Optimal selection method for carbon dioxide sequestration layer of multi-layer heterogeneous exhausted oil and gas reservoir

Abstract

The invention discloses an optimal selection method for a carbon dioxide sequestration layer of a multi-strata heterogeneous exhausted oil and gas reservoir, and belongs to the technical field of carbon dioxide sequestration, and the optimal selection method comprises the following steps: S1, determining physical property factors of the multi-strata heterogeneous exhausted oil and gas reservoir to be evaluated; s2, determining a recovery degree factor of oil and gas recovery of the to-be-evaluated multi-layer heterogeneous exhausted oil and gas reservoir; s3, determining a stress damage factor of the to-be-evaluated multi-layer heterogeneous exhausted oil and gas reservoir; s4, obtaining an evaluation index factor according to the reservoir physical property factor, the recovery degree factor and the reservoir stress damage factor obtained in the steps S1, S2 and S3; and S5, evaluating the to-be-evaluated multi-layer heterogeneous exhausted oil and gas reservoir according to the evaluation index factor, and screening a carbon dioxide sequestration injection layer, so that accurate technical support can be provided for the carbon dioxide sequestration layer selection of the multi-layer heterogeneous exhausted oil and gas reservoir, the maximization of the injection rate of the heterogeneous reservoir can be realized, the carbon dioxide injection layer section can be screened, and the accuracy of the carbon dioxide sequestration layer selection is improved. The method is simple and can reduce the screening cost.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide sealing layers, and in particular to a method for optimizing carbon dioxide sealing layers in a multi-layer heterogeneous depleted oil and gas reservoir. Background Art

[0002] Carbon dioxide geological storage technology (CCUS) refers to the capture of carbon dioxide produced in the process of industrial and energy conversion before it is emitted, and then transported to the storage site through pipelines or ships, compressed and injected into suitable deep underground strata, and isolated from the atmosphere for a long time through physical and chemical effects. Among them, depleted oil and gas reservoirs are important places for carbon dioxide geological storage. However, most of my country's depleted oil and gas reservoirs have the characteristics of multi-layer systems and strong heterogeneity, which leads to the inability to meet the safe and efficient storage of carbon dioxide in multi-layer heterogeneous depleted oil and gas reservoirs when carbon dioxide is injected in general. In view of the above problems, it is of great significance to select the carbon dioxide storage layer of multi-layer heterogeneous depleted oil and gas reservoirs to achieve safe and efficient storage of carbon dioxide. Due to the general exploitation of multi-layer depleted oil and gas reservoirs, it is difficult to judge the carbon dioxide injection capacity of each layer of the depleted oil and gas reservoir, and it is impossible to maximize the carbon dioxide injection amount of the depleted oil and gas reservoir. At present, there is a lack of economically feasible layer selection method for carbon dioxide storage in multi-layer heterogeneous depleted oil and gas reservoirs, which cannot meet the demand for maximizing carbon dioxide storage in multi-layer heterogeneous depleted oil and gas reservoirs.

[0003] Therefore, it is urgent to invent a method for optimizing the carbon dioxide storage layers in multi-layer heterogeneous depleted oil and gas reservoirs to maximize the carbon dioxide storage in multi-layer heterogeneous depleted oil and gas reservoirs and provide technical guarantees for the safe and efficient storage of carbon dioxide in multi-layer heterogeneous depleted oil and gas reservoirs. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for optimizing the layer positions for carbon dioxide storage in multi-layer heterogeneous depleted oil and gas reservoirs. The method is simple and can accurately determine the layer positions for carbon dioxide storage in multi-layer heterogeneous depleted oil and gas reservoirs, thereby providing technical support.

[0005] The technical solution of the present invention is:

[0006] A method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir comprises the following steps:

[0007] S1. Determine the physical property factors of the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated;

[0008] S2. Determine the recovery degree factor of oil and gas from the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated;

[0009] S3. Determine the stress damage factor of the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated;

[0010] S4, obtaining an evaluation index factor according to the reservoir physical property factor, recovery degree factor, and reservoir stress damage factor obtained in steps S1, S2, and S3;

[0011] S5. Evaluate the multi-layer heterogeneous depleted oil and gas reservoirs to be evaluated based on the evaluation index factors, and select the CO2 storage injection layer.

