Fracturing tool having tubing isolation system and method

A method for formation treatment, comprising:

• running into a well casing on a tubing string a formation treatment tool having spaced straddle packer elements establishing an isolated casing zone within the well casing and having fluid supply passage and an injection port directing fluid flow from the fluid supply flow passage into the isolated casing annulus zone and an inlet port and fluid discharge flow passage receiving well treatment fluid from the isolated casing zone, the formation treatment tool having a dump valve controlling discharge of fluid from said discharge flow passage into the well casing and further having a tubing isolation valve controlling fluid communication between the tubing string and formation treatment tool;
• locating the formation treatment tool with said straddle packer elements positioned respectively above and below casing perforations of a selected casing interval;
• with said dump valve closed and said tubing isolation valve open, causing formation treatment by causing treatment fluid flow through said tubing string, tubing isolation valve, fluid supply passage and injection port into the isolated casing zone and through the casing perforations into the surrounding formation;
• after formation treatment opening the dump valve and discharging excess formation treatment fluid from the tubing string, fluid supply passage and isolated casing zone into the well casing below the formation treatment tool;
• closing the tubing isolation valve;
• equalizing fluid pressure across said straddle packer elements;
• and
• with the tubing string, conveying the formation treatment tool within the well casing.