Fracture complexity evaluation method based on fracturing water hammer effect

Abstract

The invention discloses a fracture complexity evaluation method based on a fracturing water hammer effect, and the method comprises the steps: 1, obtaining a water hammer pressure fluctuation curve corresponding to a target fracturing section according to the pumping pressure data corresponding to the target fracturing section in a fracturing construction process; 2, damping sine wave pressure response fitting after detrending is carried out on the water hammer pressure fluctuation curve corresponding to the target fracturing section obtained in the step 1, and a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section are obtained; and 3, according to the pressure wave fitting curve attenuation rate corresponding to the target fracturing section obtained in the step 2, determining the fracture network complexity of the target fracturing section. Evaluation data sources are wide, and data acquisition is convenient; meanwhile, the evaluation method is based on the pressure fluctuation response of the water hammer effect, and extra test cost is not needed.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production engineering, and in particular relates to a method for evaluating the complexity of cracks based on the fracturing water hammer effect. Background Art

[0002] With the increasing importance of the connection between the development of unconventional oil and gas reservoirs and conventional oil and gas reservoirs, the multi-stage fracturing technology of horizontal wells has been more and more widely used. The evaluation of complex fracture networks formed by multi-stage fracturing of horizontal wells has always been a hot topic in scientific research. Due to the lack of direct measurement methods for fracture morphology and parameters, the understanding of underground fracture networks is unclear.

[0003] At present, the main fracture network evaluation methods are concentrated in the following categories: direct on-site monitoring and evaluation based on mining conditions (microseismic monitoring, wide-area electromagnetic monitoring), indirect evaluation based on fracturing operation pressure data (curve fluctuation method, pressure transient well test method), indirect evaluation method based on numerical simulation of fracture extension, and indirect evaluation method based on production transient well test of post-fracturing production data, etc. However, the above fracture network evaluation methods all have corresponding shortcomings in terms of principle, cost, and evaluation complexity. Summary of the invention

[0004] The purpose of the present invention is to provide a method for evaluating the complexity of fractures based on the water hammer effect of fracturing, so as to solve the problems that the existing field-scale direct monitoring fracture network evaluation method has high cost and the indirect monitoring evaluation method has insufficient representativeness.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for evaluating the complexity of cracks based on the fracturing water hammer effect, which is specifically implemented according to the following steps:

[0006] Step 1, obtaining a water hammer pressure fluctuation curve corresponding to a target fracturing section according to pumping pressure data corresponding to the target fracturing section during the fracturing construction process;

[0007] Step 2, performing a detrended damped sine wave pressure response fitting on the water hammer pressure fluctuation curve corresponding to the target fracturing section obtained in step 1 to obtain a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section;

[0008] Step 3: Determine the complexity of the fracture network of the target fracturing section according to the attenuation rate of the pressure wave fitting curve corresponding to the target fracturing section obtained in step 2.

[0009] As a preferred technical solution of the present invention, in step 1, according to the pumping pressure data corresponding to the target fracturing section during the fracturing construction, obtaining the water hammer pressure fluctuation curve corresponding to the target fracturing section includes:

[0010] Obtaining water hammer effect pressure data corresponding to the target fracturing section from the pumping pressure data corresponding to the target fracturing section;

[0011] The water hammer pressure fluctuation curve corresponding to the target fracturing section is obtained according to the water hammer effect pressure data corresponding to the target fracturing section.

[0012] As a preferred technical solution of the present invention, in step 2, the water hammer pressure fluctuation curve corresponding to the target fracturing section is subjected to a detrended damped sine wave pressure response fitting, and obtaining the pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section at least includes:

[0013] performing detrending processing on the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain a detrended pressure fluctuation curve corresponding to the target fracturing section;

[0014] A damped sine wave pressure response fitting is performed on the detrended pressure fluctuation curve corresponding to the target fracturing section to obtain a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section.

[0015] As a preferred technical solution of the present invention, detrending the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain the detrended pressure fluctuation curve corresponding to the target fracturing section includes:

[0016] Performing binomial regression fitting on the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain a binomial fitting curve corresponding to the target fracturing section;

[0017] The detrended pressure fluctuation curve corresponding to the target fracturing section is obtained according to the water hammer pressure fluctuation curve corresponding to the target fracturing section and the binomial fitting curve.

[0018] As a preferred technical solution of the present invention, fitting the detrended pressure fluctuation curve corresponding to the target fracturing section to obtain the fitted pressure curve corresponding to the target fracturing section specifically includes:

[0019] The detrended pressure fluctuation curve corresponding to the target fracturing section is subjected to damped sine wave fitting using the least squares method to obtain a pressure wave fitting curve corresponding to the target fracturing section.

