TARIM is the largest basin abundant in carbonate reservoirs in China. Acid fracturing is the main technology for exploration and development in TARIM carbonate reservoirs, which featured with great depth (4500–7200m), high temperature (250–320F Degrees) and extreme heterogeneity due to fracture formation. If the azimuths of natural fractures and in-situ stress match the azimuth of fracture-and-cavern area from the well, the acid fracturing treatment would generate good effect in general; otherwise, the effect will be non-ideal.

A novel diversion acid fracturing (acidizing) technology, which combines fracture reorientation technology and fluid diversion technology, has been developed to solve the problem. When hydraulic fractures are initiated and extended in unfavorable direction, the fracture reorientation technology utilizing DCF (Degradable Cleaning Fluid, with great block efficiency and high compressive strength) can be adopted to temporarily block the fracture and ensure the hydraulic fracture would reorientate in advantageous direction. DCF is a mixture of TDF (temperature-degradable fibers), which would remain stable at 260 Degrees Fahrenheit while degrade thoroughly at 280 Degrees F, and soluble particles. By using visco-elastic surfactant based self-diversion acid, the fluid diversion technology could achieve deep penetration and efficient acid placement.

Well YM204 has no production before stimulation. The azimuth of maximum principal stress is about NE45 Degrees. FMI data shows that natural fractures in Ordovician carbonate formation are oriented at NW315-SE135 Degrees while there is a fracture-and-cavern area about 150m to the northeast of the wellbore according to the seismic lateral prediction. Thus, acid fracturing treatment combining fracture reorientation technology and fluid diversion technology was conducted in this well. Post-treatment evaluation indicates that the fracture-and-cavern area has been connected to the wellbore and the output remained over 100t/d of oil and 7000m3/d of gas.

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