A palaeo-dark river height quantification correction method and system based on forward and inverse modeling

Abstract

The application provides a paleo-dark river height quantification correction method and system based on forward and inverse, and belongs to the technical field of oil and gas geophysical exploration. The application adopts a method combining forward simulation and impedance inversion, establishes a height correction template, and realizes quantification correction of the height of a paleo-dark river reservoir body. The height correction template established based on the forward and inverse of a karst cave body can preferably represent the actual height of the dark river; drilling calibration shows that the height correction template based on an abnormal coefficient of 50% can preferably represent the height of the dark river reservoir, especially improves the prediction accuracy of the dark river reservoir body less than 10 meters, and compared with the wave impedance inversion, the height of the dark river predicted by the method of the application is more consistent with the height of the paleo-dark river reservoir interpreted from the well logging.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas geophysical exploration technology, specifically relating to a method and system for quantitative correction of ancient underground river height based on forward and inverse modeling. Background Technology

[0002] Carbonate rock karst paleochannels are widely developed in the Tarim River region of Northwest China. The oil reservoirs are deeply buried, with extremely irregular reservoir development, strong vertical and horizontal heterogeneity, and great difficulty in reservoir prediction.

[0003] Studies on ancient river channel seismic identification show that the seismic reflection characteristics of underground rivers are characterized by strong reflection along the direction of the underground river with good lateral continuity; perpendicular to the direction of the river channel, the reflection is mainly beaded, with some local areas showing relatively weak reflection due to the less obvious beaded characteristics. Among them, the main channel of the underground river has strong energy and good continuity in various planes and spaces, and has a long extension.

[0004] Based on well point identification of karst-type reservoirs, a correspondence between paleochannel reservoirs and seismic reflection characteristics can be established through well-seismic calibration. However, for the quantitative characterization of paleochannel reservoir height, the difference between seismic anomalies and geological anomalies due to the influence of seismic resolution makes it difficult to accurately characterize the height of paleochannels based on seismic reflection characteristics. While impedance inversion data based on seismic data can effectively characterize the development height of karst paleochannels, its applicability is limited. For paleochannels with thinner reservoirs, there is a significant error between impedance inversion anomalies and reservoir height. Improving the prediction accuracy of small-scale paleochannel reservoirs has always been a challenging problem for exploration and development workers.

[0005] Chinese patent publication CN 103454685 A discloses a method and apparatus for predicting sand body thickness using well logging constrained impedance inversion. Using the geological well logging data as constraints, the method selects several sampling points for each sand group in the target exploration area to fit the relationship curve between the total impedance value of the sand body and its thickness for the corresponding sand group, thereby obtaining the thickness of the sand body for the corresponding sand group.

[0006] Chinese patent publication CN 105093306 A discloses an automatic reservoir interpretation and thickness determination method in geophysical exploration. Based on seismic data and well logging data, it obtains wave impedance inversion data volume by well logging-constrained seismic inversion and combines it with well drilling stratification. The target layer to be interpreted is determined by synthesizing seismic record calibration results.

[0007] The Chinese public literature "Application of wave impedance inversion in sand body thickness prediction in Xingma area" (Oil Industry Computer Application, 2014.06) is based on the basic principle of the constrained sparse pulse wave impedance method, extracts the target layer seismic wavelet in well-seismic calibration, optimizes the horizon, establishes the low-frequency model and multiple quality monitoring in line with the geological law, and carries out the wave impedance inversion in the area. The sand body thickness identified according to the inversion result is consistent with the actual data at 24 well points, with a coincidence degree of 79.2%.

