Integrated employment of wireline logging and seismic data, turbidite fan types and distribution characteristics were analyzed in the Paleogene strata of the second Member of Dongying Formaiton. The results showed that: the study area developed many types of turbidite fan, including the slump turbidite fans, deepwater turbidite fan, steep nearshore turbidite fan, far shore slope turbidite fan, etc. There are significant differences in the developmental environment, sedimentary characteristics, the main factors and so on. The differences in delta size, provenance, ancient terrain and triggering mechanism affect the development of different turbidite fan deposits. By identifying wireline logs stacking patterns, the external geometry and internal reflection structure of seismic events, the types of lacustrine fan identification modes were determined. And also with three-dimensional seismic attribute analysis techniques for predicting sublacustrine fan and determining the plane distribution, it provide basic geological evidence for lacustrine fan hydrocarbon reservoir exploration.
Right now the application of seismic attributes in China is almost only qualified. Given this situation 2D crossplot analysis, the unary linear regression method and the method of fuzzy clustering analysis are applied to get the seismic attributes from the 3D data volume of oilfield C. The seismic attributes are then quantified and the ones which are good for depicting the reservoir are found and fine depict, thus the application of the seismic attributes is more specifically. It provides good idea and method for the optimization and application of seismic attributes.
In Liaozhong Depression, five types of sublacustrine fans are developed in the relative lowstand systems tracts of the fourth-order sequence in Dongying Formation. In drilling cores, typical turbidites characteristics exist including bedding structures such as slump deformation structure, parallel bedding, grading laminations and multi-stage scoured basal surfaces. They also can be recognized in well logs with distinctive low gamma-ray and high-resistivity stacking patterns. Logging curves usually display serrated bell shape, cylinder shape and funnel shape respectively. On seismic reflection profiles, sublacustrine fan typically shows lateral downlap on its external geometry and continuous or discontinuous “vermicular” reflection characteristics in its inner seismic reflection texture. According to the calibration results of drilling data, continuous seismic reflection profiles are interpreted to be mud-rich deposits with cohesive, soft sediment-deformation. Discontinuous seismic reflections with lateral migration and apparent incised valleys are interpreted to be sand-rich deposits which probably host the most potential litho-stratigraphic traps.
As the escalating hotspot and key object of hydrocarbon exploration, research of shallow-water delta deposits in China have made breakthrough in both in production and efficiency. Numerous results in Bohai Bay Basin show that the conditions of shallow-water delta sandbodies are widespread in late Paleogene and Neogene. In this paper, we analyzed the geological evidences, deposition microfacies and favorable reservoir conditions from structural phases, palaeontological characteristics, depositional characteristics and geophysical characteristics (stacking patterns of wireline logs and seismic reflection characteristics). The results indicate that shallow-water delta deposits usually develope in shallow-water area where exits flat and broad terrain, arid and hot paleoclimate, turbulent lake level and ample provenance. As for the reservoir conditions, rivers brought large amounts of organic matter and minerals into the lake, which aided in bringing up organisms. All these organisms provided basis for petroliferous source rocks. The mudstone layers developed above the shallow-water deposits which helped to form vertical patterns of reservoirs. These conditions determine that shallow-water delta deposits consist of excellent reservoir combination, various types of traps, sufficient source rocks, smooth migration pathways, which provided broad exploration prospects.
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