Lost circulation in fractured formations remains a persistent challenge in drilling operations, causing substantial economic losses and increased operational risk. Conventional granular bridging packs are mechanically fragile and can be destabilized by pressure fluctuations, limiting one-trip plugging efficiency. This study incorporates a thermosensitive adhesive resin into bridging assemblies to enhance plug integrity by promoting interparticle adhesion and particle-wall coupling after thermal activation. Oscillatory temperature-sweep rheometry is used to quantify the temperature-dependent viscoelastic response of resin-particle composites. A wedge-shaped fracture analogue with photoelastic visualization is used to monitor force chain development and uniformity during progressive loading. Discrete element method simulations in Particle Flow Code, using a linear parallel-bond contact model, resolve mesoscale load-transfer pathways and isolate the contribution of adhesive interactions. Results indicate that thermosensitive adhesive resin increases assembly coherence, promotes a stable load-bearing skeleton, and suppresses stress localization that typically precedes plugging failure. The strengthening trend is governed by particle rigidity and surface characteristics, yielding consistent load-transfer patterns across experiments and simulations. These findings demonstrate that thermally activated adhesion can transform unconsolidated granular packs into mechanically stable plugging zones, providing a mechanistic basis for designing high-stability lost circulation control systems in fractured formations.

Wellbore instability is the main challenge encountered during borehole construction, particularly when employing water-based drilling fluid (WBDF) under complex geological conditions. A novel wellbore strengthening material of acrylic resin enhanced by hydrophobically modified calcium carbonate particles (ARH) is synthesized by emulsion polymerization. Transmission electron microscope and particle size analysis reveal that ARH exhibits a spherical structure with a Z-average diameter of 277.6 nm. The lap shear strength test shows ARH effectively adheres to two rock slices with a stress of 0.4838 MPa. Uniaxial compressive strength experiments of simulated rock cores verify that ARH can greatly enhance the compressive strength of the simulated core column to 7.1567 MPa. The incorporation of ARH significantly enhances the compressive strength of shale cores, with increases of 18.0620 and 18.9147 MPa compared to those immersed in water and base fluid, respectively. Further microporous membrane plugging experiments show that the filtration losses of 2% ARH in 4% base fluid through 0.1, 0.2, and 0.45 μm microporous membranes are 13.5, 13.2, and 27 mL, respectively, demonstrating excellent plugging capabilities for enhancing wellbore stability. This work generates important theoretical foundations and practical recommendations for wellbore strengthening applications utilizing ARH in complex drilling environments.

Ionic liquids (ILs), recognized for their negligible vapor pressure, thermal stability, and structural tailorability, offer targeted inhibition of clay expansion. Compared to ILs, polyionic liquids (PILs) possess stronger mechanical properties and adsorption capabilities, showing even greater potential in inhibiting clay swelling. In this work, we synthesized and characterized an imidazole-based ionic liquid (IL-NH₂), a polyionic liquid (PIL-ABHIm), and a PIL/IL combination. Their inhibitory performance was rigorously evaluated under simulated drilling conditions through immersion tests, linear swelling tests, among others. Additionally, the mechanisms underlying their interaction with clay minerals were elucidated through contact angle measurements, Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), Zeta potential analysis, and molecular electrostatic potential (MEP) analysis. This work demonstrates that IL-NH₂ inhibits osmotic hydration by altering the interlayer structure of the clay, while PIL-ABHIm reduces surface hydration by forming a hydrophobic barrier on the clay surface. PIL/IL combines both mechanisms, significantly enhancing the stability of clay through the dual mechanisms of cation exchange and hydrophobic barriers. These findings reveal an innovative mechanism by which PIL/IL combination inhibits clay hydration and swelling, providing a scientific foundation for their application in drilling fluids.

Oil-based drilling fluids possess excellent properties such as shale inhibition, cuttings suspension, and superior lubrication, making them essential in the development of unconventional oil and gas reservoirs. However, wellbore instability, caused by the invasion of drilling fluids into shale formations, remains a significant challenge for the safe and efficient extraction of shale oil and gas. This work reports the preparation of mesoporous SiO₂ nanoparticles with low surface energy, utilized as multifunctional agents to enhance the performance of oil-based drilling fluids aimed at improving wellbore stability. The results indicate that the coating prepared from these nanoparticles exhibit excellent hydrophobicity and antifouling properties, increasing the water contact angle from 32° to 146° and oil contact angle from 24° to 134.8°. Additionally, these nanoparticles exhibit exceptional chemical stability and thermal resistance. Incorporating these nanoparticles into oil-based drilling fluids reduced the surface energy of the mud cake from 34.99 to 8.17 mJ·m⁻² and increased the roughness of shale from 0.26 to 2.39 μm. These modifications rendered the mud cake and shale surfaces amphiphobic, effectively mitigating capillary infiltration and delaying the long-term strength degradation of shale in oil-based drilling fluids. After 28 days of immersion in oil-based drilling fluid, shale cores treated with MF-SiO₂ exhibited a 30.5% increase in compressive strength compared to untreated cores. Additionally, these nanoparticles demonstrated the ability to penetrate and seal rock pores, reducing the API filtration volume of the drilling fluid from 11.2 to 7.6 mL. This study introduces a novel approach to enhance the development of shale gas and oil resources, offering a promising strategy for wellbore stabilization in oil-based drilling fluid systems.