Reservoir identification method

Abstract

The invention relates to a reservoir identification method, and belongs to the technical field of oil-gas exploration and development. And determining the reservoir development condition of the target stratum by using the seismic data, the logging data and the gas testing data of the target stratum. Based on the reservoir development condition of the target stratum, wave crest and wave trough positions of the target stratum are determined through well seismic calibration and forward modeling, and structural interpretation is conducted on the wave crest and wave trough positions of the target stratum. And determining the seismic reflection characteristics of the reservoir by using a structural interpretation result, a multi-well synthetic record and a forward modeling result. Subtracting the wave trough horizon from the obtained wave crest horizon of the target layer to obtain a wave trough-to-wave crest interval time plane graph, and utilizing the interval time plane graph to construct a high-timeliness deposition interface. And recognizing the reservoir according to the determined seismic reflection characteristics of the reservoir and the constructed high-temporal sedimentary interface. According to the method, the problems that the improvement of the seismic data resolution is limited and the identification result is easily interfered by the seismic event time penetration, so that the reservoir identification precision is relatively low are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a reservoir identification method, and belongs to the technical field of oil and gas exploration and development. BACKGROUND

[0002] The carbonate platform beach reservoir and the karst weathering crust reservoir are thin (generally 5-30 meters in thickness), poor in physical property (generally 3-7% in porosity), and strong in heterogeneity, and the response characteristics on the seismic profile are weak. Moreover, the mutual interference with the strong seismic reflection axis (isochronous sedimentary interface) of the overlying low-velocity gypsoline and marl will produce a tuning effect, and the reservoir is strong in concealment.

[0003] Most of the existing thin reservoir identification methods are based on improving the resolution of seismic data to realize the prediction of the reservoir. For example, the Chinese patent application file with the application publication number CN105092343A discloses a method for removing the thin layer tuning effect based on prestack traces, which reconstructs the seismic data after the wavelet scale decomposition processing to improve the resolution of the seismic data, and then uses the reconstructed data to improve the accuracy of the seismic prediction of the reservoir. However, because the resolution of the seismic data itself may be low, the improvement of the resolution of the seismic data will be limited, thereby resulting in low accuracy of the reservoir identification.

[0004] Moreover, the prior art has proposed that different attribute analysis methods are used for various reflection characteristics to realize the prediction of the reservoir distribution. Although this method can greatly improve the reliability of the prediction, it can only qualitatively identify the reservoir through various seismic facies characteristics, and the identification result is easily disturbed by the time interference of the seismic events, thereby resulting in low accuracy of the reservoir identification.

[0005] In summary, the existing reservoir identification method has the problems of low accuracy of the reservoir identification due to the limited improvement of the resolution of the seismic data and the time interference of the seismic events. SUMMARY

[0006] The present application aims to provide a reservoir identification method to solve the problem of low accuracy of the reservoir identification due to the limited improvement of the resolution of the seismic data and the time interference of the seismic events in the prior art.

[0007] To achieve the above-mentioned purpose, the technical solution provided by the present application is as follows:

[0008] The present application provides a reservoir identification method, which comprises the following steps:

[0009] 1) determining the reservoir development of the target layer by using the seismic data, the well logging data and the gas testing data of the target layer;

[0010] 2) Based on the reservoir development of the target layer, the wave peak and wave trough horizon of the target layer are determined by well-to-seismic calibration and forward modeling, and the wave peak and wave trough horizon of the target layer are structurally interpreted;

[0011] 3) The reservoir seismic reflection characteristics are determined by using the structural interpretation results, multi-well synthetic records and forward modeling results;

[0012] 4) The wave peak horizon of the target layer is subtracted from the wave trough horizon to obtain the interval time plane from the wave trough to the wave peak, and the high-chronological sedimentary interface is constructed by using the interval time plane;

[0013] 5) The reservoir is identified according to the reservoir seismic reflection characteristics determined in step 3) and the high-chronological sedimentary interface constructed in step 4).

[0014] Further, the process of determining the high-chronological sedimentary interface is:

[0015] A. The difference between the wave peak horizon and the wave trough horizon of the target layer is corrected by dip, and the interval time plane from the wave trough to the wave peak is obtained;

[0016] B. When the interval time plane has a trend change and the change amplitude is greater than a time set threshold, the interval time plane is used for regional division;

[0017] C. The wave trough horizon of the divided region is added to the interval time average of the corresponding region, and the high-chronological sedimentary interface is obtained by smoothing at the boundaries of other adjacent regions.

