Simulation And Application Research On The Mud Cooling System For Gas Hydrate Drilling

The rapid development of the world economy has brought great pressure to the supply of the traditional energy.Finding new energy has been the urgent problem to solve for every country especially the countries that lack of energy.Gas hydrates as a largely reserved, widely distributed and less polluting new energy has been included in many countries'energy strategy plan.The exploration of the area and depth of gas hydrates storage is the premise to the exploitation.How to get the more fidelity gas hydrates samples has become the prime consideration for the drilling project.According to the thermal physical properties and the temperature and pressure conditions of gas hydrates, shuold reduce the energy input into the bore and the wall of the hole in the drilling process, so cooling the circulating mud is the necessary drilling technology.Through the application of domestic and international status of the mud cooling system we can find that there is not a drilling mud cooling system fit for Chinese permafrost gas hydrate scientific drilling, so developing a suit of drilling mud cooling system fit for Chinese permafrost gas hydrate scientific drilling is very urgent.After repeatedly discussion of mud cooling system overall design and comprehensive consideration of the field conditions, get the technical program draw of the mud cooling system firstly according the drilling technology requirements of the project, obtain the refrigeration unit power of mud the mud cooling system. and then design the mud cooling system with theoretical calculation based on the heat transfer, heat exchanger theory, fluid dynamics and other related knowledge to get the diameter, the length and the pressure loss of the pipe and finally Select the corollary equipment of the mud cooling system according these date.Using fluid analysis software FLUENT to simulate the mud cooling system to verify the reliability of theoretical calculations by the results. Finally, can get these result as follows by analyzing the temperature nephogram and the temperature curve of the numerical simulation:the temperature of the entrance can ruduce 5.4℃by the exit from 0℃to-5.4℃with the same boundary conditions of the.this result is better than 2℃temperature difference of the theoretical calculation.This shows that theoretical design is safer and can do. can get these result as follows by analyzing laboratory tests dates:in the beginning the mud temperature is high and the temperature difference of the entrance and the exit can be up to 5.8℃, while the average temperature difference has reached 2.22℃throughout the whole process and the final temperature of the mud pool are maintained at -5℃, indicating that the laboratory test result is good and the mud cooling system can be applied in the field project.The mud cooling system has been applied in the Muli basin natural gas hydrate scientific drilling project in 2009 and 2010.in the 2009 scientific drilling project, at the beginning the mud freeze and block the pipe this is beccause that the low temperature resistance of the mud is weak.obatain a suitable temperature range of refrigeration units by numerical simulate using FLUENT software. the average temperature difference of import and export reached about 3℃in the next applications and the mud temperature is maintained at 0℃～2℃that the drilling Technology required.Eventually for the first time get the fidelity gas hydrate samples in Chinese permafrost.From the application situation in Muli basin the mud cooling system also has many disadvantages. improve and manufacture the second generation the entire mud cooling system in 2010 and apply it in the Mohe gas hydrate Scientific drilling. the second generation of gas hydrate mud cooling system is more convenient to use and the effect is prefect. by theoretical calculations in the same requirements and conditions can find that the cooling effect of the screw thread pipe is much better than the smooth pipe.