Method for monitoring extension effectiveness and fracture form of multi-cluster fractures of horizontal well

Abstract

The invention discloses a horizontal well multi-cluster fracture extension effectiveness and fracture form monitoring method, which comprises the following steps: S1, selecting a monitoring well, installing a high-precision pressure gauge, and cementing the well; s2, the monitoring well is filled with filling liquid, and the sealing performance is tested; s3, first-section fracturing operation is carried out, data are collected, and a variable relation is established to serve as a standard; s4, second-section fracturing operation is carried out, obtained data are compared with the standard, the position of a deformed cement sheath is analyzed, and the number and form of perforation clusters are determined; s5, the step S4 is repeated, fracturing operation of the third section to the N / 2 section is carried out, and rules are summarized to optimize the process; and S6, referring to the optimization process, repeating the step S4, carrying out N / 2-N section fracturing operation, and determining the optimal fracturing process and expansion form of the block. According to the horizontal well multi-cluster fracture extension effectiveness evaluation method, the problems that in the prior art, a special device needs to be installed, the influence of the accuracy of a mathematical model is caused, anisotropism interferes with reservoir rock acoustic mechanics induction, and the monitoring result is uncertain are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic fracturing in oil and gas fields, and relates to a method for monitoring the effectiveness of extension of multiple clusters of fractures in horizontal wells and the fracture morphology. Background Art

[0002] In order to achieve the effective development of tight oil and gas and shale oil and gas and other unconventional oil and gas with ultra-low porosity and ultra-low permeability, the horizontal well segmented multi-cluster fracturing technology has been formed based on the technical concept of increasing the complexity of fractures to improve the fluidity of oil and gas. At present, the horizontal well segmented fracturing technology is becoming more and more common, with a horizontal section length of 2000-3000m, a segmented fracturing section length of 50-150m, and 3-5 clusters or even 8-10 clusters per section. However, the post-fracture effect is uneven. In each segment of fracturing construction, how many fractures can be formed under different geological and engineering parameters, and whether the fractures can be effectively extended have always been a matter of confusion in the industry and urgent need for research.

[0003] The Chinese invention patent with publication date of March 29, 2017 and publication number CN102292518B: Well monitoring using distributed sensing devices, discloses a method for downhole monitoring, where optical fibers are arranged along the borehole path of a fracturing well or an adjacent well to provide distributed acoustic and strain monitoring, and data collected from multiple continuous sections of the optical fiber can be processed to determine the perforation cluster fluid inflow and crack expansion in the fracturing construction section. This technology uses permanent optical fibers, which are not only costly, difficult to install equipment and interpret data, but also affected by the accuracy and precision of the mathematical model and the interference of heterogeneity on reservoir rock mechanics / acoustic sensing, which will cause uncertainty in the monitoring results.

[0004] The Chinese invention patent with a publication date of December 9, 2022 and publication number CN115450609A: A bottom hole monitoring device and method for cluster parameters of staged fracturing in horizontal wells. A monitoring device is lowered into the cluster in each fracturing section of the horizontal well to measure the injection pressure, temperature and flow rate of each fracturing section cluster. After the construction of each section is completed, data inversion can be quickly performed to determine the crack expansion of the fracturing construction section. At present, a 1000m horizontal section needs to be transformed into 10-15 sections, with 3-5 clusters or even more in each section. After the fracturing of the previous section is completed, the equipment is installed in the next transformation section. A single well needs to be installed 10-15 times, which seriously affects work efficiency. In addition, considering the high-speed flushing of liquid at the perforation holes, it is a very challenging task to install and fix the device at the bottom of a horizontal well several thousand meters deep and ensure that the device works effectively throughout the entire process.

[0005] The above-mentioned methods for evaluating the effectiveness of multi-cluster fracture extension in horizontal wells all require the installation of special equipment, and the installation process is difficult and costly. Therefore, it is urgent to explore a simple and low-cost method for evaluating the effectiveness of multi-cluster fracturing fractures in horizontal wells to provide a reliable basis for optimizing fracturing schemes under different geological conditions, increase oil and gas production, and improve economic benefits. Summary of the invention

[0006] The purpose of the present invention is to provide a monitoring method for the effectiveness and fracture morphology of multi-cluster fracture extension in horizontal wells, which solves the problem that the existing evaluation method for the effectiveness of multi-cluster fracture extension in horizontal wells needs to install special equipment, the installation process is difficult and costly, and the monitoring results are affected by the accuracy of the mathematical model and the interference of heterogeneity on the mechanics / acoustic induction of the reservoir rock, which will cause uncertainty.

