Method and apparatus for determining a concealed partition

Abstract

The application discloses a method for determining hidden interlayer, which comprises the following steps: determining the permeability limit of non-production layer and the permeability limit of non-permeable layer of a perforated section respectively; then, determining the thickness weighted permeability of abnormal layer section of formation pressure gradient caused by interlayer according to the two limit values; finally, determining the identification standard of interlayer according to the permeability value, and identifying the interlayer in a non-coring well. The application creatively proposes to take the permeability as the main parameter for identifying the hidden interlayer, and originally establishes the way of "dynamic and static mathematical statistics-permeability threshold value determination-threshold value cutting" to identify the interlayer, compared with the conventional research thought "coring well identification-logging calibration-non-coring well interpretation". The new research thought avoids the problem of weak logging response of the interlayer, and sets the interlayer identification standard based on the permeability by setting the permeability of logging interpretation, so that the accurate identification of the interlayer in the non-coring well can be realized.

Description

Technical Field

[0001] This invention relates to the field of carbonate reservoir characterization technology, and in particular to a method and apparatus for determining hidden interlayers and their sealing properties using a combination of dynamic and static data in bioclastic limestone reservoirs. Background Technology

[0002] Interlayers are a collective term for both interlayers and strata. "Hiddenness" refers to the diverse geological origins, complex petrophysical characteristics, weak geophysical response, large variations in thickness, and unclear spatial distribution patterns of interlayers. This makes characterization difficult and highly uncertain, leading to discrepancies between the sealing properties of interlayers and geological predictions during reservoir development. Specifically, geologically identified interlayers may still experience seepage and vertical channeling during water injection, while geologically considered non-interlayers may provide effective containment. Hidden interlayers are commonly found in the vast, thick carbonate reservoirs of the Middle East. The strong vertical heterogeneity of these reservoirs necessitates layered development as an effective strategy for balanced reserve utilization and enhanced oil recovery. Interlayers are crucial geological bases for development layer division, not only subdividing the massive, heterogeneous strata into independent and homogeneous development units but also controlling the direction of injected water migration and suppressing vertical water channeling. Effective identification and sealing property evaluation of hidden interlayers are fundamental to the efficient development of vast, thick carbonate reservoirs.

[0003] Concealed interlayers exhibit diverse rock structures and complex grain compositions, including granular micritic, granular mud, mud-granular, and sparry grain structures, typically lacking the "pure muddy" or "high muddy" characteristics of conventional interlayers. The grain composition consists of bioclast debris, including planktonic foraminifera, benthic foraminifera, thick-shelled clams, echinoderms, bivalves, ostracods, and sponges. The bioclastic grain size varies considerably, ranging from silt to giant clasts, with sizes ranging from less than 10 μm to 1000 μm. The "concealed" lithology of interlayers makes it difficult to effectively identify them based solely on grain size and muddy content.

[0004] Concealed interlayers exhibit weak facies control, making prediction based on sedimentary environment difficult. In low-energy environments, rocks have high micritic content, are predominantly microporous with small throat radii, and have low permeability, typically developing lithological interlayers. Quasi-syngenetic dissolution can effectively enhance the physical properties of low-energy sediments, leading to the development of large-scale reservoirs with enormous reserves even in low-energy environments. High-energy environments are a basic condition for the development of favorable reservoirs, with rocks exhibiting a predominantly grain-supported structure, good pore connectivity, and high initial permeability. However, strong cementation during the quasi-syngenetic period leads to rock compaction, forming physical property interlayers. The relationship between sedimentary environment and reservoirs and interlayers is nonlinear; even poor reservoirs possess barrier capabilities during development, and conventional methods based on water energy intensity are insufficient to effectively identify concealed interlayers.

[0005] Bioclastic limestone exhibits a high proportion of micropores, with low porosity-permeability correlation in interlayers. Although interlayers have low permeability, their porosity varies widely, ranging from low to medium-high porosity. Core samples show good oil content, and thin sections have a low porosity. Therefore, porosity cannot be used as an evaluation parameter for concealed interlayers. Throats in interlayers are typically less than 1 μm, dominated by micropores with a small number of medium throats. The pore-throat distribution curves exhibit a single-mode pattern with good overall sorting. The main peak range is between 0.01 and 0.1 μm, and the concentration of throat distribution curves varies considerably. The displacement pressure of interlayers is typically greater than 200 Psi, reaching a maximum of 6000 Psi, and the morphology of mercury injection curves varies considerably.

