Fracturing effect evaluation method and system based on combination of flowback data and tracer test

Abstract

The invention belongs to the field of oil production engineering, and relates to a fracturing effect evaluation method based on combination of flowback data and tracer testing. And a tracer liquid production profile test is conducted in the flowback period of the target horizontal well, the effective transformation volume of the whole well fracture is obtained, the water production contribution rate and the underground liquid amount corresponding to the fractured sections of the target horizontal well are obtained, and the water production contribution rate can be used for representing the transformation effect of each fractured section. According to the effective transformation volume and the water production contribution rate of the whole well crack, the effective volume corresponding to the fracturing section of the target horizontal well is obtained, the effective volume is used for evaluating the fracturing effect, and the fracturing effect evaluation accuracy is improved. According to the effective volume and the underground liquid amount, whether the inter-segment crosstalk phenomenon occurs in the fracturing segment or not is judged. According to the method, whether the inter-section crosstalk phenomenon occurs in the fracturing section or not can be effectively judged, accurate characterization of the fracture volume of the whole horizontal well and each section can be achieved, the fracturing effect can be finely characterized, the fracture transformation effect can be quantified, and the fracture transformation volume can be accurately evaluated.

Description

Technical Field

[0001] The present invention belongs to the field of oil production engineering, and relates to a method and system for evaluating fracturing effect by combining flowback data with tracer testing. Background Art

[0002] The pore permeability of shale oil reservoirs is extremely low, and the development is difficult and costly. After long-term research at home and abroad, the main technology of horizontal well + multi-stage multi-cluster fracturing has been formed. The industry generally believes that the quality of the fracturing treatment directly affects the shale oil production. The better the fracturing treatment effect, the higher the production. Therefore, a fine evaluation of the fracturing treatment effect plays an important role in optimizing fracturing parameters and evaluating production capacity.

[0003] At present, the methods for evaluating fracturing effect are mainly divided into fracture monitoring methods and well testing methods. Fracture monitoring methods mainly include technologies such as optical fiber, microseismic, and tracer. Optical fiber temperature and acoustic wave monitoring are only limited to monitoring the fluid intake of near-well fractures, and it is difficult to quantify the fracture treatment effect. The microseismic technology has high cost and high noise, and can only accurately estimate the fracture azimuth, and the evaluation of the fracture treatment volume is inaccurate. The tracer monitoring technology can obtain the oil and water production conditions of each section of the fracture according to the flowback data. However, the common well testing models currently used are too simplified for fracture characterization, cannot reflect the complex fractures formed by shale oil and gas, and have strong multi-solution characteristics. Therefore, they cannot finely characterize the fracturing effect. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method and system for evaluating fracturing effect by combining flowback data with tracer testing. The present invention can accurately characterize the effective fracture volume of the entire horizontal well and each section, quantify the fracture treatment effect, and determine whether there is crossflow between sections.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention discloses a method for evaluating fracturing effect by combining flowback data with tracer testing, including the following steps:

[0007] Obtain the effective fracture volume of the entire well, and obtain the water production contribution rate and the amount of fluid injected into the formation corresponding to the fracturing section of the target horizontal well;

[0008] According to the effective fracture volume of the entire well and the water production contribution rate, obtain the effective fracture volume of the entire well of the target horizontal well;

[0009] According to the effective volume and the amount of fluid injected into the formation corresponding to the fracturing section of the target horizontal well, determine whether there is crossflow between sections in the fracturing section.

[0010] Furthermore, to obtain the water production contribution rate corresponding to the fracturing section of the target horizontal well, the specific method is as follows:

[0011] During the backflow period of the target horizontal well, a tracer liquid production profile test is carried out, and tracers of different types are placed in all the fractured sections at the target level;

[0012] Collect water samples from the target horizontal well during the backflow period multiple times in chronological order, and detect and interpret all tracers for each detected water sample;

[0013] When it is determined that the water production contribution rates of all tracers in the latest collected detected water sample reach a steady state, then according to the water production contribution rates of all tracers in the latest collected detected water sample, determine the water production contribution rate corresponding to each fractured section of the target horizontal well.

[0014] Furthermore, the effective fracture transformation volume of the whole well of the target horizontal well is obtained as follows:

[0015] Obtain the formation pressure data, bottom-hole flowing pressure data, water flow rate data and oil flow rate data of the target horizontal well after fracturing transformation, and obtain the double logarithmic curve of flow rate normalized pressure and material balance time based on the formation pressure data, bottom-hole flowing pressure data, water flow rate data and oil flow rate data;

[0016] Determine the data points included in the slope section that meets the preset slope condition in the double logarithmic curve, and fit to obtain the rectangular coordinate curve of flow rate normalized pressure and material balance time;

[0017] Obtain the effective fracture transformation volume of the whole well of the target horizontal well according to the slope of the rectangular coordinate curve.

