The Research For Paleogene Sandbodies Distribution Principles In Bozhong Depression

By use of two-dimensional, three-dimensional seismic, drilling/logging and core, and theories and methods of sedimentology, sequence stratigraphy and seismic interpretation, the thesis discusses Paleogene structure, sequence stratigraphic framework, sedimentary facies, sedimentary facies and its controlling factors in Bohai Basin, Paleogene sandbodies distribution principles are summarized as well.The studies shows that, the structure of faulted-depression were developed in Paleogene of the Bohai Basin, and Kongdian and Shahejie formation have experienced faulted depression, Dongying formation has experienced depression. From lower to upper strata, six stratigraphic sequence of Paleogene, Kongdian and Sha-4, Sha-3, Sha-2, Sha-1, Dong-3 and Dong-2-lower, Dong-2-upper and Dong-1were developed. Basin has experienced the a large-scale expansion (Kongdian to Dong-2-lower) and atrophy (Dong-2-lower to Dong-1) , which constituted a complete stratigraphic cycle.When it comes to the types of sedimentary facies, Shahejie formation was mainly formed by coarse glutenite bodies that from nearly source area, and constituted by alluvial fans, subaqueous fans, fan deltas, braid river deltas, etc. Dong-3(Corresponding to lake transgression systems tract) was mainly formed by coarse glutenite bodies from the near source area, and also mainly constituted by alluvial fan, subaqueous fan, fan delta, braid river delta facies. The sedimentary facies were changed from Dong-2-lower to Dong-1(Corresponding to highstand systems tract), which are fine-grained meander river deltas and braid river deltas from far source area, and the glutenite bodies mainly develope along long axis of the depression.During the formation of the sedimentary system, level one (level one fault and Paleoclimate) controlling factor controls regional sedimentary background, uplifts and depressions were developed one after another;level Two (level two fault) controls the local ancient landscape, as well as transport routes and places of the sediments; level three (source area, slope breaks, ancient water system and the level change of the lake) mainly controls the sedimentary facies type, size as well as plane distribution and vertical changes of sand.The principles of sandbodies'distribution are, Shahejie formation was the coarse glutenite bodies from the near source area, and developed alluvial fan, subaqueous fan, fan delta and braid river delta vertically. Dongying formation mainly developed large fine-grained meander river delta from far source area, and local short-axis developed medium-sized braid river delta and fan delta sand bodies partly, which caused different layers. Horizontally, steep slope of depression developed crony-like coarse glutenite bodies, and mainly developed the dot fined-grained glutenite bodies between gentle slopes and uplifts with obvious characteristics of zones. Provenance in different periods had the characteristics of inheritance and evolution, Kongdian formation and Dong-3 were mainly constituted by coarse glutenite bodies from the near source area, fine-grained glutenite bodies from far source area developed from lower Dong-2 to Dong-1. Both of the formations have their own source of inheritance, and based on the early development and migration, but there were certain changes among sedimentary facies type, location and deposition of sand scale in different periods.