| Based on make full use of the results of previous studies, take stratigraphy，sedimentology, geochemistry and diagenesis theory as guide. Using test data of thinsections, scanning electron microscope analysis， rare earth elements, majorelements, trace elements, Fluid inclusions，Cathodoluminescence，X-ray diffraction ofthe clay minerals, vitrinite reflectance etc. This paper carried out the study onmechanism of cyclic sedimentation and diagenetic system material couplingrelationship in Jiyang Depression Paleogene Kongdian formation. Made the followingunderstanding:The research of substance cyclic deposition mechanism and material gatheredregular is based on the research of palaeogeographic and sedimentary filling. Thischapter uses the mineral composition, heavy minerals, rock types, sedimentarystructures, minerals and debris, logging, geophysical to research material sources andsedimentary filling type; On this basis, the substances macro filling way and law inthe depression is investigated during the deposition of Kongdian formation. Studieshave shown that:1) The main material source in Kongdian formation is north-southdirection, then is east-west direction, has the characteristics of multi-material sources.2)The deposition material filling types in Kongdian formation main include alluvialfan, river-flood plains, nearshore subaqueous fan, fan delta lakes (Salt Lake-saltwater lake), beach bar and turbidite fan etc;3) The Kongdian formation seismicfacies is similar to the third section of Kongdian formatin are presented in eachpartition phase sequence the one-way graded law,namely foreset phase transition tothe filling, then transition to sheeted phase. The second section of Kongdian formationseismic facies plane distribution in Jiyang depression lake center area are mainlyfilling phase and sheeted parallel phase, fault developed foreset phase, messy phaseand wavy phase. The characteristic of the seismic facies plane distribution in the firstsection of Kongdian formation is mainly sheeted parallel facies. Compared with the second section of Kongdian formation, in the first section of Kongdian formation thefilling phase in each subsag lake center area significantly narrowed.4) In the thirdsection of Kongdian formatin period, Huimin depression mainly developed fan delta(alluvial plains)-combination of lake sediments, and alluvial fan in the local area; thenorthern Dongying Sag developed nearshore water fan-lacustrine depositionalsystem, and BoxingPlain developed alluvial depression;In the second section ofKongdian formation period, the rift developed period, typical characteristic of theearly is basalt eruption and local area developed volcanic rocks,to deposition periodof the late of the second section of Kongdian formation, the lake basin is basicallyformed. Extensive developed alluvial fan, braided river systems, DongyingDepression and Huimin depression developed nearshore subaqueous fan–lake andfan delta-lake sedimentary system combination; In the first section of Kongdianformation period, sedimentary filling types are mainly alluvial, river diffuse and thealluvial plains deposition system. Finally, based on the study of the structure andsedimentary, detailed study the depositional model of Kongdian formation andestablished Kongdian formation mode chart.Observed by a large number of logging data and core, then detailed study of thecharacteristics of the different scale lithologic and stratigraphic cycles. Studies showthat Kongdian formation color cycles have red-gray-red stratigraphic cycles inmacro-scale and color cycles mainly include the lithology changes and color changes,across a variety of lithologic cyclicity, the color of the same lithology cyclicity inmicro-scale. The macroscopic scale lithological cyclicity are mainly positive cyclesthe lithology superimposed and anti-cyclic lithology stacked. The microscopiccyclicity are mainly interbedded sandstone and mudstone, granularity cyclicity cream,interbedded shale and mudstone. Cyclicity and depositional environment has somecorrelation and indicates different sedimentary environments, the color depositionchanges indicate changes in water medium and material sources. Using geochemicalmeans, detailed discuss the formation mechanism of the different cyclic sedimentation.The macro cyclicity reacted the drought shock lakes-a relatively wet cycles-droughtshock lakes. Lithology changes occur simultaneously with the color change is mainlyclastic material concussion change under drought conditions. Across a variety oflithologic cyclicity are related to the deposited water medium and climatic conditions.The same lithology color cyclicity are associated with the aqueous medium andclimatic conditions. Macroeconomic cycles change with the change of thedepositional environment, such as interbedded sandstone and mudstone generally appear in the littoral and shallow lake. Macro cyclicity is related to shock action ofwater and material