Exploration method for shallow stratum-lithology reservoir in gentle slope zone of faulted basin

Abstract

The present application provides a kind of exploration method for shallow strata-lithology reservoir in gentle slope zone of faulted basin, the exploration method for shallow strata-lithology reservoir in gentle slope zone of faulted basin comprises: step 1, the fine comparison of strata, division and logging facies analysis are carried out by comprehensively utilizing geology, well logging data;Step 2, the strata overstripping point is accurately described by applying seismic reflection angle extrapolation and instantaneous phase technology, and the fine tracking interpretation of structural horizon is realized;Step 3, the reservoir is finely described by applying frequency division technology;Step 4, according to the matching relationship of each accumulation element, the accumulation rule is summarized, the accumulation mode is established, and the favorable area prediction is realized.The exploration method for shallow strata-lithology reservoir in gentle slope zone of faulted basin has remarkable application effect in the study area, and can be applied to other exploration areas, especially provides basis for the favorable exploration direction and zone prediction of shallow overstripping type reservoir in gentle slope zone.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration, in particular to a method for exploring a shallow stratigraphic-lithologic reservoir in a gentle slope zone of a faulted basin. BACKGROUND

[0002] In recent years, with the deepening of the exploration degree of oil and gas fields in eastern China, the object of oil and gas exploration has shifted from structural oil and gas reservoirs to the exploration of subtle oil and gas reservoirs. As a kind of subtle reservoir, the lithologic-stratigraphic reservoir in the gentle slope zone of the oil and gas-bearing faulted basin has become an important position for increasing reserves and production in the oil and gas-bearing faulted basin in China. There is no systematic evaluation method and matching technology for reservoir description and super-unstripping point identification for the lithologic-stratigraphic reservoir in the gentle slope zone of the oil and gas-bearing faulted basin. This type of reservoir has considerable potential, and as a whole, it is difficult to describe the reservoir due to its thin reservoir thickness, large lateral variation, strong "subtlety" and high exploration risk.

[0003] The currently used reservoir description techniques include amplitude energy tracking technology based on conventional seismic and well logging constrained inversion technology based on wave impedance. The advantage of amplitude energy tracking technology is to qualitatively describe short-axis and strong-reflecting channel sand bodies with obvious seismic reflection characteristics (sand ratio 15%, single layer >10m), while the boundary of continuous reflection layer sand bodies cannot be accurately described, and the boundary of thin reservoirs cannot be clearly described. The well logging constrained inversion technology uses seismic traces as original data and uses deconvolution method to invert wave impedance, which can improve the accuracy of reservoir description and prediction, and the accuracy of boundary description of continuous reflection layer sand bodies is improved, but there are many artificial factors, and the accuracy of reservoir boundary description is still low. At present, the description of denudation line mainly uses seismic attribute and waveform analysis technology, which requires high quality of seismic data. Under the existing quality of seismic data, it is impossible to achieve fine description of denudation line.

[0004] In the Chinese patent application with application number CN201910536456.2, a method, device and system for exploring a lithologic oil and gas reservoir in a faulted basin are disclosed. The method includes dissecting the target layer of the developed oil and gas reservoir to obtain a plurality of oil and gas reservoir units; determining the corresponding accumulation mechanism information of the oil and gas reservoir units according to the oil and gas reservoir units; analyzing the oil and gas reservoir units according to the accumulation mechanism information to determine the enrichment mode information of the complex oil and gas reservoir; and performing zone evaluation according to the accumulation mechanism information and the enrichment mode information to predict the exploration direction of the lithologic oil and gas reservoir.

[0005] In the Chinese patent application with the application number CN201410117049.5, a method for exploring the distribution of reservoirs in the slope zone of a faulted lake basin is disclosed, which belongs to the technical field of oil exploration. The method is used for the late stage of faulted lake basin exploration. By statistically analyzing the relevant information of source rocks, fluid potential, sedimentary facies and faults in the target area, and based on the source-potential-facies guide principle, the above information is comprehensively analyzed to determine the favorable reservoir distribution area in the target area.

