Palaeogeomorphological features and their bearings on the hydrocarbon accumulation in the Wuqi oil field, Ordos Basin during the Lower Jurassic

The palaeogeomorphological features during the depositional periods are interpreted as important factors to control the development and distribution of sedimentary facies, and to a certain extent, to control the types and distribution of oil traps in the Wuqi oil field, Ordos Basin. In this study, the compensation impression method is employed to reconstruct the pre-Jurassic palaeogeomorphological features, clarify the local structural features, and predict the favourable reservoir facies zones. The palaeogeomorphological features controlling the distribution of oil pools in the study area include the palaeovalleys incised into the Yanchang Formation as main channels for the migration of hydrocarbons; topographic highs as the main direction for the migration of hydrocarbons; the sandstones along the palaeovalleys as the favourable localitites for the accumulation of hydrocarbons, and the overlying marsh mudstones as good lithologic barrier.