An analytical expression of the peeling mode in the near separatrix region of diverted tokamak plasma is derived. It is shown that in diverted plasmas both with single and double X points, though the perturbed potenti...An analytical expression of the peeling mode in the near separatrix region of diverted tokamak plasma is derived. It is shown that in diverted plasmas both with single and double X points, though the perturbed potential energy of the unstable peeling mode tends to be large, its growth rate becomes very small due to the even larger kinetic energy. Compared to some recent studies that give qualitatively correct results about this growth rate, our result is directly related with the diverted equilibrium quantities suitable for application to realistic experiments.展开更多
The semi-analytical method, previously used to construct model double-null and single-null diverted tokamak equi- libria （Bingren Shi, Plasma Phys. Control Fusion 50 （2008） 085006, 51 （2009） 105008, Nucl. Fusion ...The semi-analytical method, previously used to construct model double-null and single-null diverted tokamak equi- libria （Bingren Shi, Plasma Phys. Control Fusion 50 （2008） 085006, 51 （2009） 105008, Nucl. Fusion 51 （2011） 023004）, is extended to describe diverted tokamak equilibria with nonzero edge current, including the Pfirsch Schliiter（PS） cur- rent. The PS current density is expressed in a way suitable to describe a diverted tokamak configuration in the near separatrix region. The model equilibrium is expressed by only two terms of the exact separable solutions of the Grad Shafranov equation, one of which is governed by a homogeneous ordinary differential equation, and the other by an inhomogeneous one. The particular merits of such a model configuration are that the internal region inside the separa- trix and a suitable scrape-off layer can be simultaneously described by this exact solution. To investigate the physics in the region near the X-point, the magnetic surfaces can be satisfactorily described by approximate hyperbolic curves.展开更多
Marine natural products represent an important class of biologically active compounds critical for drug discovery.To date,17 marine-derived drugs,including trabectedin and eribulin,have been approved by the US FDA for...Marine natural products represent an important class of biologically active compounds critical for drug discovery.To date,17 marine-derived drugs,including trabectedin and eribulin,have been approved by the US FDA for clinical use and 33 others are in clinical trials[1].However,their medicinal investigation and clinical trials are often hampered by the scarcity of natural sources and by the difficulties of their harvesting in the delicate marine environment.Therefore,efficient and scalable approaches for the synthesis of promising marine natural products are essential to overcome supply issues for drug development.展开更多
BACKGROUND Diverting stoma(DS)is routinely proposed in intersphincteric resection for ultra-low rectal cancer,but it is associated with increased stoma-related complications and economic burden.Appropriate patient sel...BACKGROUND Diverting stoma(DS)is routinely proposed in intersphincteric resection for ultra-low rectal cancer,but it is associated with increased stoma-related complications and economic burden.Appropriate patient selection and operative strategies to avoid stoma formation need further elucidation.METHODS This study enrolled 505 consecutive patients,including 84 who underwent stoma-free(SF)intersphincteric resection.After matching,patients were divided into SF(n=78)and DS(n=78)groups.The primary endpoint was the anastomotic leakage(AL)rate within 6 months and its protective factors for both the total and SF cohorts.The secondary endpoints included overall survival and disease-free survival.RESULTS The AL rate was greater in the SF group than in the DS group(12.8%vs 2.6%,P=0.035).Male sex[(odds ratio(OR)=2.644,P=0.021],neoadjuvant chemoradiotherapy(nCRT)(OR=6.024,P<0.001),and tumor height from the anal verge≤4 cm(OR=4.160,P=0.007)were identified as independent risk factors.Preservation of the left colic artery(LCA)was protective in both the total cohort(OR=0.417,P=0.013)and the SF cohort(OR=0.312,P=0.027).The female patients who did not undergo nCRT and had preservation of the LCA experienced a significantly lower incidence of AL(2/97,2.1%).The 3-year overall survival or disease-free survival did not significantly differ be-tween the groups.CONCLUSION Female patients who do not receive nCRT may avoid the need for DS by preserving the LCA without increasing the risk of AL or compromising oncological outcomes.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
Einstein’s weak equivalence principle suggests that gravity and acceleration (centrifugal force) are indistinguishable from each other and, therefore, equivalent. We maintain that they are not only equivalent, but ev...Einstein’s weak equivalence principle suggests that gravity and acceleration (centrifugal force) are indistinguishable from each other and, therefore, equivalent. We maintain that they are not only equivalent, but even identical, or to rephrase the main statement of this work: A gravitational force does not exist. Rather, gravity is a fictitious force, or, more pointedly: Gravity is the centrifugal force which acts upon material bodies within the rotating S3-hypersphere of the Universe. These in turn warp the adjacent space-fabric, shaping it to the well-known field geometry of general relativity.展开更多
Every colorectal surgeon during his or her career is faced with anastomotic leakage(AL); one of the most dreaded complications following any type of gastrointestinal anastomosis due to increased risk of morbidity, mor...Every colorectal surgeon during his or her career is faced with anastomotic leakage(AL); one of the most dreaded complications following any type of gastrointestinal anastomosis due to increased risk of morbidity, mortality, overall impact on functional and oncologic outcome and drainage on hospital resources. In order to understand and give an overview of the AL risk factors in laparoscopic colorectal surgery, we carried out a careful review of the existing literature on this topic and found several different definitions of AL which leads us to believe that the lack of a consensual, standard definition can partly explain the considerable variations in reported rates of AL in clinical studies. Colorectal leak rates have been found to vary depending on the anatomic location of the anastomosis with reported incidence rates ranging from 0 to 20%, while the laparoscopic approach to colorectal resections has not yet been associated with a significant reduction in AL incidence. As well, numerous risk factors, though identified, lack unanimous recognition amongst researchers. For example, the majority of papers describe the risk factors for left-sided anastomosis, the principal risk being male sex and lower anastomosis, while little data exists defining AL risk factors in a right colectomy. Also, gut microbioma is gaining an emerging role as potential risk factor for leakage.展开更多
