PLA/EC共混制备自降解暂堵剂及性能评价

Preparation and Performance Evaluation of Self-degrading Temporary Plugging Agent Prepared by PLA/EC Blend

以聚乳酸为主剂,将其与乙基纤维素、腰果酚NSF3、纳米碳酸钙进行熔融共混改性,制备了新型自降解暂堵剂。通过扫描电镜分析和热重分析测试,对暂堵剂的结构进行表征,考察了自降解暂堵剂体系的降解性能、配伍性能、砂床封堵性能、储层保护性能等指标。结果表明,当聚乳酸和乙基纤维素的比例为4∶6时,暂堵剂具有较好的降解性能和热稳定性。90℃、pH=9的条件下,5d的降解率小于30%,15d的降解率大于90%,满足水平钻井作业要求。温度达到223℃时,质量损失仅为0.35%。在钻井液中加入质量分数为3%的暂堵剂后,在0.69MPa压力下,30min侵入石英砂床的深度小于5cm,能起到良好的封堵作用。此外,该暂堵剂与钻井液的配伍性良好,具有降滤失作用,且解堵后不同岩心的渗透率恢复值均在85%以上,具有较好的储层保护性能。

A new self-degrading temporary plugging agent was prepared by melting and blending polylactic acid with ethyl cellulose,cashew phenol NSF3 and nano-calcium carbonate.The structure of the temporary plugging agent was characterized by scanning electron microscopy and thermogravimetric analysis.The degradation performance,compatibility performance,sand bed plugging performance and reservoir protection performance of the self-degrading temporary plugging agent system were investigated.The results indicated that when the ratio of polylactic acid to ethyl cellulose was 4:6,the temporary plugging agent had better degradation performance and thermal stability,the degradation rate of 5 days was less than 30%,and the degradation rate of 15d was more than 90% at 90℃ and pH=9,which met the requirements of horizontal drilling operation.When the temperature was 223℃,the mass loss was only 0.35%.After adding a temporary plugging agent with a mass fraction of 3%into the simulated drilling fluid,the depth of intrusion into the quartz sand bed was less than 5cm at 0.69MPa and 30min,which played a better plugging role.In addition,the temporary plugging agent had better compatibility with drilling fluid and had the effect of reducing fluid loss;the recovery value of different core permeability after plugging removal was more than 85%,which had a better reservoir protection performance.