Method for guiding fracturing temporary plugging construction by utilizing stepped displacement reduction test

Abstract

The invention provides a method for guiding fracturing temporary plugging construction by utilizing a stepped displacement reduction test, and belongs to the technical field of unconventional petroleum and natural gas yield increase. Comprising the following steps that S1, after the first sand carrying stage is finished, the change of bottom hole pressure in the fracturing process is tested, and the bottom hole pressure and the injection displacement corresponding to a stepped descent point are selected in the displacement reduction stage; s2, the displacement reduction test data are imported into fracturing simulation software, and the hole friction resistance pressure drop is calculated; s3, determining the aperture size and distribution of the erosion shot holes in the section according to the calculation result of the friction resistance pressure drop of the shot holes; and S4, calculating the particle sizes and the feeding amounts of the temporary plugging balls and the temporary plugging particles. And S5, finishing the fracturing temporary plugging construction of the first section, repeating the steps S1 to S4, and carrying out a displacement reduction test on the rest sections to be fractured after the sand carrying stage is finished. According to the method, the competition expansion and fluid distribution rule of the hole friction to the multi-cluster cracks in the section can be determined, the size and distribution of the hole diameters in the section are determined, and the temporary plugging construction success rate and the reservoir transformation effect are improved.

Description

Technical Field

[0001] This invention relates to the field of unconventional oil and gas production enhancement technology, and in particular to a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test. Specifically, it is a method for guiding the type and amount of temporary plugging material used in multi-cluster directional fracturing of horizontal wells using a stepped reduction displacement test. Background Technology

[0002] In recent years, with the development of unconventional oil and gas, fracturing technology has evolved from conventional proppant fracturing to large-scale, high-volume volumetric fracturing, and then to close-cutting temporary plugging fracturing. Fracturing technology has gradually improved and upgraded, becoming more suitable for increasing production in unconventional oil and gas reservoirs. Among these technologies, close-cutting multi-cluster fracturing has been widely used in shale and tight oil and gas development.

[0003] Due to the high initiation pressure gradient of the reservoir, excessively large fracture spacing can lead to unexploded areas within the horizontal section, hindering production enhancement. Close-cut multi-cluster fracturing maximizes reservoir stimulation. However, this method has certain blind spots. Due to heterogeneity between perforation clusters and their locations, the uniformity of fracturing varies between clusters and even between individual perforations within a cluster, sometimes resulting in unexploded clusters or incomplete fracturing in all directions. To improve reservoir stimulation uniformity, temporary plugging materials can be used during fracturing to seal fractured perforations, directing proppant-carrying fluids towards unexploded perforations, thus achieving uniform fracturing across multiple clusters within the section. From a temporary plugging perspective, the effectiveness of sealing existing perforated clusters or perforations within the section closely affects the overall swept volume and fracturing stimulation effect.

[0004] With the development of temporary plugging and diversion technology, existing temporary plugging materials are mainly divided into types such as temporary plugging balls, temporary plugging knots, temporary plugging particles, and temporary plugging powders. Among them, temporary plugging particles and balls have large particle sizes, typically 5-30mm. Their main function is to seal the perforated holes, thereby increasing the net pressure inside the wellbore, causing the formation in the unopened perforation cluster to fracture, achieving fluid diversion, and ultimately increasing the effective stimulation volume. The dosage and particle size selection of temporary plugging particles and balls are closely related to the success of temporary plugging and diversion. In actual field implementation, if the dosage of temporary plugging balls and particles is too small, it is difficult to effectively seal the eroded perforations, failing to achieve the construction objective and leading to construction failure. When the dosage is too large, it will cause unnecessary cost waste, and on the other hand, it may cause difficulties in subsequent sand addition and sand blockage. However, at present, the selection of temporary plugging material type, timing of deployment, and dosage are mainly determined by the experience of designers. There is no method with strong matching with single wells to find the optimal solution for the use of temporary plugging particles and balls. Therefore, there is a lack of an effective means to precisely guide the temporary plugging construction. To guide fracturing and temporary plugging operations, improve the success rate of temporary plugging operations and the effect of reservoir stimulation, it is urgent to propose a method to optimize the dosage and particle size of temporary plugging materials. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test. The technical problem to be solved by this invention is to provide a method that can determine the competitive propagation and fluid distribution law of multiple clusters of fractures within a section due to pore friction, determine the pore size and distribution within the section, improve the scientific nature of the design of the particle size and dosage of the temporary plugging material, and thus guide fracturing and temporary plugging operations, improve the success rate of temporary plugging operations and the reservoir stimulation effect.

