Shale gas hydraulic fracturing real-time anomaly judgment method based on dynamic reference points

Abstract

The invention provides a shale gas hydraulic fracturing real-time anomaly judgment method based on a dynamic reference point, which comprises the following steps: according to real-time data, in combination with static pressure of sand-carrying fluid in a shaft, flowing friction resistance of fracturing fluid in the shaft and flowing friction resistance of fracturing fluid passing through a perforation hole, calculating net pressure of a shaft bottom at each moment; smoothing the well bottom net pressure array; selecting well bottom net pressure data at a plurality of moments from the well bottom net pressure array after smoothing processing, and taking the moment corresponding to the maximum value of the net pressure fitting relative error as a dynamic reference point; and taking the bottom net pressure derivative and the maximum pressure as indexes, and combining the net pressure index average value of the dynamic reference point to carry out abnormal comprehensive judgment. According to the invention, the abnormity can be carefully and timely captured.

Description

Technical Field

[0001] The invention belongs to the field of shale gas development, and in particular relates to a real-time abnormality determination method for shale gas hydraulic fracturing based on dynamic reference points. Background Art

[0002] Affected by the complexity of ground stress, the degree of natural fracture development, construction parameters, etc., the construction of hydraulic fracturing in shale gas horizontal wells is relatively complicated. Microseismic and other technologies can monitor the formation process of the fracture network. Due to the high cost, relevant monitoring is only carried out in some typical wells. In addition, due to the complex geographical and reservoir conditions of shale gas blocks, the accuracy and timeliness of its evaluation are difficult to guide on-site construction in a timely manner. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a real-time abnormality determination method for shale gas hydraulic fracturing based on dynamic reference points, which can improve the accuracy of determination.

[0004] As a first aspect of the present invention, the technical solution adopted by the present invention to solve the above technical problems is: a real-time abnormality determination method for shale gas hydraulic fracturing based on dynamic reference points, comprising: Read real-time data; Based on real-time data, the net bottom hole pressure at each moment is calculated by combining the static pressure of the sand-carrying fluid in the wellbore, the friction resistance of the fracturing fluid flowing through the wellbore, and the friction resistance of the fracturing fluid flowing through the perforations; According to the bottom hole net pressure at each moment, a bottom hole net pressure array in time sequence is obtained; Smoothing the bottom hole net pressure array; For the bottom hole net pressure array after smoothing, select the bottom hole net pressure data at several moments, and take the moment corresponding to the maximum value of the relative error of the net pressure fitting as the dynamic reference point; The bottom hole net pressure derivative and the maximum pressure are used as indicators, combined with the average value of the net pressure index of the dynamic reference point, to make a comprehensive abnormality judgment.

[0005] According to the above method, the bottom hole net pressure array is smoothed, specifically, a time-weighted method is used for forward smoothing.

[0006] According to the above method, the selection of bottom hole net pressure data at several moments and the use of the moment corresponding to the maximum relative error of net pressure fitting as a dynamic reference point specifically include: Take the time points a certain time before the current time, up to the time points two times before the current time, as reference points to calculate the relative error of the net pressure fitting; The time corresponding to the maximum value of the calculated net pressure fitting relative error is taken as the dynamic reference point.

[0007] According to the above method, the comprehensive abnormality determination specifically includes: If the net pressure derivative at the current moment is greater than or equal to the first preset derivative, it is determined that the extension is blocked; If at the current moment, the average value of the net pressure index of the dynamic reference point is greater than or equal to the first preset net pressure index, the current bottom hole net pressure is less than or equal to the first preset bottom hole net pressure value, and the net pressure derivative at the current moment is greater than or equal to the second preset derivative, it is determined that the extension is blocked; If at the current moment, the average value of the net pressure index of the dynamic reference point is greater than or equal to the first preset net pressure index, and the current bottom hole net pressure is greater than the first preset bottom hole net pressure value, it is determined that the fracture network is extended; If at the current moment, the net pressure derivative is less than or equal to the second preset derivative, and the current bottom hole net pressure is greater than the first preset bottom hole net pressure value, it is determined that the fracture network is extended; If at the current moment, the average net pressure index of the dynamic reference point is less than or equal to the second preset net pressure index, and the current bottom hole net pressure is less than or equal to the second preset bottom hole net pressure value, rapid filtration is determined.

