Jiyang Depression Tertiary Stratigraphic Reservoir Formation Mechanism

In this paper, based on sedimentology and sequence stratigraghy, three dimensional numerical simulation and petroleum migration physical analogue as technical measure, study and practice as mainline. Integrated information about geology, geophysical and assaying, study structural sequence and sedimentary system of transition period of fault sag in Jiyang depression。 Based on the conditions, reservoir feature, petroleum migration and accumulation conditions and passage system were thoroughly analyzed, petroleum pool-forming process was modeled taking Dongying depression as an example. Several achievements and conclusions had been obtained in this paper as follows:1.Considering the tectonic movement and ancient geography, this paper comprehensively analyses the features of the evolution of tertiary in Jiyang depression, the features includes strata, structure and sediment etc, and combines the research findings of structural sequence that was studied by predecessors, tertiary of Jiyang depression is divided into four structure layer including basal stratum, infrastructure, up structural layer and top structural layer. every structural layer has different geology, physical geography and geochemistry feature. These structal layers are different from each other in geology, geophysical and geochemistry, since they underwented different tectonics.2.Difine that transitive stage of fault sag in fault basin is from the stable stage of fault subsidence to the initial stage of depression. And elaborates the basic feature of transitive stage of fault sag, structural transitional stage formed large-scale unconformity, basin structure translated from asymmetry half graben to approximate symmetry half graben, main control rupture translated from northwest to northeast and east northeast, sedimentary environment translated from shallow water lake facies to fluvial facies, filling model of basin translated from quickly filling to slowly overlapping, magmatic activity gived priority to eruption and was medium intensity.3.Analyses main structure feature of transitive stage of fault sag and the feature effected reservoir formation and distribution.Strata overlap belt of transitive stage of fault sag widely distributed, this stage was the very development period of strata overlap of Cenozoic strata in Jiyang depression. The wide development strata overlap belt of different period and different level provided passage for petroleum migration, created beneficial reservoir conditions for strata reservoir formation.4.This paper correlated and analyzed a lot of drilling, coring, well logging and seismic data, the transitive stage of fault sag was divided into two 2nd -order sequence. And further divided into three 3rd-order sequence, including Es2s-Esl sequence, Ed sequence, Ngx sequence. Due to own feature of the transitive stage of fault sag, systems tract of different sequence adopted trichotomy and dichotomy. Characteristic of sequence contained two respects: plane symmetry of sequence structure and relative stability of strata distribution, strata onlap and truncation strata superposed development.5.Oil and gas of transitive stage of fault sag derived from Es4s, Es3x, Es3z and Es1. Organic matter abundance of Es3x is high, potentiality of generating hydrocarbon is great and distribution is stable. Es3x is the main period of goodness hydrocarbon source rock development in Jiyang depression.6.Passage systems of petroleum migration and accumulation of the transitive stage of fault sag in fault basin included rupture passage system, sandstone passagesystem, surface of unconformity passage system and complex type passage system. And circumstantiated the feature of every passage system.7.Taking the Dongying depression as an example, discussed hydrocarbon expulsion action and faults activity and formation of the traps and conservation conditions and spatial relationship of geologic feature. Analyzed migration regularities through unconformity of gentle slope and steep slope in Dongying depression by indoors simulating experiments, revealed the relation of unconformity and palaeotopography with oil reservoir, discussed mechanism of accumulation of strata overlapping oil reservoir, and they were helpful for exploration and exploitation...