In this paper,a viscoelasticity-plastic damage constitutive equation for naturally fractured shale is deduced,coupling nonlinear tensile-shear mixed fracture mode.Dynamic perforation-erosion on fluid re-distribution a...In this paper,a viscoelasticity-plastic damage constitutive equation for naturally fractured shale is deduced,coupling nonlinear tensile-shear mixed fracture mode.Dynamic perforation-erosion on fluid re-distribution among multi-clusters are considered as well.DFN-FEM(discrete fracture network combined with finite element method)was developed to simulate the multi-cluster complex fractures propagation within temporary plugging fracturing(TPF).Numerical results are matched with field injection and micro-seismic monitoring data.Based on geomechanical characteristics of Weiyuan deep shale gas reservoir in Sichuan Basin,SW China,a multi-cluster complex fractures propagation model is built for TPF.To study complex fractures propagation and the permeability-enhanced region evolution,intersecting and competition mechanisms between the fractures before and after TPF treatment are revealed.Simulation results show that:fracture from middle cluster is restricted by the fractures from side-clusters,and side-clusters plugging is benefit for multi fractures propagation in uniformity;optimized TPF timing should be delayed within a higher density or strike of natural fractures;Within a reservoir-featured natural fractures distribution,optimized TPF timing for most clustered method is 2/3 of total fluid injection time as the optimal plugging time under different clustering modes.展开更多
This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion w...This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion with multi-cluster sand jetting perforation.The effects of temporary plugging agent(TPA)particle size,TPA concentration,single-cluster perforation number and cluster number on plugging pressure,multi-fracture diversion pattern and distribution of TPAs were investigated.A combination of TPAs with small particle sizes within the fracture and large particle sizes within the segment is conducive to increasing the plugging pressure and promoting the diversion of multi-fractures.The addition of fibers can quickly achieve ultra-high pressure,but it may lead to longitudinal fractures extending along the wellbore.The temporary plugging peak pressure increases with an increase in the concentration of the TPA,reaching a peak at a certain concentration,and further increases do not significantly improve the temporary plugging peak pressure.The breaking pressure and temporary plugging peak pressure show a decreasing trend with an increase in single-cluster perforation number.A lower number of single-cluster perforations is beneficial for increasing the breaking pressure and temporary plugging peak pressure,and it has a more significant control on the propagation of multi-cluster fractures.A lower number of clusters is not conducive to increasing the total number and complexity of artificial fractures,while a higher number of clusters makes it difficult to achieve effective plugging.The TPAs within the fracture is mainly concentrated in the complex fracture areas,especially at the intersections of fractures.Meanwhile,the TPAs within the segment are primarily distributed near the perforation cluster apertures which initiated complex fractures.展开更多
When deep and ultra-deep shale gas well fracturing is carried out,multi-cluster fracturing can hardly realize synchronous initiation and propagation of hydraulic fractures due to the combined effects of heterogeneity ...When deep and ultra-deep shale gas well fracturing is carried out,multi-cluster fracturing can hardly realize synchronous initiation and propagation of hydraulic fractures due to the combined effects of heterogeneity of deep in-situ stress and"dense cluster"fracture arrangement,and the strong interference between fractures aggravates the unbalanced fracture propagation degree.Field practice proves that the fracture-opening temporary plugging fracturing technology can effectively control the unbalanced propagation of multiple fractures.In addition,the application effect of temporary plugging process can be improved by developing a method for simulating fracture control during fracture-opening temporary plugging fracturing of deep/ultra-deep shale-gas horizontal wells.Based on rock mechanics,elasticity mechanics,fluid mechanics and fracture propagation theory,combined with the flow distribution equation of horizontal-well multi-cluster fracturing and the plugging equation of temporary plugging balls,this paper establishes a fracture propagation model and a fracture control simulation method for the fracture-opening temporary plugging fracturing of deep/ultra-deep shale gas horizontal wells.Then,the influences of the number of temporary plugging balls and the times and timing of temporary plugging on temporary plugging control are simulated,and the influences of temporary plugging balls on fracture propagation morphology and SRV(stimulated reservoir volume)distribution are analyzed by taking Sinopec's one deep shale gas well in Dingshan-Dongxi structure of southeast Sichuan Basin as an