This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture ...This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.展开更多
Injection rate is crucial for determining the hydraulic fracturing effectiveness;however,the effects of the injection rate on the pore and fracture structure(PFS)and fluid infiltration during injection pressurization ...Injection rate is crucial for determining the hydraulic fracturing effectiveness;however,the effects of the injection rate on the pore and fracture structure(PFS)and fluid infiltration during injection pressurization have rarely been explored.In this study,the cylindrical sandstone samples were hydraulically fractured at various injection rates on a self-developed integrated nuclear magnetic resonance(NMR)and hydraulic fracturing experimental system.The results show that low injection rates predominantly resulted in macropore-scale damage by creating intergranular cracks,whereas high injection rates facilitated micropore-scale damage,probably owing to the adsorption swelling effect of clay minerals within pores.Additionally,the water contents of the samples with low injection rates exhibited a continuous increase,whereas those of the samples with high injection rates initially increased and subsequently stabilized.Magnetic resonance imaging(MRI)indicated that fluid infiltration during the fracturing process exhibited high anisotropy owing to the inherent heterogeneous PFS distributions around the wellbore.Moreover,a primary fluid infiltration path exists that aligns with the initiation direction of the hydraulic fractures.However,the fluid infiltration damage distance along the hydraulic fracture direction decreased with increasing injection rate,whereas the fluid infiltration damage distance perpendicular to the hydraulic fracture direction was approximately equal to the characteristic length,regardless of the injection rate.Finally,we recommend using the pore damage during fluid pressurization as the basis for selecting the proppant size and employing a primary fluid infiltration path to predict hydraulic fracture initiation.These findings provide valuable insights into the design of hydraulic fracturing in tight gas reservoirs.展开更多
The long-term stability of CO_(2) storage represents a pivotal challenge in geological CO_(2) storage(CGS),particularly within deep saline aquifers characterized by complex fault-block systems.While the injection site...The long-term stability of CO_(2) storage represents a pivotal challenge in geological CO_(2) storage(CGS),particularly within deep saline aquifers characterized by complex fault-block systems.While the injection sites and rate under different fault structures will directly affect the CO_(2) storage effect and the risk of leakage.This study investigates the Gaoyou Sag in the Subei Basin,a representative fault-block reservoir,through an integrated numerical-experimental approach.A three-dimensional simulation model incorporating multiphase flow dynamics was developed to characterize subsurface CO_(2) transport and dissolution processes.A novel fault seal capacity evaluation framework was proposed,integrating three critical geological indices(fault throw/reservoir thickness/caprock thicknesses)with the coupling of formation physical properties,temperature,and pressure for the rational selection of injection sites and rates.The results show that Optimal storage performance is observed when the fault throw is lower than the reservoir and caprock thicknesses.Furthermore,higher temperature and pressure promote the dissolution and diffusion of CO_(2),while compared to the structural form of faults,the physical properties of faults have a more significant effect on CO_(2) leakage.The larger reservoir space and the presence of an interlayer reduce the risk of CO_(2) leakage,and augmenting storage potential.Decreasing the injection rate increases the proportion of dissolved CO_(2),thereby enhancing the safety of CO_(2) storage.展开更多
Resistivity will have different response characteristics to the hydraulic fracture propagation process. In this work, a resistivity testing system for hydraulic fracturing specimens was established. Resistivity and ac...Resistivity will have different response characteristics to the hydraulic fracture propagation process. In this work, a resistivity testing system for hydraulic fracturing specimens was established. Resistivity and acoustic emission(AE) information were jointly analysed to determine the dynamic response characteristics of resistivity during hydraulic fracture propagation. The results show that the water and fracture exert a competitive influence on the connection structure of the circuit, and there are two significant peak resistivity points in the curve, presenting a double peak therein. The peak resistivity data of the specimen with a larger fracture area are much different from the initial value. With the increase of the rate of injection, the range of variation of the highest value that can be reached with the specimen resistivity decreases. High resistivity rates or high resistivity fluctuations exhibit rapid a release of fracture energy. The fracture failure mode dominated by shear fractures makes the formation produce a “series+parallel” electrical connection structure;a calculation model of formation resistivity based on shear and tensile failure was proposed to characterize the proportion of different types of hydraulic fractures and elucidate the control effect of matrix resistivity on the electrical performance of the overall circuit structure.展开更多
This paper investigates the effect of both unequal injection rates and different hopping rates on two-lane asymmetric simple exclusion processes(ASEPs) with asymmetric coupling. When the hopping rates of both lanes ar...This paper investigates the effect of both unequal injection rates and different hopping rates on two-lane asymmetric simple exclusion processes(ASEPs) with asymmetric coupling. When the hopping rates of both lanes are different, the system includes six steady phases, however, when the hopping rates of both lanes are same, the seventh phase(MC, MC) will exist in the system. Interestingly, with different hopping rates of both lanes, the densities of the system cannot be influenced by the non-zero vertical transition rate. Our theoretical arguments are in well agreement with extensively performed Monte Carlo simulations.展开更多
Detailed information is provided for the design and construction of nitrogen drilling in a coal seam.Two prototype wells are considered.The Guo model is used to calculate the required minimum gas injection rate,while ...Detailed information is provided for the design and construction of nitrogen drilling in a coal seam.Two prototype wells are considered.The Guo model is used to calculate the required minimum gas injection rate,while the Finnie,Sommerfeld,and Tulsa models are exploited to estimate the ensuing erosion occurring in pipe strings.The calculated minimum gas injection rates are 67.4 m^(3)/min(with water)and 49.4 m^(3)/min(without water),and the actual field of use is 90–120 m^(3)/min.The difference between the calculated injection pressure and the field value is 6.5%–15.2%(formation with water)and 0.65%–7.32%(formation without water).The results show that the Guo model can more precisely represent the situation of the no water formation in the nitrogen drilling of a coal seam.The Finnie,Sommerfeld,and Tulsa models have different sensitivities to cutting densities,particle size,impact velocity and angle,and pipe string hardness.展开更多
