Retention Improvement of Sulfonic Acid-Based Scale Inhibitor on Sandstone Formations at HTHP Conditions and H2S Environment with High Salinity

This work presents a thermally stable sulfonic acid base structure (phosphorous free) SI that provides adequate affinity to sandstone rock for squeeze treatment purposes up to 385°C. The designed inhibitor has high performance in HTHP conditions and is completely compatible with HS (200 g/L salinity), as well as high levels of calcium (20 g/L) and barium (3 g/L). At minimum concentration of 5 mg/L, scanning electron microscopy and energy dispersive x-ray results reveal disrupted sulfide scales and BaSO4 crystal growth and no traces of CaCO3 crystals. The adsorption isotherm analysis on sandstone, indicates pure adsorption for [SI] <100 mg/L and combined precipitation/adsorption behaviour for 100 mg/L< [SI] <1000 mg/L.

Recent environmental legislation has pushed many fields especially the Netherlands and UK continentals to phase out phosphorus based scale inhibitors (SI). However, remaining chemistries have mostly shown low tolerance to high salinity formation water (HS) or poor retention properties on the sandstone reservoir, rendering them unsuitable candidates for squeeze treatment. On the other hand, the high temperatures and pressures (HTHP) gas condensate wells require thermostable and compatible SI with HS that could suppress the full range of forming scales including: barium sulfate, calcium carbonate (BaSO4/CaCO3), mixed zinc, lead and iron sulfide (ZnS/PbS/FeS).