The Lacustrine Sequence Stratigraphy and the Saline Deposits Origin in Biyang Basin,China

Biyang depression is one representative of small half graben saline lacustrine basin with abundant oil in China, it is famous for stratigraphic reservoirs and saline deposits development, saline deposits are not only reservoirs but also one kind of important source rock, so it is significant to study the saline deposits distribution within sequence stratigraphy framework and its origin in order to understand the petroleum system elements of this basin. On the basis of comprehensive analysis of outcrop, well logs, seismic data, and geochemical data, sequence stratigraphy is studied in detail for the first time, which reveals the basin is the typical non-gradient change faulted basin. No large incised valley delivery system develops in the ramp slope, its main sedimentary systems and lowstand sand bodies are mainly controlled by the transitional zone between erosion and deposition, this transitional zone is the hinge belt of the strata tilting. Potential stratigraphic traps mainly distributed in the lowstand systems tract around the saline deposits. The high frequency sequence is applied to the analysis of saline deposits in deep lake setting and shallow lake environment setting. High resolution sequence stratigraphic framework correlation shows that the distribution of the saline deposits is mainly located in the highstand systems tract and closely related to the progradation extent of the different deltas(fan deltas). The seismic attributes along the maximum flooding surface is employed to identify the geomorphology of sedimentary systems and characterize the spatial distribution among different deltas, fan deltas and saline lake, which illustrates the junction of Highstand sand dispersal systems from the steep slope and that from ramp slope is one of the main mechanism for the enclosed saline lake and its deposits.