Dynamic evaluation method for repeated reconstruction of shale gas fracturing well

Abstract

The present application relates to the field of shale gas storage development and stimulation technology, in particular to a shale gas fracturing well repeated reconstruction dynamic evaluation method, which comprises: using a hydraulic pulse plugging removal device to repeatedly reconstruct the well section of the target well that has repeated reconstruction potential, and collecting the pulse pressure curve of the hydraulic pulse plugging removal device in real time; in response to the change of the pulse pressure curve waveform from the first waveform to the second waveform, it is determined that the shale gas fracturing well repeated reconstruction is completed, otherwise it is determined that the shale gas fracturing well repeated reconstruction is not completed. It can evaluate the repeated reconstruction completion degree in real time, realize the efficient, real-time and continuous repeated reconstruction process, fully develop and utilize the shale gas resources, and maximize the gas well productivity and improve the resource recovery rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shale gas storage development and stimulation, and particularly relates to a shale gas fractured well repeated reconstruction dynamic evaluation method. BACKGROUND

[0002] With the development of global economy, energy demand continues to rise. Shale gas, as an important unconventional natural gas resource, its large-scale development can significantly increase the natural gas production of a country or region, thereby reducing the dependence on imported natural gas and other traditional fossil energy, effectively improving the energy self-sufficiency rate, and ensuring the stability and security of energy supply.

[0003] The geological structure of shale gas reservoir is complex, and the initial fracturing reconstruction and other mining measures often cannot completely mine the shale gas resources in it, and a considerable part of the remaining reserves will be left in the formation. Through repeated reconstruction, the natural fracture network in the formation can be further communicated, and the gas discharge area can be expanded, so that the remaining shale gas that has not been effectively mined can be mined, thereby improving the resource recovery rate of the entire shale gas well and realizing more sufficient utilization of shale gas resources. Since the original cracks fail in the process of shale gas mining, including chemical scaling and deposition caused plugging, particle migration caused plugging, etc., therefore, the plugging of the shale gas well is an important link of repeated reconstruction.

[0004] The existing repeated reconstruction is difficult to achieve ideal effect, mainly including two reasons. First, the selection of repeated reconstruction section and the selection of repeated reconstruction time are difficult to accurately grasp, and the change of engineering and geological conditions in the dynamic construction process of repeated reconstruction is not considered, causing the lag of engineering practice. Secondly, during the repeated reconstruction process, whether the repeated reconstruction of a section is completed or not is not real-time and quantitative evaluation, and the insufficient reconstruction time is difficult to form effective cracks, and the excessive reconstruction time may cause the collapse and deformation of the wellbore. Therefore, it is necessary to dynamically evaluate the repeated reconstruction and real-time evaluate the completion degree of each repeated reconstruction.

[0005] At present, the selection of repeated reconstruction section is only determined according to the logging curve and the previous fracturing construction curve, and there is no further evaluation and reconstruction after repeated reconstruction construction; the existing plugging method of repeated reconstruction well includes ordinary acid washing, hydraulic vibration method, electro-hydraulic pulse method, etc., but these methods have certain limitations, such as small cleaning range, poor plugging effect, high operation difficulty, high operation cost, easy to cause environmental pollution and the like. And the judgment of whether the repeated reconstruction process is completed mainly depends on the pre-designed test scheme or relies on the single flow change, which has a certain lag. SUMMARY

[0006] The shale gas fracturing well repeated reconstruction dynamic evaluation method can realize real-time dynamic evaluation of repeated reconstruction completion, efficient, real-time and continuous repeated reconstruction process, fully repeated development and utilization of shale gas resources, and maximized tapping of gas well productivity and improved resource recovery ratio.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] The shale gas fracturing well repeated reconstruction dynamic evaluation method provided by the present application comprises the following steps:

[0009] Further, the first waveform is an irregular sine wave, and the second waveform is a regular sine wave.

[0010] Further, the judgment method of the pulse pressure curve waveform is as follows: three peak values P1, P2 and P3 near the end section of the pulse pressure curve and time points t1, t2 and t3 corresponding to the three peak values are obtained; when P1=P2=P3 and t3-t2=t2-t1, it is determined that the pulse pressure curve waveform is the second waveform, i.e., the regular sine wave; otherwise, it is determined that the pulse pressure curve waveform is the first waveform, i.e., the irregular sine wave.

[0011] Further, the well section with repeated reconstruction potential of the target wellbore is determined according to the previous logging curve and fracturing construction curve of the target wellbore; the logging curve comprises a resistivity curve, an acoustic travel time curve, a density curve, a porosity curve and a natural gamma curve; and the fracturing construction curve comprises a construction pressure curve, a displacement curve, a sand ratio curve, a net pressure curve and a microseismic monitoring curve.

