| 摘要 |
A method of removing iron-containing casing from a well bore open to the atmosphere, comprising injecting an acidic solution therein, which comes in contact with the casing and accelerates oxidation and dissolution of iron. Gas, e.g. hydrogen, may be produced by the redox reactions and removed by venting, absorption or adsorption. The solution may contain organic or inorganic acids, preferably a strong acid such as hydrochloric, phosphonic and sulphuric acid. It may be left in contact with the casing, which includes pipe, casing, liner and tubing, for 4-48 hours, after which it may be removed from the well, cleaned from iron compounds and reinjected downhole. The process may be applied repeatedly, to destroy one or more selected casing segments, isolated from the rest of the casing by plugs, such as pills of viscous fluids. The casing may be completely dissolved or partially corroded, then milled out of the well. The process, which aims at ensuring effective plugging of the well before its abandonment, is preferably accelerated by forming an electrochemical cell where the casing is the anode, injecting an electrolyte solution into the well bore and applying an electrical current which causes oxidation of iron into iron cations. |