[0006] In the Chinese patent application with the application number CN202010177989.9, a comprehensive evaluation method for selecting favorable areas of middle-small faulted basin coalbed methane reservoirs is disclosed. The method includes: 1. evaluating the gas generation capacity of the target coal seam; 2. evaluating the reservoir capacity of the target coal seam; 3. evaluating the preservation conditions of the target coal seam; 4. evaluating the permeability of the target coal seam; 5. determining the main controlling factors of the target coalbed methane reservoir, predicting the distribution characteristics of each main controlling factor using well logging, seismic and experimental analysis data in the study area, superimposing the favorable areas of each main controlling factor, and comprehensively analyzing and predicting the favorable high-permeability enrichment area.

[0007] The above prior art has great differences from the present application and cannot solve the technical problems we want to solve. The prior art has poor adaptability in describing sand bodies due to the sedimentary characteristics of the faulted basin depression gentle slope zone, such as thin reservoir thickness, large lateral variation, and thin interbedded sand and mud. Therefore, a new method for exploring middle-shallow stratigraphic-lithologic reservoirs in the gentle slope zone of a faulted basin is invented. SUMMARY

[0008] The purpose of the present application is to provide a method for exploring middle-shallow stratigraphic-lithologic reservoirs in the gentle slope zone of a faulted basin, which solves the problems of low precision in describing the interbedded sand and mud in the gentle slope zone of a faulted basin depression and in depicting the denudation line of the stratum, thereby improving the success rate of exploration of such reservoirs.

[0009] The purpose of the present application can be achieved by the following technical measures: a method for exploring middle-shallow stratigraphic-lithologic reservoirs in the gentle slope zone of a faulted basin, which comprises:

[0010] Step 1: comprehensively utilizing geological and logging data to finely correlate, divide and analyze the logging facies of the stratum;

[0011] Step 2: applying seismic reflection angle extrapolation and instantaneous phase technology to accurately depict the stratum over-eroded points and realize fine tracking interpretation of the structural horizon;

[0012] Step 3: applying frequency division technology to finely describe the reservoir;

[0013] Step 4: based on the matching relationship of each reservoir-forming element, summarizing the reservoir-forming rules, establishing a reservoir-forming pattern, and realizing the prediction of favorable areas.

[0014] The object of the present application can also be achieved by the following technical measures:

[0015] In step 1, the stratum development in different regions, the sandstone and mudstone sedimentary characteristics and the sedimentary types are clarified through fine comparison of the geological and logging data of the completed well, stratum division and logging facies analysis.

[0016] In step 2, the instantaneous phase technology is a processing method based on Hilbert transform, which reflects the continuity of the reflected wave. The steps of accurately depicting the super-erosion point of the stratum by using the instantaneous phase technology include:

[0017] ① inputting the three-dimensional seismic data;

[0018] ② converting the conventional seismic data body into an instantaneous phase body;

[0019] ③ performing structural interpretation in the instantaneous phase body according to the Inline and Crossline directions. Compared with the conventional seismic section, the erosion phenomenon is more clear.

[0020] In step 2, the steps of accurately depicting the super-erosion point by using the seismic reflection angle extrapolation include:

[0021] Step 2a, performing structural interpretation and mapping;

[0022] Step 2b, establishing multiple geological models;

[0023] Step 2c, performing forward modeling on the geological models to obtain the forward seismic section corresponding to the geological models;

[0024] Step 2d, establishing a stratum angle extrapolation stratum erosion pinch-out line extrapolation template;

[0025] Step 2e, applying the template of step 2d to correct the structural map of the target layer in step 2a to obtain a new corrected geological structural map.

[0026] In step 2a, the time-depth relationship is established by using the artificial seismic synthetic record or the VSP data in the region, the stratum correlation result in step 1 is calibrated to the seismic section corresponding to the well location, the target layer and the unconformity surface are tracked and interpreted according to the calibration result, and the target layer and the unconformity surface interpretation result is converted into the depth domain geological structural map by using the time-depth relationship.

[0027] In step 2b, the stratum development in the region, the sandstone and mudstone sedimentary characteristics and the sedimentary types in step 1 and the interpretation result of the target layer and the unconformity surface in step 2a are applied to establish multiple geological models with different combinations of stratum dip angle and unconformity dip angle.

