A VSP precise layer calibration method and system based on ray theory

Abstract

The present invention provides a VSP precise layer calibration method and system based on ray theory, which belongs to the field of seismic data processing and interpretation in oil and gas exploration and development. The method establishes a seismic forward model through a seismic data observation system and logging data, obtains the VSP upgoing wave travel time error and the first arrival travel time error through the seismic forward model and the first arrival travel time picking, and then obtains the VSP precise two-way travel time through the VSP upgoing wave travel time error correction and the first arrival travel time correction, determines the time-depth relationship, and then realizes the VSP precise layer calibration. The present invention is more in line with the actual situation of underground strata, lays a foundation for precise layer calibration, can accurately calculate the VSP upgoing wave travel time error based on ray theory, has high calculation efficiency, and can obtain the accurate VSP two-way travel time through the travel time correction combined with the first arrival travel time picking, and determines the correct time-depth relationship, and then performs precise layer calibration to obtain accurate layer velocity.

Description

Technical Field

[0001] The invention belongs to the field of seismic data processing and interpretation in oil and gas exploration and development, and specifically relates to a VSP precise layer calibration method and system based on ray theory. Background Art

[0002] After investigating a large number of detectable documents and patents at home and abroad, and fully understanding and studying the software products of research institutions and geophysical companies, the existing technologies related to the present invention are summarized as follows:

[0003] Conventional VSP time-depth calibration technology does not fully consider the VSP time-depth relationship and ignores the difference between VSP time and imaging processing time. This method has little effect on the interpretation of simple horizontal strata, but is not suitable for complex structures. Conventional VSP assumes a horizontal layered medium model, but when faced with non-horizontal complex strata or structures, its time-depth calibration will have a large error, resulting in inaccurate horizon calibration, which seriously affects seismic interpretation.

[0004] At present, VSP layer calibration in seismic processing is mostly done manually. When there is an error between the layer obtained by VSP data and the actual position, manual adjustment is required to obtain the correct position. However, the manual adjustment method is labor-intensive and has a strong human subjective consciousness. It is easy to get non-unique results due to different personal experiences, and it is difficult to obtain accurate calibration results.

[0005] In recent years, with the development of oil and gas exploration, the requirements for detailed interpretation of complex oil and gas reservoirs have become increasingly higher. VSP technical means have been more widely used and have played an important role in oil and gas reservoir exploration and dynamic monitoring. More attention should also be paid to the processing and interpretation technology of VSP data. Summary of the invention

[0006] The purpose of the present invention is to solve the above-mentioned difficulties existing in the prior art, and to provide a VSP accurate horizon calibration method and system based on ray theory, to establish a seismic geological forward model according to the seismic wave propagation and observation mode, to solve the horizon error problem caused by non-horizontal strata through the horizon calibration correction method, and to obtain an accurate horizon calibration position.

[0007] The present invention is achieved through the following technical solutions:

[0008] A first aspect of the present invention provides a VSP precise layer calibration method based on ray theory, wherein the method establishes a seismic forward model through a seismic data observation system and logging data, obtains the VSP upgoing wave traveltime error and the first arrival traveltime error through the seismic forward model and first arrival traveltime picking, then obtains the VSP precise two-way traveltime through the VSP upgoing wave traveltime error correction and the first arrival traveltime correction, determines the time-depth relationship, and thereby realizes the VSP precise layer calibration.

[0009] A further improvement of the present invention is that the method comprises:

[0010] Step 1: Establish a seismic forward model based on the seismic data observation system and logging data;

[0011] Step 2: Calculate the precise upgoing wave travel time and VSP upgoing wave travel time according to the earthquake forward model;

[0012] Step 3: Using the precise up-going wave travel time t acc and VSP upgoing wave travel time t VSP Get the upgoing wave travel time error;

[0013] Step 4: First arrival picking to obtain first arrival travel time error;

[0014] Step 5: Obtain the VSP accurate two-way travel time based on the upgoing wave travel time error obtained in step 3 and the first arrival travel time error obtained in step 4;

[0015] Step 6: Use the VSP precise two-way travel time to obtain the correct time-depth relationship, and then perform precise layer calibration.

[0016] A further improvement of the present invention is that the operation of the first step includes:

[0017] Determine the relationship between source excitation and receiver receiving positions through the seismic data observation system;

[0018] Determine formation dip and velocity model using VSP data and logging data;

[0019] Establish an earthquake forward model.

