This chapter could be entitled ‘Wavelet Estimation and Well Tie’ or ‘Well tie and Wavelet Estimation’ and combined with Chap. 4 since there is a need to have a representative wavelet extracted from seismic data to attempt well ties, and vice versa. Wavelet estimation or extraction from seismic data is a crucial step in seismic inversion applications as echoed throughout Chaps. 1 – 5 in Volume 2. See, for example, Özdemir et al. (Norwegian Petroleum Society (NPF) Meeting on seismic processing and interpretation: the integrated approach. Extended abstracts, 1992a; 54th EAGE conference and exhibition, extended abstracts, pp 124–125, 1992b), Veeken and Silva (First Break 22:47–70, 2004) and (Delprat-Jannaud and Lailly, Geophysics 70:R1–R14, 2005) for the importance of estimated wavelets in seismic inversion applications. The basic requirement for successful seismic applications is that modelled or extracted wavelets are to be good representatives of the wavelets imbedded in seismic data over the zones of interest, i.e., over reservoir zones and/or prospects. Therefore, the near field wavelet measurements and even the sea bottom reflections in offshore seismic surveys cannot be directly used in seismic inversion since wavelets change as they propagate down to target reflectors and come back to near surface or surface receivers.