Novel polymeric organic gelator as lost circulation material for oil-based drilling fluids

Abstract

With the exploitation of unconventional oil and gas resources towards deep and ultra-deep formations, oil-based drilling fluids (OBDFs) with white oil as a base oil have been increasingly employed in China to achieve safe, efficient, and fast drilling operations. However, due to the lack of effective lost circulation material (LCM), drilling time and drilling fluids are severely delayed and extra consumed, respectively. Herein, we innovatively propose and successfully develop a polymeric organic gelator using an emulsifier-free emulsion polymerization method and find that it achieves remarkable plugging ability in OBDF, superior to commercial LCMs, including asphalt, fine calcium carbonate, elastic graphite, and rubber particles. In detail, SMHDV with a branched C8 pendant group, benzene ring, isopropyl, and acetate groups is homogeneously dispersed in OBDF after hot rolling and capable of blocking permeable porous formations, resulting in a reduction of the cumulative filtration by 68 % at a concentration as low as 1 wt%. When added at a high concentration above 10 wt%, SMHDV turned into an organogel which can block cracks and prevent severe lost circulations together with other bridging materials. Furthermore, SMHDV maintains considerable plugging capacity in a wide temperature range of 80–150 °C, which meets most requirements of oil wells. The superior performance is attributed to the formation of supramolecular network structure in white oil due to the self-assembly behavior, which originated from the appropriate hierarchical polarities. In addition, the material can maintain stable rheological properties after hot rolling, improving the electrical stability of the drilling fluid. It is expected to form a set of scientific and efficient OBDF plugging technology to solve the leakage problems encountered during drilling.