Annular Gas-solid Two-phase Flow Numerical Simulation Of Gas Drilling

The gas drilling has the obvious effect for avoiding complexities in the well bore. It can increase drilling rate clearly, decrease the quantities of the bits, improve the recovery ratio, and be benefit for the environmental protection. In the recently years, it is used widely at home and abroad. At present, gas drilling technology is developed rapidly. The researches and applications on this item have acquired lots of fruits at home. But it is far away from the international advanced level and application on a large scale district. The researches on working characteristics and technology parameters are still not mature in gas drilling.In order to improve the computation precision and level of the theory model in gas drilling, in this paper I try to use the computation fluid dynamics method to do, and explore a set of full-well full-scale hydraulics plan and analysis method based on the CFD, by which we can visualize the flow properties in the arbitrary position.By using the CFD theory, the 3D transient dynamic mode of gas-cuttings flow in the annular space in the gas drilling has been built, which is checked by the experiment data. The comparison indicates that the results computed by the mode are better fitful with the experiment data. The gas-cuttings flow in the annular space is been simulated by the mode in this paper, the results indicate that:1. The pressure decreases firstly then increasing by the gas velocity increasing. And the pressure in the concentric annular space is larger than the eccentric one. The average cutting fraction increases by the cutting diameter increasing in logarithm law. The sheer pressure of the part element increases by the velocity increasing in exponent sign, and the erosion of drilling pipes is more obvious.2. The cuttings will pass 4 phases which including channeling, slugging, bursting apart, getting together. The pressure drop is larger at the initial of pumping on, and decreases by time, increase by time after it reaching the minimum value.3. The gas-cuttings-water 3 phase flow has also been researched by the numerical simulation. The results open out the corruption cause of the drilling tools, namely, the formation water mainly distribute on the outer wall of drill tools and wall of the well.4. The pressure will become discontinuity at the transition section in the annular space.Based on the 3D transient dynamic mode of gas-cuttings flow in the annular space and the theory of CFD, the research of full-well full-scale hydraulics plan and analysis method has been explored, the results indicate that:1. The sheer pressure of the part element can be computed quantitatively by this method.2. The critical erosion velocity of the part element can be computed in this method with the criterion of API RP 14E. The results indicate that we can control the erosion by back pressure.3. The proper back pressure can be confirmed in this method, namely the proper back pressure should make sure the velocity in the annular space is between the minimum well...