[0012] Further, the determination of the well section with repeated reconstruction potential of the target wellbore specifically comprises the following steps: the target wellbore is divided into a plurality of well sections according to a preset length; whether the wellbore integrity, the formation reserves and the remaining production of the well section meet the preset requirements is evaluated; when the wellbore integrity, the formation reserves and the remaining production all meet the preset requirements, it is determined that the well section has repeated reconstruction potential; otherwise, it is determined that the well section does not have repeated reconstruction potential.

[0013] The wellbore integrity evaluation includes: using the resistivity curve to determine whether corrosion or cracks exist in the casing wall of the wellbore, using the natural gamma curve to measure the casing wall thickness variation of the wellbore, using the acoustic travel time curve to detect the cement sheath cementation quality and whether channeling exists in the wellbore, and using the image acquisition device to observe the surface morphology of the wellbore; in response to the resistivity curve, the natural gamma curve, the acoustic travel time curve and the surface morphology of the wellbore all meeting the preset requirements, it is determined that the wellbore integrity meets the preset requirements, otherwise it is determined that the wellbore integrity does not meet the preset requirements.

[0014] The formation reserve evaluation includes: performing formation reserve evaluation based on the volumetric method, calculating the reserve by reservoir geometric volume, porosity and fluid saturation, i.e. reserve = reservoir geometric volume x porosity x fluid saturation; in response to the formation reserve being not less than a preset threshold, it is determined that the formation reserve meets the preset requirements, otherwise it is determined that the formation reserve does not meet the preset requirements.

[0015] The remaining production evaluation includes: evaluating the remaining production based on the fracturing operation curve, in response to the remaining production being not less than a preset threshold, it is determined that the remaining production meets the preset requirements, otherwise it is determined that the remaining production does not meet the preset requirements.

[0016] Further, after obtaining the evaluation results of the wellbore integrity, the formation reserve and the remaining production, the wellbore integrity, the formation reserve and the remaining production are judged one by one, and the scores of the repeated reconstruction potential of each section are sorted according to the average values of the three indexes to obtain the position of the repeated reconstruction section; the scores of all well sections with repeated reconstruction potential are added to calculate the average, and the repeated reconstruction potential of the whole wellbore is determined.

[0017] Further, the repeated reconstruction of the well section with repeated reconstruction potential of the target wellbore by the hydraulic pulse deblocking device includes: ground equipment arrangement: arranging the coiled tubing pressure operation system and the fracturing pump truck, cleaning the wellbore and detecting the wellbore integrity; installing the hydraulic pulse tool: installing the hydraulic pulse tool and the positioning and setting pipe column, sending the positioning and setting pipe column into the set position under pressure, and realizing the upper and lower setting of the closed environment by the pulse tool; pulse hydraulic injection deblocking: setting a positive pressure difference in the annulus, and pulse hydraulic injection deblocking.

[0018] Further, the process parameters of pulse hydraulic injection deblocking include: the pulse frequency is set to 0.05-50Hz, the pulse pressure is set to 0.01-120MPa, the pulse waveform is sine or rectangular wave, the displacement is set to 0.01-2m 3 / min; the action time is set to 10-20min.

[0019] Further, in response to the completion of the repeated reconstruction of the shale gas fracturing well, the fracturing operation is carried out for exploitation, and the repeated reconstruction potential of the shale gas fracturing well is evaluated again. If the shale gas fracturing well has the reconstruction potential, the wellbore is continuously reconstructed until the evaluation is that the reconstruction potential is not available.

[0020] The present application has the following unexpected beneficial effects: the present application can dynamically determine whether the repeated reconstruction of the shale gas fracturing well is completed by collecting the pulse pressure curve of the hydraulic pulse deblocking device in real time and according to the waveform change of the pulse pressure curve, and can evaluate the completion degree of the repeated reconstruction of the shale gas fracturing well in real time, so that the repeated reconstruction process of the shale gas fracturing well is efficient, real-time and continuous, the shale gas resources are fully developed and utilized, the gas well production capacity is maximized, and the resource recovery rate is improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A flowchart of the shale gas fracturing well repeated reconstruction dynamic evaluation method is shown.

[0022] Figure 2 A flowchart of the pulse pressure curve waveform determination method is shown.

[0023] Figure 3 A flowchart of the peak value determination method of the pulse pressure curve is shown. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described below with reference to the accompanying drawings and preferred embodiments, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure herein. The present application can also be implemented or applied by different specific embodiments, and various modifications or changes can be made to the details in the specification based on different views and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, but not for limiting the protection scope of the present application.

[0025] In an embodiment, referring to FIG. 1, Figure 1 The present application provides a shale gas fracturing well repeated reconstruction dynamic evaluation method, which comprises: using a hydraulic pulse deblocking device to reconstruct a well section of a target wellbore which has a repeated reconstruction potential, and collecting a pulse pressure curve of the hydraulic pulse deblocking device in real time; in response to the pulse pressure curve waveform changing from a first waveform to a second waveform, determining that the repeated reconstruction of the shale gas fracturing well is completed, and otherwise determining that the repeated reconstruction of the shale gas fracturing well is not completed. Exemplarily, the first waveform is an irregular sine wave, and the second waveform is a regular sine wave.

