Sulige (Shanxi province, 750 km southwest of Beijing) is the largest onshore gas field in China (proven gas reserves of 1.1 trillion m3 in the last evaluation). Sandstone and mudstone in the main reservoir formation (He-8) were deposited in a deltaic plain of lower Permian age. Braided stream channels moved laterally and overlapped frequently, resulting in a very heterogeneous vertical stack of sand bodies. He-8 Formation has a thickness of 25–30 m but the sand layers with sufficient porosity and permeability are often less than 10 m. There is no correlation between the height of the reservoir and the total thickness of the formation, making conventional characterization based upon poststack data unreliable. This was the motivation for looking at prestack data to improve reservoir prediction.

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