【作者】 王红波；

【导师】 段隆臣；

【作者基本信息】 中国地质大学 ， 钻井工程， 2010， 博士

【摘要】 我国是一个人口众多、资源相对不足的发展中国家,资源短缺已经成为制约我国经济发展的主要瓶颈。为了贯彻“国务院关于加强地质工作的决定”,必须大量开展深部硬岩钻探。深孔硬岩钻进大约有70%的时间花费在钻进和起下钻过程中,钻头一旦出现质量事故,都会在钻进过程中造成严重的损失。深孔勘探钻头造价一般比较昂贵,钻头损坏本身就造成了很大的经济损失,而起下钻更是浪费大量的人力物力,查明事故原因要大费周折,更换合适的替代钻头需要时间,这些因素耽误工期,使生产计划延期完成。由此可知,钻头质量好坏在钻孔施工中非常重要,要想使钻头达到钻速快、钻进效率高等目的,就必须研制高效、长寿命的钻头。我国在硬岩钻探中主要采用孕镶金刚石钻头,该技术已经比较成熟,没有多少提高的余地,而在钻软～中硬岩层时,PDC (Polycrystalline Diamond Compact)钻头的钻探效率高出传统金刚石钻头的数倍,但目前研究出的PDC取心钻头不适合于钻硬岩层及坚硬岩层,在钻进这些岩层时,钻头容易崩齿、磨损快、钻速慢,从钻进效率与经济因素来看,都不划算。要想PDC取心钻头在钻进硬岩上取得象钻软～中硬岩层那样的效果,有待于我们进行进一步开发。本课题的目的就是以适合于硬岩钻进为目标,进行胎体PDC取心钻头的研究,希望通过进一步的研究,使PDC取心钻头在硬岩层的钻进能力增强,取得较好的钻进效果。论文以钻进硬岩为目的,在前人研究PDC钻头的基础上,运用实验室设备、Pro/engineering及AutoCAD绘图软件、Ansys软件,研究了硬岩的物理力学性质、仿真分析了钻头结构对破岩能力的影响、围绕硬岩对钻头材料的要求进行了研究,并进行了钻头的制造工艺流程及微钻试验,最后设计了野外钻头并对其工作状态及受力进行了探讨。第一章综述了国内外对于PDC钻头的研究现状及趋势,包括岩石的可钻性、钻头的设计、钻头的制造及钻头的工作状态四方面。第二章是关于岩石可钻性的研究。岩石的可钻性是其钻进过程中岩石抵抗破碎的能力,它表示岩石破碎的难易程度。研究可钻性的目的是运用岩石的可钻性进行判断是否是硬岩,从而为设计钻头提供硬岩的物理力学参数和岩样。选取了8种较硬的岩石进行试验,为了了解岩样的物理组成成分、结构构造,并对岩石予以正确的定名,选用岩石薄片分析来进行。同时,通过岩石组成矿物各自的莫氏硬度计算岩石的集合莫氏硬度,再以此为依据对岩石软硬程度进行初步了解。选择压入硬度为主要指标,联合岩石摆球硬度和塑性系数,结合1984年地质部颁发的PDC岩石可钻性分级表来对岩石进行可钻性分级,确定岩石可钻性级别。然后,按岩石可钻性级别来确定岩石的软硬程度,并用综合性力学指标来对这些岩石进行鉴别。运用岩石单轴抗压强度对综合指标分级进行验证,从岩石抗压强度和综合指标对岩性分析的对比第四章是关于微钻试验的研究。微钻试验是为了达到三方面的目的,即熟悉钻头制造工艺流程,研究PDC的排列,并根据微钻过程中钻头的状况来进一步认识硬岩钻进对钻头的要求。共设计三个小钻头,每个钻头用6片PDC,每片PDC的后倾角15.1。,旁通角7.5°,出露高度为4mm保持不变,只改变唇面厚度及PDC在钻头唇面上的排列方式,分别采用单环式与双环式布置方式。钻头制造材料的准备首先包括模具的设计与制造,必须考虑到两方面问题：一是石墨模具是否能够承受住钻头烧结成型时施加的烧结压力,即在所需要的烧结压力范围内,石墨模具不致于由于抗压强度不够而被压碎；二是大直径石墨模具烧结钻头的过程中,温度能否上升至钻头配方所要求的烧结温度。钻头体作为切削具的支撑体,将轴向力和扭矩传递给每个切削具,而切削具所受的岩石反作用力及破岩中的微动载反效应,又施加在钻头体上,同时,钻头体又长期处于岩屑、岩粉流和孔壁的摩擦环境中,因此,必须选择合适的钢体。微钻试验钻头体采用45#钢。由于是室内微钻试验,钻头总的进尺较少,因此对胎体的性能要求比野外钻进胎体的要求要低,选择1#-1胎体配方。根据钻头立体图及胎体配方,计算了粉末的多少,混好粉料,在加工好石墨模具后,进行了装粉与插保径层工作,再加工好钻头钢体,然后采用热压法烧结钻头,选用SM-100E型中频感应烧结设备。为了牢固的焊接PDC,存在着几个难点,首先是PDC有一半左右的高度进入了胎体,怎么保证焊液填满胎体与PDC之间的间隙,从而形成大的焊接面,传统的钻头因为合金进入胎体的深度很小,或是直接与胎体一次成型,因此不存在这个问题,这是一个新的难题；其次是在焊接过程中,如何避免烧伤PDC,用于工业生产的常规PDC的热稳定性为750℃左右,因此焊接的时候不能超这个温度,现在较常规的方法是通过焊液温度来控制这个温度,本文采用中频电源加热感应圈,用银熔焊剂来保持低温；最后的问题是怎样减少焊接过程中对PDC的氧化,现今常用的方法有真空焊、氢气环境中焊接等手段。通过微钻试验发现,试验设计的钻头在硬岩钻进时单环式钻头比能远小于双环式钻头；与单环式钻头相比,在相同的钻压与转速下,双环式钻头受到岩石的阻力很大,传递给钻杆的阻力也很大,要求接头有相当高的强度,低强度的钻杆及接头易损坏；根据有效岩心率ζ的概念,在钻进工艺参数相同、切削齿各项参数相同及数目相同等条件下,ζ越大,钻头效果越好；必须设计合适的钻进参数,使钻头能顺利高效的破岩,且对钻具的反作用力小；在没有围压的情况下硬岩显脆性,经PDC切削的部位都变成了岩粉。第五章是有关野外钻头的研究。根据前面几章的研究成果,设计了野外胎体PDC取心钻头,同时以一种硬岩层为参照,探讨了钻压及PDC面力与钻头整体齿及螺纹受最大mises应力的关系,为施加合适的钻压与转速提供了参考。为了满足较大直径岩心的需求,相比微钻用钻头,野外钻头的内径应有所增大,选定钻头的规格为Φ94/70,采用Φ10的PDC,根据前述的成果,钻头唇面选用平底形,PDC的后倾角选用15.1°,出露高度选用5mm。通过分析旁通角的有利因素与不利因素,同时根据前人作出的一些成果,选取旁通角的大小为7.5°。钻头唇面上共布置9片PDC复合片。根据微钻试验的结论,有效岩心率ζ越大越好,因此选用单环式排列,这样唇面的厚度最薄。通过对切削齿破硬岩进行理论分析,发现PDC主要是靠压剪破岩。运用Ansys软件对钻头进行了受力分析,主要通过改变钻压与PDC面力,来分析钻头所受最大应力与螺纹上的应力的改变情况。观察Mises应力云图可知,在模拟选定的载荷范围内,钻头整体及内螺纹受到的最大Mises应力受PDC面力的影响很大,两者的变化率基本相同,而受钻压的影响较小。总的来说,本文通过大量试验、理论分析及Ansys软件分析,围绕钻进硬岩进行胎体PDC取心钻头的研究取得了一定的成果。更多还原

【Abstract】 China is a developing country with a large number of populations and relative shortage of resources which have become a major bottleneck that constrains the economic development of our country. In order to implement State Council’s decision on strengthening geological work, many drilling of deep hard rock must be carried out. During deep-hole drilling of hard rock about 70% of the time is spent on drilling and pulling out bit from the hole. So the quality accident of a drill bit will cause serious damage in the drilling process. Cost of deep-hole exploration drilling is normally more expensive.The damage of drill bit causes great economic losses itself. Putting down and pulling out the dill bit is a waste of a lot of manpower and material resources. Finding the accident and finding a suitable drill bit to replace the