Method for constructing river channel plane distribution mode based on outcrop profile

Abstract

The invention belongs to the technical field of oil and gas field development, and particularly relates to a method for constructing a river channel plane distribution mode based on an outcrop profile. According to the method, on the basis of images, coordinates and lithologic data of field outcrop strata, strata layering, sedimentary features, vertical sequences and other information are extracted with single layers as basic units, sedimentary facies belt recognition, sedimentary configuration unit recognition and scale measurement are carried out on the single layers, and the strata strata are obtained. And then phase sequence arrangement is carried out on each single layer by utilizing sedimentary configuration unit types, combination styles and scale information, a phase belt to which each layer belongs and a relative distance between the phase belt and a material source are determined, and then a delta sedimentary system plane distribution mode is constructed according to a distribution rule and a combination relation of each single layer on a plane, so that underground reservoir depiction and characterization are guided.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a method for constructing a river channel plane distribution model based on an outcrop profile. Background Art

[0002] In the study of underground delta reservoirs, the plane distribution pattern of delta sedimentary systems is an important basis and premise for guiding reservoir characterization and representation. So far, universal and conceptual sedimentary models are generally used for guidance and constraints in the characterization and representation of underground delta reservoirs. However, the ideal conceptual model is too abstract, and there are problems such as being reasonable in general but very different in details, which cannot meet the research needs of fine reservoir characterization and representation. In fact, for a delta sedimentary system developed in a certain area at a certain time, using adjacent field outcrop strata of the same era and position to conduct model research and guide the characterization and representation of underground reservoirs is a highly reasonable, reliable, accurate and targeted means. However, field outcrops are usually single profiles, lacking information on plane distribution patterns, and cannot be directly used for plane model construction.

[0003] In the prior art, a Chinese patent document with application publication number CN103760617A discloses a method and device for acquiring the growth law and sedimentation pattern of a shallow lake basin delta. The method includes using multi-temporal remote sensing images and field sedimentation survey data to establish various sedimentary microfacies identification templates for shallow lake basin deltas, using the microfacies identification templates to obtain multi-temporal interpretation vectors and superimpose and compare, quantitatively analyze delta growth elements, and then analyze the delta growth law and sedimentation pattern. This method mainly uses the interpretation vectors of modern delta sedimentary remote sensing images, and the analysis time is relatively short compared to the geological history deposition time. In addition, there are problems that the modern sediments and underground delta sedimentary reservoirs are generally reasonable but have large differences in details, which makes it difficult to meet the research needs of fine characterization of the reservoir.

[0004] The non-patent literature "Sedimentary Characteristics and Patterns of Outcrops of the Jingzigou Formation in the Southern Margin of the Junggar Basin" provides a method to subdivide lithofacies and sedimentary cycles based on the sedimentary characteristics of field profiles and then establish a delta sedimentary model. However, this method lacks quantitative research on internal sedimentary architectural units and only establishes a conceptual model, which cannot be applied to the fine characterization of reservoirs. Summary of the invention

[0005] The purpose of the present invention is to provide a method for constructing a river channel planar distribution pattern based on an outcrop profile, so as to solve the problem that the existing methods are difficult to satisfy the fine characterization of reservoirs.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for constructing a river channel plan distribution pattern based on an outcrop profile comprises the following steps:

[0008] (1) Prepare an orthophoto profile of the target outcrop;

[0009] (2) Identify stratigraphic units at all levels from the orthophoto section and determine the single-layer interface;

[0010] (3) Analyze the sedimentary characteristics within the single layer, determine the lithology, sedimentary facies, and sedimentary architectural unit types, and classify and measure the scale of sedimentary architectural units;

[0011] (4) determining whether the correlation between the width of the diversion channel sand body and the thickness of the sand body meets the requirements: if it meets the requirements, proceed to step (5); if it does not meet the requirements, return to step (3) and re-measure;

[0012] (5) Sort the relative positions of each single layer according to its facies belt, architectural unit size, and sand-to-ground ratio to determine the distance relationship of each river channel;

[0013] (6) Based on the sorting results, the sedimentary architecture unit types and combination patterns are analyzed to establish the planar distribution model of the delta sedimentary system.

