Method for determining favorable reservoir development zone

Abstract

The invention discloses a method for determining a reservoir development favorable zone, and relates to the technical field of oil and gas field development, and the method comprises the following steps: S1, collecting research area data; s2, selecting effective wells in the oil and gas wells according to the oil and gas well test yield data in the research area data; s3, determining a beach body development favorable area, a karst development favorable area, a crack development favorable area and a cave development favorable area of the target layer by utilizing the research area data and the effective well; s4, performing map gridding on the four favorable development areas; s5, performing reservoir type judgment on the four favorable development areas after the map gridding; and S6, according to a reservoir type determination result, determining a karst fracture-vug type reservoir development zone. According to the method, the four high-amplitude interfaces of the target layer top, the overlying layer, the underlying layer and the first complete layer of the underlying layer are continuously tracked, the ancient landform of the target layer before deposition and the karst ancient landform are recovered, the basis for judging the geology of a favorable area is more sufficient, and the one-sidedness of a traditional method is overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field development, and more particularly to a method for determining a favorable zone of reservoir development. BACKGROUND

[0002] Carbonate fracture-cave reservoirs are developed in close proximity to ancient weathering crusts, and have complex spatial distribution and interconnection. Such reservoirs can form large oil and gas fields. In the Permian Basin in western Texas, USA, Puckett, Yates, Hobbs and other oil fields, Grosmont oil field in Alberta, Canada, Golden Lane oil field in Mexico, Kharyaga oil field in the Timan-Pechora Basin, Russia, Natih oil field in Oman and Tarim, Tahe and Changqing oil fields in China, fracture-cave type reservoirs have been discovered. Large karst fracture-cave type oil and gas reservoirs have been discovered in multiple blocks in China, and karst fracture-cave type oil and gas reservoirs are one of the important development objects.

[0003] Karst fracture-cave type reservoirs have undergone supergene dissolution, tectonic rupture, burial dissolution, collapse and filling, and are divided into three major karst systems according to the main karst control factors: weathering crust karst system, ancient dark river karst system and fault-controlled karst system. The weathering crust karst system and the ancient dark river karst system are mainly developed in the denudation area, and the fault-controlled karst system is mainly developed in the covered area. Therefore, carbonate karst fracture-cave type oil and gas reservoirs are irregular in shape and complex in spatial distribution. The reservoir scale is controlled by sedimentary facies belts and multiple tectonic movements. The reservoir body has the characteristics of large vertical depth, strong vertical and horizontal heterogeneity, not being controlled by local structural form, and no unified oil-water interface. Therefore, determining the development zone of karst fracture-cave type reservoirs is of great significance for the exploration and development of this type of oil and gas.

[0004] At present, the description of the development zone of karst fracture-cave type reservoirs mainly describes paleogeomorphology and faults. These methods have the following problems: 1) The traditional favorable area uses a single pre-depositional paleogeomorphology or karst paleogeomorphology to select the favorable area, and the geological basis for judging the favorable area is relatively one-sided.

[0005] 2) The conventional method uses a single or double factor to divide the favorable area, and the reservoir type in the favorable area is not determined.

[0006] 3) The conventional method uses a qualitative method to select the favorable area, and the identification and boundary of the favorable area are relatively fuzzy, and the error of the result map is large.

[0007] Karst fracture-cave reservoir development zone is the key for oil and gas exploration and development, and is also the key core for efficient development of oil and gas reservoirs. However, the current method is not fine enough, and the geological basis of the formed map is insufficient. Therefore, the method for determining the karst fracture-cave reservoir development zone is of great significance for the exploration and development of this type of oil and gas reservoir. SUMMARY

[0008] In order to overcome the defects existing in the prior art, the application discloses a method for determining a reservoir development favorable zone. The application continuously tracks four strong amplitude interfaces of the top, overlying, underlying and first complete layer of the underlying of the target layer, restores the pre-deposition paleogeomorphology and karst paleogeomorphology of the target layer, carries out fracture prediction by multiple methods, and verifies by using regional effective wells. The beach development area, karst development area, fracture development area and cave development area and other map are gridded, digitized, and the reservoir type in different superimposed areas is determined to depict the karst fracture-cave reservoir development zone. The application tracks multiple marker layers above and below the target layer, forms a pre-deposition paleogeomorphology map and a karst paleogeomorphology map, and the geological basis is sufficient. The karst fracture-cave reservoir distribution zone is described comprehensively by using multiple result maps. The reservoir type in different regional favorable zones is quickly determined by using digital superposition of different development zones, and the karst fracture-cave reservoir is more convenient to identify. The application can provide a basis for the development of karst fracture-cave oil and gas reservoirs.