[0008] According to the above method, the first preset derivative is 5, and the second preset derivative is -5.

[0009] According to the above method, the first preset net pressure index is 0.3, and the second preset net pressure index is -0.6.

[0010] According to the above method, the first preset bottom hole net pressure value is 0.7 times the maximum bottom hole net pressure; the second preset bottom hole net pressure value is 0.5 times the maximum bottom hole net pressure.

[0011] According to the above method, the method further comprises: Draw and display the bottom hole net pressure curve and abnormal data in real time. As a second aspect of the present invention, the present invention further provides a shale gas hydraulic fracturing real-time abnormality determination system based on dynamic reference points, comprising: A data acquisition unit, used to read real-time data; The bottom hole net pressure calculation unit is used to calculate the bottom hole net pressure at each moment according to the real-time data, combined with the static pressure of the sand-carrying fluid in the wellbore, the friction resistance of the fracturing fluid flowing in the wellbore and the friction resistance of the fracturing fluid flowing through the perforated holes, and obtain the bottom hole net pressure array in time sequence according to the bottom hole net pressure at each moment; A smoothing processing unit, used for smoothing the bottom hole net pressure array; The dynamic reference point acquisition unit is used to select the bottom hole net pressure data at several moments from the bottom hole net pressure array after smoothing, and take the moment corresponding to the maximum value of the relative error of the net pressure fitting as the dynamic reference point; The abnormal comprehensive judgment unit is used to use the bottom hole net pressure derivative and the maximum pressure as indicators, combined with the average value of the net pressure index of the dynamic reference point, to perform an abnormal comprehensive judgment.

[0012] As a third aspect of the present invention, the present invention further provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method when executing the computer program.

[0013] The beneficial effects of the present invention are as follows: by smoothing the real-time data and calculating the dynamic reference point, the bottom hole net pressure index is obtained, and combined with the net pressure derivative, real-time abnormality judgment is achieved according to the established rules, so that the abnormality can be captured more carefully and timely. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a method flow chart of an embodiment of the present invention.

[0015] Figure 2 Schematic diagram of control points according to an embodiment of the present invention.

[0016] Figure 3 It is a rendering of an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] The present invention provides a real-time abnormality determination method for shale gas hydraulic fracturing based on dynamic reference points, such as Figure 1 As shown, the method comprises the following steps: S1. Read real-time data.

[0019] In this example, first prepare the data: minimum horizontal principal stress , shaft length L, shaft diameter D, shaft vertical depth Z, number of blastholes , blasthole diameter , fracturing fluid density , proppant density .

[0020] Then read the real-time data, including wellhead pressure , displacement q and sand ratio .

[0021] S2. Calculate the bottom hole net pressure at each moment based on real-time data, combined with the static pressure of the sand-carrying fluid in the wellbore, the friction resistance of the fracturing fluid flowing through the wellbore, and the friction resistance of the fracturing fluid flowing through the perforations; obtain a time-sequential array of bottom hole net pressures based on the bottom hole net pressures at each moment.

[0022] Static pressure of sand-carrying fluid in the wellbore :

[0023] In the formula The unit is Pa; It indicates the proppant ratio, i.e. sand ratio; represents the density of fracturing fluid, . represents the proppant density, ; g represents the acceleration due to gravity, ; Z represents the vertical depth of the wellbore, m.

[0024] Fracturing fluid wellbore flow friction :

[0025] In the formula The unit is MPa; is the wellbore diameter, m; q is the displacement, ; L is the wellbore length, m.

