Research and application of gum(borate gelling fracturing fluid system) for abnormal high temperature use

Proper fracturing fluid system is critical to successful deep well (more than 5000m deep) fracturing with abnormal high temperature (higher than 180 ℃). However, conventional fracturing fluid systems now used in China only adapt to the strata with temperature lower than 150 ℃. Lab experiment is conducted to modify two major additives that affect the property of ultra-high temperature fracturing fluid---thickener and crosslinker. By strictly controlling the reaction conditions, GHPG gum/borate gelling thickner with low residue and high viscosity for ultra-high temperature use and BA1-21 delayed crosslinker for ultra-high temperature use are obtained, and a fracturing fluid system resistant to the temperature higher than 190 ℃ is developed successfully. The performance of modified gum/borate gell for ultra-high temperature use is evaluated, the delayed crosslinking performance and heat/shearing resistance of crosslinker of the fracturing fluid system for ultra-high temperature use is also evaluated. Eight days after fracturing and modification in ZG63 well, flow back rate of fracturing fluid attains to 74.9%, with the average being 6000 m3. The reservoir is modified and recognized. This new breakthrough is valuable for deep reservoir fracturing with ultra-high temperature in China.