[0006] To address the aforementioned technical problems, this invention provides a method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test, comprising the following steps:

[0007] S1. After the first sand-carrying stage is completed, the temporary plugging construction of the first fracturing stage is started to test the change of bottom hole pressure during fracturing. In the step-down stage of fracturing construction, the bottom hole pressure and injection flow rate corresponding to the step-down point are selected to obtain the step-down test data.

[0008] S2. Import the reduced discharge test data into the fracturing simulation software to calculate the perforation friction pressure drop, near-wellbore bending friction pressure drop and total friction at the fracture inlet.

[0009] S3. By calculating the pressure drop of the perforation friction, determine the size and distribution of the erosion holes in the fracturing section;

[0010] S4. Based on the size and distribution of the erosion boreholes, calculate the particle size and dosage of the temporary plugging balls and temporary plugging particles.

[0011] S5. After the temporary plugging construction of this fracturing section is completed, repeat steps S1 to S4 to conduct a reduction in discharge rate test after the sand-carrying stage of the remaining fracturing sections.

[0012] Furthermore, in step S1, the fracturing process is tested by injecting a set amount of construction fluid into the formation in a step-decreasing manner with a set displacement, setting 3-5 time steps, and using a preset rate of decreasing displacement to keep the net pressure in the fracture constant.

[0013] Furthermore, in step S1, the displacement of each step is reduced to 0.2-0.5m. 3 / min, until the displacement drops to zero, with the displacement of the last step maintained at 1.0m. 3 / min or above.

[0014] Furthermore, in step S1, the injected construction fluid is any one of guar gum fracturing fluid, emulsion fracturing fluid, organic fracturing fluid, foam fracturing fluid, and synthetic polymer fracturing fluid.

[0015] Furthermore, in step S2, the voltage drop Δp due to the frictional resistance of the aperture is...pref The calculation formula is as follows:

[0016] Δp pref =k pref Q 2

[0017] Where Q is the construction displacement, m 3 / min,k pref The coefficient of friction of the pores;

[0018]

[0019] Where ρ is the density of the fracturing fluid, kg / m³ 3 C is the orifice flow coefficient, dimensionless, with a value of 0.85; N is the number of orifices, dimensionless; D pref The diameter of the aperture.

[0020] Furthermore, in step S2, the near-wellbore bending friction Δp nub The calculation formula is as follows:

[0021] Δp nub =k nub Q β

[0022] Where, k nub The data was obtained by fitting the step-down displacement test data; Q is the displacement, m 3 / min; β is an empirical coefficient, dimensionless, with a value of 0.5.

[0023] Furthermore, in step S2, the total frictional resistance Δp at the crack inlet... entry The calculation formula is as follows:

[0024] Δp entry =Δp pref +Δp nub .

[0025] Furthermore, in step S3, the aperture D of the erosion hole is calculated using the following formula:

[0026]

[0027] Where D is the diameter of the erosion hole (mm); Q is the construction discharge rate (m³). 3 / min; ρ is the density of the fracturing fluid, kg / m³ 3 ;ΔP pref ρ is the pressure drop due to orifice friction, MPa; C is the orifice flow coefficient, dimensionless.

[0028] Furthermore, in step S4, based on the calculation results of the erosion hole diameter, the optimal particle size and dosage of the temporary plugging knot and the temporary plugging ball are selected, with the diameter of the temporary plugging ball being 1.05 to 1.5 times the diameter of the perforation hole.

