大芦湖油田樊124断块CO_2混相驱过程中沥青质沉淀实验研究

Experimental studies on asphaltene precipitation with CO_2 miscible flooding in Fan 124 block of Daluhu Oilfield

针对胜利油区典型的低渗透油田———大芦湖油田樊124断块的油藏条件,利用SDS固体沉淀实验装置对5种压力下注入CO2过程中沥青质的沉淀情况进行了研究,确定了沥青质沉淀析出的条件及沉淀量,并提出了预防沥青质沉淀的措施。研究结果表明,在樊124断块进行CO2非混相驱,不会产生明显的沥青质沉淀,而在高于26 MPa下进行CO2混相驱时,会产生少量沥青质沉淀,且注入压力越高,沥青质沉淀趋势越强,但由于地层油中原始沥青质含量较低,产生的沥青质沉淀量不大;根据樊124断块油藏流体条件,在较低的压力(<26 MPa)下进行CO2混相驱或近混相驱,既能获得较高的原油采收率,又能避免或减少沥青质的沉淀。

Based on the characteristics of Fan 124 block in Daluhu Oilfield which is a typical low permeability oil reservoir in Shengll Oilfield, the result of asphahene precipitation in the course of CO2 injection under five pressures gradient was studied by the SDS solid precipitation test apparatus, The removal condition and quantity of asphaltene precipitation were determined and some methods which keep asphaltene from precipitating were submitted, It is shown that asphaltene precipitation will not be generated obviously during CO2 non-miscible flooding in Fan 124 block, but when the pressure is more than 26 MPa, a little precipitation is-generated. The higher pressure is, the more precipitation is. Because of a low initial content of asphaltene in reservoir oil, a little precipitation is generated ultimately. According to the characteristics of fluids in Fan 124 block, running CO2 miscible flooding can not only gain higher oil recovcry, but also keep asphaltene from precipitating or decrease the precipitation under a lower pressure.