A method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins

Abstract

The present invention relates to the technical field of evaluation of the sealing capacity of tension-torsion faults, and in particular to a method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins, using seismic data to perform three-dimensional seismic fine interpretation of tension-torsion faults and formations in deep-sea clastic rock areas, and characterize the development morphology of faults, using deep-sea basin seismic data to quantitatively evaluate the oblique-slip sealing capacity of tension-torsion faults in complex clastic salt formations, calculate the oblique-slip sealing index, and establish a quick lookup table of fault oblique-slip sealing indexes, so as to quickly evaluate the sealing capacity of oblique-slip faults in target areas. The present invention can accurately and quantitatively evaluate the sealing capacity of tension-torsion faults in complex clastic rock formations in deep-sea basins, and can also evaluate the sealing capacity of tension-torsion faults in complex clastic rock formations on land, and has strong universality.

Description

Technical Field

[0001] The invention belongs to the technical field of deep-sea oil and gas exploration, and in particular relates to a method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins. Background Art

[0002] A tension-torsion fault is a type of fault formed by relative oblique sliding of the two fault plates under a tension-torsion tectonic environment. It is characterized by having both the tension vertical component of a normal fault and the horizontal torsion component of a strike-slip fault. In the clastic rock formations with interlayers of sandstone and mudstone, normal faults usually form fault closures by causing mudstone smearing through dislocation. At present, a relatively mature technology has been formed to evaluate its closure capacity. The main quantitative evaluation formula SGR is used to reflect the relationship between mudstone thickness and fault throw. However, this method is carried out for normal faults without horizontal torsion components and only with tension vertical components, but there is still a lack of effective quantitative evaluation methods for tension-torsion faults with both tension vertical components and horizontal torsion components. In recent years, tension-torsion faults have played an important controlling role in oil and gas enrichment. Their closure capacity affects the evaluation of the effectiveness of oil and gas reservoir closures. Accurate evaluation of the closure capacity of tension-torsion faults is of great significance for guiding oil and gas exploration.

[0003] For tensile faults developed in clastic rock formations, their sealing ability is mainly related to the mudstone that breaks through the fault and is smeared on the fault surface under high temperature and high pressure conditions. The larger the smearing area, the stronger the fault sealing ability. Due to the characteristics of deep water bodies and deep burial of oil and gas reservoirs, the data obtained from deep-sea basins are very limited. Geophysics is the main data type, but there is currently a lack of methods to directly use geophysical data to quantitatively evaluate the sealing ability of tensile-torsional faults. However, for tensile-torsional faults, the existence of horizontal torsional components makes the mudstone smearing not only in the vertical direction, but also in the oblique direction. Therefore, limiting the smearing area of ​​the tensile-torsional fault mudstone has become an important part of evaluating its sealing ability.

[0004] Therefore, the present invention provides a method for quantitatively evaluating the oblique-slip sealing capacity of tension-torsion faults in complex clastic salt formations using only deep-sea basin seismic data when limited data are available during marine oil and gas exploration. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins, comprising the following steps:

[0006] S1. Use seismic data to extract and analyze three-dimensional seismic geological information of tension-torsion faults and strata in deep-sea clastic rock areas, and characterize the occurrence characteristics of fault sections and fault disks;

[0007] S2. Use structural modeling software to perform three-dimensional modeling on the tension-torsion fault and determine the spatial characteristics of the tension-torsion fault;

[0008] S3. Use deep-sea basin seismic data to quantitatively evaluate the oblique-slip closure capacity of tension-torsion faults in complex clastic salt formations and calculate the oblique-slip closure index NOFI.

[0009] S4. According to the actual geological conditions of the target area, a quick reference table of the fault oblique slip closure index NOFI is established, and the oblique slip closure index NOFI is matched with the closure capacity to quickly evaluate the closure capacity of the oblique slip fault in the target area.

[0010] In a preferred embodiment, the NOFI formula is:

[0011] NOFI= = ;

[0012] Where: α is the dip angle of the fault, β is the side fall angle of the fault, H is the vertical throw of the fault, h is the true thickness of the formation, L is the fault throw, It is the fault distance along the section perpendicular to the fault strike. is the fault distance along the fault strike, T is The horizontal component of .

[0013] In a preferred embodiment, the calculation formula of the fault distance L is as follows:

[0014] L= .

[0015] In a preferred embodiment, the density of the measurement grid is adjusted according to the accuracy of the geophysical seismic data and the scale of the target tension-torsion fault. When the seismic data accuracy is high and the scale of the target tension-torsion fault is large, the density of the interpretation grid is increased.

[0016] In a preferred embodiment, a drilling core passing through a fault is selected, and the fault plane dip angle and scratch side angle are measured on the fault plane exposed in the core, and the measured dip angle α and side angle β are verified and calibrated respectively.

[0017] In a preferred embodiment, the seismic data includes: seismic amplitude and coherence volume attributes.

[0018] In a preferred embodiment, the spatial characteristics of the torsional fault include the strike, dip, inclination and fault throw of the tension-torsion fault at different locations.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The present invention aims at the existing difficulty, inaccuracy and lack of quantitative analysis methods in evaluating the sealing capacity of tensile-torsion faults in complex clastic rock formations in deep-sea basins. The present invention has few requirements for data and only requires seismic data of the corresponding area for evaluation, and can accurately and quantitatively evaluate the sealing capacity of tensile-torsion faults in complex clastic rock formations in deep-sea basins. In addition, the present invention can also evaluate the sealing capacity of tensile-torsion faults in complex clastic rock formations on land, and has strong universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of three-dimensional modeling of tension-torsion faults. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] The method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in a deep-sea basin of the present invention comprises:

[0024] The three-dimensional seismic geological information of the tension-torsion faults and strata in the deep-sea clastic rock area is extracted and analyzed using data such as seismic amplitude and coherence body attributes, and the occurrence characteristics of the fault sections and fault disks are characterized. The interpretation grid density is 4×4.

