Study on the Method of Deep Lithologic Traps in Pinghu Formation of Xihu Sag: Taking the Kongnan Area as An Example

The main exploration target layer of Baochu Slope in Xihu Sag is a shallow-water sedimentary system with barrier coast in Pinghu Formation of the Middle and Upper Eocene. This set of strata is composed of a tidal-controlled delta sedimentary system and a lagoon/ tidal channel system that interacts to form a sedimentary sequence controlled by sea level rise and fall. And it is further complicated by contemporaneous faults, forming a series of traps which are vertically superimposed and laterally separated by faults. The target layer has characteristics of serious fault block, large burial depth and poor physical properties, which makes it difficult to characterize the reservoir. In this study, taking Pinghu Formation in the Kongnan area as an example, on the basis of basic data optimization and petrophysical analysis, deterministic pre-stack simultaneous inversion and changes in waveform structure characteristics are used to carry out reservoir research, and combined with drilling sedimentary sequence characteristics, lithologic traps are characterized by a combination of geological and geophysical methods. The technical goal of small average error between reservoir prediction and actual drilling thickness and reliable lithologic boundary is achieved.