The goal of net-zero carbon emissions has led to widespread interest in lowering carbon dioxide(CO_(2))emissions.At the same time,the oil and gas industry seeks to enhance oil recovery(EOR)techniques to meet growing d...The goal of net-zero carbon emissions has led to widespread interest in lowering carbon dioxide(CO_(2))emissions.At the same time,the oil and gas industry seeks to enhance oil recovery(EOR)techniques to meet growing demand.CO_(2) flooding,a key EOR method,offers a dual benefit:reducing CO_(2) emissions and enhancing oil recovery.This study investigates the impact of injection rate and bottom hole pressure(BHP)on CO_(2) injection performance using the Nexus reservoir simulator,a novel application in CO_(2)-EOR research.To the best of the author's knowledge,there is no previous research published in which the researchers used the Nexus reservoir simulator for the study of CO_(2)-EOR.Cases are thoroughly investigated with various injection rates and BHP limitations.Simulation results show that BHP has a minimal impact on oil production,whereas increased injection rates significantly enhance cumulative oil production(COP)by 33.39%and extend reservoir life from 20 to 37 years.Total oil production increased to 33150.7 MSTB,accompanied by reduced water production and maintained reservoir pressure.These findings align with previous research,underscoring the importance of optimized CO_(2) injection strategies for maximizing oil recovery and reservoir performance.展开更多
The use of ethanol is a promising method to reduce the emissions of diesel engines.The present study has been based on the installation of a gasoline electronic injection system in a single-cylinder diesel engine to c...The use of ethanol is a promising method to reduce the emissions of diesel engines.The present study has been based on the installation of a gasoline electronic injection system in a single-cylinder diesel engine to control the amount of ethanol entering the cylinder during the compression(while diesel has been injected into the cylinder by the original pump injection system).The injection time has been controlled by crank angle signal collected by an AVL angle indicator.In the tests ethanol and diesel each accounted for half of the fuel volume,and the total heat energy supply of the fuel was equivalent to that of the diesel under the operating conditions of the original engine.A three-dimensional combustion model of the diesel engine has been implemented by using the CFD software FIRE.Simulations have been carried out assuming uniform and non-uniform injections rate for the different holes and the different results have been compared.According to these results,a non-uniform injection rate can produce early ignition and cause an increase in the maximum in-cylinder pressure and the maximum average incylinder temperature.Moreover,in such conditions NO emissions are larger while soot emission is slightly lower.展开更多
Developing low-permeability Coalbed Methane(CBM)reservoirs can significantly benefit from a comprehensive understanding of hydraulic fracture nucleation and propagation mechanisms,particularly in anthracite CBM reserv...Developing low-permeability Coalbed Methane(CBM)reservoirs can significantly benefit from a comprehensive understanding of hydraulic fracture nucleation and propagation mechanisms,particularly in anthracite CBM reservoirs.This study employs true-triaxial hydraulic fracturing experiments to investigate these mechanisms,with variables including injection flow rate,horizontal stress difference(σH-σh),and bedding orientation.Additionally,we conduct corresponding numerical cases to validate the experimental conclusions.The research also considers re-fracturing instances.For the first time,we utilize a combination of Kaiser tests and the stress transfer function in ANSYS Workbench finite element analysis to accurately restore the confining pressure of the coal sample.The findings suggest that a high initial injection flow rate during hydraulic fracturing can promote fluid leakage and aid in maintaining substantial fracture pressure.Enhanced fracturing efficiency can be achieved through higher injection rates,and it can ensure optimal fracturing efficiency,minimizing roof and floor fracturing in coal reservoirs to prevent fracturing fluid leakage.The presence of a high horizontal stress difference facilitates hydraulic fracture propagation along the direction of the maximum horizontal compressive stress,requiring a greater hydraulic pressure to produce more fracture systems in coal reservoirs.Additionally,a minor deviation in the wellbore injection direction from the bedding orientation assists in creating a complex hydraulic fractured network,although this also requires higher hydraulic pressure to initiate new fractures.In the case of multiple hydraulic fracturing,the second initiation pressure tends to be significantly higher than the first,indicating that a sequential increase in hydraulic pressure aids the formation of additional fractures.Moreover,a simplified numerical simulation has been conducted to corroborate the experimental findings.These insights are crucial in optimizing hydraulic fracturing processes to enhance the permeability of anthracite CBM reservoirs.展开更多
Hall plot analysis,as a widespread injection evaluation method,however,often fails to achieve the desired result because of the inconspicuous change of the curve shape.Based on the cumulative injection volume,injectio...Hall plot analysis,as a widespread injection evaluation method,however,often fails to achieve the desired result because of the inconspicuous change of the curve shape.Based on the cumulative injection volume,injection rate,and the injection pressure,this paper establishes a new method using the ratio of the pressure to the injection rate（RPI） and the rate of change of the RPI to evaluate the injection efficiency of chemical flooding.The relationship between the RPI and the apparent resistance factor（apparent residual resistance factor） is obtained,similarly to the relationship between the rate of change of the RPI and the resistance factor.In order to estimate a thief zone in a reservoir,the influence of chemical crossflow on the rate of change of the RPI is analyzed.The new method has been applied successfully in the western part of the Gudong 7th reservoir.Compared with the Hall plot analysis,it is more accurate in real-time injection data interpretation and crossflow estimation.Specially,the rate of change of the RPI could be particularly suitably applied for new wells or converted wells lacking early water flooding history.展开更多