[0006] The thickness of the concealed interlayers varies greatly, with a minimum thickness of only 10 cm. Their distribution is limited, but multiple stacked layers can accumulate to a total thickness of up to 30 m, and their lateral extension is extensive. Overall, the distribution of the concealed interlayers is complex and diverse, significantly different from the conventional "interbedded sand and mud" distribution pattern in clastic rocks.

[0007] Conventional interlayers typically exhibit characteristics of "high gamma, low resistivity, and high density." Carbonate rocks have low terrigenous mud content, resulting in low permeability but good reservoir properties and high oil content. Therefore, the logging response characteristics of interlayers are similar to those of reservoirs, also exhibiting "low gamma, high resistivity, and low density." The logging characteristics are not significantly different from those of the surrounding rock reservoir. The weak logging response limits the effective interpretation of interlayers in non-cored wells, leading to "false positives" and "false negatives" in the identification of interlayers in non-cored wells.

[0008] Among the published articles, there are numerous reports on interlayers in clastic reservoirs, but fewer on carbonate reservoirs, and those that exist mainly focus on the types, characteristics, and genesis (controlling factors) of carbonate interlayers. Early studies did not explain how to determine the identification criteria for interlayers, how to effectively identify them, or whether the identified interlayers truly possess barrier capabilities during development. In other words, previous studies presupposed the identification of interlayers, and then analyzed their characteristics, types, and genesis based on this, but the specific methods used to identify the interlayers are not reported.

[0009] Furthermore, existing research indicates that previous methods for identifying interlayers primarily relied on core samples, thin sections, and physical properties. This subjective approach, within a specific research scope, characterized the identification of relatively dense or poorly structured lithologies as interlayers. This method introduces significant uncertainty. Interlayers identified geologically can still experience seepage during development, offering poor containment of injected water, while poorly structured reservoirs may function as interlayers during development, effectively blocking vertical flow. Therefore, early methods for identifying interlayers are not applicable to bioclastic limestone reservoirs. The key challenge lies in identifying interlayers with sealing capabilities and analyzing their interlayer sealing capacity. Currently, research on existing technologies related to these topics is limited, particularly regarding methods for identifying concealed interlayers in bioclastic limestone reservoirs. Summary of the Invention

[0010] The purpose of this invention is to provide a method for determining hidden interlayers and their sealing properties based on a combination of dynamic and static data. This method can overcome the shortcomings of strong concealment of interlayers in thick bioclastic limestone reservoirs, "misjudgment" and "missed judgment" by non-coring wells, which leads to discrepancies between the sealing properties of the interlayers and geological predictions during development. This method can significantly improve the accuracy of characterizing thick carbonate reservoirs.

[0011] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0012] A method for determining a concealed interlayer, the method comprising:

[0013] Determine the permeability limit of the non-productive layer in the perforated section;

[0014] Determine the permeability limits of the non-permeable layer;

[0015] Based on the permeability limit of the non-producing layer and in combination with the permeability limit of the non-flowing layer, the thickness-weighted permeability of the layer segment with abnormal formation pressure gradient caused by interlayer is determined.

[0016] Based on the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by the interlayer, the identification criteria for the interlayer are determined, and the interlayer in non-coring wells is identified.

[0017] As a further improvement of the present invention, the method further includes:

[0018] Based on the development and thickness of the identified interlayers, a single-well sealing performance analysis was conducted, and the reservoir connectivity of a single well was classified into three categories: vertical connectivity, vertical sealing, and uncertainty.

[0019] Based on the single-well sealing performance analysis results, the sealing performance between the layers is divided into sealing zones, risk zones, and connectivity zones, thereby determining the sealing performance of the interlayer.

