Sand body fine description method and system based on isochronous seismic stratigraphic framework construction

Abstract

The invention discloses a sand body fine description method and system based on isochronous seismic stratigraphic framework construction, and belongs to the technical field of oil exploration and development. The fine depicting method for the sand body comprises the following steps: identifying and comparing a marker bed by utilizing lithology and electrical property change rules; performing synthetic record calibration and constructing an isochronous seismic stratigraphic framework by utilizing reflection characteristics of a comparison marker bed in a three-dimensional seismic section; in an isochronous earthquake stratigraphic framework, through inverse verification of a forward model and identification of a special geologic body, carding response characteristics of a sand body on an earthquake to obtain sand body response characteristics; on the basis of the sand body response characteristics and the amplitude threshold value, reservoir prediction is carried out by adopting a plurality of seismic methods, and a sand body macroscopic distribution rule is depicted; the sand body communication relation is judged through dynamic and static data, and the sand body distribution form is depicted finely; and based on the sand body macroscopic distribution rule, the sand body distribution form is finely depicted, the target sand body distribution form and the target sand body characteristics are obtained, and fine depiction of the sand body is completed.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil exploration and development, and particularly relates to a method and system for fine characterization of sand bodies based on the construction of an isochronous seismic stratigraphic framework. Background Art

[0002] The lower gas-bearing formation in a condensate gas field is significantly controlled by seasonal floods, with rapid channel migration, multiple-stage channel stacking, strong reservoir heterogeneity, and complex gas-water relationships. It is a typical continental braided river depositional system. During the development process, the following phenomena are often encountered: in the same structure and the same sand body, hydrocarbons are contained in the lower part while water is contained in the higher part, or among multiple channel sand bodies deposited during the same period, some contain hydrocarbons while some do not. The same sand body has different hydrocarbon-bearing properties, which are not only controlled by reservoir diagenesis, clay type, and heterogeneity, but also closely related to the planar connectivity of the sand body. Therefore, carrying out research on sand body characterization and understanding the longitudinal and lateral distribution laws of sand bodies have extremely important research significance for the rolling deployment of gas reservoirs.

[0003] Currently, researchers have made certain progress in sand body characterization research. The commonly used method is to emphasize the principle of equal thickness, use logging curves for sub-layer division, and then conduct reservoir prediction within the sub-layers through seismic attributes to further determine the planar distribution law of sand bodies.

[0004] However, these technologies have deficiencies. On the one hand, when using logging curves for sub-layer division and correlation, the sub-layers divided often show the phenomena of crossing the axis and time in the seismic section, and major dynamic-static contradictions will be encountered when carrying out sand body characterization based on this; on the other hand, only through seismic attributes for reservoir prediction, the results can only depict the macroscopic characteristics of sand bodies, and the internal connectivity and gas-water distribution characteristics are often inaccurately depicted. In addition, the above methods are difficult to effectively guide the research on the rolling deployment of gas reservoirs. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method and system for fine characterization of sand bodies based on the construction of an isochronous seismic stratigraphic framework, adopting a method that combines dynamic and static, and well and seismic, and jointly tackling key problems to determine the planar distribution law of complex continental river channel sand bodies in front of mountains.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions to be realized:

[0007] The present invention provides a method for fine characterization of sand bodies based on the construction of an isochronous seismic stratigraphic framework, including the following steps:

[0008] S1: Identify and contrast marker beds using the variation laws of lithology and electric properties;

[0009] S2: Utilize the reflection characteristics of the contrast marker beds in the 3D seismic profile, conduct synthetic seismogram calibration, and establish an isochronous seismic stratigraphic framework;

[0010] S3: Within the isochronous seismic stratigraphic framework, through the refutation of the forward modeling and the identification of special geological bodies, sort out the seismic response characteristics of the sand bodies to obtain the sand body response characteristics;

[0011] S4: Based on the sand body response characteristics and the amplitude threshold value, use several seismic methods for reservoir prediction to depict the macroscopic distribution law of the sand bodies;

[0012] S5: Utilize dynamic and static data to judge the connectivity relationship of the sand bodies and finely depict the distribution pattern of the sand bodies;

[0013] S6: Based on the macroscopic distribution law of the sand bodies and the finely depicted distribution pattern of the sand bodies, obtain the distribution pattern and characteristics of the target sand bodies to complete the fine characterization of the sand bodies.