[0008] The Chinese public literature "Wave impedance constrained inversion technology for predicting coal seam thickness" (Coal Geology and Exploration, 2007.02), "Coal seam thickness prediction using seismic lithology inversion technology" (Western Prospecting Engineering, 2008.08) and "Improving coal seam thickness prediction accuracy by reconstructing seismic data using wave impedance inversion" (Mining Safety and Environmental Protection, 2016.10) all use wave impedance inversion technology to predict coal seam thickness. The wave impedance layer corresponding to the coal seam is determined through horizon calibration, and then the thickness of the wave impedance layer is extracted and matched with the coal seam thickness at the coal drilling point. Finally, the coal seam thickness distribution rule of the three-dimensional seismic survey area is obtained.

[0009] The existing public literature does not have a method and technical process for high quantification correction of ancient riverway. SUMMARY

[0010] The purpose of the present application is to solve the problems existing in the prior art, and to provide an ancient dark river height quantification correction method and system based on forward and inverse modeling, which quantifies the ancient dark river reservoir height based on wave impedance inversion quantification analysis of forward modeling simulation, improves the prediction accuracy of small-scale ancient dark river reservoirs, and provides strong technical support for guiding deep carbonate reservoir exploration and development efficiency.

[0011] The present application is realized by the following technical solutions:

[0012] In a first aspect of the present application, an ancient dark river height quantification correction method based on forward and inverse modeling is provided, which uses a method combining forward modeling and impedance inversion to establish a height correction template and realize quantification correction of the ancient dark river reservoir height.

[0013] Further improvements of the present application are as follows:

[0014] The method comprises the following steps:

[0015] (1) Establishing a forward modeling model of different heights of karst cave bodies;

[0016] (2) Establishing a height correction template;

[0017] (3) Predicting the ancient dark river reservoir height.

[0018] Further improvements of the present application are as follows:

[0019] The step (1) is to establish a forward model of different heights of the karst cave, and the specific operation is as follows:

[0020] The forward simulation is carried out for the karst cave models with different heights, the width of the karst cave is unchanged, the intertrace distance is fixed, and the forward models with different heights are respectively established by using the same height difference interval.

[0021] The further improvement of the present application is that:

[0022] According to the logging interpretation results of the drilling in the actual work area, the velocity and density of the karst cave model and the surrounding rock are obtained by respectively counting the velocity and density of the karst cave section and the surrounding rock section; based on the stacking section of the karst cave model obtained by the forward simulation, the spatial position of the karst cave with different heights and the change of the reflection energy can be seen on the stacking section.

[0023] The further improvement of the present application is that:

[0024] The step (2) is to establish a height correction template, and the specific operation is as follows:

[0025] The stacking section of the karst cave with different heights is obtained based on the forward simulation, the wave impedance section is obtained by sparse pulse inversion, and the relationship curve between the inversion wave impedance and the height of the karst cave, i.e. the inversion wave impedance curve, is established;

[0026] According to the relationship between the position model of the karst cave and the inversion wave impedance curve, the background impedance value, the impedance value of the karst cave model and the minimum value of the inversion impedance curve are determined;

[0027] Due to the influence of the surrounding rock, the minimum value of the inversion impedance curve is always greater than the impedance value of the bottom boundary position of the karst cave, and the relationship graph between the abnormal height and the actual height under different abnormal coefficients, i.e. the height correction template, is established.

[0028] The further improvement of the present application is that:

[0029] The relationship graph between the abnormal height and the actual height has an actual height as the horizontal coordinate and an abnormal height as the vertical coordinate, and the abnormal height is the height obtained based on the impedance inversion.

[0030] The further improvement of the present application is that:

[0031] The step (3) is to predict the height of the ancient dark river reservoir, and the specific operation is as follows:

[0032] According to the actual reservoir height of the drilling, the numerical range of the wave impedance is adjusted, the threshold value of the wave impedance inversion is determined, the height correction template based on the abnormal coefficient 50% is adjusted, the wave impedance abnormal low value under the 50% color scale is reserved, the reservoir abnormal height (time height ms) of the channel well is read, the actual height (meter) is converted based on the velocity body of the working area, and the predicted height of the dark river reservoir is determined based on the height correction template under the abnormal coefficient 50%.

