Oil & Gas Geology ›› 2020, Vol. 41 ›› Issue (1): 144-156.doi: 10.11743/ogg20200113

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Dolomite reservoir prediction with lithology factor in the Maokou Formation, Fuling area, Sichuan Basin

Ling Liu(), Yujin Wo, Tao Zhang, Wei Sun   

  1. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China
  • Received:2019-08-09 Online:2020-02-01 Published:2020-01-19
  • Supported by:
    国家自然科学基金重点资助项目(U1663209);国家科技重大专项(2017ZX05005);中国科学院A类战略性先导项目(XDA14010201)

Abstract:

Large P-wave impedance difference exists between the Maokou Fm.carbonates and overlying carbonaceous mudstones at the bottom of the Wujiaping Formation in Fuling area, southeastern Sichuan Basin, resulting in a continuous strong reflection interface(TP2), which shields the seismic response of the underlying dolomite reservoirs.Due to the superimposition of the P-wave impedance between dolomite and limestone in the Maokou Formation, post-stack seismic prediction of the dolomite reservoir is difficult.In addition, the effective angle of the original CRP gather is only 20°, and the lacking of high-angle information is unfavorable for the calculation of pre-stack elastic parameters.On the basis of the CRP gather optimization, superimposed near-and medium-angle data were formed with the technology of multi-wavelet decomposition and reconstruction.Then, the ray elastic impedance of the two superimposed data volumes was obtained by Bayesian sparse pulse inversion.The lithology factor was built by coordination rotation to identify dolomite reservoirs via the ray elastic impedances of near-and medium-angle information.Multi-wavelet decomposition and reconstruction can effectively suppress the strong inference of the carbonaceous mudstone, and highlight the seismic responses of dolomites, thus improving the accuracy of reservoir prediction.The lithology factor obtained can be applied to avoid problems relating to the lack of high-angle CRP gather and the difficulty in elastic parameter calculation.In conclusion, the dolomite reservoirs in the Mao 3 member are distributed in blocks along basement-rooted faults, the thickness out of seismic prediction by lithology factor is in good agreement with actual drilling data, indicating that the technology could be applied to the effective prediction of dolomite reservoirs, and is of promotional value in practice.

Key words: CRP gather optimization, multi-wavelet decomposition and reconstruction, ray elastic impedance, coordinate rotation, lithology factor, dolomite, Maokou Formation, Fuling area

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