A method for mapping the fans of sandstone bodies in different stages

Abstract

The present invention relates to the field of seismic interpretation, and in particular to a method for mapping the fans of each stage of a sandy conglomerate body. The method comprises the following steps: performing a detailed interpretation of the sandy conglomerate fan to clarify the development stage of the fan; determining the layer velocity of the actual drilling of the fans of each stage of the sandy conglomerate body; calculating the top depth of the fans of each stage, and drawing a small range of fan top surface structural map outside the longitudinal overlap range of the fans of each stage and the previous stage; calculating the thickness of the fans of each stage, and drawing a thickness contour map of the fans of each stage; respectively calculating the depth value of the local fans within the longitudinal overlap range of the fans of each stage and the previous stage, and drawing a local range of fan top surface structural map within the longitudinal overlap range of the fans of each stage and the previous stage; drawing a complete depth top surface structural map of the fans of each stage. The method of the present invention can eliminate structural illusions such as structural high point offset caused by the direct conversion of the regional velocity curve caused by the fan root pull-up caused by the sandy conglomerate high-speed body, and changes in the occurrence of the fans.

Description

Technical Field

[0001] The invention relates to the field of seismic interpretation, and in particular to a method for mapping fans of gravel bodies at different stages. Background Art

[0002] The northern steep slope zone of the Dongying Sag in the Jiyang Depression is a steep slope structural zone controlled by the Chennan shovel-shaped fan-shaped boundary fault. From west to east, many ancient gullies have developed, which are the main channels for material supply. Along these large and small valleys, a large amount of debris is carried by rivers into the lake through cliffs, forming a complete or incomplete sandy conglomerate sedimentary sequence such as alluvial fans, underwater fans, and fan deltas in space. Vertically, the fans formed in different periods gradually retreat from old to new and are stacked in sequence. The direction of migration of the structural high points of the fans in each period is the direction of material source. In the plane, the phase belts of the fans in each period gradually migrated toward the uplift direction, and vertically from bottom to top, they are fan root-fan middle-fan end, forming a vertical sequence that becomes thinner and thinner upward. The sandy conglomerate oil reservoirs are widely developed in the steep slope zone, which is an important exploration target for increasing reserves and production in Shengli Oilfield.

[0003] With the gradual deepening of the exploration of sandy conglomerate bodies, the geological understanding of the sandy conglomerate bodies has gradually deepened, forming a series of exploration understandings such as ditch-fan correspondence, fan root sealing, reservoirs between fans, and superposition and connection.

[0004] In recent years, with the deepening of geological analysis and the introduction of geophysical exploration technologies such as three-dimensional forward modeling, it has been found that there are "structural illusions" in the time domain seismic data of the conglomerate body: the forward fans stacked along the bedrock surface are actually caused by the fan root pull-up phenomenon caused by the overlying high-speed conglomerate body, and are not the real occurrence. The real occurrence of the conglomerate body may be back-tilted or reversed. Therefore, according to the previous mapping method, the mapping of the conglomerate body fan will cause inaccurate reflection of the real structural high points of the fan body and unequal occurrence. In order to truly reflect the structure of the conglomerate fan body, some people have proposed that the variable speed mapping of the conglomerate body should be carried out by time-to-depth conversion to eliminate the structural depth error caused by the velocity trap of the conglomerate body, but variable speed mapping requires the establishment of a high-precision three-dimensional velocity model, which is difficult to achieve in actual operation. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for mapping the fans of sandstone bodies at various stages. The method of the present invention is simple to operate, accurate and reliable, can eliminate the false occurrence generated by directly converting the regional velocity curve at the fan root position, and solve the problem of structural high point offset.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for mapping the fans of a sandstone body at each stage, which comprises the following steps:

[0008] Step 1. Conduct detailed interpretation of the sandstone fan and clarify the development stages of the fan;

[0009] Step 2. Determine the interval velocity of each sector of the gravel body during actual drilling;

[0010] Step 3. Calculate the top depth of each phase of the fan body, and draw a small range of fan body top surface structural diagram outside the longitudinal overlap range of each phase of the fan body and the previous phase of the fan body;

[0011] Step 4. Calculate the thickness of the fan body in each period and draw a contour map of the thickness of the fan body in each period;

[0012] Step 5. Calculate the depth value of the local fan body in the longitudinal overlap range of each period of fan body and the previous period of fan body respectively, and draw the fan body top surface structure diagram of the local range of the longitudinal overlap range of each period of fan body and the previous period of fan body;

[0013] Step 6. Draw the complete depth top surface structure map of each period of the fan.

