白云岩油藏低渗透条带对剩余油分布的影响

Influence of Low-permeability Layers on Remaining Oil Distribution in Dolomite Reservoir

YM白云岩油藏已进入高含水开采期,如何寻找剩余油并进行挖潜是目前面临的重要问题。该类型储层中普遍存在低渗透条带,建立机理模型,通过对低渗透条带的渗透率、厚度、产状及与储层渗透率的组合关系进行敏感性分析,研究结果表明,渗流阻挡作用的强弱主要与其渗透率大小有关,当渗透率小于0.01 mD时,能够起到较好的渗流阻挡作用;同等条件下,厚度越大,渗流阻挡作用越强;根据分布形态与样式不同,对剩余油的控制程度Ⅰ类>Ⅱ类>Ⅲ类>Ⅳ类;若有两条交错的低渗透条带,则对剩余油的控制程度Ⅴ类>Ⅵ类。低渗透条带在一定生产时间内可以形成渗流屏障,成为控制剩余油分布的重要因素。

The high water-production stage has started in the YM dolomite reservoir;however,the important issue is how to locate and potentially tap the remaining oil.Low-permeability layers are ubiquitous in this type of reservoir.A mechanism model was built for sensitivity analysis of permeability,thickness,attitude of the low-permeability layers,and reservoir permeability.The results show that the effect of a flow barrier depends mainly on the permeability of the layers.When permeability is lower than0.01mD,the flow barrier functions well.It was found that,all conditions being equal,the thicker the low-permeability layers the stronger would be the flow barrier function.According to the distribution form and style,the controlling degrees of the remaining oil are types I>II>III>IV.If two interlaced low-permeability layers were present,the controlling degrees would be types V>VI.The low-permeability layers are able to form fluid barriers over a short production time,which become the main controlling factors on the distribution of the remaining oil.