Steam assisted gravity drainage （SAGD） technology has been industrialized popularization and application in our country, according to the characteristics of Xing group I SAGD experimental zone in liaohe oilfield, SA...Steam assisted gravity drainage （SAGD） technology has been industrialized popularization and application in our country, according to the characteristics of Xing group I SAGD experimental zone in liaohe oilfield, SAGD production stage injection-production parameters such as the operating pressure, Sub - Cool control, steam injection rate, steam dryness, production factor are studied and selected.展开更多
In order to improve the effect of water control and oil stabilization during high water cut period, a mathematical model of five point method well group was established with the high water cut well group of an Oilfiel...In order to improve the effect of water control and oil stabilization during high water cut period, a mathematical model of five point method well group was established with the high water cut well group of an Oilfield as the target area, the variation law of water cut and recovery factor of different injection parameters was analyzed, and the optimization research of injection parameters of polymer enhanced foam flooding was carried out. The results show that the higher the injection rate, the lower the water content curve, and the higher the oil recovery rate. As the foam defoamed when encountering oil, when the injection time was earlier than 80% of water cut, the later the injection time was, the better the oil displacement effect would be. When the injection time was later than 80% of water cut, the later the injection time was, the worse the oil displacement effect would be. The larger the injection volume, the lower the water content curve and the higher the recovery rate. After the injection volume exceeded 0.2 PV, the amplitude of changes in water content and recovery rate slowed down. The optimal injection parameters of profile control agent for high water content well group in Oilfield A were: injection rate of 15 m<sup>3</sup>/d, injection timing of 80% water content, and injection volume of 0.2 PV.展开更多
The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the t...The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the total geological reserves of the oilfield.Therefore,they have considerable potential for future oil production.The current layered injection technologies fail to achieve effective control over the low single-layer injection rates since they can only produce low throttle differential pressure under low injection rates(5-20 m^(3)/d).In this study,a symmetrically-structured double-offset-hole injection allocator and a novel throttling component were developed.Their spatial layout was constructed and mechanical parameters were optimized using finite element analysis,which allows for expanding the flow rate range at low injection rates.According to experimental results,the throttle differential pressure increased from 0.2 MPa to 0.8 MPa at an injection rate of 5 m^(3)/d,and the range of the single-layer flow rates expanded from 20-70 m^(3)/d to 5-70 m3/d.The field test results show that the effective production of oil layers with medium and low permeability was achieved and that the ratio of producing oil layer thickness to the total reservoir thickness increased by 9.7%on average.Therefore,this study provides valuable technical support for the effective chemical-flooding-based development of Class-Ⅲ oil reservoirs.展开更多
São Paulo State has witnessed CO_(2)storage-based investigations considering the availability of suitable geologic structures and proximity to primary CO_(2)source sinks related to bioenergy and carbon capture an...São Paulo State has witnessed CO_(2)storage-based investigations considering the availability of suitable geologic structures and proximity to primary CO_(2)source sinks related to bioenergy and carbon capture and storage(BECCS)activities.The current study presents the hydrocarbon viability evaluations and CO_(2)storage prospects,focusing on the sandstone units of the Rio Bonito Formation.The objective is to apply petrophysical evaluations with geochemical inputs in predicting future hydrocarbon(gas)production to boost CO_(2)storage within the study location.The study used data from eleven wells with associated wireline logs(gamma ray,resistivity,density,neutron,and sonic)to predict potential hydrocarbon accumulation and fluid mobility in the investigated area.Rock samples(shale and carbonate)obtained from depths>200 m within the study location have shown bitumen presence.Organic geochemistry data of the Rio Bonito Formation shale beds suggest they are potential hydrocarbon source rocks and could have contributed to the gas accumulations within the sandstone units.Some drilled well data,e.g.,CB-1-SP and TI-1-SP,show hydrocarbon(gas)presence based on the typical resistivity and the combined neutron-density responses at depths up to 3400 m,indicating the possibility of other hydrocarbon members apart from the heavy oil(bitumen)observed from the near-surface rocks samples.From the three-dimensional(3-D)model,the free fluid indicator(FFI)is more significant towards the southwest and southeast of the area with deeper depths of occurrence,indicating portions with reasonable hydrocarbon recovery rates and good prospects for CO_(2)injection,circulation and permanent storage.However,future studies based on contemporary datasets are required to establish the hydrocarbon viability further,foster gas production events,and enhance CO_(2)storage possibilities within the region.展开更多
Fluid injection in fractured rocks presents significant challenges requiring the integration of various elements to account for reservoir property heterogeneities.To understand magnitude of potential seismic risks res...Fluid injection in fractured rocks presents significant challenges requiring the integration of various elements to account for reservoir property heterogeneities.To understand magnitude of potential seismic risks resulting from CO_(2) injection in naturally fractured sand reservoirs in the study location,we devised a simulation model which utilizes a coupled thermo-hydro-mechanical(THM)approach,encompassing different injection scenarios and reservoir injection systems.The model effectively cap-tures the complex interplay between geological features and fault failure processes.Furthermore,we examined the mechanical response of the caprock under constant injection rates by analyzing the evolution of shear stress and its impact on permeability enhancement.Our findings reveal that the pressurization effect of fluid and stress alterations trigger significant fault rupture,leading to seismic events of varying magnitudes.The extent of seismic activity hinges on the reservoir's initial state,the properties of the overlying caprock,and the injected volume.Moreover,we discovered that deformations within the caprock layer are most pronounced near fault zones,gradually diminishing with distance from these zones.Notably,the degree of permeability modification in the caprock is linked to the magnitude of shear stress.Additionally,our research corroborated that higher injection rates markedly accelerate fault slip,albeit with minimal impact on the extent of permeability enhancement.However,we noted a non-linear relationship between seismic activity and fluid injection rates,suggesting that the magnitude of seismic consequences is contingent upon the temporal analysis of various parameters.These significant findings offer valuable insights into understanding the intricate processes associated with subsurface injection,which often manifest in phenomena such as fault ruptures and induced seismicity.展开更多