[0014] Furthermore, in step 1, the seismic reflection characteristics of the conglomerate fan are first clarified by well-seismic calibration using actual drilling and 3D seismic data, and then detailed interpretation and tracking of the fan stages are carried out to clarify the development stages of the conglomerate body.

[0015] Furthermore, in step 2, sampling statistics are carried out based on the logging data of the sectors of each period corresponding to the actual drilling of the sandstone and conglomerate body calibrated in step 1 to determine the layer velocity of the sectors of each period.

[0016] Furthermore, in step 3, the top structural depth of each sector of the gravel body is calculated using the regional velocity curve, and the depth error statistics between the structural map of the sector 1 and the actual drilling are used to determine the correction amount, which is used to correct the top structural maps of the remaining sectors, to obtain the top structural maps of the small-scale sectors with real depth outside the longitudinal overlap range of each sector and the previous sector.

[0017] Further, in step 4, firstly, the formula Δt is entered using the travel times of each sector n =t n+1 -t n Calculate the time length of each sector and draw a diagram of the time length of each sector; then substitute the sector layer velocity of each sector into the formula ΔH n =Δt n *V n Convert it into the actual thickness of the fan body in each period to form the thickness contour map of the fan body in each period.

[0018] Furthermore, in step 5, the thickness accumulation method is used to calculate the depth of the fan body of each period in the longitudinal overlap range with the fan body of the previous period, and the top surface structural depth of the fan body of period 1 and the thickness of the fan bodies of each period are successively accumulated, that is, Hn =H1+ΔH1+ΔH2+……+ΔH n-1 , the fan depths of the 2nd, 3rd, ..., nth period fans overlapping with the previous period fans are obtained in turn and formed into the corresponding local range top surface structure map.

[0019] Furthermore, in step 6, the local top surface structural map of each period fan obtained in step 5 and the small top surface structural map of each period fan obtained in step 3 are spliced ​​to form the complete real depth top surface structural map of each period fan.

[0020] Furthermore, when the fan interpretation ranges of the nth period and the n-1th period at the fan root position are inconsistent, the values ​​are calculated and mapped according to the nth period fan range.

[0021] Furthermore, when the fan range of the nth period at the fan end position is larger than the fan range of the n-1th period, the range exceeding the n-1th period can be mapped using the regional velocity curve and depth correction can be performed using actual drilling. When the fan range of the nth period at the fan end position is smaller than the fan range of the n-1th period, the thickness is accumulated according to the nth period fan range, the depth is calculated and mapped by correction using actual drilling.

[0022] The method for mapping the fans of each period of the conglomerate body described in the present invention is to carry out statistics of the actual drilling layer velocity of each period of the conglomerate body on the basis of clarifying the development period of the conglomerate fan body through comprehensive analysis and well seismic data, calculate the structural depth of the top surface of the conglomerate body using the regional velocity curve, and calculate the top surface depth of the deeper period of the fan body by accumulating the thickness of the fan body of a single period layer by layer to form the structural map of the top surface of the conglomerate body of each period. The real depth of the top surface of the conglomerate body of each period of the conglomerate body is calculated based on the method of accumulating the thickness of the fan body of each period layer by layer to form the structural map of the top surface of the conglomerate body of each period.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The method of the invention can eliminate structural illusions such as structural high point offset caused by direct conversion of regional velocity curves due to fan root pull-up caused by high-speed bodies of sandstone and conglomerate, and changes in fan body attitude. The invention provides a simple, easy, accurate and reliable mapping method for mapping fans of various stages of conglomerate bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a flow chart of the method for identifying inter-fans of a sandstone body according to Example 1 of the present invention;

[0027] Figure 2 It is a longitudinal section diagram of seismic interpretation of various phases of a certain gravel rock body in Shengli work area described in Example 2 of the present invention;

[0028] Figure 3 This is a structural diagram of the top surface of the gravel rock mass in Shengli work area (top surface of the fan body in phase 1) described in Example 2 of the present invention;

[0029] Figure 4 It is a top surface structural diagram of a small range of fans outside the longitudinal overlap range of the fans of phase 2 and phase 1 of a certain gravel body in the Shengli work area described in Example 2 of the present invention;