[0007] The technical solution adopted by the present invention is a method for monitoring the effectiveness of multi-cluster fracture extension and fracture morphology in a horizontal well, comprising the following steps:

[0008] S1: Select the well that needs to analyze the effectiveness of fracture extension as the construction well, select monitoring wells around the construction well, install high-precision pressure gauges, and cement and complete the monitoring wells;

[0009] S2: Fill the monitoring well with filling fluid and test the sealing performance of the monitoring wellbore;

[0010] S3: Carry out the first stage of fracturing operation on the construction well, collect data of corresponding variables during the first stage of fracturing operation through a high-precision pressure gauge, and establish the relationship between the variables as a comparison standard;

[0011] S4: Carry out the second stage of fracturing operation on the construction well, collect data of corresponding variables during the second stage of fracturing operation through a high-precision pressure gauge, compare the measured variable data with the standard obtained in S3, analyze the position of the main deformation cement sheath, and determine the number and shape of effective perforation clusters;

[0012] S5: Repeat S4 to carry out fracturing operations of the 3rd to N / 2th stages, summarize the crack expansion law of the 1st to N / 2th fracturing stages, and optimize the process parameters of the N / 2nd to Nth fracturing stages according to the expansion law;

[0013] S6: Referring to the optimized fracturing process parameters, repeat S4 to carry out the N / 2 to Nth stage fracturing operations, and analyze and clarify the optimal fracturing process parameters and crack extension morphology of the corresponding block.

[0014] The present invention is also characterized in that:

[0015] The specific method for selecting monitoring wells in S1 is: taking the construction wellbore as the axis, within a circle with a radius of 20 to 500 m, select no less than one adjacent well as a monitoring well. The monitoring well is guaranteed not to be perforated or installed with a toe sleeve, ensuring that the wellbore is absolutely intact, absolutely isolated from the reservoir, and has no fluid flow channel.

[0016] The S1 medium and high precision pressure gauge is installed at the bottom or wellhead of the monitoring well. The measurement accuracy of the high precision pressure gauge is 10~100Pa and the range is 50~100kPa.

[0017] The specific operations of cementing and completing the monitoring well in S1 are: optimizing the multi-stage cementing slurry system, testing the mechanical parameters of each cementing slurry system after solidification and the compression deformation under different pressures, using a single type of standard cement slurry system for cementing at the position corresponding to the first fracturing stage of the construction well, and using different types of cement slurry systems for cementing at the positions corresponding to the perforation clusters of other fracturing stages of the construction well.

[0018] The filling liquid in S2 is a slightly compressible liquid with a volume of 0.5 to 1.0 m 3 / min is injected into the monitoring well until it is full, and the compressibility and pressure conductivity of the slightly compressible liquid are tested.

[0019] The specific method for testing the sealing of the monitoring wellbore in S2 is: increase the wellhead pressure of the monitoring well to 30MPa, stabilize the pressure for 10 minutes and then test the sealing of the wellbore. If the pressure drop is greater than 0.7MPa, abandon the well and re-select other monitoring wells. If the pressure drop is less than 0.7MPa, it is qualified, then lower the wellhead pressure to 10-20MPa.

[0020] The data collected by the high-precision pressure gauges in S3 and S4 are the corresponding pumping displacement, pumped fracturing fluid volume, wellhead pressure change and pressure growth rate during fracturing of the construction well when the measured pressure growth rate is greater than 5MPa / min; the relationship between the variables is established as follows: the mathematical relationship between the deformation of the cement ring casing and the bottom hole / wellhead pressure change is formula 1, and the mathematical relationship between the seam length / seam width / seam height and the pumping displacement, pumped fracturing fluid volume, wellhead pressure change and pressure growth rate is formula 2.

[0021]

[0022] In the formula, δ 套管 is the casing deformation, k 套管 and k 充填液 are the compression coefficients of casing and filling fluid, Δp 井口 is the wellhead pressure change, where the filling fluid pressure conductivity coefficient a is a function of the inverse of the filling fluid compressibility coefficient f(1 / k 充填液 );

[0023]

[0024] In the formula, (H f ,L f ,w f ) are the height, length and width of the cracks formed in the fracturing well, V 液量 is the volume of pumped fracturing fluid, Q 压裂液 The pumping rate of fracturing fluid.

[0025] The specific steps of fracturing the construction wells in S3 and S4 are as follows: according to the reservoir drilling rate and reservoir physical property parameters of the horizontal wells under fracturing construction, the positions of the fracturing sections and the perforation clusters in each section are determined. The length of the fracturing section is 50 to 150 m, and the cluster spacing is 10 to 50 m. The cementing length of each stage of the monitoring well is consistent with the perforation cluster spacing of the construction well. The total number of fracturing sections is N sections, of which one cluster is perforated in the first section to ensure that one fracture is generated in this section. The cluster is perforated continuously for 1 m, with a hole density of 16 holes / m and a phase angle of 60°.

