The oil production of the multi-fractured horizontal wells(MFHWs) declines quickly in unconventional oil reservoirs due to the fast depletion of natural energy. Gas injection has been acknowledged as an effective meth...The oil production of the multi-fractured horizontal wells(MFHWs) declines quickly in unconventional oil reservoirs due to the fast depletion of natural energy. Gas injection has been acknowledged as an effective method to improve oil recovery factor from unconventional oil reservoirs. Hydrocarbon gas huff-n-puff becomes preferable when the CO_(2) source is limited. However, the impact of complex fracture networks and well interference on the EOR performance of multiple MFHWs is still unclear. The optimal gas huff-n-puff parameters are significant for enhancing oil recovery. This work aims to optimize the hydrocarbon gas injection and production parameters for multiple MFHWs with complex fracture networks in unconventional oil reservoirs. Firstly, the numerical model based on unstructured grids is developed to characterize the complex fracture networks and capture the dynamic fracture features.Secondly, the PVT phase behavior simulation was carried out to provide the fluid model for numerical simulation. Thirdly, the optimal parameters for hydrocarbon gas huff-n-puff were obtained. Finally, the dominant factors of hydrocarbon gas huff-n-puff under complex fracture networks are obtained by fuzzy mathematical method. Results reveal that the current pressure of hydrocarbon gas injection can achieve miscible displacement. The optimal injection and production parameters are obtained by single-factor analysis to analyze the effect of individual parameter. Gas injection time is the dominant factor of hydrocarbon gas huff-n-puff in unconventional oil reservoirs with complex fracture networks. This work can offer engineers guidance for hydrocarbon gas huff-n-puff of multiple MFHWs considering the complex fracture networks.展开更多
Hydraulic fracturing is a key technology for the development of unconventional hydrocarbon resources.The proppant placement morphology determines the fracture conductivity,thus affecting the reservoir stimulation effe...Hydraulic fracturing is a key technology for the development of unconventional hydrocarbon resources.The proppant placement morphology determines the fracture conductivity,thus affecting the reservoir stimulation effect.In this paper,the proppant migration and placement within complex fractures was studied by considering the fracture wall roughness through computational fluid mechanics-discrete element method(CFD-DEM)in numerical simulation,which is a key approach to study the proppant migration and placement.The results show that the proppant placement non-uniformity,proppant migration capacity,and proppant volume filled in the far-end and the secondary branched fracture are enhanced within the rough fracture compared with those within smooth fractures.The proppant migration capacity is increased within the fracture at low inclination angles(<60°)and low approach angles(<90°),and the proppant placement area is larger in the inclined fracture than that in the vertical fracture.The rise of injection rate and fracturing fluid viscosity causes more proppants migrate to far-end or secondary fractures,resulting in a non-proppant area within the near-wellbore fracture.An increase by 1.3 times in the injection rate and 3 times in the fracturing fluid viscosity leads to a decrease by 26.6%and 27%,respectively,in the proppant placement area within the near-wellbore fracture.The staged injection with small size proppants followed by large size proppants increases the proppant placement area in the primary fracture by 13%-26%,and that with large size proppants followed by small size proppants increases the proppant placement area by 19%-25%,which is due to that the latter method facilitates filling of the secondary branched fracture.The injection location mainly affects the proppant filling degree within the near-wellbore fractures.Compared with the upper injection,the middle and lower injection is not beneficial to filling of proppants within the near-wellbore fracture.展开更多
Severe well interference through complex fracture networks(CFNs)can be observed among multi-well pads in low permeability reservoirs.The well interference analysis between multi-fractured horizontal wells(MFHWs)is vit...Severe well interference through complex fracture networks(CFNs)can be observed among multi-well pads in low permeability reservoirs.The well interference analysis between multi-fractured horizontal wells(MFHWs)is vitally important for reservoir effective development.Well interference has been historically investigated by pressure transient analysis,while it has shown that rate transient analysis has great potential in well interference diagnosis.However,the impact of complex fracture networks(CFNs)on rate transient behavior of parent well and child well in unconventional reservoirs is still not clear.To further investigate,this paper develops an integrated approach combining pressure and rate transient analysis for well interference diagnosis considering CFNs.To perform multi-well simulation considering CFNs,non-intrusive embedded discrete fracture model approach was applied for coupling fracture with reservoir models.The impact of CFN including natural fractures and frac-hits on pressure and rate transient behavior in multi-well system was investigated.On a logelog plot,interference flow and compound linear flow are two new flow regimes caused by nearby producers.When both NFs and frac-hits are present in the reservoir,frac-hits have a greater impact on well#1 which contains frac-hits,and NFs have greater impact on well#3 which does not have frac-hits.For all well producing circumstances,it might be challenging to see divergence during pseudosteady state flow brought on by frac-hits on the logelog plot.Besides,when NFs occur,reservoir depletion becomes noticeable in comparison to frac-hits in pressure distribution.Application of this integrated approach demonstrates that it works well to characterize the well interference among different multi-fractured horizontal wells in a well pad.Better reservoir evaluation can be acquired based on the new features observed in the novel model,demonstrating the practicability of the proposed approach.The findings of this study can help for better evaluating well interference degree in multi-well systems combing PTA and RTA,which can reduce the uncertainty and improve the accuracy of the well interference analysis based on both field pressure and rate data.展开更多
In practical development of unconventional reservoirs,fracture networks are a highly conductive transport media for subsurface fluid flow.Therefore,it is crucial to clearly determine the fracture properties used in pr...In practical development of unconventional reservoirs,fracture networks are a highly conductive transport media for subsurface fluid flow.Therefore,it is crucial to clearly determine the fracture properties used in production forecast.However,it is different to calibrate the properties of fracture networks because it is an inverse problem with multi-patterns and highcomplexity of fracture distribution and inherent defect of multiplicity of solution.In this paper,in order to solve the problem,the complex fracture model is divided into two sub-systems,namely"Pattern A"and"Pattern B."In addition,the generation method is grouped into two categories.Firstly,we construct each sub-system based on the probability density function of the fracture properties.Secondly,we recombine the sub-systems into an integral complex fracture system.Based on the generation mechanism,the estimation of the complex fracture from dynamic performance and observation data can be solved as an inverse problem.In this study,the Bayesian formulation is used to quantify the uncertainty of fracture properties.To minimize observation data misfit immediately as it occurs,we optimize the updated properties by a simultaneous perturbation stochastic algorithm which requires only two measurements of the loss function.In numerical experiments,we firstly visualize that small-scale fractures significantly contribute to the flow simulation.Then,we demonstrate the suitability and effectiveness of the Bayesian formulation for calibrating the complex fracture model in the following simulation.展开更多
The paper presents a novel hydraulic fracturing model for the characterization and simulation of the complex fracture network in shale gas reservoirs. We go beyond the existing method that uses planar or orthogonal co...The paper presents a novel hydraulic fracturing model for the characterization and simulation of the complex fracture network in shale gas reservoirs. We go beyond the existing method that uses planar or orthogonal conjugate fractures for representing the ＇＇complexity＇＇ of the network. Bifurcation of fractures is performed utilizing the Lindenmayer system based on fractal geometry to describe the fracture propagation pattern, density and network connectivity. Four controlling parameters are proposed to describe the details of complex fractures and stimulated reservoir volume（SRV）. The results show that due to the multilevel feature of fractal fractures, the model could provide a simple method for contributing reservoir volume calibration. The primary-and second-stage fracture networks across the overall SRV are the main contributions to the production, while the induced fracture network just contributes another 20% in the late producing period. We also conduct simulation with respect to different refracturing cases and find that increasing the complexity of the fracture network provides better performance than only enhancing the fracture conductivity.展开更多