[0020] A further improvement of the present invention is that the operation of the second step comprises:

[0021] The accurate upgoing wave travel time t is calculated using the following formula: acc and VSP upgoing wave travel time t VSP :

[0022] t acc =2H d / v (1)

[0023]

[0024] Among them, H d is the formation depth, v is the seismic wave propagation velocity, θ is the formation inclination, H r is the detector depth.

[0025] A further improvement of the present invention is that the operation of the third step includes:

[0026] The upgoing wave travel time error t is calculated using the following formula: error :

[0027]

[0028] Its time domain expression is:

[0029]

[0030] Among them, T d =2H d / v,t r =H r / v;

[0031] Converted to the depth domain, the layer calibration error H error for:

[0032]

[0033] A further improvement of the present invention is that the operation of the fourth step includes:

[0034] The energy ratio is calculated using the following formula:

[0035]

[0036] Where A(t) is the amplitude value of seismic data, T sta To select the start time of the time window, T mid is the middle time of the time window, T end The time window ends;

[0037] Find the time point with the largest energy ratio, which is the time when the seismic wave first arrives;

[0038] The first arrival travel time in the flat model VSP record is subtracted from the first arrival travel time in the tilt model VSP record to obtain the first arrival travel time error t efst .

[0039] A further improvement of the present invention is that the operation of the fifth step includes:

[0040] The VSP accurate round trip travel time t is calculated using the following formula: dext :

[0041] t dext =t dvsp -t error -t efst ,

[0042] Among them, t dvsp For VSP round trip.

[0043] A further improvement of the present invention is that the operation of the fifth step includes:

[0044] For a multi-layer geological model, steps 2 to 5 are repeated layer by layer from shallow to deep to obtain the VSP accurate two-way travel time of each layer.

[0045] A further improvement of the present invention is that the operation of the sixth step includes:

[0046] The VSP accurate two-way travel time is used to obtain the correct time-depth relationship, and then perform accurate layer calibration.

[0047] In a second aspect of the present invention, a VSP precise layer calibration system based on ray theory is provided, the system comprising: a memory, a processor, and a computer program stored in the memory, the computer program executing the following steps when executed by the processor:

[0048] Step 1: Establish a seismic forward model based on the seismic data observation system and logging data:

[0049] Step 2: Calculate the precise upgoing wave travel time and VSP upgoing wave travel time according to the earthquake forward model;

[0050] Step 3: Using the precise up-going wave travel time t acc and VSP upgoing wave travel time t VSP Get the upgoing wave travel time error;

[0051] Step 4: First arrival picking to obtain first arrival travel time error;

[0052] Step 5: Obtain the VSP accurate two-way travel time based on the upgoing wave travel time error obtained in step 3 and the first arrival travel time error obtained in step 4;

[0053] Step 6: Use the VSP precise two-way travel time to obtain the correct time-depth relationship, and then perform precise layer calibration.

[0054] Compared with the prior art, the present invention has the following beneficial effects: the present invention establishes a seismic forward model through a seismic data observation system and logging data, which is more in line with the actual situation of the underground strata, and lays a foundation for accurate stratigraphic calibration; based on ray theory, the VSP upgoing wave travel time error can be accurately calculated, and the calculation efficiency is high; combined with the first arrival travel time picking, the accurate VSP two-way travel time can be obtained through travel time correction, the correct time-depth relationship can be determined, and then accurate stratigraphic calibration can be performed to obtain accurate layer velocity. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A flowchart of the steps of the method of the present invention;

[0056] Figure 2-1 Schematic diagram of the flat layer model in the Marmours model;

[0057] Figure 2-2 Schematic diagram of the oblique layer model in the Marmours model;

[0058] Figure 3-1 VSP forward modeling records of flat layer models;

[0059] Figure 3-2 VSP forward modeling records of the oblique layer model;

[0060] Figure 4-1 Schematic diagram of VSP horizon calibration before correction;

[0061] Figure 4-2 Schematic diagram of VSP layer calibration after correction. DETAILED DESCRIPTION

[0062] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0063] The invention provides a VSP precise horizon calibration method based on ray theory, wherein a seismic geological model is established through a seismic data observation system and logging data, and a VSP upgoing wave travel time error and a first arrival travel time error are calculated through a forward model and first arrival travel time picking, with high calculation efficiency and accuracy, and then accurate VSP two-way travel time is obtained through VSP upgoing wave travel time error correction and first arrival travel time correction, and the time-depth relationship is determined, so as to perform VSP horizon calibration.

