非常规油藏纳米剂驱二次采油潜力实验

Experiment on secondary recovery potential of nano⁃agent flooding in unconventional reservoir

为破解蓄能体积压裂开发后存在的持续补能、降递减和提高采收率等难题,在纳米驱油剂比选基础上,通过多介质渗吸、方式接续、周期驱替等系列实验研究,明确了纳米剂渗吸排油效率变化特征和接续开发提高驱油效率的二次采油开发方式及潜力。渗吸实验表明,纳米剂渗吸的排油效率呈现空窗期、高速期、快速期和低速渗吸排油期4阶段变化特征,有助于从渗吸机理上确定合理闷井时间;接续驱替实验显示,渗吸后驱替仍有较大潜力,质量分数0.02%纳米剂接续驱替阶段的驱油效率接近渗吸阶段驱油效率,二者合计驱油效率达到74.67%,残余油饱和度较水驱降低7.43%;周期驱替能够更好发挥纳米剂渗吸排驱微−纳米孔喉剩余油、提高微观波及体积的作用,驱油效率较连续驱替提高14.1百分点(注入0.478 PV时)。因此,水平井蓄能体积压裂开发后及时转向纳米剂周期驱替是大幅度提高非常规油藏采收率的二次采油重要方向。

In order to deal with challenge of continuously supplying energy,reducing production decline rate and enhancing oil recovery after energy storage volumetric fracturing development,on the basis of nano displacement agent screening,a series of experiments of multi-media imbibition,mode succession and cyclic displacement are carried out to determine the variation characteristics of displacement efficiency by nano-agent imbibition and secondary recovery mode and potential of subsequent development to enhance recovery.Imbibition experiment shows variation characteristics of 4 imbibition displacement stages of nano-agent imbibition efficiency,including empty window stage,ultra-high speed stage,high speed stage and low speed stage,contributing to determining rational soaking time based on imbibition mechanism.Subsequent displacement experiment shows still much potential after imbibition,with displacement efficiency of nano-agent with mass volume fraction of 0.02%close to that of imbibition stage.The total displacement efficiency of imbibition displacement reaches 74.67%,and residual oil saturation is decreased by 7.43%of water flooding.Cyclic displacement can promote nano-agent imbibition to displace remaining oil in micro-nano-pore throats,and increase microscopic swept volume,with displacement efficiency increased by 14.1 percentage points of continuous displacement(injecting 0.478 PV).Therefore,it is an important direction of secondary recovery to convert to nano-agent cyclic displacement after energy storage volume fracturing of horizontal well.