CN117233830A - Method for eliminating paste salt layer based on model forward modeling - Google Patents
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Abstract
The invention discloses a method for removing a paste salt layer based on model forward modeling, which relates to the technical field of petroleum and natural gas seismic exploration and comprises a data preparation step, a lithology calculation step, a model design step, a model forward modeling step, a matching comparison step and a planar lithology spread analysis step. The invention utilizes the speed and density of the actual drilling and logging data to manufacture forward geologic models, obtains different forward results by continuously adjusting the parameters related to the models, then carries out matching comparison on the forward results and the actual seismic data to determine the seismic reflection characteristics of different lithology or lithology combinations, and predicts the spreading rules of the different lithology by combining with the analysis of the amplitude attribute. The method fully utilizes the data of actual drilling and logging to simulate the reflection characteristics of different lithologies, and the obtained result accords with the geological law. The invention utilizes the forward modeling of the model to simulate the seismic reflection characteristics of different lithology and lithology combinations, and can make up the defect of people on the propagation rule of seismic waves in complex media.
Description
Technical Field
The invention relates to the technical field of petroleum and natural gas seismic exploration, in particular to a method for removing a paste salt layer based on model forward modeling.
Background
The underground three-fold system of Sichuan basin is one of important natural gas production layers, and well developed reservoirs are arranged in the Jiangjiang group. The reservoir is mainly located in Jia two 2 The lithology of the upper part of the subsection is mainly cloud rock. Jia Er (Jia Er) 2 The thickness of the sub-section stratum is about 50m, the lithology of the sub-section stratum is mainly limestone, cream salt and Yun Yan from bottom to top, and the thickness of each lithology has certain change. Jia Er (Jia Er) 1 The sub stratum also develops a thin reservoir layer with a thickness of about 25m and an upper part of the reservoir layer isA set of cream rocks, the lower part of which is mainly cloud rocks, as shown in figure 2.
The lithology of the interval of interest is relatively complex, there are layers of paste salts, cloud strata, paste salts and Yun Yanbao interbedds, and the reservoir mainly develops inside the cloud strata. Because the speed of the salt layer is not greatly different from the speed of the reservoir section (the propagation speed of the manually excited seismic waves in the stratum, hereinafter referred to as speed), the prediction of scientific researchers is greatly interfered, and the accuracy of reservoir prediction is affected. How to accurately sum up the seismic reflection characteristics of the reservoir and the paste salt layer on the seismic section, so that the paste salt layer and the reservoir can be effectively identified, and the method is an important point for reservoir prediction of the Jiang river group.
In the prior art, a patent with publication number of CN106353808B discloses a method and a device for analyzing the time pulling law of the seismic reflection of an underlying horizon, wherein the method comprises the following steps: establishing a generalized lifting model of a calculation model of lifting amplitude change of an underlying seismic reflection layer caused by a salt-gypsum rock abnormal speed interlayer; and analyzing the lifting rule of the seismic reflection time of the underlying layer under the influence of the salt-gypsum abnormal speed layer according to a generalized lifting model of a calculation model of the lifting amplitude change of the underlying seismic reflection layer caused by the salt-gypsum abnormal speed interlayer. According to the technical scheme, a typical model which accords with an actual structure is built through forward modeling of a simple geological model, influences of different thickness combinations of salt rock and gypsum on an underlying target layer imaging are researched, seismic response characteristics corresponding to different conditions of the salt rock are researched in a gypsum layer under the right bank of America, pre-stack speed analysis is facilitated, and influences of post-stack corrected salt gypsum speed change on seismic reflection time of the underlying carbonate rock target layer are easier to learn.
However, the method provided by the above patent is not suitable for identifying normal paste salt layers and rejecting paste salt layers, i.e. paste salt layers and reservoirs cannot be effectively identified to improve the accuracy of reservoir prediction.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention discloses a method for removing a paste salt layer based on model forward modeling, and aims to solve the problem that the paste salt layer and a reservoir layer cannot be effectively identified in the prior art.
In order to achieve the above purpose, the present invention adopts the technical scheme that:
the method for eliminating the paste salt layer based on the model forward modeling comprises a data preparation step, a lithology calculation step, a model design step, a model forward modeling step, a matching comparison step and a planar lithology spread analysis step, and specifically comprises the following steps:
s1, data preparation
The data preparation step prepares basic data including drilling data, lithology data, logging data, and pre-stack time migration data.
In the above steps, the drilling data is used for subsequent lithology calculation and model design, the lithology data is used for subsequent S2 various lithology calculation and S3 model design, the logging data is used for subsequent S2 step to calculate thickness, speed and density values of different lithology, and the prestack time migration data is used for subsequent S5 step to determine the contrast analysis of the seismic reflection characteristics of different lithology or lithology combination.
Specifically, the drilling data comprise drilling coordinates, heart tonifying elevation, well deviation data and well position layering, the lithology data comprise main purpose interval lithology data, and the logging data comprise acoustic time difference, density, porosity, gamma and the like.
In the above steps, the drilling data, lithology data and logging data are obtained according to the drilling logging data, well completion geological report or logging (logging) report obtained by drilling in the research area and the adjacent area, such as drilling coordinates, heart tonifying altitude, geology (logging layering), rock debris data, well deviation data and comprehensive interpretation results (acoustic time difference, gamma curve, density curve, porosity curve and the like) of the main objective layer logging.
