稠油热采井电阻率显著降低的机理研究

针对注蒸汽热采区块中加密调整井电阻率显著降低的问题,应用沉积学原理及孔道迂曲度参数,分析热采过程中亲水大孔道的形成机理及其对储集层电学性质的影响,以视电阻率构成模型为基础,研究不同厚度及电阻率组合与视电阻率的关系。提出沉积作用导致的储集层多层次的非均质性以及高温蒸汽和热水沿高渗透条带的线性突破,是开发层段内电各向异性产生的主要原因;由于普通分辨率的测井仪器对各向异性地层中低电阻率段的反应特别灵敏,致使水线突破后加密调整井的电阻率显著下降。认为虽然加密调整井储集层过低的电阻率不能反映其中真实的含油水情况,但是通过电阻率的变化研究蒸汽在储集层中线性突破的规律,对于深入评价油藏特征、及时调整开发策略具有一定的意义。图4参11

Resistivity drop mechanism during heavy oil thermal recovery

Reservoir resistivity falls obviously in adjustment wells during thermal recovery. The formation mechanism of large waterwetting channels and their influence on reservoir electrical properties was analyzed based on the basic sedimentary theory and tortousity parameters. Reservoir heterogeneity and hot steam breakthrough is the main reason for anisotropic electrical properties. The normal-resolution logging instruments are sensitive to the low-permeability zones in anisotropic formations, which results in the obvious decrease of resisitivity. The low resistivity of the adjustment wells cannot reflect real saturation of the output zones, but it offers information for the study of steam breakthrough rules, reservoir evaluation and development adjustment.