[0020] As a further improvement of the present invention, the determination of the permeability limit of the non-productive layer in the perforation section includes:

[0021] Based on production logging test data, non-producing layers that meet the conditions are selected, the permeability of producing and non-producing layers in the perforated section is statistically analyzed, and the permeability limit of non-producing layers is determined.

[0022] The following principles are followed when selecting non-productive layers that meet the criteria:

[0023] The producing and non-producing layers must share the same perforation, and both the upper and lower layers of the non-producing layer must contribute to production.

[0024] The test results from production logging data from different periods are consistent;

[0025] A producing or non-producing layer not located within a perforated section cannot be used as a statistical point.

[0026] The distinction between producing and non-producing layers follows geological laws.

[0027] As a further improvement of the present invention, determining the permeability limit of the non-permeable layer includes:

[0028] Based on pore throat data and permeability data, the contribution of throat content with different radii to permeability is statistically analyzed, the throat types that dominate the seepage properties of rocks are determined, the types of throats with sealing properties are statistically analyzed, and the permeability limit of non-seepage layers is determined.

[0029] As a further improvement of the present invention, the throats of different radii include:

[0030] Giant throats >10μm; large throats 2.5–10μm; medium throats 0.5–2.5μm; micro throats 0.075–0.5μm; and nano throats <0.075μm.

[0031] As a further improvement of the present invention, the step of determining the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by interlayers based on the permeability limit of the non-producing layer and in combination with the permeability limit of the non-flowing layer includes:

[0032] Based on formation pressure test data, the formation pressure gradient anomaly segment was selected with the permeability limit of the non-producing layer as a constraint.

[0033] Based on the permeability limit of the non-permeable layer, the influence of the permeable layer in the selected formation pressure gradient anomaly segment is eliminated, and the formation pressure gradient anomaly segment caused by interlayer is determined.

[0034] The permeability and thickness of the formation pressure gradient anomaly segment caused by the interlayer are statistically analyzed, and the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by the interlayer is determined by thickness-weighted averaging.

[0035] As a further improvement of the present invention, the step of determining the identification criteria for interlayers based on the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by the interlayer, and identifying interlayers in non-cored wells, includes:

[0036] The thickness-weighted permeability of the abnormal formation pressure gradient segment caused by the interlayer is plotted in the thickness-permeability chart to determine the permeability and thickness limits of the interlayer.

[0037] The interlayer is identified based on the standard that its permeability is less than the permeability limit and its thickness is greater than the thickness limit.

[0038] The present invention also provides a device for determining concealed partitions, the device comprising:

[0039] The first determining unit is used to determine the permeability limit of the non-productive layer in the perforated section;

[0040] The second determining unit is used to determine the permeability limit of the non-permeable layer;

[0041] The third determining unit is used to determine the thickness-weighted permeability of the formation pressure gradient abnormality segment caused by the interlayer based on the permeability limit of the non-producing layer and in combination with the permeability limit of the non-permeable layer.

[0042] The identification unit is used to determine the identification criteria of the interlayer based on the thickness-weighted permeability of the formation pressure gradient abnormality segment caused by the interlayer, and to identify the interlayer in the non-coring well.

[0043] As a further improvement of the present invention, the device further includes:

[0044] The analysis unit is used to perform single-well sealing analysis based on whether the interlayers are developed and their thickness as identified by the identification unit, and to classify the reservoir connectivity of a single well into three categories: vertical connectivity, vertical sealing, and uncertainty.

[0045] The sealing performance determination unit is used to divide the sealing performance between the layers into sealing zones, risk zones, and connecting zones based on the sealing performance analysis results of the single well, thereby determining the sealing performance of the interlayer.

[0046] As a further improvement of the present invention, the third determining unit includes:

[0047] The selection module is used to select the formation pressure gradient anomaly segment based on formation pressure test data and with the permeability limit of the non-producing layer as a constraint.

[0048] The first determining module is used to eliminate the influence of the permeable layer in the selected formation pressure gradient anomaly segment based on the permeability limit of the non-permeable layer, and to determine the formation pressure gradient anomaly segment caused by the interlayer.

[0049] The second determining module is used to statistically analyze the permeability and thickness of the formation pressure gradient anomaly segment caused by the interlayer, and to determine the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by the interlayer by using a thickness-weighted average.