Enzyme-induced carbonate precipitation(EICP)is an environment-friendly method for improving soil mechanical properties.The extraction and application of plant crude urease reduces the treatment cost.However,in terms o...Enzyme-induced carbonate precipitation(EICP)is an environment-friendly method for improving soil mechanical properties.The extraction and application of plant crude urease reduces the treatment cost.However,in terms of the efficiency of calcium carbonate production and cementation,crude urease is considered inferior to pure urease or urease bacteria.In this paper,urease extracted from soybean was used to explore the effects of urease activity,treatment method,number of treatments(NTs),injection rate,and curing time on the unconfined compressive strength and calcium carbonate distribution characteristics of EICP-treated sand.The results showed that,compared with the pre-mixing method and the two-phase method,the one-phase method produced higher strength and a more uniform distribution of calcium carbonate.The cementation efficiency decreased with the increase of urease activity.The high-rate injection can improve the treatment effect of high-activity urease.Under the same cementation level,high strength and calcium carbonate cementation efficiency can be achieved by one-phase-low-activity EICP treatment.Data Availability Statement:All data,models,and code generated or used during the study appear in the submitted article.展开更多
Injector configuration and spray characteristics are important parameters that define diesel combustion and emissions performance. One of the critical spray inputs is the Rate-of-Injection (ROI) profile. The ROI profi...Injector configuration and spray characteristics are important parameters that define diesel combustion and emissions performance. One of the critical spray inputs is the Rate-of-Injection (ROI) profile. The ROI profile depends on the spray’s operating conditions, including nozzle geometry (e.g., nozzle diameter), injection pressure, and injection duration. Besides, the internal nozzle flow phenomenon and external ambient conditions can further impact fuel introduction characteristics. This study measured the ROI profile of a heavy-duty (multi-hole) diesel injector using the Bosch tube technique. Injection pressure and injection duration were varied from 600 to 2600 bar and 0.5–3.0 ms, respectively. After post-processing, measurement data were then used to train numerical models, including a developed machine learning (ML) model that can create very similar ROI profiles with experimental data. Next, a Computational Fluid Dynamics (CFD) simulation used the ROI profile generated by ML model. For comparison, there are other simplified ROI profiles used in similar CFD simulation configuration. Results showed that the any difference in ROI profiles could affect the combustion and emissions significantly. This further emphasizes the need to provide high-fidelity spray input in terms of ROI profile for CFD simulation. The current ML model can deliver a realistic ROI profile for any given rail pressure and injection duration.展开更多
This paper presents a new method of injection-production allocation estimation for water-flooding mature oilfields.The suggested approach is based on logistic growth rate functions and several type-curve matching meth...This paper presents a new method of injection-production allocation estimation for water-flooding mature oilfields.The suggested approach is based on logistic growth rate functions and several type-curve matching methods.Using the relationship between these equations,oil production and water injection rate as well as injection-production ratio can be easily forecasted.The calculation procedure developed and outlined in this paper requires very few production data and is easily implemented.Furthermore,an oilfield case has been analyzed.The synthetic and field cases validate the calculation procedure,so it can be accurately used in forecasting production data,and it is important to optimize the whole injection-production system.展开更多
Water flooding type-curves,recently receiving increasing attentions,play an essential role in evaluation of OOIP and prediction of future production.The study proposed a method modified form Weibull model and water fl...Water flooding type-curves,recently receiving increasing attentions,play an essential role in evaluation of OOIP and prediction of future production.The study proposed a method modified form Weibull model and water flooding type-curves to analyze the reservoir production performance,including predication of oil production and water injection rates.The results indicate that the method can estimate and provide solutions for oil production,water injection rate and injection-production ratio with a well accuracy.A case study is conducted to demonstrate the applicability and accuracy of model by field data.The matching results illustrate a good accordance between calculated values and field data.展开更多
This study uses computational fluid dynamics to survey the gas‒liquid flow hydrodynamics of a self-priming venturi scrubber with and without ring baffles.Based on the simulation results,we explore how the structure an...This study uses computational fluid dynamics to survey the gas‒liquid flow hydrodynamics of a self-priming venturi scrubber with and without ring baffles.Based on the simulation results,we explore how the structure and configuration parameters such as baffle height,opening-area ratio,and baffle thickness affect the injection flow rate and the homogeneity of the gas‒liquid mixture.In addition,we report the best structure and configuration parameters for the ring baffle.The best position for the ring baffle is at nearly 7/16 of the length of the diffuser above the throat.Having the baffle too near the throat causes large pressure loss,decreasing the injection flow rate.The decrease in opening-area ratio leads to a lower injection flow rate and a more homogeneous gas‒liquid mixture.The optimal value depends on the requirement of the injection flow rate.For the baffle thickness,5 mm is recommended;an overly thick baffle decreases the homogeneity of the gas‒liquid mixture near the throat.All structure parameters and configuration parameters must satisfy the requirement imposed by the injection flow rate and scrubbing efficiency.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB2390300)the National Natural Science Foundation of China(Grant No.42172292)Yinlin Ji is grateful for the support by the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(Contract No.VH-NG-1516).