damaged drill bit will take a lot of time. These factors have led to delays in schedules that delay the completion of production plans. It can be seen that quality of drill bit is very important during drilling. We must develop high efficient and long life drill bits which can achieve high speed and efficiency.Impregnated diamond drill bits are mostly used in hard rock drilling in China, and the technology is relatively mature with little room for improvement. While PDC (Polycrystalline Diamond Compact) drill drilling efficiency is several times higher than the traditional diamond drill bit when drilling the soft-medium hard rock. But the PDC coring bits of current level are not suitable for drilling hard rock and very hard rock. When drilling these formations, the drill bit gets collapse teeth easily, wears fast, and drills with slow speed. So using PDC bit in these formations is uneconomical from efficiency and economic factors. We must develop the PDC coring bits technology exteriorly if we want to achieve that kind of drilling results in hard rock such as in soft-medium hard rock. The purpose of this research project is to study matrix PDC Coring Bits based on hard rock drilling that hopes to enhance its ability for drilling hard rock and obtain a better drilling effect.For the purpose of drilling hard rock and based on previous studies, laboratory equipment, Pro/engineering and AutoCAD mapping software, Ansys software are used to study the physical and mechanical properties of hard rock, simulate and analyze the breaking capacity of bit structure on rock, study the material requirements surrounding hard rock, enforce a bit of the manufacturing process and micro-drilling tests, design a field drill bit and discuss its working status and stress.The first chapter summarizes the research status and trends for the PDC bit at home and abroad, including four areas as the rock drillability, drill design, manufacture and working status of drill bit.The second chapter is about Drillability research of hard rocks. Drillability of rocks it’s ability to resist breaking during drilling, which indicates the ease of crushing rock. The purpose of study is to determine whether it is hard rock which can provide physical and mechanical parameters of rock samples for the design of drill bit.Eight kinds of hard rock samples are selected for testing in order to understand their physical components, structure, and their names by slice analysis. Moh’s hardness that is calculated through rock mineral composition respective is as a basis for a preliminary understanding of the extent of soft and hard rock.Drillability level of rock is determined by the main indicators of the joint rocks combined with the ball hardness and ductility coefficient, the PDC Rock DRILLABILITY tables of rocks which was issued by the Ministry of Geology of DRILLABILITY in 1984. Then, the extent of soft and hard rock is determined according to Drillability level, and these rocks are identified by a comprehensive mechanical indicator. The rock uniaxial compressive strength is used to verify the composite indicator of classification. We can see the method that indentates hardness as the main indicators, putting the ball joint rock hardness and ductility coefficient integrated to determine drillability level is reliable coMParing with the results from the compressive strength of rock lithology and comprehensive analysis of indicators. Rock samples of numberl,8 are hardest followed by 4,5,7, and 2,3,6 the softest.The third chapter is about theory research on design of matrix PDC coring bit. The conventional PDC coring bit is only applicable to soft-medium hard rock. We