[0026] The evaluation method uses the change of the pulse pressure curve waveform of the hydraulic pulse deblocking device in the repeated reconstruction of the shale gas fracturing well to determine whether the reconstruction is completed, the abscissa of the pulse pressure curve is time, and the ordinate is the hydraulic pulse pressure of the hydraulic pulse deblocking device. In the initial stage, when there is a need for reconstruction such as plugging in the shale gas well section, the pulse pressure curve presents a first waveform, that is, an irregular sine wave, which means that the fluid flow state, the formation stress condition and the like are in a relatively complex and unstable state, which may be caused by the irregular pressure transmission due to the plugging of the formation pore, the closure of the original fracture or the poor fluid seepage channel. With the continuous action of the hydraulic pulse deblocking device, the formation is deblocked, the new fracture is opened, and the seepage channel is optimized, and when the pulse pressure curve waveform changes to a second waveform (such as a regular sine wave), it is indicated that the pressure transmission in the well becomes regular and stable, the fluid flow state in the formation tends to be stable, and the problems of hindering fluid flow and affecting the gas well productivity are effectively solved, so it is determined that the repeated reconstruction of the shale gas fracturing well is completed; otherwise, if the waveform does not change to a regular state, it is determined that the reconstruction has not been completed, which means that the reconstruction operation needs to be continued to further optimize the formation condition.

[0027] The present application can master the downhole condition at any time during the reconstruction by collecting the pulse pressure curve in real time, and the operator can make a decision in time according to the change of the waveform. For example, if the waveform has not changed for a long time, the working parameters of the hydraulic pulse deblocking device, such as pulse frequency and pressure, can be adjusted in time to better adapt to the formation condition, improve the reconstruction efficiency, and avoid invalid operation and resource waste. Moreover, the present application focuses on the well section with potential for repeated reconstruction, avoids indiscriminate operation on the entire wellbore, accurately processes the key parts that may improve the gas well productivity, and uses the change of the pulse pressure curve waveform as an objective evaluation standard, so that the evaluation result is more scientific and targeted, which helps to accurately tap the productivity potential of the shale gas well and improve the shale gas production.

[0028] In a preferred embodiment, referring to FIG. 1, Figure 2 The judgment method of the pulse pressure curve waveform is as follows: three peak values P1, P2 and P3 near the end of the pulse pressure curve and the time points t1, t2 and t3 corresponding to the three peak values are obtained, in response to P1=P2=P3 and t3-t2=t2-t1, it is determined that the pulse pressure curve waveform is the second waveform, that is, the regular sine wave, indicating that the repeated reconstruction is completed, the process is stopped, otherwise, it is determined that the pulse pressure curve waveform is the first waveform, that is, the irregular sine wave, indicating that the repeated reconstruction is not completed, the hydraulic pulse deblocking is continued, and the pulse pressure curve data is continuously collected for judgment.

[0029] For regular sine wave, its characteristics are periodicity and equal amplitude. When P1 = P2 = P3, it means that the amplitude of the waveform is equal, satisfying the equal amplitude; when t3-t2 = t2-t1, it means that the waveform is equally spaced in time, satisfying the periodicity. Only when both conditions are met, the pulse pressure curve waveform can be determined as a regular sine wave (second waveform), otherwise, the pulse pressure curve waveform is determined as an irregular sine wave (first waveform).

[0030] Further, referring to Figure 3 As shown, the peak value determination method of the pulse pressure curve is: setting a pressure threshold P n for the pulse pressure curve, capturing the pressure values of each point on the pulse pressure curve, setting the pressure value of a certain time point as P m , the pressure value of the left adjacent point as P m-1 , and the pressure value of the right adjacent point as P m+1 . When P m-1 <P m <P m+1 and P m ≥P n are met at the same time, it is determined that the pulse pressure curve reaches the peak value.

[0031] In a preferred embodiment, the well section with repeated reconstruction potential of the target wellbore is determined according to the early logging curve and the fracturing operation curve of the target wellbore; the logging curve includes resistivity curve, acoustic time difference curve, density curve, porosity curve and natural gamma curve; the fracturing operation curve includes operation pressure curve, displacement curve, sand ratio curve, net pressure curve and microseismic monitoring curve.

[0032] The resistivity curve is obtained by resistivity logging, which is a method of measuring the resistivity of rock (including fluid therein) by using power supply electrodes and measurement electrodes arranged at different positions in the borehole based on electrical principles.

[0033] When the power supply electrodes in the borehole apply current, the current will form an electric field in the surrounding rock medium. Due to the different electrical conductivity of different rocks and fluids therein, according to Ohm's law, the voltage and current are measured by the measurement electrode, and the resistivity of the rock is calculated.

[0034] For example, for good conductive rocks (such as sandstone containing a large amount of formation water), the voltage measured by the measurement electrode is relatively low under the same current intensity, and the calculated resistivity is also low; while for poor conductive rocks (such as dense limestone or oil-bearing sandstone), the voltage is higher under the same current, and the resistivity is higher.