文摘This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.
基金supported by the National Natural Science Foundation of China(Grant.Nos.52364004,52464005)the Youth Talent Growth Project of Guizhou Provincial Department of Education(Grant No.QianJiaoJi[2024]18).
文摘Injection rate is crucial for determining the hydraulic fracturing effectiveness;however,the effects of the injection rate on the pore and fracture structure(PFS)and fluid infiltration during injection pressurization have rarely been explored.In this study,the cylindrical sandstone samples were hydraulically fractured at various injection rates on a self-developed integrated nuclear magnetic resonance(NMR)and hydraulic fracturing experimental system.The results show that low injection rates predominantly resulted in macropore-scale damage by creating intergranular cracks,whereas high injection rates facilitated micropore-scale damage,probably owing to the adsorption swelling effect of clay minerals within pores.Additionally,the water contents of the samples with low injection rates exhibited a continuous increase,whereas those of the samples with high injection rates initially increased and subsequently stabilized.Magnetic resonance imaging(MRI)indicated that fluid infiltration during the fracturing process exhibited high anisotropy owing to the inherent heterogeneous PFS distributions around the wellbore.Moreover,a primary fluid infiltration path exists that aligns with the initiation direction of the hydraulic fractures.However,the fluid infiltration damage distance along the hydraulic fracture direction decreased with increasing injection rate,whereas the fluid infiltration damage distance perpendicular to the hydraulic fracture direction was approximately equal to the characteristic length,regardless of the injection rate.Finally,we recommend using the pore damage during fluid pressurization as the basis for selecting the proppant size and employing a primary fluid infiltration path to predict hydraulic fracture initiation.These findings provide valuable insights into the design of hydraulic fracturing in tight gas reservoirs.
基金the Beijing Natural Science Foundation(No.8232044)the Science Foundation of China University of Petroleum,Beijing(No.2462023BJRC030).
文摘The long-term stability of CO_(2) storage represents a pivotal challenge in geological CO_(2) storage(CGS),particularly within deep saline aquifers characterized by complex fault-block systems.While the injection sites and rate under different fault structures will directly affect the CO_(2) storage effect and the risk of leakage.This study investigates the Gaoyou Sag in the Subei Basin,a representative fault-block reservoir,through an integrated numerical-experimental approach.A three-dimensional simulation model incorporating multiphase flow dynamics was developed to characterize subsurface CO_(2) transport and dissolution processes.A novel fault seal capacity evaluation framework was proposed,integrating three critical geological indices(fault throw/reservoir thickness/caprock thicknesses)with the coupling of formation physical properties,temperature,and pressure for the rational selection of injection sites and rates.The results show that Optimal storage performance is observed when the fault throw is lower than the reservoir and caprock thicknesses.Furthermore,higher temperature and pressure promote the dissolution and diffusion of CO_(2),while compared to the structural form of faults,the physical properties of faults have a more significant effect on CO_(2) leakage.The larger reservoir space and the presence of an interlayer reduce the risk of CO_(2) leakage,and augmenting storage potential.Decreasing the injection rate increases the proportion of dissolved CO_(2),thereby enhancing the safety of CO_(2) storage.
基金supported by the National Key R&D Program of China (No. 2018YFC0807805)the National Natural Science Foundation of China (No. 52074049)。
文摘Resistivity will have different response characteristics to the hydraulic fracture propagation process. In this work, a resistivity testing system for hydraulic fracturing specimens was established. Resistivity and acoustic emission(AE) information were jointly analysed to determine the dynamic response characteristics of resistivity during hydraulic fracture propagation. The results show that the water and fracture exert a competitive influence on the connection structure of the circuit, and there are two significant peak resistivity points in the curve, presenting a double peak therein. The peak resistivity data of the specimen with a larger fracture area are much different from the initial value. With the increase of the rate of injection, the range of variation of the highest value that can be reached with the specimen resistivity decreases. High resistivity rates or high resistivity fluctuations exhibit rapid a release of fracture energy. The fracture failure mode dominated by shear fractures makes the formation produce a “series+parallel” electrical connection structure;a calculation model of formation resistivity based on shear and tensile failure was proposed to characterize the proportion of different types of hydraulic fractures and elucidate the control effect of matrix resistivity on the electrical performance of the overall circuit structure.
基金Supported by National Natural Science Foundation of China under Grant No.21301079
文摘This paper investigates the effect of both unequal injection rates and different hopping rates on two-lane asymmetric simple exclusion processes(ASEPs) with asymmetric coupling. When the hopping rates of both lanes are different, the system includes six steady phases, however, when the hopping rates of both lanes are same, the seventh phase(MC, MC) will exist in the system. Interestingly, with different hopping rates of both lanes, the densities of the system cannot be influenced by the non-zero vertical transition rate. Our theoretical arguments are in well agreement with extensively performed Monte Carlo simulations.
基金National Science and Technology Major Special Project,2016ZX05044CBM Development Technology and Pilot Test in East Yunnan and Western Guizhou.
文摘Detailed information is provided for the design and construction of nitrogen drilling in a coal seam.Two prototype wells are considered.The Guo model is used to calculate the required minimum gas injection rate,while the Finnie,Sommerfeld,and Tulsa models are exploited to estimate the ensuing erosion occurring in pipe strings.The calculated minimum gas injection rates are 67.4 m^(3)/min(with water)and 49.4 m^(3)/min(without water),and the actual field of use is 90–120 m^(3)/min.The difference between the calculated injection pressure and the field value is 6.5%–15.2%(formation with water)and 0.65%–7.32%(formation without water).The results show that the Guo model can more precisely represent the situation of the no water formation in the nitrogen drilling of a coal seam.The Finnie,Sommerfeld,and Tulsa models have different sensitivities to cutting densities,particle size,impact velocity and angle,and pipe string hardness.
