Scale prediction method and system for gravel rock mass in abrupt slope zone

Abstract

The invention provides an abrupt slope glutenite mass scale prediction method and system, and the method comprises the steps: S1, building an isochronous stratigraphic framework based on well drilling and seismic data, and recognizing a basin edge fault and a base; s2, inshore subsea fan gravel rock mass depicting based on a sedimentary facies belt; s3, constructing a relationship between occurrence parameters of the basin edge fault and the basement and geometric morphology parameters of the glutenite body; and S4, constructing a near-shore underwater fan glutenite mass scale prediction mathematical model based on the basin edge fault and the basement occurrence. And establishing a corresponding mathematical model to realize fine prediction of the near-shore underwater fan gravel rock mass scale.

Description

Technical Field

[0001] The present invention relates to the field of nearshore submarine fan sedimentation and reservoirs, and particularly to a method and system for predicting the scale of gravel bodies in steep slope zones. Background Art

[0002] The nearshore submarine fan is a widely developed terrigenous clastic sedimentary system, often showing a skirt-like distribution in the steep slope zone of the piedmont fault. The gravel bodies formed by its sedimentation can serve as important oil and gas reservoirs, which is of great significance for the evaluation of oil and gas resources. However, the gravel bodies of the nearshore submarine fan often have the characteristics of longitudinal superposition, lateral connection, and diverse shapes, and the prediction of their development scale remains a difficult point.

[0003] For the prediction of the scale of sandstone bodies in the nearshore submarine fan, the commonly used methods at present include the prediction method based on "gully-fan correspondence" (i.e., "large gully corresponds to large fan, small gully corresponds to small fan"), the prediction method using sand-to-shale ratio, and the method for depicting gravel bodies based on seismic slices. Among them, the first two methods are qualitative or semi-quantitative predictions, and the prediction results have low accuracy and can no longer meet the requirements of fine oil and gas exploration and development. The third method has high requirements for the quality of seismic data and cannot be applied in work areas without seismic data coverage. Therefore, there is an urgent need for a quantitative prediction technology to solve the problem of fine prediction of the scale of gravel bodies in the nearshore submarine fan. The distribution of gravel bodies in the nearshore submarine fan is controlled by the basin-margin fault and the basement morphology characteristics. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a method and system for predicting the scale of gravel bodies in steep slope zones that overcome the above problems or at least partially solve the above problems.

[0005] According to one aspect of the present invention, a method for predicting the scale of gravel bodies in steep slope zones is provided. The prediction method includes:

[0006] Step S1: Establish an isochronous stratigraphic framework based on drilling and seismic data, and identify the basin-margin fault and the basement;

[0007] Step S2: Depict the gravel bodies of the nearshore submarine fan based on sedimentary facies belts;

[0008] Step S3: Construct the relationship between the attitude parameters of the basin-margin fault and the basement and the geometric shape parameters of the gravel bodies;

[0009] Step S4: Construct a mathematical model for predicting the scale of the nearshore submarine fan gravel bodies based on the attitude of the basin-margin fault and the basement.

[0010] Optionally, the Step S1: Establish an isochronous stratigraphic framework based on drilling and seismic data, and identify the basin-margin fault and the basement specifically includes:

[0011] Step S1.1: Divide a certain area according to the division criteria, and establish a skeleton profile by combining well logging and mud logging data;

[0012] Step S1.2: Construct a cross-well seismic profile in the 3D seismic data volume. Through well-seismic correlation, establish an isochronous stratigraphic framework based on seismic data. Flatten the top surface with the top boundary of a certain area as the marker bed, and determine the geological reflection characteristics of the interfaces of each sand member. On the seismic profile, identify the basin margin faults and use the interface of a certain area as the sedimentary basement;

[0013] Step S1.3: Based on the division criteria, conduct stratigraphic division and correlation, and identify basin margin faults and basement on the main survey lines and connecting lines in the seismic work area in sequence.

[0014] Optionally, the division of a certain area according to the division criteria specifically includes: dividing it into four sand members, namely the first sand member S1, the second sand member S2, the third sand member S3, and the fourth sand member S4 according to the division criteria.

[0015] Optionally, the establishment of a skeleton profile by combining well logging and mud logging data specifically includes: establishing skeleton profiles along the sediment source direction and perpendicular to the sediment source direction by combining well logging and mud logging data.