Preferably, in the data preparation step, seismic data of a research area are obtained through geophysical exploration, the difference of elasticity and density of underground media is utilized, the response of each stratum to manually excited seismic waves is observed and analyzed, and the pre-stack time migration data are obtained through processing of indoor computer professional software.
In the invention, for pre-stack time migration data, seismic data of a research area is obtained through geophysical exploration, and the seismic data is obtained through data processing by indoor professional software, namely, the pre-stack time migration data is obtained by observing and analyzing the response of the earth to manually excited seismic waves by utilizing the difference of elasticity and density of underground media. The indoor pre-stack time migration processing of the outdoor seismic data is one of the most effective methods for imaging the underground complex structure, is suitable for the condition that the propagation speed of longitudinal and transverse seismic waves in each stratum is greatly changed, and is suitable for migration imaging of the complex structure.
S2, lithology calculation
And the lithology calculation step is to calculate and obtain thickness, speed and density values of different lithology rock strata by using drilling and logging data.
In the above steps, the method for calculating the rock stratum thickness comprises the following steps:
s211, counting the thickness of each section and each sub-section stratum of each well by using prepared drilling and logging data, and obtaining the average value of the thickness of each section and each sub-section stratum as the thickness of each section and each sub-section stratum of the stratum.
In the method, the collected logging data of each well are utilized to count the thickness of stratum of Jia two and one (sub) sections, and an average value of each well is taken to design an initial model. Since the Jiang river group belongs to the sea-phase carbonate stratum, the stratum thickness of each (sub) section in the transverse direction is relatively stable, and the stratum thickness of each (sub) section of the initial model is consistent.
S212, counting the rock stratum thickness of different lithologies in each section and each sub-section stratum of each well, and obtaining an average value of the rock stratum thickness of different lithologies in each section and each sub-section stratum as the thickness of different lithologies in each section and each sub-section stratum of the rock stratum to carry out lithology filling on the model.
In the above method, the thickness of different lithologies may vary somewhat in the lateral direction due to subtle differences in the depositional environment. And (3) calculating the thicknesses of different lithologies in each section of each well in the region, and designing to obtain the thicknesses of different lithologies in each section (sub).
In the above steps, the method for calculating the rock stratum speed comprises the following steps: in the well logging data, analyzing a well diameter curve, removing a collapsed section part of the well diameter curve, and then in the well logging data after removing the collapsed section part, taking acoustic wave curves of different lithology sections of each well, and calculating acoustic wave average speeds of different lithology of each well to be used as speeds of rock formations of different lithology.
In the method, the collected logging data are utilized to obtain acoustic wave curves (speeds) of different lithology (gypsum salt, limestone and Yun Yan) sections of each well, and the average speeds of the different lithology of each well are calculated.
In the above steps, the method for calculating the formation density includes: in the well logging data, analyzing a well diameter curve, removing a collapsed section part of the well diameter curve, and then in the well logging data after removing the collapsed section part, taking a density curve of different lithology sections of each well, and calculating the average density of different lithology sections of each well to be used as the density of rock stratum of different lithology.
In the method, the collected logging data are utilized to obtain the density curves of different lithology (gypsum salt, limestone and Yun Yan) sections of each well, and the average density of the different lithology of each well is calculated.
In the invention, the lithology of the Jia two sections in the longitudinal and transverse directions is complex, the lithology speed and the lithology density are different, and the average value of the speeds and the densities of the different lithology sections is obtained by analyzing a logging curve. Firstly, analyzing a well diameter curve, removing a part with a collapsed section of the well diameter curve, and ensuring the accuracy of speed and density values.
According to the invention, through analyzing the rock electric characteristics of the coring well, the lithology of the two sections of the Jiang river is complex in the longitudinal direction, the electric characteristics of different lithology sections are greatly different from each other in the layers of the cream rock, the Yun Yan and the limestone, and the distinction degree of the interlayer cream salt and the reservoir rock Yun Yan on the response of the density curve is most obvious.
In the invention, as the rock electricity corresponding relation of the coring well is good, the logging curves corresponding to different lithology can be marked in software, and the average value of the logging curves can be automatically calculated. Wherein the velocity of the gypsum is about 5500m/s, the density is 2.88g/cc, and the impedance value is 16700 m/s; about 6000m/s of limestone, 2.78g/cc of density and 16680m/s of impedance value; while Yun Yan has a speed of about 6300m/s, a density of 2.82g/cc and an impedance value of 17200 m/s.
In an open hole well, as the stratum is washed and soaked by drilling fluid, the phenomenon that the drilling fluid invades or dissolves the stratum easily occurs in different lithology, and the like, the well diameter curve can be used for dividing and verifying. For more dense limestone and Yun Yan, the permeability is poorer, the hardness is harder, the well diameter is less affected, and the well diameter curve is almost unchanged; for paste salts, the well diameter is obviously enlarged, the well diameter curve is suddenly changed and a high value is displayed. The demarcation between the paste salt and the limestone Yun Yan can be finely delineated thereby.