[0028] In step 2c, the wavelet is extracted in the time window corresponding to the target layer in the seismic data, and is convolved with the reflection coefficients of each stratigraphic interface of the geological model established in step 2b to perform forward calculation and obtain a forward seismic profile corresponding to each geological model.

[0029] In step 2d, the seismic profile obtained by forward calculation of each geological model is compared with the geological model to obtain the corresponding relationship between the stratigraphic dip angle and the unconformity dip angle combination and the stratigraphic dip angle and the extrapolation distance of the stratigraphic erosion pinchout point, and the extrapolation template of the stratigraphic erosion pinchout line is obtained by fitting calculation.

[0030] In step 2e, a plurality of control points are selected on the pinchout line of the target layer structure map in step 2a, the dip angles of the target layer and the unconformity surface corresponding to the control points are read to obtain the stratigraphic dip angle corresponding to the control points, the extrapolation distance of the control points is obtained according to the pinchout line extrapolation template in step 2d, and the corrected pinchout point or the overlap point corresponding to the control points is determined. All the corrected pinchout points or overlap points are connected in sequence to obtain a corrected pinchout line, the depths of the points on the connecting line of the control points and the corresponding pinchout points or overlap points are calculated according to the depths of the control points and the stratigraphic dip angle, and all the isobaths on the connecting line of the control points and the corresponding pinchout points or overlap points are connected in sequence to obtain the corresponding isobaths, and finally a new corrected geological structure map is obtained. The connecting line of the control points and the corresponding pinchout points, the two limbs of the stratigraphic dip angle and the unconformity dip angle are in the same vertical plane.

[0031] Step 3 includes:

[0032] (a) selecting a suitable time window in the seismic data volume, and intercepting the seismic data volume containing the target layer within a certain time range, and converting the information in the time domain to the frequency domain by using the time-frequency analysis method;

[0033] (b) decomposing the intercepted seismic data volume into a plurality of frequency domain data volumes according to a certain frequency band;

[0034] (c) by adjusting the time window length, observing the response characteristics of the target sand body under different frequencies, selecting the data volume of the dominant frequency reflecting the obvious response characteristics of the target sand body, and merging and stacking the data volume for sand body description, and finally obtaining a comprehensive frequency map of the region;

[0035] (d) according to the target layer calibrated in step (a) and the data volume obtained in step (c), performing seismic interpretation and tracking of the sand body, and the phase axis change point is the boundary of the sand body description.

[0036] In step 4, the accumulation law summary includes oil and gas source analysis, reservoir and cap rock combination analysis, carrier system analysis and reservoir type analysis; the oil and gas source analysis mainly uses geochemical analysis test data to determine the oil and gas source by oil source comparison; the reservoir and cap rock combination analysis mainly analyzes the matching relationship of the reservoir and the cap rock, the reservoir research mainly includes physical property, pore throat structure and favorable reservoir distribution area prediction; the cap rock research mainly includes the property of the cap rock and the distribution on the plane; the carrier system analysis mainly includes the research on the carrier action of faults, sand bodies and unconformity to oil and gas; the reservoir is controlled by multiple factors such as sedimentary facies, stratum and structure, and on the basis of the main control factor analysis of the reservoir, the reservoir type analysis is carried out.

[0037] The exploration method of the middle-shallow stratum-lithology reservoir in the gentle slope zone of the faulted basin in the application comprehensively utilizes geological and logging data to perform fine stratum division and comparison; based on the stratum super-unstripping contact relationship of the gentle slope zone, the stratum super-unstripping point is accurately described by using the seismic reflection angle extrapolation and instantaneous phase technology, and then the fine tracking of the structural horizon is realized; in combination with the stratum comparison and the sedimentary type, the reservoir characteristics are researched, the thin sandstone and mudstone interbedded layer is difficult to distinguish by using the conventional seismic data, and the frequency division technology is used to finely describe the reservoir; according to the matching relationship of various reservoir elements, the accumulation law is summarized, the reservoir forming mode is established, and thus the favorable area prediction is realized, which plays a certain guiding role for the exploration and development of the gentle slope zone reservoir. The application effect is remarkable in the research area, and can be popularized and applied to other exploration areas, especially provides a basis for the favorable exploration direction and zone prediction of the middle-shallow super-unstripping type reservoir in the gentle slope zone. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a conventional seismic profile and instantaneous phase profile in a specific embodiment of the application;