[0012] In step S1, the method for determining reservoir physical property factors is as follows:

[0013] Assume that there are n layers in the formation, and the layers of the entire heterogeneous formation are 1, 2, 3...n (n≥2). The reservoir factor calculation method for a certain layer is as follows:

[0014]

[0015] Where: R i is the corresponding well control radius of the ith horizon, m;

[0016] k i is the permeability corresponding to the i-th layer, m;

[0017] φ i is the porosity corresponding to the i-th horizon, %;

[0018] s i is the oil / gas saturation corresponding to the ith layer, %;

[0019] H i is the oil / gas thickness corresponding to the ith layer, m;

[0020] FI is the reservoir physical property factor.

[0021] In step S2, the recovery degree factor formula is as follows:

[0022] RI=V i / H i

[0023] Where: V i is the total liquid volume of oil / gas produced, m 3 ;

[0024] H i is the reservoir thickness, m;

[0025] RI is the recovery degree factor.

[0026] In step S3, the reservoir stress damage factor formula is as follows:

[0027] DI=k' / k0

[0028] Where: k' is the reservoir permeability under effective stress, mD;

[0029] k0 is the original permeability of the reservoir, mD;

[0030] DI is the reservoir stress damage factor.

[0031] In step S4, the evaluation index factors include normalized reservoir physical property factors, recovery degree factors and stress damage factors.

[0032] The normalized reservoir physical property factor is:

[0033] F s =(FI-FI min ) / (FI max -FI min )

[0034] Where: FI is the reservoir physical property factor of multi-layer oil and gas reservoir;

[0035] FI max , FI min are the maximum and minimum reservoir physical property factors of multi-layer oil and gas reservoirs respectively;

[0036] F s is the normalized reservoir physical property factor.

[0037] The recovery degree factor after the normalization process is:

[0038] R s =(RI max -RI) / (RI max -RI min )

[0039] Where: RI is the reservoir recovery factor of multi-layer oil and gas reservoir;

[0040] RI max , RI min are the maximum and minimum recovery factors of multi-layer oil and gas reservoirs respectively;

[0041] R s is the normalized extraction degree factor.

[0042] The stress damage factor after normalization is:

[0043] D s =(DI-DI min ) / (DI max -DI min )

[0044] Where: DI is the reservoir stress damage factor of multi-layer oil and gas reservoir;

[0045] DImax ,DI min are the maximum and minimum reservoir stress damage factors of multi-layer oil and gas reservoirs;

[0046] D s is the normalized stress damage factor.

[0047] In step S5, the evaluation formula is as follows:

[0048]

[0049] Where: F s is the normalized reservoir physical property factor;

[0050] R s is the normalized extraction degree factor;

[0051] D s is the normalized stress damage factor;

[0052] SI is the layer selection index for carbon dioxide storage in multi-layer depleted oil and gas reservoirs.

[0053] The beneficial effects of the present invention are:

[0054] Through the normalization algorithm, the storage layer selection index is obtained, which can provide accurate technical support for the carbon dioxide storage layer selection in multi-layer homogeneous depleted oil and gas reservoirs, maximize the injection volume of heterogeneous reservoirs, and screen the carbon dioxide injection layer at the same time. The method is simple and reduces the layer selection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a flow chart of a method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to an embodiment of the present invention;

[0056] Figure 2 is an exponential cumulative frequency distribution diagram of a method for optimizing carbon dioxide storage layers in a multi-layer heterogeneous depleted oil and gas reservoir according to an embodiment of the present invention;

[0057] Figure 3 It is a schematic diagram of the recommended candidate layers for carbon dioxide injection in Well A1 of a method for optimizing carbon dioxide storage layers in a multi-layer heterogeneous depleted oil and gas reservoir according to an embodiment of the present invention;

[0058] Figure 4 This is a schematic diagram of a candidate layer segment for carbon dioxide injection into Well A2 of a method for optimizing carbon dioxide storage layers in a multi-layer heterogeneous depleted oil and gas reservoir according to an embodiment of the present invention;

[0059] Figure 5 It is a schematic diagram of the recommended candidate layers for carbon dioxide injection in Well A3 of a method for optimizing carbon dioxide storage layers in a multi-layer heterogeneous depleted oil and gas reservoir according to an embodiment of the present invention;

[0060] Figure 6 It is a schematic diagram of the recommended candidate layers for carbon dioxide injection in Well A4 of a method for optimizing carbon dioxide storage layers in a multi-layer heterogeneous depleted oil and gas reservoir according to an embodiment of the present invention;

[0061] Figure 7 It is a schematic diagram of the recommended candidate layers for carbon dioxide injection in the A5 well of a method for optimizing carbon dioxide storage layers in a multi-layer heterogeneous depleted oil and gas reservoir according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0063] Example:

[0064] like Figure 1 As shown, a method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir comprises the following steps:

[0065] S1. Determine the physical property factors of the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated;

