Theoretical And Experimental Research On Reverse Circulation Constant Sampling And Powerful Compressed Air Spurting Drilling Technology

Air drilling is a drilling technique that uses compressed air or mixture of air and fluid as its circulation medium or penetration power during drilling process. Nowadays, air drilling has already come to be a multi-technique air drilling system. This drilling technology uses dry air, pulverization, foam, air mud and other low density substance as its circulation medium, uses regular circulation,reverse circulation with double-walled drill stem,reverse circulation with air lifting,regular and reverse circulation at one time and other ways as its circulation technique and uses rotary, percussive-rotary and other ways as its rocks broken up technique. It is concerned that air drilling is one of the drilling technology which is widely carried out and has most potential of development because of its perfect technology connotation and its larger and larger application field. At the same time, air drilling is also used widely in many fields such as geology prospecting,oil and gas drilling,hydrology and water well drilling,mine excavating,geology disaster prevention and cure,civil engineering construction.This article, combining mature jet drilling theory and drilling mechanics of air reverse circulation constant sampling with double-walled drill stem which circulation medium is based on compressed air aim to research a new air drilling technology---the reverse circulation constant sampling and powerful compressed air spurting drilling technology. It can penetrate as thick as tens and hundreds meters of loose overlay or relative soft rock on the earth's surface, and make drilling efficiency much higher, keep drilling cost low down and overcome the difficulty of fetching water. Particularly, it is absolutely available when the DTH is working in complex stratum such as the interlayer between soft and hard stratum,silt stratum and sand bed. If unite the powerful compressed air spurting drilling technology and hollow DTH reverse circulation constant sampling drilling technology (that is to say: the powerful compressed air spurting drilling technology is adopted when drilling loose overlay or relative soft rock on the earth's surface and hollow DTH reverse circulation constant sampling drilling technology is used when drilling hard rock under overlay stratum, it will undoubtedly solve the drilling problems in the regions hard to fetch water and bring lots of economic and social profits.Reverse circulation air spurting drilling technology has some extra advantages as follow:(1) It can successfully solve troubles during works in fetching water at places lack of water. If encounter moist stratum, the heat from high pressure air can drying them and then makes them become mud balls. The balls come upwards to the ground by circulation. Consequently, the drilling efficiency is raised and the cost is also cut down.(2) When drill loosen ground loess, it can avoid drilling accidents like diameter shrinking,hole sink,bit block and burying cause by expanding when the loess meets the water. This can still raise drilling efficiency and shorten the time limit for projects.(3) When drilling soft rocks(soil), assisted by mechanical breaking, the high speed air breaks rocks(soil) by spurting at them, with low velocity of bit abrasion, even without changing bit in this whole drilling process. And this reduces the waste of time and improves the penetration rate.Reverse circulation air spurting drilling technology is realized by two aspects, on one hand, it uses compressed air as its flush and circulation medium, on the other hand, it use the high speed air current which is formed when compressed air spurts out from the nozzle to penetrate, rip and cut the stratum. Meanwhile, high pressure air from dual channels tap goes into the gap of dual wall drill pipe, and then come to bit. When complete penetration process, the air from the bottom of the bit goes into the central channel, and then brings the chippings to surface. This process makes the counter-circulation air drilling in the whole hole come true. Drillingprinciple is illustrated as figure 1. Obviously, to do researches on reverse circulation air spurting drilling technology, we should take advantages of fluid dynamics, air dynamics, spurting dynamics, air spurting dynamics and multiphase fluid kinematics and dynamics to do researches on the mechanics of high speed air breaking rocks(soil) and residue education by reverse circulation. Generally speaking, this article mainly completed these contents as follows:(1) Researches on mechanics speciality of circulation medium and the air kinematics and dynamics theory of the compressed air in the pipe.During the process of the high speed air taking rock chippings up to ground from the bottom of the hole, the air commingles chippings and becomes multiphase flow. To research on its mechanics speciality, it is important to pay attention to its affects and transformation disciplinarian of density and conglutination, this is the precondition to build the theory of the fluid dynamics of air drilling.Compressed air spurts out from the nozzle of the bit and forms a high speed air current to penetrate stratum. The spurting current and high pressure air has a power, and the power transforms from pressure power to velocity power. The air needs to expand, absorb heat, and work, during this process, it is important to research the flow disciplinarian of the air traveling in the dual walls drill pipe and the nuzzle, and work on the spurting kinematics and dynamics of the air spurted from the nuzzle as well.(2) The primary test shows that we can achieve a high speed of drill in by the mean of using high speed gas to shoot the soft ground. To increase the rate of shooting with the high speed gas, and to get a fantastic effect, we need to have a research on the mechanism of shooting the rock (earth) with the high speed gas.Here is no adult that to remove the rock pieces and to decrease the iteration of broken is one of the main processes. We could have a strong capacity of removing the rock pieces, getting the bottom of the hole clean, a high rate of drilling in, continuous sampling the sample and no pollution to the sample by using reverse circulation drilling. How to make the gas shooting return from the central of the drill to achieve reverse circulation drilling? We need to have a research on the drill at the bottom of the hole and reverse circulation mechanics of the central pass of dual walls drill pipe with the theory of gas transportation and man-made cyclone.(3) Using the analysis of numerical value and Fluent liquid software to have a simulation to the surrounding and the inside gas transportation of the counter circle insufflation bit.In recent years, as CFD software is mature and be spread, it has become a tendency of using numerical value to calculate the gas shooting at the bottom of the hole, using CFD software to simulate the numerical value of the drill's situation and the inside gas shooting and to optimize the construction of the shooting channels have also become a tendency. It has been proved that we can optimize the construction of the shooting channels decrease the calendar of research and use unreal tech to replace the practicality experience by using CFD tech to reduce the research cost. This article has definite meaning and help to the research of reverse circulation drilling mechanism with CFD tech.(4) the design of jet bit structure of counter circle drill, manufacture of sample bit and the research of experiment.Through the theory above, and combine the experiences from the testing group who has been working on the reverse circulation bit of hollow-through DTH, we designed few kinds of jet bit with different diameter, structure and style, and we made a sample machine (showed in pic. 2) to have a test on it in the open air, drilled into the earth, and a single drill reached 20 meters below the surface, and the cumulation of drilling was about 200 meters, and the speed of the drill got to 90 m/h, and we acquired a good effect ( showed in pic.3), by comparing the drilling rate and the effect from different drills, and analyze the result, we put forward the plan of optimizing the drill.Above all, this paper receives the past theory related and research results, and also stands out its own characteristic and innovation:(1) For the first time, use air spurt dynamics to do researches on the mechanics of rock broken by high speed spurting air current,and use "air transportation" and "manmade cyclone" theory to do researches on mechanics of the whole hole counter-circulation and residue eduction, and apply the both theory to exploration field.(2) This article, combining mature jet drilling theory and drilling mechanics of constantly sampling of dual walls air reverse circulation drilling which circulation medium is based on compressed air, aim to research a new air drilling technology.(3)And at the same time, theoretical research combining with wild experimentation, the article designs jet bits with different structures and types, and these bits were good to drill,so that the article preliminarily and profitably researches on reverse circulation constant sampling and powerful compressed air spurting drilling technology,...