Delta-beach bar composite sand body prediction method

Abstract

The invention discloses a delta-beach bar composite sand body prediction method, which comprises the following steps of S1, acquiring geological background data of a target work area, and dividing delta and beach bar deposition to obtain a beach bar deposition thickness; s2, carrying out source and sink system analysis, establishing a sediment transport channel path, and obtaining a sand body transport path plane distribution diagram; s3, the ancient landform, ancient wind field features and ancient wave field features of the target work area in the deposition period are restored, the ancient landform height and the distance to the source area of the underwater ancient protrusion are obtained according to the ancient landform, and the features include the ancient wind direction, the ancient wind path, the ancient water depth and the ancient wave height; s4, determining a favorable development zone, a favorable development layer section and a favorable development target zone of the delta-beach bar composite sand body; and S5, obtaining distribution characteristics of the delta-beach bar composite sand body of the target work area according to the favorable development zone, the favorable development layer section and the favorable development target area. According to the method, the delta-beach bar composite sand body can be accurately predicted, and technical support is provided for oil exploration and development.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil exploration and development, and particularly relates to a delta-beach bar composite sand body prediction method. BACKGROUND

[0002] With the continuous deepening of global oil and gas exploration, deep-ultra deep oil and gas reservoirs have become the replacement field of energy exploration. Traditional exploration practice shows that the delta-beach bar composite sedimentary system often develops high-quality reservoirs due to its unique sedimentary configuration and physical property characteristics. In particular, the beach bar complex formed by wave modification exhibits significant advantages such as optimal pore structure and large reservoir space, and becomes an important target area for deep exploration breakthroughs.

[0003] Existing research shows that the formation of beach bar deposition is controlled by a multi-factor synergistic mechanism. The classic deposition model based on wave breaking driving dynamics has revealed the coupling control law of key parameters such as source supply strength, paleogeomorphology, and paleo-wind energy. However, in the deep-ultra deep exploration scenario, the geological constraint conditions present significant particularities: 1) The target layer of offshore is generally buried deeper than 5000 meters. Due to the limitation of seismic data quality, conventional seismic attributes and wave impedance inversion cannot effectively identify the spatial distribution characteristics of thin interbedded sand bodies; 2) The sparseness of drilling data in the exploration area leads to multiple solutions in sedimentary facies belt calibration, and a reliable sedimentary model cannot be established; 3) The quantitative response relationship between paleoenvironmental parameters (such as paleogeomorphology, paleo-provenance strength, and paleo-wave field) and reservoir development has not been established, and existing prediction methods mostly rely on single-factor analysis, which is insufficient in prediction accuracy. SUMMARY

[0004] In view of the above problems, the present application aims to provide a delta-beach bar composite sand body prediction method.

[0005] The technical solution of the present application is as follows:

[0006] A delta-beach bar composite sand body prediction method, comprising the following steps:

[0007] S1: Obtain the geological background data of the target work area, and divide the delta and beach bar deposition according to the geological background data to obtain the thickness of the beach bar deposition;

[0008] S2: Carry out source-sink system analysis, establish a sediment transport channel path, and obtain a sand body migration path planar distribution map;

[0009] S3: Restore the paleogeomorphology, paleo-wind field characteristics, and paleo-wave field characteristics of the target work area during the deposition period according to the geological background data, and obtain the paleogeomorphology height and distance from the source area of the underwater paleo-protuberance according to the paleogeomorphology. The paleo-wind field characteristics include paleo-wind direction and paleo-wind course, and the paleo-wave field characteristics include paleo-water depth and paleo-wave height;

[0010] S4: determining a favorable development zone of the delta-beach bar composite sand body according to the paleowind direction and the distance from the source area, determining a favorable development layer section of the delta-beach bar composite sand body according to the paleowind direction and the paleo-landform height, and determining a favorable development target area of the delta-beach bar composite sand body according to the paleowater depth and the paleowave height;

[0011] S5: obtaining the distribution characteristics of the target delta-beach bar composite sand body according to the favorable development zone, the favorable development layer section and the favorable development target area.

[0012] Preferably, in step S1, the geological background information includes seismic data, logging data, core data and particle size analysis data.

[0013] Preferably, in step S1, the beach bar deposition thickness is calculated by the following formula:

[0014]

[0015] In the formula, t and t b are the beach bar deposition thickness and the beach bar sand body thickness of the drilled well, respectively; and are the original porosity and the present porosity, respectively; c is the lithology-related compaction coefficient; and d is the burial depth.