文摘The goal of net-zero carbon emissions has led to widespread interest in lowering carbon dioxide(CO_(2))emissions.At the same time,the oil and gas industry seeks to enhance oil recovery(EOR)techniques to meet growing demand.CO_(2) flooding,a key EOR method,offers a dual benefit:reducing CO_(2) emissions and enhancing oil recovery.This study investigates the impact of injection rate and bottom hole pressure(BHP)on CO_(2) injection performance using the Nexus reservoir simulator,a novel application in CO_(2)-EOR research.To the best of the author's knowledge,there is no previous research published in which the researchers used the Nexus reservoir simulator for the study of CO_(2)-EOR.Cases are thoroughly investigated with various injection rates and BHP limitations.Simulation results show that BHP has a minimal impact on oil production,whereas increased injection rates significantly enhance cumulative oil production(COP)by 33.39%and extend reservoir life from 20 to 37 years.Total oil production increased to 33150.7 MSTB,accompanied by reduced water production and maintained reservoir pressure.These findings align with previous research,underscoring the importance of optimized CO_(2) injection strategies for maximizing oil recovery and reservoir performance.
基金the National Natural Science Foundation of China(Nos.51476072 and 51366002)the Science and Technology Foundation of Guizhou Province(No.[2018]1006)+1 种基金Supporting Program for Top Scientific and Technological Talents in Universities of Guizhou Province(No.[2018]062)High-level Talent Research Funding Project of Guizhou Institute of Technology and Key Construction Projects of the First Class University(Phase I)of Guizhou Province in 2017-the First Class Course(Nos.2017158418 and 2017158435).
文摘The use of ethanol is a promising method to reduce the emissions of diesel engines.The present study has been based on the installation of a gasoline electronic injection system in a single-cylinder diesel engine to control the amount of ethanol entering the cylinder during the compression(while diesel has been injected into the cylinder by the original pump injection system).The injection time has been controlled by crank angle signal collected by an AVL angle indicator.In the tests ethanol and diesel each accounted for half of the fuel volume,and the total heat energy supply of the fuel was equivalent to that of the diesel under the operating conditions of the original engine.A three-dimensional combustion model of the diesel engine has been implemented by using the CFD software FIRE.Simulations have been carried out assuming uniform and non-uniform injections rate for the different holes and the different results have been compared.According to these results,a non-uniform injection rate can produce early ignition and cause an increase in the maximum in-cylinder pressure and the maximum average incylinder temperature.Moreover,in such conditions NO emissions are larger while soot emission is slightly lower.
基金funded by the National Natural Science Foundation of China(No.42202155)China Postdoctoral Science Foundation(No.2021MD703807)+7 种基金Heilongjiang Provincial Postdoctoral Science Foundation(No.LBH-Z20121)financial support from the China Scholarship Council(No.202008230018)the Research Fund Program of Hubei Key Laboratory of Resources and Eco-Environment Geology(No.HBREGKFJJ-202309)funding by the DGICYT Spanish Project(grant no.PID2020-118999GB-I00)funded by the MCIN/AEI/10.13039/501100011033funding by the Ramón y Cajal fellowship(grant no.RyC-2018-026335-I)funded by the MCIN/AEI/10.13039/50110001103the European Social Fund-Investing in Your Future.
文摘Developing low-permeability Coalbed Methane(CBM)reservoirs can significantly benefit from a comprehensive understanding of hydraulic fracture nucleation and propagation mechanisms,particularly in anthracite CBM reservoirs.This study employs true-triaxial hydraulic fracturing experiments to investigate these mechanisms,with variables including injection flow rate,horizontal stress difference(σH-σh),and bedding orientation.Additionally,we conduct corresponding numerical cases to validate the experimental conclusions.The research also considers re-fracturing instances.For the first time,we utilize a combination of Kaiser tests and the stress transfer function in ANSYS Workbench finite element analysis to accurately restore the confining pressure of the coal sample.The findings suggest that a high initial injection flow rate during hydraulic fracturing can promote fluid leakage and aid in maintaining substantial fracture pressure.Enhanced fracturing efficiency can be achieved through higher injection rates,and it can ensure optimal fracturing efficiency,minimizing roof and floor fracturing in coal reservoirs to prevent fracturing fluid leakage.The presence of a high horizontal stress difference facilitates hydraulic fracture propagation along the direction of the maximum horizontal compressive stress,requiring a greater hydraulic pressure to produce more fracture systems in coal reservoirs.Additionally,a minor deviation in the wellbore injection direction from the bedding orientation assists in creating a complex hydraulic fractured network,although this also requires higher hydraulic pressure to initiate new fractures.In the case of multiple hydraulic fracturing,the second initiation pressure tends to be significantly higher than the first,indicating that a sequential increase in hydraulic pressure aids the formation of additional fractures.Moreover,a simplified numerical simulation has been conducted to corroborate the experimental findings.These insights are crucial in optimizing hydraulic fracturing processes to enhance the permeability of anthracite CBM reservoirs.