[0030] Figure 5 This is a time length diagram of the first sector of the gravel body in the Shengli work area described in Example 2 of the present invention;

[0031] Figure 6 This is a thickness contour map of the first sector of the gravel body in Shengli work area described in Example 2 of the present invention;

[0032] Figure 7 It is a local top surface structural diagram of the longitudinal overlap range of the second sector and the first sector of the gravel body in the Shengli work area described in Example 2 of the present invention;

[0033] Figure 8 The top surface structural diagram of the Shengli work area at the true depth of the second sector of the gravel body stage described in Example 2 of the present invention;

[0034] Fig. 9 This is the top surface structure map of the Shengli work area formed by direct conversion of the velocity curve of the second fan area of ​​the gravel body stage. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0037] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0038] Example 1

[0039] like Figure 1 As shown, the method for mapping the fans of the sandstone body at each stage includes the following steps:

[0040] Step 101, using 3D seismic data to perform detailed interpretation of the sandstone conglomerate fan to clarify the development stages of the fan.

[0041] Firstly, the seismic reflection characteristics of the conglomerate fan are clarified by well-seismic calibration using actual drilling and 3D seismic data. Then, the fan stages are interpreted and tracked in detail to clarify the development stages of the conglomerate.

[0042] Step 102: Count the actual drilling layer velocity V of each sector of the gravel body n .

[0043] Based on the logging data of various fan bodies corresponding to the actual drilling of a large number of sandstone and conglomerate bodies calibrated in step 101, sampling statistics are carried out to determine the layer velocity of each fan body in each period.

[0044] Step 103: Calculate the top depth H of each sector using the regional velocity curve and actual drilling correction n , forming a small-scale fan top surface structural diagram outside the range of longitudinal overlap between each period of fans and the previous period of fans.

[0045] The top structural depth of each stage fan of the gravel body in step 1 is calculated using the regional velocity curve, and the depth error statistics between the structural map of the stage 1 fan and the actual drilling are used to determine the correction amount. The correction amount is used to correct the top structural maps of the remaining stages of the fans, and the top structural maps of the small range of fans with real depth outside the longitudinal overlap range of each stage fan and the previous stage fan are obtained.

[0046] Step 104, using the sector layer velocity and travel time of each period, calculate the sector thickness ΔH of each period n =Δt n *V n , forming the thickness contour map of each sector in each period;

[0047] First, use the travel times of each sector into the formula Δt n =t n+1 -t n Calculate the time length of each sector in each period and form a time length diagram of each sector in each period; then substitute the layer velocity counted in step 102 into the formula ΔH n =Δt n *V n Convert it into the actual thickness of the fan body in each period to form the thickness contour map of the fan body in each period.

[0048] Step 105, calculating the depth value of the local fan body in the longitudinal overlap range of each period of fan body and the previous period of fan body, and drawing the fan body top surface structure diagram of the local range of the longitudinal overlap range of each period of fan body and the previous period of fan body.

[0049] The thickness accumulation method is used to accurately calculate the depth of the fan body of each period within the longitudinal overlap range of the fan body of the previous period. The top surface structural depth of the fan body of period 1 and the thickness of the fan bodies of each period are successively accumulated, that is, H n =H1+ΔH1+ΔH2+……+ΔH n-1 , the fan depths of the 2nd, 3rd, ..., nth period fans overlapping with the previous period fans are obtained in turn and formed into the corresponding local range top surface structure map.

[0050] Step 106, splicing the top surface structural map of the small-scale fan body with the top surface structural map of the local-scale fan body to form a complete top surface structural map of the fan body in each period with real depth.

[0051] The top surface structural map of the local range of each period fan body obtained in step 105 and the top surface structural map of the small range of each period fan body obtained in step 103 are spliced ​​to form the top surface structural map of the complete real depth of each period fan body.

[0052] When the fan interpretation ranges of the nth period and the n-1th period at the fan root position are inconsistent, the values ​​are calculated and mapped according to the nth period fan range.

[0053] When the n-th period fan range at the fan end position is larger than the n-1-th period fan range, the range beyond the n-1 period can be mapped using the regional velocity curve and depth correction can be performed using actual drilling. When the n-th period fan range at the fan end position is smaller than the n-1-th period fan range, the thickness is accumulated according to the n-th period fan range, the depth is calculated and mapped using actual drilling correction.

