Study on wellbore collapse pressure and instability area around wellbore in broken formation
The development of stratigraphic fractures has a certain impact on the collapse pressure and the distribution azimuth and depth of the instability area around the wellbore.However,conventional wellbore stability analysis methods treat the formation as an isotropic medium without considering the fracture characteristics of the broken formation.In order to study the variation laws of wellbore collapse pressure and instability area around the wellbore in broken formation,this paper combines the modified MC strength criterion and the fracture surface strength criterion under triaxial stress to establish a prediction model for wellbore collapse pressure and instability area around the wellbore in broken formation.The effects of fracture number and wellbore trajectory on wellbore stability are studied.The study found that under triaxial stress,the collapse depth of the wellbore in broken formation is mainly controlled by the fracture dip angle,which is unrelated to the fracture tendency,while the collapse azimuth of the wellbore is unrelated to the fracture dip angle,and only changes with the change of the fracture tendency;The collapse of the wellbore is mainly controlled by a fracture with special occurrence.The relative angle between the axial direction of the borehole and the fracture surface can be adjusted to reduce or control the degree of wellbore instability.
broken formationcollapse pressureinstability area around wellborestrength criterionnumber of fractures
万方数据
维普