[0009] In order to achieve the above purpose, the technical scheme adopted by the application is: A method for determining a reservoir development favorable zone, comprising the following steps: I. Data collection S1, collecting research area data; Preferably, in the step S1, the research area data includes three-dimensional seismic data, logging data, core analysis test data, oil and gas well test data and production dynamic data.

[0010] In the above S1 step, the three-dimensional seismic, logging, core analysis test, oil and gas well test and production dynamic data of the research area are collected, so as to facilitate the use of the subsequent steps. The above research area refers to the planar distribution area of the gas reservoir, or the three-dimensional seismic distribution area corresponding to the gas reservoir.

[0011] II. Effective well optimization S2, in the research area data, selecting effective wells in the oil and gas wells according to the oil and gas well test production data; Preferably, the step S2 includes: excluding the test production data of dry wells and low-yield wells in all oil and gas well test production data, and then selecting the top 80% of oil and gas wells according to the test production data from high to low as effective wells.

[0012] III. Determination of four development favorable zones S3, determining the favorable area of beach development, the favorable area of karst development, the favorable area of fracture development and the favorable area of cave development of the target layer by using the data of the research area and the effective well; In the present application, the favorable area of beach development, the favorable area of karst development, the favorable area of fracture development and the favorable area of cave development of the target layer are determined because: 1. The favorable area of beach development is the material basis for the development of the karst fracture-cave type reservoir, the favorable area of karst development is the high position of the ancient landform where karst is most likely to form, and the favorable area of fracture development and the favorable area of cave development are the fracture area and the fracture-cave area predicted by the earthquake.

[0013] 2. The development of beach and karst is the genetic factor of the karst fracture-cave type reservoir, and the fracture prediction and cave prediction are the seismic inversion performance of the karst fracture-cave type reservoir, which are the essence and phenomenon of each other.

[0014] 3. The single prediction result is a relative favorable area, and the reliability is not absolutely sufficient. Therefore, by combining the prediction maps of the four favorable areas and constraining different prediction favorable areas, the development area of the fracture-cave type reservoir is determined, and the considered factors are more comprehensive.

[0015] In the present application, the target layer refers to the target layer where the gas reservoir is located.

[0016] 1. Horizon tracking Preferably, in the step S3, the determination of the favorable area of beach development and the favorable area of karst development of the target layer comprises the following steps: According to the three-dimensional seismic data in the data of the research area, the top boundary surface of the target layer, the stable base surface above the target layer, the stable base surface below the target layer and the first complete sequence boundary below are determined by well-to-seismic combination, and the position of the target layer boundary surface and the seismic response characteristics are marked. According to the position of the target layer boundary surface and the seismic response characteristics, the horizon tracking is carried out, the distribution law of different marker layers is determined, and the favorable area of beach development and the favorable area of karst development of the target layer are determined.

[0017] 2. Determination of the favorable area A1 of beach development Preferably, in the step S3, the determination of the favorable area of beach development of the target layer comprises the following steps: The stable stratum deposition thickness H1 below the target layer is determined according to the first complete sequence boundary below and the stable base surface below the target layer. The stable stratum deposition thickness map below the target layer is drawn by using the stable stratum deposition thickness H1 below the target layer, which represents the ancient landform before the deposition of the target layer. The favorable area of beach development of the target layer is determined on the stable stratum deposition thickness map below the target layer.

[0018] 3. Determination of the favorable area A2 of karst development Preferably, in the step S3, the favorable area of karst development of the target layer is determined by the following steps: According to the top boundary of the target layer and the overlying stable datum, the thickness H2 of the overlying cover stratum is determined; Using the thickness H2 of the overlying cover stratum, a deposition thickness map of the overlying stable stratum of the target layer is drawn, representing the karst paleogeomorphology of the target layer; The favorable area of karst development of the target layer is determined on the deposition thickness map of the overlying stable stratum of the target layer.