example.And the following research results are obtained.First,fracture-opening temporary plugging can significantly promote the balanced propagation of multiple fractures,and the simulation confirms that the number of temporary plugging balls and the times and timing of temporary plugging play an important role in fracture control.Second,as the number of temporary plugging balls increase,the SRV increases firstly and then decreases,so there is an optimal number of temporary plugging balls.Third,increasing the times of temporary plugging can improve the fault tolerance rate of temporary plugging and diverting process,but it is necessary to increase the number of temporary plugging balls appropriately.Fourth,when the timing of temporary plugging is appropriate,the balanced propagation of multiple fractures is achieved and the maximum SRV is reached.In conclusion,this method is of great significance to optimizing the design of temporary plugging fracturing,improve the implementation level of field process and develop deep and ultra-deep shale gas efficiently.展开更多
Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness...Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness of reservoir stimulation. Temporary plugging and diverting fracturing(TPDF) is considered to be a potential uniform-stimulation method for creating multiple fractures simultaneously in the oilfield. However, the multi-fracture propagation morphology during TPDF is not clear now. The purpose of this study is to quantitatively investigate the multi-fracture propagation morphology during TPDF through true tri-axial fracturing experiments and CT scanning. Critical parameters such as fracture spacing, number of perforation clusters, the viscosity of fracturing fluid, and the in-situ stress have been investigated. The fracture geometry before and after diversion have been quantitively analyzed based on the two-dimensional CT slices and three-dimensional reconstruction method. The main conclusions are as follows:(1) When injecting the high viscosity fluid or perforating at the location with low in-situ stress, multiple hydraulic fractures would simultaneously propagate. Otherwise, only one hydraulic fracture was created during the initial fracturing stage(IFS) for most tests.(2) The perforation cluster effectiveness(PCE) has increased from 26.62% during the IFS to 88.86% after using diverters.(3) The diverted fracture volume has no apparent correlation with the pressure peak and peak frequency during the diversion fracturing stage(DFS) but is positively correlated with water-work.(4) Four types of plugging behavior in shale could be controlled by adjusting the diverter recipe and diverter injection time, and the plugging behavior includes plugging the natural fracture in the wellbore, plugging the previous hydraulic fractures, plugging the fracture tip and plugging the bedding.展开更多
Horizontal shale gas well fracturing is mostly carried out by pumping bridge plugs.In the case of casing deformation,the bridge plug can not be pumped down to the designated position,so the hole sections below the def...Horizontal shale gas well fracturing is mostly carried out by pumping bridge plugs.In the case of casing deformation,the bridge plug can not be pumped down to the designated position,so the hole sections below the deformation could not be stimulated according to the design program.About 30%of horizontal shale gas wells in the Changning and Weiyuan Blocks,Sichuan Basin,suffer various casing deformation after fracturing.Previously,the hole sections which could not be stimulated due to casing deformation were generally abandoned.As a result,the resources controlled by shale gas wells weren't exploited effectively and the fracturing effect was impacted greatly.There are a lot of difficulties in investigating casing deformation,such as complex mechanisms,various influencing factors and unpredictable deformation time.Therefore,it is especially important to seek a staged fracturing technology suitable for the casing deformation sections.In this paper,the staged fracturing technology with sand plugs inside fractures and the staged fracturing technology with temporary plugging balls were tested in casing deformation wells.The staged fracturing technology with sand plugs inside fractures was carried out in the mode of single-stage perforation and single-stage fracturing.The staged fracturing technology with temporary plugging balls was conducted in the mode of single perforation,continuous fracturing and staged ball dropping.Then,two kinds of technologies were compared in terms of their advantages and disadvantages.Finally,they were tested on site.According to the pressure response,the pressure monitoring of the adjacent wells and the microseismic monitoring in the process of actual fracturing,both technologies are effective in the stimulation of the casing deformation sections,realizing well control reserves efficiently and guaranteeing fracturing effects.展开更多