[0018] Furthermore, the double logarithmic curve of flow rate normalized pressure and material balance time is obtained based on the formation pressure data, bottom-hole flowing pressure data, water flow rate data and oil flow rate data, and the formula is as follows:

[0019]

[0020]

[0021]

[0022]

[0023] where p i is the formation pressure after fracturing transformation, with the unit of MPa; p wf is the bottom-hole flowing pressure, with the unit of MPa; q w is the water-phase flow rate, q o is the oil-phase flow rate, with the unit of m 3 / d; t MD is the material balance time, with the unit of d; W p is the cumulative water production, N pis the cumulative water production, with the unit of m 3 .

[0024] Furthermore, the slope of the preset slope condition is 1.

[0025] Furthermore, according to the slope of the rectangular coordinate curve, the effective fracture treatment volume of the target horizontal well is obtained as follows:[[]]

[0026] Obtain the fracture closure pressure value, bottom-hole flowing pressure value, water volume coefficient, and compressibility of the target horizontal well;

[0027] According to the fracture closure pressure value and the bottom-hole flowing pressure value, obtain the net pressure value of the target horizontal well. The formula for obtaining the net pressure value of the target horizontal well is as follows:

[0028] p n = p c - p wf

[0029] where p n represents the net pressure, p c represents the closure pressure, p wf is the bottom-hole flowing pressure, with the unit of MPa;

[0030] Determine the fracture compressibility of the target horizontal well from the standard chart according to the net pressure value of the target horizontal well;

[0031] According to the fracture compressibility of the target horizontal well, the slope of the rectangular coordinate curve, the water volume coefficient, and the compressibility, calculate the effective fracture treatment volume of the whole well of the target horizontal well. The calculation formula is as follows:

[0032] C t = C f + C w

[0033]

[0034] where B w represents the water volume coefficient, C t is the comprehensive compressibility, with the unit of MPa -1 ; C f and C w are the rock compressibility and the water compressibility respectively.

[0035] Furthermore, the process of obtaining the fracture closure pressure value is as follows:

[0036] Conduct a mini-frac test on the target horizontal well or at least one adjacent well to obtain test data;

[0037] Analyze the test data using the G-function curve analysis method to obtain the fracture closure pressure value of the target horizontal well.

[0038] Further, the process of obtaining the bottom-hole flowing pressure data is as follows:

[0039] Obtain the wellhead pressure data of the target horizontal well during the flowback period;

[0040] Obtain the bottom-hole flowing pressure data of the target horizontal well based on the wellhead pressure data.

[0041] Further, determine whether there is crossflow between fracturing intervals according to the effective volume and the liquid volume injected into the ground, specifically as follows:

[0042] When the effective fracture volume of the whole well corresponding to a fracturing interval is greater than the corresponding liquid volume injected into the ground, it is determined that the fracturing interval is affected by crossflow between intervals.

[0043] Based on the above method, the present invention discloses a fracturing effect evaluation system combining flowback data and tracer testing, including a data acquisition module, a data processing module, and an inter-stage crossflow judgment module;

[0044] Data acquisition module: used to obtain the effective fracture volume of the whole well, the water production contribution rate and the liquid volume injected into the ground corresponding to the fracturing intervals of the target horizontal well;

[0045] Data processing module: used to obtain the effective fracture volume of the whole well of the target horizontal well according to the effective fracture volume of the whole well and the water production contribution rate;

[0046] Inter-stage crossflow judgment module: used to judge whether there is crossflow between fracturing intervals according to the effective volume and the liquid volume injected into the ground corresponding to the fracturing intervals of the target horizontal well.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The method of the present invention obtains the effective fracture volume of the whole well, the water production contribution rate and the liquid volume injected into the ground corresponding to the fracturing intervals of the target horizontal well. The water production contribution rate can be used to characterize the transformation effect of each fracturing interval. According to the effective fracture volume of the whole well and the water production contribution rate, the effective volume corresponding to the fracturing intervals of the target horizontal well is obtained. The effective volume is used to evaluate the fracturing effect and improve the accuracy of fracturing effect evaluation. According to the effective volume and the liquid volume injected into the ground, judge whether there is crossflow between fracturing intervals. The larger the effective fracture volume, the better the fracturing effect. If the effective fracture volume is greater than the liquid volume injected into the ground, crossflow between intervals has occurred. The present invention can effectively judge whether there is crossflow between fracturing intervals, can accurately characterize the fracture volume of the whole well and each interval of the horizontal well, can finely characterize the fracturing effect, can quantify the fracture transformation effect, and can accurately evaluate the fracture transformation volume.