[0039] Figure 2 It is a schematic diagram of forward modeling of the stratum denudation pinch-out line of the Sha 2 member in the Cao 702 well area in a specific embodiment of the application;

[0040] Figure 3 It is a schematic diagram of quantitative extrapolation template of the stratum denudation pinch-out line of the Sha 2 member in the Cao 702 well area in a specific embodiment of the application;

[0041] Figure 4 It is a schematic diagram of the theoretical basis of the frequency division technology in a specific embodiment of the application;

[0042] Figure 5 It is a 32 frequency division attribute graph (70-90Hz) of the Sha 2 member in the Cao 702 well area in a specific embodiment of the application;

[0043] Figure 6 It is a 32 frequency division attribute graph (comprehensive frequency) of the Sha 2 member in the Cao 702 well area in a specific embodiment of the application;

[0044] Figure 7 Fig. 7 is a diagram of a reservoir-forming mode of the well area 702 in a specific embodiment of the present application;

[0045] Figure 8 Fig. 1 is a flow chart of a method for exploring a shallow stratigraphic-lithologic reservoir in a gentle slope zone of a faulted basin in a specific embodiment of the present application. DETAILED DESCRIPTION

[0046] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0047] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It is further noted that the terms "comprise" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0048] As shown in Fig. 1, Figure 8 Figure 8 Fig. 1 is a flow chart of a method for exploring a shallow stratigraphic-lithologic reservoir in a gentle slope zone of a faulted basin in a specific embodiment of the present application.

[0049] Step 101, fine correlation, division and logging facies analysis of strata are performed by comprehensively using geological and logging data;

[0050] By fine correlation, division and logging facies analysis of strata of geological and logging data of a completed well, the stratum development in different regions, sandstone and shale sedimentary characteristics and sedimentary types are clarified, thereby providing guidance for subsequent work.

[0051] Step 102, stratum denudation points are precisely depicted by using seismic reflection angle extrapolation and instantaneous phase technology, and fine structure horizon tracking interpretation is realized;

[0052] The instantaneous phase technology is a processing method based on Hilbert transform, which is only a function of time and is irrelevant to seismic wave energy, and reflects the continuity of reflected waves, thereby improving the interpretation accuracy of denudation points. The specific steps are as follows:

[0053] (4) input three-dimensional seismic data;

[0054] (5) convert the conventional seismic data volume into an instantaneous phase volume;

[0055] ​⑥ In the instantaneous phase volume, the tectonic interpretation is carried out according to the Inline (longitudinal line) and Crossline (cross line) directions. Compared with conventional seismic profiles, the erosion phenomenon is clearer.

[0056] Seismic reflection angle extrapolation is necessary because the resolution of seismic data limits the identification of over-exfoliation points. There is a certain distance between the points identified by seismic data and the actual stratigraphic boundaries. Therefore, seismic reflection angle extrapolation is needed to accurately characterize these over-exfoliation points. The specific steps are as follows:

[0057] Step 2a: Perform structural interpretation and mapping; establish time-depth relationships using synthetic seismic records or local VSP (Vertical Seismic Profiling) data, and pinpoint the stratigraphic correlation results from Step 101 to the seismic profile corresponding to the well location. Based on the pinpointing results, trace and interpret the target layer and unconformity, and use the time-depth relationships to convert the interpretation results of the target layer and unconformity into a geological structural map of the depth domain.

[0058] Step 2b: Establish multiple geological models; using the stratigraphic development, sandstone and mudstone sedimentary characteristics and sedimentary types of the region clarified in Step 101, and the interpretation results of the target layer and unconformity surface in Step 2a, establish multiple geological models with different stratigraphic dip angles and unconformity dip angle combinations.

