Abstract:

The Paleozoic buried hills which have favourable reservoir forming conditions in basement of the rifted basins in east China are important areas for hydrocarbon reservoirs exploration. Reservoir physical properties and hydrocarbon accumulation are different in the plane and the vertical for the great thickness of the sedimentary formation, varieties of rock types, complex residual formation and different tectonic stresses of the Paleozoic basement of Chengdao oilfield in Bohai Bay basin. Therefore, study of the law of residual formation is a key of oil and gas exploration of the Paleozoic. Residual formation has been studied shallowly before based on drilling results and seismic interpretation, and analysis of the genetic development is lacked. In this study, stratigraphic sequence and development law of residual formation are studied based on well and seismic analysis. And some results and understandings are achieved as follows: Firstly, Cambrian, LowerMiddle Ordovician, MiddleUpper Carboniferous and Permian strata are developed from the bottom up in the study area. Secondly, from north to south and from east to west, the residual Palaeozoic strata today change from high to low. And the residual Palaeozoic strata are less on lower location of the buried hill structural zone because of the inversion structures. Finally, main weather denudation stages are analyzed and the structural features of geological history are speculated from the stratigraphic distribution characteristics. And the regional tectonic evolution process is further proved. This study provides a reference for research of the stratigraphic features and tectonic evolution of basement of the Paleozoic in the superposed basin in east China.

Key words: superimposed basin, Chengdao oilfield, buried hill, Paleozoic, stratigraphic characteristics, tectonic significance, tectonic evolution