| Under-balanced drilling is a new drilling technology developed by 1990's, which has adapted the development of exploration and exploitation of petroleum industry at present. With many advantages in technology, it grows very soon and has very broad applying prospect.Under-balanced drilling is an irreversible and only one-time course, whether it can get the success depends on many controllable and uncontrollable factors. What are the most important technologies are how to optimize the controllable factors, make the under-balanced drilling obtain the expected result safely and successfully, design the proper fluid parameters of under-balanced drilling, and the safe and reliable control system of well-head and surface.At present, the theories of design and calculating methods of under-balanced drilling parameters are in great numbers interior of country, but they are common complicated and the methods of calculation are very complex. And this requires us research systematically into the fluid-dynamic of under-balanced drilling and form a series of simple > accurate and systematic theories of design , calculating and controlling of the parameters of fluid-dynamic about under-balanced drilling.On the base of systematically analysis of the theory and methods of parameters design of domestic and foreign UBD fluid dynamic, this paper analyzed and estimated the calculating model and methods of UBD fluid-dynamic parameters of gas, foam and aetated fluid of Bo Yun Guo. Emphasized on systematic research of surge under-ground fluid enter the wellbore and the calculate theory and design method of UBD realizing, the article set up a model of surge under-ground fluid and the equation calculation, design and control of multiphase fluid-dynamic parameters in annulus space, and also made a software of how to calculate the parameters.During the UBD experiment (gas, Aetated) on oil-field, some susceptible problems in the course of UBD have been theoretically analyzed. |
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