AIM: To assess the efficacy and safety of diverting colostomy in treating severe hemorrhagic chronic radiation proctitis(CRP). METHODS: Patients with severe hemorrhagic CRP who were admitted from 2008 to 2014 were enr...AIM: To assess the efficacy and safety of diverting colostomy in treating severe hemorrhagic chronic radiation proctitis(CRP). METHODS: Patients with severe hemorrhagic CRP who were admitted from 2008 to 2014 were enrolled into this study. All CRP patients were diagnosed by a combination of pelvic radiation history, clinical rectal bleeding, and endoscopic findings. Inclusion criteria were CRP patients with refractory bleeding with moderate to severe anemia with a hemoglobin level < 90 g/L. The study group included patients who were treated by diverting colostomy, while the control group included patients who received conservative treatment. The remission of bleeding was defined as complete cessation or only occasional bleeding that needed no further treatment. The primary outcome was bleeding remission at 6 mo after treatment. Quality of life beforetreatment and at follow-up was evaluated according to EORTC QLQ C30. Severe CRP complications were recorded during follow-up.RESULTS: Forty-seven consecutive patients were enrolled, including 22 in the colostomy group and 27 in the conservative treatment group. When compared to conservative treatment, colostomy obtained a higher rate of bleeding remission(94% vs 12%), especially in control of transfusion-dependent bleeding(100% vs 0%), and offered a better control of refractory perianal pain(100% vs 0%), and a lower score of bleeding(P < 0.001) at 6 mo after treatment. At 1 year after treatment, colostomy achieved better remission of both moderate bleeding(100% vs 21.5%, P = 0.002) and severe bleeding(100% vs 0%, P < 0.001), obtained a lower score of bleeding(0.8 vs 2.0, P < 0.001), and achieved obvious elevated hemoglobin levels(P = 0.003), when compared to the conservative treatment group. The quality of life dramatically improved after colostomy, which included global health, function, and symptoms, but it was not improved in the control group. Pathological evaluation after colostomy found diffused chronic inflammation cells, and massive fibrosis collagen depositions under the rectal wall, which revealed potential fibrosis formation. CONCLUSION: Diverting colostomy is a simple, effective and safe procedure for severe hemorrhagic CRP. Colostomy can improve quality of life and reduce serious complications secondary to radiotherapy.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
Storage modulus and loss modulus is the main performance index of visco-elastic properties.In this paper the storage modulus and loss modulus of a new diverting acid and their influencing factors were systematically i...Storage modulus and loss modulus is the main performance index of visco-elastic properties.In this paper the storage modulus and loss modulus of a new diverting acid and their influencing factors were systematically investigated.Besides,the constitutive equations of the diverting acid at different temperatures were elicited from shearing experiments,which show that the visco-elastic surfactant(VES)acid system is a non-Newtonian power law fluid at low temperature and a Newtonian fluid at high temperature.The storage modulus and loss modulus at different temperatures,pH,and VES content in the acid are critical for the design of acid stimulation for oil well,especially when the VES acid is used in this field only on trial and the basic data are in urgent needed for the design and construction of the acidification stimulation.展开更多
Objective:To summarize the nursing treatment of patients who underwent implantation of a blood flow diverter to treat complex intracranial aneurysms.Methods:Data from 22 patients with complex aneurysms,diagnosed at an...Objective:To summarize the nursing treatment of patients who underwent implantation of a blood flow diverter to treat complex intracranial aneurysms.Methods:Data from 22 patients with complex aneurysms,diagnosed at an interventional center for blood flow diverter implantation between February 2015 and February 2016,treated in the Henan Provincial People’s Hospital(Zhengzhou,China),were retrospectively analyzed.Nursing methods,including preoperative,intraoperative,and postoperative care,were analyzed.Results:All 22 patients underwent successful surgery,with no related complications or hospital mortality,and were cured in hospital.Conclusion:Interventional flow diverter therapy for patients with complex intracranial aneurysms is a new technology,and involves intensive care by nursing staff and appears to be a promising new treatment method.展开更多
In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and l...In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.展开更多
A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter,which consists of a nozzle and diffuser,is designed for lifting and transporting a hazardous fluid through a narrow mounting hole.The pumpin...A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter,which consists of a nozzle and diffuser,is designed for lifting and transporting a hazardous fluid through a narrow mounting hole.The pumping performance for a liquid mixture or a liquid-solid mixture is examined in terms of the effects of liquid viscosity,particle mass concentration,lifting height,and compression pressure.Results reveal that the pumping performance of the compact pneumatic pulse-jet pump is controlled by jet inertia and the flow resistance of the riser tube positioned after the diffuser.The capacity of the compact pneumatic pulse-jet pump increases with compression pressure and decreases with liquid viscosity.However,even for a liquid mixture with a high viscosity of 7.38 mPa·s,a pumping capacity of 170.7 L·h-1 was observed.For a liquid mixture,two dimensionless indices of performance were found to be the ratio of Euler numbers Euout/EuDV and the suction factor q.As the liquid-solid mixture was lifted to elevation of 6.74 m by the compact pump,the particle size distributions of the liquid-solid mixture in the tank and from the riser tube outlet were determined by a particle size analyzer and found to coincide well.展开更多
