Research on Fe-based impregnated diamond drill bits strengthened by Nano-NbC and Nano-WC

In order to improve the matrix performance of impregnated diamond drill bit to better meet the drilling needs,the effects of the addition of nano-WC and nano-NbC particles on the matrix material together with the mechanical properties and microstructure of the diamond-matrix composite material of the Fe-based diamond drill bit were studied by using the method of uniform formula design,regression analysis and solution finding.An indoor drilling test was also carried out using the fabricated impregnated diamond drill bit.The results showed that after the addition of nano-NbC and nano-WC,the hardness and flexural strength of the matrix material got improved,as the flexural strength of the diamond composite material increased to 4.29%,the wear-resistance ratio increased to 8.75%,and the tighter the chemical bonding between the diamond and the matrix.This,indicates that the addition of nanoparticles has a positive significance in improving the performance of the diamond composite.The results of the drilling test showed that the mechanical drilling speed of the impregnated diamond drill bit after nanoparticle strengthening is 25.85%higher than that of the conventional drill bit,and the matrix wear was increased by 17.5%.It proves that nanoparticles can improve the drilling performance and efficiency of drill bit.

Tooth arrangement design of retractable DTH hammer bit used for drilling while casing

Down-the-hole(DTH)hammer with casing while drilling(CWD)is a technology that has been proven to be able to alleviate many of the problems faced by complex formations.However,the drill bit is suffered from rapid wear,low drilling efficiency,and high energy consumption due to the unreasonable tooth arrangement and impact energy selection in drilling process,which affect the application effect of this technology.ABAQUS software was used for numerical simulation of rock breaking behavior under impact load with the single,three,and five teeth arrangement drill bit respectively,to improve the application effect and solve the aforementioned technical problems.Based on the calculated parameters of tooth arrangement,we designed a novel drill bit for hard rocks and provided a theoretical basis for the tooth arrangement of largediameter drill bits.

Reliability analysis of retractable drill bit with air reverse circulation used for drilling while casing

Casing-while-drilling(CWD)with down the hole(DTH)hammer drilling technology has been widely used in unconsolidated formations,due to its advantages in protecting the borehole wall,excellent rock cuttings capacity,and fast penetration rate in hard rock.As an important component of the CWD system,the structure of the retractable drill bit needs not only to ensure to form stronger reverse circulation,but also to be expandable or retractable as needed,otherwise the drill bit cannot be lift and put down smoothly in the casing,and may lead to drilling accidents.This paper developed a new type of reverse circulation DTH hammer drill bit used for CWD drilling technology.The retractable performance of this type of drill bit is studied using ADAMS software.The results show that it is smoothly expandable and retractable as designed under the conditions of the weight of the bit(WOB)of 0.5–2.0 t and the rotation speed of 30–60 r/min.To investigate the reverse circulation effect of the drill bit,Fluent software was used to simulate the flow characteristic inside it.The simulation results indicated that it can form strong reverse circulation,and the entrainment ratio h can reach 9.5%.

A new method of combined rock drilling

Based on the technologies of traditionally mechanical drilling and water jet,we propose a new method of abrasive water jet in combination with rock drilling,and establish a combined rock drilling system for the gas pre-drainage.This study chose the common sandstone and silicon limestone as the rock sample.A series of experiments were completed in the case of dry drilling,existing technology drilling,combined drilling with high pressure water jet and combined drilling with abrasive water jet,respectively.The drilling efficiency and performance were contrasted and analyzed in detail.The results indicate that it is better to choose the method of combined drilling with the high-pressure water jet for soft rocks.The method of combined drilling with abrasive water jet is feasible for the hard rock drilling and has higher drilling efficiency and performance.In this paper,compared with the existing technology,the drilling depth has increased by about 65%,the axial force and torque have reduced by about 14%and 17%,respectively,and the drill wear reduces obviously in the same conditions.