[0049] The system of the present invention includes a data acquisition module, a data processing module, and an inter-stage crosstalk judgment module. The data acquisition module is used to obtain the effective fracture treatment volume of the entire well, and obtain the water production contribution rate and the amount of fluid injected into the ground corresponding to the fracturing stages of the target horizontal well. The data processing module: is used to obtain the effective fracture treatment volume of the entire well of the target horizontal well according to the effective fracture treatment volume of the entire well and the water production contribution rate. The inter-stage crosstalk judgment module: is used to judge whether there is an inter-stage crosstalk phenomenon in the fracturing stages according to the effective volume and the amount of fluid injected into the ground corresponding to the fracturing stages of the target horizontal well. Each module cooperates with each other, and can achieve accurate characterization of the fracture volume of the entire horizontal well and each stage, quantify the fracture treatment effect, and judge whether there is inter-stage crosstalk, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic flow chart of the method of the present invention;

[0051] Figure 2 is a backflow dynamic curve graph of an embodiment of the present invention;

[0052] Figure 3 is a double logarithmic curve graph of RNP-tMD of an embodiment of the present invention;

[0053] Figure 4 is a rectangular coordinate curve graph of RNP-tMD of an embodiment of the present invention;

[0054] Figure 5 is a classical graph of fracture compressibility coefficient of the present invention (Aguilera, 1999);

[0055] Figure 6 is the tracer water production contribution rate of an embodiment of the present invention;

[0056] Figure 7 is a graph of the calculated fracturing fluid efficiency, the amount of fluid injected into the ground, and the fracture volume of each stage of an embodiment of the present invention;

[0057] Figure 8 is a comparison of the fracture volumes of 3 and 4 clusters of an embodiment of the present invention;

[0058] Figure 9 is a system module diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to 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 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.

[0060] It should be noted that the terms "first", "second", etc. in the description, 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 the data used in this way 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.

[0061] The present invention will be further described in detail below with reference to the accompanying drawings:

[0062] See Figure 1 , the present invention discloses a method for evaluating fracturing effect by combining flowback data with tracer testing, comprising the following steps:

[0063] S1. Obtain the effective fracture treatment volume of the whole well, and obtain the water production contribution rate and the amount of fluid injected into the ground corresponding to the fracturing section of the target horizontal well;

[0064] The method for obtaining the water production contribution rate corresponding to the fracturing section of the target horizontal well is as follows:

[0065] During the flowback period of the target horizontal well, conduct a tracer liquid production profile test, and inject tracers of different types into all fracturing sections of the target horizontal well;

[0066] Collect water samples of the target horizontal well during the flowback period multiple times in chronological order, and detect and interpret all tracers for each detected water sample;

[0067] When it is determined that the water production contribution rates of all tracers in the latest collected detected water sample reach a steady state, then determine the water production contribution rate corresponding to each fracturing section of the target horizontal well according to the water production contribution rates of all tracers in the latest collected detected water sample.

[0068] S2. Obtain the effective fracture treatment volume of the whole well according to the effective fracture treatment volume of the whole well and the water production contribution rate;

[0069] The method for obtaining the effective fracture treatment volume of the whole well of the target horizontal well is as follows:

[0070] Obtain the formation pressure data, bottom-hole flowing pressure data, water flow rate data and oil flow rate data of the target horizontal well after fracturing treatment, and obtain a double logarithmic curve of flow rate normalized pressure and material balance time according to the formation pressure data, bottom-hole flowing pressure data, water flow rate data and oil flow rate data;

[0071] The process of obtaining bottom-hole flowing pressure data is as follows:

[0072] Obtain the wellhead pressure data of the target horizontal well during the flowback period;

[0073] Obtain the bottom-hole flowing pressure data of the target horizontal well according to the wellhead pressure data.

[0074] Determine the data points included in the slope segment that meets the preset slope condition in the double logarithmic curve, and fit to obtain the rectangular coordinate curve of flow rate-normalized pressure and material balance time;

[0075] Obtain the effective fracture stimulation volume of the whole well of the target horizontal well according to the slope of the rectangular coordinate curve, specifically as follows:

[0076] Obtain the fracture closure pressure value, bottom-hole flowing pressure value, volume coefficient and compressibility of water of the target horizontal well;

[0077] The process of obtaining the fracture closure pressure value is as follows:

[0078] Conduct a mini-frac test on the target horizontal well or at least one adjacent well to obtain test data;

[0079] Analyze the test data using the G-function curve analysis method to obtain the fracture closure pressure value of the target horizontal well.

