Carbonate reservoirs worldwide are complex in structure,diverse in form,and highly heterogeneous.Based on these characteristics,the reservoir stimulation technologies and fluid flow characteristics of carbonate reserv...Carbonate reservoirs worldwide are complex in structure,diverse in form,and highly heterogeneous.Based on these characteristics,the reservoir stimulation technologies and fluid flow characteristics of carbonate reservoirs are briefly described in this study.The development methods and EOR technologies of carbonate reservoirs are systematically summarized,the relevant mechanisms are analyzed,and the application status of oil fields is catalogued.The challenges in the development of carbonate reservoirs are discussed,and future research directions are explored.In the current development processes of carbonate reservoirs,water flooding and gas flooding remain the primary means but are often prone to channeling problems.Chemical flooding is an effective method of tertiary oil recovery,but the harsh formation conditions require high-performance chemical agents.The application of emerging technologies can enhance the oil recovery efficiency and environmental friendliness to a certain extent,which is welcome in hard-to-recover areas such as heavy oil reservoirs,but the economic cost is often high.In future research on EOR technologies,flow field control and flow channel plugging will be the potential directions of traditional development methods,and the application of nanoparticles will revolutionize the chemical EOR methods.On the basis of diversified reservoir stimulation,combined with a variety of modern data processing schemes,multichannel EOR technologies are being developed to realize the systematic,intelligent,and cost-effective development of carbonate reservoirs.展开更多
For improving the hole-enlarging capability,roundness and rock-breaking efficiency of the nozzle in radial jet drilling,a new structure of self-rotating nozzle was put forward.The flow structure and rock-breaking feat...For improving the hole-enlarging capability,roundness and rock-breaking efficiency of the nozzle in radial jet drilling,a new structure of self-rotating nozzle was put forward.The flow structure and rock-breaking features of the self-rotating nozzle were investigated with sliding mesh model and labortary tests and also compared with the straight and the swirling integrated nozzle and multi-orifice nozzle which have been applied in radial jet drilling.The results show that the self-rotating jet is energy concentrated,has longer effective distance,better hole-enlarging capability and roundness and impacts larger circular area at the bottom of the drilling hole,compared with the other two nozzles.Forward jet flow generated from the nozzle is peak shaped,and the jet velocity attenuates slowly at the outer edge.Due to periodic rotary percussion,the pressure fluctuates periodically on rock surface,improving shear and tensile failures on the rock matrix and thereby enhancing rock-breaking efficiency.The numerical simulation results of the flow structure of the nozzle are consistent with the experiments.This study provides an innovative approach for radial jet drilling technology in the petroleum industry.展开更多
The ultra-low permeability reservoir is regarded as an important energy source for oil and gas resource development and is attracting more and more attention.In this work,the active silica nanofuids were prepared by m...The ultra-low permeability reservoir is regarded as an important energy source for oil and gas resource development and is attracting more and more attention.In this work,the active silica nanofuids were prepared by modifed active silica nanoparticles and surfactant BSSB-12.The dispersion stability tests showed that the hydraulic radius of nanofuids was 58.59 nm and the zeta potential was−48.39 mV.The active nanofuids can simultaneously regulate liquid-liquid interface and solid-liquid interface.The nanofuids can reduce the oil/water interfacial tension(IFT)from 23.5 to 6.7 mN/m,and the oil/water/solid contact angle was altered from 42°to 145°.The spontaneous imbibition tests showed that the oil recovery of 0.1 wt%active nanofuids was 20.5%and 8.5%higher than that of 3 wt%NaCl solution and 0.1 wt%BSSB-12 solution.Finally,the efects of nanofuids on dynamic contact angle,dynamic interfacial tension and moduli were studied from the adsorption behavior of nanofuids at solid-liquid and liquid-liquid interface.The oil detaching and transporting are completed by synergistic efect of wettability alteration and interfacial tension reduction.The fndings of this study can help in better understanding of active nanofuids for EOR in ultra-low permeability reservoirs.展开更多
Due to the low permeability of tight reservoirs,throats play a significant role in controlling fluid flow.Although many studies have been conducted to investigate fluid flow in throats in the microscale domain,compara...Due to the low permeability of tight reservoirs,throats play a significant role in controlling fluid flow.Although many studies have been conducted to investigate fluid flow in throats in the microscale domain,comparatively fewer works have been devoted to study the effect of adsorption boundary layer(ABL)in throats based on the digital rock method.By considering an ABL,we investigate its effects on fluid flow.We build digital rock model based on computed tomography technology.Then,microscopic pore structures are extracted with watershed segmentation and pore geometries are meshed through Delaunay triangulation approach.Finally,using the meshed digital simulation model and finite element method,we investigate the effects of viscosity and thickness of ABL on microscale flow.Our results demonstrate that viscosity and thickness of ABL are major factors that significantly hinder fluid flow in throats.展开更多