[0033] In a second aspect, the present application provides a paleo-dark river height quantification correction system based on forward and inverse modeling, comprising:

[0034] A forward modeling establishment unit is configured to establish a forward model of different heights of the cave body.

[0035] A height correction template establishment unit is connected with the forward modeling establishment unit and configured to establish a height correction template based on the wave impedance inversion quantification analysis of the forward modeling.

[0036] A height prediction unit is connected with the height correction template unit and configured to predict the paleo-dark river reservoir height based on the height correction template.

[0037] In a further improvement of the present application,

[0038] The system further comprises:

[0039] An inversion wave impedance curve acquisition unit is respectively connected with the forward modeling establishment unit and the height correction template establishment unit and configured to obtain the stacked section of the cave body of different heights based on the forward modeling, obtain the wave impedance section through sparse pulse inversion, and formulate the relationship curve between the inversion wave impedance of the cave and the height, i.e., the inversion wave impedance curve.

[0040] In a third aspect, the present application provides a computer readable storage medium storing at least one computer executable program, which, when executed by a computer, causes the computer to perform the steps of the paleo-dark river height quantification correction method based on forward and inverse modeling.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] The height correction template based on the forward and inverse modeling of the cave body can better represent the actual height of the dark river.

[0043] The drilling calibration shows that the height correction template based on the abnormal coefficient 50% can more accurately represent the dark river reservoir height, especially improving the prediction accuracy of the dark river reservoir less than 10 meters. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 Step block diagram of the method of the present application;

[0045] Figure 2 is a different height cave forward modeling stack section;

[0046] Figure 3 is a wave impedance profile based on the forward wave impedance model inversion;

[0047] Figure 4 is a model at the cave and the inversion impedance curve;

[0048] Figure 5 is an abnormal height correction template of 50% abnormal coefficient (the relationship between the abnormal height determined by impedance inversion and the actual height);

[0049] Figure 6 is a 50% abnormal coefficient determination wave impedance abnormal height implementation process;

[0050] Figure 7 is the identification effect of the actual drilling verification A# reservoir;

[0051] Figure 8 is the identification effect of the actual drilling verification B# reservoir;

[0052] Figure 9 is the identification effect of the actual drilling verification C# reservoir;

[0053] Figure 10 is the identification effect of the actual drilling verification D# reservoir. DETAILED DESCRIPTION

[0054] The present application will be further described in detail below in combination with the accompanying drawings:

[0055] The method of the present application is aimed at the identification ability of wave impedance inversion to different height cave bodies, and carries out targeted forward modeling and wave impedance inversion. Based on the model forward data and combined with the well logging interpretation data of the actual drilling, the quantitative relationship (classification) between the forward modeling and impedance inversion is established, the correction coefficient of different scale ancient dark river height and wave impedance inversion is analyzed, the hierarchical quantitative characterization of the ancient dark river height is realized, and the prediction accuracy of small scale ancient dark river reservoir is improved.

[0056] The present application adopts the method of combining forward modeling and impedance inversion, establishes the dark river height correction template, and realizes the quantitative correction of the ancient dark river reservoir height.

[0057] The implementation of the method of the present application is as follows:

[0058]

Example 1

[0059] As Figure 1As shown, the method of the present application comprises:

[0060] (1) Establishing forward models of different heights of the karst cave

[0061] Carrying out forward simulation for different height karst cave models, with unchanged karst cave width and fixed trace interval (consistent with the actual seismic acquisition trace interval in the work area), and using the same height difference interval to develop different height forward models;

[0062] According to the well logging interpretation results of the actual work area, the velocities and densities of the karst cave section and the surrounding rock section are respectively counted to obtain the velocities and densities of the karst cave model and the surrounding rock; based on the forward simulation, the stacking section of the karst cave model is obtained, from which the spatial positions of different height karst caves and the changes of reflection energy can be seen.