[0050] The identification unit includes:

[0051] The third determining module is used to input the thickness-weighted permeability of the abnormal formation pressure gradient segment caused by the interlayer into the thickness-permeability chart to determine the permeability limit and thickness limit of the interlayer.

[0052] The identification module is used to identify the interlayer based on the standard that the permeability is less than the permeability limit and the thickness is greater than the thickness limit.

[0053] The beneficial effects of this invention are:

[0054] The method for identifying hidden interlayers provided by this invention involves determining the permeability limit of the non-productive layer in the perforated section; determining the permeability limit of the non-permeable layer; determining the thickness-weighted permeability of the formation pressure gradient abnormality segment caused by the interlayer based on the permeability limit of the non-productive layer and the permeability limit of the non-permeable layer; and finally determining the identification criteria of the interlayer based on the thickness-weighted permeability, thereby identifying the interlayer in the non-coring well. Through the above methods, this invention creatively proposes permeability as the main parameter for identifying hidden interlayers, and originally establishes a method for identifying interlayers using "dynamic and static mathematical statistics - determination of permeability threshold value (determination of interlayer identification standard value) - threshold value truncation (using permeability standard value as the evaluation basis)". Compared with the conventional research approach of "coring well identification - logging calibration - non-coring well interpretation", the new research approach avoids the problem of weak logging response of interlayers. By setting a threshold value truncation for the permeability of logging interpretation (i.e., setting an interlayer identification standard based on permeability), accurate identification of interlayers in non-coring wells can be achieved.

[0055] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0056] Figure 1 This is a flowchart of the method for determining the hidden interlayer of the present invention;

[0057] Figure 2 This is a schematic diagram illustrating the selection of perforation intervals that meet statistical conditions when determining non-producing layers based on production logging test (PLT) data in an embodiment of the present invention.

[0058] Figure 3 This is a graph showing the relationship between different pore throats and permeability in an embodiment of the present invention;

[0059] Figure 4a This is a thickness-weighted permeability map of interlayers in the pressure anomaly segment determined by the formation pressure gradient anomaly method in this embodiment of the invention.

[0060] Figure 4b This is a thickness-weighted permeability-thickness intersection chart in an embodiment of the present invention;

[0061] Figure 5 This is a schematic diagram of the single-well sealing performance analysis results in an embodiment of the present invention;

[0062] Figure 6 This is a schematic diagram of the interlayer sealing performance evaluation results in an embodiment of the present invention. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] To address the problems of existing technologies, this invention provides a method for accurately identifying concealed interlayers and determining their sealing capabilities by combining dynamic and static data. The principle behind this method is that interlayers in bioclastic limestone reservoirs are highly concealed, and even poor reservoirs may possess sealing capabilities. The accuracy of interlayer identification based solely on static geological data is low, and the sealing capabilities of interlayers during development do not match geological predictions. This invention fully utilizes dynamic development data and combines it with static geological data, taking into full account the sealing capabilities of interlayers, using permeability as the primary parameter for interlayer identification. Anomalies in formation pressure gradients indicate the presence of interlayers with good sealing capabilities. By statistically analyzing the permeability of the anomaly zone in the formation pressure gradient, a permeability threshold value for interlayers with sealing capabilities is determined. Based on this threshold value, interlayers in non-cored wells can be identified. Furthermore, pressure anomalies caused by produced fluids are excluded using a production layer statistical method, and the influence of permeable layers on the statistical results is excluded using a microstructure method. This invention enables the effective identification of concealed interlayers in thick bioclastic limestone, and the sealing performance during development is consistent with geological predictions, which can meet the water injection development needs of oilfield strata.

[0065] The technical solution adopted in this invention is described in detail below. Please refer to [link / reference]. Figure 1 As shown:

[0066] S1. Based on production logging test (PLT) data, select non-producing layers that meet the conditions, and statistically analyze the permeability of producing and non-producing layers in the perforated section to determine the permeability limit of non-producing layers. This limit value is used to define non-producing layers, not true interlayers. Its purpose is to constrain the selection of formation pressure gradient anomaly sections and exclude local pressure anomalies caused by development and production.