In this paper,a large-scale experimental system was established to identify the migration and distribution laws of complex fracture proppant in shale reservoir volume fracturing.With this system,the effects of seconda...In this paper,a large-scale experimental system was established to identify the migration and distribution laws of complex fracture proppant in shale reservoir volume fracturing.With this system,the effects of secondary fracture angle,fluid displacement,proppant concentration and size,fracturing fluid viscosity and other factors on the migration and distribution of proppant were tested,and the migration and distribution of proppant in primary/secondary fractures were analyzed.The following results were obtained.First,the fluid flow pattern in fractures transforms gradually from laminar flow into turbulent flow with the increase of fracture supporting height.Second,the migration modes of proppant in fractures mainly include suspended migration and gliding migration.Third,the distribution form of proppant in primary fractures before branching is related to secondary fracture angle,fluid displacement and proppant concentration and size,among which the fluid displacement is the most important factor.Fourth,the mass ratio of proppant in primary fractures after branching is proportional to the secondary fracture angle,fluid displacement,fracturing fluid viscosity and proppant concentration and size,and is inversely proportional to the flow ratio between secondary fractures and primary fractures.Fifth,the mass ratio of proppant in secondary fractures after branching is proportional to fluid displacement,fracturing fluid viscosity and flow ratio between secondary fractures and primary fractures,and is inversely proportional to secondary fracture angle and proppant concentration and size.Sixth,the angle at the leading edge of proppant bank in the primary fractures after branching is proportional to the proppant concentration and size and the flow ratio between secondary fractures and primary fractures,but is inversely proportional to secondary fracture angle,fluid displacement and fracturing fluid viscosity.Seventh,the angle at the leading edge of proppant bank in the secondary fractures after branching is proportional to the secondary fracture angle and the proppant concentration and size,but is inversely proportional to the fluid displacement,fracturing fluid viscosity and flow ratio between secondary fractures and primary fractures.In conclusion,the research results can provide a theoretical support for proppant optimization and program design of shale reservoir volume fracturing.展开更多
When hydraulic fractures intersect with natural fractures,the geometry and complexity of a fracture network are determined by the initiation and propagation pattern which is affected by a number of factors.Based on th...When hydraulic fractures intersect with natural fractures,the geometry and complexity of a fracture network are determined by the initiation and propagation pattern which is affected by a number of factors.Based on the fracture mechanics,the criterion for initiation and propagation of a fracture was introduced to analyze the tendency of a propagating angle and factors affecting propagating pressure.On this basis,a mathematic model with a complex fracture network was established to investigate how the fracture network form changes with different parameters,including rock mechanics,in-situ stress distribution,fracture properties,and frac treatment parameters.The solving process of this model was accelerated by classifying the calculation nodes on the extending direction of the fracture by equal pressure gradients,and solving the geometrical parameters prior to the iteration fitting flow distribution.With the initiation and propagation criterion as the bases for the propagation of branch fractures,this method decreased the iteration times through eliminating the fitting of the fracture length in conventional 3D fracture simulation.The simulation results indicated that the formation with abundant natural fractures and smaller in-situ stress difference is sufficient conditions for fracture network development.If the pressure in the hydraulic fractures can be kept at a high level by temporary sealing or diversion,the branch fractures will propagate further with minor curvature radius,thus enlarging the reservoir stimulation area.The simulated shape of fracture network can be well matched with the field microseismic mapping in data point range and distribution density,validating the accuracy of this model.展开更多
Multi-stage volume fracturing of horizontal wells is the main means to develop tight gas reservoirs.Complex fracture networks of various shapes are generated around the wellbore after volume fracturing.At present,howe...Multi-stage volume fracturing of horizontal wells is the main means to develop tight gas reservoirs.Complex fracture networks of various shapes are generated around the wellbore after volume fracturing.At present,however,most of the well test models suitable for fracturing horizontal wells take all hydraulic fractures as single main fractures,which results in a large error between well test interpretation result and actual situation.As a result,the fracture network characteristic parameters of the stimulated areas cannot be obtained accurately.To this end,a well test model for complex fracture networks in tight-gas fracturing horizontal wells was established on the basis of the non-structural discrete fracture model.Then,this model was solved by using thefinite element method with combined triangular elements and linear elements.And accordingly,the well test type curves of a horizontal well under different fracture network patterns(rectangular,elliptical and hyperbolic)were prepared.Based on this,well test type curves were analyzed from the aspects of characteristics and influential factors and were compared with those obtained from the conventional single-fracture model.Finally,the new model was applied in well test interpretation of one multi-stage volume fracturing horizontal well in the gas reservoir of Permian Shan 1 formation in the Qingyang Gas Field of the Ordos Basin.And the following research results were obtained.First,the biggest difference of well test type curve between the fracture network model and the conventional single-fracture model occurs in the early stage,the characteristics offirst linearflow regime are replaced with the characteristics of pseudo-radialflow regime in the stimulated area.Second,the end time of the pseudo-radialflow regime in the stimulated area is mainly dominated by the size and shape of the stimulated area.The larger the stimulated area is,the longer the pseudo-radialflow regime lasts.As the shape of the stimulated area approaches to be elongated,the characteristics of the well test type curve obtained by the new model are more consistent with those by the single-fracture model.Third,the pressure derivative value of the pseudo-radialflow regime in the stimulated area is mainly dependent on the conductivity and density of the fracture network.The higher the density or the conductivity of fracture network in the stimulated area is,the earlier the wellbore storage effect regime ends,the lower the pressure derivative value of the pseudo-radialflow regime in the stimulated area is and the more obvious the characteristics of the horizontal line are.In conclusion,case study results confirm that the new model is reliable and practical and can provide accurate reservoir parameters as well as the size of the effectively stimulated area by volume fracturing and the conductivity of fracture network,which is conducive to evaluating the stimulation effect of volume fracturing and predicting the postfrac production performance.展开更多
Well interference has become a common phenomenon with the increasing scale of horizontal well fracturing.Recent studies on well interference in horizontal wells do not properly reflect the physical model of the postfr...Well interference has become a common phenomenon with the increasing scale of horizontal well fracturing.Recent studies on well interference in horizontal wells do not properly reflect the physical model of the postfracturing well groups and the realistic fracturing process of infill wells.Establishing the correspondence between well interference causative factors and manifestations is of great significance for infill well deployment and secondary oil recovery.In this work,we develop a numerical model that considers low velocity non-Darcy seepage inshale reservoirs to study the inter-well interferencephenomenon that occurs in theSantanghufield,andconstruct an explicit hydraulic fracture and complex natural fracture network model with an embedded discrete fracture model,focusing on the effect of fracture network morphology on well interactions.The model also considers a multi-segment wellbore model to accommodate the effect of inter-well crossflow on wellbore tubular flow.The changes in formation pressure and water saturation during fracturing are performed by controlling the injection pressure and water injection rate.The result shows that the shape of the fracture network generated by the infill well with the old well determines the subsequent fluid and oil-increasing performance of the disturbed well.The synergistic production or competitive relationship formed by fractures with different connectivity between the two wells determines the positive and negative effects of the interference.The paper also investigates the adaptation study of water injection huff and puff schemes for well groups with different connectivity,and demonstrated a potential yield increase of up to 10.85%under adaptation injection.This method of identifying well interference based on the production dynamics of affected wells and the subsequent corresponding water injection method provides valuable references for the selection of secondary oil recovery measures.展开更多
