Abstract:

： Aiming at the problems of reservoir density, ultra-deep, high temperature and high closure stress of the exploration well S1 in new area, we designed the modification scheme of compound high diversion acid fracturing. It was based on the fluid with better performance. The sand adding existed in the whole stage of prepad fluid and acid liquor. The proppant placement in all fractures（near wells and far wells）was realized. Meanwhile, acid is used to etch the main fracture and communicate with the surrounding reservoirs. So that the complex flow channel of ceramsite and acid etching across the whole crack scope formed. The evaluation conductivity in the lab showed that the conductivity of the compound channel form by ceramsite and acid etching increased by 40 %. The average embedded depth of high strength ceramsite proppant was only 85 μm. By the indoor fluid analysis and evaluation technology, the fracturing fluid system with the heat resistance of 180 ℃ was selected as prepad fluid to realized the effective long hydraulic fractures. The ground cross-linked acid system with the heat resistance of 165 ℃ was developed, and the optimum HCL concentration was 15 %, which meet the requirements of sand carrying and deep penetration. Then we optimized the proppant type and adding method to realized the effective support for all fractures. Well S1 successfully completed the fracturing by the equipment with the pressure resistant of 140 MPa. The highest displacement was 5.1 m ³/min and the highest pressure was 108.5 MPa, the cumulative sand adding was 78.6 t, and the fractured daily liquid output reached 72.9 t/d. The long-term conductivity of composite fractures remains at a high level.

Key words: ultra-deep well, high closure stress, fracture conductivity, composite fracturing, acid fracturing