[0067] S2. Based on pore throat data and permeability data, the contribution of throat content of different radii in rock samples to permeability is statistically analyzed to determine the throat type that dominates the seepage properties of the rock, the throat type with sealing properties is statistically analyzed, and the permeability limit of the non-seepage layer is determined. This limit value is used to constrain the statistical analysis of physical properties of pressure anomaly sections and to exclude the influence of seepage layers on the calculation of interlayer permeability.

[0068] S3. Based on formation pressure test data, select pressure gradient anomaly sections under the constraint of non-producing layers, and eliminate the influence of seepage layers according to the permeability limit of non-seepage layers. Statistically calculate the permeability and thickness of pressure anomaly sections caused by interlayers. Determine the thickness-weighted permeability value of pressure anomaly sections caused by interlayers through thickness-weighted averaging. Define the interlayer identification criteria based on all sample point values.

[0069] S4. Input the thickness-weighted permeability of the formation pressure gradient abnormality segment caused by the interlayer into the thickness-permeability chart to determine the permeability limit and thickness limit of the interlayer; using the standard that the permeability is less than the permeability limit and the thickness is greater than the thickness limit, the interlayer in non-cored wells is identified by truncation through the permeability threshold value.

[0070] The present invention further achieves accurate prediction of the sealing performance of the aforementioned identified concealed interlayers through the following method:

[0071] S5. Based on the development and thickness of interlayers, conduct a single-well sealing performance analysis. The reservoir connectivity in a single well is categorized into three types: vertical connectivity, vertical isolation, and uncertainty. Vertical connectivity refers to the superposition of high-quality reservoirs in different layers without interlayers, and perforations are deployed in both the upper and lower high-quality reservoirs of the layer, or perforations are deployed in a large layer. During reservoir development, fluids will migrate vertically, and water channeling is likely to occur during water injection development. Vertical isolation refers to the development of stable-thickness interlayers between layers. Even if high-quality reservoirs are developed in both upper and lower layers and perforations are deployed, vertical seepage will not occur due to the good sealing performance of the interlayers, and water channeling will not occur during water injection development. Uncertainty refers to the development of thin interlayers between layers, with perforations deployed in both upper and lower high-quality reservoirs. Due to the thinness of the interlayers, it is uncertain whether they can effectively block fluids vertically.

[0072] S6. Based on the aforementioned single-well sealing performance analysis, spatial interpolation and other methods can be used to characterize the sealing performance between strata, dividing the plane into sealing zones, risk zones, and interconnected zones. In the sealing zone, all wells have stable interlayers, and water channeling does not occur between strata during water injection development. In the risk zone, all wells have thin interlayers, and water channeling risk exists between strata during water injection development. In the interconnected zone, all wells do not have interlayers, and reservoirs of different strata are interconnected.

[0073] By implementing the above technical means, the present invention has at least the following advantages:

[0074] One of the beneficial effects of this invention is that it creatively proposes permeability as the main parameter for identifying hidden interlayers, and originally establishes a method for identifying interlayers using "dynamic and static mathematical statistics - permeability threshold determination - threshold truncation". Compared with the conventional research approach of "coring well identification - logging calibration - non-coring well interpretation", the new research approach avoids the problem of weak logging response of interlayers. By setting a threshold truncation for the permeability of logging interpretation (i.e., setting an interlayer identification standard based on permeability), the identification of interlayers in non-coring wells can be achieved.

[0075] The second beneficial effect of this invention is that, with the aim of identifying sealing interlayers, a method is creatively proposed to determine the identification criteria for interlayers based on the organic coupling of production data (PLT), microstructure data, and formation pressure data, thereby identifying interlayers. The boundaries of interlayers are determined by statistically analyzing the formation permeability that causes anomalies in formation pressure gradients, and the sealing performance of interlayers during development is consistent with geological predictions.

[0076] The third beneficial effect of this invention is that it creatively establishes a criterion for identifying concealed interlayers, and interprets interlayers in all wells by using a threshold value cutoff. Taking into account both the development and thickness of interlayers, the sealing performance of individual wells is analyzed. From a point-to-surface perspective, based on individual wells, the sealing performance between layers is further analyzed, demonstrating the rationality of the layer division for water injection development in thick carbonate reservoirs.