In this paper,a series of specific studies were carried out to investigate the complex form of fracture networks and figure out the multi-scale flowing laws of nano/micro poresecomplex fracture networks-wellbore durin...In this paper,a series of specific studies were carried out to investigate the complex form of fracture networks and figure out the multi-scale flowing laws of nano/micro poresecomplex fracture networks-wellbore during the development of shale reservoirs by means of horizontal well fracturing.First,hydraulic fractures were induced by means of Brazilian splitting tests.Second,the forms of the hydraulic fractures inside the rock samples were observed by means of X-ray CT scanning to measure the opening of hydraulic fractures.Third,based on the multi-scale unified flowing model,morphological description of fractures and gas flowing mechanism in the matrixecomplex fracture networkewellbore,the productivity equation of single-stage horizontal well fracturing which includes diffusion,slipping and desorption was established.And fourthly,a productivity prediction model of horizontal well multi-stage fracturing in the shale reservoir was established considering the interference between the multi-stage fracturing zones and the pressure drop in the horizontal wellbore.The following results were obtained.First,hydraulic fractures are in the form of a complex network.Second,the measured opening of hydraulic fractures is in the range of 4.25-453 mm,averaging 112 mm.Third,shale gas flowing in different shapes of fracture networks follows different nonlinear flowing laws.Forth,as the fracture density in the strongly stimulated zones rises and the distribution range of the hydraulic fractures in strongly/weakly stimulated zones enlarges,gas production increases gradually.As the interference occurs in the flowing zones of fracture networks between fractured sections,the increasing amplitude of gas production rates decreases.Fifth,when the length of a simulated horizontal well is 1500 m and the half length of a fracture network in the strongly stimulated zone is 100 m,the productivity effect of stage 10 fracturing is the best.Therefore,it is necessary to control fracturing degree reasonably and optimize fracturing parameters,so as to provide a theoretical support for the optimization design of shale gas reservoir fracturing.展开更多
Horizontal well and volume fracturing technology are the key technologies to develop unconventional reservoirs.Tight reservoir is belonging to multi-scale seepage mediaafter fracturing,and theflow offluid in it is extre...Horizontal well and volume fracturing technology are the key technologies to develop unconventional reservoirs.Tight reservoir is belonging to multi-scale seepage mediaafter fracturing,and theflow offluid in it is extremely complicated.In this paper,based on the boundary element method(BEM),the seepage model of horizontal wells with complex fracture networks in irregular boundary reservoir is established for thefirst time.The model takes into account the influence of irregular reservoir boundary,dual media,complex fracture network and interference of multiple wells on horizontal well seepage.Using this model,the sensitivity analysis of wellbore storage coefficient,skin factor,fracture permeability and interporosity transfer coefficient is carried out.The model expands the application scope of BEM in thefield of seepage simulation of unconventional oil and gas reservoirs and provides theoretical guidance for the development of tight oil reservoirs.展开更多
By integrating laboratory physical modeling experiments with machine learning-based analysis of dominant factors,this study explored the feasibility of pulse hydraulic fracturing(PHF)in deep coal rocks and revealed th...By integrating laboratory physical modeling experiments with machine learning-based analysis of dominant factors,this study explored the feasibility of pulse hydraulic fracturing(PHF)in deep coal rocks and revealed the fracture propagation patterns and the mechanisms of pulsating loading in the process.The results show that PHF induces fatigue damage in coal matrix,significantly reducing breakdown pressure and increasing fracture network volume.Lower vertical stress differential coefficient(less than 0.31),lower peak pressure ratio(less than 0.9),higher horizontal stress differential coefficient(greater than 0.13),higher pulse amplitude ratio(greater than or equal to 0.5)and higher pulse frequency(greater than or equal to 3 Hz)effectively decrease the breakdown pressure.Conversely,higher vertical stress differential coefficient(greater than or equal to 0.31),higher pulse amplitude ratio(greater than or equal to 0.5),lower horizontal stress differential coefficient(less than or equal to 0.13),lower peak pressure ratio(less than 0.9),and lower pulse frequency(less than 3 Hz)promote the formation of a complex fracture network.Vertical stress and peak pressure are the most critical geological and engineering parameters affecting the stimulation effectiveness of PHF.The dominant mechanism varies with coal rank due to differences in geomechanical characteristics and natural fracture development.Low-rank coal primarily exhibits matrix strength degradation.High-rank coal mainly involves the activation of natural fractures and bedding planes.Medium-rank coal shows a coexistence of matrix strength degradation and micro-fracture connectivity.The PHF forms complex fracture networks through the dual mechanism of matrix strength degradation and fracture network connectivity enhancement.展开更多
This study investigated the micro-sliding frictional behavior of shale in fracturing fluids under varying operational conditions using Chang 7 shale oil reservoir core samples.Through systematic micro-sliding friction...This study investigated the micro-sliding frictional behavior of shale in fracturing fluids under varying operational conditions using Chang 7 shale oil reservoir core samples.Through systematic micro-sliding friction experiments,the characteristics and governing mechanisms of shale friction were elucidated.Complementary analyses were conducted to characterize the mineral composition,petrophysical properties,and micromorphology of the shale samples,providing insights into the relationship between microscopic structure and frictional response.In this paper,the characteristics and variation law of shale micro-sliding friction under different types of graphite materials as additives in LGF-80(Low-damage Guar Fluid)oil flooding recoverable fracturing fluid system were mainly studied.In addition,the finite element numerical simulation experiment of hydraulic fracturing was adopted to study the influence of the friction coefficient of natural fracture surfaces on fracture propagation and formation of the fracture network.The geometric complexity of fracture networks was systematically quantified under varying frictional coefficients of natural fracture surfaces through multi-parametric characterization and morphometric analysis.The research results show that graphite micro-particles reduce friction and drag.Based on this,this paper proposes a new idea of graphite micro-particles as an additive in the LGF-80 oil flooding recoverable fracturing fluid system to reduce friction on the fracture surface.展开更多
Patients suffering from zygomatic complex fractures always present facial deformity and dyslunctions, and thereafter develop psychological and physiological problems. It is really hard to get an ideal prog- nosis for ...Patients suffering from zygomatic complex fractures always present facial deformity and dyslunctions, and thereafter develop psychological and physiological problems. It is really hard to get an ideal prog- nosis for the zygomatic complex fractures because of the complicated anatomical structures. Computer- assisted surgery techniques, as the new emerging auxiliary methods, can optimize the surgical protocol, predict operation outcomes, and improve the accuracy and quality of the operation. Meanwhile the postoperative complications can be reduced effectively. This review aims to provide a comprehensive overview of the application of computer-assisted surgery techniques in the management of zygomatic complex fractures.展开更多
This study extends an integrated field characterization in Eagle Ford by optimizing the numerical reservoir simulation of highly representative complex fractured systems through embedded discrete fracture modeling(EDF...This study extends an integrated field characterization in Eagle Ford by optimizing the numerical reservoir simulation of highly representative complex fractured systems through embedded discrete fracture modeling(EDFM). The bottom-hole flowing pressure was history-matched and the field production was forecasted after screening complex fracture scenarios with more than 100 000 fracture planes based on their propped-type. This work provided a greater understanding of the impact of complex-fractures proppant efficiency on the production. After compaction tables were included for each propped-type fracture group, the estimated pressure depletion showed that the effective drainage area can be smaller than the complex fracture network if modeled and screened by the EDFM method rather than unstructured gridding technique. The essential novel value of this work is the capability to couple EDFM with third-party fracture propagation simulation automatically, considering proppant intensity variation along the complex fractured systems. Thus, this work is pioneer to model complex fracture propagation and well interference accurately from fracture diagnostics and pseudo 3 D fracture propagation outcomes for multiple full wellbores to capture well completion effectiveness after myriads of sharper field simulation cases with EDFM.展开更多
Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and ...Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and fracture structure lead to complex multiphase flow,comprehensively considering multiple mechanisms is crucial for development and CO_(2) storage in fractured shale reservoirs.In this paper,a multi-mechanism coupled model is developed by MATLAB.Compared to the traditional Eclipse300 and MATLAB Reservoir Simulation Toolbox(MRST),this model considers the impact of pore structure on fluid phase behavior by the modified Peng—Robinson equation of state(PR-EOS),and the effect simultaneously radiate to Maxwell—Stefan(M—S)diffusion,stress sensitivity,the nano-confinement(NC)effect.Moreover,a modified embedded discrete fracture model(EDFM)is used to model the complex fractures,which optimizes connection types and half-transmissibility calculation approaches between non-neighboring connections(NNCs).The full implicit equation adopts the finite volume method(FVM)and Newton—Raphson iteration for discretization and solution.The model verification with the Eclipse300 and MRST is satisfactory.The results show that the interaction between the mechanisms significantly affects the production performance and storage characteristics.The effect of molecular diffusion may be overestimated in oil-dominated(liquid-dominated)shale reservoirs.The well spacing and injection gas rate are the most crucial factors affecting the production by sensitivity analysis.Moreover,the potential gas invasion risk is mentioned.This model provides a reliable theoretical basis for CO_(2)-EOR and sequestration in shale oil reservoirs.展开更多
