Geophysical prediction and evaluation of lacustrine shale oil and gas: Applications in the Fuxing area

Abstract

The lacustrine shale reservoirs of Jurassic age in China’s Sichuan Basin contain multiple hydrocarbon-bearing intervals and host substantial shale oil reserves, making them promising candidates as a significant replacement resource base for the region’s petroleum production. However, the efficient exploration and development of lacustrine shale is confronted with two key geophysical challenges. Specifically, the first challenge involves identifying the location of the “sweet spot” with a primary emphasis on the engineering “sweet spot,” characterized by critical parameters such as brittleness index and stress. The second challenge pertains to evaluating the effectiveness of hydraulic fracturing. To address these challenges, we first use engineering “sweet spot” seismic prediction technology to delineate the most favorable engineering zones, which subsequently guide well deployment and the design of horizontal well trajectories. We then use microseismic monitoring to assess the effects of hydraulic fracturing. Finally, we integrate these two technologies to form a complete geophysical workflow and conduct a comprehensive interpretation to understand the primary controlling factor. This integrated geophysical workflow effectively evaluated lacustrine shale reservoirs in the Sichuan Basin of China, providing robust recommendations for subsequent well placement, well trajectory design, and enhancing development efficiency in this complex geological setting. The analysis in this paper indicates that the brittleness index was the primary controlling factor in this geological setting, with higher values consistently corresponding to more microseismic events, and more extensive fracture networks.

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