Low-permeability thin interlayer bottom water reservoir fracturing key parameter optimization and effect evaluation method

Abstract

The invention relates to the technical field of oil reservoir development, in particular to a low-permeability thin interlayer bottom water oil reservoir fracturing key parameter optimization and effect evaluation method, which comprises the following steps of: calculating different fracturing parameters corresponding to different interlayer thicknesses by establishing a relationship among a fracturing effect, fracturing construction parameters and interlayer thicknesses; it is guaranteed that the reservoir is pressed open, and meanwhile the interlayer is prevented from being pressed through to communicate with bottom water; aiming at the difficulty of quantitatively evaluating the measure effect after the fracturing measure, the measure effect is quantitatively predicted and evaluated by establishing the relationship between the measure oil increasing effect and the water content and the oil layer thickness before the measure, and the method is simple and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of oil reservoir development, and is a method for optimizing key parameters and evaluating the effects of fracturing in a low-permeability, thin-layer bottom-water oil reservoir. Background Art

[0002] Fracturing is a common method for increasing production in the development of low permeability reservoirs. How to select suitable wells for fracturing and evaluate the effect after fracturing is of great significance to reservoir development. At present, microseismic monitoring is used to evaluate the fracturing effect. Zhao Chaofeng et al. proposed a set of fracturing effect evaluation methods based on microseismic monitoring in wells ("Evaluation of fracturing effect based on microseismic monitoring method in wells - taking Y22 well in Jilin exploration area as an example" Lithologic Oil and Gas Reservoirs, 2020, 32(02)). At present, microseismic monitoring is used to evaluate the fracturing effect, which is complex and costly.

[0003] Hydraulic fracturing is one of the main technical means to improve the production efficiency of low permeability oil and gas fields. The optimization design of key parameters of target wells with different geological characteristics in fracturing measures and the evaluation of the effect after the measures are the basis for ensuring the quality of the measures. Some oil wells in low permeability thin-layer bottom water reservoirs are restricted by the thin thickness of the interlayer between the oil layer and the lower water layer. During the fracturing process, it is easy to press through the interlayer to communicate with the bottom water, resulting in high water content after the measures, and there is a lack of quantitative evaluation methods for the effect of measures to verify the quality of the measures. Summary of the invention

[0004] The present invention provides a method for optimizing key parameters and evaluating the effects of fracturing in a low-permeability thin-layer bottom water reservoir, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problem of easily pressing through the barrier layer and communicating with the bottom water during the fracturing process of a low-permeability thin-layer bottom water reservoir.

[0005] The technical scheme of the present invention is achieved through the following measures: a method for optimizing key parameters and evaluating the effects of fracturing in a low-permeability thin-barrier bottom water reservoir, comprising: for a low-permeability thin-barrier bottom water reservoir, according to the relationship between a height control factor and the oil layer thickness, the barrier thickness and the amount of sand added, calculating the amount of sand added required for fracturing construction, when the height control factor K≤1, it is possible to avoid fracturing connecting to the bottom water layer, and fracturing and sand addition are performed according to the calculated value of the amount of sand added; obtaining an oil increase coefficient according to the oil layer thickness of the low-permeability thin-barrier bottom water reservoir and the water content of a target well, and calculating the oil increase level according to the relationship between the oil increase coefficient and the oil increase level.

[0006] The following are further optimizations and / or improvements to the above technical solutions:

[0007] The calculation formula of the above height control factor is as follows:

[0008] K=5*(v / h 油 ) / h 隔

[0009] h 油 ——Oil layer thickness, m, obtained after determining the target fracturing well;

[0010] h 隔 ——Interlayer thickness, m, obtained after determining the target fracturing well;

[0011] v——sand addition amount, m 3 , which is an important parameter in the design of fracturing operations and is determined according to the geological parameters of the target well;

[0012] The above formula can be used to determine the amount of sand added during fracturing (sand addition intensity). Different interlayer thicknesses correspond to different fracturing parameters (sand addition amounts). The application of the fracturing parameters ensures that the reservoir is opened while avoiding fracturing the bottom water layer.