[0014] In the specific implementation process, in S1, the identification of the contrast marker beds by using the lithology and electrical property variation laws includes the following steps:

[0015] S11: Identify the resistivity and spontaneous potential curves based on the lithology and electrical property variation laws to obtain the lithology and sedimentary cycle structure;

[0016] S12: Obtain the contrast marker beds based on the lithology and sedimentary cycle structure;

[0017] The sedimentary cycle includes sedimentary positive cycle and sedimentary negative cycle; the contrast marker bed is the sedimentary transition point.

[0018] In the specific implementation process, the contrast marker beds include the top layer of the sedimentary positive cycle, the top layer of the sedimentary negative cycle, and the bottom layer of the sedimentary negative cycle.

[0019] In the specific implementation process, in S2, the process of utilizing the reflection characteristics of the contrast marker beds in the 3D seismic profile, conducting synthetic seismogram calibration, and establishing an isochronous seismic stratigraphic framework is as follows:

[0020] Utilize the lithology change of the contrast marker beds to reflect the characteristics in the 3D seismic profile and conduct synthetic seismogram calibration. The top layer of the sedimentary positive cycle and the bottom layer of the sedimentary negative cycle are strong wave peak reflections, and the top layer of the sedimentary negative cycle is the zero phase of the strong wave trough and wave peak;

[0021] Establish an isochronous seismic stratigraphic framework, and within it, use the variation law of reflection isophase axis to guide the sub - layer division and sand body characterization in the sand - shale interbedded sedimentary environment. Among them, an isochronous reflection interface represents a geological interface or sedimentary unit.

[0022] In the specific implementation process, in S3, the seismic response characteristics of the target sand body include sandstone response characteristics and mudstone response characteristics;

[0023] The sandstone response characteristic is a set of trough characteristics of strong reflection, and the mudstone response characteristic is a set of peak characteristics of strong reflection.

[0024] In the specific implementation process, in S3, the geological phenomena for the identification of the special geological body include:

[0025] The geological phenomena that the amplitude of the in-phase axis corresponding to the reservoir changing from thick to thin will change from strong to weak, the in-phase axis corresponding to the non-connected reservoir shows dislocation, and the phase change of sandstone and mudstone will cause the in-phase axis to be distorted.

[0026] In the specific implementation process, in S4, the amplitude threshold value is -2200; when it is higher than the amplitude threshold value, the sand body is not developed, and when it is lower than the amplitude threshold value, the sand body is developed;

[0027] The several seismic methods include wave impedance inversion method, conventional amplitude method, root mean square amplitude method after wavelet reconstruction, and high-precision reservoir inversion method.

[0028] In the specific implementation process, in S5, the judgment conditions for the connectivity of the sand body are as follows:

[0029] It conforms to the regional climate, facies belt characteristics and provenance development direction, follows the sedimentation law that the single sand body has a large thickness and good connectivity in the provenance direction of the river channel, the single sand body has a thin thickness and a short extension distance in the direction perpendicular to the provenance of the river channel; and by using the correlation marker bed or auxiliary marker bed inside the small layer under the control of the horizon, and adopting the principles of equivalent horizon, same lithology, similar electric property, similar fluid and consistent structure to judge the connectivity of the sand body.

[0030] In the specific implementation process, it also includes recognizing the gas reservoir type based on the distribution pattern and characteristics of the target sand body to select the rolling target of the gas reservoir.

[0031] The present invention also provides a fine sand body characterization system based on the construction of an isochronous seismic stratigraphic framework, including:

[0032] An identification module, which is used to identify the correlation marker bed by using the variation laws of lithology and electric property;

[0033] An isochronous seismic stratigraphic framework construction module, which is used to carry out synthetic seismogram calibration by using the reflection characteristics of the correlation marker bed in the 3D seismic profile and construct an isochronous seismic stratigraphic framework;

[0034] A sand body response characteristic obtaining module, which is used to sort out the seismic response characteristics of the sand body and obtain the sand body response characteristics by means of the counter-evidence of the forward model and the identification of special geological bodies within the isochronous seismic stratigraphic framework;

[0035] The module for describing the macroscopic distribution of sand bodies is used to predict reservoirs based on the response characteristics of sand bodies and amplitude threshold values ​​using several seismic methods to describe the macroscopic distribution of sand bodies.

