Connectivity description method of conglomerate reservoir based on mudstone division

Abstract

The present invention provides a method for describing the connectivity of a conglomerate reservoir based on mudstone division, and the method comprises: step 1, observing the logging curve to determine the formation encountered by a single well; step 2, comparing multiple wells and combining stable mudstone layers; step 3, comprehensively considering the sedimentary pattern and describing the distribution of the mudstone layer by combining well and seismic data; step 4, dividing the conglomerate body into stages by taking stable mudstone as the interlayer interruption; and step 5, verifying the description result of the reservoir connectivity by means of dynamic development and monitoring. The method for describing the connectivity of a conglomerate reservoir based on mudstone division has clear ideas, is relatively simple to operate, and has low multi-solution results, and provides a practical method for accurately describing the connectivity of conglomerate reservoirs, and provides geological support for water injection development of conglomerate oil reservoirs.

Description

Technical Field

[0001] The invention relates to the field of sandy conglomerate oil reservoir identification, and in particular to a sandy conglomerate reservoir connectivity description method based on mudstone division. Background Art

[0002] Gravel fans generally refer to individual fans or fan groups of different sedimentary types such as alluvial fans, turbidite fans, fan deltas, and nearshore underwater fans formed by rapid accumulation above or below water in the steep slope of a fault basin. They are mainly block-like geological rock bodies composed of sandstone and conglomerate. Gravel oil reservoirs formed by such gravel fans have the characteristics of complex geological structure, large reservoir thickness, rapid changes in lithology and lithofacies, and strong heterogeneity. They are a type of oil reservoir that is difficult to develop. Such oil reservoirs have been discovered both at home and abroad. In recent years, the proportion of gravel oil reservoirs in newly discovered and newly developed oil reservoirs in China has been increasing. Therefore, it is of great significance to achieve efficient development of gravel oil reservoirs.

[0003] Unlike conventional sandstone, conglomerate reservoirs are formed in event-accumulated and rapid gravity flow deposition. They have poor reservoir stratification, complex connectivity, poor conventional logging curve cyclicity, no obvious features, difficult to determine marker layers, difficult to divide single wells, difficult to compare inter-well strata, and difficult to predict reservoir connectivity. Based on the above characteristics, the accuracy of phase division and internal research of conglomerate reservoirs is low, which is difficult to meet the needs of daily water injection development work, resulting in the lack of obvious injection and production effects in the development process of such reservoirs, and the overall elastic development trend with rapid decline. Therefore, accurately describing the connectivity of conglomerate reservoirs has become a prerequisite for the efficient development of conglomerate reservoirs and a geological basis for improving recovery.

[0004] The existing reservoir connectivity description methods for conglomerate reservoirs start from the perspective of reservoir identification, establish a relatively accurate sedimentation model, determine the reservoir boundary through seismic data, and further subdivide the reservoir using core data, etc. However, when the above methods are applied to conglomerate reservoirs with complex lithology, the reservoir identification accuracy is reduced, and the connected body description results cannot be effectively verified during the development process.

[0005] In the Chinese patent application with application number: CN201910950292.8, a reservoir connectivity analysis method is involved, which includes the following steps: S1. Establishing a reservoir physical property parameter knowledge base; S2. Establishing a reservoir physical property prototype model; S3. Performing model quality inspection on all physical property prototype models and selecting the final prototype model; S4. Coarsening the selected prototype model and applying the coarsened model to numerical simulation technology, optimizing the combination of model parameters after numerical simulation; S5. Analyzing the numerical simulation results and determining the reservoir connectivity.

[0006] In the Chinese patent application with application number: CN201910276171.X, a seismic identification method and device for the connectivity of fault-karst reservoirs are involved. The method includes: constructing a seismic maximum likelihood body based on a three-dimensional seismic data body; spatially carving the seismic maximum likelihood body using a threshold value of an attribute of the seismic maximum likelihood body to obtain a spatial contour of the fault-karst body; selecting a first point and a second point at the same altitude in the space of the fault-karst body to obtain the formation pressure at the first point and the formation pressure at the second point; comparing the formation pressure at the first point and the formation pressure at the second point, and judging whether the reservoir between the first point and the second point is connected based on the comparison result.