[0018] Further, the reservoir seismic reflection characteristics are divided according to the reservoir properties, and the seismic reflection characteristics corresponding to the better reservoir properties are the strong amplitude reflection of pull-down, and the seismic reflection characteristics corresponding to the poor reservoir properties are the weak amplitude or complex wave reflection.

[0019] Further, the good or bad of the reservoir properties is determined according to the size of the porosity, and the larger the porosity, the better the corresponding reservoir properties.

[0020] Further, in step 5), the reservoir distribution is predicted by using the corresponding amplitude attribute for different reservoir properties. For the reservoir with good properties, the high-chronological sedimentary interface layer is shifted downward by a set first threshold, and the maximum amplitude attribute is used to realize the prediction of the reservoir distribution; for the reservoir with poor properties, the high-chronological sedimentary interface layer is shifted downward by a set second threshold, and the minimum amplitude attribute is used to realize the prediction of the reservoir distribution.

[0021] Further, the identification method further includes quantitatively predicting the thickness of the reservoir.

[0022] Further, the quantitative prediction process is: obtaining the reservoir P-wave impedance by using the inversion method, and realizing the quantitative prediction of the reservoir thickness according to the comparison result of the reservoir P-wave impedance and the reservoir P-wave impedance setting threshold.

[0023] Further, the reservoir P-wave impedance setting threshold is related to the good or bad of the reservoir property, and the P-wave impedance setting threshold of the reservoir property is greater than that of the reservoir property.

[0024] Further, the inversion adopts waveform inversion.

[0025] Further, the identification method further comprises oil and gas detection on the identified reservoir to determine the favorable area of the reservoir development.

[0026] Beneficial effects: the present application belongs to an improved invention, and the reservoir identification method provided by the present application subtracts the wave trough horizon from the wave peak horizon of the obtained target layer to obtain an interval time plane from the wave trough to the wave peak, constructs a high-chronology sedimentary interface by using the interval time plane, and identifies the reservoir according to the determined reservoir seismic reflection characteristics and the constructed high-chronology sedimentary interface. It can be seen that the present application constructs a high-chronology sedimentary interface according to the interval time plane from the wave trough to the wave peak obtained by subtracting the wave trough horizon from the wave peak horizon of the obtained target layer before identifying the reservoir, and the thin reservoir can also be identified according to the constructed high-chronology sedimentary interface, thereby effectively solving the problems of the low reservoir identification accuracy caused by the limitation of the improvement of the seismic data resolution and the interference of the seismic event chronology in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a flow chart of the reservoir identification method of the present application;

[0028] Figure 2 is a target layer reservoir development feature and longitudinal distribution map of the A work area of the present application;

[0029] Figure 3 is a wave peak horizon and wave trough horizon construction interpretation schematic diagram of the A work area of the present application;

[0030] Figure 4a is a first well synthetic record diagram of the present application;

[0031] Figure 4b is a second well synthetic record diagram of the present application;

[0032] Figure 4c is a forward simulation result diagram of the present application;

[0033] Figure 5 is an interval time plane obtained by subtracting the wave trough horizon from the wave peak horizon of the present application;

[0034] Figure 6 is the high-order time depositional interface map constructed by the present application;

[0035] Figure 7 is the reservoir plan distribution map of the present application;

[0036] Figure 8 is the rock physical analysis map of the target layer of the present application;

[0037] Figure 9 is the reservoir inversion schematic diagram of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with the drawings and examples.

[0039] The reservoir identification method of the present application subtracts the wave trough horizon from the wave peak horizon of the obtained target layer to obtain the interval time planar map from the wave trough to the wave peak, uses the interval time planar map to construct the high-order time depositional interface, and identifies the reservoir according to the determined reservoir seismic reflection characteristics and the constructed high-order time depositional interface. Compared with the prior art, the present application effectively solves the problems of the reservoir identification precision being low due to the improvement of the seismic data resolution being limited and the identification result being easily interfered by the time of the seismic event.

[0040] Embodiment of the reservoir identification method:

[0041] The reservoir identification method flow of the present application is shown in Figure 1 The technical scheme of the present application is specifically described as follows:

[0042] 1. Using the seismic data, logging data and gas testing data of the target layer to determine the reservoir development situation of the target layer.

[0043] Firstly, the seismic data, logging data and gas testing data of the target layer are used to determine the reservoir development situation of the target layer, and the reservoir development situation includes lithology, physical property, thickness and longitudinal and horizontal development position.