[0064] The embodiments of the method of the present invention are as follows:

[0065] [Example 1]

[0066] like Figure 1 As shown, the method includes:

[0067] Step 1: Establish a seismic forward model based on the seismic data observation system and logging data:

[0068] The relationship between the source excitation and the detector receiving position can be determined through the seismic data observation system. The formation dip and velocity model can be determined using VSP data and logging data, thereby establishing a seismic forward model. The method for establishing a seismic forward model can be implemented using existing technology and will not be repeated here.

[0069] Step 2: According to the earthquake forward model, the precise upgoing wave travel time t is calculated by the ray minimum travel time method. acc and VSP upgoing wave travel time t VSP ,

[0070] t acc =2H d / v (1)

[0071]

[0072] Among them, H d is the formation depth, v is the seismic wave propagation velocity, θ is the formation inclination, H r is the detector depth, and the values ​​of these parameters are obtained from VSP logging data.

[0073] Step 3: When the stratum is non-horizontal, the error of the upgoing wave travel time is the error of calculating the VSP horizon calibration of the inclined stratum. The upgoing wave travel time error t error for:

[0074]

[0075] Its time domain expression is:

[0076]

[0077] Among them, T d =2H d / v,t r =H r / v

[0078] Converted to the depth domain, the layer calibration error H error for:

[0079]

[0080] Step 4: First arrival picking: Use the energy ratio method to pick up the first arrival of seismic waves. The formula for energy ratio is:

[0081]

[0082] Where A(t) is the amplitude value of seismic data, T sta To select the start time of the time window, T mid is the middle time of the time window, Tend is the end time of the time window, and the time point with the largest energy ratio is the first arrival travel time of the seismic wave (i.e., multiple ERs in the time window are calculated using formula (6), and then they are sorted to find the largest ER, which corresponds to the first arrival travel time). The energy ratio method is used to pick up the first arrival travel time of the flat model VSP record and the first arrival travel time of the tilt model VSP record respectively, and then the first arrival travel time of the flat model VSP record picked up is subtracted from the first arrival travel time of the tilt model VSP record to obtain the first arrival travel time error t efst .

[0083] Step 5: Calculate the VSP precise two-way travel time based on the up-wave travel time error obtained in step 3 and the first-arrival travel time error obtained in step 4. Specifically, the precise two-way travel time is obtained by dividing the VSP two-way travel time by the up-wave travel time error and the first-arrival travel time error:

[0084] t dext =t dvsp -t error -t efst ,

[0085] Among them, t dext is the precise two-way travel time, t dvsp For VSP round trip.

[0086] For multi-layer geological models, it is necessary to calculate the travel time difference layer by layer from shallow to deep (that is, correct the travel time layer by layer, repeat steps 2 to 5 for each layer), and then obtain the accurate two-way travel time (after correcting each layer, the VSP accurate two-way travel time of all strata can be obtained).

[0087] Step 6: Use the VSP precise two-way travel time to obtain the correct time-depth relationship (specifically, due to the correspondence between the travel time of seismic waves and the depth, the VSP data has a known accurate depth, and the correct time is obtained after the travel time error is corrected, thus establishing an accurate time-depth relationship), and then perform precise layer calibration (layer calibration links the time of the earthquake with the geological depth, and obtaining an accurate time-depth relationship establishes an accurate correspondence between the earthquake time and the geological depth. Because after the travel time correction, the earthquake recording time is accurate, and the time correction is equivalent to calibration).

[0088] The method further comprises: calculating the accurate layer velocity by using the depth difference between formation interfaces (VSP logging contains accurate depth information) and the first arrival travel time difference (obtained by the same method as in the fourth step, where the time difference is the time difference between two formation interfaces):

[0089]

[0090] The present invention also provides a VSP precise layer calibration system based on ray theory, and the embodiments of the system are as follows:

[0091] [Example 2]

[0092] The system comprises: a memory, a processor, and a computer program stored in the memory, wherein the computer program executes the following steps when executed by the processor:

[0093] Step 1: Establish a seismic forward model based on the seismic data observation system and logging data:

[0094] Step 2: Calculate the precise upgoing wave travel time and VSP upgoing wave travel time according to the earthquake forward model;

[0095] Step 3: Using the precise up-going wave travel time t acc and VSP upgoing wave travel time t VSP Get the upgoing wave travel time error;

[0096] Step 4: First arrival picking to obtain first arrival travel time error;

[0097] Step 5: Obtain the VSP precise two-way traveltime based on the upgoing wave traveltime error obtained in step 3 and the first arrival traveltime error obtained in step 4.