[0080] Obtain the net pressure value of the target horizontal well according to the fracture closure pressure value and the bottom-hole flowing pressure value. The formula for obtaining the net pressure value of the target horizontal well is as follows:

[0081] p n = p c - p wf

[0082] Wherein, p n represents the net pressure, p c represents the closure pressure, p wf is the bottom-hole flowing pressure, and the unit is MPa.

[0083] Determine the fracture compressibility of the target horizontal well from the standard chart according to the net pressure value of the target horizontal well;

[0084] Calculate the effective fracture stimulation volume of the whole well of the target horizontal well according to the fracture compressibility of the target horizontal well, the slope of the rectangular coordinate curve, the volume coefficient and compressibility of water. The formula is as follows:

[0085] C t = C f + C w

[0086]

[0087] Among them, B w represents the volume coefficient of water, and C t is the comprehensive compressibility coefficient, with the unit of MPa -1 ; C f and C w are the compressibility coefficients of rock and water respectively.

[0088] Based on the formation pressure data, bottom-hole flowing pressure data, water flow rate data, and oil flow rate data, a double logarithmic curve of flow rate normalized pressure and material balance time is obtained, and the formula is as follows:

[0089]

[0090]

[0091]

[0092]

[0093] Among them, p i is the formation pressure after fracturing treatment, with the unit of MPa; p wf is the bottom-hole flowing pressure, with the unit of MPa; q w is the water-phase flow rate, q o is the oil-phase flow rate, with the unit of m 3 / d; t MD is the material balance time, with the unit of d; W p is the cumulative water production, N p is the cumulative water production, with the unit of m 3 .

[0094] The slope of the preset slope condition is 1.

[0095] S3. According to the effective volume and the amount of fluid injected into the ground, determine whether there is cross-interference between fracturing sections, specifically as follows:

[0096] When the effective fracture transformation volume of the whole well corresponding to a fracturing section is greater than the corresponding amount of fluid injected into the ground, it is determined that the fracturing section is affected by cross-interference between sections.

[0097] See Figure 1, in another feasible embodiment of the present invention, the following is adaptively modified according to the situation. Obtain the effective transformation volume of the fractures in the whole well, obtain the water production contribution rate and the amount of fluid injected into the ground corresponding to the fracturing sections of the target horizontal well. The water production contribution rate can be used to characterize the transformation effect of each fracturing section. According to the effective transformation volume of the fractures in the whole well and the water production contribution rate, obtain the effective volume corresponding to the fracturing sections of the target horizontal well. The effective volume is used to evaluate the fracturing effect and improve the accuracy of the fracturing effect evaluation. The effective transformation volume of the fractures in the whole well multiplied by the water production contribution rate is equal to the transformation volume of each fracturing section, which is used to characterize the transformation effect of each fracturing section. According to the effective volume and the amount of fluid injected into the ground, determine whether there is cross-interference between sections in the fracturing section. The larger the effective fracture volume, the better the fracturing effect. If the effective fracture volume is greater than the amount of fluid injected into the ground, cross-interference between sections has occurred. The present invention realizes the fine characterization of the fracturing effect by calculating the fracture volumes of the whole horizontal well and each section, and can effectively determine whether there is cross-interference between sections in the fracturing section.

[0098] Embodiment 1:

[0099] As Figure 1 shown, this embodiment discloses a method for evaluating the fracturing effect by combining flowback data and tracer testing, including:

[0100] Step S10, conduct tracer fluid production profile testing on the target horizontal well during the flowback period to obtain the water production contribution rate corresponding to each fracturing section of the target horizontal well.

[0101] In this embodiment, by conducting tracer fluid production profile testing on the target horizontal well during the flowback period, the water production contribution rate corresponding to each fracturing section of the target horizontal well can be obtained. The water production contribution rate can be used to characterize the transformation effect of each fracturing section.

[0102] Optionally, conducting tracer fluid production profile testing on the target horizontal well during the flowback period to obtain the water production contribution rate corresponding to each fracturing section of the target horizontal well includes: injecting tracers of different types into all the fracturing sections of the target horizontal well; collecting water samples of the target horizontal well during the flowback period multiple times in chronological order, and detecting and interpreting all the tracers in each detected water sample; when it is determined that the water production contribution rates of all the tracers in the latest collected detected water sample reach a stable state, then determine the water production contribution rate corresponding to each fracturing section of the target horizontal well according to the water production contribution rates of all the tracers in the latest collected detected water sample.

