Regulation and control method for fracture-seepage conversion of fractured reservoir

Abstract

The invention discloses a regulation and control method for fracture-seepage conversion of a fractured oil reservoir, which comprises the following steps of: (1) determining the size range of an oil reservoir fracture according to analysis of earthquake and imaging logging information; (2) selecting variable particles matched with oil reservoir fractures according to the sizes of the fractures; (3) preparing a variable particle working solution by using on-site water; fourthly, variable particle working fluid is injected into the fractured reservoir; (V) closing the well; and VI, after well shut-in is finished, low-frequency well opening production is carried out, the frequency is gradually increased according to geological requirements, and normal production is carried out. According to the method, the original fracture flow of the fractured reservoir can be converted into matrix seepage, the heterogeneity of the fractured reservoir is greatly reduced, and then the development effect of the fractured reservoir is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil extraction, and in particular relates to a control method for fracture-permeability conversion in fractured oil reservoirs. Background Art

[0002] Fractured oil and gas reservoirs play a crucial role in global oil and gas distribution, accounting for approximately 50% of global reserves and over 60% of global production. Fractured reservoirs have become a key area for increasing reserves and production both domestically and internationally. However, due to their dual-media characteristics, fractured reservoirs exhibit significant permeability differences between fractures and between the fractures and matrix, leading to significant heterogeneity. During oilfield development, formation water or injected water can break through large fractures into the wellbore, causing a rapid increase in water cut in the well and inhibiting the productivity of smaller and medium-sized fractures or the matrix. Therefore, water control and plugging in fractured reservoirs is the primary approach to stabilizing oil production and controlling water loss in these reservoirs. At present, conventional chemical plugging agents such as gel, cement, and resin have been used on site. However, due to their strong plugging ability, cracks are easily blocked after use, resulting in a significant drop in production capacity. Mechanical water control devices such as AICD, ICD, and water control valves can only act within the wellbore and cannot treat the reservoir, nor can they fundamentally solve the problem of reservoir heterogeneity. Both of the above methods cannot meet the needs of stabilizing oil and controlling water in fractured oil reservoirs.

[0003] Therefore, this field urgently needs a method for regulating the conversion of fracture seepage in fractured oil reservoirs, which can convert fracture flow into matrix seepage, significantly reduce the heterogeneity of fractured oil reservoirs, and thus achieve uniform output of fractured oil reservoirs and improve development effects. Summary of the Invention

[0004] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a method for regulating fracture-permeability conversion in fractured oil reservoirs.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for regulating fracture-permeability conversion in a fractured oil reservoir, comprising the following steps:

[0007] (I) Based on the analysis of seismic and imaging logging data, the size range of reservoir fractures is determined;

[0008] (II) Selecting variable particles that match the reservoir fractures based on fracture size;

[0009] (III) Using on-site water to prepare variable particle working fluid

[0010] (IV) Injecting variable particle working fluid into fractured reservoirs. Since the fracture size is much larger than the matrix pore throat size, the variable particles mainly enter the fractures.

[0011] (V) shutting down the well;

[0012] (VI) After the well is shut in, the well is opened for production at a low frequency, and the frequency is gradually increased according to geological requirements to switch to normal production to prevent particle spitting failure.

[0013] In the above technical solution, the size of the reservoir fractures in step (I) is usually in the range of micrometers to millimeters.

[0014] In the above technical solution, the variable particles in step (II) are any one or more of organic bentonite particles, pre-crosslinked gel particles, and oil-soluble resin particles.

[0015] In the above technical solution, the particle size of the variable particles in step (II) is 1 / 6 to 1 / 3 of the fracture size; at the reservoir temperature, the variable particles take 3 to 5 days to fully expand or adhere.

[0016] In the above technical solution, the mass concentration of the variable particle working solution in step (III) is 1% to 5%.

[0017] In the above technical solution, in step (IV), the variable particle working fluid is injected into the fractured reservoir by means of a plunger pump; the plunger pump is any one of an electric drive profile control pump, an oil drive acidizing pump or an oil drive mud pump.

[0018] In the above technical solution, the well shut-in period is 3 to 5 days. Under reservoir temperature conditions, the variable particles will gradually expand or adhere to each other within 3 to 5 days to form large particle clusters, which fill the fractures and transform the original fracture flow into matrix seepage. Due to the pores between the large particle clusters, the fracture flow still has good permeability after being transformed into matrix seepage.

[0019] In the above technical solution, the frequency increase in step (VI) varies from oil field to oil field, and is generally performed at a frequency of 1 Hz to 5 Hz.

[0020] The beneficial effects of the present invention are:

[0021] The present invention provides a method for regulating fracture-seepage conversion in fractured reservoirs. By injecting variable particles into the fractured reservoir, the fracture flow can be converted into matrix seepage, significantly reducing the heterogeneity of the fractured reservoir, thereby achieving uniform output of the fractured reservoir and improving the development effect. This provides a new technical approach for solving the difficult problem of stabilizing oil and controlling water in fractured reservoirs.

