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Abstract

Apparatus and methods are disclosed for monitoring in real time the propagation of a fracture through a rock formation traversed by a well borehole, during hydraulic fracturing processes. The inventive system permits continuous measurement of the movement of gamma-emitting tracers in the fracturing fluid, while the fluid is pumped into the formation. The tracer isotopes pass by a downhole neutron source, which activates the tracer isotope nuclei, causing them to emit characteristic gamma radiation after the fracturing fluid passes through perforated production casing into the induced formation fracture. Multiple sodium-iodide scintillometer detectors, arrayed on the logging tool above and below the neutron source, are calibrated to detect the characteristic energy spectra emitted from the activated radioactive tracer isotopes in the fractured formation through the formation rock and the steel production casing and tubing. The detectors pass data to a surface computer system by wire-line logging cable, allowing graphical display of fracture propagation at the wellsite while the fracturing treatment proceeds. The system allows the operator to control fracture propagation in response to present conditions, preventing 'out of zone' fracturing, which can ruin a well. The system helps operators to maximize production while preventing economic waste.

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First Claim