Design And Calculation Of Hydrodynamic Parameters In Air Drilling

Air drilling is the one of main branches of underbalanced drilling. This technology use the air as the circulating media, it has a big distinction to the traditional drilling, such as the pressure distribution of the circulating system, the optimal designment of drilling parameters, and the flow characteristics of wellbore fluid. At present,we lack of systematic theory security and experimental study. In view of this, used the method of theory research conbining with experimental verification, researched into design and calculation of hydrodynamic parameters in air drilling, expected it can provide technical suppport to the further development and application of the air drilling.In the premise of analyzing the technical principle of air drilling, on the base of Angel mixed fluid theory, established the wellbore calculation model in vertical section, curved section, hold angle section. Analyzing the distribution charactristics of pressure, density and velocity both in annulus and in drillstring. According to formula of granular settlement velocity and granular starting critical velocity of the surface of cutting bed, established the criterion of minimum volumetric flow rate in vertical section and horizontal section respectively. Using the theory of similitude and conversion of pressure drop per unit, developed experimental equipment of the multifunctional annular cutting's taking, during the experimental course, we used different size of particles, observed the migration and destroyment of cutting bed, noted and calculated the critical annular velocity, and took the comparison with academic value and they tallied well with each other. At last, used language of Visual Basic to programm the software of calculation of hydrodynamic parameters in air drilling, and analyzed the calculation example.The result of the research perfected the basic theory of air drilling in a deep degree, and provided support both in theory and in technology for advancing the application of air drilling technology.