The research progress of deep and ultra-deep drilling fluid technology systematically reviewed,the key problems existing are analyzed,and the future development direction is proposed.In view of the high temperature,hi...The research progress of deep and ultra-deep drilling fluid technology systematically reviewed,the key problems existing are analyzed,and the future development direction is proposed.In view of the high temperature,high pressure and high stress,fracture development,wellbore instability,drilling fluid lost circulation and other problems faced in the process of deep and ultra-deep complex oil and gas drilling,scholars have developed deep and ultra-deep high-temperature and high-salt resistant water-based drilling fluid technology,high-temperature resistant oil-based/synthetic drilling fluid technology,drilling fluid technology for reservoir protection and drilling fluid lost circulation control technology.However,there are still some key problems such as insufficient resistance to high temperature,high pressure and high stress,wellbore instability and serious lost circulation.Therefore,the development direction of deep and ultra-deep drilling fluid technology in the future is proposed:(1)The technology of high-temperature and high-salt resistant water-based drilling fluid should focus on improving high temperature stability,improving rheological properties,strengthening filtration control and improving compatibility with formation.(2)The technology of oil-based/synthetic drilling fluid resistant to high temperature should further study in the aspects of easily degradable environmental protection additives with low toxicity such as high temperature stabilizer,rheological regulator and related supporting technologies.(3)The drilling fluid technology for reservoir protection should be devoted to the development of new high-performance additives and materials,and further improve the real-time monitoring technology by introducing advanced sensor networks and artificial intelligence algorithms.(4)The lost circulation control of drilling fluid should pay more attention to the integration and application of intelligent technology,the research and application of high-performance plugging materials,the exploration of diversified plugging techniques and methods,and the improvement of environmental protection and production safety awareness.展开更多
Aiming at the problems of large load of rotation drive system,low efficiency of torque transmission and high cost for operation and maintenance of liner steering drilling system for the horizontal well,a new method of...Aiming at the problems of large load of rotation drive system,low efficiency of torque transmission and high cost for operation and maintenance of liner steering drilling system for the horizontal well,a new method of liner differential rotary drilling with double tubular strings in the horizontal well is proposed.The technical principle of this method is revealed,supporting tools such as the differential rotation transducer,composite rotary steering system and the hanger are designed,and technological process is optimized.A tool face control technique of steering drilling assembly is proposed and the calculation model of extension limit of liner differential rotary drilling with double tubular strings in horizontal well is established.These results show that the liner differential rotary drilling with double tubular strings is equipped with measurement while drilling(MWD)and positive displacement motor(PDM),and directional drilling of horizontal well is realized by adjusting rotary speed of drill pipe to control the tool face of PDM.Based on the engineering case of deep coalbed methane horizontal well in the eastern margin of Ordos Basin,the extension limit of horizontal drilling with double tubular strings is calculated.Compared with the conventional liner drilling method,the liner differential rotary drilling with double tubular strings increases the extension limit value of horizontal well significantly.The research findings provide useful reference for the integrated design and control of liner completion and drilling of horizontal wells.展开更多
The study considers gas compression properties,gas slippage,back pressure(BP),phase transition(PT),well depth,and differences in gas-liquid physical properties.A new temperature model for multiphase flow is proposed b...The study considers gas compression properties,gas slippage,back pressure(BP),phase transition(PT),well depth,and differences in gas-liquid physical properties.A new temperature model for multiphase flow is proposed by considering phase transition in the drilling process.The mathematical model of multiphase flow is solved using the finite difference method with annulus mesh division for grid nodes,and a module for multiphase flow calculation and analysis is developed.Numerical results indicate that the temperature varies along the annulus with the variation of gas influx at the bottom of the well.During the process of controlled pressure drilling,as gas slips along the annulus to the wellhead,its volume continuously expands,leading to an increase in the gas content within the annulus,and consequently,an increase in the pressure drop caused by gas slippage.The temperature increases with the increase in BP and decreases in gas influx rate and wellbore diameter.During gas influx,the thermal conductivity coefficient for the gas-drilling mud two phases is significantly weakened,resulting in a considerable change in temperature along the annulus.In the context of MPD,the method of slightly changing the temperature along the annulus by controlling the back pressure is feasible.展开更多
The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(R...The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(RCZ) is built. The formula for an ultimate cutting force is established based on the limit equilibrium principle. The relationship between digital drilling parameters(DDP) and the c-φ parameter(DDP-cφ formula, where c refers to the cohesion and φ refers to the internal friction angle) is derived, and the response of drilling parameters and cutting ratio to the strength parameters is analyzed. The drillingbased measuring method for the c-φ parameter of rock is constructed. The laboratory verification test is then completed, and the difference in results between the drilling test and the compression test is less than 6%. On this basis, in-situ rock drilling tests in a traffic tunnel and a coal mine roadway are carried out, and the strength parameters of the surrounding rock are effectively tested. The average difference ratio of the results is less than 11%, which verifies the effectiveness of the proposed method for obtaining the strength parameters based on digital drilling. This study provides methodological support for field testing of rock strength parameters.展开更多
With the growth of deep drilling and the complexity of the well profile,the requirements for a more complete and efficient exploitation of productive formations increase,which increases the risk of various complicatio...With the growth of deep drilling and the complexity of the well profile,the requirements for a more complete and efficient exploitation of productive formations increase,which increases the risk of various complications.Currently,reagents based on modified natural polymers(which are naturally occurring compounds)and synthetic polymers(SPs)which are polymeric compounds created industrially,are widely used to prevent emerging complications in the drilling process.However,compared to modified natural polymers,SPs form a family of high-molecular-weight compounds that are fully synthesized by undergoing chemical polymerization reactions.SPs provide substantial flexibility in their design.Moreover,their size and chemical composition can be adjusted to provide properties for nearly all the functional objectives of drilling fluids.They can be classified based on chemical ingredients,type of reaction,and their responses to heating.However,some of SPs,due to their structural characteristics,have a high cost,a poor temperature and salt resistance in drilling fluids,and degradation begins when the temperature reaches 130℃.These drawbacks prevent SP use in some medium and deep wells.Thus,this review addresses the historical development,the characteristics,manufacturing methods,classification,and the applications of SPs in drilling fluids.The contributions of SPs as additives to drilling fluids to enhance rheology,filtrate generation,carrying of cuttings,fluid lubricity,and clay/shale stability are explained in detail.The mechanisms,impacts,and advances achieved when SPs are added to drilling fluids are also described.The typical challenges encountered by SPs when deployed in drilling fluids and their advantages and drawbacks are also discussed.Economic issues also impact the applications of SPs in drilling fluids.Consequently,the cost of the most relevant SPs,and the monomers used in their synthesis,are assessed.Environmental impacts of SPs when deployed in drilling fluids,and their manufacturing processes are identified,together with advances in SP-treatment methods aimed at reducing those impacts.Recommendations for required future research addressing SP property and performance gaps are provided.展开更多