Yanhu Lake basin(YHB)is a typical alpine lake on the northeastern Tibetan Plateau(TP).Its continuous expansion in recent years poses serious threats to downstream major projects.As a result,studies of the mechanisms u...Yanhu Lake basin(YHB)is a typical alpine lake on the northeastern Tibetan Plateau(TP).Its continuous expansion in recent years poses serious threats to downstream major projects.As a result,studies of the mechanisms underlying lake expansion are urgently needed.The elasticity method within the Budyko framework was used to calculate the water balance in the Yanhu Lake basin(YHB)and the neighboring Tuotuo River basin(TRB).Results show intensification of hydrological cycles and positive trends in the lake area,river runoff,precipitation,and potential evapotranspiration.Lake expansion was significant between 2001 and 2020 and accelerated between 2015 and 2020.Precipitation increase was the key factor underlying the hydrological changes,followed by glacier meltwater and groundwater.The overflow of Yanhu Lake was inevitable because it was connected to three other lakes and the water balance of all four lakes was positive.The high salinity lake water diverted downstream will greatly impact the water quality of the source area of the Yangtze River and the stability of the permafrost base of the traffic corridor.展开更多
The application of fluid diversion during hydraulic fracturing is an evolving technology and has become popular amongst E&P operators over the past few years.The primary objective of the fluid diversion is to impr...The application of fluid diversion during hydraulic fracturing is an evolving technology and has become popular amongst E&P operators over the past few years.The primary objective of the fluid diversion is to improve hydraulic fracturing treatment by increasing stimulated reservoir volume and improving hydrocarbon recovery.This is possible by achieving any of the following objectives:creating uniform distribution of treatment slurry within the target zone;treating unstimulated and under-stimulated zones;or by increasing fracture density by creating a complex fracture network.The fluid diversion application is also helpful in decreasing the number of stages(by increasing stage length)for multi-stage plug-n-perf(PnP)fracturing treatment.It is also applied to prevent fracture-driven interactions between adjacent wells,which is currently a major issue,especially in shale.In addition,for successful refracturing treatment,the diverter application is essential for isolating the existing fractures and redirecting the treatment slurry to the desired unstimulated zones.The diversion methods can be broadly categorized into the mechanical and chemical diversion.Several established mechanical diversion techniques are frac plugs,expandable casing patches,expandable liners,swellable packers,straddle packer assembly,sand plugs,frac sleeves,perforation ball sealers,and limited entry technique.The different chemical diversion techniques are particulates,fibers,gels,surfactants,perforation pods,and composite diverting.This paper describes the current status of established mechanical and chemical diverter technologies and examines their comparative advantages and challenges.Various techniques are suitable for diverter application,but the technique is selected based on the desired objective and conditions of the wellbore and reservoir.The general guidelines for selecting diversion techniques and operational considerations are also provided in the paper.The diagnosis of diversion treatment plays an essential role in diversion technique selection and optimization of selection parameters for the subsequent treatments.Therefore,the application of conventional surface pressure monitoring techniques and advanced diagnostic tools to evaluate diversion effectiveness are briefly described.Presently no standard laboratory testing method is established for the performance evaluation of diverting agents.Therefore,researchers have implemented various laboratory methods,which are briefly summarized in the paper.Significant insight into the diversion technology and guidelines for its selection and successful implementation is provided to help engineers to increase the effectiveness of hydraulic fracturing treatments.The limitations of individual diversion techniques are clarified,which provide the future scope of research for improvement in various diversion technologies.展开更多
The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry...The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry rock.At present,how temporary plugging agents plug artificial fractures under high temperature remains unclear.In this paper,by establishing an improved experimental system for the evaluation of temporary plugging performance at high temperature,we clarified the effects of high temperature,injection rate,and fracture width on the pressure response and plugging efficiency of the fracture.The results revealed that the temporary plugging process of artificial fractures in hot dry rock can be divided into four main stages:the initial stage of temporary plugging,the bridging stage of the particles,the plugging formation stage,and the high-pressure dense plugging stage.As the temperature increases,the distribution distance of the temporary plugging agent,the number of pressure fluctuations,and the time required for crack plugging increases.Particularly,when the temperature increases by 100℃,the complete plugging time increases by 90.7%.展开更多
The reverse flow diverter (RFD) consisting of a nozzle and a diffuser is a key component in pneumatic pulse jet pumps. We investigated the effects of suction gap and diffuser configurations on RFD performance during t...The reverse flow diverter (RFD) consisting of a nozzle and a diffuser is a key component in pneumatic pulse jet pumps. We investigated the effects of suction gap and diffuser configurations on RFD performance during the reverse flow mode. Three suction gap configurations were examined: (1) an axisymmetrical cylinder, (2) a cuboid whose bottom plane had no half-circle groove and was level with the diffuser entrance lower border, and (3) a cuboid with a half-circle groove on the bottom plane. Among them, the second one resulted in the highest RFD pumping capacity. The effect of receiver presence before the diffuser was also examined. RFD pumping efficiency was found to be enhanced in the presence of a receiver before the diffuser when the suction gap length is small and the jet outlet velocity at the nozzle exit is high enough. Based on experimental data, a dimensionless performance curve of the suction factor q versus the ratio of Euler numbers in sections out-out and 0-0 Eu out /Eu 0 was derived. This curve is insensitive to suction gap configurations.展开更多