[0014] Based on the images, coordinates and lithological data of outcrop strata in the field, the present invention extracts information such as stratigraphic stratification, sedimentary characteristics, vertical sequence, etc. with single layer as the basic unit, carries out sedimentary facies belt identification, sedimentary architecture unit identification and scale measurement for each single layer, then arranges each single layer in phase sequence using the sedimentary architecture unit type, combination style and scale information, determines the facies belt to which each layer belongs and its relative distance from the source, and then constructs the planar distribution pattern of the delta sedimentary system through the distribution law and combination relationship of each single layer on the plane, thereby guiding the characterization and representation of the underground reservoir.

[0015] The delta plane distribution model established by the present invention not only contains real scale information, but also contains the scale, morphology, combination law and internal structure information of the distributary channels indicated by the outcrop profile, thus it can effectively guide the characterization and representation research of delta sedimentary reservoirs.

[0016] Preferably, in step (5), the sorting is to sort the diversion channels according to the thickness of the sand body. The greater the thickness, the closer the corresponding diversion channel is to the upstream area of ​​the sedimentary system, and vice versa. The corresponding diversion channel is closer to the downstream area of ​​the sedimentary system. This method uses the river depth represented by the sand body thickness as the main sorting index and arranges in descending order of thickness, which can quickly obtain a basic sorting result.

[0017] Preferably, the thickness of the diversion channel sand bodies is the same, and auxiliary sorting is further performed according to the width of the diversion channel sand bodies. The larger the width of the channel sand bodies, the larger its scale and the closer it is to the upstream area of ​​the sedimentary system, and vice versa. On the basis of the thickness sorting, auxiliary sorting is performed according to the width of the diversion channel sand bodies, which can further refine the sorting results and provide support for the subsequent refined construction of the plane distribution pattern of the delta sedimentary system.

[0018] In order to further effectively guide the detailed characterization and characterization of deltaic sedimentary reservoirs, preferably, in step (6), the establishment of the planar distribution model of the deltaic sedimentary system includes the following steps:

[0019] (a) Placing the diversion channel profile on a plane according to the sorting results, and performing plane combination according to the morphology and internal structure style of the diversion channel on the profile to obtain the plane distribution pattern of the diversion channel;

[0020] (b) Predict the flow lines of distributary channels based on the morphology and composition of the channel, within the constraints of sedimentological principles and modern sedimentary patterns;

[0021] (c) The planar distribution pattern of the distributary channel system is depicted based on the skeleton characteristics of the channel system indicated by the streamlines of the distributary channel, and finally a three-dimensional sedimentary model that integrates the plane and section is obtained.

[0022] Preferably, in step (4), the compliance requirement is consistent with the width and depth relationship of the natural delta distributary channel. Through the correlation demonstration of this step, it can be proved that the measurement results are reasonable and reliable as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a technical flow chart of the present invention;

[0024] Figure 2 is a schematic diagram of the field outcrop sedimentology analysis in Example 1 of the present invention;

[0025] Figure 3 Schematic diagram of the correlation analysis between the width and thickness of the sand body in Example 1 of the present invention;

[0026] Figure 4 1 is a schematic diagram of the results of sorting the thickness of the river channel sand bodies in Example 1 of the present invention;

[0027] Figure 5 Schematic diagram of the auxiliary comprehensive sorting result of the width of the river channel sand body in Example 1 of the present invention;

[0028] Figure 6 This is a schematic diagram of the river channel plane sorting result in Example 1 of the present invention;

[0029] Figure 7 is a schematic diagram of the prediction result of the deposition system skeleton in Example 1 of the present invention;

[0030] Figure 8 is a schematic diagram of a planar mode of a deposition system in Example 1 of the present invention;