With the continuous increase in vertical depths and horizontal displacements of directional wells,the difficulties of drilling operations continue to increase,and more accurate methods of drilling difficulty evaluatio...With the continuous increase in vertical depths and horizontal displacements of directional wells,the difficulties of drilling operations continue to increase,and more accurate methods of drilling difficulty evaluation are needed.In this paper,a drilling difficulty evaluation method is built by combining drilling limit model and expert evaluation.Firstly,the concept of drilling difficulty index is introduced,and the method to calculate drilling difficulty index is established.Next,the meanings of five drilling difficulty levels are explained and the optimization design method with drilling difficulty as the target is built.At last,the theoretical model is applied to the extended-reach drilling of the Liuhua oilfield in the South China Sea,in which drilling difficulties are evaluated and the relationship between drilling difficulty and development control radius is revealed.The results indicate that extended-reach drilling in the Liuhua oilfield is on the“normal”difficulty level on average,rotary drilling in 8_(1/2)-in.section is the most difficult,and the main constraint conditions are excessive torque and high friction.Through technology upgradation,the drilling difficulties are decreased,the development control radius increases from 6.6 to 11.4 km,and the maximum horizontalto-vertical ratio increases from 5.3 to 8.7.Then,the development wells in marginal oilfields and adjustment wells in old oilfields can be drilled on“normal”difficulty level.Therefore,technology upgradation,especially drilling rig upgradation,is the most important development direction for extended-reach drilling in the South China Sea.展开更多
To address the two critical issues of evaluating the necessity of implementing cooling techniques and achieving real-time temperature control of drilling fluids underground in the current drilling fluid cooling techno...To address the two critical issues of evaluating the necessity of implementing cooling techniques and achieving real-time temperature control of drilling fluids underground in the current drilling fluid cooling technology,we first established a temperature and pressure coupled downhole heat transfer model,which can be used in both water-based and oil-based drilling fluid.Then,fourteen factors,which could affect wellbore temperature,were analyzed.Based on the standard deviation of the downhole temperature corresponding to each influencing factor,the influence of each factor was quantified.The influencing factors that can be used to guide the drilling fluid's cooling technology were drilling fluid thermal conductivity,drilling fluid heat capacity,drilling fluid density,drill strings rotation speed,pump rate,viscosity,ROP,and injection temperature.The nondominated sorting genetic algorithm was used to optimize these six parameters,but the optimization process took 182 min.Combining these eight parameters'influence rules with the nondominated sorting genetic algorithm can reduce the optimization time to 108 s.Theoretically,the downhole temperature has been demonstrated to increase with the inlet temperature increasing linearly under quasi-steady states.Combining this law and PID,the downhole temperature can be controlled,which can reduce the energy for cooling the surface drilling fluid and can ensure the downhole temperature reaches the set value as soon as possible.展开更多
Thermo-responsive nanocomposites have recently emerged as potential nanoplugging agents for shale stabilization in high-temperature water-based drilling fluids(WBDFs). However, their inhibitory properties have not bee...Thermo-responsive nanocomposites have recently emerged as potential nanoplugging agents for shale stabilization in high-temperature water-based drilling fluids(WBDFs). However, their inhibitory properties have not been very effective in high-temperature drilling operations. Thermo-responsive Janus nanocomposites are expected to strongly interact with clay particles from the inward hemisphere of nanomaterials, which drive the establishment of a tighter hydrophobic membrane over the shale surface at the outward hemisphere under geothermal conditions for shale stabilization. This work combines the synergistic benefits of thermo-responsive and zwitterionic nanomaterials to synchronously enhance the chemical inhibitions and plugging performances in shale under harsh conditions. A novel thermoresponsive Janus nanosilica(TRJS) exhibiting zwitterionic character was synthesized, characterized,and assessed as shale stabilizer for WBDFs at high temperatures. Compared to pristine nanosilica(Si NP)and symmetrical thermo-responsive nanosilica(TRS), TRJS exhibited anti-polyelectrolyte behaviour, in which electrolyte ions screened the electrostatic attraction between the charged particles, potentially stabilizing nanomaterial in hostile shaly environments(i.e., up to saturated brine or API brine). Macroscopically, TRJS exhibited higher chemical inhibition than Si NP and TRS in brine, prompting a better capability to control pressure penetration. TRJS adsorbed onto the clay surface via chemisorption and hydrogen bonding, and the interactions became substantial in brine, according to the results of electrophoretic mobility, surface wettability, and X-ray diffraction. Thus, contributing to the firm trapping of TRJS into the nanopore structure of the shale, triggering the formation of a tight hydrophobic membrane over the shale surface from the outward hemisphere. The addition of TRJS into WBDF had no deleterious effect on fluid properties after hot-treatment at 190℃, implying that TRJS could find potential use as a shale stabilizer in WBDFs in hostile environments.展开更多
With increasing drilling depth and large dosage of weighting materials,drilling fluids with high solid content are characterized by poor stability,high viscosity,large water loss,and thick mud cake,easier leading to r...With increasing drilling depth and large dosage of weighting materials,drilling fluids with high solid content are characterized by poor stability,high viscosity,large water loss,and thick mud cake,easier leading to reservoir damage and wellbore instability.In this paper,micronized barite(MB)was modified(mMB)by grafting with hydrophilic polymer onto the surface through the free radical polymerization to displace conventional API barite partly.The suspension stability of water-based drilling fluids(WBDFs)weighted with API barite:mMB=2:1 in 600 g was significantly enhanced compared with that with API barite/WBDFs,exhibiting the static sag factor within 0.54 and the whole stability index of 2.The viscosity and yield point reached the minimum,with a reduction of more than 40%compared with API barite only at the same density.Through multi-stage filling and dense accumulation of weighting materials and clays,filtration loss was decreased,mud cake quality was improved,and simultaneously it had great reservoir protection performance,and the permeability recovery rate reached 87%.In addition,it also effectively improved the lubricity of WBDFs.The sticking coefficient of mud cake was reduced by 53.4%,and the friction coefficient was 0.2603.Therefore,mMB can serve as a versatile additive to control the density,rheology,filtration,and stability of WBDFs weighted with API barite,thus regulating comprehensive performance and achieving reservoir protection capacity.This work opened up a new path for the productive drilling of extremely deep and intricate wells by providing an efficient method for managing the performance of high-density WBDFs.展开更多
