History matching permeability adjustment method for oil and gas reservoir numerical model

Abstract

The present invention discloses a method for adjusting the permeability of a historical matching oil and gas reservoir numerical model, comprising the following steps: establishing a geological model that reflects the permeability distribution of a formation plane and includes a production well, dividing the grid near the well into a plurality of circles, treating each circle as an independent seepage resistance body, calculating the average permeability and the characteristic length of the seepage resistance body in parallel between the grids in each circle, and then calculating the average permeability of each seepage resistance body in series; using the ratio of the average permeability to the inversion permeability of the well test as an adjustment multiple, and when the adjustment multiple is between 1.5 and 0.5, multiplying the original grid permeability by the adjustment multiple, reassigning it to the grid of the geological model, and recalculating a new average permeability of the formation, until the adjustment multiple meets the interval condition. The present invention solves the problem that the average permeability obtained by inversion cannot match the average permeability in the forward numerical model.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development simulation, in particular to a history matching permeability adjustment method for an oil and gas reservoir numerical model. Background Art

[0002] The theoretical basis of oil and gas field development engineering is reservoir engineering. From the 1980s to the beginning of this century, reservoir engineering was mainly based on inversion methods. In the past 20 years, it has been mainly based on forward modeling methods of reservoir numerical simulation. In the past 10 years, a large number of studies have hoped to apply the conclusions obtained from inversion calculations of reservoir engineering to forward modeling research of reservoir numerical simulation, but there is still no quantitative and accurate method.

[0003] Well test analysis is the most accurate inversion method in reservoir engineering, which can invert the average permeability near the extraction well. However, the average formation permeability extracted by well test analysis is usually difficult to match with the average permeability set in numerical simulation, and there is even a significant difference in order of magnitude. This is because the permeability extracted by well test inversion analysis is based on the average permeability of flow direction and flow form, while the permeability calculated by reservoir numerical simulation is based on area-weighted average. Due to the heterogeneity and anisotropy of permeability, the two average permeability calculation methods are very different and cannot be directly integrated and applied. Summary of the invention

[0004] To solve at least one of the above problems, the present invention proposes a history matching permeability adjustment method for an oil and gas reservoir numerical model.

[0005] The technical solution of the present invention is: a historical matching permeability adjustment method for an oil and gas reservoir numerical model, comprising the following steps:

[0006] S1. Collect data, establish a geological model that reflects the permeability distribution of the formation plane and includes production wells, perform grid division, and obtain the permeability of each grid and the two-dimensional size of the grid;

[0007] S2. Based on the flow state of the geological model, with the well as the center, the grid system of the production area around the well in the original geological model is divided into several circles according to the principle of the shortest distance to the well, and the thickness of each circle is one grid;

[0008] S3, each circle is regarded as a seepage resistance body, and the average permeability of each circle is calculated, wherein all grids in each circle are averagely calculated in parallel, and the average characteristic length of each circle is calculated at the same time; then, the seepage resistance body of each circle is connected in series to calculate the average permeability, and the average permeability is the average permeability considering the flow direction;

[0009] S4. The ratio of the calculated average permeability to the well test inversion permeability is used as an adjustment factor. When the adjustment factor is not less than 1.5 or not greater than 0.5, the original grid permeability is multiplied by the adjustment factor and reassigned to the grid of the geological model. The new average formation permeability and the adjustment factor are recalculated until the adjustment factor is less than 1.5 and greater than 0.5. At this time, the corrected average permeability is the average permeability of the geological model taking into account the flow characteristics.

[0010] The beneficial effect of the present invention is that the patent of the present invention solves the problem that the average permeability obtained by inversion cannot match the average permeability in the forward numerical model, laying a foundation for accurately completing historical matching and numerical simulation work. Compared with the prior art, the present invention has higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The diagram is a schematic diagram of the layer division of the geological model of the present invention (taking three layers as an example);

[0012] Figure 2 is a permeability diagram of the geological model in the x direction in the embodiment;

[0013] Figure 3 is a permeability diagram of the geological model in the y direction in the embodiment;

[0014] Figure 4 is a grid diagram of the geological model in the x direction in the embodiment;

[0015] Figure 5 is a grid diagram of the geological model in the y direction in the embodiment;

[0016] Figure 6 It is a comparison chart of the method of the present invention, the prior art and the actual gas production curve. DETAILED DESCRIPTION

[0017] The specific implementation modes of the present invention will be described clearly and completely below with reference to examples and drawings. Obviously, the described examples are only some embodiments of the present invention, rather than all embodiments.