[0026] In S4, according to the corresponding pumping time, liquid volume injected into the ground, pressure increment and pressure growth rate parameters when the pressure growth rate is greater than 5 MPa / min measured by the high-precision pressure gauge in S3, the position of the cement ring where the main deformation occurs is analyzed, and the perforation cluster opening efficiency, the number of crack initiation and expansion, the crack expansion rate, the crack length, the crack height and the crack morphology on both sides of the wellbore are determined.

[0027] The specific method for summarizing the rules and optimizing the process parameters in S5 is: according to the corresponding relationship between the number of perforation clusters, pumping displacement, pumped fracturing fluid volume and fracture morphology in the 1-N / 2 fracturing stages, the number of perforation clusters, pumping displacement, and pumped fracturing fluid volume in the N / 2-N fracturing stages are adjusted and optimized.

[0028] The beneficial effects of the present invention are as follows: the monitoring method for the effectiveness of multi-cluster fracture extension and fracture morphology in horizontal wells provided by the present invention does not require any tools to enter the well, the monitoring method is simple, and the operation risk is low. At the same time, measured data such as actual pressure response and fluid volume entering the well are used as input parameters, and the output result has reduced uncertainty. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a wellbore location distribution diagram of the construction well and the monitoring well in Example 1 of the method of the present invention;

[0030] Figure 2 Schematic diagram of the perforation scheme of the fracturing construction well and the multi-stage cementing effect of the monitoring well in Example 1 of the method of the present invention;

[0031] Figure 3 It is a schematic diagram of the fracturing construction curve of the fracturing construction well and the pressure change process of the monitoring well in Example 1 of the method of the present invention.

[0032] In the figure, 1. construction well, 2. monitoring well, 3. casing, 4. cement ring, 5. perforation cluster, 6. high-precision pressure gauge, 7. fracturing crack. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] A method for monitoring the effectiveness of multi-cluster fracture extension and fracture morphology in a horizontal well includes the following steps:

[0035] S1: Select the well for which the effectiveness of fracture extension needs to be analyzed as the construction well, select monitoring wells around the construction well, install high-precision pressure gauges, and cement and complete the monitoring wells.

[0036] The method for selecting monitoring wells is as follows: taking the horizontal wellbore of the fracturing construction well as the axis, one or more adjacent wells are selected as monitoring wells on a circle with a radius of 20 to 500 m, with a horizontal distance of 20 to 500 m and a vertical distance of 0 to 50 m from the horizontal wellbore of the fracturing construction well. The wellbore must be absolutely intact, without perforation or installation of toe sleeves after cementing, and absolutely isolated from the reservoir and without fluid flow channels; the selected one or more monitoring wells can have a horizontal wellbore located at the same layer and height as the fracturing construction well, which is used to monitor and evaluate the expansion speed, length, and fracturing efficiency of the cracks; the horizontal wellbore can also be located at a different layer and height from the fracturing construction well, which can evaluate the vertical expansion height of the cracks in addition to monitoring and evaluating the horizontal expansion law of the cracks.

[0037] High-precision pressure gauges are installed at the bottom or wellhead of horizontal wells. The bottom-hole pressure gauge does not need to pass through the wellbore liquid pressure transmission, so the accuracy is more accurate. In some cases, in order to simplify the workflow and installation difficulty, the pressure gauge can also be installed at the wellhead of the horizontal well. The measurement accuracy of the high-precision pressure gauge is 10~100Pa, and the range is 50~100kPa.

[0038] The specific operations of cementing and completing the monitoring well are as follows: optimizing the multi-stage cementing slurry system to ensure that the cementing cement ring at the wellbore position corresponding to each perforation cluster in the proposed transformation section of the fracturing construction well has different mechanical properties, testing the mechanical parameters of each cementing cement slurry system after solidification and the compression deformation under different pressures, using a single type of standard cement slurry system for cementing at the position corresponding to the first fracturing section of the construction well, and using different types of cement slurry systems for cementing at the positions corresponding to the perforation clusters of other fracturing sections of the construction well.

[0039] The multi-stage cementing process uses a variety of cement slurry systems with different mechanical properties to perform sequential, multi-stage, and continuous cementing within a length range of 50 to 150 m corresponding to the position of the simulated fracturing section, with each stage cementing length being 10 to 50 m; the total length of the multi-stage cementing is consistent with the length of the simulated fracturing section, and the length of each stage of cementing is consistent with the spacing between perforation clusters; the multi-stage cementing cement slurry changes its mechanical properties such as Young's modulus and Poisson's ratio after solidification by optimizing cement slurry density, composition, concentration and other parameters without affecting the strength of the cement sheath, so that each stage of the cementing cement sheath produces different deformations after being subjected to the same extrusion pressure.

