Method for measuring and calculating reservoir transformation fracture wave and range

Abstract

The invention discloses a method for measuring and calculating a reservoir transformation fracture sweep range, and belongs to the technical field of petroleum fracturing. According to the method disclosed by the invention, the dissipated energy values of different lithologic reservoirs can be obtained through a coring physical model experiment, then the fracture wave and range of different lithologic single wells are measured and calculated in combination with actual fracturing construction curve conditions, the method is proved to have a prediction error of about 10% from developed practices, and the method has good measurement and calculation reliability and can be applied to the field of fracturing engineering. According to the method, monitoring equipment and condition requirements are not needed, application is not limited by the objective environment, and the new method for predicting the fracture wave and range in combination with the reservoir lithology and the actual working condition of fracturing construction has wide application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil fracturing, and particularly relates to a method for calculating the affected range of reservoir reconstruction fractures. Background Art

[0002] Hydraulic fracturing is currently the key measure to increase the production of various oil and gas reservoir formations. Evaluating and understanding the affected range of hydraulic fractures and guiding the optimization and upgrading of the technology are the key ways to further increase the affected range of fractures and improve the production of a single well. At present, the evaluation method of the affected range of hydraulic fractures mainly uses the field fracture monitoring technology. By monitoring measures such as stress fracture and liquid diffusion signals, the affected volume is calculated. The technology requires a lot of supporting equipment, and the implementation process is complex and the cost is high. Moreover, the field fracture monitoring technology has strict requirements on aspects such as the distance of the monitoring well and the laying environment of the ground equipment during the implementation process. Many wells cannot be monitored due to objective conditions not being met. Therefore, it is necessary to innovate a new method for predicting the affected range of fractures that does not require monitoring equipment and condition requirements, is not restricted by the objective environment, and combines the reservoir lithology and the actual working conditions of the fracturing construction. Summary of the Invention

[0003] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for calculating the affected range of reservoir reconstruction fractures, which is used to solve the technical problems existing in the existing evaluation method of the affected range of hydraulic fractures, such as complex implementation process, high cost, and restricted application by the objective environment.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] The present invention discloses a method for calculating the affected range of reservoir reconstruction fractures, including the following steps:

[0006] S1: Conduct a physical model experiment of hydraulic fracture on the reservoir core sample;

[0007] S2: After the physical model experiment of hydraulic fracture is completed, calculate the hydraulic fracture surface area of the reservoir core sample, and calculate the total work done by the pumping pressure;

[0008] S3: Obtain the energy dissipation value per unit area of fracture propagation according to the obtained hydraulic fracture surface area and the total work done by the pumping pressure of the reservoir core sample;

[0009] S4: According to the field fracturing curve, calculate the total work done by the actual construction pumping pressure, and combine the energy dissipation value per unit area of fracture propagation to infer the actual reservoir reconstruction fracture surface area.

[0010] Further, in S1, the physical model experiment of hydraulic fracture includes the following steps:

[0011] The same fracturing fluid system as that used in the mine fracturing construction was used. Combined with the range of single-well fracturing injection displacement in the mine, the injection displacement was converted to that of the indoor experiment based on the similarity criterion. Fracturing fluid injection and core fracture experiments were carried out, and the variation curves of injection pressure and injection time were recorded.

[0012] Furthermore, the liquid viscosity of the same fracturing fluid system in the mine fracturing construction ranges from 3 to 50 MPa·s.

[0013] Furthermore, the range of injection displacement of a single well in the mine is 2-8m 3 / min.

[0014] Furthermore, the range of the converted indoor experimental injection displacement is 5-20 ml / min.

[0015] Furthermore, in S2, the hydraulic fracture surface area of ​​the reservoir core sample is calculated by a 3D scanning method; the 3D scanning method is to place the fractured core in a full core CT three-dimensional scanner, and obtain the parameters of the hydraulic fracture surface area of ​​the cracks formed after the core is fractured through instrument scanning.

[0016] Furthermore, in S2, the total work done by the pumping pressure is calculated using a pumping curve method; the pumping curve method is based on the horizontal and vertical coordinate values ​​of the curve of the change of injection displacement, injection pressure and injection time in the hydraulic fracturing simulation experiment, and the value obtained by integrating and multiplying is the total work done by the pumping pressure.

[0017] Further, in S3, the crack expansion unit area dissipation energy value is calculated by the following calculation formula:

[0018]

[0019] Where: P is the pumping pressure, Q is the pumping displacement, and S is the hydraulic fracture surface area.

[0020] Furthermore, in S4, the total work done by the actual construction pumping pressure is calculated, and the actual reservoir transformation fracture surface area is estimated in combination with the dissipated energy per unit area of ​​the fracture expansion. The specific steps include:

[0021] Based on the horizontal and vertical coordinate values ​​of the variation curve of the actual fracturing construction displacement, injection pressure and injection time of a single well in the mine, the actual construction pumping pressure total work value is calculated by integral multiplication; then, based on the actual construction pumping pressure total work value and the dissipated energy value per unit area of ​​crack expansion, the actual reservoir transformation fracture surface area is obtained.