In order to obtain the dynamic characteristics of a differential piston warm gas selfpressurization system for liquid attitude and divert propulsion system, a transient model is developed using the modular modeling me...In order to obtain the dynamic characteristics of a differential piston warm gas selfpressurization system for liquid attitude and divert propulsion system, a transient model is developed using the modular modeling method. The system includes the solid start cartridge,pressure-amplified tank with liquid monopropellant, liquid regulator, gas generator, and pipes.The one-dimensional finite-element state-variable model is applied to the pipes and the lumped parameter method is adopted for the other modules. The variations of the system operation parameters over time during the startup, steady-state, and pulsing operational processes are obtained from the transient model, and the characteristics of starting time changing with different system parameters are also analyzed. It is shown that the system startup process can be divided into three distinct processes. The starting time monotonically changes with variations of the liquid regulator parameters, first decreasing and then increasing with the mass change of the solid propellant charge of the start cartridge, initial gas cavity volume of the pressure amplified tank and initial gas cushion of the propellant tank. The starting time can be reduced to less than 1.0 s（0.68–0.75 s for the current system）. For meeting the deviation requirements of ±10% of the steady-state propellant tank pressure, the positive deviation requirement is assured by the self-locking pressure and the negative deviation can be assured within an allowable maximum propellant tank volume flowrate（1.6 times the design value for the proposed system） for downstream thrusters for a designed system. The results from the simulation are useful as a guide for further system design and testing.展开更多
Tight oil reservoirs in Songliao Basin were taken as subjects and a novel idealized refracturing well concept was proposed by considering the special parameters of volume fracturing horizontal wells, the refracturing ...Tight oil reservoirs in Songliao Basin were taken as subjects and a novel idealized refracturing well concept was proposed by considering the special parameters of volume fracturing horizontal wells, the refracturing potential of candidate wells were graded and prioritized, and a production prediction model of refracturing considering the stress sensitivity was established using numerical simulation method to sort out the optimal refracturing method and timing. The simulations show that: with the same perforation clusters, the order of fracturing technologies with contribution to productivity from big to small is refracturing between existent fractured sections, orientation diversion inside fractures, extended refracturing, refracturing of existent fractures; and the later the refracturing timing, the shorter the effective time. Based on this, the prediction model of breakdown pressure considering the variation of formation pressure was used to find out the variation pattern of breakdown pressure of different positions at different production time. Through the classification of the breakdown pressure, the times of temporary plugging and diverting and the amount of temporary plugging agent were determined under the optimal refracturing timing. Daily oil production per well increased from 2.3 t/d to 16.5 t/d in the field test. The research results provide important reference for refracturing optimization design of similar tight oil reservoirs.展开更多
Stimulation of hydraulic fracturing of horizontal shale gas wells in Weirong Block has always been facing many difficulties due to many factors such as complicated geological conditions,small differences between the h...Stimulation of hydraulic fracturing of horizontal shale gas wells in Weirong Block has always been facing many difficulties due to many factors such as complicated geological conditions,small differences between the horizontal principal stress and the vertical principal stress,high working pump pressures,and low sensitive sand ratios.In view of this,by combing the geological structure,engineering geological characteristics and the difficulties of fracturing of deep shale gas wells in Weirong Block,learning from the general idea of volumetric fracturing for shale gas reservoirs at home and abroad,we determined the main ideas and technical countermeasures for fracturing in the area and applied them to the subsequent fracturing practices of shale gas wells.And the following achievements were obtained.First,the conventional fracturing technology applied to the shale gas wells in Weirong Block resulted in low fracture complexity,small stimulated reservoir volume(SRV),difficulties in guaranteeing the effectiveness of perforation clusters,low strength of proppant adding,difficulties in obtaining higher conductivity,poor stable production capacity after stimulation,and difficulties in meeting the need of well fracturing with casing deformation.Second,in view of the difficulties of fracturing stimulation in deep shale gas wells of Weirong Block,super high pressure,huge displacement,large fluid volume,temporary plugging and diverting in fracturing,and variable displacement technology can effectively increase SRV and the complexity of fractures in distant wells.The effectiveness of multi-cluster perforation can be guaranteed by comprehensive utilization of multi-cluster perforation optimization technology,big displacement technology and temporary plugging and diverting&fracturing technology at slots.The continuous proppant-adding technology with huge displacement,high viscosity,low sand ratio,low density and small particle size can improve sand adding strength and fracture conductivity.Besides,the stimulation technology for casing deformed wells using coiled tubing fast processing+small diameter bridge plug and separate pumping technology of perforating gun have been formed.Third,after the above fracturing technologies have been applied in five shale gas horizontal wells in Weirong Block,the average absolute open flow(QAOF)reached 26.11×10^(4)m^(3)/d,indicating a good stimulation effect.In conclusion,this paper can provide meaningful reference for the development of deep shale gas wells of the similar type.展开更多
基金Project supported by the National Magnetic Confinement Fusion Science Program of China （Grant No. 2009GB 101002）.
