Abstract
Fluid invasion into productive zones has been widely recognized as detrimental to well productivity. Filtrate and solids invasion can cause irreversible formation damage and permeability reduction. Drilling fluids are formulated to avoid excessive fluid penetration into productive zones. Non- damaging acid-soluble solids are usually added to drill-in fluids in order to promote pore plugging and minimize fluid penetration. Also specific polymers are used that reduce fluid invasion due to surface chemistry and viscosity effects. The development of less invasive non-damaging fluid formulations requires the knowledge of filtration mechanisms of solids containing polymeric solutions in porous media.
The work was carried out in two ways: solids with different particle size distributions and concentrations were added to a polymeric base formulation and the filtration behavior of the fluids through unconsolidated porous media was evaluated using computer tomography scanning. Along with the solids investigation, different types of polymeric solutions exhibiting different shear and extensional rheological properties were tested using the same procedure and technique. The extent of the invaded zone could then be measured and the performance of the different types of material could be evaluated.
The results from the lab tests will be used to support the development of a filtration model to calculate filtration flow rates and depth of penetration accounting for non-newtonian rheology and type of bridging agent on filtration mechanism.
