| Natural gas hydrate is a kind of new energy which is efficient andclean, and has the advantages of high burning calorific value,pollution-free and huge amount of resources. So all countries in theworld regard it as an important reserve of energy strategy development,and it will be the first choice to replace the conventional oil and gasresources in the future.From the1990s, natural gas hydrate has become a research hotspotat home and abroad. At present, scientists have carried out a lot ofresearch for the physical properties of natural gas hydrate, and havemade significant progress. However, the achievement of exploration andexploitation of natural gas hydrate is few. In order to make the naturalgas hydrate become a new energy alternative to conventional energysources veritably, it is requisite to research the exploration andexploitation of natural gas hydrate.Drilling for coring to obtain high fidelity of natural gas hydrate isthe most direct method to verify the existence of natural gas hydrate. Atpresent, according to the temperature and pressure characteristics ofnatural gas hydrate, there are mainly two kinds of sampler, pressuremaintaining and freezing, for natural gas hydrate at home and abroad,the pressure maintaining sampler is mainly to maintain the pressure inthe hole, and to make the hydrate sample keeping high pressure, so doesnot decompose in the normal temperature; Freezing sampler is mainlyfreezing at the bottom of the hole, and to make the hydrate samplekeeping low temperature, so does not decompose under ordinary pressure.Based on the characteristics of natural gas hydrate, there are avariety of exploitation methods for natural gas hydrate, in which theresearch of heating method, the press dropping method, Chemicalinjection method and CO2displacement method is more, additionallythere are and slope well method and mining method. Currently, from aworld-wide perspective, there are at least five places has carried out theresearch exploration of natural gas hydrate so far.In this paper, the drilling and production technology of natural gashydrate is studied. On the drilling technology, and through the FCS typegas hydrate in frozen sampler of the bottom of the hole structure,working principle and indoor and outdoor test results were analyzed,the dry ice storage effect of FCS is good, but the storage of coldquantity in the freezing mechanism is less, at the same time, theconsumption of cold quantity cannot get timely supplement, the abilityto frozen core has certain limits. Efficient heat transfer original--heatpipe is introduced into the bottom of the hole gas hydrate samplesrefrigerated sampler, designed the papid freezing mechanism of naturalgas hydrate samples of hole bottom.In order to study the use of heat pipe in the freezing mechanism，Used the ANSYS finite element analysis software to carry out thecomparative analysis of heat transfer simulation between the freezingmechanism which don’t have heat pipe and the rapid freezingmechanism which have heat pipe. From the nephogram of temperaturechanged over time of the longitudinal heat transfer simulation results ofthe two kind of mechanism we can know, the freezing function for coreof the freezing mechanism which have heat pipe is significantly betterthan the freezing mechanism which don’t have heat pipe. No matter the heat transfer speed, the heat transfer efficiency, or the heat transferrange, the freezing mechanism which have heat pipe is better. From thetemperature variation curve of core of the longitudinal simulation of thetwo kind of mechanism we can know, the temperature of core peripherydropped quickly than the temperature of core center, and thetemperature of core upper part dropped quickly than the temperature ofcore under part. The freezing process of core is from top to bottom, andfrom outside to inside, that is the temperature of core upper partdropped first and then the temperature of core under part dropped, thetemperature of core periphery dropped first and then the temperature ofcore center dropped., The core came out a tendency of temperature whenthe temperature reach-9℃. And carried out the horizontal heat transfersimulation of rapid freezing mechanism. From the nephogram oftemperature changed over time of the horizontal can know, despite theheat pipe in rapid freezing mechanism is not tightly hold the core,because of the non-uniformity of the temperature field produced by theinterval distribution of the heat pipe only influence the alcohol inannular gap and don’t have influence on core, there won’t occur the badsituation that one part of core is frozen but others is not frozen duringthe process of freezing core.In order to further study the use of heat pipe in the freezingmechanism， designed and established the hole bottom rapid freezingmechanism test bench, carried out two comparative test of between thefreezing mechanism which don’t have heat pipe and the rapid freezingmechanism which have heat pipe. The test condition of first test is： thecore freezing chamber don’t add insulation, core tube don’t add core.The test result is: at the upper part and middle part of the inner wall ofthe core tube and upper part and middle part of the annular gap of core tube chamber, there is no much difference of the temperature droppingspeed and the final temperature of1300s between the freezingmechanism have or not have heat pipe. And at the under part of innerwall of the core tube and under part of the annular gap of core tubechamber, the temperature dropping speed of the freezing mechanismwhich have heat pipe is much faster than freezing mechanism whichdon’t have heat pipe, and the final temperature of1300s of freezingmechanism which have heat pipe is lower than freezing mechanismwhich don’t have heat pipe. Through the analysis can arrive at theconclusions: freezing mechanism which have heat pipe can expand thescope of the cold transfer effectively, and increase the cold transferefficiency. The test condition of second test is： the core freezingchamber add insulation, core tube add core. The test result is: at theupper part, middle part and under part of core surface and core center,not only the temperature dropping speed but also the lowest temperatureand the final temperature of1300s of freezing mechanism which haveheat pipe have a better result than freezing mechanism which don’t haveheat pipe. The temperature dropping speed of freezing mechanism whichhave heat pipe is faster, the lowest temperature and the finaltemperature of1300s of freezing mechanism which have heat pipe islower. Through the analysis can arrive at the conclusions: freezingmechanism which have heat pipe can increase the heat transfer speedand heat transfer efficiency.To improve the ability to work for the bottom of the hole frozensampling drill, combined the quick coring method of wire line coringand preserving sample method of rapid freezing of hole bottom,designed the natural gas hydrate wire line coring hole bottom rapidfreezing sampling drilling tool, increase the core is freezing speed and scope, increasing application of coring depth. Drilling tools are dividedinto three parts: start part, control part and frozen part. Start partincluding: the spear and positioning mechanism, suspension andactivation mechanism, single-action and inner tube protectionmechanism; Control part including: control mechanism, alcohol storedmechanism; Freezing part includes: cold source storage mechanism,centering mechanism, core rapid freezing mechanism and coringmechanism. Parts of drilling tools and the main mechanism of structureand working principle are introduced, and the main parts are designd.Research for the permafrost regions of natural gas hydrate miningtechnology.According to the principle of natural gas hydrate heatmining, designed the steam heating trial mining system, and the steamgenerator heating power of40kw. Determined after the indoordebugging test mining system exhaust valve opening pressure of1.0MPa,close the pressure of0.5MPa. Carried out the field test in the Chinesepermafrost hydrate first trial mining well. And made the hydratedecomposition successfully, obtained the natural gas. The data obtainedduring trial mining process of press dropping method and steam heatingmethod were analyzed. In this field trial mining test, the efficiency ofpress dropping method is higher than steam heating method; theinstantaneous flow rate of press dropping method is less than steamheating method; the energy of the natural gas obtained by steam heatingmethod is less than the energy consumed by steam heating.In this paper, heat pape papid freezing mechanism of natural gashydrate samples of hole bottom was put forward, and carried out theheat transfer simulation and indoor test, how that heat pipe can improvethe effect of freezing cores by freezing institutions, but not to optimizethe choice of heat pipe, need further studied. Design and test for the gas hydrate steam mining system, but can’t obtain complete data because ofthe conditional limitation, energy conversion rate is not ideal at thesame time, the need to further research in the future work. |
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