文摘An analytical expression of the peeling mode in the near separatrix region of diverted tokamak plasma is derived. It is shown that in diverted plasmas both with single and double X points, though the perturbed potential energy of the unstable peeling mode tends to be large, its growth rate becomes very small due to the even larger kinetic energy. Compared to some recent studies that give qualitatively correct results about this growth rate, our result is directly related with the diverted equilibrium quantities suitable for application to realistic experiments.
基金supported by the National Magnetic Confinement Fusion Science Program of China (Grant No. 2009GB101002)
文摘The semi-analytical method, previously used to construct model double-null and single-null diverted tokamak equi- libria （Bingren Shi, Plasma Phys. Control Fusion 50 （2008） 085006, 51 （2009） 105008, Nucl. Fusion 51 （2011） 023004）, is extended to describe diverted tokamak equilibria with nonzero edge current, including the Pfirsch Schliiter（PS） cur- rent. The PS current density is expressed in a way suitable to describe a diverted tokamak configuration in the near separatrix region. The model equilibrium is expressed by only two terms of the exact separable solutions of the Grad Shafranov equation, one of which is governed by a homogeneous ordinary differential equation, and the other by an inhomogeneous one. The particular merits of such a model configuration are that the internal region inside the separa- trix and a suitable scrape-off layer can be simultaneously described by this exact solution. To investigate the physics in the region near the X-point, the magnetic surfaces can be satisfactorily described by approximate hyperbolic curves.
文摘Marine natural products represent an important class of biologically active compounds critical for drug discovery.To date,17 marine-derived drugs,including trabectedin and eribulin,have been approved by the US FDA for clinical use and 33 others are in clinical trials[1].However,their medicinal investigation and clinical trials are often hampered by the scarcity of natural sources and by the difficulties of their harvesting in the delicate marine environment.Therefore,efficient and scalable approaches for the synthesis of promising marine natural products are essential to overcome supply issues for drug development.
基金Supported by Beijing Natural Science Foundation,No.L222054 and No.4232058.
文摘BACKGROUND Diverting stoma(DS)is routinely proposed in intersphincteric resection for ultra-low rectal cancer,but it is associated with increased stoma-related complications and economic burden.Appropriate patient selection and operative strategies to avoid stoma formation need further elucidation.METHODS This study enrolled 505 consecutive patients,including 84 who underwent stoma-free(SF)intersphincteric resection.After matching,patients were divided into SF(n=78)and DS(n=78)groups.The primary endpoint was the anastomotic leakage(AL)rate within 6 months and its protective factors for both the total and SF cohorts.The secondary endpoints included overall survival and disease-free survival.RESULTS The AL rate was greater in the SF group than in the DS group(12.8%vs 2.6%,P=0.035).Male sex[(odds ratio(OR)=2.644,P=0.021],neoadjuvant chemoradiotherapy(nCRT)(OR=6.024,P<0.001),and tumor height from the anal verge≤4 cm(OR=4.160,P=0.007)were identified as independent risk factors.Preservation of the left colic artery(LCA)was protective in both the total cohort(OR=0.417,P=0.013)and the SF cohort(OR=0.312,P=0.027).The female patients who did not undergo nCRT and had preservation of the LCA experienced a significantly lower incidence of AL(2/97,2.1%).The 3-year overall survival or disease-free survival did not significantly differ be-tween the groups.CONCLUSION Female patients who do not receive nCRT may avoid the need for DS by preserving the LCA without increasing the risk of AL or compromising oncological outcomes.
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).
文摘Einstein’s weak equivalence principle suggests that gravity and acceleration (centrifugal force) are indistinguishable from each other and, therefore, equivalent. We maintain that they are not only equivalent, but even identical, or to rephrase the main statement of this work: A gravitational force does not exist. Rather, gravity is a fictitious force, or, more pointedly: Gravity is the centrifugal force which acts upon material bodies within the rotating S3-hypersphere of the Universe. These in turn warp the adjacent space-fabric, shaping it to the well-known field geometry of general relativity.