[0040] The cementing slurry is injected into the annular space between the casing and the drilling wellbore. After complete solidification, the compressive strength can reach more than 80MPa; the type of cement slurry is consistent with the maximum number of perforation clusters in a single section of the horizontal well.

[0041] The casing is a standard casing used in the oil and gas well drilling and completion industry. It is a heat-resistant, pressure-resistant, and corrosion-resistant metal tubular material with an inner diameter of 80 to 150 cm (smaller than the inner diameter of the drilling wellbore) and a wall thickness of 5 to 10 mm.

[0042] S2: 0.5~1.0m 3 The monitoring well is filled with the filling fluid system at a displacement of / min, and the sealing of the monitoring wellbore is tested.

[0043] The wellbore filling fluid uses a slightly compressible liquid, usually a 2% to 10% KCl solution. The compressibility and pressure conductivity of the liquid are further reduced by pressurizing it at the wellhead to 10 to 20 MPa, and the compression coefficient and pressure conductivity coefficient of the slightly compressible liquid are tested.

[0044] During the fracturing operation of the fracturing well, the monitoring well is filled with slightly compressible liquid. When the crack extends to the periphery of the monitoring well or intersects with the cementing ring of the monitoring well, the cementing ring is deformed by compression, and the pressure is transmitted to the high-precision pressure gauge at the bottom of the well or at the wellhead through the slightly compressible liquid in the wellbore. According to the parameters such as the pressure response time, response intensity and pump injection volume, the important information such as the starting position of the effective expansion of the crack in the fracturing section, the efficiency of the perforation cluster, the crack length, the crack height and the expansion morphology of the crack on both sides of the wellbore are analyzed to guide the optimization of the horizontal well segmented multi-cluster fracturing plan and improve the development effect of oil and gas reservoirs.

[0045] The specific method for testing the sealing of the monitoring wellbore is: increase the wellhead pressure of the monitoring well to 30MPa, stabilize the pressure for 10 minutes and then test the sealing of the wellbore. If the pressure drop is greater than 0.7MPa, abandon the well and reselect other adjacent wells as monitoring wells. If the pressure drop is less than 0.7MPa, it is qualified, then lower the wellhead pressure to 10-20MPa.

[0046] S3: Carry out the first stage of fracturing operation on the construction well, collect data of corresponding variables during the first stage of fracturing operation through high-precision pressure gauge, specifically: corresponding pumping displacement when the pressure growth rate is greater than 5MPa / min, pumped fracturing fluid volume, wellhead / bottomhole pressure change and pressure growth rate, etc., and establish the relationship between each variable. As a comparison standard, the relationship between each variable is established as follows: the mathematical relationship between the deformation of cementing cement ring casing and the bottomhole / wellhead pressure change (Formula 1), the mathematical relationship between the seam length / seam width / seam height and the pumping displacement, pumped fracturing fluid volume, wellhead pressure change and pressure growth rate (Formula 2),

[0047]

[0048] In the formula, δ 套管 is the casing deformation, k 套管 and k 充填液 are the compression coefficients of casing and filling fluid, Δp 井口 is the wellhead pressure change, where the filling fluid pressure conductivity coefficient a is a function of the inverse of the filling fluid compressibility coefficient f(1 / k 充填液 ).

[0049]

[0050] In the formula, (H f ,L f ,w f ) are the height, length and width of the cracks formed in the fracturing well, V 液量 is the volume of pumped fracturing fluid, Q 压裂液 The pumping rate of fracturing fluid.

[0051] The specific steps of fracturing operation for construction wells are as follows: according to the reservoir drilling rate, reservoir physical properties and other parameters of the horizontal well under fracturing construction, the positions of the fracturing sections and the perforation clusters in each section are determined. The length of the fracturing section is 50 to 150 m, the cluster spacing is 10 to 50 m, the length of each cementing stage is consistent with the perforation cluster spacing, and the total number of fracturing sections is N. Only one cluster is perforated in the first section to ensure that only one fracture is generated in this section. The cluster is perforated continuously for 1 m, with a hole density of 16 holes / m and a phase angle of 60°.

[0052] S4: Carry out the second stage of fracturing operation on the construction well, compare the pressure change pattern of the monitoring well with the standard, and collect data on the corresponding variables during the second stage of fracturing operation through a high-precision pressure gauge: parameters such as pumping time, liquid volume entering the ground, pressure increment and pressure growth rate corresponding to the pressure growth rate greater than 5MPa / min, analyze the position of the cement ring where the main deformation occurs, determine the perforation cluster opening efficiency, the number of crack initiation and expansion, the crack expansion rate, the crack length, the crack height, and the crack morphology on both sides of the wellbore.