[0016] Optionally, Step S2: The characterization of the nearshore subaqueous fan sandy conglomerate bodies based on sedimentary facies belts specifically includes:

[0017] Step 2.1, under the constraint of the isochronous stratigraphic framework, taking the paleo-channel system as a unit, anatomize the sandy conglomerate fans in the work area in the main survey line and connecting survey line directions in sequence;

[0018] Use the well-seismic combination method to finely characterize the distribution of fans in multiple periods;

[0019] Through the identification of seismic profile characteristics, judge the fan facies belts corresponding to multiple seismic facies, characterize the pinch-out positions of seismic facies, and calibrate the pinch-out points of sandy conglomerate fans in multiple periods;

[0020] Step 2.2, according to the nearshore subaqueous fan sandy conglomerate body characterization technology described in Step 2.1, identify seismic facies every 10 traces in the 3D seismic data volume, finely characterize the distribution of sandy conglomerate bodies in the whole area, and draw the plane distribution map of the nearshore subaqueous fan sandy conglomerate bodies of the first sand member S1 in a certain area.

[0021] Optionally, the seismic facies characterization methods for multiple facies belts include: the fan root of the nearshore subaqueous fan, the middle part of the nearshore subaqueous fan, and the fan end of the nearshore subaqueous fan.

[0022] Optionally, the characterization method for the fan root of the nearshore subaqueous fan specifically includes:

[0023] The sorting of the rock in the fan root facies belt is relatively poor. The seismic reflection characteristics are mainly wedge-shaped chaos, wedge-shaped progradation, and wedge-shaped blank reflection. Different stages of the main channels in the fan root are divided by different shale sections in the troughs.

[0024] Optionally, the method for depicting the middle part of the nearshore submarine fan includes:

[0025] The middle part of the fan facies belt mainly develops braided main channels, and the seismic profile shows strong amplitude characteristics. The shale content in the middle part of the fan facies belt is more than that in the fan root and is stable. The shale interlayers in the middle part of the fan are obvious in seismic reflection, showing stable reflections between independent reflection isochrones. The separated lenticular or progradational reflection axes represent different stages of the fan body.

[0026] Optionally, the method for depicting the distal part of the nearshore submarine fan includes: good reflection continuity, weak amplitude of the isochrone, and seismic reflection characteristics of lenticular or small mound-shaped reflections of the isochrone.

[0027] Optionally, the specific steps of step S3: constructing the relationship between the basin margin fault and basement attitude parameters and the geometric morphology parameters of the sandy conglomerate body include:

[0028] Step 3.1, on the basis of the basin margin fault and basement morphology identified in step S1.2, measure the dip angle of the basin margin fault and the slope angle of the basement every 10 seismic data traces;

[0029] Among them, the dip angle of the basin margin fault is the angle between the fault plane and the horizontal plane, the slope angle of the basement is the angle between the basement tangent and the horizontal plane, the depression angle is positive, and the elevation angle is negative; statistically summarize the measured data;

[0030] Step 3.2, on the basis of the morphology of the nearshore submarine fan sandy conglomerate depicted in step S2, measure the length L and width W of the sandy conglomerate body once. Among them, the length of the sandy conglomerate body refers to the maximum extension distance of the sandy conglomerate body in the direction of the sediment source, the maximum length is the longest extension distance, and the width of the fan body refers to the maximum width of the fan body in the direction perpendicular to the sediment source;

[0031] Under the constraint of the facies belt boundary, measure the length and width of the fan body extending to the fan root, middle part, and distal part of the fan respectively, and statistically summarize the measured data.

[0032] Optionally, the specific steps of step S4: constructing a mathematical model for predicting the scale of the nearshore submarine fan sandy conglomerate body based on the basin margin fault and the basement attitude include:

[0033] On the basis of the statistical data in step S3, taking the sine values of the dip angle of the basin margin fault and the slope angle of the basin as independent variables and the length of the nearshore submarine fan sandy conglomerate body as the dependent variable, use SPSS software for binary linear regression to establish a mathematical representation model for the length of the nearshore submarine fan sandy conglomerate body extending to different facies belts in the upper submember S1 of the Shahejie Formation in the Shengtuo-Lijin area.