Efficient flow simulation and optimization methods of hydraulic fracture morphology in unconventional reservoirs are effective ways to enhance oil/gas recovery.Based on the connection element method(CEM)and distributi...Efficient flow simulation and optimization methods of hydraulic fracture morphology in unconventional reservoirs are effective ways to enhance oil/gas recovery.Based on the connection element method(CEM)and distribution of stimulated reservoir volume,the complex hydraulic fracture morphology was accurately described using heterogeneous node connection system.Then a new fracture connection element method(FCEM)for fluid flow in stimulated unconventional reservoirs with complex hydraulic fracture morphology was proposed.In the proposed FCEM,the arrangement of dense nodes in the stimulated area and sparse nodes in the unstimulated area ensures the calculation accuracy and efficiency.The key parameter,transmissibility,was also modified according to the strong heterogeneity of stimulated reservoirs.The finite difference and semi-analytical tracking were used to accurately solve the pressure and saturation distribution between nodes.The FCEM is validated by comparing with traditional numerical simulation method,and the results show that the bottom hole pressure simulated by the FCEM is consistent with the results from traditional numerical simulation method,and the matching rate is larger than 95%.The proposed FCEM was also used in the optimization of fracturing parameters by coupling the hydraulic fracture propagation method and intelligent optimization algorithm.The integrated intelligent optimization approach for multi-parameters,such as perforation number,perforation location,and displacement in hydraulic fracturing is proposed.The proposed approach was applied in a shale gas reservoir,and the result shows that the optimized perforation location and morphology distribution are related to the distribution of porosity/permeability.When the perforation location and displacement are optimized with the same fracture number,NPV increases by 70.58%,which greatly improves the economic benefits of unconventional reservoirs.This work provides a new way for flow simulation and optimization of hydraulic fracture morphology of multi-fractured horizontal wells in unconventional reservoirs.展开更多
Aim: To analyse the epidemiology, aetiology, and surgical management of zygomatic complex (ZMC) fractures in our major trauma centre, and to compare the number and location of fixation points and surgical access in ou...Aim: To analyse the epidemiology, aetiology, and surgical management of zygomatic complex (ZMC) fractures in our major trauma centre, and to compare the number and location of fixation points and surgical access in our patient cohort with the literature. Methods: Retrospective analysis of all operative cases (Open Reduction and Internal Fixation) of zygomatic complex fractures over a one year period (2016). Results: A greater proportion of patients in our cohort (54%) were treated with one-point fixation compared to the literature, with the zygomaticomaxillary (ZM) buttress being the most popular fixation point (90%). ZM buttress and frontozygomatic (FZ) suture were the commonest choices for two-point fixations (70%). Buccal sulcus incision was used for ZM access in all cases. For FZ access, upper blepharoplasty incision was the most common (56%). For infra-orbital margin access, transconjunctival incision was the most common (75%). There was no significant association between number of fixation points and presence of associated injuries, impact of injury, or time to operation. There were no post-operative complications. Conclusion: A greater proportion of patients in our cohort were successfully treated with one point fixation compared to the literature, and fewer patients underwent orbital floor exploration and repair in our cohort compared to the literature. This study highlights the ongoing variation in the surgical management of ZMC fractures.展开更多
AIM: To evaluate the effectiveness and safety of complex orbital fracture reconstruction with titanium implants. METHODS: A retrospective review of 46 patients treated with complex orbital fractures reconstruction usi...AIM: To evaluate the effectiveness and safety of complex orbital fracture reconstruction with titanium implants. METHODS: A retrospective review of 46 patients treated with complex orbital fractures reconstruction using titanium implants from January 2005 to December 2008 was conducted. The following data were recorded: age, gender, mechanism of injury, preoperative and postoperative orbital CT, visual acuity, diplopia, ocular motility and Hertel exophthalmometer. RESULTS: The most common cause was motor vehicle accident (47.8%), followed by industrial injury (30.4%). All patients had improved appearance after operation and CT scan at one week after operation showed the fracture defects of orbit and neighboring areas had been reconstructed. Forty-six cases had various degrees of enophthalmos before operation. Among them, 32 cases were completely corrected, 11 cases improved obviously and 3 cases had no improvement after operation. Thirty-six patients with visual acuity =20/60 revealed diplopia of various degrees, including 26 patients had diplopia in right ahead and/or reading positions. At the sixth month after operation, diplopia disappeared in five patients, 7 patients still had diplopia in right ahead and/or reading positions, 14 patients had diplopia in positions rather than right ahead and reading positions (<20 degrees) and ten patients had diplopia only at peripheral gazing (>20 degrees). All patients had various degrees of ocular motility disorders before operation. At the sixth month after operation, eyeball movement disorder disappeared in 9 patients, 31 patients showed improvement and 6 patients had no improvement. Complications of implant infection, rejection and displacement were not reported after operation. CONCLUSION: The application of titanium implants in the repair of complex orbital fractures greatly improves the appearance and functional results, which is a favorable material for plastic surgery of complex orbital fracture.展开更多
Objective: Acetabular fractures are common injuries in Iran. We assess the functional outcome of open reduction and internal fixation management of displaced Complex acetabular fractures. Materials and Methods: We ana...Objective: Acetabular fractures are common injuries in Iran. We assess the functional outcome of open reduction and internal fixation management of displaced Complex acetabular fractures. Materials and Methods: We analyzed a case series of patients with open reduction and internal fixation (ORIF) for complex acetabular fractures. Two hundred patients (132 men, 68 women) in four age groups including with a mean age of 43.39 ± 6.18 years (range 20 - 59 years) and a mean follow-up of 82.34 ± 12.48 months (range 18 - 109 months) met the inclusion criteria. Functional outcome at final follow-up was graded assessed according to Harris score. Factors affecting were defined. Results: Anatomic reduction was achieved in 192 hips, imperfect in 8 and poor in none. Radiological outcome revealed excellent results in 128 (64%) hips, good in eight, fair in five and none in poor. Harris score were excellent in 139 (69.5%) hips, good in 43 (21.5%) and fair in 18 (9%) and poor in none. The anatomical reduction results had a favorable final functional outcome. (0.003) However, BMI (P Conclusion: Optimal functional and radiological outcomes have been achieved with anatomic postoperative reduction. Also experience of specialist, on time surgery and good recovery lead to receiving excellent functional outcome with at least complications.展开更多
基金funded by the National Natural Science Foundation of China(No.51974268)Open Fund of Key Laboratory of Ministry of Education for Improving Oil and Gas Recovery(NEPUEOR-2022-03)Research and Innovation Fund for Graduate Students of Southwest Petroleum University(No.2022KYCX005)。
文摘The oil production of the multi-fractured horizontal wells(MFHWs) declines quickly in unconventional oil reservoirs due to the fast depletion of natural energy. Gas injection has been acknowledged as an effective method to improve oil recovery factor from unconventional oil reservoirs. Hydrocarbon gas huff-n-puff becomes preferable when the CO_(2) source is limited. However, the impact of complex fracture networks and well interference on the EOR performance of multiple MFHWs is still unclear. The optimal gas huff-n-puff parameters are significant for enhancing oil recovery. This work aims to optimize the hydrocarbon gas injection and production parameters for multiple MFHWs with complex fracture networks in unconventional oil reservoirs. Firstly, the numerical model based on unstructured grids is developed to characterize the complex fracture networks and capture the dynamic fracture features.Secondly, the PVT phase behavior simulation was carried out to provide the fluid model for numerical simulation. Thirdly, the optimal parameters for hydrocarbon gas huff-n-puff were obtained. Finally, the dominant factors of hydrocarbon gas huff-n-puff under complex fracture networks are obtained by fuzzy mathematical method. Results reveal that the current pressure of hydrocarbon gas injection can achieve miscible displacement. The optimal injection and production parameters are obtained by single-factor analysis to analyze the effect of individual parameter. Gas injection time is the dominant factor of hydrocarbon gas huff-n-puff in unconventional oil reservoirs with complex fracture networks. This work can offer engineers guidance for hydrocarbon gas huff-n-puff of multiple MFHWs considering the complex fracture networks.