[0053] S5: Repeat S4 to carry out fracturing operations in the 3rd to N / 2th stages, and summarize the crack expansion law of the 1st to N / 2th fracturing stages. According to the law, optimize the process parameters of the N / 2nd to N / 2nd fracturing stages. The specific method is: according to the correspondence between the number of perforation clusters, pumping displacement, volume of pumped fracturing fluid and crack morphology of the 1st to N / 2nd fracturing stages, then adjust and optimize the fracturing process parameters such as the number of perforation clusters, pumping displacement, volume of pumped fracturing fluid and so on of the N / 2nd to N / 2nd fracturing stages.

[0054] S6: Referring to the optimized fracturing process parameters, repeat S4, carry out the N / 2 to Nth stage fracturing operations, analyze and clarify the optimal fracturing process parameters and crack extension morphology of the corresponding block, that is: calculate the length, width and height of each fracturing crack according to the formula in S3, form the law between fracturing parameters and crack extension morphology, and guide the clarification of the optimal fracturing process parameters for the block.

[0055] Example 1

[0056] A method for monitoring the effectiveness of multi-cluster fracture extension and fracture morphology in a horizontal well includes the following steps:

[0057] S1: Select the wells for which the effectiveness of fracture extension needs to be analyzed as the construction wells, select monitoring wells around the construction wells, and select three adjacent wells with horizontal distances of 50m, 100m and 150m and vertical distances of 0m, 10m and 20m from the fracturing construction well 1 as monitoring well 2, and install high-precision pressure gauges to cement and complete the monitoring wells: Select four cementing slurry systems, test the mechanical parameters after solidification and the corresponding compression deformation under different pressures for each system, wherein the position corresponding to the first fracturing stage is cemented with a single type and standard cement slurry system, and the corresponding positions of each perforation cluster of other fracturing stages are cemented with different types of cement slurries with different mechanical properties; wherein the position corresponding to the first fracturing stage of the construction well is cemented with a single type and standard cement slurry system, and the corresponding positions of each perforation cluster of other fracturing stages are cemented with different types of cement slurries with different mechanical properties.

[0058] S2: Fill the monitoring well with filling fluid, using 2% to 10% KCl solution, test the compression coefficient and pressure conductivity coefficient of the wellbore filling fluid at 10 to 20 MPa, and test the sealing of the monitoring wellbore.

[0059] S3: Carry out the first stage of fracturing operation on the construction well, collect data of corresponding variables during the first stage of fracturing operation through high-precision pressure gauge, and establish the relationship between each variable as a comparison standard.

[0060] S4: Carry out the second stage of fracturing operation on the construction well, collect data of corresponding variables during the second stage of fracturing operation through high-precision pressure gauge, compare the measured variable data with the standard, analyze the position of the main deformation cement ring, and determine the number and shape of effective perforation clusters.

[0061] S5: Repeat S4 to carry out the third stage of fracturing operation, and summarize the crack expansion law of fracturing stages 1 to 3. According to the expansion law, optimize the process parameters of fracturing stages 4 to 5.

[0062] S6: Referring to the optimized fracturing process parameters, repeat S4 to carry out the 4th to 5th stage fracturing operations, and analyze and clarify the optimal fracturing process parameters and crack extension morphology of the corresponding block.

[0063] like Figure 1 , Figure 2 and Figure 3 As shown, a monitoring method for the effectiveness of multi-cluster fracture extension and fracture morphology in a horizontal well includes a fracturing construction well 1, a monitoring well 2, a casing 3, a cementing cement ring 4, a perforation cluster 5, a high-precision pressure gauge 6, and a fracturing fracture 7. The monitoring well 2 is horizontally 20-500 m away from the fracturing construction well 1. The wellbore is completely isolated from the reservoir. Differentiated graded cementing is performed using a variety of cementing mud systems to ensure that the cementing cement ring 4 at the wellbore position corresponding to each perforation cluster in the proposed transformation section of the fracturing construction well has different mechanical properties.

[0064] Example 2

[0065] S1: Select the well that needs to be analyzed for the effectiveness of fracture extension as the construction well, select monitoring wells around the construction well, install high-precision pressure gauges, and cement and complete the monitoring wells. The specific method is as follows:

[0066] With the horizontal wellbore of the fracturing construction well as the axis, two adjacent wells are selected as monitoring wells on a circle with a radius of 20 to 500 m. The horizontal distance from the horizontal wellbore of the fracturing construction well is 200 m and the vertical distance is 30 m. The wellbore must be absolutely intact, no perforation is performed after cementing, no toe sleeve is installed, and it is absolutely isolated from the reservoir and has no fluid flow channel.