[0019] 4. Determination of the favorable area A3 of fracture development Preferably, in the step S3, the favorable area of fracture development of the target layer is determined by the following steps: According to the three-dimensional seismic data in the research area data, a plurality of fracture prediction methods are used to predict fractures; the plurality of fracture prediction methods include coherence enhancement, chaotic attribute, ant body and maximum likelihood method; The fracture prediction results of the plurality of fracture prediction methods are verified with the effective wells, the fracture prediction result map with the highest coincidence rate with the effective wells is selected, and the favorable area of fracture development of the target layer is determined on the fracture prediction result map.

[0020] 5. Determination of the favorable area A4 of cave development Preferably, in the step S3, the favorable area of cave development of the target layer is determined by the following steps: According to the drilling display and well logging interpretation in the research area data, a fine well-seismic calibration of cave reservoirs is carried out to determine the seismic time window of cave development, the seismic reflection waveform type of cave and the amplitude energy; Using the three-dimensional seismic data in the research area data, the seismic time window of cave reservoir development is initialized, the seismic reflection information related to the cave is extracted, and a cave seismic reflection amplitude energy information map is drawn; The seismic reflection amplitude energy information is verified with the effective wells, the seismic time window of the cave reservoir is optimized and adjusted so that the distribution characteristics of the extracted cave seismic response have the highest coincidence degree with the effective wells; Under the condition of the highest coincidence degree, according to the cave seismic reflection amplitude energy information map, combined with the cave seismic reflection waveform type and the amplitude energy intensity, the favorable area of cave development of the target layer is determined on the cave seismic reflection amplitude energy information map.

[0021] Four, map gridding S4, the favorable area of beach development, the favorable area of karst development, the favorable area of fracture development and the favorable area of cave development are subjected to map gridding; Preferably, in the step S4, the map gridding includes: the grid size is the same as the coordinate, the grid size is not greater than 50m*50m, and each grid development area is assigned a value.

[0022] Preferably, in the S4 step, the value assignment to each grid development area includes: for the development area, the values of beach body, karst, fracture and cave are 1, 10, 100 and 1000 respectively; for the non-development area, the values of beach body, karst, fracture and cave are all 0.

[0023] V. Reservoir type determination S5, reservoir type determination is performed on the grid-based favorable area of beach body development, the grid-based favorable area of karst development, the grid-based favorable area of fracture development and the grid-based favorable area of cave development. Preferably, in the S5 step, the reservoir type determination includes: adding the grid values corresponding to the same coordinates in the grid-based favorable area of beach body development, the grid-based favorable area of karst development, the grid-based favorable area of fracture development and the grid-based favorable area of cave development to obtain a grid digital superimposed map, and determining the reservoir type of different areas according to the grid value R of the superimposed map.

[0024] In the present application, the grid value superimposition refers to adding the grid values corresponding to the same coordinates in the four maps (the grid value in A1 + the grid value in A2 + the grid value in A3 + the grid value in A4).

[0025] Preferably, in the S5 step, the reservoir type of different areas is determined according to the grid value R of the superimposed map, including: R≤10, it is considered that the reservoir is not developed, so no determination is made; When 10<R<100, the reservoir type is pore or hole type; When R=100, the reservoir type is fracture type; When 100<R<1000, the reservoir type is fracture-hole type or fracture-pore type; When R≥1000, the reservoir type is large fracture-hole type.

[0026] VI. Determination of karst fracture-cave type reservoir development zone S6, determining the karst fracture-cave type reservoir development zone according to the reservoir type determination result.

[0027] Preferably, in the S6 step, the karst fracture-cave type reservoir development zone is a large fracture-hole type reservoir development zone.

[0028] Advantages of the present application: 1. The traditional favorable area adopts a single sedimentary pre-paleogeomorphology or karst paleogeomorphology for favorable area optimization; the present application continuously tracks the top, overlying, underlying and first complete layer of the underlying four strong amplitude interfaces of the target layer, restores the sedimentary pre-paleogeomorphology and karst paleogeomorphology, and provides more sufficient geological basis for favorable area determination, overcoming the one-sidedness of the traditional method.