[0059] Step 2c: Perform forward modeling on the geological model to obtain the forward seismic profile corresponding to the geological model; extract the wavelet from the time window corresponding to the target layer in the seismic data, and convolve it with the reflection coefficient of each stratigraphic interface of the geological model established in step 2b, and perform forward modeling to obtain the forward seismic profile corresponding to each geological model.

[0060] Step 2d: Establish the extrapolation template for stratigraphic angle extrapolation and stratigraphic erosion pinch-out line extrapolation; by comparing the seismic profile obtained by forward modeling of each geological model with the geological model, the correspondence between stratigraphic angle and extrapolation distance of stratigraphic erosion pinch-out point corresponding to different stratigraphic dip angles and unconformity dip angle combinations is obtained, and the extrapolation template for stratigraphic erosion pinch-out line extrapolation for different stratigraphic angles is obtained through fitting calculation.

[0061] Step 2e, the template of step 2d is applied to correct the target layer structure map in step 2a to obtain a new corrected geological structure map. A plurality of control points are selected on the pinch-out line of the target layer structure map in step 2a, the dip angles of the target layer and the unconformity corresponding to the control points are read to obtain the stratum angle corresponding to the control points, the extrapolation distance of the control points is obtained according to the pinch-out line extrapolation template in step 2d, and then the corrected pinch-out point or overlap point corresponding to the control points is determined, the corrected pinch-out points or overlap points are sequentially connected to obtain the corrected pinch-out line, the depths of the points on the connecting line of the control points and the corresponding pinch-out points or overlap points are calculated according to the depths of the control points and the stratum dip angle, and the isobath points on the connecting line of the control points and the corresponding pinch-out points or overlap points are sequentially connected to obtain the corresponding isobath, and finally a new corrected geological structure map is obtained.

[0062] The connecting line of the control points and the corresponding pinch-out points, the two limbs of the stratum dip angle and the unconformity dip angle are in the same vertical plane.

[0063] Step 103, the reservoir is finely described by using frequency division technology; the frequency division technology is based on the difference in seismic reflection frequency characteristics of sand bodies with different thicknesses and areas. For relatively thick layers, the frequency changes slightly, and the thickness also changes. For thin layers of 1-5m, the frequency changes by tens of hertz, and the stratum thickness changes by about 1m. The specific steps of the technology are as follows:

[0064] (a) selecting a suitable time window in the seismic data volume, and intercepting the seismic data volume containing the target layer within a certain time range, and converting the information in the time domain to the frequency domain by using time-frequency analysis method;

[0065] (b) the intercepted seismic data volume is divided into a plurality of frequency domain data volumes according to a certain frequency band in the frequency division software;

[0066] (c) by adjusting the time window length, the response characteristics of the target sand body under different frequencies are observed, the data volume of the dominant frequency reflecting the obvious response characteristics of the target sand body is selected and stacked for sand body description, and finally the comprehensive frequency map of the region is obtained;

[0067] (d) according to the target layer calibrated in step (a) and the data volume obtained in step (c), the sand body is interpreted and tracked, and the phase axis change point is the sand body description boundary.

[0068] Step 104, according to the matching relationship of each reservoir forming element, the reservoir forming rule is summarized, the reservoir forming mode is established, and the favorable area is predicted.

[0069] The summary of hydrocarbon accumulation patterns includes analyses of hydrocarbon source, reservoir-capsule combination, transport system, and reservoir type. Hydrocarbon source analysis primarily utilizes geochemical analysis data to compare and determine the origin of hydrocarbons. Reservoir-capsule combination analysis focuses on the matching relationship between reservoirs and caprocks. Reservoir studies mainly include physical properties, pore-throat structure, and prediction of favorable reservoir distribution areas. Caprock studies mainly include the properties and planar distribution of caprocks. Transport system analysis mainly includes the study of the transport effects of faults, sand bodies, and unconformities on hydrocarbons. Since reservoirs are controlled by multiple factors such as sedimentary facies, stratigraphy, and structure, reservoir type analysis is conducted based on the analysis of the main controlling factors.