基金financial support of the National Natural Science Foundation of China(Grant No.52074332)express their gratitude to project ZR2020YQ36 supported by Shandong Provincial Science Fund for Excellent Young Scholars。
文摘Hydraulic fracturing is a key technology for the development of unconventional hydrocarbon resources.The proppant placement morphology determines the fracture conductivity,thus affecting the reservoir stimulation effect.In this paper,the proppant migration and placement within complex fractures was studied by considering the fracture wall roughness through computational fluid mechanics-discrete element method(CFD-DEM)in numerical simulation,which is a key approach to study the proppant migration and placement.The results show that the proppant placement non-uniformity,proppant migration capacity,and proppant volume filled in the far-end and the secondary branched fracture are enhanced within the rough fracture compared with those within smooth fractures.The proppant migration capacity is increased within the fracture at low inclination angles(<60°)and low approach angles(<90°),and the proppant placement area is larger in the inclined fracture than that in the vertical fracture.The rise of injection rate and fracturing fluid viscosity causes more proppants migrate to far-end or secondary fractures,resulting in a non-proppant area within the near-wellbore fracture.An increase by 1.3 times in the injection rate and 3 times in the fracturing fluid viscosity leads to a decrease by 26.6%and 27%,respectively,in the proppant placement area within the near-wellbore fracture.The staged injection with small size proppants followed by large size proppants increases the proppant placement area in the primary fracture by 13%-26%,and that with large size proppants followed by small size proppants increases the proppant placement area by 19%-25%,which is due to that the latter method facilitates filling of the secondary branched fracture.The injection location mainly affects the proppant filling degree within the near-wellbore fractures.Compared with the upper injection,the middle and lower injection is not beneficial to filling of proppants within the near-wellbore fracture.
基金The authors are grateful to the financial support from China Postdoctoral Science Foundation(2022M712645)Opening Fund of Key Laboratory of Enhanced Oil Recovery(Northeast Petroleum University),Ministry of Education(NEPU-EOR-2021-03).
文摘Severe well interference through complex fracture networks(CFNs)can be observed among multi-well pads in low permeability reservoirs.The well interference analysis between multi-fractured horizontal wells(MFHWs)is vitally important for reservoir effective development.Well interference has been historically investigated by pressure transient analysis,while it has shown that rate transient analysis has great potential in well interference diagnosis.However,the impact of complex fracture networks(CFNs)on rate transient behavior of parent well and child well in unconventional reservoirs is still not clear.To further investigate,this paper develops an integrated approach combining pressure and rate transient analysis for well interference diagnosis considering CFNs.To perform multi-well simulation considering CFNs,non-intrusive embedded discrete fracture model approach was applied for coupling fracture with reservoir models.The impact of CFN including natural fractures and frac-hits on pressure and rate transient behavior in multi-well system was investigated.On a logelog plot,interference flow and compound linear flow are two new flow regimes caused by nearby producers.When both NFs and frac-hits are present in the reservoir,frac-hits have a greater impact on well#1 which contains frac-hits,and NFs have greater impact on well#3 which does not have frac-hits.For all well producing circumstances,it might be challenging to see divergence during pseudosteady state flow brought on by frac-hits on the logelog plot.Besides,when NFs occur,reservoir depletion becomes noticeable in comparison to frac-hits in pressure distribution.Application of this integrated approach demonstrates that it works well to characterize the well interference among different multi-fractured horizontal wells in a well pad.Better reservoir evaluation can be acquired based on the new features observed in the novel model,demonstrating the practicability of the proposed approach.The findings of this study can help for better evaluating well interference degree in multi-well systems combing PTA and RTA,which can reduce the uncertainty and improve the accuracy of the well interference analysis based on both field pressure and rate data.
基金supported by the National Natural Science Foundation of China(Grant Nos.51722406,61573018 and 51874335)the Shandong Provincial Natural Science Foundation(Grant JQ201808)+1 种基金the Fundamental Research Funds for the Central Universities(Grant 18CX02097A)the National Science and Technology Major Project of China(Grant 2016ZX05025001-006)
文摘In practical development of unconventional reservoirs,fracture networks are a highly conductive transport media for subsurface fluid flow.Therefore,it is crucial to clearly determine the fracture properties used in production forecast.However,it is different to calibrate the properties of fracture networks because it is an inverse problem with multi-patterns and highcomplexity of fracture distribution and inherent defect of multiplicity of solution.In this paper,in order to solve the problem,the complex fracture model is divided into two sub-systems,namely"Pattern A"and"Pattern B."In addition,the generation method is grouped into two categories.Firstly,we construct each sub-system based on the probability density function of the fracture properties.Secondly,we recombine the sub-systems into an integral complex fracture system.Based on the generation mechanism,the estimation of the complex fracture from dynamic performance and observation data can be solved as an inverse problem.In this study,the Bayesian formulation is used to quantify the uncertainty of fracture properties.To minimize observation data misfit immediately as it occurs,we optimize the updated properties by a simultaneous perturbation stochastic algorithm which requires only two measurements of the loss function.In numerical experiments,we firstly visualize that small-scale fractures significantly contribute to the flow simulation.Then,we demonstrate the suitability and effectiveness of the Bayesian formulation for calibrating the complex fracture model in the following simulation.