[0067] A high-precision pressure gauge is installed at the bottom of a horizontal well. The bottom-hole pressure gauge is more accurate because it does not need to pass through the wellbore liquid pressure transmission. The high-precision pressure gauge has a measurement accuracy of 10 to 100 Pa and a range of 50 to 100 kPa.

[0068] Cementing and completion of monitoring wells: A multi-stage cementing slurry system is selected to ensure that the cementing cement ring at the wellbore position corresponding to each perforation cluster in the proposed stimulation section of the fracturing construction well has different mechanical properties. The mechanical parameters of each cementing cement slurry system after solidification and the compression deformation under different pressures are tested. The position corresponding to the first fracturing section is cemented with a single type of standard cement slurry system, and the corresponding positions of each perforation cluster in other fracturing sections are cemented with different types of cement slurry systems with different mechanical properties.

[0069] S2: Fill the monitoring well with filling fluid and test the sealing of the monitoring wellbore.

[0070] S3: Carry out the first stage of fracturing operation on the construction well, collect data of corresponding variables during the first stage of fracturing operation through high-precision pressure gauge, and establish the relationship between each variable as a comparison standard.

[0071] S4: Carry out the second stage of fracturing operation on the construction well, collect data of corresponding variables during the second stage of fracturing operation through high-precision pressure gauge, compare the measured variable data with the standard, analyze the position of the main deformation cement ring, and determine the number and shape of effective perforation clusters.

[0072] S5: Repeat S4 to carry out fracturing operations in stages 3 to N / 2, and summarize the crack expansion rules of stages 1 to N / 2. According to the expansion rules, optimize the process parameters of stages N / 2 to N.

[0073] S6: Referring to the optimized fracturing process parameters, repeat S4 to carry out the N / 2 to Nth stage fracturing operations, and analyze and clarify the optimal fracturing process parameters and crack extension morphology of the corresponding block.

[0074] Example 3

[0075] S1: Select the well for which the effectiveness of fracture extension needs to be analyzed as the construction well, select monitoring wells around the construction well, install high-precision pressure gauges, and cement and complete the monitoring wells.

[0076] S2: Fill the monitoring well with filling fluid and test the sealing of the monitoring well. The specific method is as follows: 3 The monitoring well is filled with a filling liquid system at a displacement of / min. A 2% KCl solution is used as the wellbore filling liquid. The compressibility and pressure conductivity of the liquid are further reduced by pressurizing the wellhead by 20MPa, and a mathematical relationship between the deformation of the cementing sheath and the increase in bottom hole / wellhead pressure is established. During the fracturing operation of the fracturing well, the monitoring well is filled with slightly compressible liquid. When the crack extends to the periphery of the monitoring well or intersects with the cementing sheath of the monitoring well, the cementing sheath is deformed by compression, and the pressure is transmitted to the high-precision pressure gauge at the bottom hole or wellhead through the slightly compressible liquid in the wellbore. According to parameters such as the pressure response time, response intensity and pump injection volume, important information such as the starting position of the effective expansion of the crack in the fracturing section, the efficiency of the perforation cluster, the crack length, the crack height and the expansion morphology of the crack on both sides of the wellbore are analyzed to guide the optimization of the multi-cluster fracturing scheme of horizontal wells and improve the development effect of oil and gas reservoirs.

[0077] The specific method for testing the sealing performance of the monitoring wellbore is as follows: increase the wellhead pressure of the monitoring well to 30MPa, stabilize the pressure for 10 minutes and then test the wellbore sealing performance. If the pressure drop is greater than 0.7MPa, the well will be abandoned and other adjacent wells will be re-selected as monitoring wells. If the pressure drop is less than 0.7MPa, it is qualified, then the wellhead pressure will be lowered to 10-20MPa.

[0078] S3: Carry out the first stage of fracturing operation on the construction well, collect data of corresponding variables during the first stage of fracturing operation through high-precision pressure gauge, and establish the relationship between each variable as a comparison standard.

[0079] S4: Carry out the second stage of fracturing operation on the construction well, collect data of corresponding variables during the second stage of fracturing operation through high-precision pressure gauge, compare the measured variable data with the standard, analyze the position of the main deformation cement ring, and determine the number and shape of effective perforation clusters.

[0080] S5: Repeat S4 to carry out fracturing operations in stages 3 to N / 2, and summarize the crack expansion rules of stages 1 to N / 2. According to the expansion rules, optimize the process parameters of stages N / 2 to N.

[0081] S6: Referring to the optimized fracturing process parameters, repeat S4 to carry out the N / 2 to Nth stage fracturing operations, and analyze and clarify the optimal fracturing process parameters and crack extension morphology of the corresponding block.