[0070] In a specific embodiment 1 of the present invention, the Sha-2 section of the Cao 702 well area is used as an example for illustration. Before the method of the present invention was applied to this work area, exploration wells such as Cao 702, Cao 701, and Cao 335 had been drilled in this area, but production had not yet been started.

[0071] 1. Utilize geological, well logging, and other data to conduct detailed stratigraphic division and correlation.

[0072] The Guantao Formation in the Cao 702 well area directly overlies the Sha-2 Member. At the bottom of Guantao, a 15-20m thick layer of stable mudstone sediments separates it from the Sha-2 Member. From the bottom of the Sha-2 Member towards the Sha-3 Member, the sandstone gradually transitions into a 5-10m thick layer of stable mudstone sediments, which then evolves into the thick massive sandstone sediments of the Sha-3 Member.

[0073] 2. Based on the stratigraphic over-exfoliation contact relationship in the gentle slope zone, seismic reflection angle extrapolation and instantaneous phase technology are used to accurately characterize the stratigraphic over-exfoliation points, thereby achieving fine tracking of structural strata.

[0074] Different types of seismic data have varying resolution capabilities for pinch-out lines of over-exfoliated strata. Instantaneous phase profiles, because they eliminate the influence of seismic amplitude and only reflect the rate of phase change, can improve the resolution of pinch-out points. We use a comparison between seismic profiles and instantaneous phase profiles for interpretation, highlighting the advantages of instantaneous phase profiles and overcoming their problems of excessive lateral interference and difficulty in continuous tracking. According to an example of this invention, inputting three-dimensional seismic data transforms the conventional seismic data volume into an instantaneous phase volume. Within the instantaneous phase volume, structural interpretation is performed according to the inline and crossline directions. Compared to conventional seismic profiles, the erosion phenomenon is much clearer. Figure 1 ).

[0075] According to the forward modeling results, the erosion pinch-out points of the Sha-2 Member strata in the Cao-702 well area generally exhibit blank reflection characteristics near the overlying strata. However, the actual erosion pinch-out points can be extrapolated along the angle between the Sha-2 Member and the overlying strata, and extended outward along the strike direction of the Sha-2 Member strata. Figure 2). Based on the above understanding, in order to accurately implement the position of the stratigraphic pinch-out point, a stratigraphic erosion pinch-out line forward model based on different stratigraphic angle extrapolation is further established, the corresponding relationship between the stratigraphic angle and the extrapolation distance of the stratigraphic erosion pinch-out point is obtained (Table 1), and through fitting calculation, the stratigraphic erosion pinch-out line extrapolation template based on the base layer angle extrapolation is established Figure 3 Through the power index relationship between the dip angle difference and the change of the stratigraphic pinch-out point and the corresponding template, the scientific and quantitative extrapolation of the stratigraphic erosion pinch-out line is realized. Compared with the original interpretation scheme, the implementation range of the erosion line of the second member of Shahejie Formation in Cao 702 well area is moved south relative to the original interpretation, the stratigraphic angle is 5-20 degrees, and the southward extrapolation distance is about 50-200 meters. On the basis of artificial interpretation, the distance is increased, and the final corrected pinch-out or overlap position is obtained.

[0076] Table 1 Stratigraphic angle and stratigraphic erosion pinch-out point extrapolation distance statistics

[0077]

[0078] 3. Combined with stratigraphic correlation and sedimentary type, the reservoir characteristics are studied. It is difficult to distinguish thin sand-shale interbedding using conventional seismic data. The frequency division technology is used to finely describe the reservoir.

[0079] In theory, to distinguish 4-5m sand body, 90-100Hz seismic data is needed. Although the main frequency of the seismic data in the example area is low, the full frequency band seismic data blurs the geological body boundary. However, in view of the specific response characteristics of various geological bodies, there is still high frequency information reflecting thin sand body in the seismic data. Through systematic analysis of the geological conditions and seismic data in the eastern section of the south slope of Dongying, and a series of effect comparison work, it is determined to use the frequency division interpretation technology of seismic data to predict the distribution of sand body in this area.