To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom...To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.展开更多
High-performance water-based drilling fluids(HPWBFs)are essential to wellbore stability in shale gas exploration and development.Laponite is a synthetic hectorite clay composed of disk-shaped nanoparticles.This paper ...High-performance water-based drilling fluids(HPWBFs)are essential to wellbore stability in shale gas exploration and development.Laponite is a synthetic hectorite clay composed of disk-shaped nanoparticles.This paper analyzed the application potential of laponite in HPWBFs by evaluating its shale inhibition,plugging and lubrication performances.Shale inhibition performance was studied by linear swelling test and shale recovery test.Plugging performance was analyzed by nitrogen adsorption experiment and scanning electron microscope(SEM)observation.Extreme pressure lubricity test was used to evaluate the lubrication property.Experimental results show that laponite has good shale inhibition property,which is better than commonly used shale inhibitors,such as polyamine and KCl.Laponite can effectively plug shale pores.It considerably decreases the surface area and pore volume of shale,and SEM results show that it can reduce the porosity of shale and form a seamless nanofilm.Laponite is beneficial to increase lubricating property of drilling fluid by enhancing the drill pipes/wellbore interface smoothness and isolating the direct contact between wellbore and drill string.Besides,laponite can reduce the fluid loss volume.According to mechanism analysis,the good performance of laponite nanoparticles is mainly attributed to the disk-like nanostructure and the charged surfaces.展开更多
基金supported by the Innovation Project for Graduates in UPC(Grant YCX2019016)the National Natural Science Foundation of China(Nos.51774306 and 51974346)+1 种基金the Science and Technology Support Plan for Youth Innovation of University in Shandong Province under Grant 2019KJH002the Major Scientific and Technological Projects of CNPC under Grant ZD2019-183-008。
文摘Carbonate reservoirs worldwide are complex in structure,diverse in form,and highly heterogeneous.Based on these characteristics,the reservoir stimulation technologies and fluid flow characteristics of carbonate reservoirs are briefly described in this study.The development methods and EOR technologies of carbonate reservoirs are systematically summarized,the relevant mechanisms are analyzed,and the application status of oil fields is catalogued.The challenges in the development of carbonate reservoirs are discussed,and future research directions are explored.In the current development processes of carbonate reservoirs,water flooding and gas flooding remain the primary means but are often prone to channeling problems.Chemical flooding is an effective method of tertiary oil recovery,but the harsh formation conditions require high-performance chemical agents.The application of emerging technologies can enhance the oil recovery efficiency and environmental friendliness to a certain extent,which is welcome in hard-to-recover areas such as heavy oil reservoirs,but the economic cost is often high.In future research on EOR technologies,flow field control and flow channel plugging will be the potential directions of traditional development methods,and the application of nanoparticles will revolutionize the chemical EOR methods.On the basis of diversified reservoir stimulation,combined with a variety of modern data processing schemes,multichannel EOR technologies are being developed to realize the systematic,intelligent,and cost-effective development of carbonate reservoirs.
基金supports from Natural Science Foundation of China(Grant No51274235)Shandong Provincial Natural Science Foundation(Grant No.ZR2019MEE120)the Major project of CNPC(Grant No.ZD2019-183-005).
文摘For improving the hole-enlarging capability,roundness and rock-breaking efficiency of the nozzle in radial jet drilling,a new structure of self-rotating nozzle was put forward.The flow structure and rock-breaking features of the self-rotating nozzle were investigated with sliding mesh model and labortary tests and also compared with the straight and the swirling integrated nozzle and multi-orifice nozzle which have been applied in radial jet drilling.The results show that the self-rotating jet is energy concentrated,has longer effective distance,better hole-enlarging capability and roundness and impacts larger circular area at the bottom of the drilling hole,compared with the other two nozzles.Forward jet flow generated from the nozzle is peak shaped,and the jet velocity attenuates slowly at the outer edge.Due to periodic rotary percussion,the pressure fluctuates periodically on rock surface,improving shear and tensile failures on the rock matrix and thereby enhancing rock-breaking efficiency.The numerical simulation results of the flow structure of the nozzle are consistent with the experiments.This study provides an innovative approach for radial jet drilling technology in the petroleum industry.