S3, model design
And the model design step is to design a geological model by using the thickness, speed and density value information of different lithology rock layers and the drilling data.
Preferably, in the model designing step, the thickness information of rock formations with different lithology is utilized to draw a distribution characteristic model of the stratum; lithology changes of stratum of each section and each sub-section of the real well are utilized to determine lithology of the model; and setting each lithology and the speed and density of the reservoir section on the model, and unifying the model into a geological-physical model.
In the above steps, the geologic model is designed based on the result of geologic analysis of the well data. Firstly, the stratum thickness of Jia two and one (sub) sections and the stratum thickness of a reservoir section are counted through real drilling in the region, and if the stratum thickness of the well in which the fault is drilled is abnormal, the stratum thickness is not selected. And secondly, determining lithology of the model according to lithology changes of each section (sub-section) of the real well drilling in the longitudinal and transverse directions, wherein the lithology changes are matched with those of the drilled well, and the obtained forward modeling result is closer to the reflection characteristics of the well-side seismic channel. After lithology and thickness determination, the velocity and density (velocity x density = wave impedance value) of each lithology and reservoir section are set by software, thereby deriving the wave impedance value for each lithology section within each section (sub-section).
In the invention, a geological model is key, and the geological model is designed according to thickness, speed and density information of a real stratum reservoir section and a paste salt layer obtained according to logging data. The side of the well is set according to the thickness, speed and density information of actual well drilling and well logging, the thickness between wells is set into a wedge shape when the lithology changes, and the thickness between wells is set into a horizontal lamellar shape when the lithology does not change. Because of the differences in lithology thickness of different sedimentary facies in different zones, the lithology thickness of the model must be determined according to the results of actual drilling and logging.
And (3) designing a geological model by using the thickness, speed and density value information obtained in the step S2 and the drilling data in the step S1, namely combining the thickness and lithology change of each section (sub-section) of the real drilling Jiangjiang group.
S4, model forward modeling
And the model forward modeling step is used for modeling forward modeling the geological model by adopting a wave equation forward modeling method, and simulating seismic wave propagation characteristics under the conditions of different lithology, different speeds and different densities.
Preferably, in the model forward modeling step, forward modeling is performed on the geological model by simulating seismic waves in a wave equation mode, and a forward seismic section is obtained through calculation; the forward seismic section is obtained by using a synthetic seismic record, wherein the synthetic seismic record is equal to convolution of a seismic wavelet and a reflection coefficient, and the reflection coefficient is equal to a wave impedance value obtained by multiplying different rock stratum speeds and densities, and is converted into the reflection coefficient through a formula.
In the invention, after the geological model is designed, forward modeling is realized mainly through professional software, and seismic forward modeling is realized through physical modeling. According to the propagation principle of the seismic waves in the underground medium, the forward modeling calculates the seismic records of the established geological model through a wave equation forward modeling method. The forward modeling of geologic models is based on different formations having different velocities and densities, the product of which is the wave impedance. The difference in impedance between adjacent formation waves produces a reflection coefficient R. Assuming that the seismic wave is normally incident, the reflection coefficient for normal incidence can be calculated. In forward modeling, selecting an appropriate seismic wavelet is also a key to determine whether the final forward modeling result matches the actual seismic record. Rake wavelets (25 Hz) that are closer to the dominant frequency of the actual seismic data are typically selected for forward modeling.
Preferably, in the model forward modeling step, the model forward modeling is performed by using a Rake 25Hz wavelet. In the invention, a wave equation forward modeling method is adopted, and a Rake 25Hz wavelet which is relatively close to the main frequency of the seismic data is selected for model forward modeling, so that the purpose of accurately modeling the propagation characteristics of seismic waves under the conditions of different lithology, different speeds and different densities is achieved.
Wave equation forward is a method of modeling seismic reflection characteristics by means of an established geologic model, which can transform geologic phases into seismic phases. By deriving the thickness and location (depth) of the reservoir, a model of the formation's profile is plotted on the software. Giving the velocity and density values of different lithologies obtained by the previous step, unifying the velocity and density values into a geological-physical model, simulating earthquake waves by using 25HZ Rake wavelets with relatively close main frequency of earthquake data, and performing digital simulation calculation (software automatic calculation, a calculation theory method is that synthetic earthquake records are equal to convolution of the earthquake wavelets and reflection coefficients, wherein the reflection coefficients are equal to wave impedance values obtained by products of adjacent different rock stratum velocities and densities, and the wave impedance values are converted into the reflection coefficients through a formula), so that a corresponding forward earthquake section can be calculated.
S5, matching and comparing
And the matching comparison step is used for matching and comparing the forward result with the actual seismic data and correcting the forward result to determine the seismic reflection characteristics of different lithology or lithology combinations.
In the steps, the geological model is designed according to the layering, thickness, speed and density of real well drilling, and the selected Rake wavelets are close to the main frequency of the actual seismic data, so that the forward result of each well is basically consistent with the relation of the seismic reflection characteristics, amplitude and wave groups of the pre-stack time migration section beside the well. If the forward result and the actual seismic reflection characteristics, wave group relations and the like beside the well have obvious differences, the reasons should be analyzed, and the thickness of each stratum or lithology section of the model is properly modified, or the slightly modified speed and density values are considered until the forward result is more consistent with the seismic channels beside the well. And finally, analyzing whether the reflection characteristics of the top and bottom boundaries of the reservoir section in the forward result of real well drilling are consistent with the characteristics of the top and bottom boundaries of the reservoir of the actual well bypass, thereby obtaining an ideal forward result.