[0016] Preferably, step S2 specifically includes the following sub-steps:

[0017] S21: performing seismic horizon interpretation of the target work area according to the sequence stratigraphy related theory selected according to the geological background of the target work area;

[0018] S22: identifying the source channel type and obtaining the source channel system distribution feature map according to the seismic profile feature analysis;

[0019] S23: performing classification analysis on the heavy mineral combination of the core of the target work area to obtain the heavy mineral combination plane classification feature;

[0020] S24: combining the basement Tg structure map, the source channel system analysis result and the heavy mineral plane combination feature to establish the path of sand body migration and transportation from the source area to the target area;

[0021] S25: calculating the paleo-source intensity factor by statistically analyzing the catchment area, the catchment height difference and the valley cross-sectional area, so as to quantitatively judge the paleo-source intensity.

[0022] Preferably, in step S25, the paleo-source intensity factor is calculated by the following formula:

[0023] Q = A 0.5 *R*S (3)

[0024] In the formula: Q is the catchment area; A is the catchment area; R is the topographic relief obtained by catchment elevation difference; S is the valley cross-sectional area;

[0025] When the paleo-provenance intensity factor is less than or equal to 510 6 m 3 , it is weak provenance supply intensity, when the paleo-provenance intensity factor is greater than 510 6 m 3 and less than 1010 6 m 3 , it is moderate provenance supply intensity, when the paleo-provenance intensity factor is greater than or equal to 1010 6 m 3 , it is strong provenance supply intensity.

[0026] As preferred, in step S3, the paleo-wind range is obtained by the following sub-steps: making radial rays to the paleo-shoreline within the range of ±45° at intervals of 6° against the paleo-wind direction, drawing the projection of the rays on the paleo-wind direction, and statistically obtaining the average value of all the projections, which is the paleo-wind range.

[0027] As preferred, in step S3, the paleo-water depth is obtained by the following formula:

[0028] h b = d b + t (4)

[0029]

[0030] In the formula: h b is the paleo-water depth; d b is the breaking wave depth; t is the beach bar deposit thickness; and a is the geomorphic slope.

[0031] The paleo-wave height is obtained by the following formula:

[0032]

[0033] In the formula: H b is the paleo-wave height; L0 is the effective wavelength in deep water; and B is an empirical constant.

[0034] As preferred, the effective wavelength in deep water is obtained by the following formula:

[0035]

[0036] In the formula: g is the acceleration of gravity; and T is the wave period.

[0037] As preferred, in step S4, the favorable development zone is determined by the following sub-steps:

[0038] According to the ancient wind direction, the research area is divided into windward area, leeward area and side wind area, according to the distance from the source area, the near source area, the middle source area and the far source area are divided, and the near source area and the windward area are selected as the favorable development zone of the delta-beach dam composite sand body;

[0039] The favorable development layer section is determined through the following sub-steps:

[0040] According to the ancient landform height, the water convex, the underwater ancient convex and the depression are divided, and the layer section with the ancient wind course greater than the ancient wind course threshold value and the underwater ancient convex or the depression is selected as the favorable development layer section of the delta-beach dam composite sand body;

[0041] The favorable development target area is determined through the following sub-steps:

[0042] According to the ancient water depth, the deep water zone and the shallow water zone are divided, according to the ancient wave height, the deep lake zone, the rising wave zone, the broken wave zone and the broken wave zone are divided, and the shallow water zone and the broken wave zone are selected as the favorable development target area of the delta-beach dam composite sand body.

[0043] Preferably, the distance from the source area of the near source area is less than 20 km, the distance from the source area of the middle source area is less than 50 km and greater than or equal to 20 km, and the distance from the source area of the far source area is greater than or equal to 50 km;

[0044] The ancient landform height greater than 0 km is divided into water convex, the ancient landform height greater than-10 km and less than or equal to 0 km is divided into underwater ancient convex, and the ancient landform height less than or equal to-10 km is divided into depression; the ancient wind course threshold value is 8 km;

[0045] The ancient water depth division threshold value of the deep water zone and the shallow water zone is 10 m, the ancient wave height less than or equal to 1 m is the deep lake zone, the ancient wave height less than or equal to 2 m and greater than 1 m is the rising wave zone, the ancient wave height less than or equal to 3 m and greater than 2 m is the broken wave zone, and the ancient wave height less than or equal to 4 m and greater than 3 m is the broken wave zone.

