Effect of fracture distribution on extraction efficiency in low-permeability NAPL-contaminated formations

Abstract

Hydraulic fracturing offers an effective solution to the challenge of remediating low-permeability contaminated formations by improving substance transport rates. In this study, COMSOL Multiphysics, a large-scale multi-physics coupled simulation software, was employed to simulate enhanced extraction and remediation of low permeability non-aqueous phase liquid (NAPL)-contaminated formations using hydraulic fractures. The results obtained indicate that fracturing and enhanced extraction can effectively improve the NAPL removal rate. The NAPL removal rate increased with increasing depth of the extraction well screens, fracture length, and fracture spacing. Through a coupling analysis of multiple factors and working conditions, the extraction well screens are suggested to be buried within the lower one-third of the low-permeability contaminated formation, and the length of a single fracture should be within 50%–80% of the extraction radius. When the distance between the two fractures was greater than 1.75 m, the enhancement effect of the fracture length was further promoted. Consequently, a reasonable configuration of fracture length, quantity, and spacing can effectively broaden the influence radius of extraction wells.