Field and synthetic experiments for virtual source crosswell tomography in vertical wells: Perth Basin, Western Australia

A Novel Principle to Localize Scattered-wave Sensitivity Using Wave Interference and Its Adjoint

“…Although this novel principle can be useful in high-resolution monitoring in a wide variety of fields e.g., medical sciences, non-destructive material testing, civil engineering, in our synthetic test we consider geoscientific applications where monitoring is necessary while injecting fluid into the subsurface using boreholes. For example, recycled water is injected and stored in the aquifer for water resource management 34,35 , or treated water is injected in order to produce energy in geothermal fields or to store carbon dioxide in the subsurface . In all these applications, detecting subsurface changes due to the replacement of fluid and changes in the pore pressure is crucial 34,37,38 .…”

“…Monitoring using sensors located in the boreholes is generally performed for this purpose due to the sensitivity of downhole sensors to changes at the target depths [22][23][24] . Source points are located at the surface, as boreholes are generally inaccessible during the operation 35 . Therefore, we also consider the observation points located in boreholes and the source points at the surface (Fig.…”

Crosswell Nonlinear Seismic Waveform Inversion Without Downhole Sources and its Application to Time-lapse Monitoring

“…In other words, this approach effectively cancels the wave propagation between the surface source xS and RF including those due to near-surface heterogeneities. Note that the conventional seismic interferometric studies (Minato et al, 2011;Almalki et al, 2013) have the same characteristics. However, an important difference of the newly developed method compared to seismic interferometry is that here we do not perform additional least-squares inversion to estimate the Green's functions; the Green's functions retrieved by seismic interferometry are assumed perfect or the errors in the estimated Green's functions are additionally considered when they are used in the existing processing methods, e.g., traveltime tomography or conventional FWI.…”

“…There is similar approach proposed earlier which retrieves crosshole Green's function from VSP data through seismic interferometry by crosscorrelation or least-squares inversion (Minato et al, 2011). This approach enables estimating the wavefield as if the sources would be located in the borehole, and the retrieved crosshole wavefields are used for further processing, e.g., reflection imaging (Minato et al, 2011) and travel time tomography (Almalki et al, 2013). Contrary to these studies, in the present research we formulate a nonlinear waveform inversion using representation theory as basis for the forward modelling operator.…”

Time-Lapse Target-Oriented Crosswell Full Waveform Inversion without Downhole Sources

“…Minato et al (2011) successfully imaged the reflection structures between boreholes using retrieved crosswell seismic data. Almalki et al, (2013) applied this idea coupling traveltime tomography for characterizing water reservoirs system in acquirer storage and recovery.…”