[0036] The module for finely depicting the sand body distribution morphology uses dynamic and static data to determine the connectivity of the sand bodies and finely depict the sand body distribution morphology;

[0037] The acquisition module is used to obtain the target sand body distribution morphology and target sand body characteristics based on the macroscopic distribution law of the sand body and finely characterize the sand body distribution morphology, and complete the fine characterization of the sand body.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention provides a method for fine characterization of sand bodies based on isochronal seismic stratigraphic framework, which fills the gap in the research method of fine characterization of continental river sand bodies in piedmont condensate gas reservoirs. It adopts a method combining dynamic and static, well and seismic, and jointly tackles the problem of determining the planar distribution law of complex continental river sand bodies in piedmont. This method can more accurately carry out stratigraphic division and comparison in the piedmont sand-mudstone interlayer sedimentary environment and analyze the vertical and horizontal distribution law of continental river sand bodies, avoid the technical problem of large dynamic and static contradictions in the sand body characterization process, and accurately characterize the connectivity and gas-water distribution characteristics inside the sand body. On this basis, we can re-understand the gas reservoir type, optimize the rolling target, and effectively guide the research on rolling deployment of gas reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a comparative diagram of the Kekeyaxihefu Formation X3-X8 stratigraphic layers according to an embodiment of the present invention;

[0041] Figure 2 This is a seismic profile diagram of pre-stack depth-to-time domain conversion through K201-K7006 well connection calibration in an embodiment of the present invention;

[0042] Figure 3 A multi-method reservoir prediction plane diagram of the Xihefu Formation in the Kekeya structural belt according to an embodiment of the present invention;

[0043] Figure 4 Kekeya gas field X7 of the embodiment of the present invention 2 Plane distribution map of main sand bodies of gas formation group;

[0044] Figure 5 A method flow chart of a sand body fine characterization method based on isochronal seismic stratigraphic framework construction according to an embodiment of the present invention;

[0045] Figure 6 The invention discloses a sand body fine characterization system based on an isochronal seismic stratigraphic framework according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0048] The present invention provides a method and system for fine characterization of sand bodies based on the construction of an isochronal seismic stratigraphic framework. The method adopts a combination of well-seismic and static methods to carry out fine characterization of sand bodies under the construction of an isochronal seismic stratigraphic framework, and then determines the research concept of gas reservoir type, thus forming a set of research methods suitable for fine characterization of sand bodies in complex terrestrial river channels in front of mountains.

[0049] The above-mentioned sand body fine characterization method based on isochronal seismic stratigraphic framework construction includes the following steps:

[0050] S1: Identify the contrast marker layer by using the lithology and electrical property change rules;

[0051] Specifically based on the above technical solution, S1 includes the following steps:

[0052] S11: Based on the laws of lithology and electrical property changes, the resistivity and natural potential curves are identified to obtain lithology and sedimentary cycle structure;

[0053] S12: Obtaining comparative marker layers based on lithology and sedimentary cycle structure;

[0054] S2: Use the contrast marker layer to reflect the characteristics in the 3D seismic profile, carry out synthetic record calibration, and build an isochronal seismic stratigraphic framework;

[0055] Specifically based on the above technical solution, S2 includes the following steps:

[0056] Using the lithological changes of the contrast marker beds to reflect characteristics in the 3D seismic profile, synthetic seismogram calibration is carried out. The top layer of the sedimentary positive cycle and the bottom layer of the sedimentary negative cycle are strong wave peak reflections, and the top layer of the sedimentary negative cycle is the zero phase of strong wave trough and wave peak;

[0057] An isochronous seismic stratigraphic framework is built, and within it, the variation law of reflection isochrones is used to guide the subdivision of small layers and the delineation of sand bodies in the sandstone-mudstone interbedded sedimentary environment. Among them, an isochronous reflection interface represents a geological interface or sedimentary unit.

[0058] S3: Within the isochronous seismic stratigraphic framework, through the refutation of the forward model and the identification of special geological bodies, the seismic response characteristics of sand bodies are sorted out to obtain the sand body response characteristics;

[0059] S4: Based on the sand body response characteristics and the amplitude threshold value of -2200, several seismic methods are used for reservoir prediction to delineate the macroscopic distribution law of sand bodies;

[0060] S5: Using dynamic and static data, judge the connectivity of sand bodies and finely delineate the distribution pattern of sand bodies;

[0061] Specifically, based on the above technical solutions, the judgment conditions for the connectivity of sand bodies are as follows:

[0062] It conforms to the regional climate, facies belt characteristics and provenance development direction, and follows the sedimentation law that the single sand body has a large thickness, good connectivity in the provenance direction along the river channel, a thin single sand body, and a short extension distance in the direction perpendicular to the river channel provenance; and using the contrast marker beds or auxiliary marker beds within the small layer, under the control of horizons, the principle of equivalent horizons, the same lithology, similar electric properties, similar fluids and consistent structures is used to judge the connectivity of sand bodies.