Temporary plugging and diverting fracturing(TPDF),involving inner-fracture temporary plugging(IFTP)and inner-stage temporary plugging(ISTP),has been proposed as a widely applied technique in China,for promoting the un...Temporary plugging and diverting fracturing(TPDF),involving inner-fracture temporary plugging(IFTP)and inner-stage temporary plugging(ISTP),has been proposed as a widely applied technique in China,for promoting the uniform initiation and propagation of multi-clustered hydraulic fractures(HFs)in a horizontal well of the shale oil/gas reservoirs.However,how the key plugging parameters controlling the multi-fracture growth and the pumping pressure response during TPDF in shale with dense bedding planes(BPs)and natural fractures(NFs)is still unclear,which limits the optimization of TPDF scheme.In this paper,a series of TPDF simulation experiments within a stage of multi-cluster in a horizontal well were carried out on outcrops of Longmaxi Formation shale using a large-scale true tri-axial fracturing simulation system,combined with the acoustic emission(AE)monitor and computed tomography(CT)scanning techniques.Each experiment was divided into three stages,including the conventional fracturing(CF),IFTP and ISTP.Multi-fracture initiation and propagation behavior,and the dominant controlling parameters were examined,containing the particle sizes,concentration of temporary plugging agent(TPA),and cluster number.The results showed that the number of transverse HFs(THFs)and the overall complexity of fracture morphology increase with the increase in TPA concentration and perforation cluster number.Obviously,the required concentration of TPA is positively correlated with the cluster number.Higher peak values and continuous fluctuations of pumping pressure during TPDF may indicate the creation of diversion fractures.The creation of standard THFs during CF is favorable to the creation of diversion fractures during TPDF.Moreover,the activation of BPs nearby the wellbore during CF is unfavorable to the subsequent pressure buildup during TPDF,resulting in poor plugging and diverting effect.Notably,under the strike-slip fault stress regime,the diversion of THFs is not likely during IFTP,which is similar as the results of ISTP to initiate mainly the un-initiated or under-propagated perforation clusters.Three typical pressure curve types during TPDF can be summarized to briefly identify the hydraulic fracture diversion effects,including good(multiple branches or/and THFs can be newly created),fair(HF initiation along the slightly opened BPs and then activating the NFs),and bad(HF initiation along the largely opened BPs and then connecting with the NFs).展开更多
To solve the problem that the production of Mahu conglomerate reservoir is not up to expectation after the multi-cluster plus temporary plugging fracturing technology is applied in horizontal wells, stages 2–6 in the...To solve the problem that the production of Mahu conglomerate reservoir is not up to expectation after the multi-cluster plus temporary plugging fracturing technology is applied in horizontal wells, stages 2–6 in the test well MaHW6285 are selected to carry out erosion tests with different pumping parameters. The downhole video imaging technology is used to monitor the degree of perforations erosion, and then the fracture initiation and proppant distribution of each cluster are analyzed. The results showed that proppant entered 76.7% of the perforations. The proppant was mainly distributed in a few perforation clusters, and the amount of proppant entered in most of the clusters was limited. The proppant distribution in Stage 4 was relatively uniform, and the fracture initiation of each cluster in the stage is more uniform. The proppant distribution in stages 2, 3, 5, and 6 was significantly uneven, and the uniform degree of fracture initiation in each cluster is low. More than 70% of the proppant dose in the stage entered clusters near the heel end, so the addition of diverters did not promote the uniform initiation of hydraulic fractures. There was a positive correlation between the amount of proppant added and the degree of perforations erosion, and the degree of perforations erosion ranged from 15% to 352%, with an average value of 74.5%, which was far higher than the statistical results of shale reservoir tests in North America. The use of 180° phase perforation(horizontal direction) can reduce the “Phase Bias” of perforations erosion, promote uniform perforations erosion and fluid inflow. The research results provide the basis for optimizing the pumping procedure, reducing the perforation erosion and improving the success rate of diversion.展开更多
