低渗稠油高压降黏驱高黏阻滞带形成机制与主控因素——以胜利油田王152油藏为例

Formation mechanisms and main controlling factors of high⁃viscosity blocked zone in low⁃permeability heavy oil with high⁃pressure viscosity reduction:Taking Wang 152 reservoir of ShengLi Oilfield as an example

化学降黏剂驱已在胜利油田深层低渗稠油中开展了初步先导试验,但试验表明井间存在高黏阻滞带,降低了地层渗流能力。因此,借助降黏剂驱岩心流动实验,结合必要的测试分析,剖析低渗稠油降黏驱高黏阻滞带形成机制与主控因素。结果表明,大排量高压注入降黏剂会在驱替前缘形成高黏阻滞带,影响驱替压力传导、降低驱油效果。该高黏阻滞带形成核心机制在于:(1)高压注入增加低孔压区域有效应力,地层孔喉受到挤压损害渗流能力;(2)高压快速降黏剂驱时,轻质组分优先流出,重质组分滞留、堆积、压实从而堵塞细小孔隙,形成高黏稠油沉聚的高饱和度油墙;(3)高压注入降黏剂会加剧其指进窜流,驱替前缘易形成W/O乳状液,增大混合流体的黏度。由此,对于低渗稠油油藏降黏驱开发,应采取多轮次温和注入降黏剂的开发模式,渐进式建立注采井间稠油整体驱动,进而有效规避稠油高黏阻滞带的形成,提高降黏剂驱油效果。

Preliminary pilot tests of chemical viscosity reducer flooding are carried out in deep low-permeability heavy oil in Shengli Oilfield,however,earlier tests show high-viscosity blocked zone existing between wells and re‑ducing flow capacity.On this basis,the formation mechanisms and main controlling factors of high-viscosity blocked zone in low-permeability heavy oil are analyzed by core flow experiment of viscosity reducer flooding combined with necessary test analysis.The results show that injection of viscosity reducer with large discharge and high pressure may form high-viscosity blocked zone at the displacement front,causing influence on transfer of displacement pres‑sure and displacement effect.The core mechanisms of blocked zone formation are:(1)High pressure injection in‑creases effective stress in low pore pressure area,and formation pore throats are squeezed to damage flow capacity;(2)During rapid high-pressure viscosity-reducer flooding,light components flow out preferentially,while heavy components’retention,deposition and compaction block small pores and form high-saturation oil bank where high-viscosity oil is deposited;(3)High-pressure injection of viscosity reducer may aggravate its fingering and channel‑ing,and the displacement front is likely to form W/O emulsion,increasing viscosity of mixed fluid.Therefore,for the development of low-permeability heavy oil reservoirs with viscosity reducer flooding,the development mode of multiple rounds of mild injection of viscosity reducer should be adopted,and overall driving of heavy oil between in‑jection and production wells should be gradually established,which can effectively avoid the formation of heavy oil blocked zones and improve displacement effect of viscosity reducer.