Reservoir Characteristics And Quality Controlling Factors Of Es4x-Ek On The South Slope In Dongying Depression

Aiming at the sedimentary strata mainly consisted by Paleogene Es4x-Ek continental red beds on the south slope in Dongying depression,this dissertation has,based on the data of core,thin slices as well as analytical exmination,focused on the characteristics about petrology and reservoir space of the reservoir in target red beds seriously,analysed the variety of reservoir diagenesis on different step-fault zones meticulously,defined the reservoir conprehensive sequence on both diagenetic and pore evolution sternly,and discussed quality controlling factors of red bed reservoir finanly,in order to provide geological evidence for next exploration in the research district.Because of the great distinctions in lithofacies and burial process of the target layer,which lead to extreme heterogeneity of the reservoir,on different sedimentary-structural units of the research district,this dissertaion should divide different procenance areas(A area western south slope,B area eastern south slope,C area northwest provenanace and D area central shore lake),and tectonic belts((1)basin-margnial erosion belt,(2)return erosion belt,(3)sag slope belt and(4)depression uplift belt),to take a comparative reaserch on the distinctions.The results indicate that: sandstones of red beds are mostly lithic arkose with a lower level of whole composition maturity.Although sandsotne detritus are basically composed of igneous rocks fragments in different provenance areas,there are a few limestone fragments discovered in area B and C,while proportion of siliceous fragments increases in area D,to influence burial diagenetic sequence.The comparison of physical property has proven that lithofacies and burial depth make a particularly prominent impact on reservoir’s porosity and permeability,with the results suggesting that conglomeratic sandstones shallowly buried from alluvial-fan on basinmargnial erosion belt and delta on return erosion belt are the best,while fine sandstones middle-deep buried from delta and beach-bar on slope belt come second.The space types of effective reservoir,divided into three categories while nine sub categories,is dominated by secondary pores and supplemented by residual primary pores and fractures.As for the diagenetic sequence of reservoir,erosion belts often suffer weak compaction,with some getting tight due to the early cementation,and dissolution cased by atmospheric freshwater and organic acid.While slope belt and depression uplifted belt sustain stronger compaction as the increase of depth,in which dissolution by organic acid from both inner target layer and external sources can exist and late cementation may develop.The diagenetic sequences at different sedimentary-structural units are restored through multi-history coupling,the contrast sections under the control of complex fluids in different diagenetic stages are displayed,and the sources of calc-alkaline fluids and acid fluids are summarized.Amony them,the acid-alkali diagenetic fluids acting as a key to effect physical property of red beds may contain alteration fluid of igneous material,derivative fluid of salinized lake,atmospheric freshwater and endogenous-exogenous organic acid.Synthetical analysis believes that the main controlling factors in reservoirs of red beds on the south slope can include lithology and lithofacies,burial evolution,compaction strength and fluid reform.lithology and lithofacies determines the initial porosity of sandstone reservoirs in different provenance areas,and influence the basis and origin of pore evolution;Burial evolution,as the bridge connecting pore evolution,acts on the diagenetic sequence of different structural zones;Compaction strength and fluid reform related to diagenesis,are the key to determine reservoir’s physical properties.Four types of effective reservoir development model about ‘early alkaline cementation,three acid domination,follow ladders distribution’ has been eastablished under discreet consideration,the comprehensive evaluation standard of the reservoir has been defined,and the regional planar prediction of reservoir with different grades has been completed.