[0035] Generally, there are various forms of arrangements of the power supply electrodes and the measuring electrodes. In a conventional resistivity logging, the electrodes are arranged along the well axis, and there are various ways of power supply and measurement, such as single-electrode power supply-single-electrode measurement, double-electrode power supply-double-electrode measurement, etc. For example, the single-electrode power supply-single-electrode measurement is to supply power with one electrode in the well and measure the electric field intensity with another electrode. This arrangement is simple, but is easily disturbed by the environment around the wellbore.

[0036] Acoustic traveltime curve is a logging curve reflecting formation characteristics by measuring the travel time of acoustic wave in the formation. During logging, the downhole instrument emits acoustic wave pulse, which propagates in the rock and the fluid therein, and is then received by the receiving device. The instrument records the time difference between the emission and the reception of the acoustic wave, and then calculates the acoustic traveltime per unit length of the formation. For example, in dense rock, the acoustic wave propagates fast, and the acoustic traveltime is small; while in rock with larger porosity, the acoustic wave propagates slowly due to the more complex propagation path in the rock particles and the pore fluid, and the acoustic traveltime is large.

[0037] Logging density curve is obtained by measuring the interaction between gamma rays and the formation. The logging instrument usually contains a gamma ray source and a detector. The gamma ray source emits gamma rays to the formation of the well wall, and the gamma rays are scattered by the electrons in the formation according to the principle of Compton scattering. The energy of the scattered gamma rays is reduced, and the intensity of the scattered gamma rays is measured by the detector. The higher the density of the formation, the more the number of electrons per unit volume, and the greater the probability of scattering of the gamma rays, and the lower the intensity of the scattered gamma rays received by the detector. Through preset calibration and calculation, the received gamma ray intensity can be converted into the formation density, and then the density curve is obtained.

[0038] Porosity curve is obtained indirectly based on various physical principles, and is used to reflect the size of the formation porosity. For example, according to the Wylie time-average formula , the porosity is calculated, in which v is the acoustic wave velocity in the rock, v f is the acoustic wave velocity in the pore fluid, v m is the acoustic wave velocity of the rock skeleton, and φ is the porosity. Or the porosity is calculated by the formula , in which ρ b is the formation density, is the porosity, ρ m is the rock skeleton density, and ρ f is the pore fluid density.

[0039] Natural gamma ray logging is a method of measuring the natural radioactivity intensity of the formation. Radioactive elements in the formation, such as potassium-40, uranium-238, and thorium-232 decay series, emit gamma rays. A gamma ray detector in the logging instrument measures the intensity of these naturally emitted gamma rays, resulting in a natural gamma ray curve. Different formations contain different types and amounts of radioactive elements, leading to different natural gamma ray intensities.

[0040] The treatment pressure curve records the change of wellhead pressure over time during the fracturing treatment. In fracturing operations, high-pressure liquid is injected into the well to break the formation rock and create fractures. Treatment pressure is mainly affected by factors such as the flow rate of injected liquid, the stress state of the formation, the mechanical properties of the rock, and the expansion of the fracture. For example, when the flow rate of injected liquid increases, the treatment pressure usually rises; when the formation rock begins to break and form a fracture, the treatment pressure will show a significant drop, because the formation of the fracture provides a new flow path for the liquid, and the pressure is released.

[0041] The flow rate curve reflects the change in the flow rate of injected liquid over time during the fracturing treatment. The flow rate is adjusted by controlling the operating state of surface equipment such as fracturing pumps. The size of the flow rate directly affects the speed and range of fracture expansion. Higher flow rates can provide more energy to promote faster extension and expansion of the fracture, but at the same time, they can also bring higher pressure to the formation and equipment.

[0042] The sand concentration curve shows the change in the concentration of proppant (sand) in the fracturing fluid over time. The role of proppant is to form support in the fracture formed by fracturing, preventing the closure of the fracture, and thus maintaining the permeability of the formation. The size of the sand concentration is determined according to factors such as the properties of the formation and the width of the fracture. In the early stage of treatment, low-sand liquid may be injected first to prop open the fracture, and as the fracture gradually stabilizes and expands, the sand concentration is gradually increased to fill the fracture.

[0043] Net pressure is the difference between bottom hole pressure and the minimum principal stress of the formation, and the net pressure curve reflects the change of this difference over time. Net pressure has a key influence on the behavior of fracture initiation, extension, and diversion. When the net pressure reaches the rock's fracture pressure, the formation rock begins to break; during the extension of the fracture, the size of the net pressure determines the direction and shape of the fracture expansion.

[0044] Microseismic monitoring is achieved by placing seismic detectors around the well or on the ground to monitor the microseismic events caused by rock rupture during fracturing. The microseismic monitoring curve records information such as the energy, frequency, occurrence time, and location of these microseismic events. When the fracturing fluid props open the formation rock to form a fracture, the rock rupture will produce microseismic signals, which can be monitored and analyzed.