[0063] S6: Based on the macroscopic distribution law of sand bodies and the finely delineated sand body distribution pattern, obtain the target sand body distribution pattern and target sand body characteristics to complete the fine delineation of sand bodies.

[0064] In the specific implementation process, the sedimentary cycle includes sedimentary positive cycle and sedimentary negative cycle; the contrast marker bed is the sedimentary transition, and more specifically, the contrast marker bed includes the top layer of the sedimentary positive cycle, the top layer of the sedimentary negative cycle and the bottom layer of the sedimentary negative cycle.

[0065] In the specific implementation process, the seismic response characteristics of the target sand body include sandstone response characteristics and mudstone response characteristics; the sandstone response characteristics are a set of strong reflection wave trough characteristics, and the mudstone response characteristics are a set of strong reflection wave peak characteristics.

[0066] In the specific implementation process, the geological phenomena for the identification of special geological bodies include: the geological phenomenon that the amplitude of the in-phase axis corresponding to the reservoir thickness decreasing from thick to thin will change from strong to weak, the geological phenomenon that the in-phase axis corresponding to the non-connected reservoir shows dislocation, and the geological phenomenon that the in-phase axis will be distorted corresponding to the phase change of sandstone and mudstone.

[0067] In the specific implementation process, when it is higher than the amplitude threshold value, the sand body is not developed; when it is lower than the amplitude threshold value, the sand body is developed.

[0068] In the specific implementation process, several seismic methods include wave impedance inversion method, conventional amplitude method, root mean square amplitude method after wavelet reconstruction, and high-precision reservoir inversion method.

[0069] Based on the above technical solutions of the present invention, it further includes recognizing the gas reservoir type based on the distribution pattern and characteristics of the target sand body to select the rolling target of the gas reservoir. Through the above technical solutions, the rolling deployment research of the gas reservoir can be effectively guided.

[0070] The present invention also provides a fine sand body characterization system based on the construction of an isochronous seismic stratigraphic framework, including an identification module, an isochronous seismic stratigraphic framework construction module, a sand body response feature acquisition module, a macroscopic sand body distribution law characterization module, a fine sand body distribution pattern characterization module, and an acquisition module:

[0071] The identification module is used to identify and contrast marker beds by using the lithology and electrical property variation laws;

[0072] The isochronous seismic stratigraphic framework construction module is used to carry out synthetic seismogram calibration by using the characteristics reflected by the marker beds in the three-dimensional seismic profile and construct an isochronous seismic stratigraphic framework;

[0073] The sand body response feature acquisition module is used to sort out the response characteristics of the sand body on the seismic by means of the counter-evidence of the forward model and the identification of special geological bodies within the isochronous seismic stratigraphic framework and obtain the sand body response characteristics;

[0074] The macroscopic sand body distribution law characterization module is used to predict the reservoir by using several seismic methods based on the sand body response characteristics and the amplitude threshold value and characterize the macroscopic sand body distribution law;

[0075] The fine sand body distribution pattern characterization module uses dynamic and static data to judge the connectivity relationship of the sand body and finely characterize the sand body distribution pattern;

[0076] The acquisition module is used to obtain the target sand body distribution pattern and target sand body characteristics based on the macroscopic sand body distribution law and the fine sand body distribution pattern characterization to complete the fine sand body characterization.

[0077] Embodiment

[0078] See Figure 5, this embodiment provides a method for fine characterization of sand bodies based on the construction of an isochronous seismic stratigraphic framework. The specific implementation steps are as follows:

[0079] Step 1: Identify and correlate marker beds using the variation laws of lithology and electric properties.

[0080] Step 2: Use the reflection characteristics of marker beds in 3D seismic profiles to carry out synthetic seismogram calibration and construct an isochronous seismic stratigraphic framework.

[0081] Step 3: Within the isochronous seismic stratigraphic framework, through the refutation of forward models and the identification of special geological bodies, sort out the seismic response characteristics of the target sand bodies in this area.

[0082] Step 4: Based on the sand body response characteristics and amplitude threshold values, use various seismic methods to carry out reservoir prediction and characterize the macroscopic distribution law of sand bodies.

[0083] Step 5: Use various dynamic and static data to judge the connectivity of sand bodies and finely characterize the distribution pattern of sand bodies.

[0084] Step 6: Comprehensively utilize the above results to carry out a re-understanding study of gas reservoir types and guide rolling deployment.

