*1.2. Geological Background*

The Du 66 block of the Shuguang oilfield is structurally located in the northwest of the Shuguang oilfield in the middle part of the western slope of the Western Sag of the Liaohe fault basin. The development target stratum in this area is the Dujiatai reservoir in the upper fourth member of the Shahejie Formation of Paleogene. Up to 2000, the proven oil-bearing area in this area was 9.41 km2, and the petroleum geological reserve was 5935.2 × 10<sup>4</sup> t.

The top surface structure of the Dujiatai oil layer in the Du 66 block of the Shuguang Oilfield is generally a monoclinic structure under the slope background, which is inclined from the northwest to the southeast. The dip angle of the stratum is generally 5◦ ~ 10◦. Reservoir lithology is mainly conglomerate sandstone and unequal-grained sandstone with medium sorting deviation, belonging to medium-high porosity and medium-high permeability reservoirs. The oil layer is mainly composed of a thin to medium–thick layer and the reservoir type is layered edge water reservoir. The density of crude oil at 20 ◦C is 0.9001–0.9504 g/cm3, and the viscosity of ground degassed crude oil at 50 ◦C is 325–2846 mPa·s, which is ordinary heavy oil.