[0077] Furthermore, the present invention provides a method for evaluating hidden interlayers and their sealing properties by combining dynamic and static data. The sealing properties of the interlayers have been confirmed by pilot tests, which can lay a solid geological foundation for the water injection development of thick carbonate reservoirs.

[0078] The method for determining hidden interlayers provided by the present invention will be described in detail below with reference to specific embodiments.

[0079] This embodiment takes the effective identification process of hidden interlayers in Cretaceous bioclastic limestone in the Middle East as an example to introduce the method of determining hidden interlayers by combining dynamic and static data in this application.

[0080] S1. Determine the permeability limit value of the non-productive layer in the perforation section based on the production layer statistical method.

[0081] The following principles should be followed when selecting qualified non-producing layers: a) The producing and non-producing layers must be in the same perforation zone, and both the upper and lower parts of the non-producing layer must contribute to production; b) Production logging test data from different periods should have consistent development characteristics; c) The producing or non-producing layer cannot be used as a statistical point if it is not within the perforated interval; d) The distinction between non-producing and producing layers should follow geological understanding principles. Based on production logging test (PLT) statistics, such as... Figure 2 As shown, the permeability of reservoirs currently contributing to reservoir productivity is greater than 10 mD, and the permeability limit for non-producing layers is 10 mD. This result can serve as a constraint for selecting formation pressure gradient anomaly segments. It is important to note that non-producing layers are not interlayers; their oil and gas production is influenced by the surrounding rock. Within the same perforated layer, if adjacent reservoirs have high permeability, a significant permeability difference exists between them. Even if the non-producing layer has seepage capacity, it will not produce any oil or gas during development. When the permeability difference between adjacent formations is greater than 10 mD, the formation with relatively lower permeability will be considered a non-producing layer.

[0082] S2. Determine the permeability limit of the non-permeable layer based on the microstructure method.

[0083] Specifically, throats can be classified into giant throats (>10 μm), large throats (2.5–10 μm), medium throats (0.5–2.5 μm), micro throats (0.075–0.5 μm), and nano throats (<0.075 μm). The type of the largest throat in each rock sample was determined, and the cumulative percentage content of the largest throat was calculated. All sample points were plotted on a cumulative throat percentage–permeability chart. The results show (see...) Figure 3 The content of giant throats (>10 μm), large throats (2.5–10 μm), and medium throats (0.5–2.5 μm) is correlated with permeability; the higher the percentage content, the higher the permeability, indicating that these types of throats contribute to permeability. When the rock only has micro-throats (0.075–0.5 μm) and nano-throats (<0.075 μm), the percentage content of micro-throats is not correlated with permeability; the increase in micro-throat content does not lead to an increase in permeability, indicating that micro-throats contribute almost nothing to permeability. Statistical analysis shows that rocks dominated by micro-throats or nano-throats usually have permeability less than 1 mD. Rocks with permeability greater than 1 mD usually have medium, large, and giant throats, and there is still a risk of seepage. Therefore, the sealing interlayers should be less than 1 mD.

[0084] S3. Determine the thickness-weighted permeability value of the formation pressure gradient anomaly segment caused by interlayers by combining the formation pressure gradient anomaly method.

[0085] Based on the aforementioned statistical results of non-producing layer permeability limits, the permeability of formation pressure gradient anomaly segments should be less than 10 mD. Formation segments meeting this condition are selected. Permeability data from the pressure gradient anomaly segments are sampled into the model grid. At grid precision, the thickness and permeability values ​​of each layer are statistically analyzed. Based on the results obtained from the microstructure method, samples greater than 1 mD are removed. The thickness-weighted permeability value of the anomaly segment is determined through a thickness-weighted average. Figure 4a ).

[0086] S4. Determine the identification criteria for interlayers and identify interlayers in non-coring wells.

