提高可循环泡沫钻井液保护油气层效果研究

通过对可循环泡沫钻井液进行微观分析，并考察其对油藏岩石润湿性的影响，探讨了可循环泡沫钻井液保护油气层的机理。为进一步提高可循环泡沫钻井液的油层保护效果，优选出两种配伍性较好的油层保护添加剂：特定浊点的聚合醇和一定级配的暂堵剂。实验结果表明．泡沫钻井液中加入适量暂堵剂和聚合醇后，渗透率恢复值从66．54％增加到84．30％，油气层保护效果显著提高，而且它们对体系的稳定性和流变性没有不良影响。聚合醇与暂堵剂协同作用，既能保持泡沫钻井液体系独特的性能，又能充分发挥各自的保护油气层作用，实现了3者的有机统一，有效提高了该特殊钻井液体系的油气层保护效果。

Study on reservoir protection improvement of circular foam drilling fluid

To further improve the reservoir protection efficiency of circular foam drilling fluid, two types of mud additives with good compatibility are optimized, i. e. , polyglycol of certain cloud point and temporary plugging agent of certain granularity. Test results show that by adding suitable amount of polyglycol and temporary plugging agent in the foam drilling fluid, the permeability recovery increases from 66. 54% to 84. 30%, with remarkable formation protection results achieved while little influence on the rheology and stability is discovered. The working mechanism of circular foam drilling fluid on reservoir protection is investigated from new aspects, by microanalysis to the foam drilling fluid and determining its influence on reservoir rock wettability. Due to the low density and filtration of the foam drilling fluid, a gas isolation zone thus can be formed, which is good for reservoir protection; The filtrate of the foam drilling fluid can assist in shifting from oil wettability to water affinity, and this is beneficial for reservoir protection and enhancing oil recovery. The combined use of polyglycol and temporary plugging agent with the foam drilling fluid system, realizes the function integrity and effectively improves the reservoir protection efficiency.