A novel hyper-cross-linked polymer for high-efficient fluid-loss control in oil-based drilling fluids

In order to control filtrate at high-temperature and high-pressure condition in oil-based drilling fluid for drilling process of oil and gas wells, an amine cross-linked polymeric fluid-loss-control material (ACP) was designed and synthesized. This material was synthesized through cross-linking poly (maleic anhydride-alt-1-octadecene) (PMAO) with amine. The structure of hyper-cross-linked copolymer enables the ACP polymers to withstand higher aging temperatures and less affect the rheology of oil-based drilling fluid. The structures of ACP polymers we synthesized were confirmed by FT-IR spectra and elemental analysis. TGA results showed that the decomposition temperature of ACP polymers exceeds 400 °C. And the amphiphilic nature of ACP polymers makes them enhance the stability of water-in-oil emulsion of oil-based drilling fluid. In addition, combining the viscoelasticity data of amine cross-linked PMAO suspensions and the fluid-loss control performance of ACP in oil-based drilling fluid, it was found that the increase of amino number in the cross-linker can effectively reduce the filtrate permeating, which is because the aggregation of hydrophilic amino makes ACP polymer form a dense structure to prevent oil from passing through. After screening of ACP polymers, the preferred one (ACP-5) can reduced filtrate volume of oil-based drilling fluid by over 90% with small dosage (3 g in 400 mL drilling fluid) after hot rolling for 16 h at 232 °C. [Display omitted] •A series of novel amine cross-linked ACP polymers were prepared.•ACP polymers are resistant to high temperature and high pressure condition.•Emulsion stability of oil-based drilling fluid increases with ACP polymers added.•Fluid loss was efficiently reduced with a small dosage of ACP polymers.