| Gas drilling technology is an effective technical measure to the efficient exploration and development of deep tight sandstone gas reservoir. However, High temperature,high pressure and high production are existed in the process of drilling in the deep tight sandstone gas reservoir. So it can’t nonsnubbing service and conventional tubing completion when gas production rate is too large. Therefore, well completion technology of drill pipe is presented. In this paper, literature research, theoretical analysis and numerical calculation are used to solve basic theory problems of drilling pipe completion in gas drilling. The main contents include:establishing high pressure natural gascompressibility factor model, wellbore temperature distribution under different workingconditions of gas drilling, the rule of gas flow in different working conditions of drillingpipe completion. The main results are as follows:(1) Through the calculation of DAK model, LXF model and Hall model, and thencomparing with StandingKatz gas compressibility factor. So the whole domain compression factor is formed which has taken the low pressure, medium pressure and high pressure flow mathematical model into consideration.(2) According to the theory of the first law of thermodynamics, thermodynamics and heat transfer theory, the mathematical model of temperature of working fluid in the drill column, column wall, annulus fluid in gas drilling is established. The numerical calculation results show that the temperature in the drill string and the annulus were increased as increase of depth. During the cycle, with the increase of the cycle time, annulus temperature increased, and as the growth of the time, the loop temperature changes more and more slowly.(3) In the domain of natural gas compressibility factor calculation model, circulation, and the loop based on the study of the wellbore temperature distribution model, according to the gas drilling is established. when drilling in reservoir, the gas into thewellbore, due to the huge difference of the formation pressure and bottom hole pressure, there will produce instantaneous pressure fluctuations in the bottom hole, make within the annulus pressure and pressure inside the drill string increase with increasing depth; during the completion test process, the gas density decreases which is in the wellbore annulus pressure and pressure inside the drill string with increasing depth and temperature, the pressure inside the wellbore increases with increasing depth, the gasvelocity decreases from the bottom to the wellhead.Through this research, the theoretical support of implementation and optimization are provided for drill pipe completion in gas drilling in deep tight sandstone gas reservoir. |