[0054] Example 2

[0055] The method described in Example 1 is used to map the sectors of a gravel body in Shengli work area at different stages, including the following steps:

[0056] Step 1: Use 3D seismic data to interpret the sandy conglomerate fan in detail and clarify the development period of the fan: First, use the actual drilling and 3D seismic data to calibrate the wells and seismic reflection characteristics of the sandy conglomerate fan, and then conduct detailed interpretation and tracking of the fan stages to clarify the development period of the sandy conglomerate. The longitudinal section of the fan stage interpretation of the sandy conglomerate fan is as follows: Figure 2 shown.

[0057] Step 2, counting the actual drilling layer velocity Vn of each sector of the gravel body;

[0058] Based on the logging data of various fan bodies corresponding to the actual drilling of a large number of sandstone and conglomerate bodies calibrated in step 1, sampling statistics are carried out to determine the layer velocity of each fan body, as shown in Table 1.

[0059] Table 1 is a statistical table of the velocity of each sub-fan layer of a gravel body in Shengli Work Area

[0060] sector period Gravel layer velocity Δv (m / s) 1 4300 2 4355 3 4690 4 5000 5 5125 6 5260 7 5810

[0061] Step 3: Calculate the top depth H of each sector using the regional velocity curve and actual drilling correction. n , forming a small range of fan top surface structural diagram outside the longitudinal overlap range of each period of fan and the previous period of fan;

[0062] The regional velocity curve is used to calculate the top structural depth of each stage of the conglomerate fan body, and the depth error statistics between the structural map of the stage 1 fan body and the actual drilling are used to determine the correction amount. The correction amount is used to correct the top structural maps of the remaining stages of the fans, and the real depth top structural maps of the small range of fans outside the longitudinal overlap range of each stage fan body and the previous stage fan body are obtained. Figure 3 This is a structural map of the top surface of the first fan of a gravel body in Shengli work area. Figure 4 This is a structural map of the top surface of a small area of ​​a conglomerate body in the Shengli work area, outside the range of the longitudinal overlap between the Phase 2 fan and the Phase 1 fan.

[0063] Step 4: Calculate the thickness of each sector ΔH using the sector layer velocity and travel time of each period n =Δt n *V n , forming contour maps of fan thickness in each period.

[0064] First, use the travel times of each sector into the formula Δt n =t n+1 -t n Calculate the time length of each sector and form a time length diagram of each sector; then substitute the layer velocity calculated in step 2 into the formula ΔH n =Δt n *V n Convert it into the actual thickness of the fan body in each period to form the thickness contour map of the fan body in each period. Figure 5 This is the time length diagram of the first fan of a sandy conglomerate body in Shengli work area; Figure 6 This is the thickness contour map of the first fan of a gravel body in Shengli work area.

[0065] Step 5, calculating the depth value of the local fan body in the longitudinal overlap range of each period of fan body and the previous period of fan body, and forming the fan body top surface structure diagram of the local range of the longitudinal overlap range of each period of fan body and the previous period of fan body.

[0066] The thickness accumulation method is used to accurately calculate the fan depth value of the longitudinal overlap range of each period of the fan body and the previous period of the fan body. The top surface structural depth of the fan body of period 1 and the thickness of the fan bodies of each period are accumulated in sequence, that is, H n =H1+ΔH1+ΔH2+……+ΔHn-1 , the fan depths of the 2nd, 3rd, ..., nth period fans overlapping with the previous period fans are obtained in turn and formed into the corresponding local range top surface structure map. Figure 7 This is a local fan top surface structural map of the longitudinal overlap range between fan 2 and fan 1 of a sandstone body in Shengli work area.

[0067] Step 6, splicing the top surface structural map of the small-scale fan body with the top surface structural map of the local-scale fan body to form a complete real-depth top surface structural map of the fan body in each period.

[0068] The top surface structural map of the local range of each period fan body obtained in step 5 is spliced ​​with the top surface structural map of a small range of each period fan body obtained in step 3 to form the top surface structural map of the complete real depth of each period fan body. Figure 8 This is the top surface structural map of the true depth of the second fan of a gravel body in Shengli work area.

[0069] Fig. 9 This is a top surface structural map of the second fan of a gravel body in the Shengli work area directly converted using the regional velocity curve.