[0029] The present invention provides a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test, which has the following beneficial effects:

[0030] By systematically and quantitatively analyzing the size and distribution of perforated holes, and utilizing the dropout test, which is the easiest to obtain in the field and most directly reflects the fracturing pressure, the analysis simultaneously yields the fracture closure pressure, perforation hole friction, and near-wellbore bending friction coefficient. On the one hand, the step dropout test method provides a large number of interpretable parameters, enriching the application range of step dropout test fracturing data and saving costs by eliminating the need for dedicated fracturing test procedures to determine fracture closure pressure.

[0031] On the other hand, the interpretation of the closure pressure is used instead of the assumed closure pressure for interpretation, thereby improving the accuracy and reliability of the interpretation of hydraulic fracturing perforation friction and near-wellbore bending friction. This provides a more accurate and effective reference and guidance for the selection of temporary plugging materials, the optimization design of single-well fracturing temporary plugging, and on-site construction. The method is highly feasible, simple to operate, safe and effective. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test, according to the present invention.

[0033] Figure 2 This is a diagram showing the selection of points for the construction displacement and pressure stages during the step-down displacement test process after fracturing of the X1 layer in an embodiment of the present invention.

[0034] Figure 3 This is a graph showing the test results of the step-by-step emission reduction of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0037] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0038] To better understand the purpose, structure, and function of this invention, the following description, in conjunction with the accompanying drawings, provides a more detailed account of a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test.

[0039] Example 1

[0040] like Figure 1 As shown, the present invention provides a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test, comprising the following steps:

[0041] S1. After the first sand-carrying stage is completed, the temporary plugging construction of the first fracturing stage is started to test the change of bottom hole pressure during fracturing. In the step-down stage of fracturing construction, the bottom hole pressure and injection flow rate corresponding to the step-down point are selected to obtain the step-down test data.

[0042] S2. Import the reduced discharge test data into the fracturing simulation software to calculate the perforation friction pressure drop, near-wellbore bending friction pressure drop and total friction at the fracture inlet.

[0043] S3. By calculating the pressure drop of the perforation friction, determine the size and distribution of the erosion holes in the fracturing section;

[0044] S4. Based on the size and distribution of the erosion boreholes, calculate the particle size and dosage of the temporary plugging balls and temporary plugging particles.

[0045] S5. After the temporary plugging construction of this fracturing section is completed, repeat steps S1 to S4 to conduct a reduction in discharge rate test after the sand-carrying stage of the remaining fracturing sections.

[0046] Example 2

[0047] like Figure 1 As shown, the present invention provides a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test, comprising the following steps:

[0048] S1. After the first sand-carrying stage is completed, the temporary plugging construction of the first fracturing stage is started to test the change of bottom hole pressure during fracturing. In the step-down stage of fracturing construction, the bottom hole pressure and injection flow rate corresponding to the step-down point are selected to obtain the step-down test data.

[0049] S2. Import the reduced discharge test data into the fracturing simulation software to calculate the perforation friction pressure drop, near-wellbore bending friction pressure drop and total friction at the fracture inlet.

[0050] S3. By calculating the pressure drop of the perforation friction, determine the size and distribution of the erosion holes in the fracturing section;

[0051] S4. Based on the size and distribution of the erosion boreholes, calculate the particle size and dosage of the temporary plugging balls and temporary plugging particles.

[0052] S5. After the temporary plugging construction of this fracturing section is completed, repeat steps S1 to S4 to conduct a reduction in discharge rate test after the sand-carrying stage of the remaining fracturing sections.

[0053] The difference between this embodiment and Embodiment 1 is that:

[0054] In step S1, using a pressure gauge installed at the bottom of the fracturing string before construction, the change in bottom hole pressure during fracturing is tested. The test process involves injecting small amounts of construction fluid into the formation in a stepped manner with a predetermined flow rate, setting 3-5 short-duration steps. By rapidly reducing the flow rate, the net pressure within the fracture remains essentially constant. The flow rate at each step is reduced to 0.2-0.5 m³ / h. 3 The displacement is maintained at a rate of 1.0 m / min until it drops to zero, with the displacement of the last step kept as low as possible at 1.0 m / min. 3 / min or above;

[0055] In step S1, the injected construction fluid is any one of guar gum fracturing fluid, emulsion fracturing fluid, organic fracturing fluid, foam fracturing fluid, and synthetic polymer fracturing fluid;

[0056] Example 3

[0057] like Figure 1 As shown, the present invention provides a method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test, comprising the following steps:

[0058] S1. After the first sand-carrying stage is completed, the temporary plugging construction of the first fracturing stage is started to test the change of bottom hole pressure during fracturing. In the step-down stage of fracturing construction, the bottom hole pressure and injection flow rate corresponding to the step-down point are selected to obtain the step-down test data.