文摘Every colorectal surgeon during his or her career is faced with anastomotic leakage(AL); one of the most dreaded complications following any type of gastrointestinal anastomosis due to increased risk of morbidity, mortality, overall impact on functional and oncologic outcome and drainage on hospital resources. In order to understand and give an overview of the AL risk factors in laparoscopic colorectal surgery, we carried out a careful review of the existing literature on this topic and found several different definitions of AL which leads us to believe that the lack of a consensual, standard definition can partly explain the considerable variations in reported rates of AL in clinical studies. Colorectal leak rates have been found to vary depending on the anatomic location of the anastomosis with reported incidence rates ranging from 0 to 20%, while the laparoscopic approach to colorectal resections has not yet been associated with a significant reduction in AL incidence. As well, numerous risk factors, though identified, lack unanimous recognition amongst researchers. For example, the majority of papers describe the risk factors for left-sided anastomosis, the principal risk being male sex and lower anastomosis, while little data exists defining AL risk factors in a right colectomy. Also, gut microbioma is gaining an emerging role as potential risk factor for leakage.
基金Supported by National Natural Science Foundation of China,No.81201581,No.81573078 and No.81372566Support Program from Ministry of Science and Technology of China,No.2014BAI09B06Natural Science Foundation of Guangdong Province,China,No.2016A030311021
文摘AIM: To assess the efficacy and safety of diverting colostomy in treating severe hemorrhagic chronic radiation proctitis(CRP). METHODS: Patients with severe hemorrhagic CRP who were admitted from 2008 to 2014 were enrolled into this study. All CRP patients were diagnosed by a combination of pelvic radiation history, clinical rectal bleeding, and endoscopic findings. Inclusion criteria were CRP patients with refractory bleeding with moderate to severe anemia with a hemoglobin level < 90 g/L. The study group included patients who were treated by diverting colostomy, while the control group included patients who received conservative treatment. The remission of bleeding was defined as complete cessation or only occasional bleeding that needed no further treatment. The primary outcome was bleeding remission at 6 mo after treatment. Quality of life beforetreatment and at follow-up was evaluated according to EORTC QLQ C30. Severe CRP complications were recorded during follow-up.RESULTS: Forty-seven consecutive patients were enrolled, including 22 in the colostomy group and 27 in the conservative treatment group. When compared to conservative treatment, colostomy obtained a higher rate of bleeding remission(94% vs 12%), especially in control of transfusion-dependent bleeding(100% vs 0%), and offered a better control of refractory perianal pain(100% vs 0%), and a lower score of bleeding(P < 0.001) at 6 mo after treatment. At 1 year after treatment, colostomy achieved better remission of both moderate bleeding(100% vs 21.5%, P = 0.002) and severe bleeding(100% vs 0%, P < 0.001), obtained a lower score of bleeding(0.8 vs 2.0, P < 0.001), and achieved obvious elevated hemoglobin levels(P = 0.003), when compared to the conservative treatment group. The quality of life dramatically improved after colostomy, which included global health, function, and symptoms, but it was not improved in the control group. Pathological evaluation after colostomy found diffused chronic inflammation cells, and massive fibrosis collagen depositions under the rectal wall, which revealed potential fibrosis formation. CONCLUSION: Diverting colostomy is a simple, effective and safe procedure for severe hemorrhagic CRP. Colostomy can improve quality of life and reduce serious complications secondary to radiotherapy.
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Supported by the Acidification for Heterogeneous Carbonate Reservoirs Program of Petro China Company Limited
文摘Storage modulus and loss modulus is the main performance index of visco-elastic properties.In this paper the storage modulus and loss modulus of a new diverting acid and their influencing factors were systematically investigated.Besides,the constitutive equations of the diverting acid at different temperatures were elicited from shearing experiments,which show that the visco-elastic surfactant(VES)acid system is a non-Newtonian power law fluid at low temperature and a Newtonian fluid at high temperature.The storage modulus and loss modulus at different temperatures,pH,and VES content in the acid are critical for the design of acid stimulation for oil well,especially when the VES acid is used in this field only on trial and the basic data are in urgent needed for the design and construction of the acidification stimulation.
基金National Natural Science Foundation of China(81601583).
文摘Objective:To summarize the nursing treatment of patients who underwent implantation of a blood flow diverter to treat complex intracranial aneurysms.Methods:Data from 22 patients with complex aneurysms,diagnosed at an interventional center for blood flow diverter implantation between February 2015 and February 2016,treated in the Henan Provincial People’s Hospital(Zhengzhou,China),were retrospectively analyzed.Nursing methods,including preoperative,intraoperative,and postoperative care,were analyzed.Results:All 22 patients underwent successful surgery,with no related complications or hospital mortality,and were cured in hospital.Conclusion:Interventional flow diverter therapy for patients with complex intracranial aneurysms is a new technology,and involves intensive care by nursing staff and appears to be a promising new treatment method.
基金supported by National Natural Science Foundation of China (No. 51475369)the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2018JM1001)
文摘In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.
文摘A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter,which consists of a nozzle and diffuser,is designed for lifting and transporting a hazardous fluid through a narrow mounting hole.The pumping performance for a liquid mixture or a liquid-solid mixture is examined in terms of the effects of liquid viscosity,particle mass concentration,lifting height,and compression pressure.Results reveal that the pumping performance of the compact pneumatic pulse-jet pump is controlled by jet inertia and the flow resistance of the riser tube positioned after the diffuser.The capacity of the compact pneumatic pulse-jet pump increases with compression pressure and decreases with liquid viscosity.However,even for a liquid mixture with a high viscosity of 7.38 mPa·s,a pumping capacity of 170.7 L·h-1 was observed.For a liquid mixture,two dimensionless indices of performance were found to be the ratio of Euler numbers Euout/EuDV and the suction factor q.As the liquid-solid mixture was lifted to elevation of 6.74 m by the compact pump,the particle size distributions of the liquid-solid mixture in the tank and from the riser tube outlet were determined by a particle size analyzer and found to coincide well.