[0087] All samples were plotted on a thickness-permeability chart to determine the permeability and thickness limits of the interlayer. Figure 4b The criteria for identifying interlayers were ultimately determined as follows: interlayer permeability less than 0.5 mD and thickness greater than 2.5 m; interlayer permeability less than 0.65 mD and thickness greater than 1 m. These criteria were then used to identify interlayers in non-cored wells.

[0088] S5. Based on the development and thickness of interlayers, the reservoir connectivity in a single well is classified into three categories: vertical connectivity, vertical isolation, and uncertain connectivity (see [reference]). Figure 5 Vertical connectivity refers to the superposition of high-quality reservoirs in different layers, without interlayers, and with perforations deployed in both the upper and lower high-quality reservoirs of the layer, or perforations deployed in a large layer. During reservoir development, fluids will migrate vertically, making water channeling likely during water injection development. Vertical isolation refers to the development of stable-thickness interlayers between layers. Even if high-quality reservoirs are developed in both upper and lower layers and perforations are deployed, vertical seepage will not occur due to the good sealing properties of the interlayers, and water channeling will not occur during water injection development. Uncertainty refers to the development of thin interlayers between layers. While perforations are deployed in both upper and lower high-quality reservoirs, the thinness of the interlayers raises uncertainty regarding their ability to vertically isolate fluids.

[0089] S6. Based on the aforementioned single-well sealing performance analysis results, the inter-stratum sealing performance is characterized, and the planar region is divided into a sealing zone, a risk zone, and a connecting zone (see...). Figure 6 In the isolated zone, all wells have stable interlayers, i.e., permeability <0.5mD and thickness >2.5m, which are vertically isolated and prevent water channeling between layers during water injection development. In the risk zone, all wells have thin interlayers, i.e., permeability <0.65m and thickness <2.5m, which pose a risk of water channeling between layers during water injection development. In the connected zone, all wells do not have interlayers, are vertically connected, and reservoirs of different layers are interconnected.

[0090] In summary, the method and apparatus for determining the sealing capacity of concealed interlayers by combining dynamic and static data provided in this invention creatively proposes a method of "dynamic and static mathematical statistics - permeability threshold determination - threshold truncation" to identify interlayers. Compared with the conventional research approach of "coring well identification - logging calibration - non-coring well interpretation," this new research approach avoids the problem of weak logging response in interlayers. By setting a threshold value to truncate the permeability of the logging interpretation, interlayer identification in non-coring wells can be achieved. Moreover, this invention creatively uses permeability as the main parameter for identifying concealed interlayers, aiming to identify interlayers with sealing capabilities. It combines dynamic and static data, and determines the interlayer identification criteria based on the organic coupling of production data (PLT), microstructure data, and formation pressure data. Furthermore, based on the innovative establishment of concealed interlayer identification criteria, this invention further analyzes the sealing capacity between layers, demonstrating the rationality of the layer division of thick carbonate reservoirs.

[0091] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining concealed interlayers, characterized in that, The method includes: Determine the permeability limit of the non-productive layer in the perforated section; Determine the permeability limits of the non-permeable layer; Based on the permeability limit of the non-producing layer and in combination with the permeability limit of the non-flowing layer, the thickness-weighted permeability of the layer segment with abnormal formation pressure gradient caused by interlayer is determined. Based on the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by the interlayer, the identification criteria for the interlayer are determined, and the interlayer in non-coring wells is identified. The determination of the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by interlayers, based on the permeability limit of the non-producing layer and in conjunction with the permeability limit of the non-flowing layer, includes: Based on formation pressure test data, the formation pressure gradient anomaly segment was selected with the permeability limit of the non-producing layer as a constraint. Based on the permeability limit of the non-permeable layer, the influence of the permeable layer in the selected formation pressure gradient anomaly segment is eliminated, and the formation pressure gradient anomaly segment caused by interlayer is determined. The permeability and thickness of the formation pressure gradient anomaly segment caused by the interlayer are statistically analyzed, and the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by the interlayer is determined by thickness-weighted averaging. The determination of the identification criteria for interlayers based on the thickness-weighted permeability of the formation pressure gradient anomaly interval caused by the interlayers, and the identification of interlayers in non-cored wells, includes: The thickness-weighted permeability of the abnormal formation pressure gradient segment caused by the interlayer is plotted in the thickness-permeability chart to determine the permeability and thickness limits of the interlayer. The interlayer is identified based on the standard that its permeability is less than the permeability limit and its thickness is greater than the thickness limit.

