| The social, resources and environment are closely correlated to our daily life with theblooming and development of the social economics, especially in21century. Every countryincluded China has the increasing demands for various mine resource and energy resource,especially the demands for oil and gas resource, iron ore, coal and other black metals. Inaddition, this huge demand has started to rank first place all over the word. In the meantime,the exploration as well as exploitation of mining resources deposited in shallow and easilyexploiting formations is near the end. However, remote areas in Midwest of China have notbeen fully exploited with mineral resource due to the complicated geological conditions andnatural environment. Now days, the influence of resource supply and price problem onChina’s economic development will gradually arise. In order to maintain the stable growthof China’s economic, it should be based on domestic and researches on advanced drillingequipment and drilling technology should be conducted, which is particularly important toensure the supply of various resources.The reverse circulation drilling technology of hollow through DTH air hammer is a setof efficient coring with DTH air hammer, full-hole reverse circulation with drilling fluids,and continuous coring without power lack. The drilling efficiency of this technology can be6to10times compared to the conventional drilling methods. There is no erosion for thewall of borehole while drilling with full-hole reverse circulation technology, and the corescan be continuously obtained without persistent rotation. This technology can be used in thedrilling exploration in remote areas in Midwest of China, because it can’t be limited bywater, season, broken stratum and hard rock. Now, this technology is of internationaladvanced level and a large number of productive drilling problems can be solved by utilizing this technology. However, few detects has been found in the promotionalapplication process when drilling with this technology. With the development of drillingequipment, especially the great improvement of air compressor, the application of largeairflow and high pressure compressor have two opposite aspects. On the one hand, it canimprove the drilling efficiency with the DTH air hammer. On the other hand, the corerecovery is not qualified and the compressed air flows out of the orifice while drilling inextremely complicated stratum, such as broken and fractured formations. The DTH airhammer is the key component of hollow through reverse circulation continuous coringtechnology, and the successful promotion application of this advanced technology can belimited by the performance of the DTH air hammer, so it is necessary to conduct thedetailed theoretical and experimental research.Series of reverse circulation drill bit with different structural parameters have beendesigned by Jilin University in the20years of continuous study, but there is no quantitativeanalysis shows that the structural parameters could have an impact on the performance ofthe reverse circulation drill bit. Furthermore, once the reverse circulation can’t be generatedor the reverse circulation is not enough, the structure of the drill bit is just adjusted in thedrill site, which is not the quantitative analysis for the performance of the reversecirculation. Therefore, the structure of the applied reverse circulation drill bit has beenanalyzed in this paper, and the local structural modification is a good direction for theimprovement of the drill bit, on the other hand, some modification should be avoided bythis analysis. In the end, the experimental design and optimization can be obtained for thelocal structure of the advanced drill bit, and it can provide the theoretical and experimentalsupport for the design of reverse circulation drill bit with high-performance.Specific contents and conclusions of this study are as follows：1.This paper summarize design features of4reverse circulation bit tester in the past20years by our group。Aiming at their shortcomings (only for special drill bit size, cannot beused to test the effect of reverse circulation bit entities), and combined with the pumpkin inthe production test problems in the using process, we design the multifunctional FZS-89-00reverse circulation drilling simulatorcreatively.Expounds the design objective in detail,FZS-89-00reverse circulation drilling simulator’s design principles and detailed structuresof each part of it with the respective function.Finally, we introduced the laboratory test equipment, test and measurement equipment which are used in reverse circulation bit testdesign, pile connection which is used in the indoor test(closer to the construction site) etc.2.We summarized the development history, structure and working principle of themulti-ejector hollow through DTH reverse circulation drill bit, the optimizationimprovement and their respective field application test.According to the improved schemewhich can achieve the anticipated effect in the field test and application, improvementwhich cannot achieve the drill bit with splined inner nozzle, laboratory experiments weredone using FZS-89-00pump kin, find out the cause of the problem.3. According to structure and practice in the production test, we select optimization ofreverse circulation bit as follows: the locations of inner nozzles use the arrangement ofdouble spiral nozzle in the double-nozzle reverse circulation drill bit, the bottom nozzle andbottom working face of the drill bit is arranged on the basis of the arrangement of spiralcutting edge.4.Using orthogonal design and EFD simulation techniques, on the theory basis ofnumerical simulation, using FZS-89-00reverse circulation bit simulation tester, we studyand discuss the influence of many parameters on the reverse circulation drill structureeffect,for optimal values for the parameters of each structure and the optimum combinationof structural parameters of the bit structure.And then an optimal bit structure parameters ofreverse circulation effect was selected,providing data and theoretical basis for thesubsequent production test and application.After verification of theory and test, double rowinner nozzle holes and spiral diffuser slot form is conducive to reverse circulation bit pumpon the air in the external ring gap, is a future direction of bit design.5.Large diameter pneumatic reverse circulation bit which is designed using Ejectorprinciple is used to solve the construction problem, slag.In the design process of the drill bit,orthogonal test design is used to drill bit structure parameters,we optimized optimal bittheory parameter combination. At the same time6bit structural parameters significantlyaffect the target value Q. The order of each factor in L8(27) and L18(37) orthogonal tableare consistent.Primary and secondary order of their effects on the target value Q is: nozzle diameterDn, nozzle number N deflection angle θ D, nozzle, nozzle angle θ s, boot diameter Dg, nozzle length L.Q which is obtained by the optimal theoretical parameters combination aremore than that in L18(37) orthogonal table consistently. And Q which is obtained by theoptimal theoretical parameters combination is not in L18(37) orthogonal table.The main innovations of this paper are as follows:1.The design of FZS-89-00reverse circulation drilling simulator is close to the actualconditions of reverse circulation drilling and functional diverse.It can simulate theconditions of the reverse circulation drilling under a variety of formation,can test reversecirculation effect of a series of real reverse circulation bit.And we can change regulatedrilling parameters conveniently and quickly.With a lot of parameters measurementinterface,we can measure conveniently.2.For the production test of on-site problems that reverse circulation effect was notperfect,according to the theoretical analysis and experimental study, we explain mainlyfrom the structure and velocity within the spray hole,which illustrate that effect of innernozzle length and path of fluid into the inner orifice are very strong.3.Modular drill designed by us has the following features:drilling parameters canchanged conveniently and quickly and it can be used as the drill bit physical experiment atthe1:1ratio. After select an optimal bit structural parameters combination in the singlefactor test conditions,orthogonal test design is used to them,and considering the effect of theinteraction term. After orthogonal test design is used to FZS-89-00reverse circulationdrilling simulator,we can come to a conclusion: the obtained the optimal parameters isconsistently to theoretical analysis.4. Ejector principle was innovatively applied to the design of pneumatic large diameterDTH air hammer reverse circulation drill bit, and achieve a stable reverse circulation effect,which is conducive to solve a thorny problem of large diameter drilling slag in complicatedstratum drilling under the complex formation.And we applied the orthogonal test designprinciple to analysis the bit structure parameters,figured out a bit structure parameterscombination with which DTH hammer can achieve optimal reverse circulation effect. |
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