基金the financial support from the National Natural Science Foundation of China (Grant No. 51574269)the Important National Science and Technology Specific Projects of China (Grant No. 2016ZX05011-003)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. 15CX08004A, 13CX05007A)the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT1294)
文摘Hall plot analysis,as a widespread injection evaluation method,however,often fails to achieve the desired result because of the inconspicuous change of the curve shape.Based on the cumulative injection volume,injection rate,and the injection pressure,this paper establishes a new method using the ratio of the pressure to the injection rate（RPI） and the rate of change of the RPI to evaluate the injection efficiency of chemical flooding.The relationship between the RPI and the apparent resistance factor（apparent residual resistance factor） is obtained,similarly to the relationship between the rate of change of the RPI and the resistance factor.In order to estimate a thief zone in a reservoir,the influence of chemical crossflow on the rate of change of the RPI is analyzed.The new method has been applied successfully in the western part of the Gudong 7th reservoir.Compared with the Hall plot analysis,it is more accurate in real-time injection data interpretation and crossflow estimation.Specially,the rate of change of the RPI could be particularly suitably applied for new wells or converted wells lacking early water flooding history.
文摘Steam assisted gravity drainage （SAGD） technology has been industrialized popularization and application in our country, according to the characteristics of Xing group I SAGD experimental zone in liaohe oilfield, SAGD production stage injection-production parameters such as the operating pressure, Sub - Cool control, steam injection rate, steam dryness, production factor are studied and selected.
文摘In order to improve the effect of water control and oil stabilization during high water cut period, a mathematical model of five point method well group was established with the high water cut well group of an Oilfield as the target area, the variation law of water cut and recovery factor of different injection parameters was analyzed, and the optimization research of injection parameters of polymer enhanced foam flooding was carried out. The results show that the higher the injection rate, the lower the water content curve, and the higher the oil recovery rate. As the foam defoamed when encountering oil, when the injection time was earlier than 80% of water cut, the later the injection time was, the better the oil displacement effect would be. When the injection time was later than 80% of water cut, the later the injection time was, the worse the oil displacement effect would be. The larger the injection volume, the lower the water content curve and the higher the recovery rate. After the injection volume exceeded 0.2 PV, the amplitude of changes in water content and recovery rate slowed down. The optimal injection parameters of profile control agent for high water content well group in Oilfield A were: injection rate of 15 m<sup>3</sup>/d, injection timing of 80% water content, and injection volume of 0.2 PV.
基金sponsored by the key consulting project of the Chinese Academy of Engineering entitled Research on the Sustainable Development Strategy of China's High Water-cut Old Oilfields(No.2019-XZ-15)the National major project entitled Large Oil and Gas Field and Coalbed Methane Development(No.:2016ZX05010006).
文摘The Class-Ⅲ oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes,an oil recovery of 39%,with remaining reserves accounting for more than 45%of the total geological reserves of the oilfield.Therefore,they have considerable potential for future oil production.The current layered injection technologies fail to achieve effective control over the low single-layer injection rates since they can only produce low throttle differential pressure under low injection rates(5-20 m^(3)/d).In this study,a symmetrically-structured double-offset-hole injection allocator and a novel throttling component were developed.Their spatial layout was constructed and mechanical parameters were optimized using finite element analysis,which allows for expanding the flow rate range at low injection rates.According to experimental results,the throttle differential pressure increased from 0.2 MPa to 0.8 MPa at an injection rate of 5 m^(3)/d,and the range of the single-layer flow rates expanded from 20-70 m^(3)/d to 5-70 m3/d.The field test results show that the effective production of oil layers with medium and low permeability was achieved and that the ratio of producing oil layer thickness to the total reservoir thickness increased by 9.7%on average.Therefore,this study provides valuable technical support for the effective chemical-flooding-based development of Class-Ⅲ oil reservoirs.
基金sponsored by Fundação de Amparoa Pesquisa do Estado de São Paulo(FAPESP)(2014/50279-4,2020/15230-5,2021/06158-1)Shell Brasil.
文摘São Paulo State has witnessed CO_(2)storage-based investigations considering the availability of suitable geologic structures and proximity to primary CO_(2)source sinks related to bioenergy and carbon capture and storage(BECCS)activities.The current study presents the hydrocarbon viability evaluations and CO_(2)storage prospects,focusing on the sandstone units of the Rio Bonito Formation.The objective is to apply petrophysical evaluations with geochemical inputs in predicting future hydrocarbon(gas)production to boost CO_(2)storage within the study location.The study used data from eleven wells with associated wireline logs(gamma ray,resistivity,density,neutron,and sonic)to predict potential hydrocarbon accumulation and fluid mobility in the investigated area.Rock samples(shale and carbonate)obtained from depths>200 m within the study location have shown bitumen presence.Organic geochemistry data of the Rio Bonito Formation shale beds suggest they are potential hydrocarbon source rocks and could have contributed to the gas accumulations within the sandstone units.Some drilled well data,e.g.,CB-1-SP and TI-1-SP,show hydrocarbon(gas)presence based on the typical resistivity and the combined neutron-density responses at depths up to 3400 m,indicating the possibility of other hydrocarbon members apart from the heavy oil(bitumen)observed from the near-surface rocks samples.From the three-dimensional(3-D)model,the free fluid indicator(FFI)is more significant towards the southwest and southeast of the area with deeper depths of occurrence,indicating portions with reasonable hydrocarbon recovery rates and good prospects for CO_(2)injection,circulation and permanent storage.However,future studies based on contemporary datasets are required to establish the hydrocarbon viability further,foster gas production events,and enhance CO_(2)storage possibilities within the region.
