Experiments carried out by personnel of the Producing Research Laboratory of The Texas Company in efforts to reduce corrosion in deep gas condensate wells in the Gulf Coast area in which the casing is mudded off from the tubing indicate:
Of two wells with open annuli through which chemicals may be pumped, one well has been treated with sodium carbonate since August 1949 and has shown no measurable corrosion increases in the tubing in two caliper surveys.
Wells in the field produce about 1.5 barrels of water per MMCF of gas at their allowable rates of 4.5 MMCF daily. The water contains dissolved carbon dioxide and organic acids. Water collected at the surface has a pH of about 5.5 and contains about 130 PPM of dissolved iron. Lower flow rates produce water with higher pH and greater dissolved iron content.
Treatment of the well with 30 gal. per day of solution containing 2.5 lb. sal soda or sodium decahydrate per MMCF of produced gas costs approximately 15-20c per MMCF.
Kontol sticks dropped for one year in wells with closed annuli produced no measurable benefit.
Alkaline solution pumped intermittently into this well at the rate of 0.5 gal. per min. with sal soda dissolved in 10-20-gal. water had following results :
At 4 MMCF a day iron content of water dropped rapidly to nearly zero, but rose in two hours to near original value.
At 2 MMCF a day iron content dropped rapidly and is maintained at a very low rate for nearly 8 hours, then in about 4 hours content climbs to original value.
Data indicate alkali not being used up by reaction but is flushed from tubing walls by produced water.
Solution can be injected continuously into wells at any depth by another string of pipe.