[0045] In a preferred embodiment, determining the well section of the target wellbore that has the repeated reformation potential specifically comprises: dividing the target wellbore into a plurality of well sections according to a preset length, evaluating whether the well section meets preset requirements in terms of wellbore integrity, formation reserves, and remaining production, and determining that the well section has the repeated reformation potential in response to the wellbore integrity, the formation reserves, and the remaining production all meeting the preset requirements, or determining that the well section does not have the repeated reformation potential otherwise. In this way, those well sections in the target wellbore that are suitable for repeated reformation can be screened out more scientifically and systematically, thereby providing a basis for subsequent related reformation decision and engineering implementation.

[0046] The present application determines whether the wellbore meets preset integrity requirements by using a plurality of different measurement methods and curve analysis from multiple dimensions. Specifically, the wellbore integrity evaluation comprises:

[0047] The resistivity curve is used to determine whether there is corrosion or cracks in the casing wall of the wellbore. Resistivity is an electrical property of a material. Different materials and different internal structural states of the materials (such as changes in medium caused by corrosion or cracks) will result in different values or change rules of resistivity. By analyzing the change characteristics of the resistivity curve, professionals can infer whether corrosion has occurred in the casing wall or whether cracks have been generated, which serves as an important basis for evaluating the integrity of the wellbore.

[0048] The natural gamma curve is used to measure the casing wall thickness variation of the wellbore. The intensity of natural gamma rays is related to the radioactivity of the formation rock and the casing and other materials. Changes in the casing wall thickness will affect the absorption and attenuation of natural gamma rays, which will be reflected on the natural gamma curve. By accurately measuring and analyzing the curve, the change information of the casing wall thickness can be obtained. If the casing wall thickness changes abnormally, it may mean that the integrity of the wellbore is affected, such as local damage.

[0049] The acoustic travel time curve is used to detect the cementing quality of the cement sheath of the wellbore and whether there is channeling. The speed of sound propagation in different media is not the same, and the acoustic travel time will have obvious differences when the sound propagates in the cement sheath with good cementing quality and channeling. By monitoring and analyzing the acoustic travel time curve, the cementing quality of the cement sheath can be accurately determined. If there is channeling or other adverse conditions, the acoustic travel time curve will show corresponding characteristic changes, thereby helping to determine the integrity of the wellbore in this regard.

[0050] The image acquisition device is used to observe the surface morphology of the wellbore. This method is the most intuitive and can clearly see whether there are visible abnormal conditions such as pits, damage, deformation, and other visible abnormal conditions on the surface of the wellbore, thereby providing intuitive image evidence for evaluating the integrity of the wellbore.

[0051] If the resistivity curve, the natural gamma ray curve, the acoustic travel time curve and the wellbore surface profile all meet the preset requirements, it is determined that the wellbore integrity meets the preset requirements, otherwise, if any of the indicators does not meet the preset requirements, it is determined that the wellbore integrity does not meet the preset requirements.

[0052] By such a comprehensive and multi-dimensional evaluation method and strict judgment logic, the integrity condition of the wellbore can be accurately measured, and key basic data support is provided for subsequent determination of whether the well section has the potential for repeated reconstruction and other related decisions.

[0053] The formation reserve evaluation includes: performing formation reserve evaluation based on the volumetric method, and calculating the reserve by reservoir geometric volume, porosity and fluid saturation, that is, reserve = reservoir geometric volume x porosity x fluid saturation.

[0054] The volumetric method is a classic method commonly used in the field of petroleum geology to calculate the formation reserve. The basic idea is to regard the reservoir as a container with a certain geometric shape, and to determine the recoverable reserve contained therein by analyzing the key elements of reservoir geometric volume, porosity and fluid saturation. Simply put, the reservoir geometric volume determines the size range of the entire "container", the porosity reflects the proportion of the space inside the reservoir rock available for fluid storage, and the fluid saturation reflects the degree to which these pore spaces are occupied by fluids such as oil and gas. Multiplying these three elements together can roughly estimate the reserve contained in the formation.

[0055] Reservoir geometric volume: This needs to be determined by geological exploration, well logging and other means to determine the distribution range and approximate shape of the reservoir underground, and then calculate the corresponding volume value. For example, for layered reservoirs, the volume can be accurately calculated according to the lateral extension range and vertical thickness; for irregularly shaped reservoirs, more complex geological modeling methods may be needed to reasonably estimate the volume.

[0056] Porosity: is an important indicator of rock storage performance, usually obtained through laboratory core analysis, well logging interpretation and other methods. It represents the ratio of pore volume to total rock volume. Different types of rocks, different sedimentary environments and other factors can cause large differences in porosity, and the size of porosity directly affects how much fluid can be contained in the formation.

[0057] Fluid saturation: mainly reflects the proportion of oil and gas fluids in the pore space, which is usually determined by special logging techniques and reservoir engineering analysis. For example, in a reservoir, oil saturation is the proportion of oil in the pore volume, which, together with water saturation and other indicators, constitutes the fluid saturation index, which plays a key role in accurately calculating the formation reserve.