Preferably, in the matching comparison step, on the pre-stack time migration data body, the forward result and the actual seismic migration section are analyzed, and the wave group characteristics and the reflection energy intensity relations of Yun Yan and the paste salt section in the target interval are compared to determine the transverse comparison principle and characteristics.
In the invention, a transverse comparison principle refers to comparing seismic reflection event along a certain fixed geological interface, and is characterized by waveform, amplitude and energy, and the purpose of determining the transverse comparison principle and the characteristic is to accurately identify a certain geological reflection interface on a pre-stack time migration section for representing an underground geological structure, thereby realizing the structure and developing reservoir prediction work.
In the step, the forward-calculated waveform characteristic results of each reflection interface are applied to the comparison tracking of the actual seismic section horizon. The invention mainly aims at sea carbonate stratum, the sea sediment thickness is stable, so we refer to the four-bottom reflection (wave crest reflection, continuous phase axis and easy comparison and tracking) near the Jiang river group, and simultaneously combine the model forward modeling result to the Jiang two 3 Bottom and Jia two 2 The bottom is compared, and the reliability is high.
S6, plane lithology spread analysis
And the plane lithology spreading analysis step is used for extracting and analyzing the amplitude attribute of the seismic reflection characteristic of a certain interface to obtain a plane spreading graph of the full-area reservoir development area and the paste salt distribution area, and removing the paste salt distribution area to obtain the reservoir development area.
Preferably, in the step of analyzing the planar lithology spread, the attribute is an attribute representing amplitude information of the seismic data; in the planar layout, the strong amplitude region is a paste salt development region, and the weak amplitude region is a reservoir development region.
In the invention, the strong amplitude area corresponds to a paste salt development area, and the thicker the paste salt is, the stronger the amplitude is; the weak amplitude region is a region with thinner paste salt (non-development), namely a region with relative development of the reservoir.
The seismic attributes represent the morphology, the kinematic characteristics, the dynamic characteristics and the statistical characteristics of seismic waves, the reflection characteristics of the paste salt layer and the reservoir layer have larger difference in amplitude according to forward results, and the attributes representing the amplitude information of the seismic data are selected for analysis to obtain the plane layout diagram of the full-area reservoir development area and the paste salt distribution area, so that the reservoir development area is effectively judged.
In the invention, forward modeling results show that reflection characteristics of the paste salt layer and the reservoir have large differences in amplitude, so that the attribute of the amplitude information representing the seismic data is selected for analysis. The forward wave characteristics can be used for horizon comparison of an actual seismic section, and the obtained horizon data is used as the basis of a seismic attribute map.
In the invention, a time domain small stratum framework model is established by using well layering data and seismic horizon data, and an amplitude seismic phase plane graph (namely a plane layout graph) is drawn by extracting amplitude attributes from software. Further analysis and verification are carried out on the plane diagram interpreted by the earthquake phase, and cross verification is carried out by utilizing the azimuth of the seismic phase delineation and the paste salt distribution condition of the coring well. If inconsistent conditions exist, the tracking comparison of the seismic horizon is rechecked. The strong amplitude area on the seismic phase diagram is determined as a paste salt development area, and the determined paste salt distribution on a plane is determined.
The invention has the beneficial effects that:
the invention utilizes the speed and density of the actual drilling and logging data to manufacture forward geologic models, obtains different forward results by continuously adjusting the parameters related to the models, then carries out matching comparison on the forward results and the actual seismic data to determine the seismic reflection characteristics of different lithology or lithology combinations, and predicts the spreading rules of the different lithology by combining with the analysis of the amplitude attribute. The method fully utilizes the data of actual drilling and logging to simulate the reflection characteristics of different lithologies, and the obtained result accords with the geological law.
According to the invention, the model forward modeling is utilized to simulate the seismic reflection characteristics of different lithology and lithology combinations, so that the polynomials of the acquired information in the seismic data under the condition of complex medium can be reduced, and the reservoir can be effectively identified.
Drawings
FIG. 1 is a schematic illustration of the process of the present invention;
FIG. 2 is a synthetic histogram of Chuandong Jiang river group;
FIG. 3 is a graph of a Jiang river set log and lithology;
FIG. 4 is a Jiang river model and forward modeling result;
FIG. 5 is a well-tie offset section;
FIG. 6 is a plan view of a salt-paste development zone and a reservoir development zone.
Detailed Description
The conception, specific structure, and technical effects produced by the present invention will be clearly and completely described below with reference to the embodiments and the drawings to fully understand the objects, features, and effects of the present invention.