[0046] The present application has the advantages that:

[0047] The present application integrates various geological information of the sediment prediction technology, establishes a sediment prediction model of the cooperative action mechanism of various ancient environment parameters, breaks through the technical barrier of the prediction of the delta-beach dam composite sediment system in deep exploration, and has great value for improving the drilling rate of high-quality reservoirs and reducing the exploration and development risk. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 Schematic diagram of the process of the delta-beach-bar composite sand body prediction method of the present invention;

[0050] Figure 2 Schematic diagram of characteristic sedimentary structures corresponding to delta and beach bar in a specific embodiment;

[0051] Figure 3 This is a diagram of the source-sink paleowater system and heavy mineral analysis in a specific embodiment;

[0052] Figure 4 A map of the ancient landforms of a specific embodiment;

[0053] Figure 5 This is an FMI paleowind direction restoration map in a specific embodiment;

[0054] Figure 6 A diagram of a measurement of ancient wind distance in a specific embodiment;

[0055] Figure 7 This is a paleo-water depth map in a specific embodiment;

[0056] Figure 8 A paleowave height diagram in a specific embodiment;

[0057] Figure 9 This is a delta-beach-bar composite sedimentary facies diagram in a specific embodiment. DETAILED DESCRIPTION

[0058] The present invention is further described below with reference to the accompanying drawings and examples. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those commonly understood by those of ordinary skill in the art to which this application belongs. The use of similar words such as "include" or "comprising" in the present invention means that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0059] like Figure 1 As shown, the present invention provides a method for predicting delta-beach-bar composite sand bodies, comprising the following steps:

[0060] S1: Obtain geological background data of a target work area, and divide the delta and beach bar deposition according to the geological background data to obtain a beach bar deposition thickness.

[0061] In a specific embodiment, the geological background data includes seismic data, well logging data, core data, and grain size analysis data.

[0062] In a specific embodiment, the beach bar deposition thickness is calculated by the following formula:

[0063]

[0064] In the formula, t and t b are the beach bar deposition thickness and the beach bar sand body thickness of a drilled well, respectively; and are the original porosity and the present porosity, respectively; c is a lithology-related compaction coefficient; and d is the burial depth.

[0065] S2: Perform source-sink system analysis to establish a sediment transport channel path to obtain a sand body migration path planar distribution map.

[0066] In a specific embodiment, step S2 specifically includes the following sub-steps:

[0067] S21: Select a sequence stratigraphy related theory according to the geological background of the target work area to perform seismic horizon interpretation of the target work area;

[0068] S22: Identify a source channel type and obtain a source channel system distribution feature map according to seismic profile feature analysis;

[0069] S23: Perform classification analysis on a core heavy mineral combination of the target work area to obtain a heavy mineral combination planar classification feature;

[0070] S24: Establish a sand body migration and transport path from a source area to a target area in combination with a basement Tg structure map, source channel system analysis results, and heavy mineral planar combination features;

[0071] S25: Calculate a paleo-source intensity factor by statistically analyzing a catchment area, a catchment elevation difference, and a valley cross-sectional area to quantitatively determine a paleo-source intensity.

[0072] In a specific embodiment, in step S25, the paleo-source intensity factor is calculated by the following formula:

[0073] Q = A 0.5 *R*S (3)

[0074] In the formula, Q is the catchment area; A is the catchment area; R is a topographic relief obtained by a catchment elevation difference; and S is a valley cross-sectional area.

[0075] When the paleo-provenance intensity factor is less than or equal to 510 6 m 3 , it is weak provenance supply intensity, when the paleo-provenance intensity factor is greater than 510 6 m 3 and less than 1010 6 m 3 , it is medium provenance supply intensity, and when the paleo-provenance intensity factor is greater than or equal to 1010 6 m 3 , it is strong provenance supply intensity.

[0076] In the above embodiment, the sand body migration path plane distribution map can highlight the direction of the paleo-provenance, and only when the provenance direction and the underwater low protrusion are matched, can the wave transformation be provided with a material basis.

[0077] S3: according to the geological background information, the paleo-geomorphology, the paleo-wind field characteristics and the paleo-wave field characteristics of the target work area in the sedimentary period are restored, and the paleo-geomorphology height and the distance from the source area of the underwater paleo-protrusion are obtained according to the paleo-geomorphology, the paleo-wind direction and the paleo-wind range are included in the paleo-wind field characteristics, and the paleo-water depth and the paleo-wave height are included in the paleo-wave field characteristics.

[0078] In a specific embodiment, the paleo-geomorphology is obtained by the following sub-steps: according to the seismic horizon interpretation result of the target work area, the stratum top and bottom time domain stratum interface of the target work area and the reflection of the entire basin filling and complementing of the seismic interface formed by the maximum flooding in the overlying stable sedimentary period are obtained, and time-depth conversion is performed; the target work area in the sedimentary period is restored by using the impression method to obtain a paleo-geomorphology map. The paleo-geomorphology height, geomorphology slope and distance from the source area of the underwater paleo-protrusion can be obtained by the paleo-geomorphology map.