[0044] The reservoir development characteristics and longitudinal distribution map of the target layer in the A working area are shown in Figure 2As shown, the target layer of A work area belongs to carbonate platform deposition mode, and is in a limited-open platform deposition environment. The early stage of A work area is open platform facies, and the intra-platform beach mainly develops in the north of the work area. The late stage is limited platform deposition, and the intra-platform beach sporadically develops in the south of the work area. The embodiment mainly depicts the intra-platform beach reservoir developed at the top of the target layer of A work area in the late stage. The reservoir thickness is thin, generally 5-30 meters, and changes fast in the horizontal direction, and is sporadically distributed and not gathered. The reservoir lithology is mainly limestone, the average porosity of the reservoir is 3.12%, and the average permeability is 0.235*10-3 μm2. The reservoir development position is generally close to the top of the target layer of A work area (within 25 meters), and a set of stable low-velocity gypsum rock develops above.

[0045] 2. Based on the reservoir development of the target layer, the wave peak and wave trough phases (also called horizons) of the target layer are determined through well-seismic calibration and forward simulation, and the target layer wave peak and wave trough horizons are structurally interpreted.

[0046] Based on the reservoir development of the target layer, the wave peak and wave trough phases of the target layer are determined through well-seismic calibration and forward simulation, and the target layer wave peak and wave trough horizons are structurally interpreted. In the embodiment, the top of the target layer of A work area is determined to be the wave peak horizon of the bottom of the low-velocity gypsum rock layer stably developed in the whole area, and the top of the gypsum rock layer is the stably distributed wave trough horizon. The wave trough at the top of the gypsum rock layer and the wave peak at the bottom of the gypsum rock layer are structurally interpreted by 8*8, as shown in Figure 3 .

[0047] 3. The reservoir seismic reflection characteristics are determined by using the structural interpretation results, multi-well synthetic records and forward simulation results.

[0048] The reservoir seismic reflection characteristics (also called seismic response characteristics) are determined by using the structural interpretation results, multi-well synthetic records and forward simulation results. The multi-well synthetic records and forward simulation results of the present application are shown in Figure 4a , Figure 4b and Figure 4c . As shown in Figure 4a , when the reservoir property is good (porosity is greater than 5%), for example, xqx1 well, the reservoir seismic reflection is affected by the overlying low-velocity marl and gypsum rock layer, and the reservoir seismic reflection is submerged in the strong amplitude reflection of the overlying low-velocity gypsum rock layer. When the reservoir is not developed, the overlying low-velocity gypsum rock layer forms a 50000 amplitude reflection. When the reservoir is developed, the strong amplitude reflection peak becomes wide, and the amplitude becomes 60000 reflection. As shown in Figure 4b , when the reservoir property is poor (porosity is 3%-5%), for example, pg2011-5 well, when the reservoir is developed, it shows weak amplitude reflection or complex wave reflection. In order to further determine the reservoir seismic reflection characteristics, 30HZ Ricker wavelet is adopted, and one-dimensional wave equation forward simulation is carried out for different porosities and different development positions, as shown in Figure 4c .

[0049] The reservoir seismic reflection characteristics are classified according to the reservoir properties, the seismic reflection characteristics corresponding to the good reservoir properties are strong amplitude reflection, and the seismic reflection characteristics corresponding to the poor reservoir properties are weak amplitude or complex wave reflection. The good or poor reservoir properties are determined according to the size of the porosity, and the larger the porosity, the better the reservoir properties. In the embodiment, when the porosity is greater than 5%, it indicates that the reservoir properties are good; when the porosity is 3%-5%, it indicates that the reservoir properties are poor.

[0050] 4. The wave peak horizon of the target layer is subtracted from the wave trough horizon to obtain an interval time plane from the wave trough to the wave peak, and a high-chronology sedimentary interface is constructed by using the interval time plane.

