An Engineered Formation-Damage-Control Drill-In Fluid Technology for Deep-Fractured Tight-Sandstone Oil Reservoir in Northern Tarim Basin

Summary Conventional drill-in fluid commonly induces formation damage during the drill-in process in deep-fractured tight reservoirs, which results in severe well-production decline. It is mainly attributed to the inadequate understanding of multiscale damage mechanisms, unique engineering, and geological conditions of these reservoirs. To fill this gap, an engineered formation-damage-control (FDC) drill-in-fluid technology is developed for a representative deep-fractured reservoir in China. Petrology, petrophysics, and well-history data are summarized to analyze the reservoir engineering and geological properties and the potential formation-damage factors. Drill-in-fluid-induced damage is experimentally evaluated on both matrix and fracture core samples at 130°C. Additionally, drill-in-fluid invasion depth is quantitatively evaluated using a mathematical model. The multiscale mechanisms of drill-in-fluid-induced formation damage are revealed to design the FDC drill-in-fluid technology. The optimized drill-in fluid is engineered by a specific assembly of acid-soluble-fiber bridging particles, filling particles, and an oil-soluble temporary-plugging agent. The effectiveness of the engineered FDC drill-in fluid is validated by laboratory experiment comprising basic-parameter tests and evaluation of FDC performance. Successful field application of the engineered FDC drill-in fluid in Tarim Basin is also discussed.