[0080] Frequency division technology is a frequency-based reservoir interpretation technology. It mainly selects appropriate time window in seismic body, converts information in time domain to frequency domain by using time-frequency analysis method, decomposes into multiple frequency domain data bodies according to certain frequency band, observes the response characteristics of the target sand body under different frequencies, and combines and superimposes the dominant frequency reflecting the target sand body to realize fine description of the whole target sand body. Figure 4

[0081] In the frequency division processing and interpretation process of 702 well area, the seismic data body containing the second member of Shahejie Formation is first extracted from the seismic data body, and then each seismic data body is frequency divided in the frequency band width of 10-100Hz with every 2Hz as a unit. Finally, 45 seismic single frequency data bodies are obtained.

[0082] The 3 2 ​For example, the 70HZ frequency division attribute map can analyze the thick part of the reservoir, but the thin part is not obvious. The 80HZ frequency division attribute map can further reflect the 5-6m thick sand body, but the thinner part still cannot be clearly reflected. The 90HZ frequency division attribute map can analyze the thinner part of the reservoir, but it affects the reflection of other parts. Because the low-frequency data cannot identify the thin reservoir, and the high-frequency data will affect other reflections, almost all single-frequency data in the frequency band are analyzed in actual work. Figure 5 After the combination and stacking of multiple frequencies, the sand body frequency division attribute map of the comprehensive frequency is finally obtained, and the sand body boundary is clearly reflected on the plane. Figure 6

[0083] 4. According to the matching relationship of each accumulation element, the accumulation rule is summarized, the accumulation mode is established, and the favorable area prediction is realized.

[0084] For the example area of Sha II reservoir, the Sha II reservoir is a stratigraphic unconformity barrier reservoir and a lithologic updip pinch-out reservoir controlled by stratigraphic and lithologic factors. As can be seen from our mode diagram, the Sha II reservoir has the characteristics of multiple sand bodies distributed horizontally and connected vertically. Figure 7 The Sha II reservoir accumulation mode can be summarized as: vertical multiple stages, horizontal multiple, and denudation control. Based on this evaluation process, in recent years, 4 exploration wells, 15 rolling wells, and 76 capacity wells have been deployed in this area, with a capacity of 9.47 million tons, a capacity of 1.72 million tons under construction, a reported control reserve of 736.24 million tons in 2019, an upgraded proven reserve of 480.58 million tons in 2020, and a pending upgrade of 400 million tons, a thousand-ton reserve, and a ten-thousand-ton capacity position.

[0085] Finally, it should be noted that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0086] In addition to the technical features described in the specification, they are known to those skilled in the art.​