[0098] Step 6: Use the VSP precise two-way travel time to obtain the correct time-depth relationship, and then perform precise layer calibration.

[0099] The first step includes:

[0100] Determine the relationship between source excitation and receiver receiving positions through the seismic data observation system;

[0101] Determine formation dip and velocity model using VSP data and logging data;

[0102] Establish an earthquake forward model.

[0103] The second step includes:

[0104] The accurate upgoing wave travel time t is calculated using the following formula: acc and VSP upgoing wave travel time t VSP :

[0105] t acc =2H d / v (1)

[0106]

[0107] Among them, H dis the formation depth, v is the seismic wave propagation velocity, θ is the formation inclination, H r is the detector depth, and the values ​​of these parameters are obtained from VSP logging data.

[0108] The operation of the third step includes:

[0109] The upgoing wave travel time error t is calculated using the following formula: error :

[0110]

[0111] Its time domain expression is:

[0112]

[0113] Among them, T d =2H d / v,t r =H r / v.

[0114] Converted to the depth domain, the layer calibration error H error for:

[0115]

[0116] The fourth step includes:

[0117] The energy ratio is calculated using the following formula:

[0118]

[0119] Where A(t) is the amplitude value of seismic data, T sta To select the start time of the time window, T mid is the middle time of the time window, T end The time window ends;

[0120] Find the time point with the largest energy ratio, which is the time when the seismic wave first arrives;

[0121] The first arrival travel time error t is obtained by subtracting the first arrival travel time in the flat model VSP record obtained by picking and averaging the first arrival travel time in the tilt model VSP record. efst .

[0122] The operation of the fifth step includes:

[0123] The VSP accurate round trip travel time t is calculated using the following formula: dext :

[0124] t dext =t dvsp -t error -tefst ,

[0125] Among them, t dvsp For VSP round trip.

[0126] The operation of the fifth step includes:

[0127] For a multi-layer geological model, steps 2 to 5 are repeated layer by layer from shallow to deep to obtain the VSP accurate two-way travel time of each layer.

[0128] The operation of the sixth step includes:

[0129] The VSP accurate two-way travel time is used to obtain the correct time-depth relationship, and then perform accurate layer calibration.

[0130] The embodiments of the present invention are as follows:

[0131] [Example 3]

[0132] Select the Marmousi model, as shown in the diagram Figure 2-1 and Figure 2-2 As shown, Figure 2-1 is the flat layer model established based on the model data at the well location (black vertical line). Figure 2-2 It is a practical inclined layer model.

[0133] use Figure 2-1 and Figure 2-2 The two models in the VSP seismic wave forward simulation are performed separately, and the forward modeling records are as follows Figure 3-1 and Figure 3-2 As shown, Figure 3-1 is the VSP earthquake forward model record of the flat layer model, Figure 3-2 It is the VSP seismic forward modeling record of the actual model. According to the interface dip, the up-going wave time error is obtained through step 3, and the two-way travel time is obtained by using the principle of first arrival picking of the energy ratio method in step 4. In actual use, VSP data is used as the basis for layer calibration. When the model has a certain dip, the layer calibration obtained by VSP will have errors, such as Figure 4-1 shown.

[0134] The result of VSP data layer calibration by the method proposed in this invention is shown in FIG4 . Figure 4-1 This is the result of the layer calibration without considering the travel time difference. The VSP layer has a large deviation. Figure 4-2 This is the layer calibration after the travel time difference correction. The layer calibration position obtained by considering the travel time difference according to the method of the present invention is accurate, which proves the accuracy of the method.

[0135] The present invention belongs to the field of seismic data processing and interpretation in oil and gas exploration and development, and is mainly used in VSP data processing and interpretation technology to provide reliable data for seismic imaging and structural interpretation.

