A method for predicting the distribution range of deep-water turbidite sand bodies

Abstract

The present application relates to the technical field of oilfield exploration and development, and particularly relates to a method for predicting the distribution range of deep-water turbidite sand bodies. The method comprises the following steps: using three-dimensional seismic data, actual drilling well data and velocity data to calculate the maximum thickness of the sedimentary sand body of the upthrown wall of the fault which provides the source for the turbidite sand body; calculating the fault throw according to the development form of the three-dimensional seismic interpretation fault in the work area, and comprehensively considering the seismic, velocity and well data; determining the dip angle of the downthrown wall stratum through the two-dimensional seismic profile perpendicular to the fault strike; based on the drilling and logging data, according to the thickness of the deep-water turbidite sand body in the higher exploration degree area of the research area and the critical value of the deep-water turbidite sand body, drawing the sand body thickness contour map of the research area, so as to determine the distribution range of the deep-water turbidite sand body in the higher exploration degree area. The method is suitable for accurately predicting the distribution range of the deep-water turbidite sand body in the faulted basin.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield exploration and development, and relates to a method for predicting the distribution range of a deep-water turbidite sand body suitable for the downthrown wall of a two-step fault in a rift basin. BACKGROUND

[0002] With the improvement of exploration degree, the deep-water turbidite sand body becomes a favorable exploration target for oil and gas development in a rift basin. The deep-water turbidite sand body is a kind of near-source rapid accumulation type of deposition. The continental rift basin has the characteristics of strong tectonic activity and complex geomorphic features. Some secondary growth faults are developed in the steep slope zone. The deep-water turbidite sand body related to the deposition of the sand-gravel body in the upper wall is often developed in the downthrown wall of the secondary growth fault. The overlying stratum of the deep-water turbidite sand body is a deep-lake facies calcareous mudstone. When the three-dimensional seismic interpretation technology is used to delineate the distribution range of the deep-water turbidite sand body, the continuous strong reflection of the calcareous mudstone concentrated section on the seismic profile is similar to the seismic characteristics of the turbidite sand body, which interferes with the identification of the turbidite sand body. The prediction of the turbidite sand body is affected by the increased gray content of the sand body edge, and it is difficult to delineate the turbidite sand body boundary on the seismic reflection characteristic representation. When the actual exploration work is carried out, there is a large error in the delineation of the distribution range of the deep-water turbidite sand body. At present, this error is difficult to completely eliminate by the three-dimensional seismic method, and needs to be analyzed comprehensively by using other methods.

[0003] Chinese invention patent CN112417664A discloses a numerical simulation method for thin interbedded reservoir considering sand body distribution law, which comprises the following steps: step one, constructing a thin interbedded sand body distribution quantitative prediction knowledge base of the target area; step two, establishing a sand body distribution range prediction model in different directions under different small layer drilling thicknesses of the target well; step three, quantifying the corresponding relationship between reservoir connectivity and injection-production well pattern; step four, establishing an oil reservoir numerical simulation model, and obtaining the conductivity data field of the oil reservoir numerical simulation model; step five, initializing the oil reservoir numerical simulation model by using the obtained oil reservoir numerical simulation model conductivity data field, performing numerical simulation calculation, and realizing simulation calculation of different development schemes by changing different conductivity data fields. The method uses the Gaussian configuration co-simulation geostatistics inversion method for the region where the target area is located, obtains a plurality of inversion bodies with equal probability, performs fine sand body carving on the inversion bodies, and then determines the spatial distribution of sand bodies in different layers, and establishes a thin interbedded reservoir sand body distribution prediction quantitative knowledge base.

[0004] Chinese invention patent CN111505720A discloses a method for depicting lithologic traps, which comprises the following steps: S1, selecting data capable of meeting the demand of lithologic trap depiction; S2, identifying dominant sedimentary facies belts; S3, identifying the type and distribution range of slope-break belts, and determining the favorable sand body distribution based on the slope-break belts; S4, quantitatively depicting the favorable sand body distribution, and completing the depiction of lithologic traps. Step S3 comprises: S31, identifying the type and distribution range of the slope-break belts by using a method of ternary coupling of micro-paleogeomorphology, stratigraphic dip angle attribute and instantaneous phase attribute; S32, establishing a lithologic body development model under the control of multi-stage slope-breaks, and determining the favorable sand body distribution.