[0007] In the Chinese patent application with application number: CN202010189180.8, a method for automatic identification of reservoir configuration interface in an oil reservoir geological model is involved, and the method for automatic identification of reservoir configuration interface in an oil reservoir geological model includes: step 1, initializing basic parameters; step 2, traversing the grid according to IJK; step 3, traversing the grid of the configuration geometry constructed in step 2; step 4, traversing the configuration geometry grid set generated in step 3, and generating a configuration geometry boundary grid set; step 5, adding the generated configuration geometry to the configuration body set established in step 1, and returning to step 2 to continue traversing the grid until all grids are traversed and stored.

[0008] The above existing technologies are greatly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new method for describing the connectivity of sandstone and conglomerate reservoirs based on mudstone division. Summary of the invention

[0009] The purpose of the present invention is to provide a method for describing the connectivity of conglomerate reservoirs based on mudstone division, which utilizes mudstone to divide the stages of conglomerate reservoirs, thereby describing the connectivity of reservoirs.

[0010] The object of the present invention can be achieved by the following technical measures: a method for describing the connectivity of a sandy conglomerate reservoir based on mudstone division, the method for describing the connectivity of a sandy conglomerate reservoir based on mudstone division comprising:

[0011] Step 1, observe the well logging curve to determine the formation encountered by the single well;

[0012] Step 2, multi-well comparison, combined stable mudstone layer;

[0013] Step 3: Comprehensively consider the sedimentation mode and describe the distribution of mudstone layers by combining well and seismic data;

[0014] Step 4, using stable mudstone as the interlayer divider, dividing the sandstone and conglomerate body into stages;

[0015] Step 5: Verify the description results of reservoir connectivity through dynamic development and monitoring.

[0016] The purpose of the present invention can also be achieved by the following technical measures:

[0017] In step 1, the effective logging curves such as acoustic time difference, neutron, density porosity, natural potential, and microelectrode are used to judge the formation encountered by a single well and identify the reservoir and mudstone layer.

[0018] In step 1, the drilled section where the natural potential curve shows a negative anomaly is a sand body, and the high overlap of the three porosity curves reflects that the physical properties of this section are good; conversely, the section where the natural potential curve is straight and the three porosity curves are scattered is a mudstone formation.

[0019] In step 2, according to the characteristic that mudstone gradually develops and thickens from the core to the fan end, well points in different sedimentary areas are selected as standard wells. By comparing the curves of multiple wells, the characteristics of formation changes are intuitively reflected, and relatively stable mudstones are identified as comparison marks and combined.

[0020] In step 3, the sedimentary pattern of the conglomerate fan is comprehensively considered, and the mudstone layer distribution is described by combining well and seismic data in the phase control mode. Under the constraint of seismic data, the unification and closure of the mudstone layer in the whole area are completed.

[0021] In step 3, the reservoir shows high resistivity in the logging response, and the three porosity curves of acoustic time difference, neutron and density basically coincide with each other; the seismic profile shows wide and messy weak reflections without obvious reflection axes.

[0022] In step 3, the resistivity of mudstone in the logging response is low, and the three porosity curves of acoustic time difference, neutron, and density are scattered; the seismic profile shows that the seismic axis reflection is clear and has good continuity.

[0023] In step 3, the mudstones encountered in the standard wells are identified and numbered according to the different characteristics of the mudstones and reservoirs in the logging response and seismic phases, and the mudstones are tracked by number. Combined with the sedimentary characteristics of the sandstone fan, the vertical and horizontal distribution patterns of the mudstones are established, the mudstone layers are closed in the entire area, the strata are divided, and the stratigraphic framework is established.

[0024] In step 4, connected secondary fan stages are developed inside the stable mudstone, and the fractures in the same stage are transformed during the formation fracturing process, and the connectivity is improved. On this basis, the reservoir connectivity is described to improve accuracy.

[0025] In step 5, referring to the description results of reservoir connectivity, in accordance with the principle of phase correspondence and advanced water injection, wells with more production sections and fewer mudstone interlayers are selected for injection transfer within the same phase to achieve a higher injection-production correspondence rate; after making injection-production adjustments to the well group, pay close attention to the production situation, use monitoring methods in a timely manner, and further complete the verification of reservoir connectivity through development effectiveness characteristics.

