Well-to-seismic tie

Tying seismic data to the available well control is a crucial step in seismic interpretation, an important component of seismic reservoir characterization. The subsurface reflection coefficient series can be calculated from the impedance well log curves, but to generate a 1D synthetic seismogram, the reflectivity must be convolved with a wavelet. For this purpose, the wavelet can be extracted from the seismic data statistically or deterministically by comparing it with the seismic trace at the location of the well. This way the generated synthetic seismogram can be correlated with the seismic data. Usually a single wavelet is extracted in a time window for the generation of the synthetic seismogram under the assumption of stationarity of seismic data. Such assumptions become invalid where zone of interest (ZOI) extents over a large time window especially for multi stacked unconventional plays. In these dataset, the idea of extraction of a single average seismic wavelet over ZOI and using that in the well-to-seismic tie leads to a poor correlation between synthetic and real seismic data. Therefore, it is required to consider the temporal as well as spatial variation of wavelets embedded in the seismic data as shown below where a dataset from the Delaware basin is cited. For this data set, notice that the assumption of stationarity of seismic data is not valid within ZOI as wavelet was changing temporally and spatially and if such variation is not considered in well-tie analysis or inversion, we will be compromising with out results.

A dataset from the Delaware Basin where zone of interest (Bone Spring to Mississippian) extents over 2.5 seconds. In this dataset, the idea of extraction of a single average seismic wavelet over that window and using that in the well-to-seismic tie leads to a poor correlation between synthetic and real seismic data. (Adapted from Chopra et al., 2019)

References

• Chopra, S., R. K. Sharma, and J. Keay, 2019, Efforts at effective reservoir characterization of Bone Spring and Wolfcamp formations in the Delaware Basin – a case study, presented at SEG Convention, held at San Antonio, in September.