[0005] Chinese invention patent application CN107917902A discloses a method for studying the possibility of negative structural formation of basin margin, which determines the sand body distribution rule by simultaneously performing sedimentary reservoir analysis on the basis of paleostructure restoration, so as to determine the oil and gas migration direction, oil and gas transport system and the maximum range of oil and gas sweep in different reservoir forming stages.

[0006] At present, there is no effective calculation method for the distribution range of deepwater turbidite sand bodies in a faulted basin. On the one hand, the early exploration of turbidite reservoirs focused on potato-shaped slump turbidite sand bodies, and on the other hand, the main control factors of the distribution range of sand bodies are complex and have not been quantitatively characterized due to the influence of multi-stage tectonic movements and source transportation after deposition. Therefore, there is an urgent need for a calculation method suitable for the distribution range of deepwater turbidite sand bodies in a faulted basin. SUMMARY

[0007] The main purpose of the present application is to provide a method for predicting the distribution range of deepwater turbidite sand bodies, which takes into account the factors such as source supply, fault activity and paleogeomorphology of deepwater turbidite sand bodies in a complex tectonic setting of a faulted lake basin, and is suitable for accurate prediction of the distribution range of deepwater turbidite sand bodies in a faulted basin.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] The present application provides a method for predicting the distribution range of deepwater turbidite sand bodies, which comprises the following steps:

[0010] The maximum thickness of the sand body deposited on the upthrown side of the fault providing source for the turbidite sand body is calculated by using three-dimensional seismic data, actual drilling data and velocity data;

[0011] The fault throw is calculated according to the development form of the fault in the three-dimensional seismic interpretation of the work area, and by comprehensively analyzing the seismic, velocity and well data;

[0012] The stratigraphic dip angle of the downthrown side is determined by a two-dimensional seismic profile perpendicular to the strike of the fault;

[0013] Based on the drilling well logging data, according to the thickness of the deepwater turbidite sand body and the critical value of the deepwater turbidite sand body in the high exploration degree area of the research area, the sand body thickness contour map of the research area is drawn, so as to determine the distribution range of the deepwater turbidite sand body in the high exploration degree area.

[0014] Further, the method further comprises: selecting a plurality of profiles in the order of the source direction in the high exploration area of the research area, and calculating the linear correlation constants of the deepwater turbidite sand body distribution distance and the variables in the research area; for the low exploration area of the research area, selecting the profile in the order of the source direction, and calculating the variables in the corresponding profile.

[0015] Further, the 5m thickness of the sandy conglomerate is taken as the critical value of the deepwater turbidite sand body.

[0016] Further, the maximum thickness H of the ascending disc sedimentary sand body, the fault throw Δh and the dip angle α of the descending disc stratum are used to take the 5m thickness of the sandstone as the sand body distribution boundary, a plurality of variables H, Δh, α and the deepwater turbidite rock distribution distance L are calculated, and the linear correlation constants a, b, c and d of the deepwater turbidite sand body distribution distance and the variables in the research area are calculated.

[0017] Further, the calculation formula L=a*H+b*Δh+c*α+d is used, for the low exploration area of the research area, the profile in the order of the source direction is selected, the variables in the corresponding profile are calculated: the maximum thickness H of the ascending disc sedimentary sand body, the fault throw Δh and the dip angle α of the descending disc stratum, and the deepwater turbidite sand body distribution distance L of the corresponding position of the profile is calculated.

[0018] Further, the exploration area with the well density greater than 0.1 well / km 2 is the high exploration area.

[0019] Further, the exploration area with the well density less than 0.1 well / km 2 is the low exploration area.

[0020] Further, the research area is a rift basin.

