Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|r...Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|rich hemipelagic sediments offers a unique opportunity to study the variability of the East Asian monsoon, the erosion and weathering of tectonic orogens as well as its possible impact on global and regional climate.Leg 184, the first deep\|sea drilling leg to the seas off China, cored 17 holes at 6 sites in the northern and southern parts of the SCS and recovered 5463m of sediment. The drilling of hemipelagic sediments was exceptionally successful, with core recovery averaging 83%～101%. The 32Ma sequence of deep\|sea sediments recovered during Leg 184 covers almost the entire environmental history of the SCS since its opening. The abnormally high sediment accumulation rates in the Oligocene section are correlative with the incipient sea floor spreading. The bathyal nature of the Oligocenefauna implies that rifting occurred in the Eocene or earlier. Faunal changesfrom the early to late Oligocene are indicative of basin deepening, a trend thatis even more evident in the Miocene section. Sediment deformation, abruptlithologic changes, and a hiatus occur near the Oligocene/Miocene boundary,representing one of the most significant events in the tectonic andenvironmental history of the SCS.展开更多
Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress grad...Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.展开更多
The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental ...The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.展开更多
The economics of drilling wells is important as we drill deeper wells whether offshore or onshore. Drilling-related problems,including stuck pipe,lost circulation,and excessive mud cost,show the need for better drilli...The economics of drilling wells is important as we drill deeper wells whether offshore or onshore. Drilling-related problems,including stuck pipe,lost circulation,and excessive mud cost,show the need for better drilling technology.If we can solve these problems,the economics of drilling the wells will improve,thus enabling the industry to drill wells that were previously uneconomical.Managed pressure drilling techniques,at one time,having展开更多
Due to specific properties arising from their structure (high ductility, high toughness,strong tenacious and low heat conductivity), the stainless steels have poor machinability. The drilling of the stainless steels b...Due to specific properties arising from their structure (high ductility, high toughness,strong tenacious and low heat conductivity), the stainless steels have poor machinability. The drilling of the stainless steels becomes the machining difficulty for their serious work-hardening and abrasion of tools. In this paper, the austenitic stainless steel is used as the work-piece to perform the contrastive experiments with the TiN coated and TiAlN-coated high-speed steel drills. The cutting force, torque, cutting temperature, and the abrasion of drills and tool life are tested and analyzed in the process of high-speed drilling. Experiment results show the effect of drilling speed on cutting force, cutting temperature, and drill wear. TiAlN-coated drills demonstrate better performances in high speed drilling. The research results will be of great benefit in the selection of drills and in the control of tool wear in high speed drilling of stainless steels.展开更多
The phenomenon of heat accumulation and transportation in the composite materials is a very typical and critical issue during drilling process.In this study,a three-dimensional temperature field prediction model is pr...The phenomenon of heat accumulation and transportation in the composite materials is a very typical and critical issue during drilling process.In this study,a three-dimensional temperature field prediction model is proposed using finite difference method,based on the partly homogenization hypothesis of material,to predict temperature field in the process of drilling unidirectional carbon fiber/epoxy(C/E)composites.According to the drilling feed motion,drilling process is divided into four stages to study the temperature distributing characteristics.The results show that the temperature distribution predicted by numerical study has a good agreement with the experimental results.The temperature increases with increasing the drilling depth,and the burn phenomena is observed due to the heat accumulation,especially at the drill exit.Due to the fiber orientation,an elliptical shape of the temperature field along the direction is found for both numerical and experimental studies of C/E composites drilling process.展开更多
The stability and nonlinear dynamic behavior of drilling shaft system in copper stave deep hole drilling were analyzed. The effects of the fluctuation of the cutting force, the mass eccentricity and the hydrodynamic f...The stability and nonlinear dynamic behavior of drilling shaft system in copper stave deep hole drilling were analyzed. The effects of the fluctuation of the cutting force, the mass eccentricity and the hydrodynamic forces of cutting fluid could be taken into consideration in the model of drilling shaft system. Based on the isoparametric finite element method, the variational form of Reynolds equation in hydrodynamic fluid was used to calculate nonlinear hydrodynamic forces and their Jacobian matrices simultaneously. In the stability analysis, a new shooting method for rapidly determining the periodic orbit of the nonlinear drilling shaft system and its period was presented by rebuilding the traditional shooting method and changing the time scale. Through the combination of theories with experiment, the correctness and effectiveness of the above methods are verified by using the Floquet theory. The results show that the mass eccentricity can inhibit the whirling motion of drilling shaft to some extent.展开更多
