Abstract

Crosswell reflection method is a high-resolution seismic imaging method that uses recordings between boreholes. The need for downhole sources is a restrictive factor in its application, for example, to time-lapse surveys. An alternative is to use surface sources in combination with seismic interferometry. Seismic interferometry (SI) could retrieve the reflection response at one of the boreholes as if from a source inside the other borehole. We investigate the applicability of SI for the retrieval of the reflection response between two boreholes using numerically modeled field data. We compare two SI approaches — crosscorrelation (CC) and multidimensional deconvolution (MDD). SI by MDD is less sensitive to underillumination from the source distribution, but requires inversion of the recordings at one of the receiver arrays from all the available sources. We find that the inversion problem is ill-posed, and propose to stabilize it using singular-value decomposition. The results show that the reflections from deep boundaries are retrieved very well using both the CC and MDD methods. Furthermore, the MDD results exhibit more realistic amplitudes than those from the CC method for downgoing reflections from shallow boundaries. We find that the results retrieved from the application of both methods to field data agree well with crosswell seismic-reflection data using borehole sources and with the logged P-wave velocity.

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