Similarity evaluation of stratum anti-drilling ability and a new method of drill bit selection

Considering the stratum anti-drilling ability,drill bit working conditions,drill bit application effect and drill bit economic benefits,the similarity of stratum anti-drilling ability was evaluated by grey relational analysis theory to screen out candidate drill bits with reference values.A new comprehensive performance evaluation model of drill bit was established by constructing the absolute ideal solution,changing the relative distance measurement method,and introducing entropy weight to work out the closeness between the candidate drill bits and ideal drill bits and select the reasonable drill bit.Through the construction of absolute ideal solution,improvement of relative distance measurement method and introduction of entropy weight,the inherent defects of TOPSIS decision analysis method,such as non-absolute order,reverse order and unreasonable weight setting,can be overcome.Simple in calculation and easy to understand,the new bit selection method has good adaptability to drill bit selection using dynamic change drill bit database.Field application has proved that the drill bits selected by the new drill bit selection method had significant increase in average rate of penetration,low wear rate,and good compatibility with the drilled formations in actual drilling.This new method of drill bit selection can be used as a technical means to select drill bits with high efficiency,long life and good economics in oilfields.

Research on slim-hole drilling technology for shale gas geological survey in China

Over the last 10 years,the China Geological Survey has deployed 137 slim-hole shale gas geological exploration wells for coring entire wellbores.These wells are primarily located in new blocks and geological formations where neighboring well data are insufficient,beyond the scope of developed oil fields in China,or outside of oil and gas company mining-right areas.The drilling rig equipment,coring tools,and core drill bits of slim-hole shale gas drilling technology are different from those associated with traditional petroleum drilling.Many studies have been conducted on non-coring slim-hole drilling technology.This paper focuses on coring technology and drilling safety,summarizing a set of high-efficiency shale gas drilling equipment and technology systems based on geological drilling equipment and techniques(that can be used for solid mineral exploration).We report on:1)an improved vertical shaft drilling rig adapted to shale gas well control safety;2)high-efficiency core drilling techniques,focusing on coring tools,and techniques incorporating an inverted tower drilling tool combination,air circulation follow-through technology,and expanded casing technology;3)research progress on high-efficiency core drill bits,including non-planar tooth polycrystalline diamond compact bits and impregnated diamond core bits,along with their application effects.This research provides substantial advances in drill-core technology and improvements in exploration efficiency.Moreover,it provides a reference frame for well structural design and selection of construction technology for shale gas exploration drilling projects.

Core discing characteristics and mitigation approach by a novel developed drill bit in deep rocks

Core discing often occurs in deep rocks under high-stress conditions and has been identified as an important characteristic for deep rock engineering.This paper presents the formation mechanism of core discing firstly.Then,the interaction between diamond drill bits and rock was analyzed based on numerical modeling.A novel drill bit with an inner conical crown for the mitigation of core discing was designed and verified by simulation experiments.The mitigation method was applied in the cavern B1 of CJPL-Ⅱand satisfactory results had been achieved.The percentage of core discing had been obviously decreased from 67.8%when drilling with a rectangular crown drill bit,to 26.5%when an inner conical crown drill bit had been adopted.This paper gives full insight into core discing characteristics and provides a new method for core discing mitigation;it will potentially contribute to stress measurement in deep rock engineering.

Design and comparative analysis of self-propelling drill bit applied to deep-sea stratum drilling robot

Robotic subsea stratum drilling robot is a method for new subsea stratigraphic geological investigation and resource exploration.Resistance at the front end is the main source of resistance to the robot’s motion in the strata.Since there is no continuous and strong downward drilling force as in conventional drilling rigs,robot movement relies heavily on the drill bit to reduce the drilling resistance.In this study we propose a self-propelling drill bit that can discharge soil debris to provide propulsive force and reduce the resistance.The key parameter of the drill bit design,the spiral blade lead angle,was determined by theoretical analysis of the drill bit’s soil discharging effect.To verify the structural advantages of the self-propelling drill bit in reducing resistance,a comparative analysis with a conventional conical drill bit was conducted.The drilling process of both bits was simulated using finite element simulation at various rotation speeds,the penetration force and torque data of both drill bits were obtained,and tests prepared accordingly in subsea soil were conducted.The simulations and tests verified that the penetration force of the self-propelling drill bit was lower than that of the conventional conical drill bit.The self-propelling drill bit can reduce the resistance effectively,and may play an important role in the stratum movement of drilling robots.