[0079] In a specific embodiment, the paleo-wind field characteristics are obtained by the following sub-steps: the paleo-wind direction is restored by using the FMI imaging logging data of the cross-bedding of the drilled well, so as to restore the paleo-wind direction; on the basis of obtaining the paleo-wind direction, the paleo-wind range is restored, the projection of the rays on the paleo-wind direction is drawn within the range of ±45° at intervals of 6° along the paleo-wind direction to the paleo-shoreline, and the average value of all projections is obtained by statistical calculation, which is the paleo-wind range.

[0080] In a specific embodiment, the paleo-water depth is obtained by the following formula:

[0081] h b = d b + t (4)

[0082]

[0083] In the formula, h b is the paleo-water depth, d b is the distance from the source area, and t is the thickness of the sedimentary layer.Hb is the wave breaking depth; t is the thickness of beach bar deposit; and a is the geomorphic slope.

[0084] The ancient wave height is obtained by the following formula:

[0085]

[0086] In the formula, H b is the ancient wave height; L0 is the effective wavelength in deep water; and B is an empirical constant, which is 0.15.

[0087] In one specific embodiment, the effective wavelength in deep water is obtained by the following formula:

[0088]

[0089] In the formula, g is the acceleration of gravity; and T is the wave period.

[0090] S4: determining a favorable development zone of the delta-beach bar composite sand body according to the ancient wind direction and the distance from the source area, determining a favorable development layer section of the delta-beach bar composite sand body according to the ancient wind course and the ancient geomorphic height, and determining a favorable development target area of the delta-beach bar composite sand body according to the ancient water depth and the ancient wave height.

[0091] In one specific embodiment, the favorable development zone is determined by the following sub-steps:

[0092] The research area is divided into a windward area, a crosswind area and a leeward area according to the ancient wind direction, and is divided into a near-source area, a middle-source area and a far-source area according to the distance from the source area, and the near-source area and the windward area are selected as the favorable development zone of the delta-beach bar composite sand body.

[0093] The favorable development layer section is determined by the following sub-steps:

[0094] The ancient geomorphic height is used to divide an above-water protrusion, an underwater ancient protrusion and a depression, and a layer section with an ancient wind course greater than an ancient wind course threshold value and the underwater ancient protrusion or the depression is selected as the favorable development layer section of the delta-beach bar composite sand body.

[0095] The favorable development target area is determined by the following sub-steps:

[0096] The ancient water depth is used to divide a deep water zone and a shallow water zone, and the ancient wave height is used to divide a deep lake zone, a rising wave zone, a broken wave zone and a wave breaking zone, and the shallow water zone and the wave breaking zone are selected as the favorable development target area of the delta-beach bar composite sand body.

[0097] In a specific embodiment, the distance between the near-source zone and the source zone is less than 20 km, the distance between the middle-source zone and the source zone is less than 50 km and greater than or equal to 20 km, and the distance between the far-source zone and the source zone is greater than or equal to 50 km; the paleo-geomorphology height greater than 0 km is divided into an above-water uplift, the paleo-geomorphology height greater than -10 km and less than or equal to 0 km is divided into an underwater paleo-uplift, and the paleo-geomorphology height less than or equal to -10 km is divided into a depression; the paleo-wind distance threshold is 8 km; the paleo-water depth division threshold for the deep water zone and the shallow water zone is 10 m, the paleo-wave height is less than or equal to 1 m for the deep lake zone, the paleo-wave height is less than or equal to 2 m and greater than 1 m for the rising wave zone, the paleo-wave height is less than or equal to 3 m and greater than 2 m for the breaking wave zone, and the paleo-wave height is less than or equal to 4 m and greater than 3 m for the breaking wave zone.

[0098] S5: Obtain the distribution characteristics of the delta-beach-bar composite sand body in the target work area based on the favorable development zones, favorable development intervals and favorable development target areas.

[0099] In a specific embodiment, taking a target work area as an example, the delta-beach-bar composite sand body prediction method of the present invention is used to predict the delta-beach-bar composite sand body, which specifically includes the following sub-steps:

[0100] (1) Obtain geological background data of the target work area, including seismic data, well logging data, core data, and grain size analysis and other analytical data, and classify the delta and beach-bar sedimentary systems;

[0101] The characteristic sedimentary structures of the delta and beach bar in the target work area are as follows: Figure 2 As shown, from Figure 2 The delta developed in the target area is relatively close to the source area and has a coarse grain size. Lithologically, it consists of conglomerate, gravelly sandstone, coarse sandstone, and medium sandstone. Typical structural features include massive bedding, trough / wedge / tabular / high-angle cross-bedding, parallel bedding, and erosion-scour surfaces. The sandstones of braided river deltas are generally poorly sorted and rounded, with a high concentration of interstitial material. The grain size probability density cumulative plot of braided river delta rock samples shows a four-segment distribution, with a low slope for the jump component, also reflecting poor overall sorting. Physically, braided river delta sandstones are highly heterogeneous and have relatively poor porosity and permeability. Furthermore, their probability density distribution curves exhibit bimodal or multimodal characteristics, reflecting a high proportion of rolling and jump components. Well logging indicates that the GR curves of braided river deltas are generally toothed box-shaped.

