Depositon And Stratigraphic Sequence Development And Evolution Of Upper Devonian Series-Carboniferous Of The Tabei Uplift South Slope And Potential Reservior Prediction

Tarim basin is a typical large scale folding basin, which located in the west of China. The basin experienced several structural movements, which caused palaeography changed, and several unconformities formed and combined together. Wildly distributed stratigraphic overlap-offlap belt and facies change belt controlled lithostratigraphic porosity trap’s formation and reformation.Upper Devonian series and Carboniferous is the main exploration target of the south slope of Tabei uplift. As exploration becomes more and more difficult, strucactural traps decreased and exploration difficulty increased, so more accurate stratigraphic sequence and sedimentary systems research are needed urgently so as to solve a series of problems(such as weak marine facies stratigraphy research, strata comparison difficulty, and different sedimentary systems views), which all restricts further oil-gas exporation.Under the guiding of sequence stratigraphy and modern sedimentology theory, using bore-seismic stratigraphy boundaries tracing, the paper set up isochronal sequence framework of upper Devonian series and Carboniferous system of the south slope of Tabei uplift, sloved the problem of strata comparison, set up two sequence models of Donghetang-Bachu formation, which provided support for sand body prediction. Upper Devonian series and Carboniferous system of the research area can be divided into 4 3rd-order sequences and 7 system tracts. Donghetang formation and Bachu formation belongs to different 3rd-order sequences and deposited successively. Bachu formation is made up of 3 lithology members. Although there is big difference between different district, it can be compared with Tazhong uplift in stratipraphic framework.Late Devonian to Carboniferous, several unconformities formed successively, several provenances provided sediments, and palaeogeomorphology background was complicated, so different opinions of sedimentary systems appeared. On the basis of the analysis of core, log and seismic data, 5 kinds of sedimentary systems were recognized, namely beach, tidal flat-lagoon, delta, fan delta and carbonate platform. The paper also studied Plane distribution and vertical evolution of the sedimentary systems, and set up two depositional models of Donghetang formation and Bachu formation.By seismic refection and remnant thickness analysis, provenances of Donghetang and Bachu formation were confirmed, namely Yingmaili low bulge and so on . Depositional palaeogeomorphology units could be divided into high uplift, platform, slope, depression and low massif. During late Devonian to Carboniferous, sea level underwent 3 fluctuations, which was affected by eustasy. Plane distribution and vertical evolution of late Devonian to Carboniferous sedimentary systems were affected by provenance, paleogeomorphology and sea level fluctuation.The characteristics of source rock- reservoir-cap rock assemblage and typical oil traps were analyzed. Combined with sedimentary systems distribution and palaeogeomorphology reconstruction, potential districts for further exploration of Donghetang formation and Bachu formation were pointed out, namely south area of Caohu sag, Saike structure and Hal2 borefild.