Anti-drilling ability of Ziliujing conglomerate formation in Western Sichuan Basin of China

The conglomerate rock is usually featured by strong heterogeneity,high abrasiveness,and poor drillability due to its complex composition and texture,which brought a huge challenge for drilling efficiency.In order to guide the drill bit selection and high-efficiency drilling,the physical,mechanical,and drillability characteristics were investigated for conglomerate rock that collected from the lower Jurassic Ziliujing formation in the Western Sichuan Basin of China.The mineral composition,SEM micro-structure,P-and S-wave velocities,uniaxial and triaxial compressive testing,drillability,abrasiveness were systematically tested and analyzed.The mechanical properties and anti-drilling ability of Ziliujing formation were proposed for a typical deep well of S-07,and the distribution characteristics were analyzed.The results indicated that the Ziliujing rock is rich-in quartz and clay minerals,due to the co-existing of strong quartz gravel and weak argillaceous cement,the Ziliujing rock shows strong heterogeneity.The relationships are roughly linear among UCS,drillability,and grinding weight loss with P-wave velocity.The Young's modulus,UCS,internal friction angle,drillability,and abrasiveness meet the Weibull distribution pattern,while only the Poisson's ratio meets the Kernel Smooth distribution pattern.Logging interpretation results reval that the Ziliujing formation has the Young's modulus of 38.61±17.08 GPa,the Poisson's ratio of 0.327±0.006,the internal friction angle of 49.21±11.00°,the drillability of 8.04±1.54,and the abrasiveness grade of 4.32±1.94.The mechanical properties and anti-drilling ability of logging interpretation are in good agreement with the experimental data.The Ziliujing formation is a kind of hard rock with strong heterogeneity,high strength,poor drillability,and medium abrasiveness.Based on the characteristics of Ziliujing formations,the SV516TAUL PDC bit with non-planar cutters was selected for the field application due to the good abrasion resistance,impact resistance,self-sharpening and thermal stability of the non-planar cutters.The field application shows that the average ROP of the new type drill bit in Ziliujing formation is 2.93 m/h,and the average footage is 225.9 m.Comparing with the traditional PDC bit,the ROP of the new drill bit with non-planar cutters has increased by 67.4%,and the footage has increased by 92.1%.The results of this paper can be utilized to guide the drill bit selection and high-efficiency drilling in conglomerate formation.

Study of the influences of rotary table speed on stick-slip vibration of the drilling system

Stick-slip vibration presents one of the major causes of drilling problems,such as premature tool failures,low drilling efficiency and poor wellbore quality.The objective of this work is to investigate the influences of rotary table speed(RTS)on stick-slip phenomenon of the drilling system.In this study,the drilling system is treated as a lumped torsional pendulum model of which the bit/rock interaction is regarded as Coulomb friction.By analyzing cases with different RTS,two types of vibrations on the bit are found:stick-slip vibration and uniform motion.With an increase in the RTS,the stick-slip vibration on the drill bit disappears once the RTS arrives at its critical value.For the cases that stick-slip vibrations occur,the phase trajectories converge toward a limit cycle.For the cases that stick-slip vibration does not appear,the drill bit tends to stabilize at a uniform motion and the phase trajectories correspond to contracting spirals observed in the phase plane.

Spherical contact mechanical analysis of roller cone drill bits journal bearing

Fang contact model is introduced to analyze stress of the spherical fixed ring journal bearing.Developed calculation programs in the MATLAB software which are utilized to calculate the contact characteristics of roller cone drill bits spherical fixed ring journal bearing.In addition,effects of external load,radius clearance values,and material parameter on the mechanics performance were investigated.The results show that the value of external load has a direct pronounced effect on the contact characteristics of journal bearing.There is a significant positive correlation between contact pressure and external load,radius clearance value,and the Young's modulus of material.However,there is an evident negative correlation between contact radius of journal bearing and radius clearance value,and the Young's modulus of material.The smaller radius clearance value of journal bearing is,the more centralized contact region will be,so the corresponding contact pressure will be higher.From the perspective of reducing friction and wear,we need select the materials which have high strength and good toughness.Not only might this can improve the wear resistance,it also effectively decreases the contact pressure.In this case,we can prolong the service life of roller cone drill bits journal bearing.

Preliminary Design of Pressure Torque Separation Sensor for Drilling Bit

The working state of drilling bit is a critical issue in the drilling process. The preliminary design of pressure and torque separation sensor for drilling bit is expatiated herein. The sensor unit is composed of the elastic unit and the Wheatstone full bridge. Under composited load, the theoretical analysis about separating the axial force and torque of drilling bit is discussed firstly. The separation has been achieved by using the Wheatstone full bridge pasted onto the elastic unit. Then the transversal and axial strains distribution of elastic unit has been calculated and analyzed by ANSYS software, when the bit is under axial force and torque. Based on the calculation and analysis results, the sensitivity and accuracy of the sensor's whole measurement chain can be reckoned. Meanwhile, the calculation and analysis results can also give good suggestion about the positions where the strains gauge should be pasted. Finally, it has been proved that this solution can meet the preset requirements very well.