[0085] The following further describes this embodiment in detail with reference to the accompanying drawings:

[0086] To more specifically illustrate the purpose and advantages of the present invention, it is introduced in detail in combination with the accompanying drawings and technical flowcharts.

[0087] This embodiment uses the lower gas-bearing formation of the Neogene Xihefupu Formation in the Kekeya condensate gas field as the implementation area. The lower gas-bearing formation of the Neogene Xihefupu Formation in the Kekeya condensate gas field is significantly affected by seasonal floods, with rapid river channel migration, multiple stages of river channel superimposition, strong reservoir heterogeneity, complex gas-water relationships, and is a typical continental braided river channel sedimentary system. During the development process, the following phenomena are often encountered: for the same structure and the same sand body, there is oil and gas in the low position, while there is water in the high position, or among multiple river channel sand bodies deposited during the same period, some contain oil and gas, while some do not. The same sand body has different oil and gas-bearing properties, which are not only controlled by reservoir diagenesis, clay type and heterogeneity, but also closely related to the planar connectivity of the sand body.

[0088] The specific method for fine characterization of sand bodies based on the construction of an isochronous seismic stratigraphic framework is as follows:

[0089] Step 1: Identify and correlate marker beds using the variation laws of lithology and electric properties.

[0090] As Figure 1 shown, there are certain regularities in the vertical variation of lithology and electric properties in the Xihefupu Formation. The resistivity and spontaneous potential curves are the most obvious for identifying lithology and sedimentary cycles.

[0091] The section from X6 to X4 shows a positive sedimentary cycle, while the section from X6 to X8 shows a negative sedimentary cycle. Vertically, they form a complete sedimentary cycle structure of "fine - coarse - fine" from X8 to X4. Among them, the tops of X4, X7, and X9 are three sets of stable marker beds: above the boundary of the top of X4, a set of fine sandstones with a thickness of 20 - 30 meters develops, and below the boundary, it is mainly mudstone; above the boundary of the top of X7, thick - layer sandstones develop, and below the boundary, the sand - to - ground ratio decreases and it turns into sand - surrounded - by - mud deposition; above the boundary of the top of X9, sand layers develop, and below the boundary, a thick - layer large - scale mudstone section develops.

[0092] Overall, the sedimentary evolution of the Xihefu Formation shows a process of continuous shrinkage of the lake towards the center of the sag from bottom to top, mainly experiencing the evolution process from the lakeshore facies, delta facies to meandering river and braided river.

[0093] Therefore, all three sets of marker beds are large sedimentary transformation surfaces.

[0094] Step 2: Utilize the reflection characteristics of the contrast marker beds in the 3D seismic profile, conduct synthetic seismogram calibration, and establish an isochronous seismic stratigraphic framework.

[0095] As Figure 2 shown, at the sedimentary interface transition, the sedimentary lithology changes sharply, which is reflected to a certain extent on the 3D seismic profile. Using multiple wells to conduct acoustic synthetic seismogram calibration, the tops of X4 and X9 show strong wave - peak reflections, with good continuity across the whole area and being easy to trace and contrast; the top of X7 shows the zero - phase of a strong wave - trough and wave - peak, with relatively good continuity.

[0096] Thus, the isochronous stratigraphic framework of X7 - X9 has been clarified. Inside it, the variation law of reflection isochrons is used to guide the subdivision of small layers and the delineation of sand bodies in the sand - shale interbedded sedimentary environment. An isochronous reflection interface represents a geological interface or sedimentary unit, which is more in line with the principles of sequence stratigraphy, and the delineation results are more scientific and reasonable.

[0097] Step 3: Within the isochronous seismic stratigraphic framework, through the refutation of the forward model and the identification of special geological bodies, sort out the seismic response characteristics of the target sand bodies in this area.

[0098] First of all, through the refutation of the forward model and the identification of special geological bodies, sort out and clarify the seismic response characteristics of the target sand bodies in this area. Based on fine well - seismic calibration, it can be judged that the response characteristic of sandstone is a set of strong - reflection wave - troughs, and the response characteristic of mudstone is a set of strong - reflection wave - peaks. After establishing the forward model, the reflected response characteristics are basically consistent with the judgment rules after well - seismic calibration, that is, the sandstone strip shows the wave - trough characteristic.

[0099] In addition, the forward - modeling law also shows that the thicker the sand body, the stronger the reflection of the isochron. The forward - modeling law also provides a basis for clarifying the seismic response characteristics.