[0020] As a preferred technical solution of the present invention, the pressure wave fitting characteristic data is also used to characterize the maximum amplitude and period of the pressure wave fitting curve.

[0021] As a preferred technical solution of the present invention, determining the fracture network complexity of the target fracturing section according to the pressure wave fitting characteristic data corresponding to the target fracturing section includes: determining the fracture network complexity of the target fracturing section according to the attenuation rate in the pressure wave fitting characteristic data corresponding to the target fracturing section.

[0022] The beneficial effects of the present invention are as follows: a method for evaluating the complexity of cracks based on the water hammer effect of hydraulic fracturing is provided. According to the pumping pressure data corresponding to the target hydraulic fracturing section during the hydraulic fracturing construction, a water hammer pressure fluctuation curve corresponding to the target hydraulic fracturing section is obtained, and the fluctuation change relationship between the wellhead pressure and time after the pump is stopped during the hydraulic fracturing construction is characterized; the damped sine wave pressure response fitting after detrending the water hammer pressure fluctuation curve corresponding to the target hydraulic fracturing section is performed to obtain the pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target hydraulic fracturing section; according to the attenuation rate in the pressure wave fitting characteristic data corresponding to the target hydraulic fracturing section, the complexity of the crack network of the target hydraulic fracturing section is determined, which solves the problem that it is difficult to evaluate the complexity of the crack network economically and efficiently under the current hydraulic fracturing crack network conditions. At the same time, since the water hammer effect caused by the hydraulic fracturing pump stop can be seen as a pressure fluctuation response in each section, the evaluation data source of the present invention is wide and the data acquisition is convenient; at the same time, the evaluation method is based on the pressure fluctuation response of the water hammer effect, and no additional testing cost is required; in addition, the method of the present invention is simple to use, and the evaluation result is fast. At the same time, the evaluation of the complexity of the crack network formed by the single-stage hydraulic fracturing can be obtained and the difference comparison can be carried out at the end of the hydraulic fracturing construction, which provides a reliable research means for the evaluation of the complexity of the crack network. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram showing a process flow of a method for evaluating the complexity of cracks according to an embodiment of the present invention is shown;

[0024] Figure 2 A schematic diagram of a fracturing construction curve and a water hammer effect according to an embodiment is shown;

[0025] Figure 3 A schematic diagram of fracturing water hammer effect fitting according to an embodiment is shown. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings, tables and specific embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1

[0028] like Figures 1 to 3 As shown, this embodiment discloses a method for evaluating the complexity of fractures based on the fracturing water hammer effect, comprising:

[0029] Step 1: obtaining a water hammer pressure fluctuation curve corresponding to the target fracturing section according to the pumping pressure data corresponding to the target fracturing section during the fracturing construction process; wherein the water hammer pressure fluctuation curve is characterized by the fluctuation change relationship between the wellhead pressure and time after the pump is stopped during the fracturing construction.

[0030] At the moment of pump stop during fracturing construction, due to the inertia of the pressurized water flow, a water shock wave is generated. The force generated by the water shock wave will cause the corresponding pressure curve to fluctuate, which is the water hammer pressure fluctuation curve, which is reflected in the fluctuation relationship between the wellhead pressure and time after the pump is stopped during fracturing construction. Since the water hammer effect caused by the pump stop during hydraulic fracturing can be seen as a pressure fluctuation response in each section, the evaluation data obtained is widely sourced and easy to obtain. At the same time, the evaluation method is based on the pressure fluctuation response of the water hammer effect, and no additional testing cost is required.

[0031] The pumping pressure data is generally the second-by-second pressure data collected by the on-site fracturing truck at the wellhead in real time, and the collection method is simple and efficient. Step 2, the damped sine wave pressure response fitting is performed on the water hammer pressure fluctuation curve corresponding to the target fracturing section after detrending, and the pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section are obtained; wherein the pressure wave fitting characteristic data is at least used to characterize the attenuation rate of the pressure wave fitting curve.

[0032] The detrended pressure fluctuation curve of the target fracturing section is fitted with a damped sine wave pressure response to obtain a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section. The pressure wave fitting characteristic data is at least used to characterize the attenuation rate of the pressure wave fitting curve.

[0033] Step 3: Determine the fracture network complexity of the target fracturing section according to the attenuation rate in the pressure wave fitting characteristic parameter corresponding to the target fracturing section.

[0034] The complexity of the fracture network of the target fracturing section can be directly determined by the attenuation rate in the pressure wave fitting characteristic parameters corresponding to the target fracturing section. The evaluation result is fast, and the quantification of the complexity evaluation of the fracture network formed by a single-stage fracturing can be obtained at the end of the fracturing construction, and the difference comparison can be carried out.