[0031] Fig. 9 It is a plan distribution diagram of the delta plain sedimentary system of the Shanxi Formation of the Permian System in a gas field in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The present invention mainly provides a method for constructing a plane distribution model of a delta sedimentary system using field outcrop profile data. Based on the images, coordinates and lithology data of field outcrop strata, the method extracts information such as stratigraphic stratification, sedimentary characteristics, and vertical sequence with a single layer as the basic unit, and carries out sedimentary phase belt identification, sedimentary configuration unit identification and scale measurement for each single layer. Subsequently, each single layer is arranged in phase sequence using the type, combination style and scale information of the sedimentary configuration unit, and the phase belt to which each layer belongs and its relative distance from the source are determined. Then, the plane distribution model of the delta sedimentary system is constructed through the distribution law and combination relationship of each single layer on the plane, thereby guiding the characterization and representation of the underground reservoir.

[0033] Specifically, the method for constructing the plane distribution model of the delta sedimentary system of the present invention comprises the following steps:

[0034] 1) Use UAV oblique photography, 3D reconstruction and orthophoto sectioning to obtain high-precision profiles with geographic information;

[0035] 2) Identify stratigraphic units at all levels from the cross-section diagram and determine the single-layer interface;

[0036] 3) Analyze the sedimentary characteristics within the single layer, determine the lithology, sedimentary facies, and sedimentary structural unit types, and classify and measure the scale of the sedimentary structural units (including width and length);

[0037] 4) Correlation analysis between sand body width and thickness;

[0038] 5) Sort the relative positions of each single layer according to its phase belt, architectural unit scale, and sand-to-ground ratio;

[0039] 6) Based on the sorting results, the sedimentary architecture unit types and combination styles are analyzed to establish the planar distribution model of the delta sedimentary system.

[0040] In step 1), a drone or camera with high-precision geolocation acquisition function is used to take detailed photos of the target outcrop profile. For each part of the profile, at least 5 different directions of shooting records should be taken. Then, the outcrop 3D model is established using the oblique photography modeling tool and the orthophoto profile calculation tool is used to draw the orthophoto profile to obtain a profile picture with no visual distortion and real scale. The orthophoto projection direction should be along the paleo-flow direction of the river system.

[0041] In step 2), the stratigraphic groups and segment interfaces are obtained based on public literature data, and the oil groups, sand groups, sublayers and single layers are compared step by step according to the lithology and distribution patterns of the profile, and finally the single layer comparison results are obtained. During the comparison process, the stratigraphic interface should be tracked according to the distribution and continuity characteristics of the stable lithology interface in the orthographic projection of the outcrop profile. The results of the single layer comparison must ensure that only one distributary channel sand body is developed vertically at any position within the single layer.

[0042] In step 3), the lithology, sedimentary facies type, sedimentary configuration unit type and boundary of each single layer on the profile are determined according to the sedimentological principles, and the width and length of each configuration unit are measured according to the ortho-profile.

[0043] In step 4), the width and thickness data of the diversion channel sand body measured in step 3) are subjected to correlation fitting. If the data have an obvious positive correlation and its R 2 >0.5, it can be considered that there is an obvious positive correlation between the width of the river channel and the thickness of the sand body, which is consistent with the width and depth relationship of the natural delta distributary channel, proving that the measurement results are reasonable and reliable as a whole. Otherwise, the data measurement accuracy is not enough, and return to step 3) for re-measurement.

[0044] In step 5), the river depth represented by the sand body thickness is used as the main sorting index and arranged in descending order of thickness. The greater the depth, the closer the corresponding diversion channel is to the upstream area of ​​the sedimentary system, and vice versa. If the thickness of the sand bodies in different river channels is the same, their width is used as an auxiliary variable for secondary sorting. The larger the width of the river channel sand body, the larger its scale and the closer it is to the upstream area of ​​the sedimentary system, and vice versa. The distance relationship of each river channel is determined by sorting by thickness and width.

