OCCURRENCE CHARACTERISTICS AND SIGNIFICANCE OF CARBONIFEROUS AND PERMIAN IN THE SHENGLI OIL FIELD, THE BOHAI BAY BASIN

Carboniferous and Permian strata in the east of Jiyang and Linqing Depressions(the Shengli Oil Field) of the Bohai Bay Basin are zoned and blocked from east to west and zoned from north to south,influenced by multi-compressions during the Indosinian-Yanshanian stage and extensions during the Himalayan stage.Compression uplifts during the Indosinian-Yanshanian stage are strong in the northeast and weak in the southwest.Extensional uplifts during the Himalayan stage are large in the southeast and small in the northwest.Various "blocks" of different sizes,shapes and depths are formed.Blocks in the northeast are small and faulted while those in the southwest are big and jointed.In addition,superimposition of the two stages of tectonic movements has changed Carboniferous and Permian residual block bodies into "wedge shape".Multi-compressions,uplifts and erosions during the Indosinian-Yanshanian stage and the following tectonic reverse result in the gradually thinning trend in the east and west of blocks.Strong extensions during the Himalayan stage make blocks deep in the north and shallow in the south.Blocks are thinning in the deep northern flank like wedges and gradually uplifting in the south.The above-mentioned characteristics have relatively great impact on late hydrocarbon generation(mainly secondary hydrocarbon generation) and accumulation in Carboniferous and Permian in the Shengli Oil Field,the Bohai Bay Basin.