Fluid Design and Field Application of an Oil-Based Drill-in Fluid Using Copolymer and Flaked Calcium Carbonate in Fractured High-Permeability Depleted Formations

This paper describes the laboratory evaluation and field application of an optimized oil-based drill-in fluid system used to drill productive zones in the Colombian Foothills. Reviewing the existing operational parameters, a reformulated low-density oil-based drill-in fluid, with a copolymer for filtration control, and with the introduction of a unique flaked CaCO3 to further enhance bridging, was studied and field tested. After careful evaluation, it was determined that gilsonite and asphalt products, in conjunction with improper bridging of both throats and micro fractures in the productive formations, contributed to formation damage. Final results demonstrate the need for adequate rheological properties for hole cleaning, tight control of the high temperature- high pressure (HT-HP) filtrate, and optimum return permeability for the evaluated conditions, whenever the drill-in fluid is applied.