[0051] The wave peak horizon of the target layer is subtracted from the wave trough horizon to obtain an interval time plane from the wave trough to the wave peak, and a high-chronology sedimentary interface is constructed by using the interval time plane, and the specific construction process of the high-chronology sedimentary interface is as follows:

[0052] 1) The gypsum distribution in the whole area is relatively stable, the thickness is generally 20-30 meters, and the time thickness of the wave trough to the wave peak corresponding to the top and bottom of the gypsum is basically the same on the seismic. Based on this rule, the dip angle correction is performed by subtracting the wave trough horizon of the top of the gypsum from the wave peak horizon of the bottom of the gypsum to obtain the interval time plane from the wave trough to the wave peak, as shown in FIG. 2. Figure 5

[0053] 2) The interval time plane is used for regional division, and the division rule is that when the interval time plane has a trend change and the change amplitude is greater than a time setting threshold, the time value is divided into regions according to the time setting threshold as a gradient, the trend change is related to the thickness of the reservoir, and generally the thicker the reservoir, the greater the trend change. When the interval time plane does not have a trend change or the change amplitude is less than the time setting threshold, no regional division is needed. In the embodiment, the time setting threshold is 4 ms. In the A work area of the embodiment, the interval time plane as a whole does not have a trend change, only the southern Qingxichang (xqx1 well area) and Dongyuezha (cy84 well area) regions have a trend change, and the change amplitude is about 10 ms, which is greater than 4 ms.

[0054] 3) The wave trough horizon of the southern Qingxichang and Dongyuezha regions after division is added to the interval time average 17 ms of the corresponding region, and the interval time average 17 ms is calculated through the thickness of the reservoir. In the embodiment, the thickness of the reservoir is 20-30 meters, the interval time from one wave peak to one wave trough is 14-19 ms, and in order to facilitate calculation, the interval time average selected in the embodiment is 17 ms. The smoothness is performed at the boundaries of other adjacent blocks to obtain a high-chronology sedimentary interface, as shown in FIG. 3. Figure 6

[0055] ​​5. Use the corresponding amplitude attributes to predict reservoir distribution based on different reservoir physical properties.

[0056] First, the reservoir distribution is predicted using the corresponding amplitude attributes for different reservoir physical properties. For reservoirs with good physical properties, the constructed high isochronous sedimentary interface layer is drifted downward by the set first threshold, and the maximum amplitude attribute is used to predict the reservoir distribution. For reservoirs with poor physical properties, the constructed high isochronous sedimentary interface layer is drifted downward by the set second threshold, and the minimum amplitude attribute is used to predict the reservoir distribution. The specific reservoir distribution prediction process is as follows:

[0057] A. The time interval between the reservoir with good physical properties and the low-velocity gypsum marker layer is 8 ms (reservoir velocity is 5800 m / s and thickness is 15-30 meters). The constructed high-isochronous sedimentary interface layer is drifted downward to the set first threshold (the first threshold set in this example is 8 ms) to perform maximum amplitude attribute analysis, and it is determined that this type of reservoir is mainly distributed around wells xqx1 and cy83.

[0058] B. The time interval between the reservoir with poor physical properties and the low-velocity gypsum marker layer is 5 ms (the reservoir velocity is 5900 m / s and the thickness is less than 15 meters). The sedimentary interface layer with high isochronous properties is drifted downward by the second threshold set (the second threshold set in this embodiment is 5 ms) to perform minimum amplitude attribute analysis, and it is determined that this type of reservoir is mainly distributed near the f4 well, such as Figure 7 shown.

[0059] The present invention also quantitatively predicts the thickness of the reservoir. The waveform inversion method is used to obtain the reservoir's P-wave impedance. This is then compared with a threshold for setting the P-wave impedance. The threshold for setting the P-wave impedance is related to the physical properties of the reservoir; for reservoirs with poor physical properties, the threshold is greater than for reservoirs with good physical properties. The specific process for predicting reservoir thickness is as follows:

[0060] a) Perform rock physical analysis on the target well, such as Figure 8 As shown, reservoirs with a porosity greater than 3% can be distinguished from surrounding rocks by P-wave impedance. Reservoirs with good physical properties have a P-wave impedance threshold lower than the first P-wave impedance setting value. The P-wave impedance threshold for reservoirs with good physical properties is within a set range. In this embodiment, the first P-wave impedance setting value is 1.62e+07kg / m3*m / s, and the setting range in this embodiment is 1.62e+07kg / m3*m / s to 1.70e+07kg / m3*m / s.

[0061] b) Using the waveform inversion method to obtain the reservoir P-wave impedance, the reservoir is mainly manifested as low impedance strips, such as Figure 9The reservoir thickness is quantitatively predicted by comparing the reservoir P-wave impedance obtained by the waveform inversion method and the reservoir P-wave impedance threshold value, and other inversion methods, such as a sparse pulse inversion method and a model inversion method, can also be used to obtain the reservoir P-wave impedance.