[0100] In addition to the response characteristics of conventional sand-mud variations, the interpretation of special geological phenomena in seismic profiles is also one of the important bases for reservoir prediction. A total of 3 types of special geological phenomena were sorted out this time: 1. When the reservoir thickness decreases from thick to thin, the amplitude of the corresponding in-phase axis will change from strong to weak; 2. Phase transformation between sandstone and mudstone, and the corresponding in-phase axis may be distorted; 3. Disconnected reservoirs, and the corresponding in-phase axis shows a fault.

[0101] Step 4: Based on the sand body response characteristics and amplitude threshold values, use a variety of seismic methods to carry out reservoir prediction and depict the macroscopic distribution law of sand bodies.

[0102] Based on the sand body response characteristics and amplitude threshold values (by statistically analyzing the maximum trough amplitude energy of 35 wells in the study area, the threshold value of the maximum trough amplitude energy of favorable sand bodies is -2200. If it is higher than the threshold value, favorable sand bodies are basically not developed, and if it is lower than the threshold value, favorable sand bodies are developed), as Figure 3 shown, four methods including wave impedance inversion, conventional amplitude, root mean square amplitude after wavelet reconstruction, and high-precision reservoir inversion were respectively used for reservoir prediction.

[0103] Through comparison, it is found that the root mean square amplitude after wavelet reconstruction and high-precision reservoir inversion have better effects: among them, the reservoir prediction after wavelet reconstruction is more prominent in depicting the details of sand bodies, and the high-precision reservoir inversion reflects the sand bodies and their distribution laws more clearly on the plane. After further comparison, it is found that the sand body morphology in the high-precision reservoir inversion results is more similar to the underwater distributary channels of braided river deltas in the sedimentary background of the zone.

[0104] Step 5: Use various dynamic and static data to judge the connectivity relationship of sand bodies and finely depict the distribution pattern of sand bodies.

[0105] First, make a preliminary judgment based on the characteristics of rock-electric combination and sedimentary cycle characteristics, and then finally make an accurate judgment by comprehensively using single-well test data (pressure measurement, logging, oil testing, etc.) or actual production dynamic data. Taking the typical wells K11 well and K24 well as examples, the structural position of K11 well is lower than that of K24 well. In 1982, the entire well section of the X72 gas reservoir group in K11 well was tested for oil, and all were water layers. K24 well was put into production in May 1992. Initially, 7 small layers were opened, showing the production dynamic characteristics of edge water advance. From this, it is judged that the sand bodies of the 7 small layers of the two are connected. In April 2002, the 7 small layers were plugged, and production was resumed from the 2nd to the 6th small layers. So far, no water has been seen, from which it is judged that the sand bodies of the 2nd to the 6th small layers of the two are not connected.

[0106] In the absence of dynamic data verification, the connectivity analysis of small-layer sand bodies should be consistent with the regional climate, phase belt characteristics and provenance development direction, and follow the sedimentary laws such as large single sand body thickness, good connectivity along the river source direction, thin single sand body thickness, and short extension distance in the direction of vertical river source. The connectivity of sand bodies can also be judged by using the comparative marker layer or auxiliary marker layer inside the small layer under the control of the stratigraphic position, adopting the principle of "equivalent stratigraphic position, same lithology, similar electrical properties, similar fluids, and consistent structures".

[0107] Take the typical wells KS103 and K50 as examples. The 7-layer sand bodies of these two wells are at the same level and have the same lithology, but the fluid properties do not match the structural position. In June 1993, the 7-layer oil test of the K50 well produced 9.5m3 of water per day, and the oil test concluded that it was a water layer. In January 2004, the electrical test of the KS103 well showed that the resistivity value of the 7-layer sand body was 5.8Ω·m, and the conclusion was that it was an oil and gas layer. However, the structural position of the K50 well is higher than that of the KS103 well, so it is judged that the 7-layer sand bodies of the two wells are not connected.

[0108] Step 6: Comprehensively utilize the above results to conduct research on re-understanding of gas reservoir types and guide rolling deployment.

[0109] In the early days, it was believed that the X72 sand bodies were distributed in a continuous manner, with good connectivity, and the gas reservoir type was controlled by the structure. Based on the above method, the single sand body distribution morphology and characteristics of the X72 gas layer group were re-detailed, which is quite different from the early understanding. Under the joint control of the continuous lateral swing of multi-stage sedimentary channels and the vertical deposition and erosion, the single sand body is distributed very complexly in the plane, with bean-shaped, lens-shaped, irregular, strip-shaped and sheet-shaped distribution; but in general, due to the influence of the southern source, most of the sand bodies are distributed in strips in the north-south direction ( Figure 4 ), which is a condensate gas reservoir with oil ring controlled by both structure and lithology, and has the characteristics of "one sand and one reservoir", so the sand body outside the structure has the conditions for rolling deployment.