[0026] The method for describing the connectivity of conglomerate reservoirs based on mudstone division in the present invention, on the basis of identifying conglomerate reservoirs using conventional seismic phase data, screens and combines the mudstone inside the conglomerate reservoir, selects relatively stable mudstone for stratification, and divides the stratigraphic stages. Based on the mudstone comparison model and combined with development data verification, the reservoir connectivity description is completed. This method for describing the connectivity of conglomerate reservoirs can be applied to the reservoir transformation and water injection development of conglomerate oil reservoirs with complex lithology. The idea of ​​the present invention is clear, the operation is relatively simple, and the result has low multi-solution. It provides a practical method for achieving accurate description of the connectivity of conglomerate reservoirs and provides geological support for water injection development of conglomerate oil reservoirs. The method has been applied in the Yan 22 block of the Yanjia Oilfield of the Dongxin Oil Production Plant of Shengli Oilfield, and the injection and production adjustment of the development well group has been completed. The conversion of water injection wells to corresponding oil wells has initially shown results. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of a specific embodiment of the method for describing the connectivity of a sandstone reservoir based on mudstone division of the present invention;

[0028] Figure 2 It is a schematic diagram of single well formation drilling in a specific embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the development mode of the curtain mudstone in the sandstone fan in a specific embodiment of the present invention;

[0030] Figure 4 A schematic diagram of multi-well comparison in a specific embodiment of the present invention;

[0031] Figure 5 It is a schematic diagram of mudstone distribution determined by combining well-seismic analysis in a specific embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of the sedimentation mode of a sandstone fan in a specific embodiment of the present invention;

[0033] Figure 7 A schematic diagram of connectivity analysis and development verification principles in a specific embodiment of the present invention;

[0034] Figure 8 It is a schematic diagram of the internal connection of the mudstone reservoir of the Yan 22-Slant 47 well group and the disconnection of the external reservoir in a specific embodiment of the present invention;

[0035] Fig. 9 It is a schematic diagram of advanced water injection into the connected and unconnected reservoirs in the mudstone reservoir of the Salt 22-23 well group in a specific embodiment of the present invention;

[0036] Fig.10 This is a schematic diagram of the disconnection caused by poor reservoir development judged by three porosity curves of the Yan 22-Slant 62 well group in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0039] like Figure 1 As shown, Figure 1 The flowchart of the method for describing the connectivity of sandstone reservoirs based on mudstone division of the present invention is shown in FIG.

[0040] Step 101, using the effective logging curves such as acoustic time difference, neutron, density porosity, natural potential, microelectrode, etc., to judge the formation encountered by the single well and identify the reservoir and mudstone layer;

[0041] Step 102, comparing multiple wells, summarizing the evolution law of mudstone layers, selecting stable mudstones in the interior of the sandstone conglomerate body and combining them;

[0042] Step 103, comprehensively considering the sedimentary mode of the sandstone fan, using the combination of well and seismic data in the phase control mode to describe the distribution of the mudstone layer, and completing the unification and closure of the mudstone layer in the entire area under the constraint of seismic data;

[0043] Step 104, using stable mudstone as the interval between layers, dividing the stratigraphic stages, and describing the reservoir connectivity within each stage;

[0044] Step 105, verifying the description result of the reservoir connectivity through dynamic development, monitoring and other means.

[0045] Embodiment 1:

[0046] In a specific embodiment of the present invention, the method for describing the connectivity of a sandstone reservoir based on mudstone division includes the following steps:

[0047] Step 1: Observe the logging curves to determine the formation encountered by the single well. Use the acoustic time difference, neutron, density porosity curves, as well as natural potential, microelectrode and other effective logging curves to analyze the formation encountered by the single well and identify the reservoir and mudstone layer. The drilling section with negative anomalies in the natural potential curve is a sand body, and the high overlap of the three porosity curves reflects that the physical properties of this section are good. On the contrary, the part with a straight natural potential curve and scattered three porosity curves is a mudstone formation, such as Figure 2 shown.

[0048] Step 2: Multi-well comparison and combination of stable mudstone layers. During the development process, stable mudstone will wrap sand bodies, be broken up and reorganized. Its development pattern is as follows: Figure 3 As shown in Figure 2. According to the characteristics of mudstone gradually developing and thickening from the core to the fan end, wells in different sedimentary areas are selected as standard wells. By comparing the curves of multiple wells, the characteristics of stratum changes can be intuitively reflected, and the relatively stable mudstone can be identified as a comparison mark and combined, as shown in Figure 2. Figure 4 shown.