[0018] A history matching permeability adjustment method for an oil and gas reservoir numerical model comprises the following steps:

[0019] S1. Collect data, establish a geological model that reflects the permeability distribution of the formation plane and includes production wells, perform grid division, and obtain the permeability of each grid and the two-dimensional size of the grid;

[0020] Specifically, the collected data include well data, formation parameters, seismic parameters, logging data and interpretation data, production data, and well test analysis data. These data are commonly used in the development process and are easy to collect. These data can be further subdivided: well data include structural location, core filling elevation, well depth, wellbore trajectory, wellbore structure, completed drilling layer, horizontal section length and oil and casing size; formation parameters include porosity, permeability, gas saturation, fluid PVT parameters and continuous thickness of Class I reservoirs; logging data and interpretation data include: sub-layer division, reservoir physical parameters and natural fractures; production data include single well production data, including daily gas production, daily liquid production, casing pressure, oil pressure and bottom hole flow pressure. These data are commonly used in the process of establishing geological models.

[0021] The above-mentioned geological model can be established by conventional methods in the art. In this embodiment, the geological model is established by using the Petrel geological modeling and numerical simulation technology platform, and the model is meshed. Those skilled in the art can also use other methods and other software to establish the corresponding geological model. At the same time, considering anisotropy, the direction of the grid is required to be consistent with the direction of the production well.

[0022] In this example, the main area of ​​the Triassic reservoir in the lower oil formation of the ninth district of Tahe is taken as the target block, the target well is a horizontal well, and the horizontal length of the horizontal well is 312m. Figures 2 to 5 As shown in the figure, Figure 2 is a permeability diagram of the geological model in the x direction in the embodiment; Figure 3 is a permeability diagram of the geological model in the y direction in the embodiment; Figure 4 is a grid diagram of the geological model in the x direction in the embodiment; Figure 5 It is a grid diagram of the geological model in the y direction in the embodiment. Figure 2 to Figure 4 In the figure, the horizontal lines in the grid are horizontal wells.

[0023] S2. Based on the flow state of the geological model, with the well as the center, the grid system of the production area around the well in the original geological model is divided into several circles according to the principle of the shortest distance to the well, and the thickness of each circle is one grid;

[0024] For vertical wells, the flow state is mainly plane runoff; for horizontal wells, the flow state is mainly layered linear flow. Therefore, in the process of dividing circles, the horizontal well is centered on the well and gradually expands outward to divide different circles, and the outermost circle reaches the detection radius extracted by the well test analysis; for vertical wells, they can be regarded as horizontal wells with a length of 0, and the division method of horizontal wells can be referred to when dividing circles.

[0025] The method of dividing the circles is to take the well as the center, and divide all the grids that are directly in contact with the grid where the well is located into the first circle of grids, and divide the grids that are directly in contact with the first circle of grids into the second circle of grids, and repeat this process until all grids are divided. For a horizontal well, it can be divided into one or more grids, and then as the 0th circle, and then all the grids that are directly in contact with the 0th circle are regarded as the 1st circle, and so on. For details of this division method, please refer to Figure 1 ,In the figure, the center is the horizontal well, which is divided into 7 grids and 3 circles outside, in order to facilitate subsequent calculation and identification.

[0026] In this embodiment, if Figure 5 As shown, the framed part in the figure is the detection range extracted by the well test analysis. It can be seen from the figure that the simulation of this embodiment is divided into 5 circles.

[0027] S3. Each circle is regarded as a seepage resistance body, and the average permeability of each circle is calculated. The permeability of all grids in each circle is averaged in parallel, and the average characteristic length of each circle is calculated at the same time. Then, the seepage resistance body of each circle is connected in series to calculate the average permeability, which is the average permeability considering the flow direction.

[0028] The corrected average permeability is calculated by the following formula: Where a represents the grid circle number, and a = 1, 2, ..., A; A represents the maximum circle number, represents the average grid characteristic length of the a-th circle; is the corrected average permeability of the ath layer. In this calculation formula, each layer is regarded as an independent seepage resistance body, and the seepage resistance bodies are regarded as connected in series.

[0029] for In general, it is calculated using the following formula: In the formula, i represents the starting point of the production well in the x direction; i+n represents the end point of the production well in the x direction; j represents the starting point of the production well in the y direction; ky represents the permeability in the y direction; m represents the cumulative cycle variable, from the cycle subscript to the cycle superscript, for example, in the calculation of A In, m=-a,-a+1...a+n-1, a+n.

[0030] Among them, when calculating the average permeability within each circle When each circle is regarded as an independent seepage resistance body, the grids in the circle are connected in parallel to calculate the average permeability of the circle. In this embodiment, the following formula is used for calculation: And A and B are calculated by the following formula:

[0031]

[0032] Where ky represents the permeability in the y direction; kx represents the permeability in the x direction; and m represents the cumulative cycle variable.