基金funded by the National Natural Science Foundation of China(42002264)the China Geological Survey Program(DD20230537)the Fundamental Research Funds for the Central Public Research Institutes(SK202006).
文摘Yanhu Lake basin(YHB)is a typical alpine lake on the northeastern Tibetan Plateau(TP).Its continuous expansion in recent years poses serious threats to downstream major projects.As a result,studies of the mechanisms underlying lake expansion are urgently needed.The elasticity method within the Budyko framework was used to calculate the water balance in the Yanhu Lake basin(YHB)and the neighboring Tuotuo River basin(TRB).Results show intensification of hydrological cycles and positive trends in the lake area,river runoff,precipitation,and potential evapotranspiration.Lake expansion was significant between 2001 and 2020 and accelerated between 2015 and 2020.Precipitation increase was the key factor underlying the hydrological changes,followed by glacier meltwater and groundwater.The overflow of Yanhu Lake was inevitable because it was connected to three other lakes and the water balance of all four lakes was positive.The high salinity lake water diverted downstream will greatly impact the water quality of the source area of the Yangtze River and the stability of the permafrost base of the traffic corridor.
文摘The application of fluid diversion during hydraulic fracturing is an evolving technology and has become popular amongst E&P operators over the past few years.The primary objective of the fluid diversion is to improve hydraulic fracturing treatment by increasing stimulated reservoir volume and improving hydrocarbon recovery.This is possible by achieving any of the following objectives:creating uniform distribution of treatment slurry within the target zone;treating unstimulated and under-stimulated zones;or by increasing fracture density by creating a complex fracture network.The fluid diversion application is also helpful in decreasing the number of stages(by increasing stage length)for multi-stage plug-n-perf(PnP)fracturing treatment.It is also applied to prevent fracture-driven interactions between adjacent wells,which is currently a major issue,especially in shale.In addition,for successful refracturing treatment,the diverter application is essential for isolating the existing fractures and redirecting the treatment slurry to the desired unstimulated zones.The diversion methods can be broadly categorized into the mechanical and chemical diversion.Several established mechanical diversion techniques are frac plugs,expandable casing patches,expandable liners,swellable packers,straddle packer assembly,sand plugs,frac sleeves,perforation ball sealers,and limited entry technique.The different chemical diversion techniques are particulates,fibers,gels,surfactants,perforation pods,and composite diverting.This paper describes the current status of established mechanical and chemical diverter technologies and examines their comparative advantages and challenges.Various techniques are suitable for diverter application,but the technique is selected based on the desired objective and conditions of the wellbore and reservoir.The general guidelines for selecting diversion techniques and operational considerations are also provided in the paper.The diagnosis of diversion treatment plays an essential role in diversion technique selection and optimization of selection parameters for the subsequent treatments.Therefore,the application of conventional surface pressure monitoring techniques and advanced diagnostic tools to evaluate diversion effectiveness are briefly described.Presently no standard laboratory testing method is established for the performance evaluation of diverting agents.Therefore,researchers have implemented various laboratory methods,which are briefly summarized in the paper.Significant insight into the diversion technology and guidelines for its selection and successful implementation is provided to help engineers to increase the effectiveness of hydraulic fracturing treatments.The limitations of individual diversion techniques are clarified,which provide the future scope of research for improvement in various diversion technologies.
基金supported financially by the Beijing Natural Science Foundation Project(No.3222030)the National Natural Science Foundation of China(No.51936001,No.52274002 and No.52192622)+1 种基金the PetroChina Science and Technology Innovation Foundation Project(2021DQ02–0201)Award Cultivation Foundation from Beijing Institute of Petrochemical Technology(No.BIPTACF-002).
文摘The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry rock.At present,how temporary plugging agents plug artificial fractures under high temperature remains unclear.In this paper,by establishing an improved experimental system for the evaluation of temporary plugging performance at high temperature,we clarified the effects of high temperature,injection rate,and fracture width on the pressure response and plugging efficiency of the fracture.The results revealed that the temporary plugging process of artificial fractures in hot dry rock can be divided into four main stages:the initial stage of temporary plugging,the bridging stage of the particles,the plugging formation stage,and the high-pressure dense plugging stage.As the temperature increases,the distribution distance of the temporary plugging agent,the number of pressure fluctuations,and the time required for crack plugging increases.Particularly,when the temperature increases by 100℃,the complete plugging time increases by 90.7%.