基金supported by National Natural Science Foundation of China(No.51674279)China Postdoctoral Science Foundation(No.2016M602227)a grant from National Science and Technology Major Project(No.2017ZX05049-006)
文摘The paper presents a novel hydraulic fracturing model for the characterization and simulation of the complex fracture network in shale gas reservoirs. We go beyond the existing method that uses planar or orthogonal conjugate fractures for representing the ＇＇complexity＇＇ of the network. Bifurcation of fractures is performed utilizing the Lindenmayer system based on fractal geometry to describe the fracture propagation pattern, density and network connectivity. Four controlling parameters are proposed to describe the details of complex fractures and stimulated reservoir volume（SRV）. The results show that due to the multilevel feature of fractal fractures, the model could provide a simple method for contributing reservoir volume calibration. The primary-and second-stage fracture networks across the overall SRV are the main contributions to the production, while the induced fracture network just contributes another 20% in the late producing period. We also conduct simulation with respect to different refracturing cases and find that increasing the complexity of the fracture network provides better performance than only enhancing the fracture conductivity.
基金supported by the Science Foundation for Young Scientists of National Natural Science Foundation of China,“Study on the Diversion and Distribution Mechanisms of Proppant for“Multi-Stage And Multi-Cluster”Fracturing by Shale Horizontal Well”(Grant No.51604050)the Chongqing Science and Technology Innovation Project for People's Livelihood,“Research&Development of Instruments for Evaluating the Migration and Distribution of Proppant for“Multi-Stage And Multi-Cluster”Fracturing by Shale Horizontal Well”(Grant No.cstc2016shmszx90003).
文摘In this paper,a large-scale experimental system was established to identify the migration and distribution laws of complex fracture proppant in shale reservoir volume fracturing.With this system,the effects of secondary fracture angle,fluid displacement,proppant concentration and size,fracturing fluid viscosity and other factors on the migration and distribution of proppant were tested,and the migration and distribution of proppant in primary/secondary fractures were analyzed.The following results were obtained.First,the fluid flow pattern in fractures transforms gradually from laminar flow into turbulent flow with the increase of fracture supporting height.Second,the migration modes of proppant in fractures mainly include suspended migration and gliding migration.Third,the distribution form of proppant in primary fractures before branching is related to secondary fracture angle,fluid displacement and proppant concentration and size,among which the fluid displacement is the most important factor.Fourth,the mass ratio of proppant in primary fractures after branching is proportional to the secondary fracture angle,fluid displacement,fracturing fluid viscosity and proppant concentration and size,and is inversely proportional to the flow ratio between secondary fractures and primary fractures.Fifth,the mass ratio of proppant in secondary fractures after branching is proportional to fluid displacement,fracturing fluid viscosity and flow ratio between secondary fractures and primary fractures,and is inversely proportional to secondary fracture angle and proppant concentration and size.Sixth,the angle at the leading edge of proppant bank in the primary fractures after branching is proportional to the proppant concentration and size and the flow ratio between secondary fractures and primary fractures,but is inversely proportional to secondary fracture angle,fluid displacement and fracturing fluid viscosity.Seventh,the angle at the leading edge of proppant bank in the secondary fractures after branching is proportional to the secondary fracture angle and the proppant concentration and size,but is inversely proportional to the fluid displacement,fracturing fluid viscosity and flow ratio between secondary fractures and primary fractures.In conclusion,the research results can provide a theoretical support for proppant optimization and program design of shale reservoir volume fracturing.
文摘When hydraulic fractures intersect with natural fractures,the geometry and complexity of a fracture network are determined by the initiation and propagation pattern which is affected by a number of factors.Based on the fracture mechanics,the criterion for initiation and propagation of a fracture was introduced to analyze the tendency of a propagating angle and factors affecting propagating pressure.On this basis,a mathematic model with a complex fracture network was established to investigate how the fracture network form changes with different parameters,including rock mechanics,in-situ stress distribution,fracture properties,and frac treatment parameters.The solving process of this model was accelerated by classifying the calculation nodes on the extending direction of the fracture by equal pressure gradients,and solving the geometrical parameters prior to the iteration fitting flow distribution.With the initiation and propagation criterion as the bases for the propagation of branch fractures,this method decreased the iteration times through eliminating the fitting of the fracture length in conventional 3D fracture simulation.The simulation results indicated that the formation with abundant natural fractures and smaller in-situ stress difference is sufficient conditions for fracture network development.If the pressure in the hydraulic fractures can be kept at a high level by temporary sealing or diversion,the branch fractures will propagate further with minor curvature radius,thus enlarging the reservoir stimulation area.The simulated shape of fracture network can be well matched with the field microseismic mapping in data point range and distribution density,validating the accuracy of this model.
文摘Multi-stage volume fracturing of horizontal wells is the main means to develop tight gas reservoirs.Complex fracture networks of various shapes are generated around the wellbore after volume fracturing.At present,however,most of the well test models suitable for fracturing horizontal wells take all hydraulic fractures as single main fractures,which results in a large error between well test interpretation result and actual situation.As a result,the fracture network characteristic parameters of the stimulated areas cannot be obtained accurately.To this end,a well test model for complex fracture networks in tight-gas fracturing horizontal wells was established on the basis of the non-structural discrete fracture model.Then,this model was solved by using thefinite element method with combined triangular elements and linear elements.And accordingly,the well test type curves of a horizontal well under different fracture network patterns(rectangular,elliptical and hyperbolic)were prepared.Based on this,well test type curves were analyzed from the aspects of characteristics and influential factors and were compared with those obtained from the conventional single-fracture model.Finally,the new model was applied in well test interpretation of one multi-stage volume fracturing horizontal well in the gas reservoir of Permian Shan 1 formation in the Qingyang Gas Field of the Ordos Basin.And the following research results were obtained.First,the biggest difference of well test type curve between the fracture network model and the conventional single-fracture model occurs in the early stage,the characteristics offirst linearflow regime are replaced with the characteristics of pseudo-radialflow regime in the stimulated area.Second,the end time of the pseudo-radialflow regime in the stimulated area is mainly dominated by the size and shape of the stimulated area.The larger the stimulated area is,the longer the pseudo-radialflow regime lasts.As the shape of the stimulated area approaches to be elongated,the characteristics of the well test type curve obtained by the new model are more consistent with those by the single-fracture model.Third,the pressure derivative value of the pseudo-radialflow regime in the stimulated area is mainly dependent on the conductivity and density of the fracture network.The higher the density or the conductivity of fracture network in the stimulated area is,the earlier the wellbore storage effect regime ends,the lower the pressure derivative value of the pseudo-radialflow regime in the stimulated area is and the more obvious the characteristics of the horizontal line are.In conclusion,case study results confirm that the new model is reliable and practical and can provide accurate reservoir parameters as well as the size of the effectively stimulated area by volume fracturing and the conductivity of fracture network,which is conducive to evaluating the stimulation effect of volume fracturing and predicting the postfrac production performance.
基金This work is supported by Open Fund Project“Study on Multiphase Flow Semi-Analytical Method for Horizontal Wells of Continental Shale Condensate Gas”of Sinopec Key Laboratory of Shale Oil/Gas Exploration and Production Technology.
文摘Well interference has become a common phenomenon with the increasing scale of horizontal well fracturing.Recent studies on well interference in horizontal wells do not properly reflect the physical model of the postfracturing well groups and the realistic fracturing process of infill wells.Establishing the correspondence between well interference causative factors and manifestations is of great significance for infill well deployment and secondary oil recovery.In this work,we develop a numerical model that considers low velocity non-Darcy seepage inshale reservoirs to study the inter-well interferencephenomenon that occurs in theSantanghufield,andconstruct an explicit hydraulic fracture and complex natural fracture network model with an embedded discrete fracture model,focusing on the effect of fracture network morphology on well interactions.The model also considers a multi-segment wellbore model to accommodate the effect of inter-well crossflow on wellbore tubular flow.The changes in formation pressure and water saturation during fracturing are performed by controlling the injection pressure and water injection rate.The result shows that the shape of the fracture network generated by the infill well with the old well determines the subsequent fluid and oil-increasing performance of the disturbed well.The synergistic production or competitive relationship formed by fractures with different connectivity between the two wells determines the positive and negative effects of the interference.The paper also investigates the adaptation study of water injection huff and puff schemes for well groups with different connectivity,and demonstrated a potential yield increase of up to 10.85%under adaptation injection.This method of identifying well interference based on the production dynamics of affected wells and the subsequent corresponding water injection method provides valuable references for the selection of secondary oil recovery measures.
