Research On Drilling Risk Assessment During Drilling Process Based On ECD

Oil and gas drilling has characteristics of high risk and high investment,many kinds of risks,like kick,fracture,collapse and stick,take place unexpected because of complex layers and uncertainty of layer information.This is an important problem for drilling engineering when considering about safety and efficiency,so it's essential to do research on it.Since the risks,like kick,fracture,collapse and stick,has strong connection with ECD(equivalent circulating density),an ECD calculation method is made to calculate ECD more accurately which considered the temperature and pressure factors and it also can be used where it's environment contains seawater area or angle buildup area or horizontal area and its calibrate method is also made to calculate ECD more accurately based on drilling data.A calculation shows that the error of this method is under 0.33%and the difference between ECD and drilling fluid density can be as big as 0.075g/cm~3 which shows the necessity and importance of ECD.In case of drilling risk assessment problems while drilling,in this paper,the accidents mechanism,which is the theory of pressure balance,is analyzed and the method that use ECD to do research on risk assessment problem while drilling is put forward.After that,a drilling risk assessment method is brought forward to make risk assessment work on drilling risk problems while drilling process which is based on the ECD calculation method and pressure balance theory.Based on drilling data of BD area and Yinggehai area,drilling risk assessment works are made using those methods above.The result shows that this method has much effectiveness on the drilling risk assessment work for those drilling risk accidents which are caused of pressure unbalanced.This shows that the ECD based drilling risk assessment method works very well on risk assessment problems and it's reasonable to make risk assessment works using ECD.