Analysis of core blockage morphology and exploration of anti-blockage methods in trip round coring

Abstract:

During core drilling， it is common to encounter fractured or fragile formation. When the core enters the drill bit， due to the disappearance of confining pressure and the release of geostress， the core will break into blocks along the fractures. When entering the core tube， it forms a blockage form whcih hinders the entry of the subsequent core into the tube. In severe cases， the core will wear and consume each other， resulting in insufficient core recovery rate and the missing of formation data. Core blockage has become an important factor affecting core quality and drilling efficiency in core drilling. The state of core fragmentation and blockage morphology are complex， and it is difficult to grasp the mechanism of core blockage under the dynamic interference of drilling tools during drilling， making the core unblocking a major challenge in core drilling. By establishing a theoretical model of core blockage morphology， this paper analyzes the typical blockage morphology and variation patterns formed in the core tube after core fragmentation， suggestions on coring parameter specifications for formations prone to blocking are posed， and based on the typical core blockage patterns listed， the anti blockage methods are put foward and discussed.