This paper describes a series of plugging agents which have been developed these years by the authors. The features of these agents can bestated as: (1) Stopping losses without stopping drilling; (2) High ratio of suc...This paper describes a series of plugging agents which have been developed these years by the authors. The features of these agents can bestated as: (1) Stopping losses without stopping drilling; (2) High ratio of success; (3) Improving fluids properties; (4) Suiting to many types of losses, even large cracks and caves; (5) Perfect efficiency in different conditions of pollution such as calcium, salt pollution and high temperature; (6) Sufficient resources of raw materials, nopoison, noharm, no pollution to the environment; (7) Convenience in use; (8) Lower cost. The properties, mechanisms and applications of these agents are also described in this paper.展开更多
Heat energy generated during machining has been found to have a greater influence on determining the machinability of the materials.In this work,magnesium-based silicon carbide composite,which has been identified as a...Heat energy generated during machining has been found to have a greater influence on determining the machinability of the materials.In this work,magnesium-based silicon carbide composite,which has been identified as a suitable lightweight application material,is prepared with the weight ratio of 90:10 by a stir casting process.Conventionally available HSS drill tools with different diameters of 4,6 and 8 mm are used to perform the drilling operations with governing parameters of spindle speed,feed rate and constant depth of cut.Thermal image camera of the FLIR E60 series is used to measure the temperature variation in the cutting zone at different operating conditions.The influences of machining temperature on chip morphology,tool wear and surface profile of the machined samples are investigated.Spindle speed has been found to have a significant effect on machining temperature.When spindle speed increases,the diameter of drill tool increases the tool wear and surface profile,respectively.Both abrasion and adhesive type of wears are observed in the drill tool.Further,change from abrasion to adhesive wear is noticed with the increase of the diameter of the drill tool.Surface plots are drawn with respect to the interaction of governing parameters along with the working temperatures obtained under different machining conditions.展开更多
Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pr...Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pressure,complicated structure and anisotropic,high flow-resistance and micro pore throats etc,.Generally they also have lots of natural micro fractures,probably leading to stress sensibility.Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations.Once damaged,formation permeability can rarely recovered.Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%.Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed.Also some feasible precaution or treating approaches of water-blocking were put forward.In a laboratory setting,a new multi-functional drilling fluid composed mainly of amphion polymer,sulfonation polymer,high effectively preventive water-blocking surfactants,ideal packing temporary bridging agents(TBA) and film-forming agents,etc.,were developed.New low-damage drilling fluids has many advantages,such as good rheological properties,excellent effectiveness of water-blocking prevention,good temporary plugging effect,low filtration and ultra-low permeability(API filtration≤5 mL,HTHP filtration≤10 mL,mud cake frictional coefficient≤0.14,permeability recovery>81%),can efficiently prevent or minimize damage,preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability,the only one developing integrated condense gas field.Some references can be provided to similar reservoir formations.展开更多
All underwater drilling and blasting operations generate seismic waves.However,due to a lack of suitable vibration sensing instruments,most studies on the propagation of seismic waves have been limited to shorelines n...All underwater drilling and blasting operations generate seismic waves.However,due to a lack of suitable vibration sensing instruments,most studies on the propagation of seismic waves have been limited to shorelines near construction areas or wharfs,whereas comparatively few studies have beerconducted on the larger seafloor itself.To address this gap,a seafloor vibration sensor system was developed and applied in this study that consists of an autonomous acquisition storage terminal,soft-ware platform,and hole-plugging device that was designed to record the blasting vibration intensities received through submarine rocks at a given measurement point.Additionally,dimensional analyses were used to derive a predictive equation for the strength of blast vibrations that considered the in fluence of the water depth.By combining reliable vibration data obtained using the sensor system in submarine rock and the developed predictive equation,it was determined that the water depth was ar important factor influencing the measured vibration strength.The results using the newly derivedequation were compared to those determined using the Sadowski equation,which is commonly used on land,and it was found that predictions using the derived equation were closer to the experimental values with an average error of less than 10%,representing a significant improvement.Based on these results the developed sensor system and preliminary theoretical basis was deemed suitable for studying the propagation behavior of submarine seismic waves generated by underwater drilling and blasting operations.展开更多