[0029] 2、The fracture prediction of the present application carries out a plurality of methods, and adopts the regional effective well to verify, and the fracture development law prediction is high in conformity degree.

[0030] 3、The present application adopts a plurality of drawings such as beach body development area, karst development area, fracture development area and cave development area in the determination process of karst fracture-cave reservoir development zone, and determines the reservoir type of the superimposed area of different drawings, and the geological basis of the reservoir distribution area is strong.

[0031] 4、The present application carries out gridding on different geological drawings, and assigns values to different development areas, realizes drawing digitization, and is more convenient in the superimposition of a plurality of drawings and the determination of different types of reservoirs. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The flow chart of the method for determining the karst fracture-cave reservoir development zone of the present application; Figure 2 The main tracking horizon schematic diagram of the method for determining the karst fracture-cave reservoir development zone of the present application; Figure 3 The underlying stable stratum sediment thickness H1 and the beach body development favorable area in the embodiment of the present application; Figure 4 The overlying stable stratum sediment thickness H2 and the karst development favorable area in the embodiment of the present application; Figure 5 The chaotic attribute fracture prediction and the fracture development favorable area in the embodiment of the present application; Figure 6 The cave corresponding bright point response and the cave development favorable area in the embodiment of the present application; Figure 7 The karst fracture-cave reservoir development favorable zone in the embodiment of the present application. DETAILED DESCRIPTION

[0033] The concept, specific structure and generated technical effects of the present application will be described clearly and completely in combination with the embodiments and drawings, so as to fully understand the purpose, features and effects of the present application.

[0034] Taking the Maokou group gas reservoir of LWC gas field as an example, the sedimentary facies of Maokou group gas reservoir is open sea platform facies, in which Maer~Maes three are a plurality of high-energy and low-energy bioclastic beach superimposed, and Maer, Maes four are mainly open sea. Affected by the Dongwu movement, the stratum is uplifted, the Maokou group is subjected to denudation, LWC is in karst slope belt, and Maes four is not completely denuded. Maokou group and overlying Longtan group are in unconformable contact, Longtan group is mud shale, and the sedimentation is stable; Maokou group and underlying Qixia group are in conformable contact.

[0035] A method for determining a reservoir development favorable zone, as shown in Figure 1 , comprising the following steps: (1) Data collection The 3D seismic, well logging, core analysis, oil and gas well testing and production dynamic data of the study area were collected.

[0036] The 3D seismic data of LWC area covers 110 km 2 , and the well logging data of 6 wells. LWC gas field has a total of 15 drilled wells, 13 of which are drilled in the Maokou Formation, and 11 of which are gas wells in the Maokou Formation. There are 10 historical production wells in the LWC Maokou Formation gas reservoir.

[0037] (2) Effective well optimization As shown in Table 1, according to the test production data of all oil and gas wells, the test data of dry wells, low-yield wells and the like are excluded, and the top 80% of oil and gas wells are sorted according to the test production from high to low as effective wells.

[0038] Table 1 Effective well judgment results in the example (3) Horizon tracking As Figure 2 shown, according to the 3D seismic data of the study area, the top boundary of the target layer (C) Longtan Formation bottom, the overlying stable datum (U) Feixianguan Formation bottom, the underlying stable datum (D) Maokou Formation bottom, and the first complete sequence boundary (P) Maerzhen bottom, the seismic reflection response characteristics of the Longtan Formation bottom, the Feixianguan Formation bottom, the Maokou Formation bottom and the Maerzhen bottom are all strong peak reflections; The horizon calibration mainly calibrates the position of the main target layer boundary and the seismic response characteristics; According to the seismic response characteristics of the main target layer boundary, the horizon tracking is carried out to determine the distribution law of different marker beds.

[0039] (4) Favorable area of beach body development (A1) The underlying stable stratum sediment thickness H1 of the target layer is determined according to the first complete sequence boundary (P) Maerzhen bottom and the underlying stable datum (D) Maokou Formation bottom; The underlying stable stratum sediment thickness map of the target layer is drawn, which represents the paleogeomorphology before the target layer deposition; According to the paleogeomorphology before the target layer deposition, the favorable area of beach body development (A1) of the target layer is determined, as Figure 3 shown.

