Open Access

ARTICLE

Synergistic Emulsifier System Based on Molecular Design for Ultra-Low Oil-to-Water Ratio Oil-Based Drilling Fluids

Junping Wang^1,2, Mingbiao Xu^3,*, Wei Xiao^1,*
1 College of Chemistry & Environmental Engineering, Yangtze University, Jingzhou, China
2 Western Drilling Engineering Company of China National Petroleum Corporation, Urumqi, China
3 School of Petroleum Engineering, Yangtze University, Wuhan, China
* Corresponding Author: Mingbiao Xu. Email: ; Wei Xiao. Email:
(This article belongs to the Special Issue: Advances in Functional Polymer Composites: Synthesis, Characterization and Applications)

Journal of Polymer Materials https://doi.org/10.32604/jpm.2026.077100

Received 02 December 2025; Accepted 06 February 2026; Published online 11 March 2026

Abstract

Formulating oil-based drilling fluids (OBDFs) with an ultra-low oil-to-water ratio (OWR ≤ 60:40) presents a formidable stability challenge due to the maximized interfacial area and intensified stress on the interfacial film under high-temperature, high-density conditions. To address this, we engineered a synergistic stabilization system through molecular and colloidal design. A novel hyperbranched polyamide emulsifier (epoxidized soybean oil polyamide) (ESOP), synthesized from epoxidized soybean oil, exhibits superior thermal stability and interfacial activity due to its hyperbranched architecture. Combined with calcium petroleum sulfonate (CPS) and hydrophobic nanosilica (HNs), it enables a high-performance OBDF with an ultra-low OWR of 60:40. The results show that the optimized formula achieves an excellent demulsification voltage of 1290 V, an ultra-low HTHP fluid loss of 1.5 mL, a yield point of 12.9 Pa, and a superior sag factor (SF) of 0.504, outperforming both base and commercial systems. Mechanistic studies reveal a multiscale stabilization strategy involving a dense composite interfacial film, Pickering stabilization, a 3D network, and a unique thermally triggered self-reinforcement effect. This work not only provides a cost-effective OBDF formulation but, more importantly, establishes a molecular topology engineering paradigm for stabilizing complex industrial fluids under extreme conditions.

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Keywords

Oil-based drilling fluid; low oil-to-water ratio; emulsifier; synergistic effect; molecular topology design

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