Deep Coring technology in Qingxi area of Yumen oilfield

Along with the further exploration and development of Qingxi area of Yumen Oilfield and the greater depth of drilling exploration,multiple wells with depth more than 5000 m are successively drilled,which requires more on deep coring technologies.In this paper,coring technology difficulties of deep well sections in the area are analyzed.Furthermore,research is conducted on selected types of coring bits and tools,match of coring parameters,optimization of drilling tool assembly,prevention of complicated coring process and accidents,and how to enhance coring recovery.Field application shows that the new technology can be used for enhancing coring recovery,simplifying coring process and reducing accidents.Coring of well sections of more than 5000m has been complicated with zero accident in the past three years.Coring recovery reaches 98.44% on average eliminating casing friction and formation breaking.