Lithologic reservoirs, characterized by the subtle location, small dimension and complex depositional architecture, have attracted much attention as a focus issue in petroleum exploration and development. Conventional structure and deposition interpretations based on seismic and logging data are very beneficial to the distribution forecast and formation analysis of lithologic reservoirs. But they are not enough to guide the remaining oil prediction of these reservoirs in the late stage of oil and gas development. Through years of study, a new fine characterization method on lithologic reservoirs is proposed. And four key techniques are involved, including the establishment of the depositional isochronous stratigraphic framework, dynamic analysis of the reservoir depositional evolution, fine anatomization of the reservoir architecture and comprehensive prediction of the remaining oil. This method has been successfully applied to a complex lithologic reservoir located at the XJ 24-1 Oilfield in the northern Pearl River Mouth Basin and verified by the later drilling results.
High-quality seismic imaging results are the basis of lithologic reservoir characterization. Since the NMO and post-stack time migration were proposed respectively by Dix (1955) and Claerbout (1972), seismic imaging theory has been developed from NMO + DMO + post-stack migration, pre-stack time migration (PSTM), pre-stack depth migration (PSDM), anisotropic medium PSDM to the orthogonal crystal medium PSDM. The lateral resolution of seismic data is gradually improved.
Sequence stratigraphy and Seismic sedimentology are the major theories to study the stratigraphic framework and depositional evolution in a depression or an oilfield. Vail (1987) proposed the concept of sequence stratigraphy based on a passive continental margin sedimentary model, and established sequence stratigraphy theory that is based on seismic, logging and geological outcrop data. Furthermore, this theory was improved constantly and applied to hydrocarbon exploration of almost all kinds of basins (Galloway, 1989; Posamentier et al., 1992; Embry, 1993). Seismic sedimentology is the use of seismic data to study sedimentary rocks and their forming processes (Zeng et al., 1998). It is a new marginal interdisciplinary subject following sequence stratigraphy (Schlager, 2000) and bring new understandings to the limitation of the seismic resolution in space (Ling et al., 2007). Seismic interpretation based on sequence stratigraphy and seismic sedimentology could reduce the exploration risk of lithologic reservoirs. However, it is difficult to study the architecture and heterogeneity of lithologic reservoirs.