基金This work was fnancially supported by National Natural Science Foundation of China(52074333,51874337)Taishan Scholar Foundation of Shandong Province(tspd20161004)Fundamental Research Funds for the Central Universities(19CX07001A).
文摘The ultra-low permeability reservoir is regarded as an important energy source for oil and gas resource development and is attracting more and more attention.In this work,the active silica nanofuids were prepared by modifed active silica nanoparticles and surfactant BSSB-12.The dispersion stability tests showed that the hydraulic radius of nanofuids was 58.59 nm and the zeta potential was−48.39 mV.The active nanofuids can simultaneously regulate liquid-liquid interface and solid-liquid interface.The nanofuids can reduce the oil/water interfacial tension(IFT)from 23.5 to 6.7 mN/m,and the oil/water/solid contact angle was altered from 42°to 145°.The spontaneous imbibition tests showed that the oil recovery of 0.1 wt%active nanofuids was 20.5%and 8.5%higher than that of 3 wt%NaCl solution and 0.1 wt%BSSB-12 solution.Finally,the efects of nanofuids on dynamic contact angle,dynamic interfacial tension and moduli were studied from the adsorption behavior of nanofuids at solid-liquid and liquid-liquid interface.The oil detaching and transporting are completed by synergistic efect of wettability alteration and interfacial tension reduction.The fndings of this study can help in better understanding of active nanofuids for EOR in ultra-low permeability reservoirs.
基金National Natural Science Foundation of China(No.51674280,51774308,51704033,51722406,51950410591)Shandong Provincial Natural Science Foundation(ZR2019JQ21,JQ201808)+3 种基金the Fundamental Research Funds for the Central Universities(No.20CX02113A)National Science and Technology Major Project(2016ZX05014-000407)Program for Changjiang Scholars and Innovative Research Team in University(IRT_16R69)PetroChina Innovation Foundation(No.2018D-5007-0210)。
文摘Due to the low permeability of tight reservoirs,throats play a significant role in controlling fluid flow.Although many studies have been conducted to investigate fluid flow in throats in the microscale domain,comparatively fewer works have been devoted to study the effect of adsorption boundary layer(ABL)in throats based on the digital rock method.By considering an ABL,we investigate its effects on fluid flow.We build digital rock model based on computed tomography technology.Then,microscopic pore structures are extracted with watershed segmentation and pore geometries are meshed through Delaunay triangulation approach.Finally,using the meshed digital simulation model and finite element method,we investigate the effects of viscosity and thickness of ABL on microscale flow.Our results demonstrate that viscosity and thickness of ABL are major factors that significantly hinder fluid flow in throats.
基金support of the National Key Research and Development Program of China(2021YFE0111400)the Shandong provincial natural science foundation(No.ZR2019MEE120)the horizon programme of the EU's funding of the ORCH YD project,EU-H2020(101006752-ORCHYD).
文摘To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.
基金The authors are thankful to the National Natural Science Foundation of China(U1762212,51904329,41902323)CNPC Science and Technology Project(No.2018A-3907)+4 种基金Shandong Natural Science Foundation(ZR2019BEE002)the Opening Fund of Key Laboratory of Unconventional Oil and Gas Development(China University of Petroleum(East China))Ministry of Education(19CX05005A-7)the Fundamental Research Funds for the Central Universities(No.18CX02171A)Scientific Research Foundation for the Introduction of Talents(YJ20170014)。
文摘High-performance water-based drilling fluids(HPWBFs)are essential to wellbore stability in shale gas exploration and development.Laponite is a synthetic hectorite clay composed of disk-shaped nanoparticles.This paper analyzed the application potential of laponite in HPWBFs by evaluating its shale inhibition,plugging and lubrication performances.Shale inhibition performance was studied by linear swelling test and shale recovery test.Plugging performance was analyzed by nitrogen adsorption experiment and scanning electron microscope(SEM)observation.Extreme pressure lubricity test was used to evaluate the lubrication property.Experimental results show that laponite has good shale inhibition property,which is better than commonly used shale inhibitors,such as polyamine and KCl.Laponite can effectively plug shale pores.It considerably decreases the surface area and pore volume of shale,and SEM results show that it can reduce the porosity of shale and form a seamless nanofilm.Laponite is beneficial to increase lubricating property of drilling fluid by enhancing the drill pipes/wellbore interface smoothness and isolating the direct contact between wellbore and drill string.Besides,laponite can reduce the fluid loss volume.According to mechanism analysis,the good performance of laponite nanoparticles is mainly attributed to the disk-like nanostructure and the charged surfaces.
