Alkaline earth metal scales, especially barium sulfate scale deposits are removed from oilfield pipe and other tubular goods with a scale-removing composition comprising an aqueous alkaline solution having a pH of about 8 to about 14, a polyaminopolycarboxylic acid, preferably EDTA or DTPA and a catalyst or synergist comprising oxalate anion. When the scale-removing solution is contacted with a surface containing a scale deposit, substantially more scale is dissolved at a faster rate than previously possible.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation part of prior co-pending application Ser. No.07/332,147, filed Apr. 3, 1989, of J. M. Paul and R. L. Morris.
The present invention relates to a method of removing alkaline earth sulfate scale from the interior surface of downhole production tubing comprising contacting the scale with a solvent having a specific gravity of at least 1.2 while simultaneously milling the scale with a rotating mill head connected to a downhole motor.
The present invention relates to the use of low frequency sonic energy within the range of 1.25 to 6.5 KHz, preferably less than 2.0 KHz and most preferably 1.25 KHz, for enhancing the dissolution of alkaline earth metal scales from well bores using a scale-removing solvent comprising an aqueous alkaline solution having a pH of about 8 to about 14 and containing EDTA or DTPA and a catalyst or synergist, preferably an oxalate anion. When the scale deposit is contacted with the scale removing solvent while simultaneously transmitting low frequency sonic energy through the solvent, substantially more scale is dissolved at a faster rate than previously possible.
Natural gas processing equipment and sorption media such as charcoal, silica or alumina, contaminated with adherent scale deposits of alkaline earth metal sulfates may include radioactive components, especially radium sulfate and thorium sulfate, which render the equipment radioactive. The scale is removed from the processing equipment by washing with an aqueous chemical composition including a polyaminopolycarboxylic acid such as EDTA or DEPA as a chelant in combination with a synergist, preferably oxalate or monocarboxylate acid anion such as salicylate. The washing may be carried out with the equipment in place or by immersion of the equipment in a body of the solution in a suitable treatment tank.
5183112 - Method for scale removal in a wellbore - Owned by Mobil Oil Corporation (Fairfax, VA) [*] Notice:The portion of the term of this patent subsequent to December 25, 2007 has been disclaimed.
Alkaline earth metal scales, especially barium sulfate scale is removed from a well (the wellbore and the adjacent formation) by contacting the scale with a scale-removing solvent and thereafter sparging the solvent with air or insert gas to dissolve the scale. The sparging aids in achieving a flushing action by the solvent relative to the scale thereby enabling the solvent to more effectively dissolve the scale in the well. Temperature and caustic compatible surfactuants (anionic and non-ionic) may be used in the solvent to generate a column of foam which increases the extent of cleaning oil from the scale surfaces, enabling the solvent to more effectively remove the scale.
This invention discloses a system and method for the disposal of solid waste that contains radioactive material. Radioactive solid wastes generated as scales during oil and gas production operations are collected and placed in a central processing chamber. High-temperature and high-pressure water containing large amounts of dissolve salts is produced from a geothermal subterranean formation and introduced into the solid processing chamber to dissolve the radioactive solid waste. The solid radioactive waste is subjected to a grinding process to microemulsion particle size and treated in an acid.