must consider the actual working state of drill bit during drilling if we want to use it for hard rock drilling. Combination of hard rock’s physical and mechanical properties, using experimental and finite element analysis and theoretical analysis and other methods we design the matrix PDC coring bit. The main design contents include the lip surface, cutting tooth, matrix materials, and waterway system.Difficult points of bit lip lies in increasing free cutting face and particularity of drilling hard rock. PDC wears fast when drill bit is used to drill hard rock. Bit lip can acquire more free cutting face by adopt step lip or double-loop bit lip. Exposed height of PDC should be on a plane to avoid stress concentration that is shared on PDC because of the large bit pressure of drilling hard rock.Research contents around drilling hard rock to study the cutting teeths include selection of suitable PDC, PDC arrangement, caster angle and bypass angle of PDC, and the exposed height of PDC in order that all aspects of cutting teeths can meet the good effects of breaking rock. It’s found that the wear resistance of PDC is strong; short-term wear and tear of grinding on the PDC is negligible. PDC is structured suitable for cutting rock by cutting test.Right typical categories of coring bit are sharpening and self-sharp-style-type drill bits among which needle-like bit, dig and drill bit, row-like bit show strong capacity when drilling hard rock. Bit with row-like structure is more appropriate in hard rock drilling regarding PDC as special carbide to design drill bits. Law of force of the rock in the process that PDC with different angle and height of the drill bit cuts the rock is acquired by drawing model of drill bit and rock with Pro/engineering software and importing the model into the ANSYS software for stress analysis coMParison. Observing stress distribution maps and coMParing Mises stress generate from change of caster angle, the locations of the maximum stress of the rock are basically the same, indicating rock damage is most likely to start here during process of breaking rock except the model of 1537540; the maximum stress of rock increases at first, and then becomes smaller. From the point of the maximum stress of the rock, it’s more reasonable for PDC bit to select 15.1°as caster angle. Observing stress distribution maps and coMParing Mises stress generate from bypass angles the locations of the maximum stress of the rock are basically the same which indicate rock damage is most likely to start here during process of breaking rock except model of 1537240; the maximum stress of rock increases along with bypass angle except the model of 1537540, subjecting to maximum stress of the rock with the bypass angle increases. Cconsidering the point of the maximum stress of rock, the bigger PDC’s bypass angle is the larger the stress of breaking rock of the bit is. Observing stress distribution maps and coMParing Mises stress generates from exposed height of PDC, the rock by the position change of the maximum stress is relatively large; remove model 1537537, the maximum stress of rocks increases at first, and then decreases. The exposed height of 4.0mm is a sub-interface. Considering from the point of maximum stress of rock, PDC’s exposed height of 4.0mm is a more appropriate choice.About matrix material design, analyzing test result, from different formulations, we can see the average hardness of the histogram increases with the increasing of WC content. The hardness and density matrix express upward trend when content of Cu-Sn alloy reduce; with content of WC increasing and content of Cu-Sn alloy decreasing, iMPact