[0059] S2. Import the reduced discharge test data into the fracturing simulation software to calculate the perforation friction pressure drop, near-wellbore bending friction pressure drop and total friction at the fracture inlet.

[0060] S3. By calculating the pressure drop of the perforation friction, determine the size and distribution of the erosion holes in the fracturing section;

[0061] S4. Based on the size and distribution of the erosion boreholes, calculate the particle size and dosage of the temporary plugging balls and temporary plugging particles.

[0062] S5. After the temporary plugging construction of this fracturing section is completed, repeat steps S1 to S4 to conduct a reduction in discharge rate test after the sand-carrying stage of the remaining fracturing sections.

[0063] The difference between this embodiment and the above embodiments is that:

[0064] In step S2, the three-dimensional fracturing simulation software Meyer is used to calculate the perforation friction pressure drop, near-wellbore bending friction pressure drop, and total fracture inlet friction using the following classical formulas, such as... Figure 2 , Figure 3 As shown

[0065] The voltage drop Δp due to frictional resistance at the orifice pref The calculation formula is as follows:

[0066] Δp pref =k pref Q 2

[0067] Where Q is the construction displacement, m 3 / min,k pref The coefficient of friction of the pores;

[0068]

[0069] Where ρ is the density of the fracturing fluid, kg / m³ 3 C is the orifice flow coefficient, dimensionless (generally taken as 0.85); N is the number of orifices, dimensionless; D pref The diameter of the aperture.

[0070] Near-well bending friction pressure drop Δp nub The calculation formula is as follows:

[0071] Δp nub =k nub Q β

[0072] Where, k nub The value was obtained by fitting the step-down displacement test data; β is an empirical coefficient, dimensionless (generally taken as 0.5); the total frictional resistance at the crack inlet Δp entry The calculation formula is as follows:

[0073] Δp entry =Δp pref +Δpnub ;

[0074] Near-wellbore bending friction pressure drop is an indicator of the complexity of fracturing fractures in the vicinity of the wellbore. The higher the near-wellbore bending friction value, the higher the complexity of the fracturing fractures. The total friction at the fracture inlet mainly includes two parts: near-wellbore friction and wellbore friction. It is used to judge the difficulty of fracturing operations. The higher the total friction at the fracture inlet value, the more difficult the fracturing operations.

[0075] In step S3, the diameter and distribution of erosion boreholes within the section are determined by solving the pressure drop due to borehole friction in the calculation formula. Taking into account factors such as the flow resistance of the fracturing fluid and the erosion effect of the boreholes, and in combination with actual engineering requirements and geological conditions, the diameter of the erosion boreholes is calculated using the following formula:

[0076]

[0077] Where D is the diameter of the erosion hole (mm); Q is the construction discharge rate (m³). 3 / min; ρ is the density of the fracturing fluid, kg / m³ 3 ;ΔP pref Let be the pressure drop due to orifice friction, MPa; C be the orifice flow coefficient, dimensionless. The above method can effectively utilize the results of small-pressure tests to predict the orifice size and distribution of erosion blast holes within a section, thereby improving the efficiency and effectiveness of fracturing operations. In practical applications, experimental and numerical simulation methods can also be combined to study the orifice size and distribution of erosion blast holes within a section under different orifice friction pressure drops.

[0078] In step S4, based on the calculation results of the perforation hole diameter, the optimal particle size and dosage of the temporary plugging knot and the temporary plugging ball are selected. The diameter of the temporary plugging ball is 1.05 to 1.5 times the diameter of the perforation hole.