[0035] Among them, the fracture network complexity of the target fracturing section is characterized by combining the pressure wave fitting characteristic data corresponding to the target fracturing section and the microseismic data. The accuracy of the determination of the fracture network complexity is higher through joint verification of the two types of data.

[0036] According to the pressure wave fitting characteristic data corresponding to the target fracturing section, the fracture network complexity of the target fracturing section is determined, including: according to the attenuation rate in the pressure wave fitting characteristic data corresponding to the target fracturing section, the fracture network complexity of the target fracturing section is determined, which solves the problem that it is difficult to evaluate the complexity of the fracture network economically and efficiently under the current fracture network conditions; wherein, the microseismic data can be used as additional data to prove the credibility of the fitting characteristic data in characterizing the fracture network complexity. Among them, the fracture network complexity of the target fracturing section is characterized by combining the pressure wave fitting characteristic data corresponding to the target fracturing section with the microseismic data, and the change trend of the attenuation rate of the effective section is consistent with the change trend of the transformation volume of the microseismic monitoring of the adjacent wells.

[0037] It can be seen from the above embodiments that the present invention obtains a water hammer pressure fluctuation curve corresponding to the target fracturing section according to the pumping pressure data corresponding to the target fracturing section during the fracturing construction, which is used to characterize the fluctuation change relationship between the wellhead pressure and time after the pump is stopped during the fracturing construction; the water hammer pressure fluctuation curve corresponding to the target fracturing section is fitted with a damped sine wave pressure response to obtain a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section, which are at least used to characterize the attenuation rate of the pressure wave fitting curve; according to the pressure wave fitting characteristic data corresponding to the target fracturing section, the seam network complexity of the target fracturing section is determined, which solves the problem that it is difficult to economically and efficiently evaluate the seam network complexity under the current conditions of the fracturing seam network. At the same time, since the water hammer effect caused by the hydraulic fracturing pump stop can be seen as a pressure fluctuation response in each section, the evaluation data source of the present invention is wide and the data acquisition is convenient; at the same time, the evaluation method is based on the pressure fluctuation response of the water hammer effect, and no additional testing cost is required; in addition, the method of the present invention is simple to use and the evaluation result is fast. At the same time, the quantification of the complexity evaluation of the seam network formed by a single-stage fracturing can be obtained at the end of the fracturing construction and the difference comparison can be carried out, which provides a reliable research means for the evaluation of the seam network complexity.

[0038] Example 2

[0039] like Figure 2 As shown, different from Example 1, in Example 2, the present invention specifically defines that in step 1, according to the pumping pressure data corresponding to the target fracturing section during the fracturing construction process, obtaining the water hammer pressure fluctuation curve corresponding to the target fracturing section includes: obtaining the water hammer effect pressure data corresponding to the target fracturing section from the pumping pressure data corresponding to the target fracturing section; wherein the water hammer effect pressure data is characterized by the wellhead pressure value within the time period when the water hammer effect occurs; and obtaining the water hammer pressure fluctuation curve corresponding to the target fracturing section according to the water hammer effect pressure data corresponding to the target fracturing section.

[0040] Among them, the water hammer effect pressure data corresponding to the target fracturing section is screened out from the pumping pressure data corresponding to the target fracturing section, and the water hammer pressure fluctuation curve corresponding to the target fracturing section is obtained through the water hammer effect pressure data corresponding to the target fracturing section. The appropriate water hammer effect fluctuation duration is selected according to the drawing display results, and only the most critical part of the data is processed, which is conducive to improving data processing efficiency.

[0041] Example 3

[0042] Different from Example 2, in Example 3, the present invention specifically defines that in step 2, the damped sinusoidal wave pressure response fitting is performed on the detrended pressure fluctuation curve corresponding to the target fracturing section to obtain the pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section, including: detrending the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain the detrended pressure fluctuation curve corresponding to the target fracturing section; and damped sinusoidal wave pressure response fitting is performed on the trended pressure fluctuation curve corresponding to the target fracturing section to obtain the pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section.

[0043] Among them, by detrending the water hammer pressure fluctuation curve corresponding to the target fracturing section, the detrended pressure fluctuation curve corresponding to the target fracturing section is obtained, which can eliminate the influence of the offset generated by the data on the subsequent curve fitting.

[0044] There are many methods for detrending the water hammer pressure fluctuation curve corresponding to the target fracturing section, such as convex optimization method, wavelet decomposition method, smoothing prior method and binomial fitting method, etc. The specific detrending method used is not limited and can be selected according to actual conditions.