[0062] The identified reservoir is detected for oil and gas by using the post-stack low-frequency resonance, so as to determine the favorable area of the reservoir development, and other methods, such as pre-stack AVO, can also be used to detect the oil and gas of the identified reservoir.

[0063] The reservoir distribution prediction and the reservoir thickness prediction of the A work area are combined under the guidance of the sedimentary facies, so as to realize the overall analysis of the reservoir of the A work area, and the favorable area of the reservoir development of the A work area is determined by combining the oil and gas detection distribution map, the high-quality reservoir of the A work area is mainly sporadically distributed in the south of the facies change line of the work area, and well site support is provided for exploration deployment.

[0064] The above embodiment is used for identifying the thin reservoir, because the high-time sedimentary interface is constructed according to the interval time plane from the trough to the peak obtained by subtracting the trough horizon from the peak horizon of the target layer before the reservoir is identified, so the present application is not only suitable for identifying the thin reservoir, but also suitable for identifying other thickness reservoirs.

Claims

1. A method of identifying a reservoir, characterized by, The identification method comprises the following steps: 1) determining the reservoir development of the target layer by using seismic data, logging data and gas testing data of the target layer; 2) determining the wave peak and wave trough horizons of the target layer by well-to-seismic calibration and forward modeling based on the reservoir development of the target layer, and performing structural interpretation on the wave peak and wave trough horizons of the target layer; 3) determining the reservoir seismic reflection characteristics by using the structural interpretation result, multi-well synthetic record and forward modeling result; 4) obtaining the interval time plane from the wave trough to the wave peak by subtracting the wave trough horizon from the wave peak horizon of the target layer, and constructing a high-chronological sedimentary interface by using the interval time plane; 5) identifying the reservoir according to the reservoir seismic reflection characteristics determined in step 3) and the high-chronological sedimentary interface constructed in step 4).

2. The method of reservoir identification according to claim 1, wherein, The process of determining the high-chronological sedimentary interface is as follows: A. performing dip correction on the difference between the wave peak horizon and the wave trough horizon of the target layer to obtain the interval time plane from the wave trough to the wave peak; B. when the interval time plane has a trend change and the change amplitude is greater than a time set threshold, dividing the region by using the interval time plane; C. adding the interval time average of the corresponding region to the wave trough horizon of the divided region, and smoothing at the boundaries of other adjacent regions to obtain the high-chronological sedimentary interface.

3. The method of reservoir identification according to claim 1, wherein, The reservoir seismic reflection characteristics are divided according to the reservoir physical property, and the seismic reflection characteristics corresponding to the better reservoir physical property are the strong amplitude reflection of drawdown, and the seismic reflection characteristics corresponding to the poor reservoir physical property are the weak amplitude or complex wave reflection.

4. The method of reservoir identification according to claim 3, wherein, The good or bad of the reservoir physical property is determined according to the size of the porosity, and the larger the porosity is, the better the reservoir physical property is.

5. The method of reservoir identification according to claim 3, wherein, In step 5), the reservoir distribution is predicted by using the corresponding amplitude attribute for different reservoir physical properties, for the reservoir with better physical property, the constructed high-chronological sedimentary interface horizon is drifted downward by a set first threshold, and the maximum amplitude attribute is used to realize the prediction of the reservoir distribution; for the reservoir with poor physical property, the constructed high-chronological sedimentary interface horizon is drifted downward by a set second threshold, and the minimum amplitude attribute is used to realize the prediction of the reservoir distribution.

6. The method of reservoir identification according to claim 1, wherein, The identification method further comprises quantitatively predicting the thickness of the reservoir.

7. The method of reservoir identification according to claim 6, wherein, The process of the quantitative prediction is as follows: the reservoir P-wave impedance is obtained by using the inversion method, and the thickness of the reservoir is quantitatively predicted according to the comparison result of the reservoir P-wave impedance and the reservoir P-wave impedance set threshold.

8. The method of reservoir identification according to claim 7, wherein, The reservoir P-wave impedance set threshold is related to the good or bad of the reservoir physical property, and the P-wave impedance set threshold of the reservoir with poor physical property is greater than that of the reservoir with good physical property.

9. The method of reservoir identification according to claim 7, wherein, The inversion adopts waveform inversion.

10. The method of reservoir identification according to claim 1, wherein, The identification method further comprises detecting oil and gas in the identified reservoir to determine the favorable area of reservoir development.

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