[0022] Furthermore, based on the total work done by the actual construction pumping pressure, divided by the dissipated energy per unit area of ​​fracture expansion, the actual reservoir transformation fracture surface area is obtained.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention discloses a method for calculating the fracture penetration range of reservoir stimulation. Through core physical simulation experiments, the dissipated energy values of reservoirs with different lithologies can be obtained. Then, in combination with the actual fracturing construction curve, the fracture penetration range of a single well with different lithologies is calculated. It has been proven by the practices carried out that the prediction error of this method is about 10%, with good calculation reliability. This method is a new method for predicting the fracture penetration range that does not require monitoring equipment and condition requirements, is not restricted by the objective environment for application, and combines the reservoir lithology and the actual working conditions of fracturing construction, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flowchart of the steps of the method for calculating the fracture penetration range of reservoir stimulation of the present invention;

[0026] Figure 2 is an external view of the reservoir core sample used in Example 1 of the present invention;

[0027] Figure 3 is the pumping curve of Example 1 of the present invention;

[0028] Figure 4 is a schematic diagram of the area parameter of the fracture formed after the core rupture in Example 1 of the present invention;

[0029] Figure 5 is a schematic diagram of the injection curve of Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order to enable those skilled in the art of the present technology to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the specification, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0032] As Figure 1 shown, the present invention discloses a method for calculating the fracture penetration range of reservoir stimulation, including the following steps:

[0033] First, select reservoir core samples to carry out physical simulation experiments on hydraulic fracturing; then use the 3D scanning method to calculate the area of the hydraulic fracture surface; then use the pump injection rate and injection pressure curve to calculate the total work done by the pump injection pressure through integral multiplication; then divide the total work done by the pump injection pressure by the fracture surface area to obtain the energy dissipation value per unit area of fracture propagation for this type of reservoir (the calculation formula is where P is the pump injection pressure, Q is the pump injection rate, and S is the area of the hydraulic fracture); finally, according to the field fracturing curve of the oilfield, calculate the total work done by the actual construction pump injection pressure, and combine the energy consumption per unit area to infer the actual fracture surface area of reservoir stimulation, that is, the fracture penetration range.

[0034] Preferably, in S1, the physical simulation experiment of hydraulic fracturing is based on real cores, adopts a fracturing fluid system with a liquid viscosity range of 3 - 50 mPa·s, which is the same as that in the field fracturing construction, and combines the single-well fracturing injection rate in the field of 2 - 8 m 3 / min. Based on the similarity criterion, it is converted into the indoor experiment injection rate of 5 - 20 ml / min, and the fracturing fluid injection and core fracturing experiments are carried out through the general operation process of the physical simulation experiment of hydraulic fracturing in the industry, and the change curve of the injection pressure with the injection time is recorded.

[0035] Preferably, in S2, the total work done by the pump injection pressure is calculated by using the pump injection curve method; the method is a value obtained by calculating through integral multiplication based on the experimental injection rate, the real-time injection pressure reflected by the ordinate on the pump injection curve, and the injection time reflected by the abscissa, which is the total work done by the pump injection pressure.

[0036] Preferably, in S4, calculate the total work done by the actual construction pumping pressure, and combine the energy dissipation value per unit area of crack propagation to estimate the actual reservoir stimulation crack surface area. The specific steps include: Based on the actual fracturing construction displacement of a single well in the field, the real-time injection pressure on the ordinate and the actual injection time on the abscissa of the actual fracturing construction curve, calculate the total work done by the actual construction pumping pressure through integration and multiplication. Then, based on this value, divide it by the energy dissipation value per unit area of crack propagation to obtain the hydraulic fracture area formed by actual fracturing.

