Oil & Gas Geology ›› 2013, Vol. 34 ›› Issue (6): 847-854.doi: 10.11743/ogg20130620

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Hydrocarbon detection methods for the Paleogene ultra-deep gas reservoirs in the Qikou Sag

Hong Zhong1, Zhang Menggang1, Liu Huaqing1, Su Mingjun1, Yuan Shuqin2   

  1. 1. Northwest Branch of Research Institute of Exploration & Development, PetroChina, Lanzhou, Gansu 730020, China;
    2. Exploration & Development Research Institute, PetroChina Dagang Oilfield Company, Tianjin 300280, China
  • Received:2012-08-07 Revised:2013-06-27 Online:2013-12-08 Published:2014-01-04

Abstract: In recent years,exploration of the Paleogene ultra-deep gas reservoirs in the Qikou Sag has been fruitful.Yet no researches have been performed on the seismic response features of these gas reservoirs and relevant gas detection techniques,impeading exploration to some degree.In an attempt to solve these problems,a comparative study on various spectral decomposition methods was performed according to the typical frequency domain responses of the ultra-deep gas re-servoirs,i.e.high-frequency attenuation and low-frequency resonation.In addition,according to the features of the ultra-deep gas reservoirs,instantaneous wavelet absorption and amplitude to frequency ratio attribute were employed to detect gas-bearing intervals and their boundaries.The result shows that the spectral decomposition method is the basis of abnormal gas-bearing reservoir detection.The Short Time Fourier Transformation through Hanning time function with a time window length being two times of average distance between two through of seismic wavelets is suitable for detecting low-frequency abnormaly of gas reservoir with high resolution both in time and frequency domains.The results of gas detection with these techniques match the drilling results of the new exploratory wells,verifying the effectiveness of these methods in ultra-deep gas reservoir detection in the Qikou Sag.

Key words: window function, spectral decomposition, hydrocarbon detection, ultra-deep gas reservoir, Qikou Sag

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