During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling...During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling fluid will invade into formation along the tiny cracks induced by stress damage,and then weaken the strength of hard brittle shale.Based on this problem,a theoretical model was set up to discuss damage level of shale under uniaxial compression tests using acoustic velocity data.And specifically,considering the coupled effect of stress damage and drilling fluid,the relationship between hard brittle shale strength and elapsed time was analyzed.展开更多
It is difficult to determine the optimal weight on bit (WOB) of the double-driven bottomhole assembly (DD-BHA, with double stabilizers and a bent housing positive displacement motor (PDM)) which is employed during ver...It is difficult to determine the optimal weight on bit (WOB) of the double-driven bottomhole assembly (DD-BHA, with double stabilizers and a bent housing positive displacement motor (PDM)) which is employed during vertical and fast drilling. High WOB leads to well deviation out of control, and low WOB leads to low rate of penetration (ROP). So considering the rock physical properties, the anisotropy index function of polycrystalline diamond compact (PDC) bit was derived with the structure and cutting performance parameters of the bit, and the effect of natural hole deviation tendencies on the performance of DD-BHA resisting deviation was represented. The concept of elliptic deformation ratio was used to characterize the performance of DD-BHA resisting deviation. Eventually, a model calculating the critical WOB was established. By comparing the model predictions with the measured hole angle changes in the field, the results show that the model predictions are accurate with error less than 5.8%, which can meet the operational requirements in the projects. Furthermore, the model was adopted to justify and guide the operating conditions and parameters during drilling, which shows that the optimum WOB predicted by the model can not only control deviation but also improve ROP effectively. The model is independent on the formation characteristics of blocks, so it can be expanded widely to other oilfields.展开更多
The functions of lubricants in diamond drilling were discussedin this paper. The influences of lubricant on drilling efficiency and bit′s life were compared and analyzed with simulated drilling test and lubrication t...The functions of lubricants in diamond drilling were discussedin this paper. The influences of lubricant on drilling efficiency and bit′s life were compared and analyzed with simulated drilling test and lubrication test apparatus. Lubricating mechanisms were also discussed.展开更多
Underbalanced drilling(UBD) is defined as a drilling operation in which circulating drilling fluid pressure is maintained to be lower than reservoir pore pressure.Underbalanced drilling may improve drilling efficiency...Underbalanced drilling(UBD) is defined as a drilling operation in which circulating drilling fluid pressure is maintained to be lower than reservoir pore pressure.Underbalanced drilling may improve drilling efficiency and enhance well productivity. Approximately 90%of the discovered fields in Iran are in carbonate reservoirs putting Iran as one of the largest carbonate producers in the world.Under-展开更多
Lack of potable water supply source is among the crucial problems in developing countries,especially in Arid to Semi Arid regions,like Eritrea.In such cases groundwater is the best if not the only resource to be looke...Lack of potable water supply source is among the crucial problems in developing countries,especially in Arid to Semi Arid regions,like Eritrea.In such cases groundwater is the best if not the only resource to be looked for to alleviate the problem.A Norwegian Church Aid funded groundwater development project was implemented for ten villages dispersedly located in Southern Zone of Eritrea,which are with展开更多
The challenging characteristics of shale formations often require horizontal drilling to economically develop their potential. While every shale gas play is unique, there are several best practices for the proper plan...The challenging characteristics of shale formations often require horizontal drilling to economically develop their potential. While every shale gas play is unique, there are several best practices for the proper planning and execution of a horizontal well. In planning a horizontal well, the optimal method and technology for building inclination and extending the lateral section must be determined. Properly specified logging-while-drilling tools are essential to keep the wellbore within the target formation. Planning must also focus on casing design. Doing so will help ensure stability and enable reliable and productive completions. Shales pose a challenge for these elements of well planning due to their thin strata and potentially low mechanical competence when foreign fluids are introduced. Once a plan is developed, executing it is even more important to prove a viable exploration program. Fast, efficient drilling with wellbore control and minimal torque and drag should be the priority. This may be achieved by focusing on fluid hydraulics and rheology and bottom hole assembly. Managed pressure drilling (MPD) will help fast drilling, well control and stability. If MPD can be combined with new generation rotary steerable systems that allow the drill string to maintain rotation, impressive efficiencies are possible. Modern drilling parameter analysis represents the newest opportunity for executing shale gas horizontal wells. A method for ROP analysis to improve operational parameters and equipment selection is also proposed.展开更多
For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoi...For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add展开更多
