成膜防塌液的室内研究及其应用工艺——用于解决气—液钻井转换初期的井壁失稳问题

气体钻井结束后,在替入钻井液初期,钻井液中的水相会大量快速地进入地层,引起地层中的黏土矿物吸水膨胀而导致井壁失稳或形成厚滤饼,造成起下钻遇阻复杂,解决井眼通畅问题需要花费更多的处理时间。为此,提出了气体介质转换成钻井液介质的钻井初期有效控制井壁失稳新的技术思路——成膜防塌技术。在实验室内研制了一种由高分子有机物和无机物组成的混合液体,称之为"成膜液",并进行了人造岩心浸泡、泥球浸泡、防清水渗透的室内实验,分别对比考察了岩样的分散、岩心表面成膜及其防水膜的渗水性能。实验结果表明:该成膜液能在短时间(10~30s)内在实验岩心上形成一层光滑致密的防水渗膜,能有效阻止钻井液中的水相进入实验岩心的内部,起到了防止黏土水化分散、稳定井壁和有效防止厚泥饼形成的作用。最后分别推荐了气体钻井和雾化钻井的成膜液现场应用浓度范围及其操作性强的防渗膜"涂抹"工艺方法。

An experimental study of a diaphragm anti-sloughing drilling fluid and its application process:A solution to wellbore instability in early-stage gas-liquid displacement

After the gas drilling is completed, free water in drilling fluid will flow into the formation rapidly in a large volume after the drilling fluid is pumped downhole. This will cause clay materials to swell, which leads to wellbore instability or the formation of thick mud cakes. Consequently, this will result in complex slacking-off, which takes more time to make borehole unobstructed. Therefore, a diaphragm anti-sloughing drilling fluid technology was proposed as a new methodology to effectively control wellbore instability when the drilling fluid is pumped downhole after the gas drilling. A fluid mixture, a so-called film-forming agent, composed of macromolecular organics and inorganics, was developed and such indoor experiments were conducted as artificial core soaking, mud ball soaking and anti water permeability test to investigate and analyze the dispersion of core samples and the permeability of core surface diaphragm and waterproof diaphragm. The experimental results showed that this film forming agent could quickly form a smooth and strong waterproof film on the surface of laboratory cores within 10 to 30 seconds to effectively prevent free water in the drilling fluid from flowing into the core internal, thus to prevent clay dispersion, borehole instability,and the formation of thick mud cakes. Finally, the field application concentration range of this film-forming agent and the "smearing" technique of waterproof diaphragm were also recommended respectively for gas drilling and mist drilling.