Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (1): 213-228.DOI: 10.13745/j.esf.sf.2022.8.37

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Application of OVT-domain 5-dimensional seismic attributes in fracture prediction in the Qixia Formation of the Shuangyushi area

ZHOU Lu1,2(), ZHOU Jianghui1, DAI Ruixue3, ZHANG Ya3, LAN Xuemei3, WU Yong1, WANG Hongqiu4, LIU Shimin1   

  1. 1. Sichuan Key Laboratory of natural gas geology, School of Geosciences and Technology, Southwest Petroleum university, Chengdu 610500, China
    2. State Key Laboratory of Oil and Gas Reservior Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
    3. Exploration and Development Research Institute of PetroChina Southwest Oil and gas field company, Chengdu 610041, China
    4. Northwest Branch of China Petroleum Exploration and Development Research Institute, Lanzhou 730020, China
  • Received:2022-07-07 Revised:2022-08-05 Online:2023-01-25 Published:2022-10-20

Abstract:

The ultra deep carbonate reservoir of the Qixia Formation, Shuangyushi area, northwestern Sichuan features strong lateral heterogeneity, complex structure, many drilling wells and great disparity in downhole natural gas production. Using OVT-domain 5-dimensional seismic data, fracture prediction, gas-bearing property assessment and real drilling verification analysis are carried out for this set of reservoirs. The first task is to detect fractures and karst caves in the carbonate reservoirs based on the differences in OVT-domain seismic attributes between different directions. The second task involves analyzing azimuth attribute to find the dominant azimuth with seismic response more sensitive to gas-bearing formations thus more conducive to a positive detection outcome. Both tasks achieved good results in the Qixia Formation, Shuangyushi block in fracture prediction and gas-bearing property assessment. The extent of fracture development in the Qixia Formation, Shuangyushi area is relatively high, and fractures are mainly developed in three directions and oblique to the fault strike. Fault normal seismic data highlight the azimuthal anisotropy and can better detect small faults, while in the fault parallel direction fault-induced seismic anisotropy can be minimized for better oil and gas detection. Targeted pre-stack and post-stack gas detection methods can effectively predict the distribution characteristics of gas-bearing reservoirs of the Qixia Formation in the study area. According to the prediction the natural gas enrichment areas mainly distribute in the middle and southeastern parts of the study area, in contiguous strips along the NE-SW direction.

Key words: OVT data, azimuthal anisotropy, divide different azimuths, oil and gas detection, fracture oriented AVO

CLC Number: