A method for identifying a stratigraphic pinchout line based on lithofacies and seismic facies

Abstract

The application discloses a method for identifying a stratum pinch-out line based on lithofacies and seismic facies, which comprises the following steps: (1) conducting stratum comparison and analysis through drilling and well connection, analyzing the lithofacies and thickness variation characteristics of the stratum near the pinch-out line, and establishing a two-dimensional geological model; (2) analyzing well logging data and actual seismic data of the drilled well to obtain the acoustic characteristics, density characteristics, seismic wavelets and seismic main frequencies of different lithofacies; (3) based on the two-dimensional geological model obtained in the step (2) and the stratum thickness variation characteristics, acoustic characteristics, density characteristics, seismic wavelets and seismic main frequencies of different lithofacies obtained in the steps (1), (3) and (4), conducting seismic simulation; (4) superimposing the two-dimensional geological model and the seismic profile obtained through seismic simulation to analyze the variation law of the seismic amplitude energy and geometric shape caused by the continuous thinning of the stratum, the pinch-out and the lithofacies and thickness variation of the directly contacted overlying stratum; and (5) applying the obtained variation law to the interpretation work of three-dimensional seismic data to identify the stratum pinch-out line.

Description

Technical Field

[0001] This invention relates to the field of petroleum and natural gas engineering technology, and in particular to a method for identifying stratigraphic pinch-out lines based on lithofacies and seismic facies. Background Technology

[0002] Determining the pinch-out location is of great significance for establishing the stratigraphic trap boundary and improving the success rate of gas reservoir exploration. However, when the gas-producing and exploration strata are buried at a large depth (generally between 5500-6500 meters), the seismic reflection energy is weak, the resolution is low, or the stratigraphic lithofacies vary greatly, it is easy to make it difficult to accurately locate the pinch-out location in the interpretation of seismic data. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings in the prior art and provide a method for identifying stratigraphic pinch-out lines based on lithofacies and seismic facies.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] A method for identifying stratigraphic pinch-out lines based on lithofacies and seismic facies includes the following steps:

[0006] Step 1: Conduct stratigraphic correlation analysis through drilling and well interconnection to analyze the upper and lower contact relationships and stratigraphic thickness variation characteristics of different lithofacies of the overlying and underlying strata within the stratigraphic thickness range of 0-80m.

[0007] Step 2: Based on the stratigraphic correlation analysis results from Step 1, establish a two-dimensional geological model;

[0008] Step 3: Analyze the completed drilling and logging data, and statistically analyze the maximum, average, and minimum values ​​of the sonic and density curves of different rock facies within the formation thickness range of 0-80m to obtain the sonic and density characteristics of different rock facies.

[0009] Step 4: Analyze actual seismic data to obtain seismic wavelets and seismic dominant frequencies;

[0010] Step 5: Based on the two-dimensional geological model obtained in Step 2, and the stratigraphic thickness variation characteristics, acoustic characteristics, density characteristics, seismic wavelets, and seismic dominant frequencies of different lithofacies obtained in Steps 1, 3, and 4, perform seismic simulation;

[0011] Step Six: Overlay the two-dimensional geological model established in Step Two with the seismic profile obtained from the seismic simulation in Step Five, and analyze the variation law of seismic amplitude energy and geometric shape caused by the continuous thinning and pinching of strata and the changes in lithofacies and thickness of the strata in direct contact with the overlying strata.

[0012] Step Seven: Apply the variation patterns obtained in Step Six to the interpretation of 3D seismic data to identify stratigraphic pinch-out lines. During interpretation, pay attention to the overall trend of change, eliminate complexities caused by local factors such as faults or seismic data processing traps, and look for patterns in the changes to determine the distribution of stratigraphic pinch-out lines.

[0013] Preferably, in step four, when analyzing actual seismic data, analysis software is used to analyze the spectrum of strata with a thickness of 0-80m and their overlying and underlying strata.

[0014] Preferably, in step four, the analysis software includes LandMark, Jason, Geocyber, GeoScope, and SMI.

[0015] Preferably, in step five, earthquake simulation is performed using earthquake simulation software, including Tesseral and SeisWave.

[0016] Preferably, in step six, the seismic profiles used for overlay analysis are similar to the actual seismic data in terms of geometry, frequency, and amplitude energy.

[0017] Preferably, in step seven, when applying the obtained variation patterns to the interpretation of three-dimensional seismic data, this includes using the variation patterns of seismic amplitude energy to identify stratigraphic pinch-out lines.

[0018] Preferably, in step seven, when applying the obtained variation patterns to the interpretation of three-dimensional seismic data, this includes using the combined variation patterns of seismic amplitude energy and geometric shape to identify stratigraphic pinch-out lines.

[0019] Preferably, step one can be implemented at any time before step five, and step two can be implemented at any time after step one and before step five.

[0020] Preferably, step three can be performed at any time before step five.

[0021] Preferably, step four can be performed at any time before step five.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The technology of this invention can determine lithofacies changes through stratigraphic correlation, establish the correlation between lithofacies and seismic facies using forward modeling, clarify the distribution characteristics of stratigraphic pinch-out lines, identify stratigraphic pinch-out lines, and establish stratigraphic trap boundaries, providing effective support for the exploration of different zones, especially slope zone structures-stratigraphy and stratigraphic traps. Attached image description:

[0024] Figure 1 This is a flowchart illustrating a method for identifying stratigraphic pinch-out lines based on lithofacies and seismic facies, as described in Embodiment 1 of the present invention.

[0025] Figure 2 This is a schematic diagram showing the upper and lower contact relationships and changes in stratum thickness between the strata with different rock facies in the overlying and underlying strata within the range of 0-80m, as described in this invention.

[0026] Figure 3 This is a schematic diagram of the two-dimensional geological model described in this invention.

[0027] Figure 4 This is a schematic diagram illustrating the identification of stratigraphic pinch-out lines using summarized variation patterns as described in this invention.

[0028] Figure 5 This is a flowchart illustrating a method for identifying stratigraphic pinch-out lines based on lithofacies and seismic facies, as described in Embodiment 2 of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0030] Example 1

[0031] like Figure 1 As shown, a method for identifying stratigraphic pinch-out lines based on lithofacies and seismic facies includes the following steps:

[0032] Step 1: Conduct stratigraphic correlation analysis through drilling and well interconnection to analyze the upper and lower contact relationships and stratigraphic thickness variation characteristics of different lithofacies in the 0-80m stratigraphic thickness range with the overlying and underlying strata. Figure 2 As shown;

[0033] Step Two: Based on the stratigraphic correlation analysis results from Step One, establish a two-dimensional geological model, such as... Figure 3 As shown;

[0034] Step 3: Analyze the completed drilling and logging data, and statistically analyze the maximum, average, and minimum values ​​of the sonic and density curves of different rock facies within the formation thickness range of 0-80m to obtain the sonic and density characteristics of different rock facies.

[0035] Step 4: Analyze actual seismic data. Use analysis software (LandMark, GeoScope, Jason, Geocyber, SMI, etc.) to analyze the spectrum of strata with a thickness of 0-80m and the overlying and underlying strata to obtain seismic wavelets and seismic main frequencies.

[0036] Step 5: Input the two-dimensional geological model obtained in Step 2 into the earthquake simulation software (Tesseral, SeisWave, etc.), assign values ​​to the two-dimensional geological model according to the stratigraphic thickness variation characteristics, acoustic characteristics, density characteristics, seismic wavelet, and seismic dominant frequency of different lithofacies obtained in Steps 1, 3, and 4, and perform earthquake simulation on the two-dimensional geological model through the earthquake simulation software;

[0037] Step Six: Overlay the two-dimensional geological model established in Step Two with the seismic profile obtained from the seismic simulation in Step Five. The seismic profile obtained from the overlay analysis is similar to the actual seismic data in terms of geometric shape, frequency, and amplitude energy. Analyze the variation law of seismic amplitude energy and geometric shape caused by the continuous thinning and pinching of strata and the changes in lithofacies and thickness of the strata in direct contact with the overlying strata.

[0038] Step Seven: Apply the variation patterns obtained in Step Six to the interpretation of 3D seismic data to identify stratigraphic pinch-out lines, such as... Figure 4 As shown, this includes identifying stratigraphic pinch-out lines by utilizing the variation patterns of seismic amplitude energy; and identifying stratigraphic pinch-out lines by utilizing the combined variation patterns of seismic amplitude energy and geometric shapes.

[0039] Example 2

[0040] like Figure 5 As shown, a method for identifying stratigraphic pinch-out lines based on lithofacies and seismic facies includes the following steps:

[0041] Step 1: Analyze the completed drilling and logging data, and statistically analyze the maximum, average, and minimum values ​​of the sonic and density curves of different rock facies within the formation thickness range of 0-80m to obtain the sonic and density characteristics of different rock facies.

[0042] Step 2: Analyze actual seismic data and use analysis software (LandMark, Jason, Geocyber, GeoScope, SMI, etc.) to analyze the spectrum of strata with a thickness of 0-80m and the overlying and underlying strata to obtain seismic wavelets and seismic main frequencies.

[0043] Step 3: Conduct stratigraphic correlation analysis through drilling and well interconnection to analyze the upper and lower contact relationships and stratigraphic thickness variation characteristics of different lithofacies in the 0-80m stratigraphic thickness range with the overlying and underlying strata. Figure 2 As shown;

[0044] Step 4: Based on the stratigraphic correlation analysis results from Step 3, establish a two-dimensional geological model, such as... Figure 3 As shown;

[0045] Step 5: Input the two-dimensional geological model obtained in Step 4 into earthquake simulation software (Tesseral, SeisWave, etc.), assign values ​​to the two-dimensional geological model according to the acoustic characteristics, density characteristics, seismic wavelet, seismic dominant frequency, and stratigraphic thickness variation characteristics of different lithofacies obtained in Steps 1, 2, and 3, and perform earthquake simulation on the two-dimensional geological model through earthquake simulation software;

[0046] Step Six: Overlay the two-dimensional geological model established in Step Four with the seismic profile obtained from the seismic simulation in Step Five. The seismic profile obtained from the overlay analysis is similar to the actual seismic data in terms of geometric shape, frequency, and amplitude energy. Analyze the changes in seismic amplitude energy and geometric shape caused by the continuous thinning and pinching out of the strata and the changes in the lithofacies and thickness of the strata in direct contact with the overlying strata.

[0047] Step Seven: Apply the variation patterns obtained in Step Six to the interpretation of 3D seismic data to identify stratigraphic pinch-out lines, such as... Figure 4 As shown, this includes identifying stratigraphic pinch-out lines by utilizing the variation patterns of seismic amplitude energy; and identifying stratigraphic pinch-out lines by utilizing the combined variation patterns of seismic amplitude energy and geometric shapes.

[0048] The following example, using a stratigraphic section in the Sichuan Basin, further illustrates how to summarize the patterns of change and guide the interpretation of 3D seismic data:

[0049] Analysis revealed that the variation in seismic profiles within the 0-80m stratigraphic thickness range can be divided into two parts. Firstly, the variation in amplitude energy at the reflection interface between the top clastic and carbonate rocks is evident. When a certain stratigraphic segment is greater than one-quarter of the wavelength (approximately 40 meters), its amplitude energy is weak; when it is between one-quarter and one-eighth of the wavelength, its amplitude energy is strong; when it is less than one-eighth of the wavelength, its amplitude energy reverts to weak; and when a certain stratigraphic segment pinches out, its amplitude energy becomes medium-strong. Overall, it exhibits a weak-strong-weak-medium-strong variation pattern. However, due to the influence of the overlying carbonate strata in the area, the weak amplitude characteristics of a certain stratigraphic segment greater than one-quarter of the wavelength show complex variations. But from a certain stratigraphic segment equal to one-quarter of the wavelength... The strong-weak-medium intensity variation characteristics of the wavelength until pinch-out are relatively stable, and therefore can be used as one of the bases for judging the pinch-out line. On the other hand, it is reflected in the combination of geometric shape and amplitude energy of the seismic reflection layer below the interface between clastic rocks and carbonate rocks. When a certain stratum is larger than a quarter wavelength, it is affected by the overlying carbonate strata (a certain limestone section), and the earthquake generally shows a broad trough, a double-peak composite phase characteristic, and medium-strong amplitude energy. As the limestone section pinches out, the composite phase gradually transitions. When the limestone section pinches out, the broad trough gradually narrows, and the characteristic becomes a single trough. As the thickness of the strata in a certain stratum decreases until pinch-out, the trough becomes narrower and narrower, and the energy changes from strong to weak. When a weak trough meets a medium-strong trough, the stratum in that stratum is near the pinch-out line.