[0103] Among them, when conducting tracer production profile testing, different types of tracers are placed in all the fracturing sections of the target horizontal well. Detection water samples of the target horizontal well during the flowback period are collected in batches and multiple times in chronological order, and the water production contribution rates of all tracers are detected for each detection water sample. When the water production contribution rates of all tracers reach a stable state, the water production contribution rate corresponding to each fracturing section of the target horizontal well is determined. Selecting the water production contribution rates of all tracers when reaching the stable state can ensure that the calculated water production contribution rate corresponding to each fracturing section is relatively accurate, because the water production contribution rates of all the tracers measured from the water samples collected at the beginning are inaccurate.

[0104] Step S20: Obtain the effective volume corresponding to each fracturing section according to the total effective fracture transformation volume of the target horizontal well and the water production contribution rate corresponding to each fracturing section.

[0105] In this embodiment, through the total effective fracture transformation volume of the target horizontal well and the water production contribution rate corresponding to each fracturing section, the effective volume corresponding to each fracturing section can be obtained to evaluate the fracturing effect.

[0106] Optionally, according to the formation pressure data, bottom-hole flowing pressure data, and water flow rate data or oil flow rate data of the target horizontal well after fracturing transformation, obtain a double logarithmic curve of flow rate normalized pressure and material balance time; determine the data points included in the unit slope section of the double logarithmic curve, and fit to obtain a rectangular coordinate curve of flow rate normalized pressure and material balance time; calculate the total effective fracture transformation volume of the target horizontal well according to the slope of the rectangular coordinate curve.

[0107] Among them, through the formation pressure data, bottom-hole flowing pressure data, and water flow rate data or oil flow rate data of the target horizontal well after fracturing transformation, a double logarithmic curve of flow rate normalized pressure and material balance time is obtained. The data points included in the slope section that meets the preset slope condition in the double logarithmic curve are fitted, and a slope is obtained on the rectangular coordinate curve of flow rate normalized pressure and material balance time, and finally the total effective fracture transformation volume of the target horizontal well is calculated. This method can calculate the total effective fracture transformation volume of the target horizontal well more accurately.

[0108] Preferably, the slope of the preset slope condition of the double logarithmic curve is 1.

[0109] Among them, when fitting, select the data points with a slope of 1 in the double logarithmic curve of flow rate normalized pressure and material balance time. This part of the data points can accurately describe the phenomenon of fracturing fluid depletion in the fracture and the pressure disturbance reaching the fracture boundary.

[0110] Preferably, calculating the effective fracture treatment volume of the target horizontal well according to the slope of the rectangular coordinate curve includes: obtaining the net pressure value of the target horizontal well according to the fracture closure pressure value and the bottom-hole flowing pressure value of the target horizontal well; determining the fracture compressibility coefficient of the target horizontal well from the standard chart according to the net pressure value of the target horizontal well; calculating the effective fracture treatment volume of the whole well of the target horizontal well according to the fracture compressibility coefficient of the target horizontal well, the slope of the rectangular coordinate curve, and the measured volume coefficient and compressibility coefficient of water.

[0111] Among them, the net pressure value of the target horizontal well is obtained through the fracture closure pressure value and the bottom-hole flowing pressure value of the target horizontal well, the fracture compressibility coefficient of the target horizontal well is determined in the standard chart, and the effective fracture treatment volume of the whole well of the target horizontal well is calculated through the obtained fracture compressibility coefficient of the target horizontal well, the slope of the rectangular coordinate curve, and the measured volume coefficient and compressibility coefficient of water. The whole well fracture effect is measured by multiple data, and the calculation result is more accurate.

[0112] Preferably, the process of obtaining the fracture closure pressure value is as follows: conducting a mini-frac test on the target horizontal well to obtain the test data of the target horizontal well; analyzing the test data of the target horizontal well by using the G-function curve analysis method to obtain the fracture closure pressure value of the target horizontal well.

[0113] Among them, if a mini-frac test is carried out on the target horizontal well, the fracture closure pressure value is obtained by using the G-function curve analysis method, which is more accurate.

[0114] Preferably, obtaining the fracture closure pressure value of the target horizontal well according to the fracture closure pressure values of at least one adjacent well; wherein, the adjacent well is a horizontal well located in the same block as the target horizontal well.

[0115] That is, obtaining the fracture closure pressure value corresponding to the target horizontal well according to the fracture closure pressure values corresponding to at least one adjacent well located in the same block as the target horizontal well.

[0116] Among them, if a mini-frac test is not carried out on the target horizontal well, the fracture closure pressure value of the target horizontal well is converted according to the fracture closure pressure value obtained by analyzing the mini-frac test of the adjacent well in the same block, which can achieve lower construction costs on the premise of ensuring the accuracy of the fracture closure pressure value.

[0117] Preferably, the method of the present invention further includes: obtaining the wellhead pressure data of the target horizontal well during the flowback period; obtaining the bottom-hole flowing pressure data of the target horizontal well according to the wellhead pressure data of the target horizontal well.

