Interpretation method of true and false faults caused by gypsum-salt rock

Abstract

The present invention discloses a method for interpreting true and false faults caused by gypsum-salt rock, including: tracking and interpreting the top and bottom of the gypsum-salt body to obtain the distribution law of the gypsum-salt body; establishing a gypsum-salt body geological model according to the distribution law of the gypsum-salt body; based on the gypsum-salt body geological model, obtaining the first seismic reflection characteristics corresponding to the distribution law of different gypsum-salt bodies and the second seismic reflection characteristics corresponding to the fault caused by the gypsum-salt sliding through forward modeling research; establishing a true and false fault judgment standard according to the forward modeling result; carrying out fault detection on the seismic data body, identifying and extracting all parts of the seismic reflection phase axis with dislocation; forming a preliminary fault body according to the part of the seismic reflection phase axis with dislocation; based on the preliminary fault body, counting the fault distance of the fault two-plate stratum dislocation characteristics on the seismic reflection profile; excluding the false faults in the preliminary fault body according to the true and false fault judgment standard and the fault distance, and obtaining the fault distribution. The present invention establishes a true and false fault judgment standard based on the forward model, and the result is more reliable.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration, and in particular to a method for interpreting true and false faults caused by gypsum-salt rocks. Background Art

[0002] Faults play a vital role in the process of oil and gas accumulation. On the one hand, they can block and form traps; on the other hand, they can also play a destructive role, causing the oil and gas in the trap to dissipate. In addition, faults can also play an important role in oil and gas transportation. Therefore, fault interpretation is an important part of structural interpretation.

[0003] At present, there are mainly two methods for fault interpretation:

[0004] Phase plane method tracking interpretation: Faults have significant signs on seismic sections, including: reflection wave phase axis misalignment; reflection phase axis bifurcation, merging, distortion, strong phase conversion and other phenomena; the number of reflection phase axes suddenly increases or disappears; reflection phase axis occurrence mutation, reflection disorder or blank zone; cross-section wave, diffraction wave phenomenon, etc. Phase plane method is the main method of fault interpretation at present. This method has the following problems: first, it is affected by resolution and can only explain large faults, but it is difficult to explain small faults; second, it has strong multi-solution.

[0005] Seismic attribute method: Based on the problem that small faults are difficult to identify in the face method, a fault attribute detection method has been developed. The seismic attribute method mainly uses seismic attributes to characterize the structural change information in seismic reflections, and then to characterize faults. Commonly used methods include coherence, ant tracking, and maximum likelihood attributes. The seismic attribute method has the following advantages: high efficiency, mainly through computer calculations, reducing the workload of manual interpretation; high resolution, can characterize small faults that are difficult to identify with the naked eye. However, the seismic attribute method has the following disadvantages: too strong multi-solution, structural changes caused by noise, lithology and other factors are all identified as faults, and there are too many illusions.

[0006] The above two methods are difficult to solve the false fault anomaly caused by the phase axis misalignment caused by the slippage of gypsum-salt rock. Summary of the invention

[0007] The purpose of the present invention is to overcome one or more deficiencies of the prior art and provide a method for interpreting true and false faults caused by gypsum-salt rocks.

[0008] The object of the present invention is achieved through the following technical scheme: A method for interpreting true and false faults caused by gypsum-salt rock comprises the following steps:

[0009] Using seismic data to trace and interpret the top and bottom of the gypsum-salt body, the distribution law of the gypsum-salt body is obtained;

[0010] Establishing a geological model of the gypsum-salt body according to the distribution law of the gypsum-salt body;

[0011] Based on the gypsum-salt geological model, the first seismic reflection characteristics corresponding to the distribution laws of different gypsum-salt bodies and the second seismic reflection characteristics corresponding to the faults caused by the gypsum-salt sliding are obtained through a forward modeling method;

[0012] Establishing a true or false fault judgment standard based on the first seismic reflection feature and the second seismic reflection feature;

[0013] Conduct fault detection on the seismic data volume for true and false fault interpretation, and identify and extract all parts of the seismic reflection phase axis that are dislocated;

[0014] forming a preliminary fault body according to the dislocated part of the seismic reflection event axis;

[0015] Based on the preliminary fault body, the fault throw of the two sides of the fault is calculated on the seismic reflection section;

[0016] According to the true and false fault judgment standard and fault distance, false faults in the preliminary fault body are eliminated to obtain the fault distribution.

[0017] Preferably, the criteria for judging true or false faults are: the fault throw is greater than 20 ms, and the fault throws of the upper and lower salt rock formations are equivalent.

[0018] Preferably, the fracture detection method includes one or more of an edge detection method, an ant body tracking method, a maximum likelihood attribute fracture detection method, and a frequency division body fusion display method.