Example 1
A method for eliminating a paste salt layer based on model forward modeling, as shown in figure 1, comprises a data preparation step, a lithology calculation step, a model design step, a model forward modeling step, a matching comparison step and a planar lithology spread analysis step;
the data preparation step, preparing basic data including drilling data, lithology data, logging data and pre-stack time migration data;
the lithology calculating step calculates and obtains thickness, speed and density values of different lithology rock strata by using drilling and logging data;
the model design step utilizes thickness, speed and density value information of different lithology rock layers and the drilling data to design a geological model;
the model forward modeling step is used for modeling forward modeling the geological model by adopting a wave equation forward modeling method, and simulating seismic wave propagation characteristics under the conditions of different lithology, different speeds and different densities;
the matching comparison step is used for matching comparison and correction of forward results and actual seismic data, and determining seismic reflection characteristics of different lithology or lithology combinations;
and the plane lithology spread analysis step is used for extracting and analyzing the amplitude attribute of the seismic reflection characteristics to obtain a plane spread graph of the full-area reservoir development area and the paste salt distribution area, and removing the paste salt distribution area to obtain the reservoir development area.
In the method, forward geological models are manufactured by using the speed and the density of actual drilling and well logging data, different forward results are obtained by continuously adjusting the parameters related to the models, then the forward results are matched and compared with the actual seismic data to determine the seismic reflection characteristics of different lithology or lithology combinations, and then the amplitude attribute analysis is combined to predict the distribution rules of the different lithology. The method fully utilizes the data of actual drilling and logging to simulate the reflection characteristics of different lithologies, and the obtained result accords with the geological law. Meanwhile, the model forward modeling is utilized to simulate the seismic reflection characteristics of different lithology and lithology combinations, so that the defect of people on the propagation rule of the seismic waves in the complex medium can be overcome.
Example 2
This embodiment further describes the data preparation step based on embodiment 1. In the data preparation step, drilling data are used for subsequent lithology calculation and model design, lithology data are used for subsequent S2 various lithology calculation and S3 model design, logging data are used for subsequent S2 step to calculate thickness, speed and density values of different lithology, and prestack time migration data are used for subsequent S5 step to determine the contrast analysis of seismic reflection characteristics of different lithology or lithology combinations.
Specifically, the drilling data comprise drilling coordinates, heart tonifying elevation, well deviation data and well position layering, the lithology data comprise main purpose interval lithology data, and the logging data comprise acoustic time difference, density, porosity, gamma and the like.
In the above steps, the drilling data, lithology data and logging data are obtained according to the drilling logging data, well completion geological report or logging (logging) report obtained by drilling in the research area and the adjacent area, such as drilling coordinates, heart tonifying altitude, geology (logging layering), rock debris data, well deviation data and comprehensive interpretation results (acoustic time difference, gamma curve, density curve, porosity curve and the like) of the main objective layer logging.
In the data preparation step, seismic data of a research area are obtained through geophysical exploration, the difference of elasticity and density of underground media is utilized, the response of each stratum in the underground to manually excited seismic waves is observed and analyzed, and the pre-stack time migration data are obtained through processing of indoor computer professional software.
In this embodiment, for pre-stack time migration data, seismic data of a research area is obtained through geophysical exploration, and the seismic data is obtained through data processing by indoor professional software, that is, by utilizing the difference of elasticity and density of underground media, response of the earth to manually excited seismic waves is observed and analyzed, so as to obtain the pre-stack time migration data. The indoor pre-stack time migration processing of the outdoor seismic data is one of the most effective methods for imaging the underground complex structure, is suitable for the condition that the propagation speed of longitudinal and transverse seismic waves in each stratum is greatly changed, and is suitable for migration imaging of the complex structure.
Example 3
This embodiment further describes the lithology calculation step based on embodiment 2.
1. Calculation of formation thickness
S211, counting the thickness of each section and each sub-section stratum of each well by using prepared drilling and logging data, and acquiring the average value of the thickness of each section and each sub-section stratum as the thickness of each section and each sub-section stratum of the stratum;
in the method, the collected logging data of each well are utilized to count the thickness of stratum of Jia two and one (sub) sections, and an average value of each well is taken to design an initial model. Since the Jiang river group belongs to the sea-phase carbonate stratum, the stratum thickness of each (sub) section in the transverse direction is relatively stable, and the stratum thickness of each (sub) section of the initial model is consistent.
S212, counting the rock stratum thickness of different lithologies in each section and each sub-section of stratum of each well, and obtaining an average value of the rock stratum thickness of different lithologies in each section and each sub-section of stratum as the thickness of the rock stratum of different lithologies in each section and each sub-section of stratum of the stratum.
In the above method, the thickness of different lithologies may vary somewhat in the lateral direction due to subtle differences in the depositional environment. And (3) calculating the thicknesses of different lithologies in each section of each well in the region, and designing to obtain the thicknesses of different lithologies in each section (sub).
2. Calculation of formation velocity
In the well logging data, analyzing a well diameter curve, removing a collapsed section part of the well diameter curve, and then in the well logging data after removing the collapsed section part, taking acoustic wave curves of different lithology sections of each well, and calculating acoustic wave average speeds of different lithology of each well to be used as speeds of rock formations of different lithology.
In the method, the collected logging data are utilized to obtain acoustic wave curves (speeds) of different lithology (gypsum salt, limestone and Yun Yan) sections of each well, and the average speeds of the different lithology of each well are calculated.
