China Petroleum Exploration ›› 2024, Vol. 29 ›› Issue (4): 160-169.DOI: 10.3969/j.issn.1672-7703.2024.04.012

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Logging evaluation method for sweet spots classification of the interlayered type shale oil in continental lake basin: a case study of the seventh member of Yanchang Formation in Wuqi area in Ordos Basin

Li Chaoliu1,Wang Changsheng2,Zhang Wenjing2,Wang Min1, Li Gaoren2,Xu Hongjun1   

  1. 1 PetroChina Research Institute of Petroleum Exploration & Development; 2 Research Institute of Exploration & Development, PetroChina Changqing Oilfield Company
  • Online:2024-07-15 Published:2024-07-15

Abstract: In view of the difficulty in logging evaluation of the interlayered type shale oil sweet spots, a quantitative evaluation method has been proposed for the coupling relationship of source rock quality parameters, reservoir quality parameters, and their spatial distance, achieving the production capacity classification of the interlayered type shale oil and the determination of the lower limit standard for sweet spots with commercial oil flows after calibrated by well test data, which is reliable confirmed by multiple wells. Based on geochemical experimental data of core samples, a regional model for qualitative TOC calculation has been constructed by using logging data, and the effective source rock interval in the seventh member of Yanchang Formation in Wuqi area has been determined by referring to the relevant standards. The porosity-permeability relationship curve has been used to calculate the reservoir quality factor, and the vertical shortest distance between reservoir interval to be tested and effective source rock has been determined. Finally, a formula for calculating source rock and reservoir coupling coefficient that reflects the coupling relationship between the tested interval and the adjacent main source rock has been established by combining with reservoir quality factor, average TOC and effective source rock thickness. After calibrated by well test results, the lower limit of coupling coefficient in an oilfield or a well area with commercial oil flows has been determined, which enables to evaluate intervals to be tested in new wells and avoid ineffective well testing, improving success rate of unconventional oil and gas well test and providing decision basis for the optimization of capacity construction.

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