In extended-reach or long-horizontal drilling,cuttings usually deposit at the bottom of the annulus.Once cuttings accumulate to a certain thickness,complex problems such as excessive torque and drag,tubing buckling,an...In extended-reach or long-horizontal drilling,cuttings usually deposit at the bottom of the annulus.Once cuttings accumulate to a certain thickness,complex problems such as excessive torque and drag,tubing buckling,and pipe stuck probably occur,which results in a lot of non-productive time and remedial operations.Cuttings bed remover can efficiently destroy deposited cuttings in time through hydraulic and mechanical stirring effects.This paper aims to build a method for hole cleaning evaluation and installation spacing optimization of cuttings bed remover to improve the wellbore cleaning effect.Firstly,a Computational Fluid Dynamics approach with Eulerian—Eulerian multiphase model was utilized to investigate the mechanism of cuttings transportation,and a new type of cuttings bed remover was designed.Next,an evaluation method of hole cleaning effect of remover was established.After that,the effects of several drilling parameters on hole cleaning including flow rate of drilling fluid,rotational speed of drillpipe,rate of penetration,wellbore size,rheological property of drilling fluid,and remover eccentricity on the performance of cuttings bed remover were investigated.The results demonstrate that the new type of remover with streamline blade performs better than conventional removers.The efficiency of hole cleaning is greatly improved by increasing the rotational speed of drillpipe,flow rate of drilling fluid,remover eccentricity,and 6 rpm Fann dial reading for drilling fluid.While higher rate of penetration and large wellbore size result in worse hole cleaning.These findings can serve as an important guide for the structure optimization design of cuttings bed remover and installation spacing of removers.展开更多
Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detect...Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detection(DPD)system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod,geophones at the tunnel face,a laser rangefinder,and an onsite computer.A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling.A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method.Time-frequency analysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seismic exploration wavelet.A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained.Both the borehole core and optical image validate the inverted P-wave velocity field.A numerical simulation of a checkerboard benchmark model is used to test the tomography method.The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.展开更多
The environmental hazards and"carbon footprint"of oil and gas drilling can be significantly reduced by replacing traditional petroleum-based chemical additives with natural materials derived from plants and ...The environmental hazards and"carbon footprint"of oil and gas drilling can be significantly reduced by replacing traditional petroleum-based chemical additives with natural materials derived from plants and animals.This paper explored for the first time the interaction mechanism between natural rubber latex(NRL)and bentonite suspensions(BTs)through a series of characterization experiments,as well as the potential applications in water-based drilling fluids(WBDF).The gel viscoelasticity experiments showed that NRL could decrease the consistency coefficient(k)and flow index(n)of BTs,and enhance the shear thinning performance of BTs as pseudo-plastic fluids.In addition,0.5 w/v%NRL not only increased the critical yield stress and strengthened the structural strength between the bentonite particles,but also facilitated the compatibility of pressure loss and flow efficiency.The evaluation of colloidal stability and WBDF performance indicated that NRL particles could promote the hydration and charge stability on the surface of BTs particles,and optimize the particle size distribution and flow resistance of WBDF under the"intercalation-exfoliation-encapsulation"synergistic interaction.Moreover,NRL can improve the rheological properties of WBDF at high temperatures(<150.C),and form a dense blocking layer by bridging and sealing the pores and cracks of the filter cake,which ultimately reduces the permeability of the cake and the filtration loss of WBDF.展开更多
Using pressure-preserved coring technique to determine in-situ gas content provides a more precise assessment of gas resource reserves and safeguard of mining safety in coal seams. How coring technique and depth affec...Using pressure-preserved coring technique to determine in-situ gas content provides a more precise assessment of gas resource reserves and safeguard of mining safety in coal seams. How coring technique and depth affect the determination of gas content is unclear due to borehole zoning rupture caused by roadway excavation and drilling disturbance. To this end, a proposed coupling model of stress distribution and gas migration was simulated and validated by FLAC^(3D) and COMSOL Multiphysics considering superposition effects of roadway excavation and drilling disturbance. The findings indicate that the roadway surrounding rock displays distinct zoning features including stress relief zone, stress concentration zone that is composed of plastic zone, elastic zone, and original stress zone;and the broken situations depending on the borehole peeping are consistent with the corresponding simulation results.On this basis, this study proposes a set of drilling coring depth calculation and prediction model for the gas desorption affected area under engineering disturbance. Optimal depth of coring drilling is not only approach to the in-situ coal bulk, but also can get the balance of the drilling workload and cost controlling. According to the typical mine site geological conditions and the numerical simulation results in this study, if the roadway excavation time is ~1 year, it is recommended that the pressure-preserved coring depth should be greater than 17 m.展开更多
For the analysis of the formation damage caused by the compound function of drilling fluid and fracturing fluid,the prediction method for dynamic invasion depth of drilling fluid is developed considering the fracture ...For the analysis of the formation damage caused by the compound function of drilling fluid and fracturing fluid,the prediction method for dynamic invasion depth of drilling fluid is developed considering the fracture extension due to shale minerals erosion by oil-based drilling fluid.With the evaluation for the damage of natural and hydraulic fractures caused by mechanical properties weakening of shale fracture surface,fracture closure and rock powder blocking,the formation damage pattern is proposed with consideration of the compound effect of drilling fluid and fracturing fluid.The formation damage mechanism during drilling and completion process in shale reservoir is revealed,and the protection measures are raised.The drilling fluid can deeply invade into the shale formation through natural and induced fractures,erode shale minerals and weaken the mechanical properties of shale during the drilling process.In the process of hydraulic fracturing,the compound effect of drilling fluid and fracturing fluid further weakens the mechanical properties of shale,results in fracture closure and rock powder shedding,and thus induces stress-sensitive damage and solid blocking damage of natural/hydraulic fractures.The damage can yield significant conductivity decrease of fractures,and restrict the high and stable production of shale oil and gas wells.The measures of anti-collapse and anti-blocking to accelerate the drilling of reservoir section,forming chemical membrane to prevent the weakening of the mechanical properties of shale fracture surface,strengthening the plugging of shale fracture and reducing the invasion range of drilling fluid,optimizing fracturing fluid system to protect fracture conductivity are put forward for reservoir protection.展开更多
The general layout of 6th generation semi-submersible drilling platforms is the main factor impacting the efficiency of their drilling operations. This paper provides a compound/integrated algorithm based on process f...The general layout of 6th generation semi-submersible drilling platforms is the main factor impacting the efficiency of their drilling operations. This paper provides a compound/integrated algorithm based on process flow that is aimed at improving efficiency, while giving attention to stability and safety at the same time. The paper describes the process flow of dual drilling centers and a hierarchical division of rigs based on the different modes of transportation of various drilling support systems. The general layout-centripetal overall arrangement spatially was determined based on drilling efficiency. We derived our modules according to drilling functionality; the modules became our basic layout units. We applied different layout algorithm to mark out the upper and lower decks. That is, the upper deck was designed based on the lowest transportation cost while the lower deck＇s calculations were based on the best-fit scope. Storage configurations in columns and pontoons were also considered for the layout design. Finally the center of gravity was taken into consideration and the general layout was adjusted accordingly, to result in an optimal center of gravity. The methodology of the general layout can provide a reference for implementation of domestic designs of semi-submersible rigs.展开更多