[0102] Well logging reveals a continuous series of positive cycles superimposed on negative cycles. The lithologic composition of the beach-bar facies is primarily fine sandstone and siltstone. Sedimentary structure is characterized by massive bedding and wave-shaped / wavy / depression-shaped cross-bedding. Pore structure and interstitial material content indicate moderate sorting and rounding, clean pores, and low interstitial material content. Physical properties indicate high porosity and permeability overall. The cumulative probability density distribution curve of the beach-bar core shows a distinct two-stage pattern, reflecting a complex environment characterized by multiple hydrodynamic forces of varying energy. In lakes, this often reflects multiple fluid processes, including wave surge, backflow, and longshore currents. The probability density distribution curve exhibits a distinct single peak, with the primary jump component exceeding 90%, indicating a strong influence of wave remodeling. Well logging results also provide a good indicator of grain size variation. Based on logging characteristics, the GR of the beach-bar is primarily characterized by negative cycles, funnel-shaped, and finger-shaped formations.

[0103] Based on the lithofacies sequence of some cored wells and the logging facies of all target layers in the area, a total of 23 wave-breaking sandbars were identified on the wells. The results are shown in Table 1:

[0104]

[0105]

[0106] As can be seen from Table 1, the thickness of the drilled beach bar sand body t b The distribution range is 0.87~4.16m. The thickness of the beach bar sand body is corrected by decompaction using formula (1) to obtain the beach bar sediment thickness t. In this embodiment, the lithologic composition of the identified wave-breaking dam is all sandstone, and its original porosity is and compaction coefficient c are 50.92% and 0.0003382, respectively, and the thickness of the beach-bar deposits is between 1.43 and 6.85 m.

[0107] (2) Conduct source-sink system analysis, establish sediment transport pathways, and obtain a planar distribution map of sand body migration pathways;

[0108] First, based on the geological background of the target work area, relevant theories of sequence stratigraphy are selected to interpret the seismic horizons of the target work area. Specifically: based on the sequence stratigraphic division of the work area, seismic horizon interpretation is carried out to obtain the sequence stratigraphic framework of the target work area.

[0109] Secondly, based on the analysis of seismic profile characteristics, the source channel type is identified and the distribution characteristic map of the source channel system is obtained; specifically: by analyzing the stratigraphic interface morphology of multiple continuous sections in the tectonic transition zone, the source channel type is identified and the distribution characteristic map of the source channel system is obtained. Figure 3The shown material source channel type map. Through the fine seismic profile dissection, 8 under cutting valley channels are identified, narrow at the bottom and wide at the top. Among them, the small under cutting valley system developed in the middle of the study area is mainly V-shaped, with a cutting valley width of 0.4-1 km, and a small development scale. The W-shaped under cutting valley system developed in the north of the slope belt is wider, with a width of 3-4 km, a larger development scale, and is also steeper.

[0110] Again, the heavy mineral assemblage of the target work area is classified and analyzed, and the heavy mineral assemblage plane classification characteristics are obtained; Specifically: Heavy minerals are affected by weathering and show different degrees of stability, which can be divided into stable heavy minerals and unstable heavy minerals. The farther away from the source area, the higher the content of stable heavy minerals in sediments, and the unstable heavy minerals gradually decrease. The ZTR index refers to the percentage of transparent mineral components such as tourmaline, zircon, and rutile in heavy minerals. The ZTR index increases with the distance from the parent rock area, and in the near-source area, the ZTR index often presents a relatively low value.

[0111] From the heavy mineral assemblage and ZTR index of the study area, it can be seen that there are three heavy mineral assemblages in the Wenchang Formation during deposition, corresponding to different sedimentary areas. Heavy mineral assemblage one, ZTR index (6.61-10.07), corresponding to the northern area of the target work area, with the north slope large under cutting valley source channel transporting sedimentation. Heavy mineral assemblage two, low ZTR index, corresponding to the southern uplift position of the target work area, transported by the southern fault channel source channel; Heavy mineral assemblage three, high ZTR index (11.6-25.6), corresponding to the central depression well area, transported by the central small under cutting valley source channel.

