Development and application of full bore acid fracturing string in Tuofutai Region of Tahe Oilfield

The packers for conventional acid fracturing string and hydraulic anchors used in Tuofutai Region of Tahe Oilfield are not match the internal diameter of ?88.9 mm tubing, leading to increase in friction and affecting the effectiveness of acid fracturing. For this reason, the research on full bore acid fracturing string was conducted and the Y241-146 full bore packer was developed. On condition that the external diameter of the packer and its setting effect are not affected, the internal diameter of central tube of the packer is increased from 62 mm to 76 mm, and the internal diameter of hydraulic anchor increased from 62 mm to 76 mm. The acid fracturing strings have a diameter of 76 mm as a whole; the key components are 42Cr high-strength material; the rubber sleeve material is changed from nitrile rubber to hydrogenated nitrile rubber, which effectively improves the tension and compression strengths, temperature resistance and sealing performance of the tool. It has been used in 26 wells in Tuofutai Region of Tahe Oilfield, and the string setting, checking, acid fracturing and unsetting were all successfully conducted in one time; the acid fracturing friction was reduced by 4–5 MPa in average in single well. The tests show that the acid fracturing string can meet the requirement of site technology.