文摘Both evolution of the Asian monsoon system and the Cenozoic global cooling are thought to be closely linked to the Himalayan—Tibetan orogen. The South China Sea (SCS) with its high sedimentation rates of carbonate\|rich hemipelagic sediments offers a unique opportunity to study the variability of the East Asian monsoon, the erosion and weathering of tectonic orogens as well as its possible impact on global and regional climate.Leg 184, the first deep\|sea drilling leg to the seas off China, cored 17 holes at 6 sites in the northern and southern parts of the SCS and recovered 5463m of sediment. The drilling of hemipelagic sediments was exceptionally successful, with core recovery averaging 83%～101%. The 32Ma sequence of deep\|sea sediments recovered during Leg 184 covers almost the entire environmental history of the SCS since its opening. The abnormally high sediment accumulation rates in the Oligocene section are correlative with the incipient sea floor spreading. The bathyal nature of the Oligocenefauna implies that rifting occurred in the Eocene or earlier. Faunal changesfrom the early to late Oligocene are indicative of basin deepening, a trend thatis even more evident in the Miocene section. Sediment deformation, abruptlithologic changes, and a hiatus occur near the Oligocene/Miocene boundary,representing one of the most significant events in the tectonic andenvironmental history of the SCS.
基金Projects(51278166,51478163)supported by the National Natural Science Foundation of ChinaProject(2015B17414)supported by the Fundamental Research Funds for the Central Universities,China
文摘Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.
基金Project(50574061) supported by the National Natural Science Foundation of ChinaProject(IRT0411) supported by the Changjiang Scholars and Innovative Research Team,Ministry of Education
文摘The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.
文摘The economics of drilling wells is important as we drill deeper wells whether offshore or onshore. Drilling-related problems,including stuck pipe,lost circulation,and excessive mud cost,show the need for better drilling technology.If we can solve these problems,the economics of drilling the wells will improve,thus enabling the industry to drill wells that were previously uneconomical.Managed pressure drilling techniques,at one time,having
文摘Due to specific properties arising from their structure (high ductility, high toughness,strong tenacious and low heat conductivity), the stainless steels have poor machinability. The drilling of the stainless steels becomes the machining difficulty for their serious work-hardening and abrasion of tools. In this paper, the austenitic stainless steel is used as the work-piece to perform the contrastive experiments with the TiN coated and TiAlN-coated high-speed steel drills. The cutting force, torque, cutting temperature, and the abrasion of drills and tool life are tested and analyzed in the process of high-speed drilling. Experiment results show the effect of drilling speed on cutting force, cutting temperature, and drill wear. TiAlN-coated drills demonstrate better performances in high speed drilling. The research results will be of great benefit in the selection of drills and in the control of tool wear in high speed drilling of stainless steels.
基金Projects(51475073,51605076,51875079)supported by the National Natural Science Foundation of ChinaProject(2017YFB1301701)supported by the National Key Research and Development Program of China
文摘The phenomenon of heat accumulation and transportation in the composite materials is a very typical and critical issue during drilling process.In this study,a three-dimensional temperature field prediction model is proposed using finite difference method,based on the partly homogenization hypothesis of material,to predict temperature field in the process of drilling unidirectional carbon fiber/epoxy(C/E)composites.According to the drilling feed motion,drilling process is divided into four stages to study the temperature distributing characteristics.The results show that the temperature distribution predicted by numerical study has a good agreement with the experimental results.The temperature increases with increasing the drilling depth,and the burn phenomena is observed due to the heat accumulation,especially at the drill exit.Due to the fiber orientation,an elliptical shape of the temperature field along the direction is found for both numerical and experimental studies of C/E composites drilling process.
基金Project(2007CB707706) supported by the Major State Basic Research Development Program of ChinaProjects(2007E213,2007E203) supported by the Natural Science Foundation of Shaanxi Province,China
文摘The stability and nonlinear dynamic behavior of drilling shaft system in copper stave deep hole drilling were analyzed. The effects of the fluctuation of the cutting force, the mass eccentricity and the hydrodynamic forces of cutting fluid could be taken into consideration in the model of drilling shaft system. Based on the isoparametric finite element method, the variational form of Reynolds equation in hydrodynamic fluid was used to calculate nonlinear hydrodynamic forces and their Jacobian matrices simultaneously. In the stability analysis, a new shooting method for rapidly determining the periodic orbit of the nonlinear drilling shaft system and its period was presented by rebuilding the traditional shooting method and changing the time scale. Through the combination of theories with experiment, the correctness and effectiveness of the above methods are verified by using the Floquet theory. The results show that the mass eccentricity can inhibit the whirling motion of drilling shaft to some extent.