With the rapid development of shale gas exploration and development in China,casing deformation in shale gas horizontal wells happens frequently,which directly impacts the development efficiency and benefits of shale ...With the rapid development of shale gas exploration and development in China,casing deformation in shale gas horizontal wells happens frequently,which directly impacts the development efficiency and benefits of shale gas.In order to explore casing deformation prediction,prevention and treatment methods,this paper analyzes the geological and engineering causes of casing deformation in shale-gas horizontal wells through laboratory work,such as the casing resistance to internal pressure alternating test,the ground simulation test and systematical casing deformation characteristic analysis of MIT24 caliper logging,and the large-scale physical simulation test and numerical simulation of casing deformation.Then,combined with the generalized shear activity criterion,a new method for evaluating casing deformation risk points and some technical measures for preventing casing deformation were formulated.And the following research results were obtained.First,the deformation characteristics of 119 casing deformation points in 23 wells interpreted by MIT24 caliper logging are consistent with the mechanical behaviors of shear compression deformation test.Second,the large-scale physical simulation test shows that natural fault-fractures slip obviously under the state of strike-slip stress.Third,numerical simulation shows that the compression stress on casing increases with the increase of fault-fracture slip.When the fault-fracture slip is between 7.5 mm and 9.0 mm,the casing reaches the critical yield strength and begins to undergo plastic deformation.The“temporary fracture plugging+long segment and multi-cluster”and other technologies are field tested in 28 wells in Weiyuan area of southern Sichuan Basin.The casing deformation rate decreases from 54%(before this research)to 14.3%,and the segment loss rate decreases from 7.8%to 0,which reveals remarkable achievements in casing deformation treatment.In conclusion,the shear slip of fault and macro fractures(referred to as fault-fracture)is the main cause of casing deformation in shale gas horizontal wells,and some measures(e.g.“temporary fracture plugging+long segment and multi-cluster”,reducing fracturing scale and releasing wellbore pressure properly)shall be taken in advance to reduce the fault-fracture activity before the risk point of casing deformation is fractured,so as to reach the goal of casing deformation prevention.展开更多
基金Supported by the National Natural Science Foundation of China(52192622,52204005,U20A20265)Sichuan Outstanding Young Scientific and Technological Talents Project(2022JDJQ0007).
文摘In this paper,a viscoelasticity-plastic damage constitutive equation for naturally fractured shale is deduced,coupling nonlinear tensile-shear mixed fracture mode.Dynamic perforation-erosion on fluid re-distribution among multi-clusters are considered as well.DFN-FEM(discrete fracture network combined with finite element method)was developed to simulate the multi-cluster complex fractures propagation within temporary plugging fracturing(TPF).Numerical results are matched with field injection and micro-seismic monitoring data.Based on geomechanical characteristics of Weiyuan deep shale gas reservoir in Sichuan Basin,SW China,a multi-cluster complex fractures propagation model is built for TPF.To study complex fractures propagation and the permeability-enhanced region evolution,intersecting and competition mechanisms between the fractures before and after TPF treatment are revealed.Simulation results show that:fracture from middle cluster is restricted by the fractures from side-clusters,and side-clusters plugging is benefit for multi fractures propagation in uniformity;optimized TPF timing should be delayed within a higher density or strike of natural fractures;Within a reservoir-featured natural fractures distribution,optimized TPF timing for most clustered method is 2/3 of total fluid injection time as the optimal plugging time under different clustering modes.
基金Supported by the National Natural Science Foundation of China(51974332).
文摘This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion with multi-cluster sand jetting perforation.The effects of temporary plugging agent(TPA)particle size,TPA concentration,single-cluster perforation number and cluster number on plugging pressure,multi-fracture diversion pattern and distribution of TPAs were investigated.A combination of TPAs with small particle sizes within the fracture and large particle sizes within the segment is conducive to increasing the plugging pressure and promoting the diversion of multi-fractures.The addition of fibers can quickly achieve ultra-high pressure,but it may lead to longitudinal fractures extending along the wellbore.The temporary plugging peak pressure increases with an increase in the concentration of the TPA,reaching a peak at a certain concentration,and further increases do not significantly improve the temporary plugging peak pressure.The breaking pressure and temporary plugging peak pressure show a decreasing trend with an increase in single-cluster perforation number.A lower number of single-cluster perforations is beneficial for increasing the breaking pressure and temporary plugging peak pressure,and it has a more significant control on the propagation of multi-cluster fractures.A lower number of clusters is not conducive to increasing the total number and complexity of artificial fractures,while a higher number of clusters makes it difficult to achieve effective plugging.The TPAs within the fracture is mainly concentrated in the complex fracture areas,especially at the intersections of fractures.Meanwhile,the TPAs within the segment are primarily distributed near the perforation cluster apertures which initiated complex fractures.