[0013] The calculation formula of the above oil increase coefficient C is as follows:

[0014] C=(h 油 +(1-w)*10) / 3

[0015] h 油 ——Oil layer thickness, m, obtained after determining the target fracturing well;

[0016] w——water content of target well, %, obtained after determining the target fracturing well.

[0017] The above oil increase level M is calculated as follows:

[0018] M=1.59*C-2.59

[0019] M——Oil increase level, t / d,

[0020] C——Oil increase coefficient.

[0021] The present invention establishes the relationship between the fracturing effect and the fracturing construction parameters and the thickness of the interlayer, calculates the corresponding different fracturing parameters under different interlayer thicknesses, and ensures that the reservoir is opened while avoiding the interlayer being penetrated to communicate with the bottom water; in order to solve the problem of quantitatively evaluating the effect of the fracturing measures after the fracturing measures, the relationship between the oil-increasing effect of the measures and the water content and the thickness of the oil layer before the measures is established, so as to quantitatively predict and evaluate the effect of the measures, and the method is simple and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Attached Figure 1 This is the relationship diagram between sand addition strength, barrier thickness and fracturing effect.

[0023] Attached Figure 2 This is a prediction chart for oil increase effect. DETAILED DESCRIPTION

[0024] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0025] The present invention will be further described below in conjunction with embodiments:

[0026] The present invention provides a method for optimizing key parameters and evaluating the effects of fracturing in a low-permeability thin-barrier bottom water reservoir, comprising: for a low-permeability thin-barrier bottom water reservoir, according to the relationship between a height control factor and the thickness of the oil layer, the thickness of the barrier layer and the amount of sand added, calculating the amount of sand added required for fracturing construction, when the height control factor K≤1, it is possible to avoid the fracturing from communicating with the bottom water layer, and performing fracturing sand addition according to the calculated value of the amount of sand added;

[0027] The oil increase coefficient is obtained according to the oil layer thickness of the low permeability thin barrier bottom water reservoir and the water content of the target well. The oil increase level is calculated according to the relationship between the oil increase coefficient and the oil increase level.

[0028] The fracturing effect can be predicted by the oil increase level, the quality of fracturing measures can be reversely evaluated, and the efficient implementation of reservoir fracturing measures can be guided.

[0029] The inventors of this application have studied the oil layer thickness, barrier thickness, sand addition amount and oil increase level data of developed low permeability thin barrier bottom water reservoir blocks, established the mathematical relationship between the height control factor and the oil layer thickness, barrier thickness and sand addition amount, and found that when the height control factor K≤1, it is possible to avoid fracturing and connecting the bottom water layer, and have a significant oil increase effect (see Figure 1 ).

[0030] The calculation formula of the height control factor is as follows:

[0031] K=5*(v / h 油 ) / h 隔

[0032] h 油 ——Oil layer thickness, m, obtained after determining the target fracturing well;

[0033] h 隔 ——Interlayer thickness, m, obtained after determining the target fracturing well;

[0034] v——sand addition amount, m 3 , which is an important parameter in the design of fracturing operations and is determined according to the geological parameters of the target well;

[0035] The calculation formula of the height control factor can determine the amount of sand added (sand addition intensity) for fracturing construction. Different interlayer thicknesses correspond to different fracturing parameters (sand addition amounts). The application of the fracturing parameters ensures that the reservoir is opened while avoiding fracturing the bottom water layer.

[0036] The inventors of this application have established a mathematical relationship between the oil layer thickness and the water content of the target well by studying the oil layer thickness and the water content of the target well in the developed low permeability thin barrier bottom water oil reservoir block, that is, they have established an oil increase coefficient, and have established a linear relationship between the oil increase coefficient and the oil increase level. The relationship diagram between the oil increase coefficient and the oil increase level is shown in Figure 2 .

[0037] The calculation formula of the oil increase coefficient C is as follows:

[0038] C=(h 油 +(1-w)*10) / 3

[0039] h 油 ——Oil layer thickness, m, obtained after determining the target fracturing well;

[0040] w——water content of target well, %, obtained after determining the target fracturing well.