[0063] (2) Quantitative analysis based on wave impedance inversion of forward simulation to establish a height correction template

[0064] Based on the forward simulation of step (1), the stacking section of different height karst caves is obtained, the wave impedance section is obtained through sparse pulse inversion, and the relationship curve between the karst cave inversion wave impedance and height is developed;

[0065] According to the relationship between the karst cave position model and the inversion wave impedance curve, the background impedance value, the karst cave model impedance value and the minimum value of the inversion impedance curve are determined;

[0066] Due to the influence of surrounding rock, the minimum value of the inversion impedance curve will always be greater than the impedance value of the bottom boundary position of the karst cave, and the relationship graph between the abnormal height and the actual height under different abnormal coefficients, i.e. the height correction template, is established.

[0067] The abnormal coefficient refers to the percentage of the vertical distance between the minimum value of the inversion impedance curve and the background impedance value.

[0068] Taking the correction template under 50% abnormal coefficient as an example, the relationship graph between the abnormal height and the actual height is explained, in which the horizontal coordinate is the actual height (from left to right, the karst cave height increases), and the vertical coordinate is the abnormal height, which is the height obtained based on the impedance inversion.

[0069] (3) Predicting the height of the ancient dark river based on the height correction template

[0070] According to the actual reservoir height of the drilled well, the numerical range of the wave impedance is adjusted to determine the threshold value of the wave impedance inversion for calibrating the reservoir height of the research area; based on the height correction template of the abnormal coefficient of 50%, the wave impedance inversion color scale is adjusted, the low wave impedance abnormal value under the 50% color scale is reserved, the reservoir abnormal height (time height ms) of the channel well is read, the actual height (meter) is converted based on the velocity body of the working area, and the predicted height of the dark river reservoir is determined based on the height correction template under the abnormal coefficient of 50%. The reservoirs with different heights of the ancient dark river well in the working area are subjected to actual application detection.

[0071] The method will be further described below through an application example of an actual drilled well.

[0072]

Example 2

[0073] (1) Establishment of forward model of different height karst cave

[0074] Forward simulation is carried out for different height karst cave models, a set of physical simulation models of different height karst caves are established, the velocities and densities of the karst cave and the surrounding rock are given according to the statistical results of the well logging interpretation of the reservoir and non-reservoir in the actual working area. The karst cave width is 50 m, the trace interval is 15 m, the heights of the karst caves from left to right are 5 m, 10 m, 15 m, 20 m, 25 m, 30 m, 35 m, 40 m, 45 m and 50 m, the velocity is 4774.0898 m / s, the density is 1.9121 g / cm 3 , the velocity of the surrounding rock is 6000 m / s, and the density is 2.0243 g / cm 3 , that is, the reflection coefficient of the karst cave is 0.1418. Figure 2 is the superimposed profile of the physical simulation of the karst cave with different heights, and the spatial position of the karst cave can be seen on the superimposed profile. Figure 2 It can be seen that the reflection energy increases with the increase of the height of the karst cave.

[0075] (2) Quantitative analysis based on wave impedance inversion

[0076] Based on the above-mentioned initial wave impedance model established by forward simulation, the wave impedance profile (as shown in Figure 3 ) is obtained by inversion, and the inversion result is similar to the initial impedance model, and the inversion result is reliable.

[0077] Figure 4 is the model of one of the karst cave positions and the inversion wave impedance curve, the background impedance value B / B' is 12145543 Kg / m 3 , the impedance value at the karst cave D / D' is 9189251 Kg / m 3 , and the impedance value at the minimum point A of the inversion impedance curve is 9642898 Kg / m 3Impedance value of A point is always greater than impedance value of D / D' point due to the influence of surrounding rock. Impedance difference from A point to B / B' point is defined as impedance anomaly, and impedance difference from C / C' point to B / B' point is defined as 50% of impedance anomaly, and anomaly identification 50% proportion coefficient = BB' / CC'. Relationship between anomaly height and actual height under different anomaly coefficients can be established, Figure 5 Cave height correction chart under anomaly coefficient 50% can show that there is a good linear relationship between impedance inversion anomaly height and actual height.