[0050] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described herein. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present invention, and all technical solutions and improvements that do not depart from the spirit and scope of the invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for identifying a stratigraphic pinchout line based on lithofacies and seismic facies, characterized in that, The method comprises the following steps: Step 1: carry out formation correlation analysis by drilling and well tie, analyze the upper and lower contact relationship of different lithofacies and the formation thickness variation characteristics in the range of 0-80m; Step 2: establish a two-dimensional geological model according to the formation correlation analysis result of step 1; Step 3: analyze the well logging data of the drilled well, and count the maximum value, average value and minimum value of the sonic curve and density curve of different lithofacies in the range of 0-80m to obtain the sonic characteristics and density characteristics of different lithofacies; Step 4: analyze the actual seismic data to obtain the seismic wavelet and seismic main frequency; when analyzing the actual seismic data, the spectrum of the formation thickness in the range of 0-80m and the overlying and underlying formations is analyzed by using an analysis software; Step 5: based on the two-dimensional geological model obtained in step 2, and the formation thickness variation characteristics, sonic characteristics, density characteristics, seismic wavelet and seismic main frequency of different lithofacies obtained in steps 1, 3 and 4, carry out seismic simulation; Step 6: superimpose the two-dimensional geological model established in step 2 and the seismic profile obtained in step 5 to carry out superimposition analysis; the superimposed seismic profile is similar to the actual seismic data in geometric shape, frequency and amplitude energy; analyze the variation law of the seismic amplitude energy and geometric shape caused by the continuous thinning and pinch-out of the formation and the change of the lithofacies and thickness of the overlying directly contacted formation; the variation law comprises: the variation of the amplitude energy on the reflection interface between the top clastic rock and the carbonate rock: when the formation is greater than one fourth of the wavelength, the amplitude energy is weak; when it is equal to one fourth to one eighth of the wavelength, the amplitude energy is strong; when it is less than one eighth of the wavelength, the amplitude energy turns to be weak; when the formation pinches out, the amplitude energy turns to be medium strong, and the overall variation law is weak-strong-weak-medium strong; the combined variation of the seismic reflection layer below the interface between the clastic rock and the carbonate rock in geometric shape and amplitude energy: when the formation is greater than one fourth of the wavelength, the seismic profile is generally wide trough with double peak complex phase characteristics and medium strong amplitude energy due to the influence of the overlying carbonate rock formation; with the pinch-out of the overlying carbonate rock formation, the complex phase gradually transitions; when the overlying carbonate rock formation pinches out, the wide trough gradually narrows and the characteristics change to single trough; with the thinning of the formation thickness until the pinch-out, the trough becomes narrower and the energy changes from strong to weak; when the weak trough meets the medium strong trough, the formation is near the pinch-out line; Step 7: apply the variation law obtained in step 6 to the interpretation work of the three-dimensional seismic data to identify the pinch-out line of the formation.

2. The method according to claim 1, characterized in that, In step 4, the analysis software comprises LandMark, Jason, GeoScope, Geocyber and SMI.

3. The method according to claim 1, characterized in that, In step 5, the seismic simulation is carried out by using a seismic simulation software, and the seismic simulation software comprises Tesseral and SeisWave.

4. The method according to claim 1, characterized in that, In step 7, when the obtained variation law is applied to the interpretation work of the three-dimensional seismic data, the variation law of the seismic amplitude energy is used to identify the pinch-out line of the formation.

5. The method according to claim 1, wherein, The obtained variation law is applied to the interpretation of three-dimensional seismic data in step seven, including identifying the pinch-out line of the stratum by using the combined variation law of seismic amplitude energy and geometric shape.

6. The method according to any one of claims 1-5, wherein, The step one can be implemented at any time before the implementation of the step five, and the step two can be implemented at any time after the implementation of the step one and before the implementation of the step five.

7. The method according to any one of claims 1-5, wherein, The step three can be implemented at any time before the implementation of the step five.

8. The method according to any one of claims 1-5, wherein, The step four can be implemented at any time before the implementation of the step five. The step three can be implemented at any time before the implementation of the step five. The step four can be implemented at any time before the implementation of the step five.

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