[0021] The prediction method suitable for the distribution range of the deepwater turbidite sand body on the downthrown side of the two-step fault in the fault basin in the application is based on the main control factors of the distribution range of the deepwater turbidite sand body, selects the three parameters of the maximum thickness of the sedimentary sand body on the upthrown side of the fault, the fault throw and the stratigraphic dip angle of the downthrown side to quantitatively characterize the distribution range of the deepwater turbidite sand body on the downthrown side, fully considers the main control factors of the distribution range of the deepwater turbidite sand body on the downthrown side on the basis of the maximum simplification. Therefore, the application has important reference significance for the quantitative characterization of the distribution range of the deepwater turbidite sand body on the downthrown side of the two-step fault in the fault basin, can also quantitatively characterize the planar distribution range of the deepwater turbidite sand body on the downthrown side of the two-step fault in the fault basin to the maximum extent combined with three-dimensional seismic, and provides favorable support for the effectiveness of the sand body description in the deepwater turbidite sand body exploration.

[0022] Compared with the prior art, the application has the following advantages:

[0023] (1) The application establishes the linear correlation between the turbidite sand body distribution distance L and the maximum thickness H of the sedimentary sand body on the upthrown side of the fault, the fault throw Δh and the stratigraphic dip angle α of the downthrown side, and realizes the quantitative characterization of the sand body distribution distance;

[0024] (2) The application establishes the work flow of calculating the correlation coefficient from the high exploration degree area and calculating the turbidite sand body distribution distance in the low exploration degree area, the parameter acquisition method is simple and reasonable, and the technical flow is strong in operability;

[0025] (3) The application overcomes the difficulty that the turbidite sand body boundary in the calcareous mudstone development area is difficult to accurately depict from the seismic data, realizes the target of determining the turbidite sand body range based on simple geological parameters, and the method is strong in practicability. BRIEF DESCRIPTION OF DRAWINGS

[0026] The drawings accompanying the specification of the application form a part of the application and serve to provide further understanding of the application, and the schematic embodiments of the application and the description thereof serve to explain the application, and do not constitute improper limitations on the application.

[0027] Figure 1 The flow chart of the prediction method of the deepwater turbidite sand body distribution range in the embodiment 1 of the application;

[0028] Figure 2 The calculation method of the three parameters of the maximum thickness of the sedimentary sand body on the upthrown side of the fault, the fault throw and the stratigraphic dip angle of the downthrown side in the embodiment 1 of the application is shown in the profile schematic diagram along the source direction;

[0029] Figure 3 The schematic diagram of the linear correlation constant a, b, c and d of the deepwater turbidite sand body distribution distance and the variable in the research area in the embodiment 1 of the application for the area with higher exploration degree is the drawing of the fan sandstone thickness contour map. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, 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 invention pertains.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0033] Example 1

[0034] like Figure 1 As shown, the method for predicting the distribution range of deep-water turbidite sand bodies includes the following steps:

[0035] Step 101: Calculate the maximum thickness H of the fault-uplifted block sedimentary sand body that provides the source material for the turbidite sand body using 3D seismic data. Based on a comprehensive analysis of 3D seismic data, velocity data, and well data for the study area, calculate the cumulative displacement Δh of the overlying strata after the fan-shaped deposition, such as... Figure 2 As shown, the process proceeds to step 102;

[0036] Step 102, take a cross-section along the source direction, such as... Figure 2 As shown, the faults controlling the deposition of deep-water turbidite sand bodies are finely described through three-dimensional seismic interpretation. By integrating velocity data and well data, the fault displacement Δh is calculated, and the process proceeds to step 103.

[0037] Step 103: Determine the stratigraphic dip angle α using a two-dimensional profile perpendicular to the fault (along the source direction), such as... Figure 2 As shown. The process proceeds to step 104;

[0038] Step 104: Based on drilling and logging data, read the thickness N of the deep-water turbidite sand body in the higher exploration area of ​​the study area. Taking a 5m thickness of conglomerate as the critical value for the deep-water turbidite sand body, draw a contour map of the sand body thickness in this area to determine the distribution range of the deep-water turbidite sand body in the higher exploration area. Figure 3 The process proceeds to step 105;

[0039] Step 105: Select a higher exploration area (Area I) and create multiple profiles along the provenance direction, such as...Figure 3 With the obtained maximum thickness H of the rising disc deposition sand body, fault throw Δh and dip angle α of the falling disc stratum, the sand body distribution boundary is taken as the sandstone thickness 5m contour line, a plurality of variable (H, Δh, α) and deepwater turbidite sand body distribution distance (L) corresponding data are obtained, and the linear correlation constants a, b, c and d of the deepwater turbidite sand body distribution distance and the variable in the research area are obtained. The process enters step 106.

