Staged-Fracturing Completion Technology for the Ultra Deep-Hpht High Inclination Well in the Keshen Gas Field: a Case Study

Abstract

Abstract Keshen No. 10 gas reservoir has a large amount of resources, but the geological structure is complex, and three sets of faults are developed in the upper formation. Four vertical wells had been drilled in the last ten years, and only one well was drilled successfully. To develop the gas field, a high inclination well KSX was designed to avoid the faults. The final well depth is 7060m, maximum inclination was 76.6°, reservoir pressure was 103MPa, reservoir temperature was 154 °C, effective reservoir thickness was 115.5m, and the production casing was 7 3/4 inch with 5 inch liner. The staged-fracturing was designed to achieve a high production rate, and it was a major challenge for completion design and operation. To meet the requirement of staged fracturing, the different completion technology including bridge plug isolation, packer isolation and temporary plugging of perforated intervals were evaluated, and the combination of packer isolation and temporary plugging was finally chosen. Based on the casing program, 7 3/4 inch + 5 inch double packer combination was chosen preferably. Also, systematic analysis was conducted for the past failure case of double packer fracturing in the HPHT well, and it was clear that excessive axial force was the key factor of packer failure. Therefore, expansion joint was set between the packers to relieve the axial force on the packer during the fracturing. In addition, the soluble ball was chosen to open the sliding sleeve to conduct the next interval fracturing operation. During the completion operation, wellbore treatment, packer centralization and the other auxiliary measures were taken, completion string was successfully run in the expected depth, and the packer setting was also normal. During the fracturing operation, the target intervals were divided into two zones by both soluble ball and packers, the fiber temporary plugging of perforated intervals were completed in each zone, and the temporary pressure was up to 7 MPa. The total injection fluid volume 2562m3, total sand volume 159m3, maximum flow rate 6.55 m3/min, maximum pump pressure 118.5MPa. After fracturing operation, the production rate 740,000 m3/d was obtained with wellhead flow pressure 75MPa, and the rate was 2.6 times larger than the vertical well.