[0026] Flow friction of fracturing fluid through perforations :

[0027] In the formula The unit is MPa; is the number of blast holes; is the borehole diameter, mm; q is the displacement, .

[0028] Then calculate the net bottom hole pressure according to the following formula

[0029] Where, p represents the net bottom hole pressure, Pa; Indicates wellhead pressure, Pa; Indicates the static pressure of the sand-carrying fluid in the wellbore, Pa; It represents the friction resistance of fracturing fluid in wellbore, Pa; represents the flow friction of the fracturing fluid through the perforation holes, Pa; represents the minimum horizontal principal stress, Pa.

[0030] According to the bottom hole net pressure at each moment, we can get the bottom hole net pressure array in time sequence: The changing time series of bottom hole net pressure is .

[0031] S3, smoothing the bottom hole net pressure array. Due to the randomness of real-time data, it is necessary to smooth the real-time data to a certain extent. In this embodiment, a time-weighted method is used for forward smoothing.

[0032]

[0033] In the formula, is the net bottom hole pressure at the current moment; For the current moment, For the previous moment, is the previous two moments (i.e. the moment before the previous moment); for Net bottom hole pressure at any moment; for Net bottom hole pressure at all times.

[0034] S4. For the bottom hole net pressure array after smoothing, select the bottom hole net pressure data at several moments, and use the moment corresponding to the maximum relative error of net pressure fitting as the dynamic reference point. Specifically, it includes: using the moment points a certain time before the current moment, up to the moment points 2 times before the current moment, as reference points, and calculating the relative error of net pressure fitting; using the moment corresponding to the maximum relative error of net pressure fitting calculated as the dynamic reference point.

[0035] In this embodiment, the current real-time point is i, and the point a certain time (2 minutes in this embodiment) ahead is k. The average value of the net pressure index is calculated by taking i-2 to k as reference points. and relative error of net pressure fitting , find the maximum relative error of the net pressure fitting .

[0036] The fitting value of the net bottom hole pressure index at the i-th point for:

[0037] Where j is the reference point, and the corresponding bottom hole net pressure index fitting values ​​can be calculated by substituting i-2 to k respectively.

[0038] Net stress index average for:

[0039]

[0040] Pick The reference point n is a dynamic reference point, then: .

[0041] S5. Taking the bottom hole net pressure derivative and the maximum pressure as indicators and combining the average value of the net pressure index of the dynamic reference point, a comprehensive abnormality determination is performed, specifically including: If the net pressure derivative at the current moment is greater than or equal to the first preset derivative, it is determined that the extension is blocked; If at the current moment, the average value of the net pressure index of the dynamic reference point is greater than or equal to the first preset net pressure index, the current bottom hole net pressure is less than or equal to the first preset bottom hole net pressure value, and the net pressure derivative at the current moment is greater than or equal to the second preset derivative, it is determined that the extension is blocked; If at the current moment, the average value of the net pressure index of the dynamic reference point is greater than or equal to the first preset net pressure index, and the current bottom hole net pressure is greater than the first preset bottom hole net pressure value, it is determined that the fracture network is extended; If at the current moment, the net pressure derivative is less than or equal to the second preset derivative, and the current bottom hole net pressure is greater than the first preset bottom hole net pressure value, it is determined that the fracture network is extended; If at the current moment, the average net pressure index of the dynamic reference point is less than or equal to the second preset net pressure index, and the current bottom hole net pressure is less than or equal to the second preset bottom hole net pressure value, rapid filtration is determined.

[0042] In this embodiment, the first preset derivative is 5, and the second preset derivative is -5; the first preset net pressure index is 0.3, and the second preset net pressure index is -0.6; the first preset bottom hole net pressure value is 0.7 times the maximum bottom hole net pressure; the second preset bottom hole net pressure value is 0.5 times the maximum bottom hole net pressure.

