Successful Application of Advanced Enzyme Clean Up System in Perforated Completions to Revive Dead Wells – Case Studies from Romania

The presence of residual mud cake around perforation tunnels is a key factor contributing to production decline and blockage of reservoir fluid flow into the wellbore, even after conventional acid stimulation procedures. This work extends previous work on conventional enzymatic cleanup, highlighting the capabilities of a newly developed recombinant enzyme that has proven efficient in perforated completions, where damage is caused by drilling and perforating processes. Specially developed cellulase enzymes break down cellulose-based biopolymers into simpler sugars, improving fluid flow. This enzyme, combined with bio-acetic acid and bio-surfactant, is injected at perforated points into the formation to target clogging materials such as biopolymers and carbonates. In laboratory trials, enzymatic percolation through porous media was studied using mud cake built on ceramic discs using an HPHT setup, along with reducing sugar assay estimates. Field trials conducted in a Romanian oil field involved using the treatment solution in wells drilled with cellulose-based mud. A 12-hour seepage through the tunnel pores allowed the dissolution of the internal cakes. The tailored enzyme system effectively cleaned the wellbore, offering a sustainable alternative for damage clean-up. The wells were first perforated in 2014, but oil production declined abruptly after achieving the maximum flow potential, eventually becoming completely non-productive. Despite two periodic hydrochloric acid stimulation treatments on both wells, no long-term benefits were achieved. While partial production enhancement was observed, it remained at a rate lower than the wells’ optimum flow potential. Subsequently, a rapid reduction in flow led to well closure within a period of three to twelve months. Post-treatment steady-state flow rates showed a 40% improvement in flow profiles compared to conventional treatments conducted on analogous wells. The results proved substantial clean-up, reviving the wells and maintaining production for over 12 months to date. This novel application of the specialized cellulase enzyme system establishes an effective perforation cleanup method for the dissolution of compressed mud cake in perforated zones. This system could be a primary choice for removing damage in perforation tunnels and internal filter cakes, ultimately improving well injectivity and productivity.