Theories established from engineering fundamentals have been of great value in supporting the design and execution of drilling operations in gas drilling where gas is used as a drilling fluid.This work presents an ove...Theories established from engineering fundamentals have been of great value in supporting the design and execution of drilling operations in gas drilling where gas is used as a drilling fluid.This work presents an overview of new theories developed in recent years for special gas drilling operations including horizontal wells.These new theories are found in the areas of gas-mixture flow hydraulics in deviated and horizontal boreholes,hole cleaning of solids accumulation,hole cleaning of formation water,flow diverging for washout control,bit orifice optimization,and depression of formation water influx.This paper provides drilling engineers with updated mathematical models and methods for optimizing design to improve gas drilling performance.展开更多
Three high-temperature resistant polymeric additives for water-based drilling fluids are designed and developed:weakly cross-linked zwitterionic polymer fluid loss reducer(WCZ),flexible polymer microsphere nano-pluggi...Three high-temperature resistant polymeric additives for water-based drilling fluids are designed and developed:weakly cross-linked zwitterionic polymer fluid loss reducer(WCZ),flexible polymer microsphere nano-plugging agent(FPM)and comb-structure polymeric lubricant(CSP).A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid was developed for deep drilling.The WCZ has a good anti-polyelectrolyte effect and exhibits the API fluid loss less than 8 mL after aging in saturated salt environment at 200°C.The FPM can reduce the fluid loss by improving the quality of the mud cake and has a good plugging effect on nano-scale pores/fractures.The CSP,with a weight average molecular weight of 4804,has multiple polar adsorption sites and exhibits excellent lubricating performance under high temperature and high salt conditions.The developed drilling fluid system with a density of 2.0 g/cm^(3)has good rheological properties.It shows a fluid loss less than 15 mL at 200°C and high pressure,a sedimentation factor(SF)smaller than 0.52 after standing at high temperature for 5 d,and a rolling recovery of hydratable drill cuttings similar to oil-based drilling fluid.Besides,it has good plugging and lubricating performance.展开更多
In recent years, numerous exploration activities of oil and gas industry have been conducted in ultra deep water. The global offshore industry is building systems today for drilling in even deeper water, progressively...In recent years, numerous exploration activities of oil and gas industry have been conducted in ultra deep water. The global offshore industry is building systems today for drilling in even deeper water, progressively using new technologies, and significantly extending existing technologies. This is the general trend in the offshore oil and gas industry. So the technology of ultra-deepwater risers, which is the main tool in drilling oil, is more and more standard. This paper manly focuses on the global analysis of the drilling risers. And it is divided into two parts, operability analysis and hang-off analysis that are used to check the design of the riser. In this paper, the rotation angle and stress of the riser in the drilling mode are calculated to determine the operability envelop. The number of the buoyancy modules has been determined and according to the API standard, all the worked out values have been checked out. From all the above, it is concluded that the operability envelop is relatively small under harsh condition and the number of the buoyancy modules is a little large. And above all, the design of this riser is successful.展开更多
Effect of electrode insulation on the electric field and the flow field of the machining gap during electrochemical drilling（ECD） is numerically studied. Electric field simulation shows that the current density alon...Effect of electrode insulation on the electric field and the flow field of the machining gap during electrochemical drilling（ECD） is numerically studied. Electric field simulation shows that the current density along the side gap decreases with increasing the thickness of electrode insulation. And the analysis of the electrolyte flow in the frontal gap shows that the insulation thickness has a remarkable influence on the pressure distributions. Ex- periments investigate the influence of the insulation thickness on the main characteristics of the machined hole, i.e. , radial overcut, entrance conicity, and current stability. The poor hole is observed and identified as most likely to occur with a combination of the low tool feed rate and the low insulation thickness. The appropriate thickness of the insulating layer leads to an improvement on hole accuracy and machining stability.展开更多
Two new AlTiN coated cemented carbide drills with Al content of 40% and 55% in weight are developed for high efficiency dry drilling of 40Cr. By studying tool durability, machined hole quality, tool wear mechanism, ch...Two new AlTiN coated cemented carbide drills with Al content of 40% and 55% in weight are developed for high efficiency dry drilling of 40Cr. By studying tool durability, machined hole quality, tool wear mechanism, chip deformation, and lubrication, the dry drilling performance of the two kinds of coated drills is analyzed. Experimental results show that the AlTiN coated drills are suitable for high efficiency dry drilling and can obtain higher quality of machined holes. The tool durability of the drill with 55% Al content is 1. 3 times of that of the drill with 40% Al content at the cutting speed of 90 m/min. The wear mechanism of two AlTiN coatings are studied in experiments. During dry drilling process, oxidative wear appears in both two kinds of drills. The oxide film is formed on the top of the coated drill containing Al content of 55%. And the oxide film helps to increase its high temperature resistance and decrease the coating flaking, thus the drill is failed because of coating subsidence. The drill with less Al content is failed due to peeling and breakage. The lubricated condition in dry drilling is improved by the high Al content coating. It helps to reduce the cutting deformation and benefits to improve the quality of machined holes. The AlTiN coating with higher Al content shows longer tool life and higher quality of machined holes in high efficiency dry drilling. Its tool life increases by 30% compared with that of the coating with less Al content.展开更多
基金Supported by the Projects of National Natural Science Foundation of China(52288101,52174014,52374023)。
文摘The research progress of deep and ultra-deep drilling fluid technology systematically reviewed,the key problems existing are analyzed,and the future development direction is proposed.In view of the high temperature,high pressure and high stress,fracture development,wellbore instability,drilling fluid lost circulation and other problems faced in the process of deep and ultra-deep complex oil and gas drilling,scholars have developed deep and ultra-deep high-temperature and high-salt resistant water-based drilling fluid technology,high-temperature resistant oil-based/synthetic drilling fluid technology,drilling fluid technology for reservoir protection and drilling fluid lost circulation control technology.However,there are still some key problems such as insufficient resistance to high temperature,high pressure and high stress,wellbore instability and serious lost circulation.Therefore,the development direction of deep and ultra-deep drilling fluid technology in the future is proposed:(1)The technology of high-temperature and high-salt resistant water-based drilling fluid should focus on improving high temperature stability,improving rheological properties,strengthening filtration control and improving compatibility with formation.(2)The technology of oil-based/synthetic drilling fluid resistant to high temperature should further study in the aspects of easily degradable environmental protection additives with low toxicity such as high temperature stabilizer,rheological regulator and related supporting technologies.(3)The drilling fluid technology for reservoir protection should be devoted to the development of new high-performance additives and materials,and further improve the real-time monitoring technology by introducing advanced sensor networks and artificial intelligence algorithms.(4)The lost circulation control of drilling fluid should pay more attention to the integration and application of intelligent technology,the research and application of high-performance plugging materials,the exploration of diversified plugging techniques and methods,and the improvement of environmental protection and production safety awareness.