3. Calculation of formation density
In the well logging data, analyzing a well diameter curve, removing a collapsed section part of the well diameter curve, and then in the well logging data after removing the collapsed section part, taking a density curve of different lithology sections of each well, and calculating the average density of different lithology sections of each well to be used as the density of rock stratum of different lithology.
In the method, the collected logging data are utilized to obtain the density curves of different lithology (gypsum salt, limestone and Yun Yan) sections of each well, and the average density of the different lithology of each well is calculated.
In this embodiment, the two sections of the lithology in the longitudinal and transverse directions are complex, the different lithology speeds and densities are different, and the average value of the speeds and densities of the different lithology sections is obtained by analyzing the logging curve. Note that the well diameter curve is analyzed first, and the collapsed section of the well diameter curve is removed to ensure accuracy of the velocity and density values, as shown in fig. 3.
In this embodiment, by analyzing the rock electrical characteristics of the coring well, it is found that the lithology of the two sections of the Jiang river set in the longitudinal direction is complex, the lithology of the gypsum rock, yun Yan and the limestone are layered, the electrical characteristics of the different lithology sections have large differences, and the distinction degree between the interlayer gypsum salt and the reservoir rock Yun Yan is most obvious in the response of the density curve.
In this embodiment, since the rock electricity correspondence of the coring well is good, the logging curves corresponding to different lithologies can be marked in software, and the average value thereof can be automatically calculated. Wherein the velocity of the gypsum is about 5500m/s, the density is 2.88g/cc, and the impedance value is 16700 m/s; about 6000m/s of limestone, 2.78g/cc of density and 16680m/s of impedance value; while Yun Yan has a speed of about 6300m/s, a density of 2.82g/cc and an impedance value of 17200 m/s.
In an open hole well, as the stratum is washed and soaked by drilling fluid, the phenomenon that the drilling fluid invades or dissolves the stratum easily occurs in different lithology, and the like, the well diameter curve can be used for dividing and verifying. For more dense limestone and Yun Yan, the permeability is poorer, the hardness is harder, the well diameter is less affected, and the well diameter curve is almost unchanged; for paste salts, the well diameter is obviously enlarged, the well diameter curve is suddenly changed and a high value is displayed. The demarcation between the paste salt and the limestone Yun Yan can be finely delineated thereby.
Example 4
This embodiment further describes the model design step on the basis of embodiment 3. In the model design step, the thickness information of rock strata with different lithology is utilized to draw a distribution characteristic model of the stratum; lithology changes of stratum of each section and each sub-section of the real well are utilized to determine lithology of the model; and setting each lithology and the speed and density of the reservoir section on the model, and unifying the model into a geological-physical model.
In the above steps, the geologic model is designed based on the result of geologic analysis of the well data. Firstly, the stratum thickness of Jia two and one (sub) sections and the stratum thickness of a reservoir section are counted through real drilling in the region, and if the stratum thickness of the well in which the fault is drilled is abnormal, the stratum thickness is not selected. And secondly, determining lithology of the model according to lithology changes of each section (sub-section) of the real well drilling in the longitudinal and transverse directions, wherein the lithology changes are matched with those of the drilled well, and the obtained forward modeling result is closer to the reflection characteristics of the well-side seismic channel. After lithology and thickness determination, the velocity and density (velocity x density = wave impedance value) of each lithology and reservoir section are set by software, thereby deriving the wave impedance value for each lithology section within each section (sub-section).
In this embodiment, the geologic model is critical, and is designed according to the thickness, speed and density information of the reservoir section and the salt layer of the real stratum obtained from the logging data. The side of the well is set according to the thickness, speed and density information of actual well drilling and well logging, the thickness between wells is set into a wedge shape when the lithology changes, and the thickness between wells is set into a horizontal lamellar shape when the lithology does not change. Because of the differences in lithologic thickness of the different zones, the lithologic thickness of the model must be determined according to the results of actual drilling and logging, as shown in fig. 4.
And (3) designing a geological model by using the thickness, speed and density value information obtained in the step S2 and the drilling data in the step S1, namely combining the thickness and lithology change of each section (sub-section) of the real drilling Jiangjiang group.
Example 5
This embodiment further describes the model forward modeling step based on embodiment 4. In the model forward modeling step, forward modeling is carried out on the geological model by simulating seismic waves in a wave equation mode, and a forward seismic section is obtained through calculation; the forward seismic section is obtained by using a synthetic seismic record, wherein the synthetic seismic record is equal to convolution of a seismic wavelet and a reflection coefficient, and the reflection coefficient is equal to a wave impedance value obtained by multiplying different rock stratum speeds and densities, and is converted into the reflection coefficient through a formula.
In this embodiment, after the geological model is designed, forward modeling is mainly implemented by professional software, and seismic forward modeling is implemented by physical modeling. According to the propagation principle of the seismic waves in the underground medium, the forward modeling calculates the seismic records of the established geological model through a wave equation forward modeling method. The forward modeling of geologic models is based on different formations having different velocities and densities, the product of which is the wave impedance. The difference in impedance between adjacent formation waves produces a reflection coefficient R. Assuming that the seismic wave is normally incident, the reflection coefficient for normal incidence can be calculated. In forward modeling, selecting an appropriate seismic wavelet is also a key to determine whether the final forward modeling result matches the actual seismic record. Rake wavelets (25 Hz) that are closer to the dominant frequency of the actual seismic data are typically selected for forward modeling.
