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Study on Intercalation of Shallow Water Delta by Integration of Logging and Seismic Data


Abstract: Intercalation is one of the main reasons for reservoir heterogeneity and plays an important role in the waterflooding and distribution remaining oil. In consideration of sparse well spacing and imperfection of well pattern in offshore oilfield, we carried out detailed analysis on shallow water delta by integration of logging and seismic data to clarify the types, well-to-seismic responses and spatial distribution of intercalations. The results show that distributary channels are widely distributed during the period of Nml Formation. Muddy intercalation is the main type of intercalations, characterized by mudstone and siltstone with low value of GR and RT. Controlled by sedimentation, the formation of muddy intercalations are of three origins: (1) mud deposits during the intermission of flood period (flood plain); (2) fine-grained deposits during the weakening period of flow (interdistributary bay deposits); (3) migration of distributary channels (architectural boundary). Integrated analysis shows that seismic waveform, coupled with instantaneous frequency and minimum amplitude are in well response to the development of intercalations as the reservoir thickness ranges from ?/4 to ?/2. The intercalations with thickness over 4 m show asymmetric waveforms and a reduction of instantaneous frequency and minimum amplitude, whereas unapparent change in instantaneous frequency and minimum amplitude but asymmetric waveform with thickness less than 4 m. Accordingly, by attribute computation and calibration of waveform and logging, the intercalations were quantitatively delineated and the 3D model was established ultimately. This technique helps to reveal the internal structure of distributary channel, improve the precision of numerical simulation, as well as provide geological basis for enhancing oil recovery. Key words:Shallow water delta; Intercalation; Spatial distribution; Stratigraphic slice; Seismic waveform