[0058] When the formation reserves calculated according to the volume method are not lower than the preset threshold value, it is determined that the formation reserves meet the preset requirement, which means that the well section has certain exploitation value and potential for repeated reconstruction from the perspective of reserves; otherwise, if the calculated formation reserves are lower than the preset threshold value, it is determined that the formation reserves do not meet the preset requirement, which means that the exploitable resources in the formation are relatively limited, and thus the economic benefits and other factors need to be carefully weighed when considering the repeated reconstruction of the well section.

[0059] The remaining production evaluation includes: evaluating the remaining production based on the fracturing operation curve, and determining that the remaining production meets the preset requirement in response to the remaining production being not lower than a preset threshold value, and determining that the remaining production does not meet the preset requirement otherwise.

[0060] The fracturing operation curve is a kind of curve chart recorded in the process of fracturing operation of oil wells, gas wells and the like, which can reflect a plurality of key information. It usually contains the changes of construction time, construction pressure, injected liquid volume, sand volume and the like with time. The changes of these parameters are closely related to the characteristics of the formation, the expansion of the fracture and the final production performance and the like. By deeply analyzing the fracturing operation curve, the current seepage capacity of the formation, the production performance corresponding to the remaining recoverable reserves and the like can be indirectly inferred. For example, the change trend of the construction pressure can reflect the opening and extension of the formation fracture, and the injected liquid volume, sand volume and the like are related to the scale of the effective fracture network formed, thereby affecting the subsequent fluid production performance, that is, the production performance.

[0061] In a preferred embodiment, after obtaining the evaluation results of the wellbore integrity, the formation reserves and the remaining production, the wellbore integrity, the formation reserves and the remaining production are judged one by one, and the repeated reconstruction potential of each section is scored and sorted according to the average value of the three indexes to obtain the position of the repeated reconstruction section; the scores of all well sections with repeated reconstruction potential are added to calculate the average, and the repeated reconstruction potential of the whole wellbore is determined.

[0062] For example, the evaluation results of the wellbore integrity, the formation reserves and the remaining production of a well section of a wellbore are shown in Table 1.

[0063] Serial number Wellbore integrity Reservoir Remaining production Average value A1 A1x A1y A1z A1 ave ]]> A2 A2x A2y A2z [A2 ave ]] A3 A3x A3y A3z A3 ave ]] …… …… …… …… …… An Anx Any Anz An ave ]]

[0064] In the table, A1x, A2x, A3x,..., Anx respectively correspond to the wellbore integrity evaluation scores of A1 well section, A2 well section, A3 well section,..., An well section, A1y, A2y, A3y,..., Any respectively correspond to the formation reserves evaluation scores of A1 well section, A2 well section, A3 well section,..., An well section, A1z, A2z, A3z,..., Anz respectively correspond to the remaining production evaluation scores of A1 well section, A2 well section, A3 well section,..., An well section, and A1ave 、A2 ave 、A3 ave ...An ave The summed average values ​​of the wellbore integrity assessment scores, formation reserve assessment scores, and remaining production assessment scores corresponding to well sections A1, A2, A3, ..., and An, respectively.

[0065] When judging the potential for repeated transformation, the wellbore integrity, formation reserves, and remaining production are first judged one by one, that is, the wellbore integrity assessment score, formation reserve assessment score, and remaining production assessment score of a certain well section are judged one by one to see whether they meet the preset requirements. In response to the wellbore integrity assessment score, formation reserve assessment score, and remaining production assessment score all meeting the preset requirements, it is determined that the well section has the potential for repeated transformation; otherwise, it is determined that the well section does not have the potential for repeated transformation.

[0066] After the evaluation of all sections of the wellbore is completed, the sequence number of the sections with the potential for repeated transformation can be obtained.

[0067] The summed evaluation values ​​of the assessment scores of the well sections with the potential for repeated transformation are added together to calculate the average score to obtain the transformation potential score of the wellbore. The transformation potential score of the wellbore is compared with a preset threshold to determine whether the wellbore as a whole has the potential for repeated transformation.

[0068] In a preferred embodiment, the method of repeatedly reforming a target wellbore section with repeat reforming potential by using a hydraulic pulse unblocking device comprises:

[0069] Step 1: Arrangement of ground equipment: Arrangement of the continuous tubing pressure operation system and the fracturing pump truck. The continuous tubing pressure operation system includes a continuous tubing truck, an injection head, a blowout preventer (BOP) system, a control system, and a power unit. The continuous tubing pressure operation system enables various downhole operations to be performed while the wellbore is under pressure, and has the advantages of high operating efficiency and minimal damage to the formation. The fracturing pump truck provides a powerful power source for subsequent hydraulic pulse injection, including a high-pressure pump, a hydraulic drive system, a control system, and sand mixing equipment. The fluid is injected into the wellbore at a relatively high pressure through the fracturing pump truck. The two work together to build a basic ground equipment guarantee for the entire transformation operation.

