Xinjiang Petroleum Geology ›› 2020, Vol. 41 ›› Issue (5): 535-541.doi: 10.7657/XJPG20200504

• OIL AND GAS EXPLORATION • Previous Articles     Next Articles

Seismic Prediction Methods of Shale Oil Sweet Spots in Lucaogou Formation of Jimsar Sag

JIA Shuguang1(), WANG Jun2, WANG Lingling1(), YU Hongguo2, QI Jie2, ZENG Tan1   

  1. 1. Beijing Jinhainengda Technology Limited Company, Beijing 102299, China
    2. Xinjiang Branch, CNPC Logging, Karamay, Xinjiang 834000, China
  • Received:2019-09-15 Revised:2020-07-13 Online:2020-10-01 Published:2020-10-10
  • Contact: WANG Lingling E-mail:shuguangjia@126.com;wll_gzf@163.com

Abstract:

It is difficult to predict the tight dolomite reservoirs in the Lucaogou formation in the Jimsar sag of the Junggar basin using conventional seismic inversion methods because of the poor physical properties, strong heterogeneity and small impedance contrast between the sweet spot reservoirs and surrounding rock. We begin with rock physics to analyze the seismic response characteristics of the tight reservoirs and search for sensitive parameters of inversion, then carry out poststack and prestack inversion to detect shale sweet spots, and finally select the most suitable methods according to the actual drilling results, and develop comprehensive technologies for predicting shale oil sweet spots. The study indicates: 1. The crossplot of P-wave velocity and density after coordination rotation can be used to identify ClassⅠ reservoirs in the upper sweet spot interval in the Lucaogou formation; 2. The crossplot of P-wave impedance and S-wave impedance can distinguish ClassⅠ, ⅡfromⅢ reservoirs and non-reservoir zones in the lower sweet spot interval in the Lucaogou formation; 3. NMR porosity is the best parameter for shale oil identification, whose lower limit is 4%; and 4. The comparison of the identification results from poststack RMS amplitude, poststack absorption attenuation, prestack AVO and prestack synchronous inversion methods, and formation test data indicates that prestack synchronous inversion is more advantageous in sweet spot prediction in the study area, and based on which, 3 types of reservoirs are classified.

Key words: Junggar basin, Jimsar sag, Lucaogou formation, shale oil, sweet spot, reservoir prediction, seismic attribute

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