[0022] The variable particles used in the present invention are one or more of organic bentonite particles, pre-crosslinked gel particles, and oil-soluble resin particles. The particle size is mainly determined according to the crack size, and the variable particle diameter is generally 1 / 6 to 1 / 3 of the crack size. The variable particle working fluid can be prepared with on-site water at a mass ratio of 1% to 5%. At the reservoir temperature, the particles fully expand or adhere to each other in 3 to 5 days. The variable particles will gradually expand and become larger or adhere to each other within 3 to 5 days to form large particle clusters, so that the original crack flow is converted into matrix seepage. Due to the pores between the large particle clusters, it is ensured that the crack flow still has good permeability after being converted into matrix seepage. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the method flow of the present invention;

[0024] Figure 2 This is a schematic diagram of the original fracture development before the fracture reservoir is treated in Example 1 of the present invention;

[0025] Figure 3 This is a schematic diagram of variable particles filled in the original fractures after the fractured oil reservoir is treated in Example 1 of the present invention.

[0026] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0028] Example 1

[0029] Well A has a formation temperature of 80°C, well-developed fractures, and a daily fluid production of 350.5 m 3 / d, daily oil production 14.1m 3 / d, the water content is 96.0%, and the production enters the high water content stage. The control method of fracture permeability conversion in fractured reservoirs is implemented according to the following steps:

[0030] ① According to the analysis of seismic and imaging logging data, the average width of the fracture is 210μm;

[0031] ②. According to the crack size, select the particle size of pre-crosslinked gel particles from 35μm to 70μm;

[0032] ③. Use on-site water at a mass ratio of 3% to prepare the pre-crosslinked gel particle working solution;

[0033] ④, with the help of oil flooding acidification pump, the displacement is controlled at 20m 3 / h~30m 3 / h, inject 3% pre-crosslinked gel particles into the fractured reservoir at 500m 3 ;

[0034] ⑤ After shutting in the well for 3 days, under the reservoir temperature conditions, the pre-crosslinked gel particles will gradually expand and grow to form large particle clusters;

[0035] ⑥. Start production at a frequency of 25 Hz, and gradually increase the frequency to 35 Hz according to geological requirements, and switch to normal production.

[0036] After following the above steps, Well A produced 232.4m3 of liquid per day. 3 / d, daily oil production 31.3m 3 / d, the water content is 86.5%, and the effect of stabilizing oil and controlling water is obvious.

[0037] Example 2

[0038] Well B has a formation temperature of 92°C, well-developed fractures, and a daily fluid production of 437.2 m 3 / d, daily oil production 21.4m 3 / d, the water content is 95.1%, and the production enters the high water content stage. The control method of fracture permeability conversion in fractured reservoirs is implemented according to the following steps:

[0039] ① According to the analysis of seismic and imaging logging data, the average width of the fracture is 852μm;

[0040] ②. According to the crack size, select the oil-soluble resin particles with a particle size of 140μm to 280μm;

[0041] ③. Use on-site water at a mass ratio of 2% to prepare the oil-soluble resin particle working fluid;

[0042] ④, with the help of oil drive acidification pump, the displacement is controlled at 15m 3 / h~25m 3 / h, inject 650m3 of 2% oil-soluble resin particles into the fractured reservoir 3 ;

[0043] ⑤ After shutting in the well for 5 days, under the reservoir temperature conditions, the oil-soluble resin particles adhered to each other and formed large particle clusters;

[0044] ⑥. Start production at a frequency of 28 Hz, and gradually increase the frequency to 40 Hz according to geological requirements, and switch to normal production.

[0045] After following the above steps, Well A produced 394.5m3 of liquid per day. 3 / d, daily oil production 35.6m 3 / d, the water content is 91.0%, and the effect of stabilizing oil and controlling water is obvious.

[0046] The schematic diagram of the fracture reservoir before and after the above steps is as follows Figure 2 、 3 As shown. Figure 2 The natural fractures developed in the reservoir are shown in FIG. Figure 3 The figure shows that filling natural fractures with variable particles can transform fracture flow into matrix seepage.

[0047] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for controlling fracture-permeability conversion in fractured oil reservoirs, characterized by: The following steps are involved: (I) Based on the analysis of seismic and imaging logging data, the size range of reservoir fractures is determined; (II) Selecting variable particles that match the reservoir fractures based on fracture size; (III) Using on-site water to prepare variable particle working fluid; (IV) injecting variable particle working fluid into fractured reservoirs; (V) shutting down the well; (VI) After the well is shut in, the well is opened for production at a low frequency, and the frequency is gradually increased according to geological requirements to return to normal production.

2. The method for controlling fracture-permeability conversion in fractured oil reservoirs according to claim 1, characterized in that: The variable particles in step (II) are any one or more of organic bentonite particles, pre-crosslinked gel particles, and oil-soluble resin particles.

3. The method for controlling fracture-permeability conversion in fractured oil reservoirs according to claim 1, characterized in that: The particle size of the variable particles in step (II) is 1 / 6 to 1 / 3 of the fracture size; at the reservoir temperature, the variable particles take 3 to 5 days to fully expand or adhere.

4. The method for controlling fracture-permeability conversion in fractured oil reservoirs according to claim 1, characterized in that: The mass concentration of the variable particle working solution in step (III) is 1% to 5%.

5. The method for controlling fracture-permeability conversion in fractured oil reservoirs according to claim 1, characterized in that: In step (IV), the variable particle working fluid is injected into the fractured reservoir by means of a plunger pump; the plunger pump is any one of an electric drive profile control pump, an oil drive acidizing pump or an oil drive mud pump.

6. The method for controlling fracture-permeability conversion in fractured oil reservoirs according to claim 1, characterized in that: The well closure time is 3 to 5 days.

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