[0070] Before formally carrying out the plugging removal and reconstruction, it is necessary to clean the wellbore first. Various impurities, sediments and the like may exist in the wellbore, and cleaning the wellbore can remove these obstacles affecting subsequent operations and fluid flow, and ensure that the internal environment of the wellbore is relatively clean. At the same time, detecting the integrity of the wellbore can again confirm the structural condition of the wellbore, such as whether the casing is intact, whether the cementing quality of the cement sheath meets the requirements, and the like, so as to avoid accidents due to hidden dangers in the wellbore during subsequent operations, and provide a basis for the safe and smooth performance of the reconstruction operation. Specifically, a suitable cleaning fluid is selected, a pipeline pump is pressurized to inject, and the cleaning fluid is ensured to circulate fully in the wellbore to remove the blockage. After cleaning, a downhole endoscopic camera device is used to be sent into the wellbore to observe the condition of the inner wall of the wellbore in real time.

[0071] Step two, installation of hydraulic pulse tool: install the hydraulic pulse tool and the positioning and setting pipe string, send the positioning and setting pipe string into the set position under pressure, and realize the up and down setting and sealing of the closed environment through the pulse tool. Connect the hydraulic pulse tool with one end of the oil pipe, and connect the other end of the oil pipe with the fracturing pump truck. Start the drum device of the coiled tubing truck, send the coiled tubing into the wellbore, and lower it according to the predetermined depth and position. When the positioning and setting pipe string is lowered to the predetermined plugging position, stop the lowering operation of the coiled tubing, and use the positioning tool to confirm the specific position of the pipe string.

[0072] The hydraulic pulse tool can generate a specific hydraulic pulse, and use the energy of the pulse to destroy the structure of the plugging in the formation and improve the seepage performance of the formation. The positioning and setting pipe string plays the role of accurate positioning and setting and sealing at a specific position downhole to build a closed environment. The two are installed together to ensure that the hydraulic pulse tool can be accurately placed at the set position where the plugging removal is needed, and to create good closed conditions for the subsequent pulse action.

[0073] When the positioning and setting pipe string reaches the specified position, the hydraulic pulse tool is operated to realize the up and down setting, so as to form a relatively closed environment downhole, so that the subsequently injected pulse water can fully play a role in this limited space and concentrate the power to remove the plugging of the surrounding formation.

[0074] Step three, pulse water injection for plugging removal: set the positive pressure difference in the annulus, and inject pulse water for plugging removal. Specifically, inject the balancing fluid into the wellbore to stabilize the pressure, and inject the balancing fluid or adjust the fluid column height in the annulus to form the required positive pressure difference. Real-time monitoring of the pressure changes inside and outside the wellbore is realized by using the pressure sensor, the pressure control valve of the injection head is adjusted by the ground control system, the pressure difference is ensured to be stable, and the whole process is operated under pressure, which can effectively control the sand return of the formation.

[0075] The present application can guide the pulse water force to flow in the formation in the expected direction and strength by reasonably controlling the pressure difference of the annulus, so that the energy of the water force pulse can better act on the blockage, and the blockage removal effect is enhanced. For example, a suitable positive pressure difference can promote the pulse water force to more effectively impact the blockage particles, colloid and other substances in the formation pores, so as to promote them to be loose, dispersed and then carried out of the formation by the fluid.

[0076] The present application uses the ground equipment such as the fracturing pump truck to inject the fluid into the wellbore in the form of pulse and act on the formation, and by means of the energy such as high-frequency vibration and impact generated by the water force pulse, the original blockage structure in the formation is destroyed, such as the rock debris blocking the pores, the colloid asphalt adhering to the pore wall and other substances are broken and diluted, the seepage channel of the formation is restored, the permeability of the formation is improved, and finally the blockage is removed and the production potential of the well section is improved.

[0077] Further, the process parameter setting of the pulse water force injection blockage removal includes that the pulse frequency is set to 0.05-50Hz, the pulse pressure is set to 0.01-120MPa, the pulse waveform is sine or rectangular wave, the displacement is set to 0.01-2m 3 / min; and the action time is set to 10-20min.

[0078] In a preferred embodiment, after the completion of the repeated reconstruction of the shale gas fracturing well, the fracturing operation is carried out for exploitation, and the repeated reconstruction potential of the shale gas fracturing well is re-evaluated. If the shale gas fracturing well has reconstruction potential, the wellbore is continuously reconstructed, aiming to optimize the seepage performance of the formation, increase the production and the like by further measures. The re-reconstruction process also follows the corresponding reconstruction process and technical requirements, and after the completion, the next round of repeated reconstruction potential evaluation is carried out again based on the new fracturing operation curve. The cycle is repeated until the evaluation result shows that the wellbore has no reconstruction potential, which means that at this time, from the aspects of technology, economy and the like, the reconstruction cannot obtain considerable benefits or cannot effectively improve the production condition.