[0043] Where, the net pressure derivative :

[0044] As the fracturing process progresses, the maximum net bottom hole pressure is obtained in real time , used for rapid filtration loss determination.

[0045] The judgment rule is expressed in the following formula:

[0046] S5. Draw and display the bottom hole net pressure curve and abnormal data in real time. Figure 2 and Figure 3 As shown, a large amount of data smoothing is required to obtain more reasonable control points. Through the method of the present invention, dynamic reference points are used to capture anomalies more carefully.

[0047] As a second aspect of the present invention, the present invention further provides a shale gas hydraulic fracturing real-time abnormality determination system based on dynamic reference points, comprising: The data acquisition unit is used to read real-time data. The specific reading process has been described in detail in the above method, so it will not be repeated here.

[0048] The bottom hole net pressure calculation unit is used to calculate the bottom hole net pressure at each moment according to the real-time data, combined with the static pressure of the sand-carrying fluid in the wellbore, the friction resistance of the fracturing fluid in the wellbore and the friction resistance of the fracturing fluid flowing through the perforated holes, and obtain a bottom hole net pressure array in time sequence according to the bottom hole net pressure at each moment. The specific calculation process has been detailed in the above method, so it will not be repeated here.

[0049] The smoothing processing unit is used to smooth the bottom hole net pressure array; the specific processing process has been described in detail in the above method, so it will not be repeated here.

[0050] The dynamic reference point acquisition unit is used to select the bottom hole net pressure data at several moments from the smoothed bottom hole net pressure array, and take the moment corresponding to the maximum value of the net pressure fitting relative error as the dynamic reference point; the specific acquisition process has been detailed in the above method, so it will not be repeated here.

[0051] The abnormal comprehensive judgment unit is used to use the bottom hole net pressure derivative and the maximum pressure as indicators, combined with the average value of the net pressure index of the dynamic reference point, to perform an abnormal comprehensive judgment. The specific judgment process has been detailed in the above method, so it will not be repeated here.

[0052] As a third aspect of the present invention, the present invention further provides a computer device, such as a smart phone, tablet computer, laptop computer, desktop computer, rack server, blade server, tower server or cabinet server (including an independent server, or a server cluster composed of multiple servers) that can execute programs. The computer device of this embodiment includes at least but is not limited to: a memory that can be interconnected through a system bus, a processor, and a computer program stored in the memory and can be run on the processor, and the processor implements the steps of the method when executing the computer program.

[0053] The present invention focuses on the demand for real-time abnormality judgment of fracturing. Based on the bottom hole net pressure index and the net pressure fitting relative error model, on the basis of establishing a real-time data smoothing method, the reference point is dynamically calculated for specific real-time data points, and then the bottom hole net pressure index is obtained. Combined with the net pressure derivative, real-time abnormality judgment is achieved according to the established rules; the real-time abnormality judgment method for shale gas horizontal wells based on dynamic reference points can capture abnormalities more carefully and timely.

[0054] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A real-time abnormality determination method for shale gas hydraulic fracturing based on dynamic reference points, characterized in that: include: Read real-time data; Based on real-time data, the net bottom hole pressure at each moment is calculated by combining the static pressure of the sand-carrying fluid in the wellbore, the friction resistance of the fracturing fluid flowing through the wellbore, and the friction resistance of the fracturing fluid flowing through the perforations; According to the bottom hole net pressure at each moment, a bottom hole net pressure array in time sequence is obtained; Smoothing the bottom hole net pressure array; For the bottom hole net pressure array after smoothing, select the bottom hole net pressure data at several moments, and take the moment corresponding to the maximum value of the relative error of the net pressure fitting as the dynamic reference point; The bottom hole net pressure derivative and the maximum pressure are used as indicators, combined with the average value of the net pressure index of the dynamic reference point, to make a comprehensive abnormality judgment.