[0033] S4. The ratio of the calculated average permeability to the well test inversion permeability is used as an adjustment factor. When the adjustment factor is not less than 1.5 or not greater than 0.5, the original grid permeability is multiplied by the adjustment factor and reassigned to the grid of the geological model. The new average formation permeability and the adjustment factor are recalculated until the adjustment factor is less than 1.5 and greater than 0.5. At this time, the corrected average permeability is the average permeability of the geological model taking into account the flow characteristics.

[0034] In this embodiment, according to the well test analysis, the average permeability in the producing area is 142 mD. The corrected average permeability obtained by the first calculation using the method of this embodiment is 2191 mD, and the adjustment factor is 15.31, which is greater than 1.5.

[0035] Then the average permeability of the five layers was divided by 15.31 at the same time. Taking into account the grid size and the anisotropy of the permeability, the iteration was repeated 6 times. The final calculated corrected average permeability was 159.52 mD, and the adjustment factor was 1.12, which was less than 1.5. Therefore, the corrected average permeability was set as the permeability of the local geological model.

[0036] In order to verify the accuracy of the permeability optimized by the embodiment of the present invention, the permeability optimized by the method of the present invention was brought into the model for simulation, and the obtained results were compared with the actual gas production. The final results are as follows: Figure 6 As shown; as a comparison, the present invention also provides the results obtained by fitting the permeability obtained by the prior art.

[0037] In the figure, the conventional method fitting refers to the permeability calculated by area weighted average; the new method refers to the method of the embodiment of the present invention. Among them, the conventional method is used to fit the production dynamics of 60 days. After fitting, the maximum error is 24.52%, the minimum error is 2.81%, and the average error is 14.25%; while the new method is used to fit the production dynamics of 60 days. After fitting, the maximum error is 14.94%, the minimum error is 0.02%, and the average error is 4.06%, and the fitting accuracy is better. It can be seen from the figure that the results obtained in this embodiment are more accurate when applied to the model.

[0038] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for adjusting the permeability of a historical matching oil and gas reservoir numerical model, characterized in that: The following steps are involved: S1. Collect data, establish a geological model that reflects the permeability distribution of the formation plane and includes production wells, perform grid division, and obtain the permeability of each grid and the two-dimensional size of the grid; S2. Based on the flow state of the geological model, with the well as the center, the grid system of the production area around the well in the original geological model is divided into several circles according to the principle of the shortest distance to the well, and the thickness of each circle is one grid; S3, each circle is regarded as a seepage resistance body, and the average permeability of each circle is calculated, wherein all grids in each circle are averagely calculated in parallel, and the average characteristic length of each circle is calculated at the same time; Then, the seepage resistance bodies of each circle are connected in series to calculate the average permeability, which is the average permeability considering the flow direction; S4. The ratio of the calculated average permeability to the well test inversion permeability is used as an adjustment factor. When the adjustment factor is not less than 1.5 or not greater than 0.5, the original grid permeability is multiplied by the adjustment factor and reassigned to the grid of the geological model. The new average formation permeability and the adjustment factor are recalculated until the adjustment factor is less than 1.5 and greater than 0.

5. At this time, the corrected average permeability is the average permeability of the geological model taking into account the flow characteristics.

2. The method according to claim 1, characterized in that The data include well data, formation parameters, seismic parameters, logging information and interpretation data, production data, and well test analysis data.

3. The method according to claim 2, characterized in that The well data include structural location, core elevation, well depth, wellbore trajectory, wellbore structure, completed layer, horizontal section length and oil and casing size; the formation parameters include porosity, permeability, gas saturation, fluid PVT parameters and continuous thickness of Class I reservoirs; the seismic parameters include structural interpretation results, fault and natural fracture prediction attributes and artificial fracture inversion attribute parameters; the logging information and interpretation data include: sub-layer division, reservoir physical parameters and natural fractures; the production data include single well production data, including daily gas production, daily liquid production, casing pressure, oil pressure and bottom hole flowing pressure.

4. The method according to claim 1, characterized in that: After the geological model is established, the model is meshed, and the grid direction is consistent with the direction of the production wells.

5. The method according to claim 1, characterized in that The corrected average permeability is calculated by the following formula: Where a represents the grid circle number, and a = 1, 2, ..., A; A represents the maximum circle number, represents the average grid characteristic length of the ath circle layer; is the corrected average permeability of the ath layer.

6. The method according to claim 1, characterized in that The method of dividing the circles is to take the well as the center, divide all the grids directly in contact with the grid where the well is located into the grids of the first circle, and divide the grids directly in contact with the first circle into the grids of the second circle, and repeat this process until all the grids are divided.

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