[0112] Then, combined with the basement Tg structure map, the source channel system analysis results and the heavy mineral plane assemblage characteristics, the path of sand body migration and transportation from the source area to the target area is established.

[0113] Finally, the catchment area, catchment elevation difference, and valley cross-sectional area are counted, and the paleo-source intensity factor is calculated to quantitatively judge the paleo-source intensity.

[0114] (3) Restore the paleogeomorphology of the target work area during the sedimentary period, and count the paleogeomorphology height of the underwater paleo-uplift and the distance from the source area;

[0115] Firstly, according to the seismic horizon interpretation result of the target work area, the stratum top and bottom time domain stratum interface of the target work area is obtained, and the reflection of the entire basin filling and patching is obtained, and time-depth conversion is carried out; according to the seismic horizon interpretation result, the target horizon Wen 6 top and bottom time domain seismic layer (T85 and T85-1) of the target work area is obtained, and the isochronal seismic interface selected in the overlying sedimentary stratum which can reflect the filling and patching characteristics of the target layer is taken as the marker layer interface, and the time domain is converted into depth domain through well-seismic combination time-depth relationship, so as to obtain the depth domain plane diagram of the top and bottom interface of the target layer.

[0116] Then, the target work area sedimentary period paleogeomorphology is recovered by using the impression method, and the paleogeomorphology map is obtained; the residual thickness of Wen 6 upper stratum depth domain is obtained by subtracting the depth domain marker layer interface from the depth domain target stratum bottom surface, and the paleogeomorphology is recovered. Figure 4 The target work area target stratum sedimentary period paleogeomorphology map is shown.

[0117] Finally, the paleogeomorphology height, geomorphology slope and distance from the source area of the underwater paleo-protrusion are counted.

[0118] (4) Recover the characteristics of the paleo-wind field in the sedimentary period, including the paleo-wind direction and the paleo-wind course;

[0119] The FMI imaging logging data of the cross-bedding of the drilled well are used to recover the paleo-current direction, so as to recover the paleo-wind direction; specifically: based on the FMI imaging logging data of the cross-bedding of the drilled well, the paleo-current direction is recovered, and the paleo-current direction can indicate the paleo-wind wave field direction in the sedimentary period. Cross-bedding usually shows a series of wave-like or linear structures intersecting the bedding plane, which reflects the change of the water flow direction in the sedimentary process. It is generally believed that in the sedimentary period, the cross-bedding of sandstone is inclined to the same paleo-current direction, so the inclination of the cross-bedding of sandstone can be used to recover the transport direction of the source. The cross-bedding and mudstone bedding inclination data are extracted from the corrected, filtered and enhanced imaging logging data, and the mudstone bedding is used to correct the inclination of the cross-bedding of sandstone to restore the original sedimentary inclination, and finally a rose diagram is drawn, so that the paleo-current direction can be determined. As shown in Figure 5 In the drilled well data, the drilling of HZ25-7-2 encountered the Wen Chang formation sedimentary microfacies of braided river delta, and the drilling of HZ25-4-1 encountered the Wen Chang formation sedimentary microfacies of island-beach complex. Among them, the paleo-current direction recovered by the imaging logging in HZ25-7-2 well is single NE direction, and NE may represent the direction of the original source advance. By comparison, the paleo-current direction of HZ25-4-1 well is NE and NW, and as mentioned before, NE is the transport direction of the original source, and NW reflects the paleo-wind direction at that time.

[0120] At the same time, through literature research, the influence of the collision process between the Indian plate and the Eurasian plate on the direction of the East Asian summer monsoon is proposed. The summer monsoon in the Pearl River Estuary area during the Upper Oligocene (49-43 Ma) was mainly southeast, and was affected by the uplift of the Qinghai-Tibet Plateau. The influence range of the East Asian monsoon gradually expanded northward after 41 Ma. The wind force during the Lower Oligocene (43-38 Ma) was stronger, which further verified that the paleowind direction in the B block during the Lower Oligocene was mainly northwest.

[0121] On the basis of the determination of the southeast paleowind direction, the paleowind course F is restored. The radial lines are drawn to the paleoshoreline (shoreline) within ±45° at an interval of 6° against the paleowind direction. The projection of the radial lines on the paleowind direction is drawn, and finally the average value of the projections is obtained by statistics. The paleowind course of the B block is about 11 km, as shown in Table 1 and Figure 6 .

[0122] (5) Restoring the characteristics of the paleowave field during the deposition period, including the paleowater depth and the paleowave height;

[0123] In this embodiment, the paleowater depth is obtained by calculation according to formula (4)-(5), and the paleowave height is obtained by calculation according to formula (6)-(8). The results are shown in Table 1 and Figure 7 , Figure 8 .