文摘In this paper,a series of specific studies were carried out to investigate the complex form of fracture networks and figure out the multi-scale flowing laws of nano/micro poresecomplex fracture networks-wellbore during the development of shale reservoirs by means of horizontal well fracturing.First,hydraulic fractures were induced by means of Brazilian splitting tests.Second,the forms of the hydraulic fractures inside the rock samples were observed by means of X-ray CT scanning to measure the opening of hydraulic fractures.Third,based on the multi-scale unified flowing model,morphological description of fractures and gas flowing mechanism in the matrixecomplex fracture networkewellbore,the productivity equation of single-stage horizontal well fracturing which includes diffusion,slipping and desorption was established.And fourthly,a productivity prediction model of horizontal well multi-stage fracturing in the shale reservoir was established considering the interference between the multi-stage fracturing zones and the pressure drop in the horizontal wellbore.The following results were obtained.First,hydraulic fractures are in the form of a complex network.Second,the measured opening of hydraulic fractures is in the range of 4.25-453 mm,averaging 112 mm.Third,shale gas flowing in different shapes of fracture networks follows different nonlinear flowing laws.Forth,as the fracture density in the strongly stimulated zones rises and the distribution range of the hydraulic fractures in strongly/weakly stimulated zones enlarges,gas production increases gradually.As the interference occurs in the flowing zones of fracture networks between fractured sections,the increasing amplitude of gas production rates decreases.Fifth,when the length of a simulated horizontal well is 1500 m and the half length of a fracture network in the strongly stimulated zone is 100 m,the productivity effect of stage 10 fracturing is the best.Therefore,it is necessary to control fracturing degree reasonably and optimize fracturing parameters,so as to provide a theoretical support for the optimization design of shale gas reservoir fracturing.
基金funded by National Natural Science Founda-tion of China(Grant No.51804258,51974255,52274007)Natural Science Basic Research Program of Shaanxi Province(Grant No.2023-JC-YB-414)the Youth Innovation Team of Shaanxi Universities.Scientific Research Program Funded by Shaanxi ProvincialEducation Department(Program No.22JS029).
文摘Horizontal well and volume fracturing technology are the key technologies to develop unconventional reservoirs.Tight reservoir is belonging to multi-scale seepage mediaafter fracturing,and theflow offluid in it is extremely complicated.In this paper,based on the boundary element method(BEM),the seepage model of horizontal wells with complex fracture networks in irregular boundary reservoir is established for thefirst time.The model takes into account the influence of irregular reservoir boundary,dual media,complex fracture network and interference of multiple wells on horizontal well seepage.Using this model,the sensitivity analysis of wellbore storage coefficient,skin factor,fracture permeability and interporosity transfer coefficient is carried out.The model expands the application scope of BEM in thefield of seepage simulation of unconventional oil and gas reservoirs and provides theoretical guidance for the development of tight oil reservoirs.
基金Supported by the National Natural Science Foundation of China(52274014,52421002).
文摘By integrating laboratory physical modeling experiments with machine learning-based analysis of dominant factors,this study explored the feasibility of pulse hydraulic fracturing(PHF)in deep coal rocks and revealed the fracture propagation patterns and the mechanisms of pulsating loading in the process.The results show that PHF induces fatigue damage in coal matrix,significantly reducing breakdown pressure and increasing fracture network volume.Lower vertical stress differential coefficient(less than 0.31),lower peak pressure ratio(less than 0.9),higher horizontal stress differential coefficient(greater than 0.13),higher pulse amplitude ratio(greater than or equal to 0.5)and higher pulse frequency(greater than or equal to 3 Hz)effectively decrease the breakdown pressure.Conversely,higher vertical stress differential coefficient(greater than or equal to 0.31),higher pulse amplitude ratio(greater than or equal to 0.5),lower horizontal stress differential coefficient(less than or equal to 0.13),lower peak pressure ratio(less than 0.9),and lower pulse frequency(less than 3 Hz)promote the formation of a complex fracture network.Vertical stress and peak pressure are the most critical geological and engineering parameters affecting the stimulation effectiveness of PHF.The dominant mechanism varies with coal rank due to differences in geomechanical characteristics and natural fracture development.Low-rank coal primarily exhibits matrix strength degradation.High-rank coal mainly involves the activation of natural fractures and bedding planes.Medium-rank coal shows a coexistence of matrix strength degradation and micro-fracture connectivity.The PHF forms complex fracture networks through the dual mechanism of matrix strength degradation and fracture network connectivity enhancement.
文摘This study investigated the micro-sliding frictional behavior of shale in fracturing fluids under varying operational conditions using Chang 7 shale oil reservoir core samples.Through systematic micro-sliding friction experiments,the characteristics and governing mechanisms of shale friction were elucidated.Complementary analyses were conducted to characterize the mineral composition,petrophysical properties,and micromorphology of the shale samples,providing insights into the relationship between microscopic structure and frictional response.In this paper,the characteristics and variation law of shale micro-sliding friction under different types of graphite materials as additives in LGF-80(Low-damage Guar Fluid)oil flooding recoverable fracturing fluid system were mainly studied.In addition,the finite element numerical simulation experiment of hydraulic fracturing was adopted to study the influence of the friction coefficient of natural fracture surfaces on fracture propagation and formation of the fracture network.The geometric complexity of fracture networks was systematically quantified under varying frictional coefficients of natural fracture surfaces through multi-parametric characterization and morphometric analysis.The research results show that graphite micro-particles reduce friction and drag.Based on this,this paper proposes a new idea of graphite micro-particles as an additive in the LGF-80 oil flooding recoverable fracturing fluid system to reduce friction on the fracture surface.
文摘Patients suffering from zygomatic complex fractures always present facial deformity and dyslunctions, and thereafter develop psychological and physiological problems. It is really hard to get an ideal prog- nosis for the zygomatic complex fractures because of the complicated anatomical structures. Computer- assisted surgery techniques, as the new emerging auxiliary methods, can optimize the surgical protocol, predict operation outcomes, and improve the accuracy and quality of the operation. Meanwhile the postoperative complications can be reduced effectively. This review aims to provide a comprehensive overview of the application of computer-assisted surgery techniques in the management of zygomatic complex fractures.
文摘This study extends an integrated field characterization in Eagle Ford by optimizing the numerical reservoir simulation of highly representative complex fractured systems through embedded discrete fracture modeling(EDFM). The bottom-hole flowing pressure was history-matched and the field production was forecasted after screening complex fracture scenarios with more than 100 000 fracture planes based on their propped-type. This work provided a greater understanding of the impact of complex-fractures proppant efficiency on the production. After compaction tables were included for each propped-type fracture group, the estimated pressure depletion showed that the effective drainage area can be smaller than the complex fracture network if modeled and screened by the EDFM method rather than unstructured gridding technique. The essential novel value of this work is the capability to couple EDFM with third-party fracture propagation simulation automatically, considering proppant intensity variation along the complex fractured systems. Thus, this work is pioneer to model complex fracture propagation and well interference accurately from fracture diagnostics and pseudo 3 D fracture propagation outcomes for multiple full wellbores to capture well completion effectiveness after myriads of sharper field simulation cases with EDFM.
