Study On Size Calculation And Separation Of Four - Phase Separator For Underbalanced Drilling

Underbalanced drilling technology is an effective drilling process to find and protect the reservoir, but in the process of implementation of such drilling technology, the wellbore pressure is less than the formation pressure, so the formation fluids (oil, gas) will continue to spill back into the wellbore. It not only affects the drilling fluid properties, but also toxic and flammable gases will bring environmental and safety problem to us. To equip with a four-phase separator in underbalanced drilling site is very necessary.This paper focuses on making good use of four-phase separator and increasing the separation efficiency. To achieve what is mentioned above, optimizing dimensions of the four-phase separator calculation, the use of rectifier component within separator and modified design of solid removal system are done.First, to calculate the four-phase separator’s dimension, the grade efficiency model is applied. In this research, a general calculation method which considers the size of dispersed phase particles as a constant one is abandoned, Instead, a way that consider the size distribution(as lognormal distribution) of the dispersed phase is used. Among four phases, the separation between oil and water is the most difficult, so the size of separator will be determine mainly by oil-water phase separation, and then combined with the separation of liquid-solid, liquid-gas phase as a check.Secondly, in this study, how to use and select rectifier components in the separation zone in the four-phase separator is discussed. Rectifier components are added to the separator in order to improve the stability of the flow field within the separator to increase the separation efficiency. In this part of the study, by using Fluent6.3 flow field simulation software, five commonly used rectifier components (vertical plate, horizontal plate, orifice plate, the Swastika plate and cylindrical rectifier component) are analysed, then the impact on the flow field were compared. The results show that the Swastika plate rectifier component is more useful to shape the flow field of the four-phase separation.Finally, aim to design a excellent discharging system of rock debris, a new thought is put forward which applies metal screw pump as a part of the system. At the same time, a experiment table is designed to check the using effect of the system.The content of this research can improve the separation efficiency of the four-phase separator, which will play an important role in using and promotion of the four-phase separation.