In the model forward step, the model forward is performed by using Rake 25Hz wavelets. In this embodiment, a wave equation forward modeling method is adopted, and a Rake 25Hz wavelet which is relatively close to the main frequency of the seismic data is selected for model forward modeling, so as to achieve the purpose of accurately modeling the propagation characteristics of seismic waves under the conditions of different lithology, different speeds and different densities, as shown in fig. 4.
Wave equation forward is a method of modeling seismic reflection characteristics by means of an established geologic model, which can transform geologic phases into seismic phases. By deriving the thickness and location (depth) of the reservoir, a model of the formation's profile is plotted on the software. Giving the velocity and density values of different lithologies obtained by the previous step, unifying the velocity and density values into a geological-physical model, simulating earthquake waves by using 25HZ Rake wavelets with relatively close main frequency of earthquake data, and performing digital simulation calculation (software automatic calculation, a calculation theory method is that synthetic earthquake records are equal to convolution of the earthquake wavelets and reflection coefficients, wherein the reflection coefficients are equal to wave impedance values obtained by products of adjacent different rock stratum velocities and densities, and the wave impedance values are converted into the reflection coefficients through a formula), so that a corresponding forward earthquake section can be calculated.
The results show that: jia Er (Jia Er) 3 Reflecting a peak near an upper zero point; jia Er (Jia Er) 2 The bottom reflection is weak, and is a weak wave crest or a weak wave trough reflection.
Example 6
This example further illustrates the matching comparison step based on example 5. In the matching and comparing step, the geological model is designed according to layering, thickness, speed and density of real well drilling, and the selected Rake wavelets are close to the main frequency of the actual seismic data, so that the forward result of each well is basically consistent with the relation of the seismic reflection characteristics, amplitude and wave groups of the pre-stack time migration section beside the well. If the forward result and the actual seismic reflection characteristics, wave group relations and the like beside the well have obvious differences, the reasons should be analyzed, and the thickness of each stratum or lithology section of the model is properly modified, or the slightly modified speed and density values are considered until the forward result is more consistent with the seismic channels beside the well. And finally, analyzing whether the reflection characteristics of the top and bottom boundaries of the reservoir section in the forward result of real well drilling are consistent with the characteristics of the top and bottom boundaries of the reservoir of the actual well bypass, thereby obtaining an ideal forward result.
In the matching comparison step, the model forward result is utilized to guide the fine comparison of the bottom boundary layer bits of each sub-section in the Jiatwo. On the pre-stack time migration data volume, forward modeling results and an actual seismic migration section are analyzed, wave group characteristics and reflection energy intensity relations of Yun Yan and paste salt sections in a target interval are mainly compared, and transverse comparison principles and characteristics are determined, as shown in fig. 5.
In this embodiment, the transverse comparison principle refers to comparing seismic reflection event along a certain fixed geological interface, the characteristics refer to waveform, amplitude and energy thereof, and the purpose of determining the transverse comparison principle and the characteristics is to accurately identify a certain geological reflection interface on a pre-stack time migration section for characterizing an underground geological structure, thereby implementing the structure thereof and performing reservoir prediction work. In the step, the forward-calculated waveform characteristic results of each reflection interface are applied to the comparison tracking of the actual seismic section horizon. The embodiment mainly aims at the sea carbonate stratum, the sea sediment thickness is stable, so we refer to the femto reflection (peak reflection, continuous phase axis and easy comparison and tracking) which is close to the Jiang river group, and simultaneously combine the model forward modeling result to the Jiang two 3 Bottom and Jia two 2 The bottom is compared, and the reliability is high.
Example 7
This example further illustrates the planar lithology spread analysis procedure based on example 6. In the step of analyzing the planar lithology spread, the attribute is an attribute representing amplitude information of the seismic data; in the planar layout, the strong amplitude region is a paste salt development region, and the weak amplitude region is a reservoir development region.
In this embodiment, the strong amplitude region corresponds to a paste salt development region, and the thicker the paste salt is, the stronger the amplitude is; the weak amplitude region is a region with thinner paste salt (non-development), namely a region with relative development of the reservoir.
The seismic attributes represent the morphology, the kinematic characteristics, the dynamic characteristics and the statistical characteristics of seismic waves, the reflection characteristics of the paste salt layer and the reservoir layer have larger difference in amplitude according to forward results, and the attributes representing the amplitude information of the seismic data are selected for analysis to obtain a planar layout diagram of a full-area reservoir development area and a paste salt distribution area, so that the reservoir development area is effectively judged, as shown in fig. 6.
In this embodiment, forward modeling results show that the reflection characteristics of the salt and reservoir are greatly different in amplitude, so that the attribute of the amplitude information characterizing the seismic data is selected for analysis. The forward wave characteristics can be used for horizon comparison of an actual seismic section, and the obtained horizon data is used as the basis of a seismic attribute map.