[0079] It is important to note that in actual construction, temporary plugging balls of different diameters should be added in batches according to the calculation results and construction parameters, and the pumping rate should be adjusted to optimize the temporary plugging effect. These steps may also need to be adjusted in combination with specific geological conditions, fracturing design and construction parameters. In practical applications, factors such as the type of temporary plugging agent, temperature resistance, degradability and pressure bearing capacity also need to be considered.

[0080] In step S4, the optimal particle size and dosage of the temporary plugging balls were determined based on the size and distribution of the erosion holes, which improved the success rate of temporary plugging and diverting fracturing.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Where there is no contradiction, the embodiments can be combined with each other to form new embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A method for guiding fracturing and temporary plugging operations using a stepped reduction displacement test, characterized in that, Includes the following steps: S1. After the first sand-carrying stage is completed, the temporary plugging construction of the first fracturing and stimulation section is started to test the change of bottom hole pressure during fracturing. In the step-down stage of fracturing construction, the bottom hole pressure and injection flow rate corresponding to the step-down point are selected to obtain the step-down test data. S2. Import the reduced discharge test data into the fracturing simulation software to calculate the perforation friction pressure drop, near-wellbore bending friction pressure drop and total friction at the fracture inlet. S3. By calculating the pressure drop of the perforation friction, determine the size and distribution of the erosion holes in the fracturing section; S4. Based on the size and distribution of the erosion boreholes, calculate the particle size and dosage of the temporary plugging balls and temporary plugging particles. S5. After the temporary plugging construction of this fracturing section is completed, repeat steps S1 to S4 to conduct a reduction in discharge rate test after the sand-carrying stage of the remaining fracturing sections.

2. The method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test according to claim 1, characterized in that, In step S1, the fracturing process is tested by injecting a set amount of construction fluid into the formation in a step-decreasing manner with a set displacement. 3-5 time steps are set, and the net pressure in the fracture is kept constant by reducing the displacement at a preset rate.

3. The method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test according to claim 2, characterized in that, In step S1, the displacement of each step is reduced to 0.2-0.5m. 3 / min, until the displacement drops to zero, with the displacement of the last step maintained at 1.0m. 3 / min or above.

4. The method for guiding fracturing and temporary plugging operations using a stepped discharge rate test according to any one of claims 1 to 3, characterized in that, In step S1, the injected construction fluid is any one of guar gum fracturing fluid, emulsion fracturing fluid, organic fracturing fluid, foam fracturing fluid, and synthetic polymer fracturing fluid.

5. The method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test according to claim 1, characterized in that, In step S2, the voltage drop Δp due to the frictional resistance of the aperture is... pref The calculation formula is as follows: Δp pref =k pref Q 2 Where Q is the construction displacement, m 3 / min,k pref The coefficient of friction of the pores; in, Where ρ is the density of the fracturing fluid, kg / m³ 3 C is the orifice flow coefficient, dimensionless, with a value of 0.85; N is the number of orifices, dimensionless; D pref The diameter of the aperture.

6. The method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test according to claim 5, characterized in that, In step S2, the near-wellbore bending friction Δp nub The calculation formula is as follows: Δp nub =k nub Q β Where, k nub The value was obtained by fitting the test data of step-by-step emission reduction; β is an empirical coefficient, dimensionless, and has a value of 0.

5.

7. The method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test according to claim 6, characterized in that, In step S2, the total frictional resistance Δp at the crack inlet entry The calculation formula is as follows: Δp entry =Δp pref +Δp nub 。 8. The method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test according to claim 1, characterized in that, In step S3, the diameter D of the erosion hole is calculated using the following formula: Where D is the diameter of the erosion hole, mm; Q is the construction discharge rate, m³. 3 / min; ρ is the density of the fracturing fluid, kg / m³ 3 ;ΔP pref ρ is the pressure drop due to orifice friction, MPa; C is the orifice flow coefficient, dimensionless.

9. The method for guiding fracturing and temporary plugging operations using a stepped reduction in discharge rate test according to claim 1, characterized in that, In step S4, based on the calculation results of the perforation hole diameter, the optimal particle size and amount of the temporary plugging knot and the temporary plugging ball are selected. The diameter of the temporary plugging ball is 1.05 to 1.5 times the diameter of the perforation hole.

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