2. The method for determining concealed interlayers according to claim 1, characterized in that, The method further includes: Based on the development and thickness of the identified interlayers, a single-well sealing performance analysis was conducted, and the reservoir connectivity of a single well was classified into three categories: vertical connectivity, vertical sealing, and uncertainty. Based on the results of the single-well sealing performance analysis, the sealing performance between the layers is divided into sealing zones, risk zones, and connectivity zones, thereby determining the sealing performance of the interlayer.

3. The method for determining concealed interlayers according to claim 1 or 2, characterized in that, The permeability limit for determining the non-productive layer in the perforated section includes: Based on production logging test data, non-producing layers that meet the conditions are selected, the permeability of producing and non-producing layers in the perforated section is statistically analyzed, and the permeability limit of non-producing layers is determined. The following principles are followed when selecting non-productive layers that meet the criteria: The producing and non-producing layers must share the same perforation, and both the upper and lower layers of the non-producing layer must contribute to production. The test results from production logging data from different periods are consistent; A producing or non-producing layer not located within a perforated section cannot be used as a statistical point. The distinction between producing and non-producing layers follows geological laws.

4. The method for determining concealed interlayers according to claim 1 or 2, characterized in that, The determination of the permeability limit of the non-permeable layer includes: Based on pore throat data and permeability data, the contribution of throat content with different radii to permeability is statistically analyzed, the throat types that dominate the seepage properties of rocks are determined, the types of throats with sealing properties are statistically analyzed, and the permeability limit of non-seepage layers is determined.

5. The method for determining concealed interlayers according to claim 4, characterized in that, The throats of different radii include: Giant throats >10μm; large throats 2.5~10μm; medium throats 0.5~2.5μm; micro throats 0.075~0.5μm; and nano throats <0.075μm.

6. A device for determining concealed interlayers, characterized in that, The device includes: The first determining unit is used to determine the permeability limit of the non-productive layer in the perforated section; The second determining unit is used to determine the permeability limit of the non-permeable layer; The third determining unit is used to determine the thickness-weighted permeability of the formation pressure gradient abnormality segment caused by the interlayer based on the permeability limit of the non-producing layer and in combination with the permeability limit of the non-permeable layer. The identification unit is used to determine the identification criteria of the interlayer based on the thickness-weighted permeability of the formation pressure gradient abnormality segment caused by the interlayer, and to identify the interlayer in the non-coring well. The third determining unit includes: The selection module is used to select the formation pressure gradient anomaly segment based on formation pressure test data and with the permeability limit of the non-producing layer as a constraint. The first determining module is used to eliminate the influence of the permeable layer in the selected formation pressure gradient anomaly segment based on the permeability limit of the non-permeable layer, and to determine the formation pressure gradient anomaly segment caused by the interlayer. The second determining module is used to statistically analyze the permeability and thickness of the formation pressure gradient anomaly segment caused by the interlayer, and to determine the thickness-weighted permeability of the formation pressure gradient anomaly segment caused by the interlayer by using a thickness-weighted average. The identification unit includes: The third determining module is used to input the thickness-weighted permeability of the abnormal formation pressure gradient segment caused by the interlayer into the thickness-permeability chart to determine the permeability limit and thickness limit of the interlayer. The identification module is used to identify the interlayer based on the standard that the permeability is less than the permeability limit and the thickness is greater than the thickness limit.

7. The device for determining concealed interlayers according to claim 6, characterized in that, The device further includes: The analysis unit is used to perform single-well sealing analysis based on whether the interlayers are developed and their thickness as identified by the identification unit, and to classify the reservoir connectivity of a single well into three categories: vertical connectivity, vertical sealing, and uncertainty. The sealing performance determination unit is used to divide the sealing performance between the layers into sealing zones, risk zones, and connecting zones based on the results of the single-well sealing performance analysis, thereby determining the sealing performance of the interlayer.

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