Research On Characteristic Of Low Amplitude Structures And It's Relationship With Hydrocarbon Accumulation Of Yanan Formation In Pengyang Area

Ordos Basin is the second largest sedimentary basin on land in china which has great potential of oil and gas exploration.With the development of reservoirs,it is found that the low amplitude structure reservoirs are widespread in Pengyang area where is located in the Southwest Margin of the Ordos Basin.Due to the influence of complex tectonic evolution of the conterminous southwest margin,it is difficult to recognize the low amplitude structure and to reveal the regularity of hydrocarbon accumulation.Therefore,it is urgent to identify the low amplitude structure.In order to improve the prediction accuracy of low amplitude structure of the Yanan Formation in the southern Tianhuan Depression where is only covered by 2D seismic data,tomographic static correction technology was optimized to solve the problems of long and short wavelength imaging.After that,reverse linear noise suppression technique based on data reconstruction was used to reprocess the data which have problems of strong interference and low signal-noise ratio in loess tableland area.Then the Subtle horizon labeling of the research area was used.Problems such as low signal-noise ratio of seismic data and incomplete amplitude,frequency,and phase of intersecting seismic lines were solved by means of the integration of data processing and interpretation.Then,faults identification techniques such as seismic reflection features and forward modeling and low amplitude structures prediction techniques like variable-speed mapping and small grid large scale mapping were adopted to identify low amplitude structures and analyze the relationship between these structures and hydrocarbon accumulation.Finally,the study on the relationship between paleogeomorphology,paleostructure and the low amplitude structural reservoirs in the research area was carried out to understand the influence of tectonic evolution on low amplitude structural reservoirs.To sum up,the genesis of low amplitude structures in the region is complicated under comprehensive influences of denudation ?extrusion and differential compaction,and Yan9,Yan8 and Yan7 oil-bearing horizons of Yanan Formation are main productive layers in the study area.The low amplitude structure is the dominant controlling factor of reservoirs and the small faults,folds and fractures caused by activities of the western margin fault zone are goodmigration pathways for hydrocarbon.The tectonic evolution of Tianhuan Dpression has great influence on the low amplitude structures in this area,which lead to multiple migration and final accumulation of hydrocarbon at high structural portions in the low amplitude structures.