[0066] Field practice and theoretical research have shown that the better the reservoir porosity, permeability, oil / gas saturation and other physical properties, the higher the carbon dioxide storage potential. At the same time, the thicker the reservoir, the greater the carbon dioxide storage potential. Therefore, the reservoir physical property factor FI is defined to characterize the carbon dioxide storage potential. The larger the value, the greater the storage potential, and vice versa. Assuming that there are n layers in the formation, the layers of the entire heterogeneous formation are 1, 2, 3...n (n≥2). The calculation method of the reservoir factor of a certain layer is as follows:

[0067]

[0068] Where: R i is the corresponding well control radius of the ith horizon, m;

[0069] k i is the permeability corresponding to the i-th layer, m;

[0070] φ i is the porosity corresponding to the i-th horizon, %;

[0071] s i is the oil / gas saturation corresponding to the ith layer, %;

[0072] H i is the oil / gas thickness corresponding to the ith layer, m.

[0073] S2. Determine the recovery degree factor of oil and gas from the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated;

[0074] The degree of recovery refers to the percentage of the cumulative geological reserves of oil and gas reservoirs during any development period. That is, the higher the degree of recovery, the greater the space released by the reservoir, and the greater the storage potential of carbon dioxide. Therefore, there is a positive correlation between the degree of recovery and the amount of oil / gas produced and the thickness of the reservoir. The degree of recovery factor is defined as the relationship between the total liquid volume produced per meter of the reservoir and the reservoir thickness. RI is defined as the degree of recovery factor, which means the degree of recovery of a single layer. The larger the value, the higher the degree of oil and gas recovery, and vice versa.

[0075] RI=V i / H i

[0076] Where: V i is the total liquid volume of oil / gas produced, m 3 ;

[0077] H i is the reservoir thickness, m;

[0078] RI is the recovery degree factor.

[0079] S3. Determine the stress damage factor of the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated;

[0080] As effective stress increases during oil and gas development, the ratio of the rock permeability at different times to the permeability when effective stress is 0 is defined. Stress sensitivity refers to the change in the pore volume (porosity) and permeability of porous media with effective stress. Therefore, the reservoir stress damage factor is defined as the ratio of the reservoir permeability under effective stress to the original permeability of the reservoir. DI is defined as the reservoir stress damage factor, which means that the permeability returns to the original permeability level after oil and gas production. The larger the value, the greater the storage potential, and vice versa.

[0081] DI=k' / k0

[0082] Where: k i is the reservoir permeability under effective stress, mD;

[0083] k0 is the original permeability of the reservoir, mD.

[0084] S4, obtaining an evaluation index factor according to the reservoir physical property factor, recovery degree factor, and reservoir stress damage factor obtained in steps S1, S2, and S3;

[0085] The reservoir physical property factors after normalization are:

[0086] F s =(FI-FI min ) / (FI max -FI min )

[0087] Where: FI is the reservoir physical property factor of multi-layer oil and gas reservoir;

[0088] FI max , FI min are the maximum and minimum reservoir physical property factors of multi-layer oil and gas reservoirs respectively;

[0089] F s is the normalized reservoir physical property factor.

[0090] The recovery degree factor after normalization is:

[0091] R s =(RI max -RI) / (RI max -RI min )

[0092] Where: RI is the reservoir recovery factor of multi-layer oil and gas reservoir;

[0093] RI max , RI min are the maximum and minimum recovery factors of multi-layer oil and gas reservoirs respectively;

[0094] R s is the normalized extraction degree factor.

[0095] The normalized stress damage factor is:

[0096] D s =(DI-DI min ) / (DI max -DI min )

[0097] Where: DI is the reservoir stress damage factor of multi-layer oil and gas reservoir;

[0098] DI max ,DI min are the maximum and minimum reservoir stress damage factors of multi-layer oil and gas reservoirs;

[0099] D s is the normalized stress damage factor.

[0100] S5. Evaluate the multi-layer heterogeneous depleted oil and gas reservoirs to be evaluated based on the evaluation index factors, and select the CO2 storage injection layer.

[0101] The evaluation formula is as follows:

[0102]

[0103] Where: F sis the normalized reservoir physical property factor;

[0104] R s is the normalized extraction degree factor;

[0105] D s is the normalized stress damage factor;

[0106] SI is the layer selection index for carbon dioxide storage in multi-layer depleted oil and gas reservoirs.

[0107] The layers are sorted according to the layer selection index and a cumulative frequency distribution diagram of the layer selection index and frequency is made. The layers are divided into three levels according to the cumulative frequency value: poor (≤33%), medium (33%-66%) and good (≥66%). The layers with the level of "good" are determined as candidate layers.