文摘This paper describes a series of plugging agents which have been developed these years by the authors. The features of these agents can bestated as: (1) Stopping losses without stopping drilling; (2) High ratio of success; (3) Improving fluids properties; (4) Suiting to many types of losses, even large cracks and caves; (5) Perfect efficiency in different conditions of pollution such as calcium, salt pollution and high temperature; (6) Sufficient resources of raw materials, nopoison, noharm, no pollution to the environment; (7) Convenience in use; (8) Lower cost. The properties, mechanisms and applications of these agents are also described in this paper.
文摘Heat energy generated during machining has been found to have a greater influence on determining the machinability of the materials.In this work,magnesium-based silicon carbide composite,which has been identified as a suitable lightweight application material,is prepared with the weight ratio of 90:10 by a stir casting process.Conventionally available HSS drill tools with different diameters of 4,6 and 8 mm are used to perform the drilling operations with governing parameters of spindle speed,feed rate and constant depth of cut.Thermal image camera of the FLIR E60 series is used to measure the temperature variation in the cutting zone at different operating conditions.The influences of machining temperature on chip morphology,tool wear and surface profile of the machined samples are investigated.Spindle speed has been found to have a significant effect on machining temperature.When spindle speed increases,the diameter of drill tool increases the tool wear and surface profile,respectively.Both abrasion and adhesive type of wears are observed in the drill tool.Further,change from abrasion to adhesive wear is noticed with the increase of the diameter of the drill tool.Surface plots are drawn with respect to the interaction of governing parameters along with the working temperatures obtained under different machining conditions.
基金Project(50574061) supported by the National Natural Science Foundation of China
文摘Low-permeability dense reservoirs,including micro-fractured reservoirs,are commonly characterized by high content of clay substances,high original water saturation,high sensitivity to invasive fluids,high capillary pressure,complicated structure and anisotropic,high flow-resistance and micro pore throats etc,.Generally they also have lots of natural micro fractures,probably leading to stress sensibility.Main damaging factors in such reservoirs are water-sensibility and water-blocking caused by invasive fluids during drilling and production operations.Once damaged,formation permeability can rarely recovered.Numerous studies have shown that damaging extent of water-blocking ranges from 70% to 90%.Main damaging mechanisms and influencing factors of water-blocking were systematically analyzed.Also some feasible precaution or treating approaches of water-blocking were put forward.In a laboratory setting,a new multi-functional drilling fluid composed mainly of amphion polymer,sulfonation polymer,high effectively preventive water-blocking surfactants,ideal packing temporary bridging agents(TBA) and film-forming agents,etc.,were developed.New low-damage drilling fluids has many advantages,such as good rheological properties,excellent effectiveness of water-blocking prevention,good temporary plugging effect,low filtration and ultra-low permeability(API filtration≤5 mL,HTHP filtration≤10 mL,mud cake frictional coefficient≤0.14,permeability recovery>81%),can efficiently prevent or minimize damage,preserve natural formation and enhance comprehensive development-investment effect in TUHA Jurassic dense sandstone reservoir formation with low-permeability,the only one developing integrated condense gas field.Some references can be provided to similar reservoir formations.
文摘All underwater drilling and blasting operations generate seismic waves.However,due to a lack of suitable vibration sensing instruments,most studies on the propagation of seismic waves have been limited to shorelines near construction areas or wharfs,whereas comparatively few studies have beerconducted on the larger seafloor itself.To address this gap,a seafloor vibration sensor system was developed and applied in this study that consists of an autonomous acquisition storage terminal,soft-ware platform,and hole-plugging device that was designed to record the blasting vibration intensities received through submarine rocks at a given measurement point.Additionally,dimensional analyses were used to derive a predictive equation for the strength of blast vibrations that considered the in fluence of the water depth.By combining reliable vibration data obtained using the sensor system in submarine rock and the developed predictive equation,it was determined that the water depth was ar important factor influencing the measured vibration strength.The results using the newly derivedequation were compared to those determined using the Sadowski equation,which is commonly used on land,and it was found that predictions using the derived equation were closer to the experimental values with an average error of less than 10%,representing a significant improvement.Based on these results the developed sensor system and preliminary theoretical basis was deemed suitable for studying the propagation behavior of submarine seismic waves generated by underwater drilling and blasting operations.