[0124] (6) According to the paleowind direction and the distance between the paleohigh and the source area, the favorable development zone of the delta-beach bar complex is determined;

[0125] It is determined that the paleowind direction during the deposition period of the Wenchang Formation in the target work area is mainly southeast. Therefore, the northwest region is divided into a windward area, the southwest region is a side wind area, and the southeast region is a leeward area. The distance between the paleohigh and the source area Ds is measured, which is divided into near source <20 km, medium source 20 km

[0126] (7) According to the paleowind course and the paleogeomorphological height, the favorable development layer section of the delta-beach bar complex is determined;

[0127] By measuring the palaeo-wind course of each area, the section with the developed palaeo-wind course F>8km is selected as the potential delta-beach bar composite sediment development section. By measuring the palaeo-landform height H of each area, the underwater palaeo-convexity with H>0, -10<H<0, and the depression with H<-10 are obtained. By restoring the palaeo-landform, the palaeo-landform height of each area is quantitatively judged, and the section with the developed underwater low convexity (-10<H<0) is the potential delta-beach bar composite sediment development section. By comprehensively analyzing the palaeo-wind course and the palaeo-landform related parameters, the Wuliu section with the developed underwater low convexity (H=-8) and large wind course (F=11km) is selected as the dominant sediment section of the delta-beach bar composite sand body.

[0128] (8) According to the palaeo-water depth and the palaeo-wave height, the target area with the developed delta-beach bar composite is determined;

[0129] According to the restored palaeo-water depth, the water depth zone is divided, and the deep lake zone with hw>10m and the shallow lake zone with hw<10m are obtained. According to the restored palaeo-wave height, the hydrodynamic zone is divided, and the deep lake zone with Hb<1m, the rising wave zone with 1m<Hb<2m, the broken wave zone with 2<Hb<3, and the broken wave zone with 3<Hb<4 are obtained. The shallow lake zone (water depth <10m) and the broken wave zone (wave height >3m) are selected as the favorable target area of the delta-beach bar composite sand body. By comprehensively analyzing the palaeo-water depth and the palaeo-wave height, the two steps of the shallow lake zone and the broken wave zone are selected as the favorable target area of the delta-beach bar composite sand body.

[0130] (9) The distribution characteristics of the target delta-beach bar composite in the target work area are obtained.

[0131] Based on the "six palaeo-three steps" common constraints of steps (6)-(8), the strong material source, the windward area, the large wind course, the low convexity, the shallow lake zone and the broken wave zone are selected as the favorable constraints for the development of the delta-beach bar composite, and the results are shown in Figure 9 .

[0132] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as the above preferred embodiment, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution of the present application, and any simple modification, equivalent change and modification of the above embodiment based on the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for predicting delta-beach-bar composite sand bodies, characterized in that: The following steps are involved: S1: Obtain geological background data of the target work area, and classify delta and beach-bar deposits according to the geological background data to obtain the thickness of beach-bar deposits; S2: Conduct source-sink system analysis, establish sediment transport pathways, and obtain a planar distribution map of sand body migration pathways; S3: Restore the paleo-geomorphology, paleo-wind field characteristics, and paleo-wave field characteristics of the target work area during the sedimentation period based on the geological background data, and obtain the paleo-geomorphology height and distance from the source area of ​​the underwater paleo-uplift based on the paleo-geomorphology. The paleo-wind field characteristics include paleo-wind direction and paleo-wind range, and the paleo-wave field characteristics include paleo-water depth and paleo-wave height. S4: determining a favorable development zone of the delta-beach-bar composite sand body according to the paleowind direction and the distance from the source area, determining a favorable development interval of the delta-beach-bar composite sand body according to the paleowind direction and the paleogeomorphic height, and determining a favorable development target area of ​​the delta-beach-bar composite sand body according to the paleowater depth and the paleowave height; S5: Obtain the distribution characteristics of the delta-beach-bar composite sand body in the target work area based on the favorable development zones, favorable development intervals and favorable development target areas.

2. The method for predicting delta-beach-bar composite sand bodies according to claim 1, characterized in that: In step S1, the geological background data includes seismic data, well logging data, core data and grain size analysis data.

3. The method for predicting delta-beach-bar composite sand bodies according to claim 1, characterized in that: In step S1, the beach bar deposition thickness is calculated by the following formula: Where: t and t b are the thickness of beach-bar sediments and the thickness of drilled beach-bar sand bodies, respectively; φ and φ' are the original porosity and the current porosity, respectively; c is the compaction coefficient related to lithology; d is the burial depth.

