Borehole deviation surveys are necessary for hydraulic fracture monitoring

Leo Eisner & Petr Bulant


Not performing accurate borehole deviation surveys for hydraulic fracture monitoring (HFM) and neglecting the effects of the borehole trajectory results in significant errors in the calculated fracture azimuth and other parameters. For common HFM geometries, a 5° deviation uncertainty of monitoring or treatment wells can cause more than 40° uncertainty in inverted fracture azimuths. Furthermore, if the positions of injection point and receiver array are not known accurately and the velocity model is artificially adjusted to locate fracture on an assumed injection point, several milliseconds discrepancy between measured and modelled P-to-S-wave travel-times may appear at utmost receivers of the receiver array. This travel-time discrepancy may then be misinterpreted as VTI anisotropy. In the case of HFM, the uncertainty of the relative positions between the monitoring and treatment wells can have a cumulative, non-linear effect on inverted fracture parameters.

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In: Seismic Waves in Complex 3-D Structures, Report 16, pp. 197-201, Dep. Geophys., Charles Univ., Prague, 2006.
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