[0040] In step 106, finally, the calculation formula L=a*H+b*Δh+c*α+d is used, for the lower exploration area (II) of the research area, a profile along the source direction is selected, the variable (H, Δh, α) in the corresponding profile is obtained, and the deepwater turbidite sand body distribution distance L of the corresponding position of the profile is obtained. The process ends.

[0041] The prediction method of the deepwater turbidite sand body distribution range in the falling disc of the two-step fault in the rift basin in the application comprehensively considers the main control factors of the deepwater turbidite sand body distribution range, selects the maximum thickness of the rising disc deposition sand body, the fault throw and the dip angle of the falling disc stratum to quantitatively represent the deepwater turbidite sand body distribution range of the falling disc, fully considers the main control factors of the deepwater turbidite sand body distribution range of the falling disc on the basis of maximum simplification, and quantitatively represents the main control factors, and the method is reasonable. In the exploration of the steep slope sand gravel body in the rift basin, the method has wide popularization and application value.

[0042] The above embodiment is the preferred embodiment of the application, but the embodiment of the application is not limited by the above embodiment, and any change, modification, substitution, combination, simplification made without departing from the spirit and principle of the application should be an equivalent replacement method, and all are included in the protection scope of the application.

Claims

1. A method of predicting the extent of a deepwater turbidite sand body, characterized by, The method comprises the following steps: Using three-dimensional seismic data, drilling data and velocity data, the maximum thickness of the sedimentary sand body of the upthrown wall of the fault providing the source of the turbidite sand body is calculated; According to the development pattern of the fault in the three-dimensional seismic interpretation of the working area, the fault throw is calculated by comprehensively considering the seismic, velocity and well data; The dip angle of the downthrown wall stratum is determined through the two-dimensional seismic profile perpendicular to the fault strike; Based on the drilling and logging data, according to the thickness of the deepwater turbidite sand body in the high exploration degree area of the study area and the critical value of the deepwater turbidite sand body, the sand body thickness contour map of the study area is drawn, so as to determine the distribution range of the deepwater turbidite sand body in the high exploration degree area; The method further comprises the following steps: selecting a plurality of profiles in the source direction in the high exploration area of the study area, and calculating the linear correlation constants of the deepwater turbidite sand body distribution distance and the variables in the study area; for the low exploration area of the study area, selecting the profile in the source direction, and calculating the variables in the corresponding profile; The 5m thickness of the sandy conglomerate is taken as the critical value of the deepwater turbidite sand body; Using the maximum thickness H of the sedimentary sand body of the upthrown wall, the fault throw Δh and the dip angle α of the downthrown wall stratum, and taking the 5m thickness contour of the sandstone as the sand body distribution boundary, a plurality of variable H, Δh, α and deepwater turbidite rock distribution distance L corresponding data are calculated, and the linear correlation constants a, b, c and d of the deepwater turbidite sand body distribution distance and the variables in the study area are calculated; Using the calculation formula L=a*H+b*Δh+c*α+d, for the low exploration area of the study area, the profile in the source direction is selected, the variables H, Δh and α in the corresponding profile are calculated, and the deepwater turbidite sand body distribution distance L at the corresponding position of the profile is calculated.

2. The prediction method of claim 1, wherein, Exploration area with density of more than 0.1 well / km 2 is a higher exploration area.

3. The prediction method according to claim 1 or 2, characterized in that, Exploration density less than 0.1 well per km 2 The exploration area is a lower exploration area.

4. The prediction method according to claim 1 or 2 or 3, characterized in that, The study area is a fault basin.

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