基金Major Project of National Natural Science Foundation of China Basic Theory of Efficient Development of Shale Oil and Gas(No.51490653)Theory and Method of Efficient Con struction of Fracture Network in Deep and Ultra-Deep Shale Gas Horizontal Wells(No.U19A2043)National Natural Science Foundation of China Theory and Method of Long term Propping for Deep Shale Gas Hydraulic Fractures based on DEM-LBM Hydro-Mechanical Coupling(No.52104039).
文摘When deep and ultra-deep shale gas well fracturing is carried out,multi-cluster fracturing can hardly realize synchronous initiation and propagation of hydraulic fractures due to the combined effects of heterogeneity of deep in-situ stress and"dense cluster"fracture arrangement,and the strong interference between fractures aggravates the unbalanced fracture propagation degree.Field practice proves that the fracture-opening temporary plugging fracturing technology can effectively control the unbalanced propagation of multiple fractures.In addition,the application effect of temporary plugging process can be improved by developing a method for simulating fracture control during fracture-opening temporary plugging fracturing of deep/ultra-deep shale-gas horizontal wells.Based on rock mechanics,elasticity mechanics,fluid mechanics and fracture propagation theory,combined with the flow distribution equation of horizontal-well multi-cluster fracturing and the plugging equation of temporary plugging balls,this paper establishes a fracture propagation model and a fracture control simulation method for the fracture-opening temporary plugging fracturing of deep/ultra-deep shale gas horizontal wells.Then,the influences of the number of temporary plugging balls and the times and timing of temporary plugging on temporary plugging control are simulated,and the influences of temporary plugging balls on fracture propagation morphology and SRV(stimulated reservoir volume)distribution are analyzed by taking Sinopec's one deep shale gas well in Dingshan-Dongxi structure of southeast Sichuan Basin as an example.And the following research results are obtained.First,fracture-opening temporary plugging can significantly promote the balanced propagation of multiple fractures,and the simulation confirms that the number of temporary plugging balls and the times and timing of temporary plugging play an important role in fracture control.Second,as the number of temporary plugging balls increase,the SRV increases firstly and then decreases,so there is an optimal number of temporary plugging balls.Third,increasing the times of temporary plugging can improve the fault tolerance rate of temporary plugging and diverting process,but it is necessary to increase the number of temporary plugging balls appropriately.Fourth,when the timing of temporary plugging is appropriate,the balanced propagation of multiple fractures is achieved and the maximum SRV is reached.In conclusion,this method is of great significance to optimizing the design of temporary plugging fracturing,improve the implementation level of field process and develop deep and ultra-deep shale gas efficiently.
基金the National Natural Science Foundation of China fund (Project number: 52174045 and No. 52104011)Research Foundation of China University of Petroleum-Beijing at Karamay (No. XQZX20210001)PetroChina Innovation Foundation (2020D50070207)。
文摘Due to the reservoir heterogeneity and the stress shadow effect, multiple hydraulic fractures within one fracturing segment cannot be initiated simultaneously and propagate evenly, which will cause a low effectiveness of reservoir stimulation. Temporary plugging and diverting fracturing(TPDF) is considered to be a potential uniform-stimulation method for creating multiple fractures simultaneously in the oilfield. However, the multi-fracture propagation morphology during TPDF is not clear now. The purpose of this study is to quantitatively investigate the multi-fracture propagation morphology during TPDF through true tri-axial fracturing experiments and CT scanning. Critical parameters such as fracture spacing, number of perforation clusters, the viscosity of fracturing fluid, and the in-situ stress have been investigated. The fracture geometry before and after diversion have been quantitively analyzed based on the two-dimensional CT slices and three-dimensional reconstruction method. The main conclusions are as follows:(1) When injecting the high viscosity fluid or perforating at the location with low in-situ stress, multiple hydraulic fractures would simultaneously propagate. Otherwise, only one hydraulic fracture was created during the initial fracturing stage(IFS) for most tests.(2) The perforation cluster effectiveness(PCE) has increased from 26.62% during the IFS to 88.86% after using diverters.(3) The diverted fracture volume has no apparent correlation with the pressure peak and peak frequency during the diversion fracturing stage(DFS) but is positively correlated with water-work.(4) Four types of plugging behavior in shale could be controlled by adjusting the diverter recipe and diverter injection time, and the plugging behavior includes plugging the natural fracture in the wellbore, plugging the previous hydraulic fractures, plugging the fracture tip and plugging the bedding.