resistance and flexural toughness strength of matrix express downward trend from the average bending strength of different formulations and different histograms formula, and the average iMPact toughness of the histogram.About design of waterway system of bit, design of discharge area expresses in design of areas mainly. The paper discusses the relationship between the PDC number, PDC in size, the support size of after each piece part of PDC, the volume of PDC in the matrix, the depth of PDC cutting into the rocks and discharge area, and points out that layouts of cutting teeth on the lips of bit should be conducive to exclude debris. Because bit is used in hard rock drilling, full flush-type outlet, also known as plum-type outlet is used taking into account the first outlet layout of pregnant diamond that drills hard rock.This outlet is characterized by forcing the washing fluid flow out along the edge of the PDC, and form flow between the gap of the matrix and the hole at the end of the formation of rock which can fully cool PDC and remove debris. Gap on the inner and outer ring, inner and outer ring gap of drill bit should be designed to ensure the realization of the function of drill fluid.The fourth chapter is about pilot study of micro-drill. There are three aims to carry out micro-drilling tests on the drill bit, first, to be familiar with manufacturing processes of drill-bit, and second, to study the arrangement of PDC by using micro-drill bit in hard rock drilling, and finally to understand the requirements of hard-rock drilling on the drill bit further according to the status of micro-drilling processes.Three small bits are designed. Each bit has 6 PDC per one, caster angle is 15.1°, by-pass angle is 7.5°, the exposed height is 4mm which remain unchanged, thickness of he bit lip surface and the arrangement of PDC on the bit lip surface is changed, and single-loop and double-loop layout are used respectively.Preparations of the construction material of drill bit include designing and manufacturing mold at first. Two aspects must be taken into account:one is whether the graphite mold can bear the sintering pressure which the powder needed during the sintering process to form bit. That is to say the mold won’t be crushed because of low endurance in the range of sintering pressure; the second is whether the temperature of large-diameter drill graphite mold can drill up to the required sintering temperature that the formula needs during sintering process.Bit body as a support body of PDC delivers axial force and torque to each cutting tools, and suffers a reaction and the micro-containing counter-effect during breaking rocks, but also lies in the environment of a long time in the debris, rock powder flow and pore-wall friction, therefore, we must choose appropriate steel body.45# steel is used as bit body in micro-drill pilot. Because it is micro-drilling tests indoor, and the total footage of bit is short, requirement to performance of matrix is lower than that in the wild-drilling. Matrix formulation of 1#-1 is chosen.How much of the powder is calculated according to three-dimensional maps of drill bit and matrix formula. Powder is loaded and the installation path layer are inserted after powder is mixed and graphite mold is fabricated, and then a good bit processing steel body, and then hot-pressing sintering method is selected to sinter the bit with SM-100E medium-frequency induction sintering equipment.In order to welding PDC firmly, there are several difficulties, firstly, it is how to ensure solderability liquid filling the gap between the matrix and the PDC to form a large welding surface since about half of