[0049] Step 3, comprehensively consider the sedimentation pattern and describe the distribution of mudstone layers through the combination of well logging and seismic. The reservoir shows high resistivity in the logging response, and the three porosity curves of acoustic time difference, neutron, and density basically coincide; the seismic profile shows a wide range of messy weak reflections without obvious reflection axes. The resistivity of mudstone in the logging response is relatively low, and the three porosity curves of acoustic time difference, neutron, and density are scattered; the seismic profile shows that the seismic axis reflection is clear and continuous. According to the different characteristics of mudstone and reservoir in logging response and seismic phase, the mudstone encountered in the standard well is identified and numbered, and the mudstone is tracked by number, such as Figure 5 Combined with the sedimentary characteristics of the sandstone fan, the vertical and horizontal distribution patterns of mudstone were established, the mudstone layer was closed in the whole area, the system layer division was completed, and the stratigraphic framework was established, as shown in Figure 1. Figure 6 shown.

[0050] Step 4: Use stable mudstone as the interval to divide the sandstone and conglomerate into stages. By comparing the actual production situation, we believe that the stable mudstone has connected secondary fan stages, and the fractures in the same stage can be transformed during the formation fracturing process, and the connectivity is improved. Describing the reservoir connectivity on this basis can improve accuracy. Figure 7 As shown, mode 1 is stable mudstone, and the 1-3 perforation section of Well 1 is not connected with the perforation section of Well 2; mode 2 is unstable mudstone, in which the mudstone does not play a sealing role, and the 3-2 perforation section of Well 3, the 4-2 perforation section of Well 4 and the 5-2 perforation section of Well 5 are interconnected.

[0051] Step 5: Verify the description results of reservoir connectivity through dynamic development, monitoring and other means. Referring to the description results of reservoir connectivity, according to the principle of "phase correspondence, advanced water injection", wells with more production sections and fewer mudstone barriers are selected for injection in the same phase to achieve a higher injection-production correspondence rate, such as Figure 7 After making injection and production adjustments to the well group, pay close attention to production conditions, use monitoring methods in a timely manner, and further verify reservoir connectivity through development effectiveness characteristics.

[0052] Embodiment 2:

[0053] In the specific embodiment 2 of the present invention, the same comparison idea is adopted. After the sandstone and mudstone are identified by logging and the stable mudstone distribution is judged by combining well seismic, the stable mudstone No. 6 mudstone is divided. The newly put into production section of Salt 22-Slant 49 Well in 2010.02 and the water injection section of Salt 22-Slant 47 Well are in the same connected body, and the production layer of Salt 22-Slant 49 Well is flooded; in November 2012, Salt 22-Slant 49 Well returned to production in the upper reservoir of No. 6 mudstone. This layer was not water-injected, and the production characteristics were low energy and low liquid, which were consistent with the analyzed connectivity, such as Figure 8 shown.

[0054] Embodiment 3:

[0055] In the specific embodiment 3 of the present invention, the salt 22-23 well injects water into the 3370-3400 m perforation section, and the production section 3430-3532 m of the salt 22-slant 47 well is located between the No. 6 stable mudstone and the No. 7 stable mudstone. It is analyzed that the reservoirs between the No. 6 and No. 7 stable mudstones are interconnected. During the production process, the salt 22-slant 47 well has obvious effects, the liquid volume increases from 6.3 cubic meters to 7.8 cubic meters, the daily oil increases from 4.1 to 5.1 tons, and the area of ​​the indicator diagram increases significantly. At the same time, between the No. 7 stable mudstone and the No. 8 stable mudstone, the salt 22-slant 47 well has no perforation section production, and the salt 22-23 well injects water in advance to replenish energy for the later return production of the salt 22-slant 47 well, thereby improving the development effect. Fig. 9 shown.