基金Supported by the Project of National Natural Science Foundation of China(52234002,42230814)。
文摘Aiming at the problems of large load of rotation drive system,low efficiency of torque transmission and high cost for operation and maintenance of liner steering drilling system for the horizontal well,a new method of liner differential rotary drilling with double tubular strings in the horizontal well is proposed.The technical principle of this method is revealed,supporting tools such as the differential rotation transducer,composite rotary steering system and the hanger are designed,and technological process is optimized.A tool face control technique of steering drilling assembly is proposed and the calculation model of extension limit of liner differential rotary drilling with double tubular strings in horizontal well is established.These results show that the liner differential rotary drilling with double tubular strings is equipped with measurement while drilling(MWD)and positive displacement motor(PDM),and directional drilling of horizontal well is realized by adjusting rotary speed of drill pipe to control the tool face of PDM.Based on the engineering case of deep coalbed methane horizontal well in the eastern margin of Ordos Basin,the extension limit of horizontal drilling with double tubular strings is calculated.Compared with the conventional liner drilling method,the liner differential rotary drilling with double tubular strings increases the extension limit value of horizontal well significantly.The research findings provide useful reference for the integrated design and control of liner completion and drilling of horizontal wells.
基金support by the financial support of the National Nature Science Foundation of China(No.52274001,No.52074018)China Petrochemical Corporation(No.p21069)The financial support of Fundamental Research Funds for the Central Universities(buctrc202017)。
文摘The study considers gas compression properties,gas slippage,back pressure(BP),phase transition(PT),well depth,and differences in gas-liquid physical properties.A new temperature model for multiphase flow is proposed by considering phase transition in the drilling process.The mathematical model of multiphase flow is solved using the finite difference method with annulus mesh division for grid nodes,and a module for multiphase flow calculation and analysis is developed.Numerical results indicate that the temperature varies along the annulus with the variation of gas influx at the bottom of the well.During the process of controlled pressure drilling,as gas slips along the annulus to the wellhead,its volume continuously expands,leading to an increase in the gas content within the annulus,and consequently,an increase in the pressure drop caused by gas slippage.The temperature increases with the increase in BP and decreases in gas influx rate and wellbore diameter.During gas influx,the thermal conductivity coefficient for the gas-drilling mud two phases is significantly weakened,resulting in a considerable change in temperature along the annulus.In the context of MPD,the method of slightly changing the temperature along the annulus by controlling the back pressure is feasible.
基金supported by the National Key Research and Development Program of China(No.2023YFC2907600)the National Natural Science Foundation of China(Nos.42077267,42277174 and 52074164)+2 种基金the Natural Science Foundation of Shandong Province,China(No.ZR2020JQ23)the Opening Project of State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology(No.KFJJ21-02Z)the Fundamental Research Funds for the Central Universities,China(No.2022JCCXSB03).
文摘The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(RCZ) is built. The formula for an ultimate cutting force is established based on the limit equilibrium principle. The relationship between digital drilling parameters(DDP) and the c-φ parameter(DDP-cφ formula, where c refers to the cohesion and φ refers to the internal friction angle) is derived, and the response of drilling parameters and cutting ratio to the strength parameters is analyzed. The drillingbased measuring method for the c-φ parameter of rock is constructed. The laboratory verification test is then completed, and the difference in results between the drilling test and the compression test is less than 6%. On this basis, in-situ rock drilling tests in a traffic tunnel and a coal mine roadway are carried out, and the strength parameters of the surrounding rock are effectively tested. The average difference ratio of the results is less than 11%, which verifies the effectiveness of the proposed method for obtaining the strength parameters based on digital drilling. This study provides methodological support for field testing of rock strength parameters.
文摘With the growth of deep drilling and the complexity of the well profile,the requirements for a more complete and efficient exploitation of productive formations increase,which increases the risk of various complications.Currently,reagents based on modified natural polymers(which are naturally occurring compounds)and synthetic polymers(SPs)which are polymeric compounds created industrially,are widely used to prevent emerging complications in the drilling process.However,compared to modified natural polymers,SPs form a family of high-molecular-weight compounds that are fully synthesized by undergoing chemical polymerization reactions.SPs provide substantial flexibility in their design.Moreover,their size and chemical composition can be adjusted to provide properties for nearly all the functional objectives of drilling fluids.They can be classified based on chemical ingredients,type of reaction,and their responses to heating.However,some of SPs,due to their structural characteristics,have a high cost,a poor temperature and salt resistance in drilling fluids,and degradation begins when the temperature reaches 130℃.These drawbacks prevent SP use in some medium and deep wells.Thus,this review addresses the historical development,the characteristics,manufacturing methods,classification,and the applications of SPs in drilling fluids.The contributions of SPs as additives to drilling fluids to enhance rheology,filtrate generation,carrying of cuttings,fluid lubricity,and clay/shale stability are explained in detail.The mechanisms,impacts,and advances achieved when SPs are added to drilling fluids are also described.The typical challenges encountered by SPs when deployed in drilling fluids and their advantages and drawbacks are also discussed.Economic issues also impact the applications of SPs in drilling fluids.Consequently,the cost of the most relevant SPs,and the monomers used in their synthesis,are assessed.Environmental impacts of SPs when deployed in drilling fluids,and their manufacturing processes are identified,together with advances in SP-treatment methods aimed at reducing those impacts.Recommendations for required future research addressing SP property and performance gaps are provided.