文摘The reverse flow diverter (RFD) consisting of a nozzle and a diffuser is a key component in pneumatic pulse jet pumps. We investigated the effects of suction gap and diffuser configurations on RFD performance during the reverse flow mode. Three suction gap configurations were examined: (1) an axisymmetrical cylinder, (2) a cuboid whose bottom plane had no half-circle groove and was level with the diffuser entrance lower border, and (3) a cuboid with a half-circle groove on the bottom plane. Among them, the second one resulted in the highest RFD pumping capacity. The effect of receiver presence before the diffuser was also examined. RFD pumping efficiency was found to be enhanced in the presence of a receiver before the diffuser when the suction gap length is small and the jet outlet velocity at the nozzle exit is high enough. Based on experimental data, a dimensionless performance curve of the suction factor q versus the ratio of Euler numbers in sections out-out and 0-0 Eu out /Eu 0 was derived. This curve is insensitive to suction gap configurations.
文摘In order to obtain the dynamic characteristics of a differential piston warm gas selfpressurization system for liquid attitude and divert propulsion system, a transient model is developed using the modular modeling method. The system includes the solid start cartridge,pressure-amplified tank with liquid monopropellant, liquid regulator, gas generator, and pipes.The one-dimensional finite-element state-variable model is applied to the pipes and the lumped parameter method is adopted for the other modules. The variations of the system operation parameters over time during the startup, steady-state, and pulsing operational processes are obtained from the transient model, and the characteristics of starting time changing with different system parameters are also analyzed. It is shown that the system startup process can be divided into three distinct processes. The starting time monotonically changes with variations of the liquid regulator parameters, first decreasing and then increasing with the mass change of the solid propellant charge of the start cartridge, initial gas cavity volume of the pressure amplified tank and initial gas cushion of the propellant tank. The starting time can be reduced to less than 1.0 s（0.68–0.75 s for the current system）. For meeting the deviation requirements of ±10% of the steady-state propellant tank pressure, the positive deviation requirement is assured by the self-locking pressure and the negative deviation can be assured within an allowable maximum propellant tank volume flowrate（1.6 times the design value for the proposed system） for downstream thrusters for a designed system. The results from the simulation are useful as a guide for further system design and testing.
基金Supported by the National Natural Science Foundation of China(51525404,51504203)China National Science and Technology Major Project(2016ZX05002002)
文摘Tight oil reservoirs in Songliao Basin were taken as subjects and a novel idealized refracturing well concept was proposed by considering the special parameters of volume fracturing horizontal wells, the refracturing potential of candidate wells were graded and prioritized, and a production prediction model of refracturing considering the stress sensitivity was established using numerical simulation method to sort out the optimal refracturing method and timing. The simulations show that: with the same perforation clusters, the order of fracturing technologies with contribution to productivity from big to small is refracturing between existent fractured sections, orientation diversion inside fractures, extended refracturing, refracturing of existent fractures; and the later the refracturing timing, the shorter the effective time. Based on this, the prediction model of breakdown pressure considering the variation of formation pressure was used to find out the variation pattern of breakdown pressure of different positions at different production time. Through the classification of the breakdown pressure, the times of temporary plugging and diverting and the amount of temporary plugging agent were determined under the optimal refracturing timing. Daily oil production per well increased from 2.3 t/d to 16.5 t/d in the field test. The research results provide important reference for refracturing optimization design of similar tight oil reservoirs.
基金supported by the Scientific Research Project of Sinopec Oilfield Service Corporation“Key technologies for deep shale gas fracturing and gas testing in Weiyuan-Yongchuan”(No.:SG1704-02K).
文摘Stimulation of hydraulic fracturing of horizontal shale gas wells in Weirong Block has always been facing many difficulties due to many factors such as complicated geological conditions,small differences between the horizontal principal stress and the vertical principal stress,high working pump pressures,and low sensitive sand ratios.In view of this,by combing the geological structure,engineering geological characteristics and the difficulties of fracturing of deep shale gas wells in Weirong Block,learning from the general idea of volumetric fracturing for shale gas reservoirs at home and abroad,we determined the main ideas and technical countermeasures for fracturing in the area and applied them to the subsequent fracturing practices of shale gas wells.And the following achievements were obtained.First,the conventional fracturing technology applied to the shale gas wells in Weirong Block resulted in low fracture complexity,small stimulated reservoir volume(SRV),difficulties in guaranteeing the effectiveness of perforation clusters,low strength of proppant adding,difficulties in obtaining higher conductivity,poor stable production capacity after stimulation,and difficulties in meeting the need of well fracturing with casing deformation.Second,in view of the difficulties of fracturing stimulation in deep shale gas wells of Weirong Block,super high pressure,huge displacement,large fluid volume,temporary plugging and diverting in fracturing,and variable displacement technology can effectively increase SRV and the complexity of fractures in distant wells.The effectiveness of multi-cluster perforation can be guaranteed by comprehensive utilization of multi-cluster perforation optimization technology,big displacement technology and temporary plugging and diverting&fracturing technology at slots.The continuous proppant-adding technology with huge displacement,high viscosity,low sand ratio,low density and small particle size can improve sand adding strength and fracture conductivity.Besides,the stimulation technology for casing deformed wells using coiled tubing fast processing+small diameter bridge plug and separate pumping technology of perforating gun have been formed.Third,after the above fracturing technologies have been applied in five shale gas horizontal wells in Weirong Block,the average absolute open flow(QAOF)reached 26.11×10^(4)m^(3)/d,indicating a good stimulation effect.In conclusion,this paper can provide meaningful reference for the development of deep shale gas wells of the similar type.