[0034] Formula 1-3;

[0035] L 1 = 5.278×sinα + 0.286×sinβ - 3.644, Formula 1

[0036] L 2 = 7.831×sinα + 0.596×sinβ - 5.152, Formula 2

[0037] L 3 = 8.680×sinα + 0.490×sinβ - 5.393, Formula 3

[0038] Wherein, α is the dip angle of the basin margin fault, β is the basin slope angle, unit: °; L 1 、L 2 、L 3 are respectively the lengths of the fan extending along the provenance direction to the boundaries of the fan root, fan middle and fan end, unit: km;

[0039] Step 4.2, based on the statistical data in Step 2.2, taking the lengths and widths of the subaqueous fan sandy conglomerate bodies extending to different facies belts as independent and dependent variables respectively, plotting a scatter diagram of the length-width relationship, and performing a unary linear regression to establish a mathematical characterization model of the width of the sandy conglomerate bodies in the S1 sand member of the upper Es4 submember in the Shengtuo-Lijin area, Formulas 4-6;

[0040] W 1 = 0.612×L 1 + 0.449, Formula 4

[0041] W 2 = 0.326×L 2 + 0.770, Formula 5

[0042] W 3 = 0.596×L 3 + 0.530, Formula 6

[0043] Wherein, L 1 、L 2 、L 3 are respectively the lengths of the fan extending along the provenance direction to the boundaries of the fan root, fan middle and fan end, unit: km; W 1 、W 2 、W 3 are respectively the widths of the fan root, fan middle and fan end perpendicular to the provenance direction, unit: km.

[0044] The present invention also provides a prediction system for the scale of the sandy conglomerate bodies in the steep slope zone, applying the above-mentioned prediction method for the scale of the sandy conglomerate bodies in the steep slope zone. The prediction system includes:

[0045] The isochronous stratigraphic framework establishment module is used to establish an isochronous stratigraphic framework based on drilling and seismic data, and identify basin margin faults and the basement;

[0046] The fan gravel rock body characterization module is used to characterize the nearshore underwater fan gravel rock body based on the sedimentary facies belt;

[0047] The parameter relationship construction module is used to construct the relationship between the attitude parameters of the basin margin fault and the basement and the geometric shape parameters of the gravel rock body;

[0048] The mathematical model construction module is used to construct a mathematical model for predicting the scale of the nearshore underwater fan gravel rock body based on the attitudes of the basin margin fault and the basement.

[0049] A method and system for predicting the scale of gravel rock bodies in a steep slope zone provided by the present invention. The prediction method includes: Step S1: Establish an isochronous stratigraphic framework based on drilling and seismic data, and identify basin margin faults and the basement; Step S2: Characterize the nearshore underwater fan gravel rock body based on the sedimentary facies belt; Step S3: Construct the relationship between the attitude parameters of the basin margin fault and the basement and the geometric shape parameters of the gravel rock body; Step S4: Construct a mathematical model for predicting the scale of the nearshore underwater fan gravel rock body based on the attitudes of the basin margin fault and the basement. By establishing a corresponding mathematical model, fine prediction of the scale of the nearshore underwater fan gravel rock body is realized.

[0050] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the description. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are given below. Description of the Drawings

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0052] Figure 1 It is a flowchart of a method for predicting the scale of gravel rock bodies in a steep slope zone provided by an embodiment of the present invention;

[0053] Figure 2 It is a stratigraphic correlation profile based on drilling data provided by an embodiment of the present invention;

[0054] Figure 3 It is a stratigraphic framework and basement morphology profile based on seismic data provided by an embodiment of the present invention;

[0055] Figure 4Cross-sectional view of the nearshore submarine fan sedimentary facies belt provided by the embodiment of the present invention;

[0056] Figure 5 Planar distribution map of the nearshore submarine fan sandy conglomerate body provided by the embodiment of the present invention;

[0057] Figure 6 Schematic diagram of the parameter measurement method provided by the embodiment of the present invention;

[0058] Figure 7 Length-width relationship diagram of the nearshore submarine fan sandy conglomerate body provided by the embodiment of the present invention. Detailed implementation manners

[0059] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0060] The terms "including" and "having" and any variations thereof in the description embodiments, claims and drawings of the present invention are intended to cover non-exclusive inclusion. For example, including a series of steps or units.

[0061] Hereinafter, in combination with the accompanying drawings and embodiments, the technical solutions of the present invention will be described in further detail.

