient are scientifically calculated by combining dynamic and static methods to achieve reasonable splitting of injection, production, fluid and oil, thereby quantifying the layered injection and production status of oil and water wells and obtaining key parameters such as inter-well water flow ratio, cumulative injection, cumulative production, comprehensive water cut, water absorption index and production index. Figure 2 It shows the production and utilization status of layered injection at the single sand body scale.

[0044] The inter-well water flow ratio is defined as the ratio of the cumulative inter-well water flow volume in all directions to the pore volume of the oil layer.

[0045] Step (2) includes:

[0046] Using the results of step (1), by normalizing the comparison of well groups, and by comprehensively analyzing the historical cumulative injection output and the current water absorption and production index, key water wells, key oil wells, and key well groups with advantageous injection-production relationships are identified.

[0047] Water wells: Table 1 shows the water absorption index calculated based on historical cumulative injection data and current injection volume and oil pressure to identify key injection wells.

[0048] Oil wells: Table 2 shows the production index calculated based on historical cumulative production and current fluid production and flowing pressure to identify key producing wells.

[0049] Table 1. Statistics on water injection in some well groups

[0050]

[0051] Table 2. Statistics on the output of some well groups

[0052]

[0053] Step (3) includes:

[0054] Based on the determination of key water wells, key oil wells and key well groups in step (2) above, the identification of key advantageous injection and production layers is guided by the dynamic and static development parameters of oil wells and water wells, combined with the evaluation of stratified cumulative injection and the current injection production and water cut status.

[0055] The fuzzy recognition method was used to select the main geological and development factors influencing the formation of advantageous channels. Based on a comprehensive evaluation combining dynamic and static indicators, the indicator weights were optimized to derive a comprehensive evaluation index, such as... Figure 3 As shown, the dominant orientation between wells is identified using a single sand body as the unit.

[0056] Among them, static indicators reflect the main geological control factors of reservoirs, such as sedimentation, physical properties, connectivity, and heterogeneous anisotropy. Specifically, they include: permeability, sandstone thickness, permeability gradient, coefficient of variation, protrusion coefficient, porosity, and clay content.

[0057] Dynamic indicators reflect the dynamic response of reservoir seepage characteristics, specifically including: cumulative fluid production intensity, fluid production index, comprehensive water cut, water injection ratio, water absorption index, and stage water channeling coefficient.

[0058] Step (4) includes:

[0059] Using the results of step (3), a quantitative calculation method for the comprehensive index of the dominant channel is established, and a comprehensive evaluation combining dynamic and static methods is performed to identify the dominant direction between wells with a single sand body as the unit. The specific implementation method is to assign different weights to different indicators based on their contribution to the dominant channel.

[0060] Comprehensive Index = Static Index (Sandstone Thickness * 0.3 + Porosity * 0.1 + Permeability * 0.3 + Breakthrough Coefficient * 0.3) * 0.5 + Dynamic Index (Water Saturation * 0.5 + Inter-well Water Flow Ratio * 0.5) * 0.5

[0061] Among them, oil saturation can be directly monitored at the oil production site, and water saturation is obtained by subtracting oil saturation from 1.

[0062] Once the inter-well water flow ratio reaches a certain value, the dominant channel becomes stable, resulting in high liquid production and high water cut at the production end, leading to ineffective water circulation. At this point, the dominant injection-production direction between wells is determined based on the size of the inter-well water flow ratio.

[0063] Step (5) includes:

[0064] Based on the conclusions obtained in steps (2), (3), and (4), and combined with the tracer or numerical simulation tracer and the dynamic reaction of water channeling in the field, the advance speed of the water drive front and the water flow rate between stages can be obtained, and the dynamic ineffective water volume can be quantitatively calculated.

[0065] As the dominant channel forms and develops, it reaches a stable state after achieving a certain inter-well water flow ratio. In several typical wells, the water intake profiles show that as the cumulative water flow ratio increases, the water intake thickness decreases, but the water intake intensity increases. The water drive velocity within the channel accelerates, while the swept volume component decreases. Ultimately, this results in high water cut and high production, with injected water repeatedly short-circuiting at both injection and production ends, no longer increasing water storage or playing a role in swept-up oil displacement, thus forming ineffective water circulation. After the generation of ineffective excess water, tracers and dynamic reactions are used to determine the water drive front advance velocity, the staged inter-well water flow, and the size of the dynamic ineffective water volume, i.e., the volume of the fully developed channel.

[0066] The inter-well water flow rate is defined as the volume of water flowing from the injection well to the production well and being extracted from the production well during a specific development period.

[0067] Time required for one ineffective water circulation = injection-production well distance / water drive front advance speed;

[0068] Ineffective water volume = inter-well flow rate × time required for one cycle of ineffective water.

[0069] Example 2

[0070] Figure 4 The current flow chart is used to overlay the ineffective injection-production comprehensive index of the 7.2 sublayer of the X7-015.2 well group. In accordance with Example 1, ineffective water identification and quantitative characterization are carried out.