[0019] The beneficial effects of the present invention are:

[0020] (1) The present invention establishes a true and false fracture judgment standard based on the forward model, and the result is more reliable and has strong operability;

[0021] (2) The seismic data of the present invention depicts fault bodies of various sizes, and uses the forward modeling standard to exclude false faults, thereby improving both the interpretation efficiency and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of the method for interpreting true and false faults caused by gypsum-salt rocks;

[0023] Figure 2 A schematic diagram for the detailed interpretation of the top and bottom of gypsum salt rock;

[0024] Figure 3 A schematic diagram of the fracture forward modeling results;

[0025] Figure 4 A schematic diagram for identifying faults for earthquake attributes;

[0026] Figure 5A schematic diagram of fault distance statistics and false fault exclusion. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0028] See also Figure 1-Figure 5 This embodiment provides a method for interpreting true and false faults caused by gypsum-salt rock:

[0029] like Figure 1 As shown in FIG. 1 , the method for interpreting true and false faults caused by gypsum-salt rock includes the following steps:

[0030] S1. Use seismic data to track and interpret the top and bottom of the gypsum-salt body to obtain the distribution pattern of the gypsum-salt body.

[0031] like Figure 2 A detailed interpretation of the top and bottom of gypsum salt rock is presented. Figure 2 It can be seen that the upper gypsum body is distributed throughout the area, while the lower gypsum body is distributed locally, and the upper and lower gypsum bodies are distributed in a symmetrical relationship of one increasing while the other decreases.

[0032] S2. Establishing a geological model of the gypsum-salt body according to the distribution law of the gypsum-salt body.

[0033] S3. Based on the gypsum-salt body geological model, the first seismic reflection characteristics corresponding to the distribution patterns of different gypsum-salt bodies and the second seismic reflection characteristics corresponding to the faults caused by gypsum-salt sliding are obtained through forward modeling methods.

[0034] S4. Establishing a true or false fault judgment standard based on the first seismic reflection characteristic and the second seismic reflection characteristic.

[0035] Figure 3 This is a forward modeling case in Sichuan. In forward model I, the thickness of the thunder salt changes, which has a differentiated downward pull effect on the underlying horizontal strata, causing a false fault in the imaging results of the underlying strata, but the fault amplitude is small, which is a false fault.

[0036] In forward model II, the fault extends upward from Jiayan to Leiyan. The imaging results show that the stratigraphic offset between the two salt (gypsum salt) layers is large, which is equivalent to or slightly larger than the Leiyan fault amplitude, and is a reliable fault.

[0037] In summary, the criteria for judging a true fault are that the fault offset is large and the fault throw is greater than 20ms; the fault throws of the upper and lower salt rock formations are equivalent.

[0038] S5. Perform fracture detection on the seismic data volume for true and false fault interpretation, and identify and extract all parts of the seismic reflection phase axis that are dislocated.

[0039] The fracture detection method includes one or more of an edge detection method, an ant body tracking method, a maximum likelihood attribute fracture detection method, and a frequency division body fusion display method.

[0040] Figure 4 The maximum likelihood attribute fracture data volume is superimposed with the conventional section. Figure 4 It can be seen that the seismic attributes depict the details of the event axis dislocation more clearly, which is conducive to fault identification and interpretation.

[0041] S6. A preliminary fault body is formed according to the displaced portion of the seismic reflection event axis.

[0042] S7. Based on the preliminary fault body, the fault distance of the stratum dislocation characteristics of the two sides of the fault is statistically analyzed on the seismic reflection profile.

[0043] S8. Eliminate false faults in the preliminary fault body according to the true and false fault judgment criteria and fault distance to obtain fault distribution.

[0044] For example, the faults with equal fault throws in the upper and lower gypsum-salt layers and fault throws greater than 20ms are retained, and the other false faults are eliminated. Figure 5 As shown, based on the fault throw statistics, false faults are excluded and true faults are retained.

[0045] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for interpreting true and false faults caused by gypsum-salt rock, characterized in that: The following steps are involved: Using seismic data to trace and interpret the top and bottom of the gypsum-salt body, the distribution law of the gypsum-salt body is obtained; Establishing a geological model of the gypsum-salt body according to the distribution law of the gypsum-salt body; Based on the gypsum-salt geological model, the first seismic reflection characteristics corresponding to the distribution laws of different gypsum-salt bodies and the second seismic reflection characteristics corresponding to the faults caused by gypsum-salt sliding are obtained through a forward modeling method; Establishing a true or false fault judgment standard based on the first seismic reflection feature and the second seismic reflection feature; Conduct fault detection on the seismic data volume for true and false fault interpretation, and identify and extract all parts of the seismic reflection phase axis that are dislocated; forming a preliminary fault body according to the dislocated part of the seismic reflection event axis; Based on the preliminary fault body, the fault throw of the two sides of the fault is calculated on the seismic reflection section; Eliminate false faults in the preliminary fault body according to the true and false fault judgment standard and fault distance to obtain fault distribution; The criteria for judging true or false faults are: the fault throw is greater than 20ms, and the fault throws of the upper and lower salt rock formations are equal; The fracture detection method includes one or more of an edge detection method, an ant body tracking method, a maximum likelihood attribute fracture detection method, and a frequency division body fusion display method.

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