[0056] Embodiment 4:

[0057] In the specific embodiment 4 of the present invention, the reservoir evaluation was carried out on the salt 22-slant 62 well group. The internal reservoirs of stable mudstones 8 and 9 were analyzed through step 1. The acoustic time difference, neutron, density porosity, and natural potential showed that the reservoir development of the corresponding production layer section 3334-3550 meters of the salt 22-42 well was relatively thin and had a high mud content. The analysis showed that the reservoir development of the production sections of the two wells was unstable, resulting in poor connectivity. During the production process, the salt 22-42 well did not see the effective characteristics of the salt 22-slant 62 water well injection. The dynamic verification was consistent with the analysis, such as Fig.10 shown.

[0058] The present invention provides a method for describing reservoir connectivity of a conglomerate reservoir, which solves the problems of difficulty in stratigraphic comparison and reservoir connectivity description in conglomerate reservoirs. The method uses relatively stable mudstone to divide the stratigraphic framework, and on this basis completes the description of reservoir connectivity, thereby achieving effective injection-production correspondence in the development process of conglomerate reservoirs and achieving the purpose of improving recovery.

[0059] Finally, it should be noted that the above 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 aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0060] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A method for describing the connectivity of sandstone and conglomerate reservoirs based on mudstone division, characterized in that: The sandstone reservoir connectivity description method based on mudstone division includes: Step 1, observe the well logging curve to determine the formation encountered by the single well; Step 2, multi-well comparison, combined stable mudstone layer; Step 3: Comprehensively consider the sedimentation pattern and describe the distribution of mudstone layers by combining well and seismic data; Step 4, using stable mudstone as the interlayer divider, dividing the sandstone and conglomerate body into stages; Step 5, verify the description results of reservoir connectivity through dynamic development and monitoring methods; In step 1, the formation encountered by a single well is judged by using the three porosities of acoustic time difference, neutron and density, as well as the natural potential and microelectrode effective logging curves, to identify the reservoir and mudstone layer; In step 2, according to the characteristics of mudstone gradually developing and thickening from the core to the fan end, wells in different depositional areas are selected as standard wells. Through the comparison of multiple well curves, the characteristics of formation changes are intuitively reflected, and relatively stable mudstones are identified as comparison marks and combined; In step 3, the sedimentary pattern of the sandstone fan is comprehensively considered, and the mudstone layer distribution is described by combining well and seismic data in the phase control mode, and the unification and closure of the mudstone layer in the whole area are completed under the constraint of seismic data; According to the different characteristics of mudstone and reservoir in logging response and seismic phase, the mudstone encountered in the standard well is identified and numbered, and the mudstone is tracked according to the number. Combined with the sedimentary characteristics of the sandstone fan, the vertical and horizontal distribution patterns of the mudstone are established, the mudstone layer is closed in the whole area, the system layer division is completed, and the stratigraphic framework is established; In step 4, connected secondary fan stages are developed inside the stable mudstone, and the fractures in the same stage are transformed during the formation fracturing process, and the connectivity is improved. On this basis, the reservoir connectivity is described to improve accuracy.

2. The method for describing connectivity of sandstone reservoirs based on mudstone division according to claim 1, characterized in that: In step 1, the drilled section where the natural potential curve shows a negative anomaly is a sand body, and the high overlap of the three porosity curves reflects that the physical properties of this section are good; conversely, the section where the natural potential curve is straight and the three porosity curves are scattered is a mudstone formation.

3. The method for describing connectivity of sandstone reservoirs based on mudstone division according to claim 1, characterized in that: In step 3, the reservoir shows high resistivity in the logging response, and the three porosity curves of acoustic time difference, neutron and density basically coincide with each other; the seismic profile shows wide and messy weak reflections without obvious reflection axes.

4. The method for describing connectivity of sandstone reservoirs based on mudstone division according to claim 3, characterized in that: In step 3, the resistivity of mudstone in the logging response is low, and the three porosity curves of acoustic time difference, neutron, and density are scattered; the seismic profile shows that the seismic axis reflection is clear and continuous.

5. The method for describing connectivity of sandstone reservoirs based on mudstone division according to claim 1, characterized in that: In step 5, referring to the description results of reservoir connectivity, in accordance with the principle of phase correspondence and advanced water injection, wells with more production sections and fewer mudstone interlayers are selected for injection transfer within the same phase to achieve a higher injection-production correspondence rate; after making injection-production adjustments to the well group, pay close attention to the production situation, use monitoring methods in a timely manner, and further complete the verification of reservoir connectivity through development effectiveness characteristics.

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