Reason Analysis on Internal Pressure Decrease of A Annulus Space at One Well

The reason of internal pressure decrease of A annulus space at one well was investigated. It was considered that production casing string leakage resulted in internal pressure decrease of A annulus space and internal pressure increase of B annulus space by the tests of filling and releasing internal pressure of A and B annulus space. It was thought that casing failure at the coupling position led to casing leakage and pipe sticking per analyzing on stuck point and casing string.