Zhu Wenxi, Luo Yuhan, Li Haidong, Gong Yufei
School of Civil Engineering and Architecture, Henan University, Kaifeng, Henan 475004, People's Republic of China.
Key Laboratory of Shallow Geothermal Energy, Ministry of Natural Resources of the People's Republic of China, Beijing 100195, People's Republic of China.
ACS Omega. 2025 Mar 25;10(13):13011-13026. doi: 10.1021/acsomega.4c09819. eCollection 2025 Apr 8.
In geothermal drilling, the significant rheological deterioration of biopolymer drilling fluids can lead to decreased cutting-carrying efficiency and fluctuations in annulus pressure, which can easily result in unpredictable downhole accidents. To address the challenges, this study innovatively introduces temperature-sensitive monomers (NIPAM) and nanosilica into molecular chains based on temperature response effects and adsorption stability to counteract the negative effects of temperature and salt ions, aiming to develop a rheological agent (PNA-SiO) that is resistant to high temperature and salt. The molecular structure and thermal stability of PNA-SiO were characterized by FT-IR and TGA, and it was demonstrated to have the stability of the molecular main chain within 317 °C. According to rheological and filtration studies, PNA-SiO effectively addresses the issues of high-temperature viscosity attenuation and a sharp rise in the filtration volume of bentonite mud by aggressively adsorbing, creating a stable thixotropic network, and enhancing molecular repulsion. After aging at 60-180 °C, the drilling fluid with 2-4% PNA-SiO has excellent rheology (AV ≥ 57.5 mPa·s, PV ≥ 42 mPa·s, Gel ≥ 1.533 Pa) and filtration (FL ≤ 9.6 mL) properties that fully satisfy API requirements. The H-B model is the preferred model to accurately describe the rheology behavior of PNA-SiO drilling fluids. Moreover, under the comprehensive influence of Na on the interlayer spacing of bentonite and the thickness of the diffusion bilayer, PNA-SiO has applicability in high-temperature saturated saline water. After aging at 150 °C and 5-36% NaCl, the PNA-SiO drilling fluid exhibits stable viscosity (AV ≥ 55 mPa·s, PV ≥ 44 mPa·s) and low filtration volume (≤9.6 mL). In conclusion, PNA-SiO is used as a rheological and fluid loss agent, offering a cost-effective solution to the technical issues of severe leakage and inadequate cutting-carrying capacity encountered by geothermal drilling, which enables the safe and quick exploration of geothermal resources.
在地热钻井中，生物聚合物钻井液显著的流变性能恶化会导致岩屑携带效率降低和环空压力波动，极易引发不可预测的井下事故。为应对这些挑战，本研究基于温度响应效应和吸附稳定性，创新性地将温敏单体（NIPAM）和纳米二氧化硅引入分子链中，以抵消温度和盐离子的负面影响，旨在开发一种耐高温和耐盐的流变剂（PNA-SiO）。通过傅里叶变换红外光谱（FT-IR）和热重分析（TGA）对PNA-SiO的分子结构和热稳定性进行了表征，结果表明其分子主链在317℃以内具有稳定性。根据流变学和过滤性能研究，PNA-SiO通过强烈吸附、形成稳定的触变网络和增强分子排斥力，有效解决了膨润土泥浆高温粘度衰减和滤失量急剧增加的问题。在60-180℃老化后，含有2-4%PNA-SiO的钻井液具有优异的流变性能（动切力≥57.5 mPa·s，塑性粘度≥42 mPa·s，静切力≥1.533 Pa）和过滤性能（滤失量≤9.6 mL），完全满足美国石油学会（API）的要求。H-B模型是准确描述PNA-SiO钻井液流变行为的首选模型。此外，在Na对膨润土夹层间距和扩散双电层厚度的综合影响下，PNA-SiO在高温饱和盐水中具有适用性。在150℃和5-36%NaCl条件下老化后，PNA-SiO钻井液表现出稳定的粘度（动切力≥55 mPa·s，塑性粘度≥44 mPa·s）和低滤失量（≤9.6 mL）。综上所述，PNA-SiO作为一种流变和降滤失剂，为地热钻井中遇到的严重漏失和岩屑携带能力不足等技术问题提供了一种经济有效的解决方案，能够实现地热资源的安全快速勘探。