[0062] The present invention aims to solve the deficiencies of the prior art, and proposes a scale prediction technology for sandy conglomerate bodies in the steep slope zone based on basin margin faults and basement attitude. Combining the dip angle of the basin margin fault, the basement slope and the morphological parameters of the sandy conglomerate body, a corresponding mathematical model is established to achieve fine prediction of the scale of the nearshore submarine fan sandy conglomerate body.

[0063] Hereinafter, taking the S1 sand member of the lower fourth member of the Shahejie Formation in the Shengtuo-Lijin area in the northern part of the Dongying Depression as an example, the scale prediction technology for sandy conglomerate bodies in the steep slope zone based on basin margin faults and basement attitude proposed by the present invention will be described in detail, specifically including the following steps as Figure 1 shown:

[0064] Step 1, establish an isochronous stratigraphic framework based on drilling and seismic data, and identify basin margin faults and basement, specifically including the following steps:

[0065] Step 1.1, finely divide the lower fourth member of the Shahejie Formation in the Shengtuo-Lijin area into four sand members, namely S1, S2, S3 and S4. On the basis of the fine stratigraphic division of a single well, combined with logging and mud logging data, establish a framework profile in the direction of sediment source (north-south) and perpendicular to the sediment source direction (east-west), as Figure 2 shown.

[0066] Step 1.2. Construct a well-seismic profile in the 3D seismic data volume. Through well-seismic correlation, establish an isochronous stratigraphic framework based on seismic data. Flatten the top surface with the top boundary of the upper sub-member of the fourth member of the Shahejie Formation as the marker bed, and determine the geological reflection characteristics of the interfaces of each sand member. On the seismic profile, identify the basin-margin faults, and use the bottom interface of the lower sub-member of the fourth member of the Shahejie Formation as the sedimentary basement, as Figure 3 shown.

[0067] Step 1.3. Based on the division criteria in Step 1.2, conduct stratigraphic division and correlation, and identify basin-margin faults and basement on the main survey lines and connecting lines in the seismic work area in sequence.

[0068] Step 2. Characterize the subaqueous fan sandstone-gravel rock bodies in the sedimentary facies belt, specifically including the following steps:

[0069] Step 2.1. Constrained by the isochronous stratigraphic framework established in Step 1, take the paleo-gully system as the unit, and anatomize the sandstone-gravel rock fans in the work area in the directions of the main survey line and the connecting survey line in sequence. Use the well-seismic combination method to finely characterize the distribution of fans in different periods. Through the identification of seismic profile characteristics, judge the fan facies belts corresponding to different seismic facies, characterize the pinch-out positions of seismic facies, and calibrate the pinch-out points of sandstone-gravel rock fans in different periods. The seismic facies characterization techniques for different facies belts are as follows:

[0070] 1) Fan root of the subaqueous fan near the shore

[0071] The rock sorting of the fan root facies belt is poor, and the main seismic reflection characteristics are wedge-shaped chaotic, wedge-shaped progradational, and wedge-shaped blank reflections. Different periods of main channels of the fan root are divided by different trough mudstone segments.

[0072] 2) Fan middle of the subaqueous fan near the shore

[0073] Braided main channels are mainly developed in the fan middle facies belt, and the seismic profile shows strong amplitude characteristics. The mud content in the fan middle facies belt is more than that in the fan root and is developed stably. The mudstone interlayers in the fan middle are obvious in seismic reflection, showing stable reflections between independent reflection isochrons. The lens-shaped or progradational reflection axes separated represent fans in different periods. Profile of the sedimentary facies belt of the subaqueous fan near the shore, as Figure 4 shown.

[0074] 3) Fan tip of the subaqueous fan near the shore

[0075] The reflection continuity is good, the amplitude of the isochron is weak, and the seismic reflection characteristics are lens-shaped or small mound-shaped reflections of the isochron.

[0076] Step 2.2: According to the nearshore submarine fan sandy conglomerate body characterization technology described in Step 2.1, identify seismic facies every 10 traces in the 3D seismic data volume, finely characterize the distribution of the sandy conglomerate bodies in the whole area, and draw the planar distribution map of the nearshore submarine fan sandy conglomerate bodies of the S1 sand member in the upper Es4 submember in the Shengtuo-Lijin area, as Figure 5 shown.