[0136] The present invention has good application prospects in oil and gas exploration and development. First, in terms of technology, the present invention is based on ray theory and establishes a seismic geological model from a practical perspective, which has good accuracy; secondly, in terms of production application, the present invention can be effectively applied to actual production, providing good technical support for VSP data processing and interpretation, solving the problem of VSP data layer calibration errors in complex structural areas, and has good application prospects, which can provide strong technical support for oil and gas exploration and development.

[0137] Finally, it should be explained that the above technical solution is only one implementation method of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific implementation method of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A VSP accurate horizon calibration method based on ray theory, characterized by: The method establishes a seismic forward model through a seismic data observation system and logging data, obtains VSP upgoing wave travel time error and first arrival travel time error through the seismic forward model and first arrival travel time picking, then obtains VSP precise two-way travel time through VSP upgoing wave travel time error correction and first arrival travel time correction, determines the time-depth relationship, and thus realizes VSP precise layer calibration; The method comprises: Step 1: Establish a seismic forward model based on the seismic data observation system and logging data: Step 2: Calculate the precise upgoing wave travel time and VSP upgoing wave travel time according to the earthquake forward model; Step 3: Using the precise up-going wave travel time t acc and VSP upgoing wave travel time t VSP Get the upgoing wave travel time error; Step 4: First arrival picking to obtain first arrival travel time error; Step 5: Obtain the VSP accurate two-way travel time based on the upgoing wave travel time error obtained in step 3 and the first arrival travel time error obtained in step 4; Step 6: Use the VSP precise two-way travel time to obtain the correct time-depth relationship, and then perform precise layer calibration.

2. The VSP precise horizon calibration method based on ray theory according to claim 1 is characterized in that: The operations of the first step include: Determine the relationship between source excitation and receiver receiving positions through the seismic data observation system; Determine formation dip and velocity model using VSP data and logging data; Establish an earthquake forward model.

3. The VSP precise horizon calibration method based on ray theory according to claim 2 is characterized by: The second step includes: The accurate upgoing wave travel time t is calculated using the following formula: acc and VSP upgoing wave travel time t VSP : t acc =2H d / v(1) Among them, H d is the formation depth, v is the seismic wave propagation velocity, θ is the formation inclination, H r is the detector depth.

4. The VSP precise horizon calibration method based on ray theory according to claim 3 is characterized by: The operation of the third step includes: The upgoing wave travel time error t is calculated using the following formula: error : Its time domain expression is: Among them, T d =2H d / v,t r =H r / v Converted to the depth domain, the layer calibration error H error for:

5. The VSP precise horizon calibration method based on ray theory according to claim 4 is characterized by: The fourth step includes: The energy ratio is calculated using the following formula: Where A(t) is the amplitude value of seismic data, T sta To select the start time of the time window, T mid is the middle time of the time window, T end The time window ends; Find the time point with the largest energy ratio, which is when the seismic wave first arrives and travels; The first arrival travel time in the flat model VSP record is subtracted from the first arrival travel time in the tilt model VSP record to obtain the first arrival travel time error t efst .

6. The VSP precise horizon calibration method based on ray theory according to claim 5 is characterized by: The operation of the fifth step includes: The VSP accurate round trip travel time t is calculated using the following formula: dext : t dext =t dvsp -t error -t efst , Among them, t dvsp For VSP round trip.

7. The VSP precise horizon calibration method based on ray theory according to claim 6 is characterized by: The operation of the fifth step includes: For a multi-layer geological model, steps 2 to 5 are repeated layer by layer from shallow to deep to obtain the VSP accurate two-way travel time of each layer.

8. A VSP accurate layer calibration system based on ray theory, characterized by: The system comprises: a memory, a processor, and a computer program stored in the memory, wherein the computer program executes the following steps when executed by the processor: Step 1: Establish a seismic forward model based on the seismic data observation system and logging data; Step 2: Calculate the precise upgoing wave travel time and VSP upgoing wave travel time according to the earthquake forward model; Step 3: Using the precise up-going wave travel time t acc and VSP upgoing wave travel time t VSP Get the upgoing wave travel time error; Step 4: First arrival picking to obtain first arrival travel time error; Step 5: Obtain the VSP accurate two-way travel time based on the upgoing wave travel time error obtained in step 3 and the first arrival travel time error obtained in step 4; Step 6: Use the VSP precise two-way travel time to obtain the correct time-depth relationship, and then perform precise layer calibration.

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