Research on ultrasonic-assisted drilling in micro-hole machining of the DD6 superalloy

The DD6 nickel-based superalloy exhibits remarkably high temperature properties;therefore,it is employed as a crucial structural material in the aviation industry.Nevertheless,this material is difficult to process.Ultrasonic-assisted drilling(UAD)combines the characteristics of vibration processing technology and conventional drilling technology,significantly improving the machinability of difficult-to-machine materials.Thus,UAD experiments were performed on micro-hole machining of DD6 superalloy in this study.The effects of amplitude,frequency,spindle speed,and feed rate on thrust force,machining quality,and drill bit wear were studied;thereafter,a comparison was drawn between these effects and those of conventional drilling(CD).The experimental results reveal that the thrust force decreases with an increase in spindle speed or a decrease in feed rate for both UAD and CD.UAD can significantly reduce the thrust force.With the same processing parameters,the greater the amplitude,the greater the reduction of the thrust force.The surface roughness of the hole wall produced by UAD is lower than that of CD.Compared with CD,UAD reduces the burr height,improves machining accuracy,and reduces drill bit wear.

Bionic surface design of cemented carbide drill bit

The development of a high-performance cemented carbide drill bit is of great significance to the reduction of rock drilling-cost. The non-smooth features of a biological surface provide an insight into how they can obtain low friction and good wear resistance with evolving surface morphology. By analyzing the mechanism of the surface of a dung beetle for reducing soil wear and adherence, we design a cemented carbide drill bit with a bionic surface, which is expected to have superior anti-wearing and anti-sticking properties for drilling the soft coal seam. Inspired from the characteristics of the head and pronotum surface of the dung beetle, optimized non-smooth surface of the drill bit was constructed. The working performance of this innovative drill was experimentally tested. With comparative experiments under the identical drilling conditions, the wear rates, drilling times of conventional drills and bionic drills were measured. Compared with the conventional counterpart, the drill designed exhibits better performance in reducing wear and sticking drilling-breaks, therefore achieving higher levels of efficiency. The diameter of the dome and pit on the bit surface is in the range of 0.8–1.2 mm, and the bionic drill bits could get better performance with preferable drilling speeds and wear rates.

On the formation of limit cycle of the friction-induced stick-slip vibration in oilwell drillstring

In this paper,the stick-slip vibration in oilwell drillstring is studied.The drilling system is modelled as a lumped-parameter torsional pendulum and the interaction between the drill bit and the rock is treated as Coulomb friction.Equation of motion of the drill bit is established and the dynamic responses of the drill bit are obtained.A drilling system with the drillstring length 3000 m is analysed,in which the system parameters are selected by reference to the actual drilling situation.After the slip vibrations in the initial stage,final state of the drill bit is a stable stick-slip vibration of which the limit cycle is a closed loop.In order to find the stability of the limit cycle corresponds to the periodically stick-slip vibration,different initial conditions for the drill bit are studied.Results show that the drill bit will lead to a periodic motion and the phase trajectories ultimately converge to the same limit cycle corresponds to stable stick-slip vibration.

Using Raman shift and FT-IR spectra as quality indices of oil bit PDC cutters

Nowadays many of oil and gas wells are drilled extensively by Polycrystalline Diamond Compact(PDC)drill bits.Various companies are manufacturing PDC cutters according to their usage.All of these companies concentrate their products of PDC cutters to be well resisting for abrasive wear.The wear of PDC inserts leads to money loss as well as delays the drilling procedures causing unexpected dilemmas.Therefore,it is crucially significant to evaluate the quality of the PDC cutters based on their resistance against abrasive wear.The present work concentrates on assessing the PDC cutters from various sources using two non-destructive analytical approaches:Raman-Shift and Fourier Transformation Infrared Ray(FT-IR)spectra.The analysis of the PDC samples with the analytical techniques were validated with the previous experimental results obtained from micro and nano-scratch tests achieved on the same specimens.The presented work could be performed on many PDC cutters from various manufacturers as the applied tests considered non-destructive compared to the traditional destructive techniques which leads the way for evaluating lots of PDC cutters without causing any damage.The analysis of the applied analytical approaches agreed with the results obtained from previous experimental scratch tests.