| The ice in the south and north regions contains the complete information of the ancient climate and paleoenvironment of the earth.We can speculate on the changing trend of the climate in the past millions of years or even tens of millions of years ago.Through the thick ice layer,to study the nature of the ice layer contacted with the ice bed.To study situation of mineral deposits and the structure characteristics of strata,as a longer-term goal.The only way to get ice and bedrock information is drilling.As early as 1840,Agassiz,the glacier theory founder,began first drilling attempt in the Alps.Then countries have also sent a delegation to the polar region,from the initial manual drilling drill into the superficial ice,to current armored cable electric machine drilling tools,successfully drilled to the deep ice,made hundreds of meters of ice core samples.Drilling fluid is indispensable during polar drilling.As the same with the geologic core drilling,drilling fluids play an important role in maintaining the stability of the hole wall,cooling the bit and cleaning the bottom of the hole.As the ice easily melt and creep,some new requirements to type and performance of the drilling fluid.Polar drilling fluid at low temperature,not only to have the appropriate density and viscosity,but also have:(1)low conductivity,do not damage the soaked electronic components;(2)high thermal conductivity,quickly take away the heat generated by the drill bit to prevent the ice melt;(3)no corrosive,have no effect with drilling,sealing components and rubber products.In order to prevent the ice and ice core melt,drilling fluids used in polar drilling are mostly hydrophobic media.The types of drilling fluids that have been applied are kerosene-based drilling fluids,ethanol aqueous solutions and ethylene glycol aqueous solutions,butyl acetate.However,kerosene-based drilling fluids are heavily polluted the environment.The ethanol aqueous solutions and ethylene glycol aqueous solutions is resistant to pore walls and ice cores.Butyl acetate has a dissolution effect on the rubber products in the field.Therefore,they are not the best drilling fluids for polar drilling.After the previous theoretical analysis and research,there are six kinds liquid medium have the potentialto do the polar drilling fluid,which are:(1)dimethyl silicone oil,domestic silicone oil and KF96 silicone oil;(2)fatty acid esters,butyrate and propyl propionate.The research and testing of six kinds of density and viscosity have been completed,and its performance satisfies the requirements of polar ice core drilling.But its conductivity,thermal conductivity and the swelling effect of the sealing element have not study,need for a complete test and research work.(1)Using DDSJ-308 F conductivity tester to test the conductivity of pure liquid medium and mixed with ice-stained liquid.The conductivity of domestic silicone oil,KF96 silicone oil,butyrate butyrate and amyl butyrate was 0.000?S / cm at room temperature(20?),and it was non-conductive liquid.The conductivity of ethyl butyrate and propyl propionate was 0.003 ?S / cm and 0.002 ?S / cm,with very weak conductivity.When mixed with 5% and 15% of the ice,the content of ice have no much influence on the conductivity of the solution.The temperature at-60 ~-5?,six kinds solution conductivity does not exceed 0.02?S / cm.On Antarctic,temperature always at-60 ~-50?,and the conductivity of the medium 0?S / cm,will not affect the normal work of drilling tools.At 0?,due to the phase transition temperature of the ice,ice melted,resulting in a sharp increase in electrical conductivity.At the same temperature,the conductivity of fatty acid esters is generally less than that of silicone oil,butyl butyrate and amyl butyrate has the lowest conductivity,and fatty acid esters can prevent the ice sticks from adhering to the conducting electrode.It is possible to form a protective film on the surface of the drill bit to prevent the ice stick from sticking the drill bit,which is very advantageous for the warm ice drilling.(2)The thermal conductivity of the medium was measured by DRE-? transient planar heat source method.The thermal conductivity of the six liquids was decreased with the temperature decrease.At the same temperature,the thermal conductivity of fatty acid esters is much larger than that of silicone oil.The thermal conductivity of propionate is the best,followed by ethyl butyrate.At-50?,the thermal conductivity of the six liquids is between 0.015 W /(m · K)to 0.065 W /(m · K).According to the actual drilling parameters,if not using drilling fluid,temperature of cutter will rise 3.5?,and the use of drilling fluid can make cutter a significant cooling down.Antarctic temperature at-60 ~-50?,the bottom of the hole actually produce 95 KJ calories,six kinds media can take it away in time to meet the requirements of polar drilling.(3)Due to the special polar environment,the rigging components of the cold resistance,chemical resistance,resistance to deformation and mechanical high requirements,polar commonly used sealing materials are silicone rubber,fluorine rubber,polyurethane and polytetrafluoro Ethylene four kinds.It is found that with the increase of soaking time,the amount of swelling is gradually increased,and when it reaches a certain value,it does not change,and the lower the temperature,the smaller the total deformation.Silicone oil has a strong swelling effect on silicone rubber,which may be due to the silicone oil molecules and silicone rubber molecular structure contains silicon oxygen atoms and in the structure of a similarity,similar compatibility.Between-25 ~ 25?,domestic silicone oil on the silicone rubber swell 21 ~ 33%;KF96 silicone oil on the silicone rubber swell 25 ~ 38%.KF96 silicone oil swell ability stronger than domestic silicone oil.Silicone oil on the fluorine rubber,polyurethane and polytetrafluoroethylene is no swelling effect.Because the fluorine rubber chain with fluorine atoms,the outer layer by the protection of fluorine atoms;and polyurethane and silicone oil molecular differences are large,and the molecule is not unsaturated;polytetrafluoroethylene CF bond bond strength,chemical Stable and inert,so the swelling of the role of silicone oil.Fatty acid ester liquid only has no swelling effect on polytetrafluoroethylene,silicone rubber,fluorine rubber and polyurethane have different degrees of swelling.(1)Four kinds of fatty acid ester liquid silicone rubber swelling effect is not much difference between-25 ~ 25 ?,silicone rubber deformation in the 28 to 38%.(2)The swelling of fluorine rubber,propyl propionate the strongest,followed by ethyl butyrate,butyrate,butyrate butylobutate swelling is far less than the other three.In the range of-25 ~ 25 ?,the deformation amount is 58 ~ 68%,54 ~ 64%,51 ~ 56% and 21 ~ 54%.Propyl propionate is the same as the molecular weight of ethyl butyrate,but the molecular chain of propyl propionate is short,so the penetration rate is fast and the number of entry is large.For the molecular weight and molecular chain length,pentyl butyrate> butyric acid butyl ester> butyrate,so the amount of deformation of fluorine rubber is opposite.(3)Fatty acid ester liquid has a slight swelling of polyurethane,which is the strongest propionate,followed by ethyl butyrate,butyrate,butyrate butyrate weak,between 0 ~ 25 ?,the amount of deformation in turn 6 to 15%,2 to 10%,1.5 to 3% and 0 to 2%.When the temperature is lower than 0 ?,pentyl butyrate has no swelling effect on the polyurethane,when the temperature is lower than-25 ?,ethyl butyrate,butyl butyrate and amyl butyrate have no swelling effect on the polyurethane.Both silicone oil and low molecular weight saturated fatty acid esters are excellent drilling media with excellent performance.The conductivity,thermal conductivity and the swelling of the sealing element of six kinds media test,obtained a good quantitative indicators,for the practical work of a guiding significance.From the test results,six kinds of media can be very good to meet the Antarctic ice core drilling and can be used for actual production. |
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