Abstract
Organophosphorous compounds are still widely used as potential scale inhibitors in the upstream oil and gas industry, particularly in squeeze treatments as they have good adsorption properties on rock and are easily detectable. However, most phosphonate-based scale inhibitors have some drawbacks, such as poor biodegradability and various incompatibilities with the production system. The low toxicity of bisphosphonates motivated us to test a series of aliphatic and aromatic hydroxybisphosphonates as new oilfield scale inhibitors for calcium carbonate (calcite) and barium sulfate (barite) scales. Thus, the well-known bone-targeting drugs 3-amino-1-hydroxypropane-1,1-bisphosphonic acid (pamidronic acid, SI-1), 4-amino-1-hydroxybutane-1,1-bisphosphonic acid (alendronic acid, SI-2), 5-amino-1-hydroxypentane-1,1-bisphosphonic acid (SI-3), and hydroxyphenylmethylene-1,1-bisphosphonic acid (fenidronic acid, SI-6) are studied along with novel, specially designed bisphosphonates (1,4-dihydroxybutane-1,1,4,4-tetrayl)tetrakisphosphonic acid (SI-4), (1,6-dihydroxyhexane-1,1,6,6-tetrayl)tetrakisphosphonic acid (SI-5), and ((4- aminophenyl)(hydroxy)methylene)bisphosphonic acid (SI-7) in a dynamic tube-blocking scale rig at 100 °C and 80 bar according to typical North Sea conditions. The scale inhibition performance of the new SIs was compared to that of the commercial 1-hydroxyethylidene bisphosphonic acid (HEDP) and aminotrismethylenephosphonic acid (ATMP). The results indicate that all synthesized hydroxybisphosphonates provide reasonable inhibition performance against calcite scaling and show good thermal stability at 130 °C for 7 days under anaerobic conditions.