Geochemical-Sequence Stratigraphy and Its Application Prospects in Lake Basins

As a useful approach for hydrocarbon exploration, the sequence stratigraphy has been commonly accepted. The concepts of sequence and parasequence provide a state-of-the-artframework for studying the distribution and characters of depositional system, and analyzing the occurrence, distribution, characteristics of source, reservoir and seal-play elements. The newly-developed geochemical-sequence stratigraphy focuses mainly on the occurrence, distribution and characters of source rocks and reservoir hydrocarbons within a chronostratigraphic framework. Integrated with sequence stratigraphy, geochemistry can be used to study the source rock potential within a sequence stratigraphic framework and to describe the characteristics of hydrocarbons accumulated in reservoirs, which were predicted by way of sequence stratigraphy. The concept of geochemical-sequence stratigraphy was proposed by Peters et al. (2000). Constructing a reliable sequence stratigraphic framework is the basis of geochemical-sequence stratigraphic study although it is not the main goal. High-resolution biomarker analysis is critical to the construction of a geochemical-sequence stratigraphic model. The geochemical-stratigraphic study involves mainly: (1) the distribution and geochemical characteristics of source rocks within a sequence chronostratigraphic framework; (2) the geochemical features of source rocks with relative sea (lake)-level change; (3) to predict if these reservoirs bear hydrocarbons and their geochemical features; (4) to be used to construct the time-stratigraphic framework. This paper also summarizes the lake basin types, and introduces their facies associations, source potential and organic geochemical features. At the end, the authors offer some suggestions about how to carry out geochemical-sequence stratigraphic study in lacustrine strata.