[0077] Step 3: Establish the relationship between the parameters of the basin margin fault and basement attitude and the geometric shape parameters of the sandy conglomerate body, which specifically includes the following steps:

[0078] Step 3.1: Based on the basin margin fault and basement morphology identified in Step 1.2, measure the dip angle of the basin margin fault and the basement slope angle every 10 seismic data traces. Among them, the dip angle of the basin margin fault is the angle between the fault plane and the horizontal plane, and the basement slope angle is the angle between the basement tangent and the horizontal plane. The depression angle is positive and the elevation angle is negative, as Figure 6 shown. Statistically summarize the measured data.

[0079] Step 3.2: Based on the morphology of the nearshore submarine fan sandy conglomerate characterized in Step 2, measure the length L and width W of the sandy conglomerate body once. Among them, the length of the sandy conglomerate body refers to the maximum extension distance of the sandy conglomerate body in the direction of the provenance, and the maximum length is the longest extension distance. The width of the fan body refers to the maximum width of the fan body in the direction perpendicular to the provenance ( Figure 6 -b). Under the constraint of the facies belt boundary, measure the length and width of the fan body extending to the fan root, fan middle and fan end respectively, and statistically summarize the measured data.

[0080] Step 4: Establish a mathematical model for predicting the scale of the nearshore submarine fan sandy conglomerate body based on the basin margin fault and basement attitude. Specifically, it includes the following steps:

[0081] Step 4.1: Based on the statistical data in Step 3, using the sine values of the dip angle of the basin margin fault and the basin slope angle as independent variables and the length of the nearshore submarine fan sandy conglomerate body as the dependent variable, perform binary linear regression using SPSS software to establish a mathematical representation model (Equations 1-3) for the length of the nearshore submarine fan sandy conglomerate body extending to different facies belts in the S1 sand member of the upper Es4 submember in the Shengtuo-Lijin area.

[0082] L 1 = 5.278×sinα + 0.286×sinβ - 3.644 Equation 1

[0083] L 2 = 7.831×sinα + 0.596×sinβ - 5.152 Equation 2

[0084] L 3 = 8.680×sinα + 0.490×sinβ - 5.393 Equation 3

[0085] In the formula, α is the dip angle of the basin margin fault, and β is the basin slope angle, with the unit of °; L1, L2, and L3 are the lengths of the fan extending along the provenance direction to the boundaries of the fan root, fan middle, and fan end respectively, with the unit of km.

[0086] Step 4.2: Based on the statistical data in Step 2.2, taking the lengths and widths of the subaqueous fan sandy conglomerate bodies extending to different facies belts as independent and dependent variables respectively, plot a scatter diagram of the length-width relationship as Figure 7 shown, and perform a unary linear regression to establish a mathematical characterization model (Equation 4-6) for the width of the sandy conglomerate bodies in the S1 sand member of the upper submember of the fourth member of the Shahejie Formation in the Shengtuo-Lijin area.

[0087] W1 = 0.612×L1 + 0.449 Equation 4

[0088] W2 = 0.326×L2 + 0.770 Equation 5

[0089] W3 = 0.596×L3 + 0.530 Equation 6

[0090] In the formula, L1, L2, and L3 are the lengths of the fan extending along the provenance direction to the boundaries of the fan root, fan middle, and fan end respectively, with the unit of km; W1, W2, and W3 are the widths perpendicular to the provenance direction at the fan root, fan middle, and fan end respectively, with the unit of km.

[0091] A prediction system for the scale of sandy conglomerate bodies in a steep slope zone, the prediction system comprising:

[0092] An isochronous stratigraphic framework establishment module for establishing an isochronous stratigraphic framework based on drilling and seismic data and identifying basin margin faults and the basement;

[0093] A fan sandy conglomerate body characterization module for characterizing subaqueous fan sandy conglomerate bodies in the sedimentary facies belt;

[0094] A parameter relationship construction module for constructing the relationship between the occurrence parameters of basin margin faults and the basement and the geometric shape parameters of sandy conglomerate bodies;

[0095] A mathematical model construction module for constructing a mathematical model for predicting the scale of subaqueous fan sandy conglomerate bodies based on the occurrence of the basin margin faults and the basement.

