Inhibiting hydrate decomposition due to the friction heat generated by the drilling tools is one of the key factors for drilling hydrate formation. Since the existing method based on chemical inhibition technology can only delay the hydrate decomposition rate, a phase-change microcapsule was introduced in this paper to inhibit, by the intelligent control of the drilling fluid temperature, the decomposition of the formation hydrate, which was microencapsulated by modified n-alkane as the core material, and nano-silica was taken as the shell material. Scanning electron microscope (SEM), size distribution, X-ray diffraction (XRD), and Fourier transform infrared spectrometer (FT-IR) were utilized to characterize the structural properties of microcapsules. Differential scanning calorimetry (DSC) spectra displayed that the latent heat was 136.8 J/g in the case of melting enthalpy and 136.4 J/g in the case of solidification enthalpy, with an encapsulation efficiency of 62.6%. In addition, the prepared microcapsules also showed good thermal conductivity and reliability. By comparison, it was also proved that the microcapsules had good compatibility with drilling fluid, which can effectively control the temperature of drilling fluid for the inhibition of hydrate decomposition.

To address the technical challenge of high polymer gel viscosity reducers losing viscosity at elevated temperatures and difficulty in controlling fluid loss, a polymer-based nano calcium carbonate composite high-temperature tackifier named GW-VIS was prepared using acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinylpyrrolidone (NVP), and nano calcium carbonate as raw materials through water suspension polymerization. This polymer gel can absorb water well at room temperature and has a small solubility. After a long period of high-temperature treatment, most of it can dissolve in water, increasing the viscosity of the suspension. The structure of the samples was characterized by infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, and their performance was evaluated. Rheological tests indicated that the 0.5% water suspension had a consistency coefficient (k = 761) significantly higher than the requirement for clay-free drilling fluids (k > 200). In thermal resistance experiments, the material maintained stable viscosity at 180 °C (reduction rate of 0%), and only decreased by 14.8% at 200 °C. Salt tolerance tests found that the viscosity reduction after hot rolling at 200 °C was only 17.31% when the NaCl concentration reached saturation. Field trials in three wells in the Liaohe oilfield verified that the clay-free drilling fluid supported formation operations successfully. The study shows that the polymer gel has the potential to maintain rheological stability at high temperatures by forming a network structure through polymer chain adsorption and entanglement, with a maximum temperature resistance of up to 200 °C, providing an efficient drilling fluid for deep oil and gas well development. It is feasible to select nano calcium carbonate to participate in the research of high-temperature resistant polymer materials. Meanwhile, the combined effect of monomers with large steric hindrance and inorganic materials can enhance the product’s temperature resistance and resistance to NaCl pollution.

With the depletion of shallow hydrocarbon reservoirs, deep petroleum exploration is emerging as a technical focus in the industry, where elevated formation temperatures impose stringent requirements for drilling fluid thermal stability. Concurrently, extended-reach horizontal well (ERHW) technology is widely adopted in offshore development to enhance single-well productivity, demanding drilling fluids that have superior cuttings transport efficiency and environmentally compliant formulations. Consequently, high-temperature-resistant rheological modifiers capable of enhancing dynamic shear stress (τ) while maintaining eco-compatibility have gained critical importance. Based on the requirements of such drilling, this study analyzed the rheological properties of nanostarch crystals(SNC) and explored their application prospects as flow pattern regulators for high temperature resistant drilling fluids in combination with the advantages of nanomaterials and starch materials. The results showed that nanostarch rheological property regulators are disc-shaped and strip-shaped. Compared with starch particles, the proportion of hydroxyl groups in crystal particles is higher, which is conducive to the adsorption and bridging performance of SNC particles. SNC have extremely strong thixotropy. When the concentration is 3%, the crystal suspension has good thixotropy, and when the concentration is doubled, the thixotropy is greatly enhanced, showing good suspension ability, and the sedimentation stability of the suspension is good, 48 hours without subsidence. It has a very positive impact on the drilling fluid system. Even after thermal aging at 150℃/16h (roller oven), it can improve the dynamic shear force of the drilling fluid system, reduce the filtration loss, and improve the thixotropic properties, that is, improve the suspension capacity of the drilling fluid system. Findings validate SNC effectively optimize shear thinning behavior, fluid loss control and solid sag resistance, demonstrating potential as advanced rheological modifiers for high-pressure/high-temperature (HTHP) drilling environments.