[0118] Among them, the bottom-hole flowing pressure data of the target horizontal well is determined by converting the pressure value measured at the wellhead. Since it is easier to measure the pressure at the wellhead than at the bottom hole, the detection difficulty can be reduced.

[0119] Further, the method of the present invention further includes: evaluating the inflow performance of the target horizontal well during the flowback period according to the bottom-hole flowing pressure data of the target horizontal well and the water flow rate data or oil flow rate data.

[0120] Among them, after obtaining the bottom-hole flowing pressure data of the target horizontal well and the water flow rate data or oil flow rate data, the inflow performance of the target horizontal well during the flowback period can be evaluated, and the effect of the inflow performance of the target horizontal well can be judged more comprehensively.

[0121] Step S30: Judging whether there is cross-fracture interference between each fracturing stage according to the effective volume corresponding to each fracturing stage and the amount of fluid injected into the ground corresponding to each fracturing stage.

[0122] In this embodiment, by comparing the effective volume corresponding to each fracturing stage with the amount of fluid injected into the ground, it is judged whether there is cross-fracture interference between each fracturing stage.

[0123] Optionally, judging whether there is cross-fracture interference between each fracturing stage according to the effective volume corresponding to each fracturing stage and the amount of fluid injected into the ground corresponding to each fracturing stage includes: when the effective volume corresponding to a fracturing stage is greater than the amount of fluid injected into the ground corresponding to it, it is determined that cross-fracture interference occurs in the fracturing stage.

[0124] Among them, by comparing the effective volume corresponding to each fracturing stage with the amount of fluid injected into the ground, when the effective volume corresponding to a fracturing stage is greater than the amount of fluid injected into the ground corresponding to it, it is determined that cross-fracture interference occurs in the fracturing stage; when the effective volume corresponding to a fracturing stage is less than the amount of fluid injected into the ground corresponding to it, other means need to be combined to jointly judge whether cross-fracture interference occurs, and it is possible to accurately identify cross-fracture interference in this case.

[0125] As can be seen from the above embodiments, the present invention obtains the water production contribution rate corresponding to each fracturing stage of the target horizontal well according to the tracer production profile test of the target horizontal well during the flowback period; obtains the effective volume corresponding to each fracturing stage according to the total well fracture effective transformation volume of the target horizontal well and the water production contribution rate corresponding to each fracturing stage; judges whether there is cross-fracture interference between each fracturing stage according to the effective volume corresponding to each fracturing stage and the amount of fluid injected into the ground corresponding to each fracturing stage, and can realize the accurate characterization of the fracture volume of the whole well and each section of the horizontal well, and judge whether cross-fracture interference occurs.

[0126] Embodiment 2:

[0127] This embodiment provides a method for evaluating fracturing effect by combining flowback data with tracer testing, including the following steps:

[0128] Step 1: Collect fracturing construction data, collect the wellhead continuous pressure and oil / water flow rate data at the initial stage of backflow of the shale oil fracturing well, and conduct a backflow dynamic analysis of Well H1. For example, Figure 2 As shown, after fracturing Well H1 was shut in for 19 days, the wellbore was cleaned under pressure. After 35 days of flowback, the wellhead pressure dropped to 0. Subsequently, an ESP was lowered to increase the pressure difference. The water volume was stable between 35 and 80 days of flowback, and oil production gradually started after 80 days.

[0129] Step 2: Calculate RNP and t based on the collected pressure and flow rate data MD , and plot the double logarithmic graph of RNP and t MD to identify the fracture depletion stage, i.e., the unit slope stage. For example, Figure 3 as shown.

[0130] Step 3: Calculate the effective fracture treatment volume. First, plot the unit slope stage in a rectangular coordinate system. The functional relationship is: y = 0.0036x + 0.0104. Read the slope as 0.0036. For example, Figure 4 as shown. Then, calculate the fracture net pressure as 4.68 MPa according to the formula p n = p c - p wf . Among them, the fracture closure pressure of Well H1 was obtained by converting the results of the small-scale fracturing test of the adjacent well, which is 27.58 MPa. The wellhead pressure data was converted to the bottom-hole pressure data and then read the fracture compressibility as 0.013 from the Figure 5 shown chart. Finally, calculate the effective fracture volume as 20776.2 m 3 , accounting for 74% of the total injected fluid volume. The injected fluid volume is 26439.1 m 3 , and the treatment effect is good.

[0131] Step 4: Take samples of the backflow fluid in batches, analyze the water production contribution rate of each section of the tracer, see Figure 6 . During the stable stage, split the effective fracture volume according to the water production contribution rate of the tracer, calculate the effective volume of each section of the fracture, and evaluate the treatment effect of each section of the fracture. For example, Figure 7 as shown.