[0096] Beneficial effects: The present invention proposes a technology for predicting the scale of sandy conglomerate bodies in a steep slope zone based on the occurrence of basin margin faults and the basement. By combining the dip angle of the basin margin fault, the basement slope, and the morphological parameters of the sandy conglomerate bodies, a corresponding mathematical model is established to achieve fine prediction of the scale of subaqueous fan sandy conglomerate bodies.

[0097] The above specific embodiments have further elaborated in detail the object, technical solution and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for predicting the scale of gravel mass in steep slopes, characterized in that: The prediction method comprises: Step S1: Establish an isochronous stratigraphic framework based on drilling and seismic data to identify basin margin faults and basement; Step S2: Characterization of nearshore underwater fan gravel body based on sedimentary facies belt; Step S3: construct the relationship between the basin margin fault and basement attitude parameters and the geometric parameters of the gravel body; Step S4: constructing a mathematical model for predicting the scale of the nearshore underwater fan gravel body based on the basin margin fault and the basement attitude.

2. The method for predicting the scale of gravel mass in steep slope according to claim 1, characterized in that: The step S1: establishing an isochronous stratigraphic framework based on drilling and seismic data to identify basin margin faults and basement specifically includes: Step S1.1: Divide a region according to the division criteria and establish a skeleton profile based on well logging and mud logging data; Step S1.2: construct a well seismic profile in the 3D seismic data volume, establish an isochronous stratigraphic framework based on seismic data through well-seismic comparison, flatten the top surface with the top boundary of a certain area as the landmark layer, and determine the geological reflection characteristics of the interface of each sand layer group; identify the basin margin fault on the seismic profile, and use the interface of a certain area as the sedimentary basement; Step S1.3: Based on the division standard, stratigraphic division and comparison and identification of basin margin faults and basement are performed on the main survey lines and contact lines in the seismic work area in turn.

3. The method for predicting the scale of gravel mass in steep slope according to claim 2, characterized in that: The dividing of a certain area according to the division standard specifically includes: dividing the area into four sand layer groups, namely, a first sand layer group S1, a second sand layer group S2, a third sand layer group S3 and a fourth sand layer group S4 according to the division standard.

4. The method for predicting the scale of gravel mass in steep slope according to claim 2, characterized in that: The establishing of a skeleton section by combining logging and mud logging data specifically includes: establishing a skeleton section along the provenance direction and perpendicular to the provenance direction by combining logging and mud logging data.

5. The method for predicting the scale of gravel mass in steep slope according to claim 1, characterized in that: The step S2: characterizing the nearshore underwater fan gravel body based on the sedimentary facies belt specifically includes: Step 2.1, under the constraints of the isochronous stratigraphic framework, taking the ancient gully system as a unit, dissect the conglomerate fan in the work area in the direction of the main survey line and the connecting survey line; The fan distribution of multiple periods is finely depicted by combining well and seismic data. Through the identification of seismic profile characteristics, the fan phase belts corresponding to multiple seismic phases are determined, the pinch-out positions of seismic phases are described, and the pinch-out points of the sandstone fans in multiple periods are calibrated; Step 2.2, according to the nearshore underwater fan conglomerate body characterization technology described in step 2.1, the seismic phase is identified at intervals of 10 in the three-dimensional seismic data body, the distribution of the conglomerate body in the whole area is finely characterized, and the plan distribution map of the nearshore underwater fan conglomerate body of the first sand layer group S1 in a certain area is drawn.

6. A method for predicting the scale of gravel mass in a steep slope according to claim 5, characterized in that: The seismic phase characterization method of the multiple phase belts includes: nearshore underwater fan root, nearshore underwater fan middle, and nearshore underwater fan end.

7. A method for predicting the scale of gravel mass in a steep slope according to claim 6, characterized in that: The method for depicting the root of the nearshore underwater fan specifically includes: The rock sorting in the fan root facies is poor, and the seismic reflection characteristics are mainly wedge-shaped chaotic, wedge-shaped retrograde and wedge-shaped blank reflections. The main water channels of the fan root of different periods are divided by different trough mudstone sections.

8. The method for predicting the scale of gravel mass in steep slope according to claim 6, characterized in that: The characterization method in the nearshore underwater fan includes: The fan-mid phase zone mainly develops braided main waterways, and the seismic profile shows strong amplitude characteristics. The mud content of the fan-mid phase zone is higher than that of the fan root and is stably developed. The mudstone interlayer in the fan is obvious in seismic reflection, showing stable reflections between independent reflection phase axes, and the separated lens-shaped or foreset reflection axes represent the fan bodies of different periods.