[0082] Example 4

[0083] S1: Select the well for which the effectiveness of fracture extension needs to be analyzed as the construction well, select monitoring wells around the construction well, install high-precision pressure gauges, and cement and complete the monitoring wells.

[0084] S2: Fill the monitoring well with filling fluid and test the sealing of the monitoring wellbore.

[0085] S3: Carry out the first stage of fracturing operation on the construction well, collect data of corresponding variables during the first stage of fracturing operation through high-precision pressure gauge, and establish the relationship between each variable as a comparison standard.

[0086] The first stage of fracturing operation was carried out on the construction well. The specific steps were as follows: according to the reservoir drilling rate, reservoir physical properties and other parameters of the horizontal well under fracturing construction, the positions of the fracturing sections and the perforation clusters in each section were determined. The length of the fracturing section was 50-150 m, the cluster spacing was 10-50 m, the length of each cementing stage was consistent with the perforation cluster spacing, the total number of fracturing sections was N, and only one cluster was perforated in the first section; the corresponding data were collected through a high-precision pressure gauge: the corresponding pumping time, the amount of liquid entering the ground, the pressure increment and the pressure growth rate when the pressure growth rate was greater than 5 MPa / min, and the relationship between the variables was established: the relationship between the compression deformation of the cement sheath formed by the solidification of the standard cement slurry system and the pressure change at different stages of crack expansion was established as a reference for the analysis of the crack expansion effect of other fracturing sections.

[0087] S4: Carry out the second stage of fracturing operation on the construction well, compare the pressure change of the monitoring well with the standard, analyze the position of the main deformed cement ring according to the data of S3, and determine the number and shape of effective perforation clusters: Carry out the second stage of fracturing operation on the construction well, compare the pressure change pattern of the monitoring well with the standard, and analyze the position of the cement ring with major deformation according to the parameters such as pumping time, liquid volume entering the ground, pressure increment and pressure growth rate corresponding to the sudden pressure increase measured by the high-precision pressure gauge in S3, and determine the opening efficiency of the perforation cluster, the number of crack initiation and expansion, crack expansion rate, crack length, crack height, and crack shape on both sides of the wellbore.

[0088] S5: Repeat S4 to carry out fracturing operations in stages 3 to N / 2, and summarize the crack expansion rules of stages 1 to N / 2. Based on the rules, optimize the process parameters of stages N / 2 to N.

[0089] S6: Referring to the optimized fracturing process parameters, repeat S4 to carry out the N / 2 to Nth stage fracturing operations, and analyze and clarify the optimal fracturing process parameters and crack extension morphology of the corresponding block.

Claims

1. A method for monitoring the effectiveness of multi-cluster fracture extension and fracture morphology in horizontal wells, characterized in that: The following steps are involved: S1: Select the well that needs to analyze the effectiveness of fracture extension as the construction well, select monitoring wells around the construction well, install high-precision pressure gauges, and cement and complete the monitoring wells; S2: Fill the monitoring well with filling fluid and test the sealing performance of the monitoring wellbore; S3: carrying out the first stage of fracturing operation on the construction well, collecting data of corresponding variables during the first stage of fracturing operation by means of a high-precision pressure gauge, and establishing a relationship between the variables as a comparison standard; S4: Carry out the second stage of fracturing operation on the construction well, collect data of corresponding variables during the second stage of fracturing operation through a high-precision pressure gauge, compare the measured variable data with the standard obtained in S3, analyze the position of the main deformation cement sheath, and determine the number and shape of effective perforation clusters; S5: Repeat S4 to carry out fracturing operations of the 3rd to N / 2th stages, summarize the crack expansion law of the 1st to N / 2th fracturing stages, and optimize the process parameters of the N / 2nd to Nth fracturing stages according to the expansion law; S6: Referring to the optimized fracturing process parameters, repeat S4 to carry out the N / 2 to Nth stage fracturing operations, and analyze and clarify the optimal fracturing process parameters and crack extension morphology of the corresponding block.

2. The method for monitoring the effectiveness of multi-cluster fracture extension and fracture morphology in horizontal wells according to claim 1, characterized in that: The specific method for selecting the monitoring well in S1 is: taking the construction wellbore as the axis, within a circle with a radius of 20 to 500 m, select no less than one adjacent well as a monitoring well, and ensure that the monitoring well is not perforated and does not install a toe end sliding sleeve, and ensure that the wellbore is absolutely intact, absolutely isolated from the reservoir, and has no fluid flow channel.

3. The method for monitoring the effectiveness of extension and morphology of multiple clusters of fractures in horizontal wells according to claim 2, characterized in that: The high-precision pressure gauge in S1 is installed at the bottom or wellhead of the monitoring well. The measurement accuracy of the high-precision pressure gauge is 10-100Pa and the range is 50-100kPa.

