Division of Stratigraphy Sequences and Characteristics for Engineering Geology Investigation in Central South Area of Xihu Depression

The Central South Area of Xihu Depression is an area with abundant petroleum resources in East China Sea. The pre-drill-ing engineering geology investigation (site investigation) is an indispensable part among offshore petroleum E&P, which is crucial for stability of drilling platforms' foundation and safely of drilling process. Up to now, most of study is focused on individual drilling site. In individual drill site scale, the site's seafloor instable factors (geohazards) and soil's bearing capacity which affects platform foundation's stability are studied. However, study on the forming mechanism, sequence, distribution characteristics of geotechnical strata on regional scale is scare. Understanding the regional geotechnical stratigraphy sequences of a specific area is crucial for fol-lowing site investigation in this area. By stratigraphy sequences study using sub-bottom profiler data and study on regional marine geology and geotechnical drilling data, this paper analyzes the seismic facies, sedimentary environment, sedimentary facies, sedimen-tary sequences, and mechanical characteristics of Central South Area of Xihu Depression's geotechnical strata. After integrated study, this area's geotechnical strata are divided into five geotechnical sequences. This area's overall geotechnical sequences are established for the first time, and the soil layers are numbered. The result can be used as guideline for the following site investigation in this area.