[0041] The calculation formula of the oil increase level M is as follows:

[0042] M=1.59*C-2.59(R 2 =0.8765)

[0043] M——Oil increase level, t / d,

[0044] C——Oil increase coefficient.

[0045] Implementation Cases

[0046] It is known that in a production well of the Jurassic Sangonghe Formation reservoir in Xiayan area, the oil layer thickness is h 油 4m, daily liquid production 3t / d, daily oil production 1.5t / d, water content w is 50%, the thickness of the barrier between the oil layer and the water layer h 隔 For 6m, use the height control factor relationship:

[0047] K=5*(v / h 油 ) / h 隔

[0048] h 油 ——Oil layer thickness, m;

[0049] h 隔 ——interlayer thickness, m;

[0050] v——sand addition amount, m 3 .

[0051] Under the condition that K is equal to 1, the calculated sand addition strength v is 4.8m 3 While ensuring that the reservoir is opened, avoid fracturing the bottom water layer.

[0052] Oil increase coefficient C:

[0053] C=(h 油 +(1-w)*10) / 3=(4+(1-0.5)*10) / 3=3

[0054] h 油 ——Oil layer thickness, m;

[0055] w——water content of target well, %.

[0056] Through the relationship between the oil increase level M and the oil increase coefficient C:

[0057] M=1.59*C-2.59=2.18

[0058] C——Oil increase coefficient, obtained by calculation.

[0059] According to the above formula, the calculated oil increase level M is 2.18t / d, which is close to the actual oil increase level (2.24t / d). The fracturing effect can be predicted. After construction, the quality of the measures can be reversely evaluated according to the production effect to guide the efficient implementation of reservoir fracturing measures.

[0060] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A method for optimizing key parameters and evaluating the effects of fracturing in a low permeability, thin-layer bottom water reservoir, characterized in that The method includes calculating the amount of sand added required for fracturing construction for a low-permeability thin-barrier bottom water reservoir according to the relationship between the height control factor and the oil layer thickness, the barrier thickness and the amount of sand added; when the height control factor K≤1, it is possible to avoid fracturing connecting to the bottom water layer, and fracturing and sand addition are performed according to the calculated value of the amount of sand added; obtaining an oil increase coefficient according to the oil layer thickness and the water content of a target well of a low-permeability thin-barrier bottom water reservoir, and calculating the oil increase level according to the relationship between the oil increase coefficient and the oil increase level.

2. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 1, characterized in that The calculation formula of the height control factor is as follows: K=5*(v / h 油 ) / h 隔 h 油 ——Oil layer thickness, m; h 隔 ——interlayer thickness, m; v——sand addition amount, m 3 , which is an important parameter for fracturing construction design; The above formula can be used to determine the amount of sand added during fracturing construction.

3. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 2, characterized in that The oil layer thickness is obtained after determining the target fracturing well.

4. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 2 or 3, characterized in that The thickness of the barrier layer is obtained after determining the target fracturing well.

5. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 1, 2 or 3, characterized in that The calculation formula of the oil increase coefficient C is as follows: C=(h 油 +(1-w)*10) / 3 h 油 ——Oil layer thickness, m, obtained after determining the target fracturing well; w——water content of target well, %, obtained after determining the target fracturing well.

6. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 4, characterized in that The calculation formula of the oil increase coefficient C is as follows: C=(h 油 +(1-w)*10) / 3 h 油 ——Oil layer thickness, m; w——water content of target well, %.

7. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 5, characterized in that The target well water content is obtained after determining the target fracturing well.

8. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 6, characterized in that The target well water content is obtained after the target fracturing well is determined.

9. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 5, characterized in that The calculation formula of oil increase level M is as follows: M=1.59*C-2.59 M——Oil increase level, t / d, C——Oil increase coefficient.

10. The method for optimizing key parameters and evaluating the effects of fracturing in a low permeability thin barrier bottom water reservoir according to claim 6, 7 or 8, characterized in that The calculation formula of oil increase level M is as follows: M=1.59*C-2.59 M——Oil increase level, t / d, C——Oil increase coefficient.

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