基金Project(U262201)supported by National Natural Science Foundation of China
文摘During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling fluid will invade into formation along the tiny cracks induced by stress damage,and then weaken the strength of hard brittle shale.Based on this problem,a theoretical model was set up to discuss damage level of shale under uniaxial compression tests using acoustic velocity data.And specifically,considering the coupled effect of stress damage and drilling fluid,the relationship between hard brittle shale strength and elapsed time was analyzed.
基金Projects(50804040,51004082)supported by the National Natural Science Foundation of China
文摘It is difficult to determine the optimal weight on bit (WOB) of the double-driven bottomhole assembly (DD-BHA, with double stabilizers and a bent housing positive displacement motor (PDM)) which is employed during vertical and fast drilling. High WOB leads to well deviation out of control, and low WOB leads to low rate of penetration (ROP). So considering the rock physical properties, the anisotropy index function of polycrystalline diamond compact (PDC) bit was derived with the structure and cutting performance parameters of the bit, and the effect of natural hole deviation tendencies on the performance of DD-BHA resisting deviation was represented. The concept of elliptic deformation ratio was used to characterize the performance of DD-BHA resisting deviation. Eventually, a model calculating the critical WOB was established. By comparing the model predictions with the measured hole angle changes in the field, the results show that the model predictions are accurate with error less than 5.8%, which can meet the operational requirements in the projects. Furthermore, the model was adopted to justify and guide the operating conditions and parameters during drilling, which shows that the optimum WOB predicted by the model can not only control deviation but also improve ROP effectively. The model is independent on the formation characteristics of blocks, so it can be expanded widely to other oilfields.
文摘The functions of lubricants in diamond drilling were discussedin this paper. The influences of lubricant on drilling efficiency and bit′s life were compared and analyzed with simulated drilling test and lubrication test apparatus. Lubricating mechanisms were also discussed.
文摘Underbalanced drilling(UBD) is defined as a drilling operation in which circulating drilling fluid pressure is maintained to be lower than reservoir pore pressure.Underbalanced drilling may improve drilling efficiency and enhance well productivity. Approximately 90%of the discovered fields in Iran are in carbonate reservoirs putting Iran as one of the largest carbonate producers in the world.Under-
文摘Lack of potable water supply source is among the crucial problems in developing countries,especially in Arid to Semi Arid regions,like Eritrea.In such cases groundwater is the best if not the only resource to be looked for to alleviate the problem.A Norwegian Church Aid funded groundwater development project was implemented for ten villages dispersedly located in Southern Zone of Eritrea,which are with
文摘The challenging characteristics of shale formations often require horizontal drilling to economically develop their potential. While every shale gas play is unique, there are several best practices for the proper planning and execution of a horizontal well. In planning a horizontal well, the optimal method and technology for building inclination and extending the lateral section must be determined. Properly specified logging-while-drilling tools are essential to keep the wellbore within the target formation. Planning must also focus on casing design. Doing so will help ensure stability and enable reliable and productive completions. Shales pose a challenge for these elements of well planning due to their thin strata and potentially low mechanical competence when foreign fluids are introduced. Once a plan is developed, executing it is even more important to prove a viable exploration program. Fast, efficient drilling with wellbore control and minimal torque and drag should be the priority. This may be achieved by focusing on fluid hydraulics and rheology and bottom hole assembly. Managed pressure drilling (MPD) will help fast drilling, well control and stability. If MPD can be combined with new generation rotary steerable systems that allow the drill string to maintain rotation, impressive efficiencies are possible. Modern drilling parameter analysis represents the newest opportunity for executing shale gas horizontal wells. A method for ROP analysis to improve operational parameters and equipment selection is also proposed.
文摘For decades,some geological formations have been drilled with a drilling fluid that exerted a bottom-hole pressure less than the formation pressure,allowing formation fluids-oil,gas and water-to flow from the reservoir into the well bore while drilling proceeds.A growing number of Iranian case histories have shown that when UBD is applied in the right reservoir with the proper planning,well productivity can be orders of magnitude greater than with a conventional well drilled into the same formation.Wells drilled underbalanced have been proven to add