sources, such as interbedded cream rock and mudstone is related tomaterial sources and climatic conditions of intermittent the Salt Lake.By cyclic sedimentation minerals change, changes in the major elements, traceelements change, ree distribution analysis,emphasis selected Wang100well andHaoke1well for complete samples, detailed study of the material accumulation lawand distribution mode in the process of cyclicity. The results show that in the processof color cyclicity overall have some regular of mineral aggregation responsecharacteristics. In the longitudinal evolutionary of wang100well, have some changesof quartz content is gradually increased, K-feldspar content gradually increased,Plagioclase content gradually reduced, calcite content decreased, anhydrite contentgradually increased etc. The mineral cycles change and color cycles change has bettercoupling relationship. The instability of Part mineral content may be due to thetransformation effect of the late diagenetic fluid. The study of cyclicity of two keywells showed that cyclicity and element enrichment have some coupling relationship.Study of HaoKe1well show that, besides elements change is related to color,lithology is also accounts. Wang100well showed in the vertical evolution thatconstant elements of Al, Ca, Fe, Mg content, there is an increasing trend. Traceelements of Sr, Ba, Ga, Co content showed an increasing trend. Cyclicity and elementratio have better coupling relationship, especially Fe/Mn and V/Ni ratio showingthe changing characteristics of multi-level cyclicity. The microscopic color cyclicityand REE distribution way also has some coupling relationship, such as Wang46welland Wang100well typical cycle and REE distribution way showed that the graysiltstone overall is higher than mauve siltstone element content and showed a positiveanomaly; The rare earth elements (REE) content of purple siltstone or mudstoneoverall is higher than the gray rock that showed a positive anomaly.Using sheet microscopic identification, the clay mineral X color, rock pyrolysispeak temperature, scanning electron microscopy, fluid inclusions and other means toresearch diagenesis system in Kongdian formation. The results show that:1) Thematerial composition in different parts have some differences, the basin center mainlyis arkose and southern gentle slope with lithic arkose.2) Diagenesis phenomenon hascharacteristics of compaction is not obvious, carbonate cements is better developedand was presented as basal cementation, anhydrite developed in basin center, quartzovergrowth is not developed, dissolution relatively developed and occur fill dissolved.3) Diagenesis differences mainly reflected in the performance of regional diagenetic phenomenon interstitial material, compaction, diagenetic environment, lithologicalcyclicity also has differences in diagenetic phenomenon, especially lithologiccyclicity lead to diagenesis differences.4) Using diagenetic evolution stage aspartitioning standards to judge diagenetic stage of Kongdian formation mainly indiagenetic A period, different burial depth and regions have different differences, andbased on the recovery of Kongdian formation diagenetic evolution proposeddiagenetic evolution Kongdian formation reservoir has a certain influence.5)Kongdian formation have the characteristics of local area is open diageneticenvironment and the overall is closed diagenetic environments, diagenetic evolutioninfluenced by the original deposition fluid, deep buried environments, tectonic-magmatic activities.6) study on rock Kongdian water-rock interaction mechanismand precipitation mechanism of calcite cement, anhydrite cements, siliceous cement,clay mineral.By study on different mechanism of cyclic sedimentation and diagenetic systemto explore the coupled relationship between cyclicity and diagenetic material. Thecyclicity and minerals coupling, the lithological cyclicity has two cases: the firstcyclostratigraphy with poor sorting and poor structural maturity diagenetic fluid ishard to flow, so substances inheritance is relatively good and coupled better with theoriginal sedimentary material; the second sandstone with better sorting and bettertextural maturity, due to the transformation of the diagenetic fluid is relatively easyand good liquidity,so the cyclic sedimentation substance coupling is rrelatively poor.Stratigraphic cycles changes in color due to different causes, but original sedimentsdistribution cyclicity under general buried conditions is better coupled with today’srock substance. The coupling relationship between cyclicity and elements is mainlyrelated to sealing of lithology and diagenetic system, so sandstone with poor coupling,mudstone with good coupling, open systems with poor coupling, closed systemswhith good coupling. The diagenetic fluid play a key role in original depositionmechanism and diagenetic system substances coupling. |
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