[0132] Example 3:

[0133] Based on Example 1, this method can also evaluate the crossflow phenomenon between fracturing sections.

[0134] Step 1: Collect the single-section injected fluid volume of all fracturing sections of Well H1.

[0135] Step 2: Plot the bar chart of the single-section injected fluid volume of Well H1 and the fracture volume of each section calculated in Example 1, and calculate the fracturing fluid efficiency. For example, Figure 7 as shown.

[0136] Step 3: Figure 7 In paragraphs 7, 8, 15, 17, and 19 of Figure 7 , the fracturing fluid efficiency is greater than 1, indicating possible crossflow between stages. After removing the abnormal stages, the average fracturing fluid efficiency is 51%.

[0137] Step 4: The cementing quality map of Well H1 shows poor cementing quality in stages 7 - 19, which may have caused crossflow between stages, basically consistent with the calculation results of this method.

[0138] Example 4

[0139] Based on Example 1, this method can also evaluate the fracturing stimulation effect under different cluster conditions within a stage.

[0140] Step 1: Well fracturing perforation parameters. Well H1 was fractured in a total of 19 stages, with 9 stages fractured with 3 clusters per stage and 10 stages fractured with 4 clusters per stage.

[0141] Step 2: According to the stage fracture stimulation volume calculated in Example 1, the average effective fracture volume is 1026 m 3 , and the average fracture stimulation volume is 1154 m 3 . The fracturing volume of 4 clusters per stage is slightly larger than that of 3 clusters per stage, as Figure 8 shown.

[0142] See Figure 9 , based on the above method, the present invention also discloses a fracturing effect evaluation system combining flowback data and tracer testing, including a data acquisition module, a data processing module, and an inter - stage crossflow judgment module;

[0143] Data acquisition module: used to obtain the effective stimulation volume of fractures in the whole well, and obtain the water production contribution rate and the amount of fluid entering the ground corresponding to the fractured stages of the target horizontal well;

[0144] Data processing module: used to obtain the effective stimulation volume of fractures in the whole well according to the effective stimulation volume of fractures in the whole well and the water production contribution rate;

[0145] Inter - stage crossflow judgment module: used to judge whether there is an inter - stage crossflow phenomenon in the fractured stages according to the effective volume and the amount of fluid entering the ground corresponding to the fractured stages of the target horizontal well.

[0146] In another feasible embodiment of the present invention, the following is adaptively modified according to the situation. It includes a data acquisition module, a data processing module, and an inter-stage crosstalk judgment module. The data acquisition module is used to acquire the effective fracture treatment volume of the entire well, and acquire the water production contribution rate and the amount of fluid injected into the ground corresponding to the fracturing stage of the target horizontal well. The data processing module is used to obtain the effective fracture treatment volume of the entire well of the target horizontal well according to the effective fracture treatment volume of the entire well and the water production contribution rate. The inter-stage crosstalk judgment module: is used to judge whether there is an inter-stage crosstalk phenomenon in the fracturing stage according to the effective volume and the amount of fluid injected into the ground corresponding to the fracturing stage of the target horizontal well. Each module cooperates with each other, and can achieve the accurate characterization of the fracture volume of the entire horizontal well and each stage, quantify the fracture treatment effect, and judge whether there is inter-stage crosstalk, etc.

[0147] The above content is only to illustrate 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 according to 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 evaluating the fracturing effect by combining flowback data with tracer testing, characterized in that, It includes the following steps: Obtain the effective fracture treatment volume of the whole well, and obtain the water production contribution rate and the amount of injected fluid corresponding to the fracturing sections of the target horizontal well; Based on the effective fracture treatment volume of the whole well and the water production contribution rate, obtain the effective fracture treatment volume of the whole well of the target horizontal well; Based on the effective volume and the amount of injected fluid corresponding to the fracturing sections of the target horizontal well, determine whether there is crossflow between sections in the fracturing sections.

2. The fracturing effect evaluation method combining flowback data and tracer test according to claim 1, wherein The specific method for obtaining the water production contribution rate corresponding to the fracturing sections of the target horizontal well is as follows: During the flowback period of the target horizontal well, conduct tracer fluid production profile tests, and inject tracers of different types into all the fracturing sections of the target horizontal well; Collect water samples of the target horizontal well during the flowback period multiple times in chronological order, and detect and interpret all tracers in each detected water sample; When it is determined that the water production contribution rates of all tracers in the latest collected detected water sample reach a steady state, then based on the water production contribution rates of all tracers in the latest collected detected water sample, determine the water production contribution rate corresponding to each fracturing section of the target horizontal well.

