Heavyweight Brines and Corrosion Inhibitors Commonly Used in Brines Affect Various Types of Packer Elements

ABSTRACT The use of brines in oil and gas wells as a completion fluid, workover fluid and packer fluid is a common practice. Salts commonly used to make these brines are KCl, NaCl, CaCl2, CaBr2 and ZnBr2. Under certain conditions these brines are corrosive, and corrosion inhibitors are usually added to reduce their corrosivity on the tubing, casing and downhole tools used in the well. Brines also come into contact with the elastomers (packer elements) used on the downhole tools. Failure of the packer element either by hardening or softening can significantly reduce the time interval between workover operations. This study encompassed the testing of various types of commonly used packer elements at 250°F (121°C) and 350°F (177°C). These elastomers were tested for 7 and 70 days. The physical properties of packer elements observed throughout the test periods were hardness, tensile strength and elongation. Brines selected for use in these tests were 14.5 lb/gal (1.74 g/cc) and 16.5 lb/gal (1.98 g/cc) which used CaCl2, CaBr2 and ZnBr2 as weighting agents. Corrosion inhibitors tested were (1) a film-forming amine and (2) a low-molecular-weight organic product which contained sulfur. The types of rubber elements used in this study were 80-durometer chlorinated polyethylene (CPE), 70-durometer nitrile and 90-durometer nitrile elastomers.