[0045] In step 6), the sedimentary configuration unit type and combination style are analyzed according to the sorting results to establish the plane distribution pattern of the delta sedimentary system. The specific steps include: ① placing the distributary channel profile on the plane at an appropriate proportion according to the sorting results, and performing plane combination according to the morphology, internal structure style and other information of the distributary channel on the profile to obtain the plane distribution pattern of the distributary channel; ② predicting the flow lines of the distributary channel according to the morphology and combination rules of the channel, under the constraints of sedimentological principles and modern sedimentary styles (derived from public data and literature); ③ describing the plane distribution pattern of the distributary channel system according to the skeleton characteristics of the channel system indicated by the distributary channel flow lines, and finally obtaining a three-dimensional sedimentary model that links the plane and the profile.

[0046] The implementation process of the present invention is described in detail below in conjunction with specific embodiments.

[0047] Example 1

[0048] The method of constructing the river channel plane distribution pattern based on the outcrop profile in this embodiment is as follows: Figure 1 As shown, the following steps are included:

[0049] 1) Use UAV oblique photography, 3D reconstruction and orthophoto profile production to obtain high-precision profiles with geographic information.

[0050] A commercial drone was used to take all-round photos of the outcrop and record the camera's geographic coordinates. Then, an oblique photography modeling tool was used to build a three-dimensional model of the outcrop, and an orthographic projection profile calculation tool was used to draw an orthographic profile. Figure 2 This is a schematic diagram of the sedimentological analysis of the field outcrop, where the orthophoto section drawing results for the outcrop section are shown in Figure 2 As shown in a, a cross-sectional image with no visual deformation and true scale is obtained.

[0051] 2) Identify stratigraphic units at each level from the cross-section diagram and determine the single-layer interface.

[0052] exist Figure 2 On the section shown in a, based on the lithology and stratigraphic interface information, combined with the development characteristics of the sedimentary system, stratigraphic hierarchical tracking is carried out. Through the six levels of group, section, oil group, sand group, small layer and single layer, a series of stratigraphic interfaces at the single layer scale are obtained ( Figure 2 b). The interface of groups and sections is derived from public literature, and the oil group, sand group, sub-layer and single layer are divided step by step according to the stratigraphic characteristics.

[0053] 3) Analyze the sedimentary characteristics within a single layer, determine the lithology, sedimentary facies, and sedimentary structural unit types, and classify and measure the scale of sedimentary structural units (including width and length).

[0054] In this example, based on on-site observations and ortho-profile analysis, two main types of lithology were identified, including sandstone and mudstone, of which the distributary channels were sandstone and the inter-channel floodplains were mudstone. Based on the sand body morphology, internal sedimentary structure, and on-site plant fossils on the profile, it was determined that the sedimentary facies belt belongs to the delta plain subfacies. Sedimentary architectural units include distributary channels and inter-channel floodplains, but there are obvious differences in the morphology and scale of distributary channels. A total of 41 single channels ( Figure 2 c, d), and use the information such as the profile geographic coordinates to measure the thickness and width of the above-mentioned rivers one by one, as shown in Table 1.

[0055] Table 1 Field outcrop sedimentary structure unit measurement data

[0056]

[0057]

[0058] 4) Correlation analysis between sand body width and thickness

[0059] In this embodiment, the correlation analysis between the width and thickness of the sand body is carried out by fitting the correlation between the two. According to the fitting results, there is a significant positive correlation between the width and the thickness, and its R 2 >0.5( Figure 3 ), indicating that there is an obvious positive correlation between the channel width and the sand body thickness, which is consistent with the relationship between the width and depth of the delta distributary channel in nature, proving that the measurement results are reasonable and reliable as a whole.

[0060] 5) Sort the relative positions of each single layer according to its phase belt, architectural unit scale, and sand-to-ground ratio;

[0061] In this example, the diversion channels are prioritized according to the thickness of the sand body. The basic principle is that the closer the diversion channel is to the source, the deeper it is, and it becomes shallower towards the lake. Figure 4 shown.

[0062] On this basis, auxiliary sorting is performed according to the width of the distributary channel sand body. The larger the width, the larger the channel scale and the more upstream its distribution position in the entire system. The sorting results of the distributary channel sand body width are shown in Figure 2. Figure 5 shown.