3. The fracturing effect evaluation method by combining flowback data with tracer testing according to claim 1, characterized in that The specific method for obtaining the effective fracture treatment volume of the whole well of the target horizontal well is as follows: Obtain the formation pressure data, bottom-hole flowing pressure data, water flow rate data, and oil flow rate data of the target horizontal well after fracturing treatment, and obtain the double logarithmic curve of flow rate normalized pressure and material balance time based on the formation pressure data, bottom-hole flowing pressure data, water flow rate data, and oil flow rate data; Determine the data points included in the slope section that meets the preset slope condition in the double logarithmic curve, and fit to obtain the rectangular coordinate curve of flow rate normalized pressure and material balance time; Based on the slope of the rectangular coordinate curve, obtain the effective fracture treatment volume of the whole well of the target horizontal well.

4. The fracturing effect evaluation method combining flowback data with tracer testing according to claim 3, characterized in that, The formula for obtaining the double logarithmic curve of flow rate normalized pressure and material balance time based on the formation pressure data, bottom-hole flowing pressure data, water flow rate data, and oil flow rate data is as follows: Among them, p i is the formation pressure after fracturing treatment, with the unit of MPa; p wf is the bottom-hole flowing pressure, with the unit of MPa; q w is the water-phase flow rate, q o is the oil-phase flow rate, with the unit of m 3 / d; t MD is the material balance time, with the unit of d; W p is the cumulative water production, N p is the cumulative water production, with the unit of m 3 .

5. The fracture effect evaluation method by combining flowback data with tracer test according to claim 3, characterized in that The slope of the preset slope condition is 1.

6. The fracture effect evaluation method by combining flowback data with tracer testing according to claim 3, characterized in that The specific method for obtaining the effective fracture treatment volume of the whole well of the target horizontal well based on the slope of the rectangular coordinate curve is as follows: Obtain the fracture closure pressure value, bottom-hole flowing pressure value, water volume coefficient, and compressibility of the target horizontal well; Based on the fracture closure pressure value and the bottom-hole flowing pressure value, obtain the net pressure value of the target horizontal well. The formula for obtaining the net pressure value of the target horizontal well is as follows: p n = p c -p wf where p n represents the net pressure, p c represents the shut-in pressure, p wf is the bottom-hole flowing pressure, with the unit of MPa; Based on the net pressure value of the target horizontal well, determine the fracture compressibility of the target horizontal well from the standard chart; Based on the fracture compressibility of the target horizontal well, the slope of the rectangular coordinate curve, the water volume coefficient, and the compressibility, calculate and obtain the effective fracture treatment volume of the whole well of the target horizontal well. The calculation formula is as follows: C t = C f + C w Among them, B w represents the volume coefficient of water, and C t is the comprehensive compressibility coefficient, with the unit of MPa -1 ; C f and C w are the rock compressibility coefficient and the water compressibility coefficient respectively.

7. The fracturing effect evaluation method combining flowback data with tracer testing according to claim 6, wherein The process for obtaining the fracture closure pressure value is as follows: Conduct a mini-frac test on the target horizontal well or at least one adjacent well to obtain test data; Use the G-function curve analysis method to analyze the test data to obtain the fracture closure pressure value of the target horizontal well.

8. The fracturing effect evaluation method combining flowback data with tracer testing according to claim 3, wherein, The process for obtaining the bottom-hole flowing pressure data is as follows: Obtain the wellhead pressure data of the target horizontal well during the flowback period; Based on the wellhead pressure data, obtain the bottom-hole flowing pressure data of the target horizontal well.

9. The fracturing effect evaluation method combining flowback data with tracer testing according to claim 1, characterized in that, The specific method for determining whether there is crossflow between sections in the fracturing sections based on the effective volume and the amount of injected fluid is as follows: When the effective fracture treatment volume of the whole well corresponding to a fracturing stage is greater than the corresponding fluid volume injected into the ground, it is determined that the fracturing stage is affected by cross-stage interference.

10. A fracturing effect evaluation system combining flowback data with tracer testing, characterized in that, It includes a data acquisition module, a data processing module, and an inter-stage interference judgment module; Data acquisition module: used to acquire the effective fracture treatment volume of the whole well, and acquire the water production contribution rate and the fluid volume injected into the ground corresponding to the fracturing stage of the target horizontal well; Data processing module: used to obtain the effective fracture treatment volume of the whole well of the target horizontal well according to the effective fracture treatment volume of the whole well and the water production contribution rate; Inter-stage interference judgment module: used to judge whether there is an inter-stage interference phenomenon in the fracturing stage according to the effective volume and the fluid volume injected into the ground corresponding to the fracturing stage of the target horizontal well.

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