the height of the PDC into the matrix. There is no question about the traditional drill because the depth of alloy into the matrix is very small, or the alloy forms the bit with the matrix directly at once. So this is a new problem; secondly, it is how to avoid burning PDC during the welding process. Welding temperature should never exceed 750℃since conventional thermal stability of PDC of industrial production is around 750℃, and now conventional approach is to control the temperature of molten solder. In this paper silver melting flux is used to maintain the low temperature with medium frequency induction heating power supply ring; lastly, it is how to reduce oxidation to PDC during the welding process. The current methods are in vacuum welding, welding and other means of hydrogen environment commonly.There are certain conclusions through the micro-drilling tests:specific energy of single ring bits is far less than the double-loop bit which are designed to drill hard rock; comparing with single-ring drill bit under same WOB and speed, double-loop bit receives larger stress of rock, resistance passed to the drill pipe is also lager, require higher strength of the joint of bit, and low-intensity drill pipe and joints are damaged easily; according to the concept of the effective rock heart rateζ,ζbigger the better drill bits in the drilling process of same parameters, cutting teeth and the number under the same conditions; suitable drilling pressure and torque are needed to so that the bit can break rock smoothly and efficiently with small reaction force; hard rock expresses brittle, and become rock powder when PDC cut through it in the absence of confining pressure circumstances.Chapter V is research about the field drill bit. According to research results in the preceding chapters, field matrix PDC coring bits is designed, and refer to a hard-rock, the paper discusses the relationship between WOB, surface force of PDC and the largest force of the whole bit and the thread subject which provide reference for imposing appropriate drilling pressure and speed.Compared with micro-drilling bit drill diameter of field bit should be lager in order to meeting the needs of a larger core diameter. Specifications of the selected drill bit isφ94/70 which used PDC ofφ10, labial surface of flat-bottomed shape, caster angle 15.1°, and 5mm as the exposed height of PDC according to the aforementioned results. We select 7.5°as the size of the bypass angle by analyzing favorable factors and unfavorable factors of bypass angle combining with some achievements of the predecessors. Nine PDC are fixed up on the lip surface totally. Single-loop arrangement of bit is selected according to the conclusions of micro-drilling tests that the biggerζis the better is the bit, so that the thickness of lip surface is thinnest.It’s found that PDC breaks rock mainly by compressive-shear affect through theoretical analysis that the cutting tooths break hard rock. Finally Ansys software is used to analyze mechanical force of bit mainly by changing the WOB and surface force of PDC to obtain the greatest stress and the stress of the bit and change of force on the thread. By observing nephograms of Mises stress on the selected boundary rate of change, the maximum Mises stress of the whole bit and internal thread receive a tremendous influence of surface force of PDC which is basically the same in the rate of change but less affected by the drilling pressure.In summary, based on hard rock drilling tests, this paper makes some achievements on matrix PDC Coring Bits research by a large number of tests, theoretical analysis and analysis with Ansys software.更多还原