水驱原油稠化对剩余油富集的有利影响

胜利油田虽已进入含水率约99%的特高含水期，但从取心情况来看，岩心含油饱和度主体在60%~80%之间，即岩心 含水饱和度低、水驱采出液高含水、电加热采出液几乎为纯油不含水。为解释这三点看似矛盾的现象，提出了地下原油水 驱后逐渐生物降解稠化的新型解释，认为油田长期开采后，会因为水驱而发生快速的生物降解。实验状态下，生物降解至 6 级以上大约需要8 周时间。由于原油的逐渐稠化，使胜利油田早期出现地表采出液特高含水的情况。地下含油饱和度仍较 高，且主体为难于采出的稠油和沥青，使剩余油富集。水驱的增稠作用虽然对过去的采收率有一定影响，然而就目前而 言，稠化后形成的周边沥青，对剩余油的富集反而起到了有利的保存作用。

Favorable Effects on the Densification of Water-drived Oil and Its Residual Oil Enrichment

SINOPEC Shengli Oilfield has reached the period when crude oil is produced with extremely high water content (approximately 99%). However, the oil saturations of cores are mainly between 60%-80%. This means that the water saturations of cores are relatively low, there is a high water content in the production fluid during water driving, and the produced liquid by electric heating is almost pure oil. To explain these seemingly contradictory phenomena, we present a new explanation in this paper. It is the gradual biodegradation that made the crude oil more viscous. The oil field underwent rapid biodegradation due to water flooding after long-term exploitation. Under experimental conditions, biodegradation of 6th level or above only took about 8 weeks. Due to the gradual densification of oil, a super-high water content of surface produced fluid appeared at the early period in the Shengli oilfield. However, the underground oil saturation is still high, and the oil is mainly composed of heavy oil and bitumen, which is difficult to be recovered. As a result, the residual oil was enriched underground. Although water flooding has some influences on the recovery factor in the past, but at present, it has preservative effects on the enrichment of residual oil instead.