基金the financial support from the Natural Science Foundation of China(Grant Nos.51904317 and 51821092)Science Foundation of China University of Petroleum,Beijing(Grant No.ZX20180414)other projects(ZLZX2020-0107-01)
文摘With the continuous increase in vertical depths and horizontal displacements of directional wells,the difficulties of drilling operations continue to increase,and more accurate methods of drilling difficulty evaluation are needed.In this paper,a drilling difficulty evaluation method is built by combining drilling limit model and expert evaluation.Firstly,the concept of drilling difficulty index is introduced,and the method to calculate drilling difficulty index is established.Next,the meanings of five drilling difficulty levels are explained and the optimization design method with drilling difficulty as the target is built.At last,the theoretical model is applied to the extended-reach drilling of the Liuhua oilfield in the South China Sea,in which drilling difficulties are evaluated and the relationship between drilling difficulty and development control radius is revealed.The results indicate that extended-reach drilling in the Liuhua oilfield is on the“normal”difficulty level on average,rotary drilling in 8_(1/2)-in.section is the most difficult,and the main constraint conditions are excessive torque and high friction.Through technology upgradation,the drilling difficulties are decreased,the development control radius increases from 6.6 to 11.4 km,and the maximum horizontalto-vertical ratio increases from 5.3 to 8.7.Then,the development wells in marginal oilfields and adjustment wells in old oilfields can be drilled on“normal”difficulty level.Therefore,technology upgradation,especially drilling rig upgradation,is the most important development direction for extended-reach drilling in the South China Sea.
基金supported by the National Natural Science Foundation of China(Grants 52304001,52227804)State Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum,Beijing(No.PRE/open-2310)。
文摘To address the two critical issues of evaluating the necessity of implementing cooling techniques and achieving real-time temperature control of drilling fluids underground in the current drilling fluid cooling technology,we first established a temperature and pressure coupled downhole heat transfer model,which can be used in both water-based and oil-based drilling fluid.Then,fourteen factors,which could affect wellbore temperature,were analyzed.Based on the standard deviation of the downhole temperature corresponding to each influencing factor,the influence of each factor was quantified.The influencing factors that can be used to guide the drilling fluid's cooling technology were drilling fluid thermal conductivity,drilling fluid heat capacity,drilling fluid density,drill strings rotation speed,pump rate,viscosity,ROP,and injection temperature.The nondominated sorting genetic algorithm was used to optimize these six parameters,but the optimization process took 182 min.Combining these eight parameters'influence rules with the nondominated sorting genetic algorithm can reduce the optimization time to 108 s.Theoretically,the downhole temperature has been demonstrated to increase with the inlet temperature increasing linearly under quasi-steady states.Combining this law and PID,the downhole temperature can be controlled,which can reduce the energy for cooling the surface drilling fluid and can ensure the downhole temperature reaches the set value as soon as possible.
基金financially supported by the National Natural Science Foundation of China(Grant No.52150410427)the Key Support Program for Foreign Experts of the Ministry of Science and Technology of the People's Republic of China(No.wgxz2022057)funding for post-doctoral work by the Department of Human Resources and Social Security of Hubei Province。
文摘Thermo-responsive nanocomposites have recently emerged as potential nanoplugging agents for shale stabilization in high-temperature water-based drilling fluids(WBDFs). However, their inhibitory properties have not been very effective in high-temperature drilling operations. Thermo-responsive Janus nanocomposites are expected to strongly interact with clay particles from the inward hemisphere of nanomaterials, which drive the establishment of a tighter hydrophobic membrane over the shale surface at the outward hemisphere under geothermal conditions for shale stabilization. This work combines the synergistic benefits of thermo-responsive and zwitterionic nanomaterials to synchronously enhance the chemical inhibitions and plugging performances in shale under harsh conditions. A novel thermoresponsive Janus nanosilica(TRJS) exhibiting zwitterionic character was synthesized, characterized,and assessed as shale stabilizer for WBDFs at high temperatures. Compared to pristine nanosilica(Si NP)and symmetrical thermo-responsive nanosilica(TRS), TRJS exhibited anti-polyelectrolyte behaviour, in which electrolyte ions screened the electrostatic attraction between the charged particles, potentially stabilizing nanomaterial in hostile shaly environments(i.e., up to saturated brine or API brine). Macroscopically, TRJS exhibited higher chemical inhibition than Si NP and TRS in brine, prompting a better capability to control pressure penetration. TRJS adsorbed onto the clay surface via chemisorption and hydrogen bonding, and the interactions became substantial in brine, according to the results of electrophoretic mobility, surface wettability, and X-ray diffraction. Thus, contributing to the firm trapping of TRJS into the nanopore structure of the shale, triggering the formation of a tight hydrophobic membrane over the shale surface from the outward hemisphere. The addition of TRJS into WBDF had no deleterious effect on fluid properties after hot-treatment at 190℃, implying that TRJS could find potential use as a shale stabilizer in WBDFs in hostile environments.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51991361)the foundation of China University of Petroleum(Beijing)(Grant No.2462021YXZZ002).
文摘With increasing drilling depth and large dosage of weighting materials,drilling fluids with high solid content are characterized by poor stability,high viscosity,large water loss,and thick mud cake,easier leading to reservoir damage and wellbore instability.In this paper,micronized barite(MB)was modified(mMB)by grafting with hydrophilic polymer onto the surface through the free radical polymerization to displace conventional API barite partly.The suspension stability of water-based drilling fluids(WBDFs)weighted with API barite:mMB=2:1 in 600 g was significantly enhanced compared with that with API barite/WBDFs,exhibiting the static sag factor within 0.54 and the whole stability index of 2.The viscosity and yield point reached the minimum,with a reduction of more than 40%compared with API barite only at the same density.Through multi-stage filling and dense accumulation of weighting materials and clays,filtration loss was decreased,mud cake quality was improved,and simultaneously it had great reservoir protection performance,and the permeability recovery rate reached 87%.In addition,it also effectively improved the lubricity of WBDFs.The sticking coefficient of mud cake was reduced by 53.4%,and the friction coefficient was 0.2603.Therefore,mMB can serve as a versatile additive to control the density,rheology,filtration,and stability of WBDFs weighted with API barite,thus regulating comprehensive performance and achieving reservoir protection capacity.This work opened up a new path for the productive drilling of extremely deep and intricate wells by providing an efficient method for managing the performance of high-density WBDFs.
