Feature Research Of Supercritical Carbon Dioxide Drilling Fluid

The paper launch on research work according to petroleum science and technology innovating fund for middle-young people"Bring cuttings feature research of supercritical carbon dioxide coiled tubing drilling fluid"and China University of Petroleum doctor innovating fund"Feature research of supercritical carbon dioxide drilling fluid". The regular patterns of density, viscosity, temperature and pressure in the borehole are researched thoroughly; The supercritical carbon dioxide drilling fluid circulating simulating experiment equipment is developed; By the simulating experiment equipment, bring cuttings law and carbon dioxide hydrate dissolution law are found. All these are base of the application of supercritical carbon dioxide drilling fluidCarbon dioxide fluid is a non-ideal gas with good compressibility, common use ideal gas equation isn't fit for caculation of density, viscosity, temperature, and pressure in borehole .By modifing P-R equation and Chung equation, equations of caculating density and viscosity in borehole are developed with error no more than 5%,the two equation have good applicability. Using diathermanous concept temperature transfer math model of layer/drill pipe/carbon dioxide fluid is setted up. By resolving the math model, temperature at any well depth of in drill pipe and annular can be calculated and get temperature profile. With these basic data, divide borehole into many small unit, the hydrostatic column pressure and friction pressure consume can be calculated in these small unit, then pressure and pressure consume can be calculated at any well depth and get pressure profile.The supercritical carbon dioxide drilling fluid circulating simulating experiment equipment was designed and setted up. As similarity principle, the experiment equipment was proved fully comparable with practice borehole. The experiment equipment can simulate operation behavior of supercritical carbon dioxide drilling fluid in depth of 2000 meters. Tempreture can be adjust and pressure can be controled easily in the experiment equipment. The visulization can be achieved in the high tempreture and high pressure condition(90℃,15MPa) The experiment equipment can accomplish bring cuttings, pressure consume and carbon dioxide hydrate preparation.By circulation simulating experiment equipment, the feature of bring cuttings was researched in different state and different inclined angle. Experiment found that carring cuttings is easy when the angle is between 0°~36°in supercritical state, carring cuttings become difficult when the angle get to 36°and carring cuttings is most difficult when the angle is between 54°~72°.it is different with our mind's eye that carring cuttings isn't most difficult in horizontal well. The least uphole velocity and minimal rate of flow for carring cuttings are found in different condition. The law of carring cuttings capability is increasing with pressure increasing and decreasing with temperature increasing.Solid separator in the experiment equipment is a side face revolver; this can mix carbon dioxide and water, when the temperature is no more than 10℃and pressure more than 5MPa carbon dioxide hydrate can be preparation. Stability of carbon dioxide hydrate in air gas was researched , the research demonstrate that carbon dioxide hydrate decompose speed is double than 2℃, 10℃, 20℃when surroundings temperature is more then 30℃. Carbon dioxide hydrate dissolving feature was researched in thermodynamics inhibitor like grain alcohol and inorganic salt calcium chloride and sodium chloride solution.. Carbon dioxide hydrate dissolving feature was research in dynamics inhibitor like SAS. The research of dissolving feature gives a settling way of dissolving carbon dioxide hydrate when jam occurs.