Exploration theories and practices of buried-hill reservoirs: A case from Liaohe Depression

In recent years, various breakthroughs have been made in buried hill reservoir exploration in Liaohe Depression. Exploration targets have shifted from the Shallow-medium buried hill reservoirs with clearer reservoir-forming conditions to the low and inner buried hill reservoirs with deeper, hidden, and more complex features. Reservoir-forming conditions of low and inner buried hills were studied in aspects of basement tectonic activity, type of buried hills, lithology and reservoir characteristics, hydrocarbon generating system, and hydrocarbon conducting system. A practical classification method of inner buried hill reservoirs has been reestablished in accordance with the relationship between buried hills and hydrocarbon accumulations by studying reservoir characteristics of inner buried hill reservoirs with consideration of exploration practices. Such a classification method has widened the hydrocarbon searching scope in buried hills and built up a reservoir-forming pattern for the exploration targets inside buried hills with low amplitude, multiphase fractures, and multisource charging. Based on the theoretical studies and exploration practices of low and inner buried hill reservoirs, the 3P reserves reported for low and inner buried hill reservoirs reached 2.54 × 108 t and 1.76 × 108 t, respectively, from 2001 to 2006. The buried hill reservoirs have made significant contribution to increasing reserves and stabilizing production in Liaohe Oilfield.