[0063] 6) Based on the sorting results, the sedimentary architecture unit types and combination styles are analyzed to establish the planar distribution model of the delta sedimentary system.

[0064] In this embodiment, after the relative positions of the diversion channels are sorted, the diversion channel sections are placed on the plane according to an appropriate ratio, and the plane combination is performed according to the shape, quantity, distribution pattern (including isolation, lateral cutting, etc.) of the diversion channels on the section, so as to obtain Figure 6 The plane distribution style shown.

[0065] On this basis, according to the morphology and combination rules of the river channel, under the constraints of sedimentological principles and modern sedimentary patterns, the flow lines of the distributary channels are predicted ( Figure 7 ), then, the planar distribution pattern of the distributary channel system is depicted according to the channel system skeleton characteristics indicated by the distributary channel streamlines, and finally a three-dimensional sedimentary model with plane and section linkage is obtained ( Figure 8 ), under the guidance of the above model and the constraint of river channel scale, the plane distribution characteristics of the distributary channel system of the Shanxi Formation delta plain in the Permian of a gas field were analyzed, and the flow lines of the distributary channels were drawn based on the sand body thickness data revealed by drilling. Figure 8 The sedimentary patterns shown (such as the distribution characteristics and morphology of the river system) were used to draw the sedimentary facies diagram ( Fig. 9 ).

Claims

1. A method for constructing a river channel plan distribution pattern based on an outcrop profile, characterized in that: The following steps are involved: (1) Prepare an orthophoto profile of the target outcrop; (2) Identify stratigraphic units at all levels from the orthophoto section and determine the single-layer interface; (3) Analyze the sedimentary characteristics within the single layer, determine the lithology, sedimentary facies, and sedimentary architectural unit types, and classify and measure the scale of sedimentary architectural units; (4) determining whether the correlation between the width of the diversion channel sand body and the thickness of the sand body meets the requirements: if it meets the requirements, proceed to step (5); if it does not meet the requirements, return to step (3) and re-measure; (5) Sort the relative positions of each single layer according to its facies belt, architectural unit size, and sand-to-ground ratio to determine the distance relationship of each river channel; (6) Based on the sorting results, the sedimentary architecture unit types and combination patterns are analyzed to establish the planar distribution model of the delta sedimentary system.

2. The method for constructing a river channel plan distribution pattern based on an outcrop profile according to claim 1, characterized in that: In step (5), the sorting is to sort the distributary channels according to the thickness of the sand body. The greater the thickness, the closer the corresponding distributary channel is to the upstream area of ​​the sedimentary system, and vice versa.

3. The method for constructing a river channel plan distribution pattern based on an outcrop profile according to claim 2, characterized in that: The thickness of the distributary channel sand bodies is the same, and further auxiliary sorting is performed according to the width of the distributary channel sand bodies. The larger the width of the channel sand body, the larger its scale and the closer it is to the upstream area of ​​the sedimentary system, and vice versa.

4. The method for constructing a river channel plan distribution pattern based on an outcrop profile according to claim 1, characterized in that: In step (6), establishing the planar distribution model of the delta deposition system comprises the following steps: (a) Placing the diversion channel profile on a plane according to the sorting results, and performing plane combination according to the morphology and internal structure style of the diversion channel on the profile to obtain the plane distribution pattern of the diversion channel; (b) Predict the flow lines of distributary channels based on the morphology and composition of the channel, within the constraints of sedimentological principles and modern sedimentary patterns; (c) The planar distribution pattern of the distributary channel system is depicted based on the skeleton characteristics of the channel system indicated by the streamlines of the distributary channel, and finally a three-dimensional sedimentary model that integrates the plane and section is obtained.

5. The method for constructing a river channel plan distribution pattern based on an outcrop profile according to any one of claims 1 to 4, characterized in that: In step (4), the compliance requirement is to be consistent with the width and depth relationship of the natural delta diversion channel.

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