基金the financial support from the Natural Science Foundation of China(Grant Nos.52222401,52234002,52394250,52394255)Science Foundation of China University of Petroleum,Beijing(Grant No.ZXZX20230083)other projects(ZLZX2020-01-07-01)。
文摘In extended-reach or long-horizontal drilling,cuttings usually deposit at the bottom of the annulus.Once cuttings accumulate to a certain thickness,complex problems such as excessive torque and drag,tubing buckling,and pipe stuck probably occur,which results in a lot of non-productive time and remedial operations.Cuttings bed remover can efficiently destroy deposited cuttings in time through hydraulic and mechanical stirring effects.This paper aims to build a method for hole cleaning evaluation and installation spacing optimization of cuttings bed remover to improve the wellbore cleaning effect.Firstly,a Computational Fluid Dynamics approach with Eulerian—Eulerian multiphase model was utilized to investigate the mechanism of cuttings transportation,and a new type of cuttings bed remover was designed.Next,an evaluation method of hole cleaning effect of remover was established.After that,the effects of several drilling parameters on hole cleaning including flow rate of drilling fluid,rotational speed of drillpipe,rate of penetration,wellbore size,rheological property of drilling fluid,and remover eccentricity on the performance of cuttings bed remover were investigated.The results demonstrate that the new type of remover with streamline blade performs better than conventional removers.The efficiency of hole cleaning is greatly improved by increasing the rotational speed of drillpipe,flow rate of drilling fluid,remover eccentricity,and 6 rpm Fann dial reading for drilling fluid.While higher rate of penetration and large wellbore size result in worse hole cleaning.These findings can serve as an important guide for the structure optimization design of cuttings bed remover and installation spacing of removers.
基金the support of the National Natural Science Foundation of China(Nos.42207211,42202320 and 42172296)Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Tongji University(No.KLE-TJGE-G2304).
文摘Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point.This paper develops a drilling process detection(DPD)system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod,geophones at the tunnel face,a laser rangefinder,and an onsite computer.A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling.A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method.Time-frequency analysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seismic exploration wavelet.A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained.Both the borehole core and optical image validate the inverted P-wave velocity field.A numerical simulation of a checkerboard benchmark model is used to test the tomography method.The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.
基金supported by the National Natural Science Foundation of China (Grant No.51991361 and Grant No.51874329)。
文摘The environmental hazards and"carbon footprint"of oil and gas drilling can be significantly reduced by replacing traditional petroleum-based chemical additives with natural materials derived from plants and animals.This paper explored for the first time the interaction mechanism between natural rubber latex(NRL)and bentonite suspensions(BTs)through a series of characterization experiments,as well as the potential applications in water-based drilling fluids(WBDF).The gel viscoelasticity experiments showed that NRL could decrease the consistency coefficient(k)and flow index(n)of BTs,and enhance the shear thinning performance of BTs as pseudo-plastic fluids.In addition,0.5 w/v%NRL not only increased the critical yield stress and strengthened the structural strength between the bentonite particles,but also facilitated the compatibility of pressure loss and flow efficiency.The evaluation of colloidal stability and WBDF performance indicated that NRL particles could promote the hydration and charge stability on the surface of BTs particles,and optimize the particle size distribution and flow resistance of WBDF under the"intercalation-exfoliation-encapsulation"synergistic interaction.Moreover,NRL can improve the rheological properties of WBDF at high temperatures(<150.C),and form a dense blocking layer by bridging and sealing the pores and cracks of the filter cake,which ultimately reduces the permeability of the cake and the filtration loss of WBDF.
基金supported by National Natural Science Foundation of China (Nos. 51827901, 52104096)the Shenzhen National Science Fund for Distinguished Young Scholars (No. RCJC20210706091948015)+2 种基金Open Fund of State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (No. SKHL2216)National Key R & D Program of China (No. 2022YFB3706605)Youth Foundation of Sichuan Natural Science Foundation (No. 2023NSFSC0780)。
文摘Using pressure-preserved coring technique to determine in-situ gas content provides a more precise assessment of gas resource reserves and safeguard of mining safety in coal seams. How coring technique and depth affect the determination of gas content is unclear due to borehole zoning rupture caused by roadway excavation and drilling disturbance. To this end, a proposed coupling model of stress distribution and gas migration was simulated and validated by FLAC^(3D) and COMSOL Multiphysics considering superposition effects of roadway excavation and drilling disturbance. The findings indicate that the roadway surrounding rock displays distinct zoning features including stress relief zone, stress concentration zone that is composed of plastic zone, elastic zone, and original stress zone;and the broken situations depending on the borehole peeping are consistent with the corresponding simulation results.On this basis, this study proposes a set of drilling coring depth calculation and prediction model for the gas desorption affected area under engineering disturbance. Optimal depth of coring drilling is not only approach to the in-situ coal bulk, but also can get the balance of the drilling workload and cost controlling. According to the typical mine site geological conditions and the numerical simulation results in this study, if the roadway excavation time is ~1 year, it is recommended that the pressure-preserved coring depth should be greater than 17 m.
基金Supported by the Key Fund Project of the National Natural Science Foundation of China and Joint Fund of Petrochemical Industry(Class A)(U1762212)National Natural Science Foundation of China(52274009)"14th Five-Year"Forward-looking and Fundamental Major Science and Technology Project of CNPC(2021DJ4402)。
文摘For the analysis of the formation damage caused by the compound function of drilling fluid and fracturing fluid,the prediction method for dynamic invasion depth of drilling fluid is developed considering the fracture extension due to shale minerals erosion by oil-based drilling fluid.With the evaluation for the damage of natural and hydraulic fractures caused by mechanical properties weakening of shale fracture surface,fracture closure and rock powder blocking,the formation damage pattern is proposed with consideration of the compound effect of drilling fluid and fracturing fluid.The formation damage mechanism during drilling and completion process in shale reservoir is revealed,and the protection measures are raised.The drilling fluid can deeply invade into the shale formation through natural and induced fractures,erode shale minerals and weaken the mechanical properties of shale during the drilling process.In the process of hydraulic fracturing,the compound effect of drilling fluid and fracturing fluid further weakens the mechanical properties of shale,results in fracture closure and rock powder shedding,and thus induces stress-sensitive damage and solid blocking damage of natural/hydraulic fractures.The damage can yield significant conductivity decrease of fractures,and restrict the high and stable production of shale oil and gas wells.The measures of anti-collapse and anti-blocking to accelerate the drilling of reservoir section,forming chemical membrane to prevent the weakening of the mechanical properties of shale fracture surface,strengthening the plugging of shale fracture and reducing the invasion range of drilling fluid,optimizing fracturing fluid system to protect fracture conductivity are put forward for reservoir protection.