Claims

1. A method for exploring a shallow stratigraphic-lithologic reservoir in a gentle slope zone of a rifted basin, characterized in that, The exploration method of the shallow strata-lithology reservoir in the gentle slope zone of the rift basin comprises: Step 1, the strata are finely compared, divided and well facies analyzed by comprehensively utilizing geological and logging data; Step 2, the strata over denudation points are precisely depicted by applying the seismic reflection angle extrapolation and instantaneous phase technology, and the structural horizon is finely tracked and explained; Step 3, the reservoir is finely described by applying the frequency division technology; Step 4, the matching relationship of each reservoir forming element is considered to summarize the reservoir forming rule, establish the reservoir forming mode and realize the prediction of the favorable area; In step 2, the step of precisely depicting the over denudation point by the seismic reflection angle extrapolation comprises: Step 2a, the structural interpretation and mapping are performed; Step 2b, a plurality of geological models are established; Step 2c, the forward modeling is performed on the geological models to obtain the forward seismic profile corresponding to the geological models; Step 2d, the stratum angle extrapolation stratum denudation pinch-out line extrapolation template is established; Step 2e, the template of step 2d is applied to correct the structural map of the target layer in step 2a to obtain a new corrected geological structural map; In step 2a, the time-depth relationship is established by applying the artificial seismic synthetic record or the VSP data in the region, the strata comparison result in step 1 is calibrated to the seismic profile corresponding to the position of the well, the target layer and the unconformity are tracked and explained according to the calibration result, and the target layer and the unconformity explanation result are converted into the depth domain geological structural map by applying the time-depth relationship; In step 2b, the strata development situation, the sandstone and mudstone deposition characteristics and the sedimentary type in the region are clarified in step 1, and the different geological model combinations of different stratum dip angles and unconformity dip angles are established according to the explanation result of the target layer and the unconformity in step 2a; In step 2c, the wavelet is extracted in the time window corresponding to the target layer in the seismic data, the reflection coefficients of the stratum interfaces of the geological model established in step 2b are convoluted, the forward modeling is performed to obtain the forward seismic profile corresponding to each geological model; In step 2d, the seismic profile obtained by the forward modeling of each geological model is compared with the geological model to obtain the corresponding relationship between the stratum angle and the stratum denudation pinch-out point extrapolation distance corresponding to different stratum dip angles and unconformity dip angle combinations, and the stratum angle extrapolation stratum denudation pinch-out line extrapolation template of different stratum angles is obtained by fitting calculation; In step 2e, a plurality of control points are selected on the pinchout line of the target layer in step 2a, the inclination of the target layer and the unconformity corresponding to the control points are read, so as to obtain the stratum angle corresponding to the control points, the extrapolation distance of the control points is obtained according to the extrapolation template of the pinchout line in step 2d, and the correction pinchout point or the overlap point corresponding to the control points is determined, the correction pinchout points or the overlap points are connected in sequence to obtain the corrected pinchout line, the depth of each point on the line connecting the control points and the corresponding pinchout points or overlap points is calculated according to the depth of the control points and the stratum inclination, and the isobath points on the line connecting the control points and the corresponding pinchout points or overlap points are connected in sequence to obtain the corresponding isobath, and finally a new corrected geological structure map is obtained; the line connecting the control points and the corresponding pinchout points, the two limbs of the stratum inclination and the unconformity inclination are in the same vertical plane; In step 4, the accumulation rule summary includes oil and gas source analysis, reservoir and cap rock combination analysis, carrier system analysis and reservoir type analysis; the oil and gas source analysis includes oil source comparison and determination of oil and gas source by using geochemical analysis test data; the reservoir and cap rock combination analysis includes matching relationship analysis of reservoir and cap rock, reservoir research including physical property, pore throat structure and favorable reservoir distribution area prediction; cap rock research includes the nature of cap rock and its distribution on the plane; carrier system analysis includes fault, sand body and unconformity surface oil and gas transport research; due to the control of multiple factors such as sedimentary facies, stratum and structure, on the basis of main control factor analysis, the reservoir type is analyzed.

2. The method for exploring the shallow stratigraphic-lithologic reservoirs in the gentle slope zone of the rift basin according to claim 1, characterized in that, In step 1, through fine comparison of geological and logging data of the drilled well, stratum division and logging facies analysis, the stratum development situation, sand and shale sedimentary characteristics and sedimentary types of different regions are clarified.

3. The method for exploring the shallow stratigraphic-lithologic reservoirs in the gentle slope zone of rifted basins according to claim 1, characterized in that, In step 2, the steps of accurately depicting the stratum over-eroded point by using the instantaneous phase technology include:

1. inputting three-dimensional seismic data; 2. converting the conventional seismic data body into an instantaneous phase body; 3. performing structure interpretation in the instantaneous phase body according to Inline and Crossline directions, and compared with the conventional seismic profile, the denudation phenomenon is more clear.

4. The method for exploration of shallow stratigraphic-lithologic reservoirs in the gentle slope zone of rift basins according to claim 1, characterized in that, Step 3 includes: (a) selecting a suitable time window in the seismic data body, and intercepting the seismic data body containing the target layer in a certain time range, and converting the information in the time domain to the frequency domain by using the time-frequency analysis method; (b) decomposing the intercepted seismic data body into a plurality of frequency domain data bodies according to a certain frequency band; (c) by adjusting the time window length, observing the response characteristics of the target sand body under different frequencies, selecting the data body of the dominant frequency reflecting the obvious response characteristics of the target sand body, and merging and stacking the data body for sand body description, and finally obtaining the comprehensive frequency map of the region; (d) according to the target layer calibrated in step (a) and the data body obtained in step (c), the sand body is interpreted and tracked, and the phase axis change point is the sand body description boundary.

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