文摘Fluid injection in fractured rocks presents significant challenges requiring the integration of various elements to account for reservoir property heterogeneities.To understand magnitude of potential seismic risks resulting from CO_(2) injection in naturally fractured sand reservoirs in the study location,we devised a simulation model which utilizes a coupled thermo-hydro-mechanical(THM)approach,encompassing different injection scenarios and reservoir injection systems.The model effectively cap-tures the complex interplay between geological features and fault failure processes.Furthermore,we examined the mechanical response of the caprock under constant injection rates by analyzing the evolution of shear stress and its impact on permeability enhancement.Our findings reveal that the pressurization effect of fluid and stress alterations trigger significant fault rupture,leading to seismic events of varying magnitudes.The extent of seismic activity hinges on the reservoir's initial state,the properties of the overlying caprock,and the injected volume.Moreover,we discovered that deformations within the caprock layer are most pronounced near fault zones,gradually diminishing with distance from these zones.Notably,the degree of permeability modification in the caprock is linked to the magnitude of shear stress.Additionally,our research corroborated that higher injection rates markedly accelerate fault slip,albeit with minimal impact on the extent of permeability enhancement.However,we noted a non-linear relationship between seismic activity and fluid injection rates,suggesting that the magnitude of seismic consequences is contingent upon the temporal analysis of various parameters.These significant findings offer valuable insights into understanding the intricate processes associated with subsurface injection,which often manifest in phenomena such as fault ruptures and induced seismicity.
基金supported by National Natural Science Foundation of China,China(Grant No.42177454)the Training Plan of Young Scholar in Colleges and Universities of Henan Province,China(Grant No.2019GGJS041)Postgraduate Education Reform and Quality Improvement Project of Henan Province,China(Grant No.YJS2021JD13).
文摘Enzyme-induced carbonate precipitation(EICP)is an environment-friendly method for improving soil mechanical properties.The extraction and application of plant crude urease reduces the treatment cost.However,in terms of the efficiency of calcium carbonate production and cementation,crude urease is considered inferior to pure urease or urease bacteria.In this paper,urease extracted from soybean was used to explore the effects of urease activity,treatment method,number of treatments(NTs),injection rate,and curing time on the unconfined compressive strength and calcium carbonate distribution characteristics of EICP-treated sand.The results showed that,compared with the pre-mixing method and the two-phase method,the one-phase method produced higher strength and a more uniform distribution of calcium carbonate.The cementation efficiency decreased with the increase of urease activity.The high-rate injection can improve the treatment effect of high-activity urease.Under the same cementation level,high strength and calcium carbonate cementation efficiency can be achieved by one-phase-low-activity EICP treatment.Data Availability Statement:All data,models,and code generated or used during the study appear in the submitted article.
文摘Injector configuration and spray characteristics are important parameters that define diesel combustion and emissions performance. One of the critical spray inputs is the Rate-of-Injection (ROI) profile. The ROI profile depends on the spray’s operating conditions, including nozzle geometry (e.g., nozzle diameter), injection pressure, and injection duration. Besides, the internal nozzle flow phenomenon and external ambient conditions can further impact fuel introduction characteristics. This study measured the ROI profile of a heavy-duty (multi-hole) diesel injector using the Bosch tube technique. Injection pressure and injection duration were varied from 600 to 2600 bar and 0.5–3.0 ms, respectively. After post-processing, measurement data were then used to train numerical models, including a developed machine learning (ML) model that can create very similar ROI profiles with experimental data. Next, a Computational Fluid Dynamics (CFD) simulation used the ROI profile generated by ML model. For comparison, there are other simplified ROI profiles used in similar CFD simulation configuration. Results showed that the any difference in ROI profiles could affect the combustion and emissions significantly. This further emphasizes the need to provide high-fidelity spray input in terms of ROI profile for CFD simulation. The current ML model can deliver a realistic ROI profile for any given rail pressure and injection duration.
文摘This paper presents a new method of injection-production allocation estimation for water-flooding mature oilfields.The suggested approach is based on logistic growth rate functions and several type-curve matching methods.Using the relationship between these equations,oil production and water injection rate as well as injection-production ratio can be easily forecasted.The calculation procedure developed and outlined in this paper requires very few production data and is easily implemented.Furthermore,an oilfield case has been analyzed.The synthetic and field cases validate the calculation procedure,so it can be accurately used in forecasting production data,and it is important to optimize the whole injection-production system.
基金This research is supported by The National Natural Science Fund(No.51574199),administered by the National Natural Science Foundation of China.
文摘Water flooding type-curves,recently receiving increasing attentions,play an essential role in evaluation of OOIP and prediction of future production.The study proposed a method modified form Weibull model and water flooding type-curves to analyze the reservoir production performance,including predication of oil production and water injection rates.The results indicate that the method can estimate and provide solutions for oil production,water injection rate and injection-production ratio with a well accuracy.A case study is conducted to demonstrate the applicability and accuracy of model by field data.The matching results illustrate a good accordance between calculated values and field data.
文摘This study uses computational fluid dynamics to survey the gas‒liquid flow hydrodynamics of a self-priming venturi scrubber with and without ring baffles.Based on the simulation results,we explore how the structure and configuration parameters such as baffle height,opening-area ratio,and baffle thickness affect the injection flow rate and the homogeneity of the gas‒liquid mixture.In addition,we report the best structure and configuration parameters for the ring baffle.The best position for the ring baffle is at nearly 7/16 of the length of the diffuser above the throat.Having the baffle too near the throat causes large pressure loss,decreasing the injection flow rate.The decrease in opening-area ratio leads to a lower injection flow rate and a more homogeneous gas‒liquid mixture.The optimal value depends on the requirement of the injection flow rate.For the baffle thickness,5 mm is recommended;an overly thick baffle decreases the homogeneity of the gas‒liquid mixture near the throat.All structure parameters and configuration parameters must satisfy the requirement imposed by the injection flow rate and scrubbing efficiency.