[0071] First, key wells were identified by comparing well groups as units and normalizing the data. Through comparison of cumulative injection and water absorption index, water well X7-015.2 was identified as a key ineffective water injection well. Based on the comparison of cumulative water production, fluid production index, comprehensive water cut normalization, and comprehensive index of dominant channels of the X7-015.2 well group, oil well X7-15.1 was identified as a key ineffective water production well.

[0072] Secondly, based on the results of the longitudinal injection and production splitting in the plane and the dynamic and static development parameters, the layered advantages of the injection and production relationship of the well group were comprehensively evaluated, and the No. 7.2 sub-layer of the X7-015.2 well group was identified as the key layer for ineffective water circulation. Through comprehensive analysis of the inter-well water flow ratio, it was determined that the ineffective water direction of the oil well X7-15.1 mainly came from the X7-015.2 water well.

[0073] Finally, using the water drive front advance velocity and the inter-well flow rate in each stage, the volume of ineffective water was quantitatively calculated. Based on the injection-production splitting results, the inter-layer flow rate of water well X7-015.2 in the direction of oil well X7-15.1 at sub-layer 7.2 was 6.8 m. 3 The tracer statistics show that the advance rate of the water drive front between the two wells is 8 m / d, and the distance between the oil and water wells is 108 m. Therefore, the ineffective water volume = 6.8 × (108 / 8) = 91.8 m³. 3 .

[0074] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for identifying and quantifying invalid water, characterized in that, Includes the following steps: (1) Based on the results of hierarchical understanding, carry out the identification of the dominant injection-production relationship of well, layer, and direction; (2) Based on the above step (1), key water wells, key oil wells, and key well groups are identified. Wells with high cumulative injection and water absorption index are key water wells; wells with high production index and comprehensive water cut are key oil wells; and well groups containing key oil wells and water wells are key well groups. (3) Based on step (2), determine the key strata; (4) Based on the above step (3), determine the dominant injection and production direction. The direction of the key oil well corresponding to the key water well is the dominant injection and production direction. Using the results of step (3), a quantitative calculation method for the comprehensive index of the dominant channel is established, and a comprehensive evaluation combining dynamic and static methods is performed to identify the dominant directions between wells with a single sand body as the unit. The quantitative calculation method for the comprehensive index is as follows: Comprehensive Index = Static Index * 0.5 + Dynamic Index * 0.5 = (Sandstone Thickness * 0.3 + Porosity * 0.1 + Permeability * 0.3 + Breakthrough Coefficient * 0.3) * 0.5 + (Water Saturation * 0.5 + Inter-well Water Flow Ratio * 0.5) * 0.5; Among them, the oil saturation can be directly monitored at the oil production site, and the water saturation is obtained by subtracting the oil saturation from 1; (5) Based on the results obtained in steps (2), (3), and (4), the volume of ineffective water is quantitatively calculated using the inter-well flow rate and velocity. Based on the conclusions obtained in steps (2), (3) and (4), and combined with the tracer or numerical simulation tracer and the dynamic reaction of water channeling in the field, the advance speed of the water drive front and the water flow rate between stages can be obtained, and the dynamic ineffective water volume can be quantitatively calculated. The inter-well water flow rate is defined as the volume of water flowing from the injection well to the production well and being extracted from the production well during a specific development period. Time required for one ineffective water circulation = injection-production well distance / water drive front advance speed; Ineffective water volume = inter-well flow rate × time required for one cycle of ineffective water.

2. The method for identifying and quantifying invalid water as described in claim 1, characterized in that, The step (1) includes: taking into account data from coring, monitoring, logging interpretation, and development dynamics, and combining static and dynamic data to carry out injection-production splitting and stratification at the single sand body scale, and clarifying the stratification utilization and production status.

3. The method for identifying and quantifying invalid water as described in claim 1, characterized in that, Step (2) includes: using the results of step (1), through normalization comparison of well groups, and comprehensive analysis of historical cumulative injection output and current water absorption and production index, identifying key water wells, key oil wells, and key well groups with advantageous injection-production relationships.

4. The method for identifying and quantifying invalid water as described in claim 1, characterized in that, Step (3) includes: based on the key water wells, key oil wells and key well groups determined in step (2) above, the identification of key advantageous injection and production layers is guided by the dynamic and static development parameters of oil wells and water wells combined with the evaluation of layered cumulative injection and current injection production and water cut status. The main geological and development factors affecting the formation of advantageous channels are selected by using fuzzy identification method. Based on the comprehensive evaluation of dynamic and static indicators and dynamic indicators, the indicator weights are optimized to obtain a comprehensive evaluation index.

5. The method for identifying and quantifying invalid water as described in claim 4, characterized in that, Static indicators specifically include: permeability, sandstone thickness, permeability gradient, coefficient of variation, protrusion coefficient, porosity, and clay content.

6. The method for identifying and quantifying invalid water as described in claim 4, characterized in that, The dynamic indicators specifically include: cumulative liquid extraction intensity, liquid extraction index, comprehensive water content, water injection ratio, water absorption index, and stage water channeling coefficient.

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