Petroleum geology and exploration of beach sandbar in Junggar Basin, NW China: A case from Shawan Formation in Well Pai 2

Well Pai 2 is located at the Chepaizi high relief belt, west Junggar Basin. The Neogene Shawan Formation beach sandbar in the Well Pai 2 is developed by lake wave reconstruction of fan-delta and reworking in its frontal side or flank, which was caused by lake transgression and fan oscillation on the basin slope, in the continuously dextral and uplifting of Chepaizi relief and under the compression background during evolution of the Tertiary quasi-foreland basin. Depositional and electric characteristics of the beach sandbar are characterized by fine, loose grains, small thickness, two-stage cumulative probability curve, C-M chart showing PQRS paragraph mainly, moderate compositional and textural maturity, dactyline self-potential curve, and semi-funnel-shaped resistivity curve. After light oil charging, the beach sandbar reservoir show high amplitude, low-to-moderate frequency, and high absorption coefficient, and its energy amplitude shows clear boundary, convex top, and flat bottom. Beach sandbar has prospects for good physical properties and lithologic reservoirs.