2. The method for determining real-time abnormality of shale gas hydraulic fracturing based on dynamic reference points according to claim 1 is characterized in that: The smoothing of the bottom hole net pressure array is specifically performed by forward smoothing using a time-weighted method.

3. The method for determining real-time abnormality of shale gas hydraulic fracturing based on dynamic reference points according to claim 1, characterized in that: The method of selecting the bottom hole net pressure data at several moments and taking the moment corresponding to the maximum relative error of the net pressure fitting as the dynamic reference point specifically includes: Take the time points a certain length of time before the current time, and the time points two times before the current time, as reference points to calculate the relative error of the net pressure fitting; The time corresponding to the maximum value of the calculated net pressure fitting relative error is taken as the dynamic reference point.

4. The method for real-time abnormality determination of shale gas hydraulic fracturing based on dynamic reference points according to claim 1 is characterized in that: The comprehensive abnormality determination specifically includes: If the net pressure derivative at the current moment is greater than or equal to the first preset derivative, it is determined that the extension is blocked; If at the current moment, the average value of the net pressure index of the dynamic reference point is greater than or equal to the first preset net pressure index, the current bottom hole net pressure is less than or equal to the first preset bottom hole net pressure value, and the net pressure derivative at the current moment is greater than or equal to the second preset derivative, it is determined that the extension is blocked; If at the current moment, the average value of the net pressure index of the dynamic reference point is greater than or equal to the first preset net pressure index, and the current bottom hole net pressure is greater than the first preset bottom hole net pressure value, it is determined that the fracture network is extended; If at the current moment, the net pressure derivative is less than or equal to the second preset derivative, and the current bottom hole net pressure is greater than the first preset bottom hole net pressure value, it is determined that the fracture network is extended; If at the current moment, the average net pressure index of the dynamic reference point is less than or equal to the second preset net pressure index, and the current bottom hole net pressure is less than or equal to the second preset bottom hole net pressure value, rapid filtration is determined.

5. The method for determining real-time abnormality of shale gas hydraulic fracturing based on dynamic reference points according to claim 4 is characterized in that: The first preset derivative is 5, and the second preset derivative is -5.

6. The method for determining real-time abnormality of shale gas hydraulic fracturing based on dynamic reference points according to claim 4 is characterized in that: The first preset net pressure index is 0.3, and the second preset net pressure index is -0.

6.

7. The method for determining real-time abnormality of shale gas hydraulic fracturing based on dynamic reference points according to claim 4 is characterized in that: The first preset bottom hole net pressure value is 0.7 times the maximum bottom hole net pressure; the second preset bottom hole net pressure value is 0.5 times the maximum bottom hole net pressure.

8. The method for real-time abnormality determination of shale gas hydraulic fracturing based on dynamic reference points according to claim 1, characterized in that: The method further comprises: Draw and display the bottom hole net pressure curve and abnormal data in real time.

9. A real-time abnormality determination system for shale gas hydraulic fracturing based on dynamic reference points, characterized in that: include: A data acquisition unit, used to read real-time data; The bottom hole net pressure calculation unit is used to calculate the bottom hole net pressure at each moment according to the real-time data, combined with the static pressure of the sand-carrying fluid in the wellbore, the friction resistance of the fracturing fluid flowing in the wellbore and the friction resistance of the fracturing fluid flowing through the perforated holes, and obtain the bottom hole net pressure array in time sequence according to the bottom hole net pressure at each moment; A smoothing processing unit, used for smoothing the bottom hole net pressure array; The dynamic reference point acquisition unit is used to select the bottom hole net pressure data at several moments from the bottom hole net pressure array after smoothing, and take the moment corresponding to the maximum value of the relative error of the net pressure fitting as the dynamic reference point; The abnormal comprehensive judgment unit is used to use the bottom hole net pressure derivative and the maximum pressure as indicators, combined with the average value of the net pressure index of the dynamic reference point, to perform an abnormal comprehensive judgment.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to one of claims 1 to 9 are implemented.

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