Packer-Induced Stresses During Hydraulic Well Fracturing

Well bore stresses induced by inflatable packers during hydraulic fracturing operations are investigated. The geologic formation is modeled as an unbounded homogeneous isotropic linear elastic solid containing an infinitely long circular cavity, while the packer is modeled as a semi-infinite thin-walled circular cylindrical shell. For given packer properties, these induced stresses are shown to depend on the difference between packer pressure and fracturing pressure and can become significant. Typical numerical results are obtained and presented graphically. Analytical approximations for the maximum values of these stresses are also presented. While these effects are of no importance in the usual application of hydraulic fracturing to enhance oil and gas recovery, they are crucial in attempts to estimate in-situ stresses from hydraulic fracturing pressure data.