Research On Mechanism Of Oil Flooding By CO₂ In Block Du-84, Liaohe Oil-Field

In Block Du 84, the main hyper-heavy oil block in Area Shu 1, vertically develop Neogene Guantao oil layer and Palaeogene Xinglongtai oil layer, constituting the main hyper-heavy oil layers. The explored oil area of Guantao covers 1.4km² and the explored geologic reserve is 1970×10⁴t, whose oil layer has a single structure that is monoclinal structure with NW elevating, angle 2°-3°. The explored oil area of Xinglongtai is 3.76km² and the explored geologic reserve is 3661×10⁴t, whose oil layer has a single structure that is oval-like monoclinal structure with NW-SE dipping, angle 2°-4°.Based on a lot of experimental analyses, this paper studies on the solubility of CO₂ into the hyper-heavy oil in Block Du 84 and its effect on the property of crude oil. The paper also studies on oil recovering pattern, production and stimulation mechanism of three huff-puff methods, including steam huff-puff, steam+CO₂ huff-puff and steam + CO₂ + agent huff-puff. It is concluded that: (1) the solubility of CO₂ in the crude oil in Block Du 84 is very low. The solubility increases with pressure rising. When the temperature rises, the solubility increases at first and then decreases, depending on the viscosity of crude oil. (2) The production pattern of steam huff-puff in Block Du 84: periodic output goes up rapidly along with the increase of periodicity at first and then goes down promptly. (3) Compared to steam huff-puff, steam + CO₂ + agent huff-puff has larger cyclic steam injection volume, higher cyclic degree of reserve recovery and higher water degree of recovery. (4) The best flooding aiding agent is WZ-AS hyperthermic foam, the next by mixed mode, the last by EOR-CL/LH-XIII sulfosalt.This study not only offers experimental criteria and reference for the production of heavy oil in Area Shu 1 in Liaohe Oilfield, but also offers some guidance for the future production of heavy oil in Liaohe Oilfield and other oilfields.