Research on the Use of Nano-starch Crystals as Rheological Performance Regulators in Drilling Fluids

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.