4. The method for predicting delta-beach-bar composite sand bodies according to claim 1, characterized in that: Step S2 specifically includes the following sub-steps: S21: Select sequence stratigraphy-related theories based on the geological background of the target work area and interpret the seismic horizons in the target work area; S22: Based on the analysis of seismic profile characteristics, identify the source channel type and obtain the distribution characteristic map of the source channel system; S23: Classify and analyze the heavy mineral assemblage of the cores in the target work area to obtain the plane classification characteristics of the heavy mineral assemblage; S24: Combine the basement Tg structural map, the results of the provenance channel system analysis and the plane combination characteristics of heavy minerals to establish the migration and transportation path of the sand body from the provenance area to the target area; S25: Count the catchment area, water collection height difference, and valley cross-sectional area, calculate the paleosource intensity factor, and thus quantitatively determine the paleosource intensity.

5. The method for predicting delta-beach-bar composite sand bodies according to claim 4, characterized in that: In step S25, the antiquity source intensity factor is calculated using the following formula: Q=A 0.5 *R*S (3) Where: Q is the catchment area; A is the catchment area; R is the topographic relief obtained by the height difference of the catchment; S is the cross-sectional area of ​​the valley; When the antiquity source intensity factor is less than or equal to 510 6 m 3 When the paleo-source intensity factor is greater than 510 6 m 3 and less than 1010 6 m 3 When the intensity factor of the ancient source is greater than or equal to 1010 6 m 3 When is the strong source supply intensity.

6. The method for predicting delta-beach-bar composite sand bodies according to claim 1, characterized in that: In step S3, the paleowind distance is obtained by the following sub-steps: radial lines are drawn to the paleoshore line at intervals of 6° and within the range of ±45° against the paleowind direction, the projections of the rays in the paleowind direction are plotted, and the average value of all projections is obtained by statistics. The average value is the paleowind distance.

7. The method for predicting delta-beach-bar composite sand bodies according to claim 1, characterized in that: In step S3, the paleo-water depth is calculated using the following formula: h b =d b +t (4) Where: h b is the ancient water depth; d b is the wave-breaking water depth; t is the thickness of beach-bar sediments; α is the landform slope; The paleowave height is calculated by the following formula: Where: H b is the paleo-wave height; L0 is the effective wavelength in deep water; B is an empirical constant.

8. The method for predicting delta-beach-bar composite sand bodies according to claim 7, characterized in that: The effective wavelength in deep water is calculated by the following formula: Where: g is the acceleration due to gravity; T is the wave period.

9. The method for predicting delta-beach-bar composite sand bodies according to any one of claims 1 to 8, characterized in that: In step S4, the favorable growth zone is determined by the following sub-steps: The study area is divided into windward area, crosswind area and leeward area according to the paleowind direction, and divided into near-source area, middle-source area and far-source area according to the distance from the source area. The near-source area and windward area are selected as the favorable development zones of delta-beach-bar composite sand bodies. The favorable development interval is determined by the following sub-steps: According to the height of the paleo-geomorphology, the above-water bulges, underwater paleo-bulges and depressions are divided, and the intervals with paleo-wind distance greater than the paleo-wind distance threshold and underwater paleo-bulges or depressions are selected as the favorable intervals for the development of delta-beach-bar composite sand bodies; The favorable development target area is determined by the following sub-steps: The deep water zone and the shallow water zone are divided according to the ancient water depth, and the deep lake zone, the rising wave zone, the breaking wave zone and the wave-breaking zone are divided according to the ancient wave height. The shallow water zone and the wave-breaking zone are selected as favorable development target areas for the delta-beach-bar composite sand body.

10. The method for predicting delta-beach-bar composite sand bodies according to claim 9, characterized in that: The distance between the near source region and the source region is less than 20 km, the distance between the middle source region and the source region is less than 50 km and greater than or equal to 20 km, and the distance between the far source region and the source region is greater than or equal to 50 km; Paleo-relief heights greater than 0 km are classified as above-water uplifts, paleo-relief heights greater than -10 km and less than or equal to 0 km are classified as underwater uplifts, and paleo-relief heights less than or equal to -10 km are classified as depressions. The paleo-wind distance threshold is 8 km. The paleo-water depth threshold for dividing the deep water zone and the shallow water zone is 10m. The paleo-wave height is less than or equal to 1m for the deep lake zone, the paleo-wave height is less than or equal to 2m and greater than 1m for the rising wave zone, the paleo-wave height is less than or equal to 3m and greater than 2m for the breaking wave zone, and the paleo-wave height is less than or equal to 4m and greater than 3m for the breaking wave zone.

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