[0025] In this process, the density of the measurement grid should be adjusted according to the accuracy of the geophysical seismic data and the scale of the target tension-torsion fault. When the seismic data is highly accurate and the scale of the target tension-torsion fault is large, the density of the interpretation grid can be appropriately increased to 2×2.

[0026] Using structural modeling software, three-dimensional modeling of tension-torsion faults is carried out to determine the spatial characteristics of tension-torsion faults such as strike, dip, inclination and fault throw at different locations.

[0027] like Figure 1 As shown, represents the direction of the principal stress, They correspond to the components along the fault direction and perpendicular to the fault direction respectively; in the three-dimensional modeling of the tension-torsion fault, the seismic profile P1 perpendicular to the fault direction is selected to measure the fault dip and the true thickness h of the mudstone layer; select point a on the footwall (upward wall) and its corresponding point b on the hanging wall (downward wall); the footwall refers to the wall located below the fault plane, which rises relative to the other wall in a tension-torsion fault, and the hanging wall refers to the wall located above the fault plane, which descends relative to the other wall in a tension-torsion fault;

[0028] Take the section P2 perpendicular to the fault direction through point b. The section intersects the fault and the phase axis through point a at point c. Measure the distance between point c and point b respectively. , as well as horizontal distance T, vertical distance (vertical distance) H;

[0029] Measure the distance between P1 and P2 , from L = Calculate the distance L between point a and point b;

[0030] Take the angle β between line segment ac and line segment ab and calculate:

[0031] sinβ = ;

[0032] cosβ = ;

[0033] cosα = ;

[0034] Select the drill core that passes through the fault, and measure the fault plane dip angle and scratch side angle on the fault plane exposed in the core. and side angle Perform a verification calibration.

[0035] The oblique-slip sealing capacity of tension-torsional faults in complex clastic salt strata is quantitatively evaluated using deep-sea basin seismic data, and the oblique-slip sealing index NOFI is calculated.

[0036] The NOFI formula is:

[0037] NOFI= = ;

[0038] Where: is the fault dip, is the side fall angle of the fault, H is the vertical fault throw of the fault, h is the true thickness of the formation, L is the fault throw, It is the fault distance along the section perpendicular to the fault strike. is the fault distance along the fault strike, T is The horizontal component of .

[0039] Since the thickness of the mudstone layer and the fault throw significantly affect the smear area, the mudstone thickness parameter (h), distance parameters (H, L, L M , L N , T) is positively correlated with the fault's oblique slip closure index; in addition, the closure capacity of the tension-torsion fault is also controlled by the tightness of the section, and the angle parameter ( ) indirectly affects the tightness of the section by affecting the weight of the fault hanging plate, and is negatively correlated with the oblique slip closure index of the fault.

[0040] The NOFI formula can solve the problem of quantitative evaluation of the sealing capacity of tension-torsion faults in the process of oil and gas exploration and evaluation of complex clastic rock formations in deep-sea basins. Using this formula, the sealing capacity of tension-torsion faults can be evaluated more accurately in the absence of geological data in the target area.

[0041] According to the actual geological conditions of the target area, a quick reference table of fault oblique slip closure index (NOFI) is established, and the oblique slip closure index NOF is matched with the closure capacity, so as to quickly evaluate the closure capacity of oblique slip faults in the target area. The larger the NOFI, the stronger the closure capacity.

[0042] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0044] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins, characterized in that: The steps include: S1. Use seismic data to extract and analyze three-dimensional seismic geological information of tension-torsion faults and strata in deep-sea clastic rock areas, and characterize the occurrence characteristics of fault sections and fault disks; S2. Using structural modeling software, three-dimensional modeling is performed on the tension-torsion fault to determine the spatial characteristics of the tension-torsion fault; S3. Using deep-sea basin seismic data, quantitatively evaluate the oblique-slip closure capacity of tension-torsion faults in complex clastic salt formations, and calculate the oblique-slip closure index NOFI; the formula of the oblique-slip closure index NOFI is: ； Where: is the fault dip, is the lateral angle of the fault, is the vertical distance of the fault, is the true thickness of the formation, is the fault distance, It is the fault distance along the section perpendicular to the fault strike. is the fault throw along the fault strike, for The horizontal component of S4. According to the actual geological conditions of the target area, a quick reference table of the fault oblique slip closure index NOFI is established, and the oblique slip closure index NOFI is matched with the closure capacity to quickly evaluate the closure capacity of the oblique slip fault in the target area.

2. The method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins according to claim 1, characterized in that: Fault Distance The calculation formula is as follows: 。 3. The method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins according to claim 1, characterized in that: The density of the measurement grid is adjusted according to the accuracy of the geophysical seismic data and the scale of the target tension-torsion fault. When the seismic data accuracy is high and the scale of the target tension-torsion fault is large, the density of the interpretation grid is increased.

4. The method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins according to claim 1, characterized in that: Drilling cores passing through faults are selected, and the fault plane dip angle and scratch side angle are measured on the fault plane exposed in the drilling cores. The measured dip angle α and side angle β are verified and calibrated respectively.

5. The method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins according to claim 1, characterized in that: The seismic data include: seismic amplitude and coherence volume attributes.

6. The method for evaluating the sealing capacity of tension-torsion faults in clastic rock formations in deep-sea basins according to claim 1, characterized in that: The spatial characteristics of the torsional fault include the strike, dip, inclination and fault throw of the tension-torsion fault at different locations.

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