4. The method for monitoring the effectiveness of extension and morphology of multiple clusters of fractures in horizontal wells according to claim 3, characterized in that: The specific operations of cementing and completing the monitoring well in S1 are: selecting a multi-stage cementing slurry system, testing the mechanical parameters of each cementing slurry system after solidification and the compression deformation under different pressures, using a single type of standard cement slurry system for cementing at the position corresponding to the first fracturing stage of the construction well, and using different types of cement slurry systems for cementing at the positions corresponding to the perforation clusters of other fracturing stages of the construction well.

5. The method for monitoring the effectiveness of extension and morphology of multiple clusters of fractures in horizontal wells according to claim 1, characterized in that: The filling liquid in S2 is a slightly compressible liquid with a volume of 0.5 to 1.0 m 3 / min is injected into the monitoring well until it is full, and the compressibility coefficient and pressure conductivity coefficient of the slightly compressible liquid are tested.

6. The method for monitoring the effectiveness of extension and morphology of multiple clusters of fractures in horizontal wells according to claim 1, characterized in that: The specific method for testing the sealing performance of the monitoring wellbore in S2 is: increase the wellhead pressure of the monitoring well to 30MPa, stabilize the pressure for 10 minutes and then test the sealing performance of the wellbore; if the pressure drop is greater than 0.7MPa, abandon the well and reselect other monitoring wells; if the pressure drop is less than 0.7MPa, it is qualified, then lower the wellhead pressure to 10-20MPa.

7. The method for monitoring the effectiveness of extension and morphology of multiple clusters of fractures in horizontal wells according to claim 1, characterized in that: The data collected by the high-precision pressure gauges in S3 and S4 are the corresponding pumping displacement, pumped fracturing fluid volume, wellhead pressure change and pressure growth rate during fracturing of the construction well when the measured pressure growth rate is greater than 5MPa / min; the relationship between the variables is established as follows: the mathematical relationship between the deformation of the cement ring casing and the bottom hole / wellhead pressure change is Formula 1, and the mathematical relationship between the seam length / seam width / seam height and the pumping displacement, pumped fracturing fluid volume, wellhead pressure change and pressure growth rate is Formula 2, In the formula, δ 套管 is the casing deformation, k 套管 and k 充填液 are the compression coefficients of casing and filling fluid, Δp 井口 is the wellhead pressure change, where the filling fluid pressure conductivity coefficient a is a function of the inverse of the filling fluid compressibility coefficient f(1 / k 充填液 ); In the formula, (H f ,L f ,w f ) are the height, length and width of the cracks formed in the fracturing well, V 液量 is the volume of fracturing fluid pumped, Q 压裂液 The pumping rate of fracturing fluid.

8. The method for monitoring the extension effectiveness and fracture morphology of multiple cluster fractures in horizontal wells according to claim 1, characterized in that: The specific steps of fracturing the construction well in S3 and S4 are as follows: according to the reservoir drilling rate and reservoir physical property parameters of the horizontal well under fracturing construction, the positions of the fracturing sections and the perforation clusters in each section are determined; the length of the fracturing section is 50 to 150 m, the cluster spacing is 10 to 50 m, the cementing length of each stage of the monitoring well is consistent with the perforation cluster spacing of the construction well, the total number of fracturing sections is N sections, wherein the first section has one cluster of perforations to ensure that one fracture is generated in the section, the cluster is perforated continuously for 1 m, the hole density is 16 holes / m, and the phase angle is 60°.

9. The method for monitoring the extension effectiveness and fracture morphology of multiple cluster fractures in horizontal wells according to claim 1, characterized in that: In S4, according to the corresponding pumping time, amount of liquid entering the ground, pressure increment and pressure growth rate parameters when the pressure growth rate is greater than 5 MPa / min measured by the high-precision pressure gauge in S3, the position of the cement ring where the main deformation occurs is analyzed to determine the perforation cluster opening efficiency, the number of crack initiation and expansion, the crack expansion rate, the crack length, the crack height, and the crack morphology on both sides of the wellbore.

10. The method for monitoring the extension effectiveness and fracture morphology of multiple clusters of fractures in horizontal wells according to claim 1, characterized in that: The specific method for summarizing the rules and optimizing the process parameters in S5 is: according to the corresponding relationship between the number of perforation clusters, pumping displacement, pumped fracturing fluid volume and fracture morphology in the 1 to N / 2 fracturing stages, the number of perforation clusters, pumping displacement, and pumped fracturing fluid volume in the N / 2 to N fracturing stages are adjusted and optimized.

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