And (3) building a time domain small stratum framework model by using well layering data and seismic horizon data, extracting amplitude attributes from software, and drawing an amplitude seismic phase plane graph (i.e. a plane expansion graph). Further analysis and verification are carried out on the plane diagram interpreted by the earthquake phase, and cross verification is carried out by utilizing the azimuth of the seismic phase delineation and the paste salt distribution condition of the coring well. If inconsistent conditions exist, the tracking comparison of the seismic horizon is rechecked. The strong amplitude area on the seismic phase diagram is determined as a paste salt development area, and the determined paste salt distribution on a plane is determined.
While the embodiments of the present invention have been described in detail, the present invention is not limited to the embodiments described above, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the present invention, and these are intended to be included in the scope of the present invention as defined in the appended claims.
Claims (10)
1. The method for eliminating the paste salt layer based on the model forward modeling is characterized by comprising a data preparation step, a lithology calculation step, a model design step, a model forward modeling step, a matching comparison step and a planar lithology spread analysis step;
the data preparation step, preparing basic data including drilling data, lithology data, logging data and pre-stack time migration data;
the lithology calculating step calculates and obtains thickness, speed and density values of different lithology rock strata by using drilling and logging data;
the model design step utilizes thickness, speed and density value information of different lithology rock layers and the drilling data to design a geological model;
the model forward modeling step is used for modeling forward modeling the geological model by adopting a wave equation forward modeling method, and simulating seismic wave propagation characteristics under the conditions of different lithology, different speeds and different densities;
the matching comparison step is used for matching comparison and correction of forward results and actual seismic data, and determining seismic reflection characteristics of different lithology or lithology combinations;
and the plane lithology spread analysis step is used for extracting and analyzing the amplitude attribute of the seismic reflection characteristics to obtain a plane spread graph of the full-area reservoir development area and the paste salt distribution area, and removing the paste salt distribution area to obtain the reservoir development area.
2. The method for removing salt from paste based on model forward modeling as claimed in claim 1, wherein in the data preparing step, seismic data of a research area is obtained through geophysical exploration, and the pre-stack time migration data is obtained through observing and analyzing responses of each stratum of the subsurface to manually excited seismic waves by utilizing differences of elasticity and density of the subsurface medium and through indoor computer professional software processing.
3. The method for removing a salt layer of a paste based on model forward modeling as defined in claim 1, wherein in the lithology calculating step, the rock layer thickness calculating method is as follows: using the prepared drilling and logging data to count the thickness of each section and each sub-section stratum of each well, and obtaining the average value of the thickness of each section and each sub-section stratum as the thickness of each section and each sub-section stratum of the stratum; and counting the rock stratum thickness of different lithologies in each section and each sub-section of stratum of each well, and obtaining the average value of the rock stratum thickness of different lithologies in each section and each sub-section of stratum as the thickness of the rock stratum of different lithologies in each section and each sub-section of stratum of the stratum.
4. The method for removing a salt deposit based on model forward modeling as defined in claim 1, wherein in the lithology calculating step, the rock formation velocity calculating method is as follows: in the well logging data, analyzing a well diameter curve, removing a collapsed section part of the well diameter curve, and then in the well logging data after removing the collapsed section part, taking acoustic wave curves of different lithology sections of each well, and calculating acoustic wave average speeds of different lithology of each well to be used as speeds of rock formations of different lithology.
5. The method for removing a salt layer of a paste based on model forward modeling as defined in claim 1, wherein in the lithology calculating step, the rock formation density calculating method is as follows: in the well logging data, analyzing a well diameter curve, removing a collapsed section part of the well diameter curve, and then in the well logging data after removing the collapsed section part, taking a density curve of different lithology sections of each well, and calculating the average density of different lithology sections of each well to be used as the density of rock stratum of different lithology.
6. The method for removing the paste salt layer based on the model forward modeling as defined in claim 1, wherein in the model designing step, the thickness information of different lithology rock layers is utilized to draw a distribution characteristic model of the stratum; lithology changes of stratum of each section and each sub-section of the real well are utilized to determine lithology of the model; and setting each lithology and the speed and density of the reservoir section on the model, and unifying the model into a geological-physical model.
7. The method for removing the paste salt layer based on model forward modeling as defined in claim 1, wherein in the model forward modeling step, forward modeling is performed on the geological model by simulating seismic waves in a wave equation mode, and a forward modeling seismic section is obtained through calculation; the forward seismic section is obtained by using a synthetic seismic record, wherein the synthetic seismic record is equal to convolution of a seismic wavelet and a reflection coefficient, and the reflection coefficient is equal to a wave impedance value obtained by multiplying different rock stratum speeds and densities, and is converted into the reflection coefficient through a formula.
8. The method for removing a salt layer of a paste based on model forward according to claim 1, wherein in the model forward step, the model forward uses a Rake 25Hz wavelet for model forward.
9. The method for removing the paste salt layer based on model forward modeling as defined in claim 1, wherein in the matching comparison step, on a prestack time migration data body, forward modeling results and an actual seismic migration section are analyzed, wave group characteristics and reflection energy intensity relations of Yun Yan and paste salt sections in a target layer section are compared, and a transverse comparison principle and characteristics are determined.
10. The method for removing a salt layer based on model forward modeling as claimed in claim 1, wherein in the planar lithology spread analysis step, the attribute is an attribute representing amplitude information of the seismic data; in the planar layout, the strong amplitude region is a paste salt development region, and the weak amplitude region is a reservoir development region.
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