[0040] (5) Favorable area of karst development (A2) The overlying stratum thickness H2 is determined according to the top boundary of the target layer (C) Longtan Formation bottom and the overlying stable datum (U) Feixianguan Formation bottom; The overlying stable stratum sediment thickness map of the target layer is drawn, which represents the karst paleogeomorphology of the target layer; According to the karst paleogeomorphology of the target layer (imprint method), the favorable area of karst development of the target layer (A2) is determined, as shown in Figure 4 . .

[0041] (6) Favorable area of fracture development (A3) According to the three-dimensional seismic data, the fracture prediction is carried out by using multiple methods such as coherence enhancement, chaotic attribute, ant body and maximum likelihood; The multiple fracture prediction results are verified by using the effective wells, the coincidence rate of the fracture prediction result of the chaotic attribute with the effective wells is high, the favorable area of fracture development of the target layer (A3) is determined, as shown in Figure 5 . .

[0042] (7) Favorable area of cave development (A4) According to the drilling display and well logging interpretation in the research area data, the fine well-seismic calibration of the cave reservoir is carried out, the seismic time window of the cave development, the seismic reflection waveform type and the amplitude energy of the cave are determined; The seismic time window of the cave reservoir development is initialized by using the three-dimensional seismic data in the research area data, the seismic reflection information related to the cave is extracted, and the seismic reflection amplitude energy information map of the cave is drawn; The seismic reflection amplitude energy information is verified by using the effective wells, the seismic time window of the extraction of the cave reservoir is optimized and adjusted, so that the coincidence degree of the distribution characteristics of the extracted cave seismic response with the effective wells is the highest; Under the condition of the highest coincidence degree, according to the cave seismic reflection amplitude energy information map, combined with the cave seismic reflection waveform type and the amplitude energy intensity, and the favorable area of cave development of the target layer (A4) is determined on the cave seismic reflection amplitude energy information map, as shown in Figure 6 . .

[0043] (8) Grid of map The four map pieces of the favorable area of beach development (A1), the favorable area of karst development (A2), the favorable area of fracture development (A3) and the favorable area of cave development (A4) are gridded, the grid size and coordinates are consistent, the grid size is 20m*20m, and each grid development area is valued, and the value size is shown in Table 2: Table 2 Value assignment of different map development areas . . (9) Reservoir type determination The grid values with the same coordinates in the map pieces of the favorable area of beach development (A1), the favorable area of karst development (A2), the favorable area of fracture development (A3) and the favorable area of cave development (A4) are added, the grid digital superposition map is obtained, the reservoir types of different regions are determined according to the value size, and the reservoir type determination standard is shown in Table 3: Table 3 Reservoir type determination standard of different regions (10) Karst fracture-cave type reservoir development zone According to the grid numerical size, the reservoir types in different regions are determined, and a large fracture-cave type reservoir development zone is a karst fracture-cave type reservoir development zone, as shown in FIG. 10. Figure 7

[0044] The above describes the embodiments of the present application in detail, but the present application is not limited to the above-mentioned embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.​

Claims

1. A method of determining reservoir development sweet spots, characterized by, The method comprises the following steps: S1, collecting research area data; S2, in the research area data, selecting effective wells in oil and gas wells according to the test production data of the oil and gas wells; S3, using the research area data and the effective wells, determining the favorable area of beach development, the favorable area of karst development, the favorable area of fracture development and the favorable area of cave development of the target layer; S4, griding the favorable area of beach development, the favorable area of karst development, the favorable area of fracture development and the favorable area of cave development of the target layer; S5, determining the reservoir type of the grided favorable area of beach development, the favorable area of karst development, the favorable area of fracture development and the favorable area of cave development of the target layer; S6, according to the determination result of the reservoir type, determining the development zone of the karst fracture-cave type reservoir.

2. A method of determining a reservoir development sweet spot according to claim 1, wherein, The step S2 comprises: excluding the test production data of dry wells and low-yield wells in all the test production data of oil and gas wells, and then selecting the top 80% of the oil and gas wells according to the test production data from high to low as effective wells.

