Study and Application of High-effcient Multi-stage Fracturing with Fixed String in Vertical Well in Daqing Oilfeld

The conventional multi-stage fracturing technique cannot meet the demand of exquisite separating layer stimulation and increasing sand-adding scale. The execution of multi-trip string, however, may result in excessive workloads, reservoir damage, long time consuming, low effciency as well as high cost. Besides, the possession of crews and equipments are not geared up to the requirements. Therefore, the author conducted a research on the technology of high-effcient multi-stage fracturing with fxed string which can be applied in the circumstance of 120℃, 60 MPa, developed some associated fracturing tools including slide-sleeve pressure-transmitting sand blast packer, large drift diameter hydraulic anchor, innovated the integrated design of small range slide-sleeve, pressure-transmitting and packer, resolved some diffcult problems such as string block and anti-block, design strength and security as well as reliability etc. It also makes it possible that 10 intervals can be treated in one trip without strings running up and down instead of the previous 4 intervals. This technology has been applied in 683 wells with success ratio at 99.4%, is also useful to the effective reserve-producing from the poor and thin reservoir in the peripheral area of Daqing Oilfeld and to the fne potential tapping with water flooding in Changyuan area.