Efficient and formation-friendly removal of hematite filter cake using DTPA-based chelating solution

Filter cake plays a crucial role in controlling fluid loss and stabilizing the wellbore during drilling; however, in open-hole completions, it can hinder reservoir connectivity and impair production performance. This study evaluates a DTPA-based chelating solution as an efficient and formation-friendly alternative for removing hematite-water-based filter cake. The goal is to overcome the limitations of conventional HCl-based treatments, including high corrosion risk and iron precipitation upon contact with carbonate formations. A series of solubility experiments were conducted to examine the effects of DTPA concentration (5–20 wt%), pH (2.5–12), temperature, and soaking time on hematite dissolution. Core flooding experiments with CT scanning were also carried out to simulate fluid-rock interactions and assess removal efficiency, wormhole development, and permeability changes. The optimized formulation was applied to dissolve a laboratory-built filter cake on a ceramic disk. To mimic post-dissolution interactions with carbonate formation, calcite powder was introduced into the iron-rich solution, and inductively coupled plasma (ICP) analysis was performed to track Fe and Ca concentrations. Hematite solubility improved with lower pH and higher temperatures. Optimal conditions were identified at 15 wt% DTPA, pH 2.5, and 20 h of soaking, achieving approximately 90 % filter cake removal. Despite the pH increase during calcite interaction, no iron precipitation occurred. ICP results confirmed that chelated Fe remained stable, minimizing formation plugging risk. Corrosion testing showed that DTPA caused significantly lower metal loss than HCl, even without inhibitors. Core flooding validated efficient removal, wormhole creation, and a twofold increase in permeability with no evidence of deep-zone damage. This study introduces a non-acidic, corrosion-controlled removal approach. Unlike HCl, DTPA effectively prevents post-reaction iron precipitation, offering a safer and more formation-compatible solution for filter cake removal in acid-sensitive reservoirs.