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Analysis On The Complex Seismic Micro-facies Of Shallow-water Delta

Posted on:2012-06-13Degree:MasterType:Thesis
Country:ChinaCandidate:S Y LiFull Text:PDF
GTID:2180330332988881Subject:Marine Geology
Abstract/Summary:PDF Full Text Request
In the Bohai Bay Basin, the shallow-water delta of Neocene period is widely distributed, the subtle traps of which have large exploration potential, and sandbody predication is one of the most important tasks in exploration of subtle reservoir. The paper takes the Neocene in Yellow River Mouth Sag as the example, and the high frequency sequence stratigraphic framework is built up by well-to-seismic integration. The relationship of geology-geophysical for different lithology in subsequence is built up by the statistics on lithology of more than 70 wells in study area, on the basis of that, the sandbody characterization and composite seismic micro-facies analysis are studied. This paper has given below main fruits:According to the vertical features of subsequence, the high frequency sequence framework of low sub-segment of Minghuazhen formation (mL2), there are 10 subsequences in the well area of BZ29 and BZ34, and 11 subsequences in the well area of BZ26, and there are progradation configuration, retrogradation configuration and aggradation configuration in subsequences of different periods.On the basis of statistics of lithology in subsequence, by the measures of sedimentary micro-facies analysis and forward modeling, the relationship of geology-geophysical of genetic sandbody in key area is built up. The amplitude is strong for thick layer, such as a single and multiple thick layer distributaries channel; and the amplitude is middle-middle to weak for thin layer, such as a single and multiple thin layer distributaries channel, distal bar and bank; the amplitude is middle-middle to strong for composite micro-facies with composite wave. 2D forward modeling shows that the lateral connectivity of sandbody of early low-stand—transgression system tract is better, and contact style of sandbody is the assembly, the continuity of seismic reflection is poorer but the amplitude is strong, which shows the channels of multiple terms are superimposition relationship and destroyed each other. In later low-stand—transgression system tract to early high-stand system tract, the sandbody is isolated, and the mudstone well develops, the forward modeling shows the isolated and lens-shaped reflection, Influenced by acoustic velocity, sandbody thickness and extent in lateral, the amplitude of different sandbody varies greatly. In the later high-stand system tract, the thickness of sandbody is increasing, the lateral connectivity is better, and contact style is joined-plate. The seismic reflection is high continuity, strong amplitude and parallel or sub-paralleling wavy reflection.Combined with regional sedimentary facies features, there are 4 composite seismic micro-facies identified:distributaries channel, distributaries channel-distal bar, distal bar-distributaries channel and distal bar-bank. In the early of low-stand—transgression system tract, it is distributaries channel near the source direction, and it changes to distributaries channel-distal bar and distal bar-bank in the central of basin. Along the southwest, the delta extends far to the basin; the distributaries channel is the main composite seismic micro-facies. In later low-stand—transgression system tract to early high-stand system tract, the distributaries channel-distal bar is the main facies, followed by distal bar-bank, and in the east of study area, the distal bar-distributaries channel is developed. In the later high-stand system tract, the distributaries channel well develops, followed by distributaries channel-distal bar, and in the east and south of study area, it develops distal bar-bank.
Keywords/Search Tags:Yellow River Mouth Sag, Neocene, shallow water delta, composite seismic micro-facies, forward modeling
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