基金Project supported by the National Key Basic Research and Development Program(973 Program)“Theory and Technology Adaptability of Shale Gas Development in Typical Marine Blocks in South China”(No.2013CB228006).
文摘Horizontal shale gas well fracturing is mostly carried out by pumping bridge plugs.In the case of casing deformation,the bridge plug can not be pumped down to the designated position,so the hole sections below the deformation could not be stimulated according to the design program.About 30%of horizontal shale gas wells in the Changning and Weiyuan Blocks,Sichuan Basin,suffer various casing deformation after fracturing.Previously,the hole sections which could not be stimulated due to casing deformation were generally abandoned.As a result,the resources controlled by shale gas wells weren't exploited effectively and the fracturing effect was impacted greatly.There are a lot of difficulties in investigating casing deformation,such as complex mechanisms,various influencing factors and unpredictable deformation time.Therefore,it is especially important to seek a staged fracturing technology suitable for the casing deformation sections.In this paper,the staged fracturing technology with sand plugs inside fractures and the staged fracturing technology with temporary plugging balls were tested in casing deformation wells.The staged fracturing technology with sand plugs inside fractures was carried out in the mode of single-stage perforation and single-stage fracturing.The staged fracturing technology with temporary plugging balls was conducted in the mode of single perforation,continuous fracturing and staged ball dropping.Then,two kinds of technologies were compared in terms of their advantages and disadvantages.Finally,they were tested on site.According to the pressure response,the pressure monitoring of the adjacent wells and the microseismic monitoring in the process of actual fracturing,both technologies are effective in the stimulation of the casing deformation sections,realizing well control reserves efficiently and guaranteeing fracturing effects.
基金supported by the National Natural Science Foundation of China(Grant No.51974332)。
文摘Temporary plugging and diverting fracturing(TPDF),involving inner-fracture temporary plugging(IFTP)and inner-stage temporary plugging(ISTP),has been proposed as a widely applied technique in China,for promoting the uniform initiation and propagation of multi-clustered hydraulic fractures(HFs)in a horizontal well of the shale oil/gas reservoirs.However,how the key plugging parameters controlling the multi-fracture growth and the pumping pressure response during TPDF in shale with dense bedding planes(BPs)and natural fractures(NFs)is still unclear,which limits the optimization of TPDF scheme.In this paper,a series of TPDF simulation experiments within a stage of multi-cluster in a horizontal well were carried out on outcrops of Longmaxi Formation shale using a large-scale true tri-axial fracturing simulation system,combined with the acoustic emission(AE)monitor and computed tomography(CT)scanning techniques.Each experiment was divided into three stages,including the conventional fracturing(CF),IFTP and ISTP.Multi-fracture initiation and propagation behavior,and the dominant controlling parameters were examined,containing the particle sizes,concentration of temporary plugging agent(TPA),and cluster number.The results showed that the number of transverse HFs(THFs)and the overall complexity of fracture morphology increase with the increase in TPA concentration and perforation cluster number.Obviously,the required concentration of TPA is positively correlated with the cluster number.Higher peak values and continuous fluctuations of pumping pressure during TPDF may indicate the creation of diversion fractures.The creation of standard THFs during CF is favorable to the creation of diversion fractures during TPDF.Moreover,the activation of BPs nearby the wellbore during CF is unfavorable to the subsequent pressure buildup during TPDF,resulting in poor plugging and diverting effect.Notably,under the strike-slip fault stress regime,the diversion of THFs is not likely during IFTP,which is similar as the results of ISTP to initiate mainly the un-initiated or under-propagated perforation clusters.Three typical pressure curve types during TPDF can be summarized to briefly identify the hydraulic fracture diversion effects,including good(multiple branches or/and THFs can be newly created),fair(HF initiation along the slightly opened BPs and then activating the NFs),and bad(HF initiation along the largely opened BPs and then connecting with the NFs).