[0079] The above examples are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. The equivalent substitutions or transformations made by the person skilled in the art on the basis of the present application are within the protection scope of the present application.

Claims

1. A method for dynamic evaluation of repeated reformation of shale gas fracturing wells, characterized in that, The method comprises the following steps: repeatedly transforming the well section of the target wellbore which has the potential for repeated transformation by using a hydraulic pulse deblocking device, and collecting the pulse pressure curve of the hydraulic pulse deblocking device in real time; in response to the pulse pressure curve waveform changing from a first waveform to a second waveform, determining that the repeated transformation of the shale gas fracturing well is completed, otherwise determining that the repeated transformation of the shale gas fracturing well is not completed; the first waveform is an irregular sine wave, and the second waveform is a regular sine wave; determining the well section of the target wellbore which has the potential for repeated transformation according to the previous logging curve and fracturing operation curve of the target wellbore; the logging curve comprises resistivity curve, acoustic travel time curve, density curve, porosity curve and natural gamma curve; the fracturing operation curve comprises operation pressure curve, displacement curve, sand ratio curve, net pressure curve and microseismic monitoring curve; determining the well section of the target wellbore which has the potential for repeated transformation specifically comprises: dividing the target wellbore into several well sections according to the preset length, evaluating whether the wellbore integrity, formation reserves and remaining production of the well section meet the preset requirements, and in response to the wellbore integrity, formation reserves and remaining production all meeting the preset requirements, determining that the well section has the potential for repeated transformation, otherwise determining that the well section does not have the potential for repeated transformation; the wellbore integrity evaluation comprises: using the resistivity curve to determine whether there is corrosion and cracks in the casing wall of the wellbore, using the natural gamma curve to measure the casing wall thickness change of the wellbore, using the acoustic travel time curve to detect the cementing quality of the wellbore and whether there is channeling, and using the image acquisition equipment to observe the surface morphology of the wellbore; in response to the resistivity curve, the natural gamma curve, the acoustic travel time curve and the surface morphology of the wellbore all meeting the preset requirements, it is determined that the wellbore integrity meets the preset requirements, otherwise it is determined that the wellbore integrity does not meet the preset requirements; the formation reserves evaluation comprises: evaluating the formation reserves based on the volume method, and calculating the reserves by reservoir geometric volume, porosity and fluid saturation, i.e. reserves = reservoir geometric volume × porosity × fluid saturation; in response to the formation reserves being not less than the preset threshold, it is determined that the formation reserves meet the preset requirements, otherwise it is determined that the formation reserves do not meet the preset requirements; the remaining production evaluation comprises: evaluating the remaining production based on the fracturing operation curve, and in response to the remaining production being not less than the preset threshold, it is determined that the remaining production meets the preset requirements, otherwise it is determined that the remaining production does not meet the preset requirements; after obtaining the evaluation results of the wellbore integrity, formation reserves and remaining production, the wellbore integrity, formation reserves and remaining production are judged one by one, and the repeated transformation potential of each section is scored and sorted according to the average value of the three indexes to obtain the position of the repeated transformation section; adding up the scores of all well sections which have the potential for repeated transformation to calculate the average, and determining the repeated transformation potential of the whole wellbore.

2. The method of claim 1, wherein, The judgment method of the pulse pressure curve waveform is: obtaining three peak values near the end of the pulse pressure curve P 1、 P 2、 P 3 and the time points corresponding to the three peak values respectively t 1、 t 2、 t 3, in response to P 1= P 2= P 3, and t 3- t 2= t 2- t 1, determining that the pulse pressure curve waveform is the second waveform, that is, a regular sine wave, and otherwise determining that the pulse pressure curve waveform is the first waveform, that is, an irregular sine wave.

3. The method of claim 1, wherein: the repeated transformation of the well section of the target wellbore which has the potential for repeated transformation by using the hydraulic pulse deblocking device comprises: ground equipment arrangement: arranging the coiled tubing pressure operation system and fracturing pump truck, cleaning the wellbore and detecting the wellbore integrity; Hydraulic pulse tool is installed: install hydraulic pulse tool and positioning and setting pipe column, and send the positioning and setting pipe column to the set position under pressure, and realize the up and down setting and sealing of the closed environment through the pulse tool; Pulse hydraulic injection deblocking: annulus is set to a positive pressure difference, and pulse hydraulic injection deblocking is performed.

4. The method of claim 3, wherein, The process parameter setting of the pulse hydraulic injection plugging solution includes: pulse frequency setting is 0.05~50Hz, pulse pressure setting is 0.01~120MPa, pulse waveform is sine, displacement setting is 0.01~2m 3 / min; action time setting is 10~20min.

5. The method of claim 1, wherein: After the completion of the repeated reconstruction of the shale gas fracturing well, the fracturing operation is performed for exploitation, and the repeated reconstruction potential of the shale gas fracturing well is evaluated again. If the shale gas fracturing well has reconstruction potential, the wellbore is continuously reconstructed until it is evaluated as not having reconstruction potential.

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