An Analysis On Sedimentary System In Shahejie Formation Of Paleogene At The Gentle Slope Of The North Slope Of Chengning Uplift

The north slope of Chengning Uplift is located in the gentle slope of QikouDepression Basin in the southeast of Huanghua Depression. There are fourextensional normal faults with the NNW dip shift, named the South of YangerzhuangFault, Zhaobei- Yangerzhuang Fault, Zhangdong-Hai4 Fault and Qidong Fault, whichconstitute the Chengbei fault-step belt framework falling downwards step by step. Asdemonstrated by many years' petroleum exploration, there has abundant of petroleumresources in Shahejie Formation of Paleogene. However, the degree of exploration isrelative lower. It isn't adequately realized the particularity and controlling-factorscaused by the sequences and depositional systems of the gentle slope belt, from theearlier researches and works.Aimed at the above research meaning and problems, in this thesis, It conceivingthe north gentle slope belt of Chengning Uplift as erea, and Shahejie Formation assubject, uses the theories and methods of Sedimentary Geology and Continentalsequence stratigraphy to analyse its isochronal stratigraphic framework, the types ofdepositional systems, the evolution of paleo-provenances and paleo-river systems,reveal the space-distributing rules of depositional systems and sandstone bodies, andoffer important basic geological datas for the exploration of sandstone bodies subtlereservoirs in Shahejie Formation of Paleogene of this erea.According to the characters of gentle slope palaeogeomorphology, stratigraphicsequences are controlled by architecture, climate, deposited accommodation,elevation of lake level, and so on. On vertical and plane, layers distributediscontinuously, sequences develop uncompletely and the bounding surfaces are clear.Using and realizing the different bounding surfaces on seismic profile and log curve,it divides Paleogene into two second-order sequence, and divides Shahejie Formationinto six third-order sequence. It uses third-order sequence as cell to constitute theregion sequence stratigraphic framework.Utilizating the datas of drilling core, well log, seismic and interior testinganalysis, based on sedimentary facies indicator analysis, and also according to thecharacters of rock association, sedimentary structure, section structure andevolutionary series, it identifies three type of depositional systems, including delta,lakes and gravity current, and analyses sedimentary facies, subfacies and microfaciesdetailedly. Utilizating the components of gravel and sandstone, heavy minerals and sandstone bodies dispersion system to analyse paleo-provenances and paleo-riversystems, it identifies that there were three secondary-paleo-provenances andpaleo-river systems in this area, which were divided into western, middle and easternriver system (corresponding to three secondary-paleo-provenances) by the boundariesof modern coastline and two-meter-deep waterline.On basis of the above research, it analyses the distributions on space andevolution rules on time of the depositional systems for the six third-order sequencesfrom SQ1 to SQ6. On space, from southern Chengning Uplift to northern QikouDepression, the depositional systems were erosed in the slope zone, developed braidriver delta plain in outer zone, braid river delta front and sand-bar in middle zone, andbraid river delta front and turbidite fan in inner zone. It constitutes the gentle slopedepositional system pattern of Shahejie Formation in Chengbei fault-step belt, whichis built up by delta, lake and gravity current. At last, it takes three hydrocarbon trapsfor prediction, which is built by lithologic trap and lithologic-fault trap including deltasandstone in member three of shahejie formation, sand-bar sandstone in member two,and delta and carbonate sandstone in member one.