[0078] (3) Quantitative correction of actual height of underground river

[0079] The maximum value and minimum value of wave impedance inversion are determined through well calibration, the wave impedance color scale is adjusted based on height identification template under anomaly coefficient 50%, the low value of wave impedance anomaly under 50% color scale is reserved ( Figure 6 ), the anomaly height of river well is read, the actual height (meter) is converted based on velocity body of the working area, and the predicted height of underground river reservoir is determined based on height correction template under 50% anomaly coefficient.

[0080] The actual application detection is carried out for different height reservoirs of the ancient underground river well in the working area, and the prediction result is shown in Figure 7 - Figure 10 It can be seen that the actual height of reservoir logging interpretation of well A is 44 m, the wave impedance anomaly height is 22 m (the error is 22 m with the actual height), for the reservoir greater than 40 m, the identification of wave impedance inversion to reservoir height is less than the actual height, and the predicted height determined based on the height correction template is 45 m, and the error is 1 m with the actual height.

[0081] For the medium scale reservoir B well, the actual height of the reservoir is 26 m, the wave impedance inversion anomaly height is 21 m (the error is 5 m), and the predicted height of the correction template is 25 m (the error is 1 m).

[0082] For small scale reservoir (reservoir height less than 10 m, wave impedance inversion predicts reservoir height greater than actual height): the actual height of the underground river of well C is 7 m, the wave impedance anomaly height is 17 m (the error is 10 m), and the predicted height of the reservoir based on the height correction template is 5 m (the error is 2 m); the actual reservoir height of well D is 9.4 m, the wave impedance identification anomaly height is 16 m (the error is 7.4 m), and the predicted height of the reservoir based on the height correction template is 5 m (the error is 4.4 m). It can be seen that for the reservoir with a height less than 10 m, the prediction error of the reservoir height identified based on the method is greatly reduced compared with the reservoir height identified by wave impedance inversion, and the prediction accuracy of small scale underground river reservoir is obviously improved.

[0083] The application also provides a paleo-underground river height quantitative correction system based on forward and inverse modeling, and the implementation of the system is as follows:

[0084]

Example 3

[0085] The system comprises:

[0086] A forward model establishing unit is configured to establish a forward model of different heights of the cave body.

[0087] A height correction template establishing unit is connected with the forward model establishing unit and configured to establish a height correction template based on quantitative analysis of wave impedance inversion of forward simulation.

[0088] A height prediction unit is connected with the height correction template unit and configured to predict the height of the ancient dark river reservoir based on the height correction template.

[0089] The system further comprises:

[0090] An inversion wave impedance curve obtaining unit is respectively connected with the forward model establishing unit and the height correction template establishing unit and configured to obtain a stacked section of the cave body of different heights based on forward simulation, obtain a wave impedance section through sparse pulse inversion, and formulate a relationship curve between the inversion wave impedance of the cave and the height, i.e., an inversion wave impedance curve.

[0091] The application further provides a computer readable storage medium, and implementation of the computer readable storage medium is as follows:

[0092]

Embodiment 4

[0093] The computer readable storage medium stores at least one computer executable program, and the at least one program enables the computer to execute the steps in the ancient dark river height quantitative correction method based on forward and inversion when the computer executes the at least one program.

[0094] The height correction template established based on the forward and inversion of the cave body can preferably represent the actual height of the dark river.

[0095] Drilling calibration shows that the height correction template based on the abnormal coefficient 50% can preferably represent the height of the dark river reservoir, especially the prediction accuracy of the dark river reservoir less than 10 meters is improved, and compared with the wave impedance inversion, the dark river height predicted by the method of the application is more consistent with the ancient dark river reservoir height interpreted by well logging.