[0108] The specific cases are as follows:

[0109] Taking 5 horizontal wells in a block of sandstone reservoir A as an example, according to this method, the segment index of each segment is calculated based on the reservoir physical property factors, recovery degree factors, and reservoir stress damage factors of the sandstone oil layer, combined with the segment index model, and then the segment index is used to determine the level limit through the cumulative frequency distribution method to determine the three levels of good, medium, and poor. Figure 2 Finally, the candidate horizontal wells for repeated acidizing were selected according to the three levels.

[0110] According to the grade limit determined by the segment selection index, a good grade is selected as the target layer for carbon dioxide injection. The target layers for carbon dioxide injection in 5 depleted oil wells evaluated by the segment selection index are as follows: Figure 3-7 shown.

[0111] This technology is not only suitable for layer selection in depleted oil and gas reservoirs, but can also be used for layer selection when detecting seepage at a site, to achieve efficient carbon dioxide displacement and geological storage. It will help to overcome the problem of low carbon dioxide storage efficiency in multi-layer depleted oil and gas reservoirs in my country, and has important scientific significance and broad production application prospects.

[0112] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir, characterized in that: The steps include: S1. Determine the physical property factors of the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated; S2. Determine the recovery degree factor of oil and gas from the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated; S3. Determine the stress damage factor of the multi-layer heterogeneous depleted oil and gas reservoir to be evaluated; S4, obtaining an evaluation index factor according to the reservoir physical property factor, recovery degree factor, and reservoir stress damage factor obtained in steps S1, S2, and S3; S5. Evaluate the multi-layer heterogeneous depleted oil and gas reservoirs to be evaluated based on the evaluation index factors, and select the CO2 storage injection layer.

2. The method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to claim 1, characterized in that: In step S1, the method for determining reservoir physical property factors is as follows: Assume that there are n layers in the formation, and the layers of the entire heterogeneous formation are 1, 2, 3...n (n≥2). The reservoir factor calculation method for a certain layer is as follows: FI=3.14R i 2 k i φ i s i H i Where: R i is the corresponding well control radius of the ith horizon, m; k i is the permeability corresponding to the i-th layer, m; φ i is the porosity corresponding to the i-th horizon, %; s i is the oil / gas saturation corresponding to the ith layer, %; H i is the oil / gas thickness corresponding to the ith layer, m; FI is the reservoir property factor.

3. The method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to claim 1, characterized in that: In step S2, the recovery degree factor is determined by the following formula: RI=V i / H i Where: V i is the total liquid volume of oil / gas produced, m 3 ; H i is the reservoir thickness, m; RI is the recovery degree factor.

4. The method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to claim 1, characterized in that: In step S3, the reservoir stress damage factor is determined by the following formula: DI=k'k0 Where: k i is the reservoir permeability under effective stress, mD; k0 is the original permeability of the reservoir, mD; DI is the reservoir stress damage factor.

5. The method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to claim 1, characterized in that: In step S4, the evaluation index factors include normalized reservoir physical property factors, recovery degree factors and stress damage factors.

6. The method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to claim 5, characterized in that: The normalized reservoir physical property factor is: F s =(FI-FI min )(BE max -BE min ) Where: FI is the reservoir physical property factor of multi-layer oil and gas reservoir; FI max , FI min are the maximum and minimum reservoir physical property factors of multi-layer oil and gas reservoirs respectively; F s is the normalized reservoir physical property factor.

7. The method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to claim 5, characterized in that: The recovery degree factor after the normalization process is: R s =(RI max -RI)(RI max -RI min ) Where: RI is the reservoir recovery factor of multi-layer oil and gas reservoir; RI max , RI min are the maximum and minimum recovery factors of multi-layer oil and gas reservoirs respectively; R s is the normalized extraction degree factor.

8. The method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to claim 5, characterized in that: The stress damage factor after normalization is: D s =(TUE-TUE min )(DI max -DI min ) Where: DI is the reservoir stress damage factor of multi-layer oil and gas reservoir; DI max ,DI min are the maximum and minimum reservoir stress damage factors of multi-layer oil and gas reservoirs; D s is the normalized stress damage factor.

9. A method for optimizing the carbon dioxide storage layer in a multi-layer heterogeneous depleted oil and gas reservoir according to any one of claims 1 to 8, characterized in that: In step S5, the evaluation formula is as follows: Where: F s is the normalized reservoir physical property factor; R s is the normalized extraction degree factor; D s is the normalized stress damage factor; SI is the layer selection index for carbon dioxide storage in multi-layer depleted oil and gas reservoirs.

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