Abstract
<title>Abstract</title> <p>Synthetic-based drilling fluids (SBFs) formulated as olefin-based inverse emulsions are widely used in deepwater operations, where static intervals during BOP tests, equipment failures, and maintenance can expose the fluid to high temperatures without shear, accelerating interfacial degradation and structural changes. The role of aging time as a governing factor remains underexplored, since previous studies have mainly emphasized temperature effects and conventional aging durations of up to 16 h. This study investigates the coupled effects of aging temperature (100–150°C) and prolonged static exposure (24–168 h) on the rheological behavior, emulsion stability, and filtration performance of an olefin-based synthetic drilling fluid stabilized by low-HLB amide/amidoamine-type emulsifiers, using a Central Composite Design. Results reveal nonlinear temperature–time domains in which physicochemical rearrangements progressively transition into irreversible degradation, evidenced by changes in yield stress, increases in consistency index and apparent viscosity, and reduction in flow behavior index. These responses indicate enhanced pseudoplasticity and structural reorganization of the multicomponent fluid. Thermal aging promoted interfacial destabilization, brine manifestation, and droplet coalescence, consistent with partial emulsifier degradation indicated by thermogravimetric analysis. Filtration showed a nonlinear response, with reduced filtrate volume at higher temperatures attributed to physical transformation of the filtration control additive and formation of a denser filter cake. These findings demonstrate that aging time is a critical and previously overlooked factor governing performance loss in olefin-based synthetic drilling fluids, with direct implications for fluid integrity management during prolonged static intervals in deepwater operations.</p>