3. A method of determining a reservoir development sweet spot according to claim 1, wherein, In the step S3, the determination of the favorable area of beach development and the favorable area of karst development of the target layer comprises the following steps: According to the three-dimensional seismic data in the research area data, the top boundary of the target layer, the stable base surface above the target layer, the stable base surface below the target layer and the first complete sequence boundary below are determined by well-to-seismic combination, and the position and seismic response characteristics of the target layer boundary are marked; According to the position and seismic response characteristics of the target layer boundary, the horizon tracking is carried out to determine the distribution law of different marker beds and the favorable area of beach development and the favorable area of karst development of the target layer.

4. A method of determining a reservoir development sweet spot according to claim 3, wherein, In the step S3, the determination of the favorable area of beach development of the target layer comprises the following steps: The stable stratum deposition thickness H1 below the target layer is determined according to the first complete sequence boundary below and the stable base surface below the target layer; The stable stratum deposition thickness map of the target layer below is drawn by using the stable stratum deposition thickness H1 below the target layer, which represents the ancient landform before the deposition of the target layer; The favorable area of beach development of the target layer is determined on the stable stratum deposition thickness map of the target layer below.

5. A method of determining a reservoir development sweet spot according to claim 3, wherein, In the step S3, the determination of the favorable area of karst development of the target layer comprises the following steps: The overlying stratum thickness H2 is determined according to the top boundary of the target layer and the stable base surface above the target layer; The stable stratum deposition thickness map of the target layer above is drawn by using the overlying stratum thickness H2, which represents the karst ancient landform of the target layer; The favorable area of karst development of the target layer is determined on the stable stratum deposition thickness map of the target layer above.

6. A method of determining a reservoir development sweet spot according to claim 1, wherein, In the step S3, the determination of the favorable area of fracture development of the target layer comprises the following steps: According to the three-dimensional seismic data in the research area data, a plurality of fracture prediction methods are used to predict fractures; the plurality of fracture prediction methods comprise coherence enhancement, chaotic attribute, ant body and maximum likelihood method; The fracture prediction result maps of the plurality of fracture prediction methods are verified with the effective wells, the fracture prediction result map with the highest coincidence rate of fracture development area and effective wells is selected, and the favorable area of fracture development of the target layer is determined on the fracture prediction result map.

7. A method of determining a reservoir development sweet spot according to claim 1, wherein, In the step S3, the determination of the favorable area of cave development of the target layer comprises the following steps: According to the drilling display and well logging interpretation in the research area data, fine well-seismic calibration of cave reservoir is carried out to determine the seismic time window of cave development, the seismic reflection waveform type of cave and the amplitude energy; Using the 3D seismic data in the research area data, the seismic time window of cave reservoir development is initialized, the seismic reflection information related to cave is extracted, and the seismic reflection amplitude energy information map of cave is drawn; The seismic reflection amplitude energy information is verified with effective wells, and the seismic time window of extracting cave reservoir is optimized and adjusted, so that the distribution characteristics of the extracted cave seismic response are most consistent with the effective wells; Under the condition of the highest consistency, according to the cave seismic reflection amplitude energy information map, combined with the cave seismic reflection waveform type and amplitude energy intensity, and the favorable area of cave development in the target layer is determined on the cave seismic reflection amplitude energy information map.

8. The method of determining reservoir development sweet spots of claim 1, wherein, In S4, the grid of the drawing includes: grid size, same coordinates, and grid no more than 50m*50m, and each grid development area is assigned a value, including: For the development area, the values of beach, karst, fracture and cave are 1, 10, 100 and 1000 respectively; for the non-development area, the values of beach, karst, fracture and cave are all 0.

9. A method of determining a reservoir development sweet spot according to claim 1, wherein, In S5, the reservoir type determination includes: adding the corresponding grid values in the drawing of beach development favorable area, karst development favorable area, fracture development favorable area and cave development favorable area after grid of the drawing, obtaining the grid digital superimposed drawing, and determining the reservoir type of different areas according to the grid value R of the superimposed drawing, including: When 10<R<100, the reservoir type is pore or pore type; When R=100, the reservoir type is fracture type; When 100<R<1000, the reservoir type is fracture-pore type or fracture-pore type; When R≥1000, the reservoir type is large fracture-cave type.

10. The method of determining reservoir development sweet spots of claim 1, wherein, In S6, the karst fracture-cave type reservoir development area is large fracture-cave type reservoir development area.

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