[0096] Finally, it should be noted that the above technical solutions are only one embodiment of the application, and for those skilled in the art, on the basis of the application disclosed application method and principle, various types of improvements or deformations can be easily made, and are not limited to the method described in the above embodiment of the application, therefore, the above described method is only preferred, and does not have the meaning of limitation.

Claims

1. A method for quantitative correction of paleo-underground river height based on forward and inverse modeling, characterized in that, A height correction template was established by combining forward modeling and impedance inversion to achieve quantitative correction of the height of ancient underground river reservoirs; The method includes the following steps: (1) Establish forward modeling of caves at different heights; (2) Establish a height correction template. Specific operations include: Based on forward modeling, superimposed profiles of karst caves at different heights are obtained. Wave impedance profiles are obtained through sparse pulse inversion. The relationship curve between the inverted wave impedance and height of the karst cave is established, namely the inverted wave impedance curve. Based on the relationship between the location model of the karst cave and the inversion wave impedance curve, determine the background impedance value, the karst cave model impedance value, and the minimum value of the inversion impedance curve; Due to the influence of the surrounding rock, the minimum value of the inversion impedance curve will always be greater than the impedance value at the bottom boundary of the cave. A graph showing the relationship between the abnormal height and the actual height under different anomaly coefficients is established, which is the height correction template. The graph showing the relationship between abnormal height and actual height has the actual height on the horizontal axis and the abnormal height on the vertical axis. The abnormal height is the height obtained based on impedance inversion. (3) Based on the height correction template, the height of the ancient underground river reservoir is predicted. The specific operation is as follows: Based on the actual reservoir height of the well, the numerical range of the wave impedance is adjusted to determine the threshold value for wave impedance inversion calibration of the reservoir height in the study area; based on the height correction template with an anomaly coefficient of 50%, the wave impedance inversion color scale is adjusted, and the low value of the wave impedance anomaly under the 50% color scale is retained. The anomaly height of the river well reservoir is read, and the actual height is converted based on the velocity volume of the work area. On this basis, the predicted height of the underground river reservoir is determined based on the height correction template with an anomaly coefficient of 50%.

2. The method according to claim 1, characterized in that, Step (1) involves establishing forward models of the cave body at different heights. The specific operation is as follows: Forward modeling was conducted for cave models at different heights, with the cave width and channel spacing remaining constant. Forward modeling models at different heights were developed using the same height difference.

3. The method according to claim 2, characterized in that, Based on the logging interpretation results of actual drilling in the work area, the velocity and density of the karst cave section and the surrounding rock section were statistically analyzed to obtain the velocity and density of the karst cave model and the surrounding rock. Based on forward modeling, a superimposed profile of the karst cave model was obtained. The spatial location of karst caves at different heights and the changes in reflected energy can be seen on the superimposed profile.

4. A paleo-underground river height quantization correction system based on forward and inverse modeling, characterized in that, The system is used to perform the steps in the paleo-underground river height quantization correction method based on forward and inverse modeling as described in any one of claims 1-3, the system comprising: Forward model building unit, used to build forward models of cave bodies at different heights; A height correction template establishment unit is connected to the forward model establishment unit and is used to establish a height correction template based on wave impedance inversion quantization analysis of forward modeling. The height prediction unit is connected to the height correction template establishment unit and is used to predict the height of the ancient underground river reservoir based on the height correction template.

5. The system according to claim 4, characterized in that, The system also includes: The inversion wave impedance curve acquisition unit, together with the forward model establishment unit and the height correction template establishment unit, is used to obtain superimposed profiles of karst caves of different heights based on forward modeling, obtain wave impedance profiles through sparse pulse inversion, and formulate the relationship curve between the inversion wave impedance and height of the karst cave, i.e., the inversion wave impedance curve.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one computer-executable program, which, when executed by the computer, causes the computer to perform the steps of the paleo-underground river height quantization correction method based on forward and inverse modeling as described in any one of claims 1-3.

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