[0070] Figure 8 The structural morphology in the dashed box and Fig. 9 Compared with Figure 8 That is, after the gravel body was mapped using this method, the location of the structural high changed and moved significantly to the south; Figure 8 The calculated inclination angle of the sector in the dotted box is 11.2°. Fig. 9 The calculated inclination angle of the fan body in the dotted box is 6.6°, and the calculated inclination angle of the fan body in the actual drilling wells (Li 943 and Li 567) is 10.8°. Figure 8 The calculated fan inclination is closer to the actual well calculation; it is confirmed that the mapping method can eliminate structural illusions such as the structural high point offset caused by the fan root pull-up caused by the high-speed body of sandstone and conglomerate, and the change of fan body occurrence.

[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for mapping the sectors of a sandstone mass at different stages, characterized in that: It includes the following steps: Step 1. Conduct detailed interpretation of the sandstone fan and clarify the development stages of the fan; Step 2. Determine the interval velocity of each sector of the gravel body during actual drilling; Step 3. Calculate the top depth of each phase of the fan body, and draw a small range of fan body top surface structural diagram outside the longitudinal overlap range of each phase of the fan body and the previous phase of the fan body; Step 4. Calculate the thickness of the fan body in each period and draw a contour map of the thickness of the fan body in each period; Step 5. Calculate the depth value of the local fan body in the longitudinal overlap range of each period of fan body and the previous period of fan body respectively, and draw the fan body top surface structure diagram of the local range of the longitudinal overlap range of each period of fan body and the previous period of fan body; Step 6. Draw the complete depth top surface structure diagram of each phase fan; In step 3, the top structural depth of each phase of the conglomerate fan is calculated using the regional velocity curve, and the depth error statistics between the structural map of the phase 1 fan and the actual drilling are used to determine the correction amount, and the top structural map of the remaining phases of the fan is corrected using the correction amount to obtain the top structural map of the small range of the fan with the real depth outside the longitudinal overlap range of each phase of the fan and the previous phase of the fan; In step 5, the thickness accumulation method is used to calculate the depth of each sector in the longitudinal overlap range of the sector of the previous sector. The top surface structural depth of the sector of phase 1 and the thickness of the sectors of each phase are successively accumulated, that is, H n =H1+ΔH1+ΔH2+……+ΔH n-1 , successively obtain the fan depths of the overlapped range of the 2nd, 3rd, ..., nth period fans and the previous period fans and form the corresponding local range top surface structure map; In step 6, the local top surface structural map of each period fan obtained in step 5 and the small top surface structural map of each period fan obtained in step 3 are spliced ​​to form the complete real depth top surface structural map of each period fan.

2. The method for mapping the sectors of a sandstone mass at each stage according to claim 1 is characterized in that: In step 1, the seismic reflection characteristics of the conglomerate fan are first clarified by well-seismic calibration using actual drilling and 3D seismic data, and then detailed interpretation and tracking of the fan stages are carried out to clarify the development stages of the conglomerate body.

3. The method for mapping the sectors of a sandstone mass at each stage according to claim 1 is characterized in that: In step 2, sampling statistics are carried out based on the logging data of each period of the fan corresponding to the actual drilling of the sandstone and conglomerate body calibrated in step 1 to determine the layer velocity of each period of the fan.

4. The method for mapping the sectors of a sandstone mass at each stage according to claim 1 is characterized in that: In step 4, first use the travel times of each sector to enter the formula Δt n =t n+1 -t n Calculate the time length of each sector and draw a diagram of the time length of each sector; then substitute the sector layer velocity of each sector into the formula ΔH n =Δt n *V n Convert it into the actual thickness of the fan body in each period to form the thickness contour map of the fan body in each period.

5. The method for mapping the sectors of a sandstone mass at each stage according to claim 1 is characterized in that: When the fan interpretation ranges of the nth period and the n-1th period at the fan root position are inconsistent, the values ​​are calculated and mapped according to the nth period fan range.

6. The method for mapping the sectors of a sandstone mass at each stage according to claim 1, characterized in that: When the n-th period fan range at the fan end position is larger than the n-1-th period fan range, the range beyond the n-1 period can be mapped using the regional velocity curve and depth correction can be performed using actual drilling. When the n-th period fan range at the fan end position is smaller than the n-1-th period fan range, the thickness is accumulated according to the n-th period fan range, the depth is calculated and mapped using actual drilling correction.

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