基金supported by the National Natural Science Foundation of China(No.52174038 and No.52004307)China Petroleum Science and Technology Project-Major Project-Research on Tight Oil-Shale Oil Reservoir Engineering Methods and Key Technologies in Ordos Basin(No.ZLZX2020-02-04)Science Foundation of China University of Petroleum,Beijing(No.2462018YJRC015)。
文摘Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and fracture structure lead to complex multiphase flow,comprehensively considering multiple mechanisms is crucial for development and CO_(2) storage in fractured shale reservoirs.In this paper,a multi-mechanism coupled model is developed by MATLAB.Compared to the traditional Eclipse300 and MATLAB Reservoir Simulation Toolbox(MRST),this model considers the impact of pore structure on fluid phase behavior by the modified Peng—Robinson equation of state(PR-EOS),and the effect simultaneously radiate to Maxwell—Stefan(M—S)diffusion,stress sensitivity,the nano-confinement(NC)effect.Moreover,a modified embedded discrete fracture model(EDFM)is used to model the complex fractures,which optimizes connection types and half-transmissibility calculation approaches between non-neighboring connections(NNCs).The full implicit equation adopts the finite volume method(FVM)and Newton—Raphson iteration for discretization and solution.The model verification with the Eclipse300 and MRST is satisfactory.The results show that the interaction between the mechanisms significantly affects the production performance and storage characteristics.The effect of molecular diffusion may be overestimated in oil-dominated(liquid-dominated)shale reservoirs.The well spacing and injection gas rate are the most crucial factors affecting the production by sensitivity analysis.Moreover,the potential gas invasion risk is mentioned.This model provides a reliable theoretical basis for CO_(2)-EOR and sequestration in shale oil reservoirs.
基金supported the National Natural Science Foundation of China(No.52004033,51922007,and 51874044).
文摘Efficient flow simulation and optimization methods of hydraulic fracture morphology in unconventional reservoirs are effective ways to enhance oil/gas recovery.Based on the connection element method(CEM)and distribution of stimulated reservoir volume,the complex hydraulic fracture morphology was accurately described using heterogeneous node connection system.Then a new fracture connection element method(FCEM)for fluid flow in stimulated unconventional reservoirs with complex hydraulic fracture morphology was proposed.In the proposed FCEM,the arrangement of dense nodes in the stimulated area and sparse nodes in the unstimulated area ensures the calculation accuracy and efficiency.The key parameter,transmissibility,was also modified according to the strong heterogeneity of stimulated reservoirs.The finite difference and semi-analytical tracking were used to accurately solve the pressure and saturation distribution between nodes.The FCEM is validated by comparing with traditional numerical simulation method,and the results show that the bottom hole pressure simulated by the FCEM is consistent with the results from traditional numerical simulation method,and the matching rate is larger than 95%.The proposed FCEM was also used in the optimization of fracturing parameters by coupling the hydraulic fracture propagation method and intelligent optimization algorithm.The integrated intelligent optimization approach for multi-parameters,such as perforation number,perforation location,and displacement in hydraulic fracturing is proposed.The proposed approach was applied in a shale gas reservoir,and the result shows that the optimized perforation location and morphology distribution are related to the distribution of porosity/permeability.When the perforation location and displacement are optimized with the same fracture number,NPV increases by 70.58%,which greatly improves the economic benefits of unconventional reservoirs.This work provides a new way for flow simulation and optimization of hydraulic fracture morphology of multi-fractured horizontal wells in unconventional reservoirs.
文摘Aim: To analyse the epidemiology, aetiology, and surgical management of zygomatic complex (ZMC) fractures in our major trauma centre, and to compare the number and location of fixation points and surgical access in our patient cohort with the literature. Methods: Retrospective analysis of all operative cases (Open Reduction and Internal Fixation) of zygomatic complex fractures over a one year period (2016). Results: A greater proportion of patients in our cohort (54%) were treated with one-point fixation compared to the literature, with the zygomaticomaxillary (ZM) buttress being the most popular fixation point (90%). ZM buttress and frontozygomatic (FZ) suture were the commonest choices for two-point fixations (70%). Buccal sulcus incision was used for ZM access in all cases. For FZ access, upper blepharoplasty incision was the most common (56%). For infra-orbital margin access, transconjunctival incision was the most common (75%). There was no significant association between number of fixation points and presence of associated injuries, impact of injury, or time to operation. There were no post-operative complications. Conclusion: A greater proportion of patients in our cohort were successfully treated with one point fixation compared to the literature, and fewer patients underwent orbital floor exploration and repair in our cohort compared to the literature. This study highlights the ongoing variation in the surgical management of ZMC fractures.
文摘AIM: To evaluate the effectiveness and safety of complex orbital fracture reconstruction with titanium implants. METHODS: A retrospective review of 46 patients treated with complex orbital fractures reconstruction using titanium implants from January 2005 to December 2008 was conducted. The following data were recorded: age, gender, mechanism of injury, preoperative and postoperative orbital CT, visual acuity, diplopia, ocular motility and Hertel exophthalmometer. RESULTS: The most common cause was motor vehicle accident (47.8%), followed by industrial injury (30.4%). All patients had improved appearance after operation and CT scan at one week after operation showed the fracture defects of orbit and neighboring areas had been reconstructed. Forty-six cases had various degrees of enophthalmos before operation. Among them, 32 cases were completely corrected, 11 cases improved obviously and 3 cases had no improvement after operation. Thirty-six patients with visual acuity =20/60 revealed diplopia of various degrees, including 26 patients had diplopia in right ahead and/or reading positions. At the sixth month after operation, diplopia disappeared in five patients, 7 patients still had diplopia in right ahead and/or reading positions, 14 patients had diplopia in positions rather than right ahead and reading positions (<20 degrees) and ten patients had diplopia only at peripheral gazing (>20 degrees). All patients had various degrees of ocular motility disorders before operation. At the sixth month after operation, eyeball movement disorder disappeared in 9 patients, 31 patients showed improvement and 6 patients had no improvement. Complications of implant infection, rejection and displacement were not reported after operation. CONCLUSION: The application of titanium implants in the repair of complex orbital fractures greatly improves the appearance and functional results, which is a favorable material for plastic surgery of complex orbital fracture.
文摘Objective: Acetabular fractures are common injuries in Iran. We assess the functional outcome of open reduction and internal fixation management of displaced Complex acetabular fractures. Materials and Methods: We analyzed a case series of patients with open reduction and internal fixation (ORIF) for complex acetabular fractures. Two hundred patients (132 men, 68 women) in four age groups including with a mean age of 43.39 ± 6.18 years (range 20 - 59 years) and a mean follow-up of 82.34 ± 12.48 months (range 18 - 109 months) met the inclusion criteria. Functional outcome at final follow-up was graded assessed according to Harris score. Factors affecting were defined. Results: Anatomic reduction was achieved in 192 hips, imperfect in 8 and poor in none. Radiological outcome revealed excellent results in 128 (64%) hips, good in eight, fair in five and none in poor. Harris score were excellent in 139 (69.5%) hips, good in 43 (21.5%) and fair in 18 (9%) and poor in none. The anatomical reduction results had a favorable final functional outcome. (0.003) However, BMI (P Conclusion: Optimal functional and radiological outcomes have been achieved with anatomic postoperative reduction. Also experience of specialist, on time surgery and good recovery lead to receiving excellent functional outcome with at least complications.