[0037] Example 1

[0038] For a certain new type of reservoir in Basin A, use the method disclosed in the present invention to evaluate the hydraulic fracture propagation range. First, obtain the true core of this type of reservoir through well and layer selection, and process it to form dimensions that meet the requirements of indoor rock fracture experiments ( Figure 2 ); then refer to the 0.4% slickwater system used in actual field construction, based on the actual construction displacement of 4 - 6m 3 / min, convert the injection displacement in the indoor experiment to 8 ml / min based on the similarity criterion. Based on the above fracturing fluid system and injection parameters, use the industry-standard rock fracture physical model experiment process to carry out injection and fracture experiments, and record the pumping curve of the injection pressure changing with time ( Figure 3 ); after the fracture experiment, place the fractured core in a full-core CT three-dimensional scanner, and obtain the area parameter of the cracks formed after the core fracture through instrument scanning ( Figure 4 ); then obtain the total work done by the experimental pumping pressure by integrating and multiplying the three parameters of the experimental injection displacement, injection pressure, and injection time, and divide this value by the area parameter of the core fracture crack surface obtained by three-dimensional scanning to obtain the energy dissipation value per unit area of crack propagation for this type of lithologic reservoir as 0.083 J / mm 2 ; finally, combine the injection curve ( 3 ) of a certain actual fracturing single well in the field of this type of reservoir under the construction displacement parameter of 6m Figure 5 / min, use the displacement, pressure, and time to obtain the total work done by the actual injection pumping pressure through integration and multiplication, and divide it by the energy dissipation value per unit area of 0.083 J / mm 2 , that is, calculate and obtain the crack surface area that can be formed in the reservoir after the actual fracturing of this well in the field as 4.13×10 5 m 2 . According to the crack width of 2.46 mm, the crack volume after fracturing this well can be further obtained as 1016 m 3 .

[0039] The above content is only for explaining the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution in accordance with the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for measuring the affected range of fractures in reservoir stimulation, characterized in that The following steps are involved: S1: Conduct hydraulic fracturing simulation experiment on reservoir core samples; S2: After the hydraulic fracture simulation experiment is completed, the hydraulic fracture surface area of ​​the reservoir core sample is calculated, and the total work done by the pumping pressure is calculated; S3: Obtain the dissipated energy per unit area of ​​fracture expansion according to the hydraulic fracture surface area of ​​the reservoir core sample and the total work done by the pumping pressure; S4: According to the on-site fracturing curve of the mine, the total work done by the actual construction pumping pressure is calculated, and the actual reservoir transformation fracture surface area is estimated in combination with the dissipated energy per unit area of ​​the fracture expansion.

2. The method for measuring the fracture penetration range of reservoir stimulation according to claim 1, wherein In S1, the hydraulic fracturing model experiment includes the following steps: The same fracturing fluid system as that used in the mine fracturing construction was used. Combined with the range of single-well fracturing injection displacement in the mine, the injection displacement was converted to that of the indoor experiment based on the similarity criterion. Fracturing fluid injection and core fracture experiments were carried out, and the variation curves of injection pressure and injection time were recorded.

3. A method for calculating the fracture influence range of reservoir stimulation according to claim 2, wherein The liquid viscosity of the same fracturing fluid system in the mine fracturing construction ranges from 3 to 50 MPa·s.

4. A method for calculating the fracture influence range of reservoir stimulation according to claim 3, characterized in that The range of the fracturing injection displacement of a single well in the mine is 2 - 8 m 3 / min.

5. A method for measuring the fracture influence range of reservoir stimulation according to claim 4, characterized in that The range of the injection displacement converted into indoor experiments is 5-20 ml / min.

6. The method for measuring the fracture sweep area of reservoir stimulation according to claim 5, characterized in that, In S2, the hydraulic fracture surface area of ​​the reservoir core sample is calculated by a 3D scanning method; the 3D scanning method is to place the fractured core in a full core CT three-dimensional scanner, and obtain the parameters of the hydraulic fracture surface area of ​​the cracks formed after the core is fractured through instrument scanning.

7. The method for measuring the fracture influence range of reservoir stimulation according to claim 6, wherein In S2, the total work done by the pumping pressure is calculated using the pumping curve method; the pumping curve method is based on the horizontal and vertical coordinate values ​​of the curve of the change of injection displacement, injection pressure and injection time in the hydraulic fracturing model experiment, and the value obtained by integrating and multiplying is the total work done by the pumping pressure.

8. A method for measuring the affected range of fractures in reservoir stimulation according to claim 1, characterized in that In S3, the energy dissipated per unit area of ​​the crack expansion is calculated by the following calculation formula: Where: P is the pumping pressure, Q is the pumping displacement, and S is the hydraulic fracture surface area.

9. A method for measuring the fracture influence range of reservoir stimulation according to claim 1, characterized in that In S4, the total work done by the actual construction pumping pressure is calculated, and the actual reservoir transformation fracture surface area is estimated in combination with the dissipated energy per unit area of ​​the fracture expansion. The specific steps include: Based on the horizontal and vertical coordinate values ​​of the variation curve of the actual fracturing construction displacement, injection pressure and injection time of a single well in the mine, the actual construction pumping pressure total work value is calculated by integral multiplication; then, based on the actual construction pumping pressure total work value and the dissipated energy value per unit area of ​​crack expansion, the actual reservoir transformation fracture surface area is obtained.

10. A method for measuring the fracture influence range of reservoir stimulation according to claim 9, characterized in that, Based on the total work done by the actual construction pumping pressure, divided by the dissipated energy per unit area of ​​fracture expansion, the actual reservoir transformation fracture surface area is obtained.

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