[0045] Detrending the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain the detrended pressure fluctuation curve corresponding to the target fracturing section includes: performing least squares binomial fitting on the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain the binomial fitting pressure curve corresponding to the target fracturing section; obtaining the detrended pressure fluctuation curve corresponding to the target fracturing section according to the water hammer pressure fluctuation curve corresponding to the target fracturing section and the binomial fitting pressure curve.

[0046] Among them, the least squares binomial fitting can more accurately characterize the trend change of the water hammer pressure fluctuation curve.

[0047] Example 4

[0048] like Figure 3As shown, different from Example 3, in Example 4, further, a damped sine wave fitting is performed on the de-trended pressure fluctuation curve corresponding to the target fracturing section to obtain the fitted pressure fluctuation curve corresponding to the target fracturing section, including: using the least squares method to perform a damped sine wave fitting on the de-trended pressure fluctuation curve corresponding to the target fracturing section to obtain the fitted pressure fluctuation curve corresponding to the target fracturing section.

[0049] Among them, the damped sine wave fitting of the detrended pressure fluctuation curve corresponding to the target fracturing section is performed by using the least squares method to obtain the fitted pressure fluctuation curve corresponding to the target fracturing section. The least squares method can be used to easily fit the data and minimize the sum of squares of the errors between the fitted data and the actual data. Among them, the pressure wave fitting characteristic data is not only used to characterize the attenuation rate of the pressure wave fitting curve, but also can be used to characterize the maximum amplitude and period of the pressure wave fitting curve.

Claims

1. Fracture complexity evaluation method based on fracturing water hammer effect, It is characterized in that Follow the steps below to implement it: Step 1, obtaining a water hammer pressure fluctuation curve corresponding to a target fracturing section according to pumping pressure data corresponding to the target fracturing section during the fracturing construction process; Step 2, performing a detrended damped sine wave pressure response fitting on the water hammer pressure fluctuation curve corresponding to the target fracturing section obtained in step 1 to obtain a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section; Step 3: Determine the complexity of the fracture network of the target fracturing section according to the attenuation rate of the pressure wave fitting curve corresponding to the target fracturing section obtained in step 2.

2. According to the method for evaluating the complexity of fractures based on the water hammer effect of fracturing according to claim 1, It is characterized in that In the step 1, according to the pumping pressure data corresponding to the target fracturing section during the fracturing construction process, obtaining the water hammer pressure fluctuation curve corresponding to the target fracturing section includes: Obtaining water hammer effect pressure data corresponding to the target fracturing section from the pumping pressure data corresponding to the target fracturing section; The water hammer pressure fluctuation curve corresponding to the target fracturing section is obtained according to the water hammer effect pressure data corresponding to the target fracturing section.

3. The method for evaluating the complexity of cracks based on the water hammer effect of fracturing according to claim 2, It is characterized in that In step 2, performing a detrended damped sine wave pressure response fitting on the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section includes at least: Performing detrending processing on the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain a detrended pressure fluctuation curve corresponding to the target fracturing section; A damped sine wave pressure response fitting is performed on the detrended pressure fluctuation curve corresponding to the target fracturing section to obtain a pressure wave fitting curve and pressure wave fitting characteristic data corresponding to the target fracturing section.

4. The method for evaluating the complexity of cracks based on the water hammer effect of fracturing according to claim 3, It is characterized in that Performing detrending processing on the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain the detrended pressure fluctuation curve corresponding to the target fracturing section includes: Performing binomial regression fitting on the water hammer pressure fluctuation curve corresponding to the target fracturing section to obtain a binomial fitting curve corresponding to the target fracturing section; The detrended pressure fluctuation curve corresponding to the target fracturing section is obtained according to the water hammer pressure fluctuation curve corresponding to the target fracturing section and the binomial fitting curve.

5. According to the method for evaluating the complexity of fractures based on the water hammer effect of fracturing according to claim 4, It is characterized in that The detrended pressure fluctuation curve corresponding to the target fracturing section is fitted to obtain the fitted pressure curve corresponding to the target fracturing section, specifically including: The detrended pressure fluctuation curve corresponding to the target fracturing section is subjected to damped sine wave fitting using the least squares method to obtain a pressure wave fitting curve corresponding to the target fracturing section.

6. According to the method for evaluating the complexity of fractures based on the water hammer effect of fracturing according to claim 5, It is characterized in that The pressure wave fitting characteristic data is also used to characterize the maximum amplitude and period of the pressure wave fitting curve.

7. The method for evaluating the complexity of fractures based on the water hammer effect of fracturing according to claim 6, It is characterized in that Determining the fracture network complexity of the target fracturing section according to the pressure wave fitting characteristic data corresponding to the target fracturing section includes: determining the fracture network complexity of the target fracturing section according to an attenuation rate in the pressure wave fitting characteristic data corresponding to the target fracturing section.

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