基金Supported by the National High Technology Research and Development Program of China (863 Program) under Grant No.2006AA09A104
文摘The general layout of 6th generation semi-submersible drilling platforms is the main factor impacting the efficiency of their drilling operations. This paper provides a compound/integrated algorithm based on process flow that is aimed at improving efficiency, while giving attention to stability and safety at the same time. The paper describes the process flow of dual drilling centers and a hierarchical division of rigs based on the different modes of transportation of various drilling support systems. The general layout-centripetal overall arrangement spatially was determined based on drilling efficiency. We derived our modules according to drilling functionality; the modules became our basic layout units. We applied different layout algorithm to mark out the upper and lower decks. That is, the upper deck was designed based on the lowest transportation cost while the lower deck＇s calculations were based on the best-fit scope. Storage configurations in columns and pontoons were also considered for the layout design. Finally the center of gravity was taken into consideration and the general layout was adjusted accordingly, to result in an optimal center of gravity. The methodology of the general layout can provide a reference for implementation of domestic designs of semi-submersible rigs.
基金financially supported by the National Natural Science Foundation of China through Grants No. 51221003, No. 51134004 and No. 51274220
文摘Theories established from engineering fundamentals have been of great value in supporting the design and execution of drilling operations in gas drilling where gas is used as a drilling fluid.This work presents an overview of new theories developed in recent years for special gas drilling operations including horizontal wells.These new theories are found in the areas of gas-mixture flow hydraulics in deviated and horizontal boreholes,hole cleaning of solids accumulation,hole cleaning of formation water,flow diverging for washout control,bit orifice optimization,and depression of formation water influx.This paper provides drilling engineers with updated mathematical models and methods for optimizing design to improve gas drilling performance.
基金Supported by the National Natural Science Foundation of China(52288101).
文摘Three high-temperature resistant polymeric additives for water-based drilling fluids are designed and developed:weakly cross-linked zwitterionic polymer fluid loss reducer(WCZ),flexible polymer microsphere nano-plugging agent(FPM)and comb-structure polymeric lubricant(CSP).A high-temperature resistant and high-density polymeric saturated brine-based drilling fluid was developed for deep drilling.The WCZ has a good anti-polyelectrolyte effect and exhibits the API fluid loss less than 8 mL after aging in saturated salt environment at 200°C.The FPM can reduce the fluid loss by improving the quality of the mud cake and has a good plugging effect on nano-scale pores/fractures.The CSP,with a weight average molecular weight of 4804,has multiple polar adsorption sites and exhibits excellent lubricating performance under high temperature and high salt conditions.The developed drilling fluid system with a density of 2.0 g/cm^(3)has good rheological properties.It shows a fluid loss less than 15 mL at 200°C and high pressure,a sedimentation factor(SF)smaller than 0.52 after standing at high temperature for 5 d,and a rolling recovery of hydratable drill cuttings similar to oil-based drilling fluid.Besides,it has good plugging and lubricating performance.
基金Supported by the 111 Projects Foundation from State Administration of Foreign Experts Affairs of China and Ministry of Education of China under Grant No.B07019
文摘In recent years, numerous exploration activities of oil and gas industry have been conducted in ultra deep water. The global offshore industry is building systems today for drilling in even deeper water, progressively using new technologies, and significantly extending existing technologies. This is the general trend in the offshore oil and gas industry. So the technology of ultra-deepwater risers, which is the main tool in drilling oil, is more and more standard. This paper manly focuses on the global analysis of the drilling risers. And it is divided into two parts, operability analysis and hang-off analysis that are used to check the design of the riser. In this paper, the rotation angle and stress of the riser in the drilling mode are calculated to determine the operability envelop. The number of the buoyancy modules has been determined and according to the API standard, all the worked out values have been checked out. From all the above, it is concluded that the operability envelop is relatively small under harsh condition and the number of the buoyancy modules is a little large. And above all, the design of this riser is successful.
基金Supported by the National Natural Science Foundation of China(50635040)the National High Technology Research and Development Program of China("863"Program)(2006AA04Z321)the Natural Science Foundation of Jiangsu Province(BK2008043)~~
文摘Effect of electrode insulation on the electric field and the flow field of the machining gap during electrochemical drilling（ECD） is numerically studied. Electric field simulation shows that the current density along the side gap decreases with increasing the thickness of electrode insulation. And the analysis of the electrolyte flow in the frontal gap shows that the insulation thickness has a remarkable influence on the pressure distributions. Ex- periments investigate the influence of the insulation thickness on the main characteristics of the machined hole, i.e. , radial overcut, entrance conicity, and current stability. The poor hole is observed and identified as most likely to occur with a combination of the low tool feed rate and the low insulation thickness. The appropriate thickness of the insulating layer leads to an improvement on hole accuracy and machining stability.
文摘Two new AlTiN coated cemented carbide drills with Al content of 40% and 55% in weight are developed for high efficiency dry drilling of 40Cr. By studying tool durability, machined hole quality, tool wear mechanism, chip deformation, and lubrication, the dry drilling performance of the two kinds of coated drills is analyzed. Experimental results show that the AlTiN coated drills are suitable for high efficiency dry drilling and can obtain higher quality of machined holes. The tool durability of the drill with 55% Al content is 1. 3 times of that of the drill with 40% Al content at the cutting speed of 90 m/min. The wear mechanism of two AlTiN coatings are studied in experiments. During dry drilling process, oxidative wear appears in both two kinds of drills. The oxide film is formed on the top of the coated drill containing Al content of 55%. And the oxide film helps to increase its high temperature resistance and decrease the coating flaking, thus the drill is failed because of coating subsidence. The drill with less Al content is failed due to peeling and breakage. The lubricated condition in dry drilling is improved by the high Al content coating. It helps to reduce the cutting deformation and benefits to improve the quality of machined holes. The AlTiN coating with higher Al content shows longer tool life and higher quality of machined holes in high efficiency dry drilling. Its tool life increases by 30% compared with that of the coating with less Al content.
