Throttle Mechanism Of The Underground Research And Field Applications

Throttling in high-press natural gas well is a process which pressure and temperature will greatly drop. Throttling on ground need to use calefaction and heat preservation equipment to rise and keep the temperature of natural gas stream lest hydrate form. Throttling technique in downhole install choke at the suitable depth in tube to depress pressure and fully use terrestrial heat to heat gas stream. By doing so, the temperature of gas stream will higher than the temperature at which hydrate could form. This kind of new technique can depress the pressure in pipeline, control production rate, protect formation energy and reduce production cost.Contrast throttling on the ground with throttling in downhole On the base of throttling theory. Based on energy conservation theory and van der Waals' s mixed rule, a mathematical model considering phase equilibrium with Peng-Robinson equation is deduced to describe gas flow through choke and temperature drop through choke. This model can calculate the value of dropping of pressure and temperature cause by throttle.The mathematics model, based on mass, momentum, energy conservation and wellbore radius heat transmission, is derived to describe the profile of the flow pressure, temperature of the fluid in wellbore. The model allows for the kinetic energy of fluid, Joule-Thomson effect, structure of the well, the structure of oil string, different heat transfer medium in annular and the change, with the depth, of the physical properties of the formation. Nodal analysis is applied to combine the two models to calculate the distributing of pressure and temperature in the wellbore in which is install chock.Gas hydrate formation during exploitation and transportation is a well recognized operational hazard. It can impose serious accident such as the choke' s plugging, the gas well' s off production. In order to forecast the conditions of hydrate formation and choose corresponding steps to preventit, need to calculate some important parameters such as operation temperature and pressure before and after throttling, dosage of inhibitor, water content ratio and write suitable applying program.Develop throttle using in wellbore and compound equipment on ground and constitute technique guide line on the base of theoretic research. Applying test had been carry out in 12 wells of Chuanyu gas field and 5 wells of Changqing gas field. The test results prove that throttle in wellbore have the advantages of reasonable design, easy installation and fishing. So we can get the conclusion that throttling in wellborn has great applying foreground.