[0110] This embodiment uses a combination of well-seismic and static methods to carry out fine characterization of sand bodies under the construction of an isochronous seismic stratigraphic framework, and then determines the research concept of the gas reservoir type, forming a set of research methods suitable for fine characterization of complex terrestrial river channel sand bodies in front of mountains. This method not only successfully promoted the revolutionary transformation of the gas reservoir type from "structural control" to "lithological-structural control" in the lower gas layer group of a certain gas field, and completely solved the problems of uncertain sand body distribution and contradictory fluid relationships for decades, but also promoted the drilling of 5 rolling evaluation wells on the periphery of the lower gas layer group, and all 5 wells were successful, successfully reversing the situation of continuous decline in the production of the experimental gas field and realizing efficient development. This method not only provides effective ideas and methods for the study of complex terrestrial river channel sand body gas reservoirs in front of mountains, but also can provide reliable research ideas for similar gas reservoir development research at home and abroad.

[0111] See alsoFigure 6 , in another embodiment of the present invention, a fine sand body characterization system based on the construction of an isochronous seismic stratigraphic framework is provided, which can be used to implement the above-mentioned fine sand body characterization method based on the construction of an isochronous seismic stratigraphic framework. Specifically, the system includes an identification module, an isochronous seismic stratigraphic framework construction module, a sand body response feature acquisition module, a macroscopic sand body distribution law characterization module, a fine sand body distribution pattern characterization module, and an acquisition module.

[0112] Among them, the identification module is used to identify and compare marker beds by using the laws of lithology and electrical property changes;

[0113] The isochronous seismic stratigraphic framework construction module is used to carry out synthetic seismogram calibration by using the reflection characteristics of the marker bed in the 3D seismic profile and construct an isochronous seismic stratigraphic framework;

[0114] The sand body response feature acquisition module is used to sort out the seismic response characteristics of the sand body and obtain the sand body response features within the isochronous seismic stratigraphic framework through the refutation of the forward model and the identification of special geological bodies;

[0115] The macroscopic sand body distribution law characterization module is used to predict the reservoir by using several seismic methods based on the sand body response characteristics and the amplitude threshold value, and characterize the macroscopic sand body distribution law;

[0116] The fine sand body distribution pattern characterization module uses dynamic and static data to judge the connectivity relationship of the sand body and finely characterize the sand body distribution pattern;

[0117] The acquisition module is used to obtain the target sand body distribution pattern and target sand body characteristics based on the macroscopic sand body distribution law and the fine sand body distribution pattern characterization, and complete the fine sand body characterization.

[0118] All relevant contents of each step involved in the embodiment of the foregoing fine sand body characterization method based on the construction of an isochronous seismic stratigraphic framework can be cited in the function description of the corresponding functional modules of the fine sand body characterization system based on the construction of an isochronous seismic stratigraphic framework in the embodiment of the present invention, and will not be elaborated here.

[0119] The division of modules in the embodiment of the present invention is illustrative, only a logical function division. In actual implementation, there may be other division methods. In addition, in each embodiment of the present invention, each functional module can be integrated in one processor, or can exist separately physically, or two or more modules can be integrated in one module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework, characterized in that, It includes the following steps: S1: Identify and correlate marker beds by using the variation laws of lithology and electric property; S2: Utilize the reflection characteristics of the marker beds in the 3D seismic profile, conduct synthetic seismogram calibration, and establish an isochronous seismic stratigraphic framework; S3: Within the isochronous seismic stratigraphic framework, through the refutation of the forward model and the identification of special geological bodies, sort out the seismic response characteristics of sand bodies to obtain the sand body response characteristics; S4: Based on the sand body response characteristics and the amplitude threshold value, adopt several seismic methods for reservoir prediction to depict the macroscopic distribution law of sand bodies; S5: Use dynamic and static data to judge the connectivity of sand bodies and finely depict the distribution pattern of sand bodies; S6: Based on the macroscopic distribution law of sand bodies and the finely depicted distribution pattern of sand bodies, obtain the distribution pattern and characteristics of target sand bodies, and complete the fine characterization of sand bodies.