基金Supported by the PetroChina–China University of Petroleum (Beijing) Strategic Cooperation Project (ZLZX2020-04)。
文摘To solve the problem that the production of Mahu conglomerate reservoir is not up to expectation after the multi-cluster plus temporary plugging fracturing technology is applied in horizontal wells, stages 2–6 in the test well MaHW6285 are selected to carry out erosion tests with different pumping parameters. The downhole video imaging technology is used to monitor the degree of perforations erosion, and then the fracture initiation and proppant distribution of each cluster are analyzed. The results showed that proppant entered 76.7% of the perforations. The proppant was mainly distributed in a few perforation clusters, and the amount of proppant entered in most of the clusters was limited. The proppant distribution in Stage 4 was relatively uniform, and the fracture initiation of each cluster in the stage is more uniform. The proppant distribution in stages 2, 3, 5, and 6 was significantly uneven, and the uniform degree of fracture initiation in each cluster is low. More than 70% of the proppant dose in the stage entered clusters near the heel end, so the addition of diverters did not promote the uniform initiation of hydraulic fractures. There was a positive correlation between the amount of proppant added and the degree of perforations erosion, and the degree of perforations erosion ranged from 15% to 352%, with an average value of 74.5%, which was far higher than the statistical results of shale reservoir tests in North America. The use of 180° phase perforation(horizontal direction) can reduce the “Phase Bias” of perforations erosion, promote uniform perforations erosion and fluid inflow. The research results provide the basis for optimizing the pumping procedure, reducing the perforation erosion and improving the success rate of diversion.
基金supported by the Scientific Research and Technology Development Project of CNPC“Research and field test of key technologies for effective exploitation of deep shale gas”(No.2019F-31JT).
文摘With the rapid development of shale gas exploration and development in China,casing deformation in shale gas horizontal wells happens frequently,which directly impacts the development efficiency and benefits of shale gas.In order to explore casing deformation prediction,prevention and treatment methods,this paper analyzes the geological and engineering causes of casing deformation in shale-gas horizontal wells through laboratory work,such as the casing resistance to internal pressure alternating test,the ground simulation test and systematical casing deformation characteristic analysis of MIT24 caliper logging,and the large-scale physical simulation test and numerical simulation of casing deformation.Then,combined with the generalized shear activity criterion,a new method for evaluating casing deformation risk points and some technical measures for preventing casing deformation were formulated.And the following research results were obtained.First,the deformation characteristics of 119 casing deformation points in 23 wells interpreted by MIT24 caliper logging are consistent with the mechanical behaviors of shear compression deformation test.Second,the large-scale physical simulation test shows that natural fault-fractures slip obviously under the state of strike-slip stress.Third,numerical simulation shows that the compression stress on casing increases with the increase of fault-fracture slip.When the fault-fracture slip is between 7.5 mm and 9.0 mm,the casing reaches the critical yield strength and begins to undergo plastic deformation.The“temporary fracture plugging+long segment and multi-cluster”and other technologies are field tested in 28 wells in Weiyuan area of southern Sichuan Basin.The casing deformation rate decreases from 54%(before this research)to 14.3%,and the segment loss rate decreases from 7.8%to 0,which reveals remarkable achievements in casing deformation treatment.In conclusion,the shear slip of fault and macro fractures(referred to as fault-fracture)is the main cause of casing deformation in shale gas horizontal wells,and some measures(e.g.“temporary fracture plugging+long segment and multi-cluster”,reducing fracturing scale and releasing wellbore pressure properly)shall be taken in advance to reduce the fault-fracture activity before the risk point of casing deformation is fractured,so as to reach the goal of casing deformation prevention.
