Application of submerged pressure maintaining sealed coring techniques to Well Xushen-12

The pressure maintaining coring technique is a coring technique that can keep or be close to formation pressure.It is of great significance to obtain complete and exact formation data by applying pressure maintaining tools and sealing fluid,realizing the differential motion of outer cylinders at the bottom of wells,closing the ball valves of inner cylinders,sealing cores in inner cylinders,preventing oil-gas-water losses from cores during the process of coring,and then obtaining the cores of original formation pressure.In 2006,a new type of pressure maintaining coring tool,BYM-Ⅲ,suitable for Daqing deep layers,is developed and successfully applied to the deep layers of Well Xushen-12.In view of the characteristics of deep volcanic strata,the operation of one pressure core barrel is successfully completed,based on using impregnated diamond coring bits,selecting assembly materials of ball valves,increasing protection structures for closing ball valves,improving sealing materials and forms,applying sealing fluid resisting high temperature,enhancing pressure-filled technology,employing liquid nitrogen refrigeration technology,and optimizing drilling parameters.This provides abundant basic data and interpretation basis for having correct cognition of the geological conditions of the area,calculating gas reserves,and making reasonable development plans.