Mechanism and Performance Evaluation of a Solid-Free One-Step Flushing Fluid for Removing Drilling Fluid Filter Cakes
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摘要: 随着环保法规的日益严格,环保型水基钻井液在海洋钻井中得到广泛应用,其形成的致密滤饼会严重影响固井二界面胶结质量。以BIODRILL水基钻井液滤饼为研究对象,结合XRD、FT-IR、SEM、TG等手段揭示了其成分和结构特征,发现滤饼主要由高分子聚合物、加重材料和黏土矿物构成,滤饼孔隙度低、强度高,常规方法难以清除。基于滤饼形成机理,设计了一种由草酸、NaF、EDTA-Na、鼠李糖脂和TWEEN80组成的无固相一步式冲洗液。该体系通过“酸解–螯合–界面剥离–物理冲刷”的协同机制,实现了滤饼的高效溶解与剥离。实验结果表明,在pH值为5.5下,冲洗液在室温和85℃下均可在15 min内达到80%以上的滤饼去除率;冲洗后岩心胶结强度可恢复至空白岩心的70%以上,满足现场对冲洗液性能的要求。研究结果不仅揭示了钻井液滤饼的清洗难点和形成机制,还为复杂环境下固井二界面滤饼的高效清除与胶结质量的提升提供了新思路和理论依据。Abstract: With the tightening of environmental regulations, eco-friendly water-based drilling fluids have been increasingly adopted in offshore drilling operations. However, the dense filter cakes formed by such fluids can severely impair the bonding quality at the cementing interfacial zone. In this study, the filter cake generated by BIODRILL water-based drilling fluid was investigated. Its composition and structural characteristics were examined using XRD, FT-IR, SEM, and TG analyses, which revealed that the cake is mainly composed of polymeric additives, weighting materials, and clay minerals. The resulting structure exhibits low porosity and high strength, making it resistant to removal by conventional methods. Based on the formation mechanism of the cake, a solid-free one-step flushing fluid was developed, formulated with oxalic acid, NaF, EDTA-Na, rhamnolipids, and TWEEN80. The system operates through a synergistic mechanism of acid dissolution, chelation, interfacial peeling, and physical scouring, enabling efficient disintegration and removal of the filter cake. Experimental results demonstrated that at an optimal pH of 5.5, the flushing fluid achieved over 80% cleaning efficiency within 15 minutes under both ambient and 85℃ conditions, with maximum removal rates exceeding 95%. Furthermore, the bonding strength of flushed sandstone cores recovered to more than 70% of that of clean cores, meeting field performance requirements. These findings not only elucidate the challenges and mechanisms of filter cake removal but also provide new strategies and theoretical support for efficient cleaning of cementing interfacial filter cakes and enhancement of bonding quality in complex drilling environments.
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Key words:
- Drilling fluid /
- Filter cake /
- Cementing interfacial zone /
- Flushing fluid /
- Cleaning mechanism
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表 1 钻井液流变性及厚度
钻井液名称 PV/
mPa·sAV/
mPa·sYP/
Pan K/
Pa·sn孔隙度/
%滤饼厚度/
mmBIODRILL 24 42.5 37 0.43 2.12 9.90 1.0 表 2 冲洗液成分及作用
成分 加量/% 功能用途说明 具体作用 草酸 3.0% 有机酸/反应源 形成酸性环境与NaF反应生成HF溶解SiO2 NaF 1.0% 含氟反应源 与草酸反应缓释HF,溶解滤饼表面硅质颗粒 EDTA-Na 5.0% 螯合剂 螯合金属离子,防止沉淀 NaCl 2.0% 盐调节剂 提高体系离子强度,增强渗透、润湿能力 鼠李糖脂 1.5% 生物表面活性剂 环保可降解,提供润湿渗透能力 TWEEN 80 1.5% 非离子表活剂 无毒、环保,降低表面张力,协同剥离 NaOH 2.0% pH值调节剂 控制体系酸碱性,使得体系不同成分均处于高活性范围区间 -
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