Modelling of seismic response from hydrocarbon bearing north sea chalk

In chalk exploration and development seismic inversion has become a standard tool for porosity prediction whereas AVO processing so far has not been widely applied to seismic data in relation to chalk fields. In general AVO effects from different fluid saturations are expected to be very subtle and consequently the applicability of AVO methods for fluid detection in chalk fields have been questioned. In this paper forward modelling has been used to simulate seismic response. Modelling has been performed with seismic modelling software developed by Norsk Hydro. Modelling tools to include compaction/de-compaction and fluid saturation effects in chalk have been developed by GEUS. The modelling has been applied to a profile connecting the Dan and Halfdan chalk fields (Figure 1). Hydrocarbons are located in Danian and Maastrictian chalks (e.g. Jacobsen et al, 1999; Albrechtsen et al, 2001). The pelagic, deep water origin of the chalk supports the assumption of lateral homogeneity. Comprehensive studies of porosity-depth relationships and rock physic methods have been included to model changes in acoustic properties away from well sites. The EQR method has been used for fluid saturation modelling.