2. The fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework according to claim 1, wherein In the above S1, identifying and correlating marker beds by using the variation laws of lithology and electric property includes the following steps: S11: Identify the resistivity and spontaneous potential curves based on the variation laws of lithology and electric property to obtain lithology and sedimentary cycle structure; S12: Obtain marker beds based on lithology and sedimentary cycle structure; The sedimentary cycle includes positive sedimentary cycle and reverse sedimentary cycle; the marker bed is the sedimentary transition point.

3. The fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework according to claim 2, wherein The marker beds include the top layer of the positive sedimentary cycle, the top layer of the reverse sedimentary cycle, and the bottom layer of the reverse sedimentary cycle.

4. The fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework according to claim 3, characterized in that, In the above S2, the process of utilizing the reflection characteristics of the marker beds in the 3D seismic profile, conducting synthetic seismogram calibration, and establishing an isochronous seismic stratigraphic framework is as follows: Utilize the lithology change of the marker beds to reflect characteristics in the 3D seismic profile and conduct synthetic seismogram calibration. The top layer of the positive sedimentary cycle and the bottom layer of the reverse sedimentary cycle are strong wave peak reflections, and the top layer of the reverse sedimentary cycle is the zero phase of strong wave trough and wave peak; Establish an isochronous seismic stratigraphic framework, and within it, use the variation law of reflection event to guide the subdivision of sublayers and the characterization of sand bodies in the sandstone-mudstone interbedded sedimentary environment. Among them, an isochronous reflection interface represents a geological interface or sedimentary unit.

5. The fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework according to claim 4, characterized in that, In the above S3, the seismic response characteristics of the target sand bodies include sandstone response characteristics and mudstone response characteristics; The sandstone response characteristics are a set of strong reflection wave trough characteristics, and the mudstone response characteristics are a set of strong reflection wave peak characteristics.

6. The fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework according to claim 4, characterized in that In the above S3, the geological phenomena for the identification of special geological bodies include: The geological phenomena that the amplitude of the event corresponding to the thickening-thinning of the reservoir will change from strong to weak, the event corresponding to the non-connectivity of the reservoir shows dislocation, and the phase change of sandstone and mudstone corresponds to the distortion of the event.

7. The fine sand body characterization method based on the construction of an isochronous seismic stratigraphic framework according to claim 1, wherein In the above S4, the amplitude threshold value is -2200; when it is higher than the amplitude threshold value, sand bodies are not developed, and when it is lower than the amplitude threshold value, sand bodies are developed; The several seismic methods include wave impedance inversion method, conventional amplitude method, root mean square amplitude method after wavelet reconstruction, and high-precision reservoir inversion method.

8. The fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework according to claim 1, wherein In the above S5, the judgment conditions for the connectivity of sand bodies are as follows: It conforms to the regional climate, facies belt characteristics and provenance development direction, follows the sedimentation law that the single sand body has a large thickness, good connectivity in the provenance direction along the river channel, a thin single sand body thickness, and a short extension distance in the direction perpendicular to the river channel provenance; and uses the correlation marker beds or auxiliary marker beds within the sub-layer to control the layer position, and adopts the principle of equivalent layer position, same lithology, similar electrical properties, similar fluids, and consistent structure to judge the connectivity relationship of the sand bodies.

9. The fine characterization method of sand bodies based on the construction of an isochronous seismic stratigraphic framework according to claim 1, wherein It also includes recognizing the gas reservoir type based on the distribution pattern and characteristics of the target sand body to select the rolling target of the gas reservoir.

10. A fine sand body characterization system based on the construction of an isochronous seismic stratigraphic framework, characterized in that, It includes: An identification module for identifying correlation marker beds by using the variation laws of lithology and electrical properties; An isochronous seismic stratigraphic framework building module for carrying out synthetic seismogram calibration by using the reflection characteristics of the correlation marker beds in the 3D seismic profile and building an isochronous seismic stratigraphic framework; A sand body response characteristic obtaining module for sorting out the seismic response characteristics of the sand bodies and obtaining the sand body response characteristics through the refutation of the forward model and the identification of special geological bodies within the isochronous seismic stratigraphic framework; A sand body macroscopic distribution law depicting module for predicting the reservoir by using several seismic methods based on the sand body response characteristics and amplitude threshold value and depicting the macroscopic distribution law of the sand bodies; A sand body distribution pattern finely depicting module for judging the connectivity relationship of the sand bodies by using dynamic and static data and finely depicting the distribution pattern of the sand bodies; An obtaining module for obtaining the distribution pattern and characteristics of the target sand body based on the macroscopic distribution law of the sand bodies and the finely depicted sand body distribution pattern to complete the fine depiction of the sand bodies.

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