9. The method for predicting the scale of gravel mass in steep slope according to claim 6, characterized in that: The characterization method of the nearshore underwater fan end includes: good reflection continuity, weak event axis amplitude, and seismic reflection characteristics of the event axis lens-shaped or small hillock-shaped reflection.

10. The method for predicting the scale of gravel mass in steep slope according to claim 1, characterized in that: The step S3: constructing the relationship between the basin margin fault and basement attitude parameters and the geometric parameters of the gravel body specifically includes: Step 3.1, based on the basin margin fault and basement morphology identified in step S1.2, measure the basin margin fault dip angle and basement slope angle every 10 seismic data channels; Among them, the dip angle of the basin margin fault is the angle between the fault plane and the horizontal plane, the basement slope angle is the angle between the basement tangent and the horizontal plane, the depression angle is positive and the elevation angle is negative; the measured data are statistically summarized; Step 3.2, based on the nearshore underwater fan conglomerate morphology depicted in step S2, measure the length L and width W of the conglomerate body, where the length of the conglomerate body refers to the maximum extension distance of the conglomerate body along the provenance direction, the maximum length is the longest extension distance, and the fan width refers to the maximum width of the fan body in the direction perpendicular to the provenance direction; Under the constraint of the facies boundary, the length and width of the fan extending to the fan root, fan middle and fan end are measured respectively, and the measured data are statistically summarized.

11. The method for predicting the scale of gravel mass in steep slope according to claim 1, characterized in that: The step S4: constructing a mathematical model for predicting the scale of the nearshore underwater fan gravel body based on the basin margin fault and the basement attitude specifically includes: On the basis of the statistical data in step S3, the sine values ​​of the basin margin fault dip angle and the basin slope angle were used as independent variables, and the length of the nearshore underwater fan conglomerate was used as the dependent variable. The SPSS software was used for binary linear regression to establish a mathematical characterization model of the length of the nearshore underwater fan conglomerate extending to different phase zones in the S1 sand layer group of the upper sub-member of the fourth segment of the Shahejie in the Shengtuo-Lijin area, as shown in Equation 1-3; L1=5.278×sinα+0.286×sinβ-3.644 Formula 1 L2=7.831×sinα+0.596×sinβ-5.152 Formula 2 L3=8.680×sinα+0.490×sinβ-5.393 Formula 3 Where, α is the dip angle of the basin margin fault, β is the basin slope angle, unit: °; L1, L2, L3 are the lengths of the boundaries of the fan body extending to the fan root, fan middle and fan end along the provenance direction, unit: km; Step 4.2, based on the statistical data in step 2.2, the length and width of the nearshore underwater fan conglomerate extending to different phase zones are used as independent variables and dependent variables, respectively, and a length-width relationship scatter plot is drawn, and a univariate linear regression is performed to establish a mathematical characterization model 4-6 for the width of the conglomerate of the sand layer group of the S1 sand layer group of the upper subsection of the fourth segment of the Shahejie in the Shengtuo-Lijin area; W1=0.612×L1+0.449 Formula 4 W2=0.326×L2+0.770 Equation 5 W3=0.596×L3+0.530 Formula 6 Among them, L1, L2, and L3 are the lengths of the fan body extending to the boundaries of the fan root, fan center, and fan end along the source direction, respectively, in km; W1, W2, and W3 are the widths of the fan root, fan center, and fan end perpendicular to the source direction, respectively, in km.

12. A system for predicting the scale of gravel mass in a steep slope zone, using the method for predicting the scale of gravel mass in a steep slope zone as described in claims 1 to 11, characterized in that: The prediction system comprises: Isochronous stratigraphic framework building module, used to build an isochronous stratigraphic framework based on drilling and seismic data to identify basin margin faults and basement; The fan conglomerate characterization module is used to characterize the nearshore underwater fan conglomerate based on the sedimentary facies belt; Parameter relationship building module, used to build the relationship between basin margin fault and basement attitude parameters and the geometric morphological parameters of the sandstone body; The mathematical model building module is used to build a mathematical model for predicting the scale of the nearshore underwater fan gravel body based on the basin margin fault and the basement attitude.

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