Análise da força gel de fluidos de perfuração contendo microesferas ocas de vidro

Abstract

This study investigated the rheological behavior of gel strength in olefin-based synthetic drilling fluids modified with hollow glass microspheres (HGMs). The development of low- density fluids is essential for drilling fragile or depleted formations or those with narrow operational windows, reducing the risk of rock fracturing, undesired circulation losses, and formation damage. Gel strength is a critical rheological property that ensures the static suspension of drilling cuttings and weighting agents during circulation interruption, preventing solids settlement without generating excessive pressure spikes upon pump restart. Using a Central Composite Rotatable Design (CCRD) seventeen samples were formulated by varying the concentrations of lime, hollow glass microspheres (HGS19K46), and organophilic viscosifier. Tests were performed in triplicate at 30°C on a coaxial cylinder rheometer to measure gel strength after 10 seconds (G10s) and 10 minutes (G10min), adopting Petrobras' maximum reference limits of 10 and 15 lbf/100 ft², respectively. Results showed that nine formulations met the G10s criterion and six satisfied both parameters simultaneously (PE4, PE6, PE14, PE15, PE16, and PE17). Variable analysis revealed that approval was primarily conditioned on lower organophilic viscosifier concentrations (10.2 to 12 lb/bbl), whereas the simultaneous increase of additives in sample PE10 resulted in the highest gel value (33. lbf/100 ft² for G10min). It is concluded that the incorporation of hollow glass microspheres enables the formulation of viable low-density fluids, in which strict control of viscosifier dosage ensures fragile, flat gels, preserving wellbore integrity and maintaining hydrostatic pressure within safe operational limits.